Date   

Re: carbon

One Sky Dog
 

Got it fooled me too.

Charlie

In a message dated 12/21/2009 1:53:45 P.M. Mountain Standard Time,
dmperry1012@... writes:

I understood that; Bob didn't understand that Lynn was joking. Read
Lynn's post from earlier today.

Mike

Allan Farr wrote:

Bob wasn't advocating 18k ft without oxygen, he was saying don't do it.

----- Original Message -----


Re: carbon

Jon Finley <jon@...>
 

I see that Bob unsubscribed from the Q-List. I have nothing to do with the
Performance list so cannot tell you whether or not he went over there.

Jon

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf
Of Sam Hoskins
Sent: Monday, December 21, 2009 7:25 AM
To: Q-LIST
Subject: Re: [Q-LIST] Re: carbon

All,

I truly hope that we don't get off on the wrong foot with someone new
to the
Q world, especially someone who has already built seven aircraft. It
sounds
like Bob Cringely can bring a lot to the table. There are newer ways
to
skin the old cats around here, and we need to keep our eyes/ears open
when
the potentially good ideas surface.

Having said that, Bob probably does not have the benefit of having read
thousands of posts on the Q-list, the contributions to the newsletter,
or
the experiences many of us have been through. Having been in aviation
as
long as he has, I'm sure that he also has "seen em' come and seen em'
go".
(Google Bob and you might be surprised what you come up with). Several
times
a year a Quickie newbie may pop up and propose all sorts of unusual
ideas,
that never make it to fruition; the latest, a turbine powered Quickie,
comes
to mind. The Q-group is weary of these Johnny come lately's and
justifiably
wary of them.

Bob also may not know that we have an entirely separate e-mail list,
just
for discussions of non-standard Q related mods. You can join here:
http://groups.yahoo.com/group/Q-Performance/ This was created to try
and
avoid confusion when attempting to build a standard Quickie type plane.
Admittedly, the line sometimes blurs.

We all need to keep in mind that there is a world outside or ours and a
lot
of people can bring things to the table. The trick is separating the
wheat
from the chaff. I think Bob may be good for us.

Personally, I sincerely hope Bob sticks around and I hope he builds his
CF
Quickie. However, that discussion is most appropriate on the
Performance
list.

Good luck and stay friendly.

Sam Hoskins
Murphysboro, IL
www.samhoskins.blogspot.com



On Sun, Dec 20, 2009 at 3:17 PM, Mike Perry <dmperry1012@...>
wrote:



Bob:

Someone is crazy here. I don't think it's Lynn French. Your recent
posts contains some interesting insights mixed with some half truths
and
some gross errors. Let's start with your comments about Burt Rutan.

1) The Q2 is NOT a Rutan design and he objects vigorously to being
associated with it. You seem to mix comments on the Q1 with the Q2
without realizing that.
2) The wing spar takes the main load but what prevents torsion
(twisting)? Some part of the structure has to prevent twisting, what
is
it? I do not know the context of Burt's remarks about the skins not
carrying the loads but I do not think the foam alone is enough to
resist
twisting in any Q wing. BTW, just what is the "spar" in the Q wing?
3) "[Burt's] spars were designed with ultimate loads double the
service
loads as opposed to 1.5X in a metal structure." That is an FAA
standard
for composite structures and a generally accepted criteria in
engineering work with composites. This is based on the failure mode
of
composites and on variability in materials and construction. There
are
whole books written on this, I'm not reproducing them here.
4) "[Burt's] design process was always minimal while his testing was
rigorous." Great. Just who tested the Q-2 wing? Or the Q-1 wing for
that matter? If QAC tested them there is no record I know of.

This seems to be the right point to inject that I tested a Q2 wing.
The
results will be in the next Q-talk. There were several problems with
the test, so I don't think we can say much about the safety of the Q2
wing; however, the wing broke at 7.5 Gs (design limit 12 Gs) with a
failure that appeared torsional. It started just outside of an area
that was repaired and reinforced for testing purposes -- it certainly
seemed like a minor change that would make the overall wing stronger,
but instead the wing broke early. That experience makes me very
skeptical of people who say these wings are over-designed, or who say
the skins aren't important for torsion resistance, or who substitute
materials without engineering and testing.

Returning to your posts, you wrote, "The only real structural change
was
adding carbon spars to the canard and that was in an attempt to keep
bad
pilots from breaking their planes during Pilot-Induced-Oscillation
(PIO)
on landing." Really? I'm glad to hear it wasn't needed to increase
the
gross weight of the airplane or to change to a thinner airfoil that
was
less susceptible to surface contamination, esp. rain.

You also wrote, "So on wings of this type (where the spars carry the
majority of loads) a single layer of cloth on the 45-degree bias
offers
enough strength to carry any torsion loads and keep the insides of
the
wing on the inside." Which cloth? Surely not UNI. Has a single layer
of BID been tested in this application? Based on the wing test I did
I
would strongly disagree with this advice.

You also wrote, "What is the history of structural failures on
Quickies?
Zero." If you mean only the single seat Quickie I am not aware of any
structural failures, but there have been main wing failures in the
Q2.
Two Q-2 wings failed due to non-standard construction (building a
core
from smaller blocks) or a non standard repair (using expanding foam).
This makes me suspicious when people propose "minor" changes or
substitutions because the airplane is "so over-built that you can
make
lots of changes with relative impunity."

You also wrote, "I'm not cutting any foam for my Q. I'm making female
molds for all the parts and will vacuum bag and cure them at 250
degrees
in my home-made oven. I expect to finish the plane by September."
Great. Please stop calling this airplane a Q, Q1 or Quickie. You are
talking about a totally redesigned airplane.

THIS DISCUSSION BELONGS ON Q-PERFORMANCE. You are talking about an
entirely new design. This is not about building testing and flying a
standard Quickie or Q2xx.

I am not an engineer. From what I read neither are you. For your
safety I recommend you get one involved, or do a lot of testing, or
both.

Mike Perry


bob@... <bob%40cringely.com> wrote:


I don't know how to put this politely, but are you CRAZY?

I fly 300+ hours per year entirely in experimental aircraft. Next
year
I will go to California (I live in South Carolina) 18 times -- all
at
16-18K. So I have quite a bit of experience doing just the sort of
flying you describe. In my youth (I am 56) I went as high as 22K
without oxygen -- ONCE. Today I use O2 fulltime at night (no matter
what altitude) and above 8000 during the day. What you propose to
do
is insane.

Bob








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Re: carbon

Sam Hoskins
 

All,

I truly hope that we don't get off on the wrong foot with someone new to the
Q world, especially someone who has already built seven aircraft. It sounds
like Bob Cringely can bring a lot to the table. There are newer ways to
skin the old cats around here, and we need to keep our eyes/ears open when
the potentially good ideas surface.

Having said that, Bob probably does not have the benefit of having read
thousands of posts on the Q-list, the contributions to the newsletter, or
the experiences many of us have been through. Having been in aviation as
long as he has, I'm sure that he also has "seen em' come and seen em' go".
(Google Bob and you might be surprised what you come up with). Several times
a year a Quickie newbie may pop up and propose all sorts of unusual ideas,
that never make it to fruition; the latest, a turbine powered Quickie, comes
to mind. The Q-group is weary of these Johnny come lately's and justifiably
wary of them.

Bob also may not know that we have an entirely separate e-mail list, just
for discussions of non-standard Q related mods. You can join here:
http://groups.yahoo.com/group/Q-Performance/ This was created to try and
avoid confusion when attempting to build a standard Quickie type plane.
Admittedly, the line sometimes blurs.

We all need to keep in mind that there is a world outside or ours and a lot
of people can bring things to the table. The trick is separating the wheat
from the chaff. I think Bob may be good for us.

Personally, I sincerely hope Bob sticks around and I hope he builds his CF
Quickie. However, that discussion is most appropriate on the Performance
list.

Good luck and stay friendly.

Sam Hoskins
Murphysboro, IL
www.samhoskins.blogspot.com



On Sun, Dec 20, 2009 at 3:17 PM, Mike Perry <dmperry1012@...> wrote:



Bob:

Someone is crazy here. I don't think it's Lynn French. Your recent
posts contains some interesting insights mixed with some half truths and
some gross errors. Let's start with your comments about Burt Rutan.

1) The Q2 is NOT a Rutan design and he objects vigorously to being
associated with it. You seem to mix comments on the Q1 with the Q2
without realizing that.
2) The wing spar takes the main load but what prevents torsion
(twisting)? Some part of the structure has to prevent twisting, what is
it? I do not know the context of Burt's remarks about the skins not
carrying the loads but I do not think the foam alone is enough to resist
twisting in any Q wing. BTW, just what is the "spar" in the Q wing?
3) "[Burt's] spars were designed with ultimate loads double the service
loads as opposed to 1.5X in a metal structure." That is an FAA standard
for composite structures and a generally accepted criteria in
engineering work with composites. This is based on the failure mode of
composites and on variability in materials and construction. There are
whole books written on this, I'm not reproducing them here.
4) "[Burt's] design process was always minimal while his testing was
rigorous." Great. Just who tested the Q-2 wing? Or the Q-1 wing for
that matter? If QAC tested them there is no record I know of.

This seems to be the right point to inject that I tested a Q2 wing. The
results will be in the next Q-talk. There were several problems with
the test, so I don't think we can say much about the safety of the Q2
wing; however, the wing broke at 7.5 Gs (design limit 12 Gs) with a
failure that appeared torsional. It started just outside of an area
that was repaired and reinforced for testing purposes -- it certainly
seemed like a minor change that would make the overall wing stronger,
but instead the wing broke early. That experience makes me very
skeptical of people who say these wings are over-designed, or who say
the skins aren't important for torsion resistance, or who substitute
materials without engineering and testing.

Returning to your posts, you wrote, "The only real structural change was
adding carbon spars to the canard and that was in an attempt to keep bad
pilots from breaking their planes during Pilot-Induced-Oscillation (PIO)
on landing." Really? I'm glad to hear it wasn't needed to increase the
gross weight of the airplane or to change to a thinner airfoil that was
less susceptible to surface contamination, esp. rain.

You also wrote, "So on wings of this type (where the spars carry the
majority of loads) a single layer of cloth on the 45-degree bias offers
enough strength to carry any torsion loads and keep the insides of the
wing on the inside." Which cloth? Surely not UNI. Has a single layer
of BID been tested in this application? Based on the wing test I did I
would strongly disagree with this advice.

You also wrote, "What is the history of structural failures on Quickies?
Zero." If you mean only the single seat Quickie I am not aware of any
structural failures, but there have been main wing failures in the Q2.
Two Q-2 wings failed due to non-standard construction (building a core
from smaller blocks) or a non standard repair (using expanding foam).
This makes me suspicious when people propose "minor" changes or
substitutions because the airplane is "so over-built that you can make
lots of changes with relative impunity."

You also wrote, "I'm not cutting any foam for my Q. I'm making female
molds for all the parts and will vacuum bag and cure them at 250 degrees
in my home-made oven. I expect to finish the plane by September."
Great. Please stop calling this airplane a Q, Q1 or Quickie. You are
talking about a totally redesigned airplane.

THIS DISCUSSION BELONGS ON Q-PERFORMANCE. You are talking about an
entirely new design. This is not about building testing and flying a
standard Quickie or Q2xx.

I am not an engineer. From what I read neither are you. For your
safety I recommend you get one involved, or do a lot of testing, or both.

Mike Perry


bob@... <bob%40cringely.com> wrote:


I don't know how to put this politely, but are you CRAZY?

I fly 300+ hours per year entirely in experimental aircraft. Next year
I will go to California (I live in South Carolina) 18 times -- all at
16-18K. So I have quite a bit of experience doing just the sort of
flying you describe. In my youth (I am 56) I went as high as 22K
without oxygen -- ONCE. Today I use O2 fulltime at night (no matter
what altitude) and above 8000 during the day. What you propose to do
is insane.

Bob




[Non-text portions of this message have been removed]


Re: carbon long

One Sky Dog
 

Lynn and anyone else who is interested,

This may or may not be of any use but I teach a portion of a Intro to
Composites class for engineers that have not had exposure to composites. I have
also learned a bit more about composites under load.

We have them do several practical hands on lay-ups both wet and with
pre-impregnated material. One of these projects is a 3" X 3" carbon "I" beam.
The students are given a drawing and a material package and the tooling to
build the beam. In another portion of the class the students use "Genlam" and
matrix math calculations to predict first ply failure and ultimate failure
of their beams. The day prior to the end of the class the students write
the predicted failure loads on the board and we take the students and their
beams over to the Instron machine and do a 4 point bend test to failure.

So you might ask what is the point? Well the point is that in order to meet
calculated load values the basic material has to be made correct.
Engineers are generally terrible tech's and do all kinds of things that are bad
like wrinkling fibers not getting the angles correct leaving paper or plastic
in the layup ect. It also brings out the fact that composites are not
understood as well as metal and the predictive tools are not taking into account
of the process variability of making the basic material. This variability
does not factor in when designing in metal because builders buy the basic
material already made to exacting specifications and tested. To compensate
for the material/builder factor like Bob said design margins are huge if you
build it correct to the design, and adequate most of the time even if the
builder makes some mistakes.

Most composite structures are designed and built with a lot of "build and
test" data that supports the F.E.A. models.

The test values on our student beams has a huge range from really crappy to
amazing. Also the beam design was not optimized and has problems
independent of the students workmanship. My co-instructor and I decided to try and
improve the beam lay-up to overcome non expected failure modes. We first
took the existing material package and started rearranging plies and fiber
orientation and noting the effect on the ultimate value and the failure mode.
The last beam we also looked at the analysis programs and tried to balance
the stress levels between the cap and web.

Going from memory because I am visiting my daughter in WI. I will list the
lay-up and failure loads all beams were made from 0.005 unidirectional pre
impregnated AS-4 grade carbon fiber.

Student beams: The webs are (+/- 45)4 symmetrical about the centerline or
16 plies of +/- 45 material that form 2 back to back C sections. The caps
consist of the 8 plies of 45's that form each side of the web and 19 plies
of zero degrees along the length of the beam.

The modified beam: (90,90)(+/-45)4) symmetrical about the centerline. This
is 20 plies with 2, 90 degree plies on the outside with 16 45 plies in the
middle of the web. The upper and lower cap plies on top of the web plies
was: 0,0,0,90,0,0,90,0,0,90,0,0. So we added 4 plies to the web and took out
7 plies from each cap and reoriented 3 cap plies from zero degrees to 90
degrees.

The student beams broke at 6500 lbs and 7800 lbs. The instructor beam with
less material failed at 9700 lbs. Because of non optimized design and
workmanship the student beams there was never a failure in the caps. Basically
the caps were so over designed that they drove all of the stress into the
webs and the beam would fail in the web or split the cap and collapse. By
balancing out the design we were able to drive the failure to a compression
buckle in the top cap at the load point and carry approximately 125% higher
load than the base design.

Lynn I hope this was of some help, a little 3" X 3" X 36" test I beam is
good for loads of 5,000 to 10,000 lbs. The filament wound spar most likely
does not contain zero plies but uses the cosign of the winding angle. I
think it would be pretty easy to adapt the Dragonfly spar design to the Q
canard if you were a good designer and did some testing to support the
calculations. I am with Bob on the position that most outside skins are designed to
withstand handling loads vs. actual aero loads. If you have a beam design
and could build a 36" long section I might be able to break it for you. I
often break other beam designs like a 3" sandwich structure to contrast
against the "I" beam design. E-mail me offline if you want.

The value of this info is equal to the price.

Regards,

One Sky Dog

In a message dated 12/20/2009 6:02:08 A.M. Mountain Standard Time,
LJFrench@... writes:

OK, I think I understand that you say the carbon spar should be able to
carry most of the loads with minimal glass. Would this be for just the
canard, and what are the minimum number of plies you think I can get by
with
on the main wing?

Thanks again,
LJ French


Re: carbon

L.J. French <LJFrench@...>
 

Mike,
Thanks for calling this in and doing the right thing regarding the
statements made in this thread over the past few days.
My approach at having fun with this was wrong. Most people on this list know
me and know how off the wall my comments were. However, not everyone may
have recognized this and could potentially jeopardize their safety if they
thought some of the comments made in the last few days were legitimate.

For those who don't know different, DO NOT even think about listening to
this type of internet hype when it comes to recommendations about building
or flying these airplanes. Seek out the many experienced people on this list
and get to know them and their airplanes on a personal level. Then decide
what / how to make changes and how best to fly these airplanes. Building to
plans is always the best approach - especially without some engineering
help.


Regards,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Mike Perry
Sent: Sunday, December 20, 2009 3:17 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

Bob:

Someone is crazy here. I don't think it's Lynn French. Your recent posts
contains some interesting insights mixed with some half truths and some
gross errors. Let's start with your comments about Burt Rutan.

1) The Q2 is NOT a Rutan design and he objects vigorously to being
associated with it. You seem to mix comments on the Q1 with the Q2 without
realizing that.
2) The wing spar takes the main load but what prevents torsion (twisting)?
Some part of the structure has to prevent twisting, what is it? I do not
know the context of Burt's remarks about the skins not carrying the loads
but I do not think the foam alone is enough to resist twisting in any Q
wing. BTW, just what is the "spar" in the Q wing?
3) "[Burt's] spars were designed with ultimate loads double the service
loads as opposed to 1.5X in a metal structure." That is an FAA standard for
composite structures and a generally accepted criteria in engineering work
with composites. This is based on the failure mode of composites and on
variability in materials and construction. There are whole books written on
this, I'm not reproducing them here.
4) "[Burt's] design process was always minimal while his testing was
rigorous." Great. Just who tested the Q-2 wing? Or the Q-1 wing for that
matter? If QAC tested them there is no record I know of.

This seems to be the right point to inject that I tested a Q2 wing. The
results will be in the next Q-talk. There were several problems with the
test, so I don't think we can say much about the safety of the Q2 wing;
however, the wing broke at 7.5 Gs (design limit 12 Gs) with a failure that
appeared torsional. It started just outside of an area that was repaired
and reinforced for testing purposes -- it certainly seemed like a minor
change that would make the overall wing stronger, but instead the wing broke
early. That experience makes me very skeptical of people who say these
wings are over-designed, or who say the skins aren't important for torsion
resistance, or who substitute materials without engineering and testing.

Returning to your posts, you wrote, "The only real structural change was
adding carbon spars to the canard and that was in an attempt to keep bad
pilots from breaking their planes during Pilot-Induced-Oscillation (PIO) on
landing." Really? I'm glad to hear it wasn't needed to increase the gross
weight of the airplane or to change to a thinner airfoil that was less
susceptible to surface contamination, esp. rain.

You also wrote, "So on wings of this type (where the spars carry the
majority of loads) a single layer of cloth on the 45-degree bias offers
enough strength to carry any torsion loads and keep the insides of the wing
on the inside." Which cloth? Surely not UNI. Has a single layer of BID
been tested in this application? Based on the wing test I did I would
strongly disagree with this advice.

You also wrote, "What is the history of structural failures on Quickies?
Zero." If you mean only the single seat Quickie I am not aware of any
structural failures, but there have been main wing failures in the Q2.
Two Q-2 wings failed due to non-standard construction (building a core from
smaller blocks) or a non standard repair (using expanding foam).
This makes me suspicious when people propose "minor" changes or
substitutions because the airplane is "so over-built that you can make lots
of changes with relative impunity."

You also wrote, "I'm not cutting any foam for my Q. I'm making female molds
for all the parts and will vacuum bag and cure them at 250 degrees in my
home-made oven. I expect to finish the plane by September."
Great. Please stop calling this airplane a Q, Q1 or Quickie. You are
talking about a totally redesigned airplane.

THIS DISCUSSION BELONGS ON Q-PERFORMANCE. You are talking about an entirely
new design. This is not about building testing and flying a standard
Quickie or Q2xx.

I am not an engineer. From what I read neither are you. For your safety I
recommend you get one involved, or do a lot of testing, or both.

Mike Perry

bob@... wrote:


I don't know how to put this politely, but are you CRAZY?

I fly 300+ hours per year entirely in experimental aircraft. Next year
I will go to California (I live in South Carolina) 18 times -- all at
16-18K. So I have quite a bit of experience doing just the sort of
flying you describe. In my youth (I am 56) I went as high as 22K
without oxygen -- ONCE. Today I use O2 fulltime at night (no matter
what altitude) and above 8000 during the day. What you propose to do
is insane.

Bob


Re: carbon perry and hoskins

JMasal@...
 

OOOOoooops, in my post I was referring to canard tests and not to the main
wing. I think I had a neuron misfire.

Jim


Re: carbon- Hoskins and Perry

JMasal@...
 

Hoskins and Perry make consummate good sense in their emails.

Newbie that I am not, I am reminded of a fatal accident of a T-18 at
Oshkosh in the late 70's. Wing failure. For some reason it turned out that the
builder substituted a slightly smaller rivet in his wings build.
His plane flew it for 10+ years before the fatal failure which killed him
and a 13 year old girl rider.

My conclusion is that flying a modified airplane for many years without a
failure is a foolhardy test of adequate engineering. But one is free to risk
HIS OWN life only. A correctly conceived engineering static test to an
appropriate load is the way to go, IMO.

Since the 70's, a number of Q wings have been tested successfully. I've
seen 2 failures on video but the test jigs were wrong. Consulting an
"experienced" aero engineer is a wise thing to do.

Modifications: if it ain't broke, don't fix it and don't lead other
builders down your garden path... do it quietly and without showing off your ego
until you sucessfully prove it out. And don't disregard the past.

Jim


Re: carbon

Mike Perry
 

Bob:

Someone is crazy here. I don't think it's Lynn French. Your recent posts contains some interesting insights mixed with some half truths and some gross errors. Let's start with your comments about Burt Rutan.

1) The Q2 is NOT a Rutan design and he objects vigorously to being associated with it. You seem to mix comments on the Q1 with the Q2 without realizing that.
2) The wing spar takes the main load but what prevents torsion (twisting)? Some part of the structure has to prevent twisting, what is it? I do not know the context of Burt's remarks about the skins not carrying the loads but I do not think the foam alone is enough to resist twisting in any Q wing. BTW, just what is the "spar" in the Q wing? 3) "[Burt's] spars were designed with ultimate loads double the service loads as opposed to 1.5X in a metal structure." That is an FAA standard for composite structures and a generally accepted criteria in engineering work with composites. This is based on the failure mode of composites and on variability in materials and construction. There are whole books written on this, I'm not reproducing them here.
4) "[Burt's] design process was always minimal while his testing was rigorous." Great. Just who tested the Q-2 wing? Or the Q-1 wing for that matter? If QAC tested them there is no record I know of.

This seems to be the right point to inject that I tested a Q2 wing. The results will be in the next Q-talk. There were several problems with the test, so I don't think we can say much about the safety of the Q2 wing; however, the wing broke at 7.5 Gs (design limit 12 Gs) with a failure that appeared torsional. It started just outside of an area that was repaired and reinforced for testing purposes -- it certainly seemed like a minor change that would make the overall wing stronger, but instead the wing broke early. That experience makes me very skeptical of people who say these wings are over-designed, or who say the skins aren't important for torsion resistance, or who substitute materials without engineering and testing.

Returning to your posts, you wrote, "The only real structural change was adding carbon spars to the canard and that was in an attempt to keep bad pilots from breaking their planes during Pilot-Induced-Oscillation (PIO) on landing." Really? I'm glad to hear it wasn't needed to increase the gross weight of the airplane or to change to a thinner airfoil that was less susceptible to surface contamination, esp. rain.

You also wrote, "So on wings of this type (where the spars carry the majority of loads) a single layer of cloth on the 45-degree bias offers enough strength to carry any torsion loads and keep the insides of the wing on the inside." Which cloth? Surely not UNI. Has a single layer of BID been tested in this application? Based on the wing test I did I would strongly disagree with this advice.

You also wrote, "What is the history of structural failures on Quickies? Zero." If you mean only the single seat Quickie I am not aware of any structural failures, but there have been main wing failures in the Q2. Two Q-2 wings failed due to non-standard construction (building a core from smaller blocks) or a non standard repair (using expanding foam). This makes me suspicious when people propose "minor" changes or substitutions because the airplane is "so over-built that you can make lots of changes with relative impunity."

You also wrote, "I'm not cutting any foam for my Q. I'm making female molds for all the parts and will vacuum bag and cure them at 250 degrees in my home-made oven. I expect to finish the plane by September." Great. Please stop calling this airplane a Q, Q1 or Quickie. You are talking about a totally redesigned airplane.

THIS DISCUSSION BELONGS ON Q-PERFORMANCE. You are talking about an entirely new design. This is not about building testing and flying a standard Quickie or Q2xx.

I am not an engineer. From what I read neither are you. For your safety I recommend you get one involved, or do a lot of testing, or both.
Mike Perry

bob@... wrote:


I don't know how to put this politely, but are you CRAZY?

I fly 300+ hours per year entirely in experimental aircraft. Next year I will go to California (I live in South Carolina) 18 times -- all at 16-18K. So I have quite a bit of experience doing just the sort of flying you describe. In my youth (I am 56) I went as high as 22K without oxygen -- ONCE. Today I use O2 fulltime at night (no matter what altitude) and above 8000 during the day. What you propose to do is insane.

Bob



Re: carbon

Robert Cringely
 

I don't know how to put this politely, but are you CRAZY?

I fly 300+ hours per year entirely in experimental aircraft. Next year I will go to California (I live in South Carolina) 18 times -- all at 16-18K. So I have quite a bit of experience doing just the sort of flying you describe. In my youth (I am 56) I went as high as 22K without oxygen -- ONCE. Today I use O2 fulltime at night (no matter what altitude) and above 8000 during the day. What you propose to do is insane.

Bob

-----Original Message-----
From: L.J. French [mailto:LJFrench@...]
Sent: Sunday, December 20, 2009 09:13 AM
To: Q-LIST@...
Subject: RE: [Q-LIST] Re: carbon

OK, great. I will make the main wing the same as the canard and try to avoid
too much Bondo. I would really like to make this thing come in under 600 lbs
since weight is the most important criteria for my design. I would also like
to fly up in that 18,000 ft range but want to be able to go faster than 204
KTS. So to do that I want to install a turbo charged O-200 instead of the
VW. That is also part of why I want to save weight on glass. I am in pretty
good health so I think I can fly up there without oxygen. I just don't like
the thought of carrying the extra weight of an oxygen bottle. I am still
thinking that part through. I think for now I will try your idea of starting
with the cowl.
Thanks for the help,

LJ

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
bob@...
Sent: Sunday, December 20, 2009 7:42 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

There is no difference between the to wings in this matter.

How much weight are you hoping to save? Most people use too much resin and
WAY too much Bondo. First improve your construction methods THEN start to
think about changing the ply schedule. But keep your hopes realistic. You'll
find a huge amount of good advice on Mark Landoll's KR-2S web site,
especially his method of laying-up glass (or carbon fiber -- his wings are
CF) first on acetate film then transferring it to the foam with an ideal
glass-to-resin ratio.

If you really want to use carbon fiber start with the engine cowl, a place
where there is quite a bit of weight to be saved. Keep it to one ply with a
few strategic stiffeners and maybe local reinforcement at fasteners.

Bob

-----Original Message-----
From: L.J. French [mailto:LJFrench@...]
Sent: Sunday, December 20, 2009 08:01 AM
To: Q-LIST@...
Subject: RE: [Q-LIST] Re: carbon

OK, I think I understand that you say the carbon spar should be able to
carry most of the loads with minimal glass. Would this be for just the
canard, and what are the minimum number of plies you think I can get by with
on the main wing?

Thanks again,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
bob@...
Sent: Sunday, December 20, 2009 12:00 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

Lighter is always better.

I built two Glasairs -- #102 (the first kit sold) and #123 -- and brought
both in under 1000 lbs empty, which is rarely done. It helped that I built
102 right next to the prototype in Washington with a lot of input from the
designers (I was their guinea pig). This was after I built an earlier
composite aircraft, a Rand KR-1, which had skins made of Dynel, a synthetic
fiber known mainly for its use as artificial hair in wigs. Dynel is NOT
good. Here are some interesting things I learned from building those
aircraft, both of which had substantial wing spars and did not take skin
strength into account in ANY stress calculations. That is, the skins were
not required to carry anything other than air loads and -- in the case of
the Glasair -- to keep the gas from leaking out. If that's the case with the
Quickie, then ONE layer of glass on the 45-degree bias should be enough.
That's all Kenny Rand used on the KR-1, he didn't even use the fabric on a
45-degree bias, and it was crappy Dynel to boot, which was great at
following compound curves but also stretched so much it transferred the
loads completely to the spars anyway.

"Yes, but this Q is a Rutan design we are talking about," you say. "It's
different from those others."

Not according to Burt Rutan when I asked him the specific question of
whether his wing designs required the skins to carry other than air loads to
meet strength targets. Rutan told me he designed the spars to take the loads
in all his homebuilt designs because it was simpler that way from a
computational standpoint. And his spars were designed with ultimate loads
double the service loads as opposed to 1.5X in a metal structure. That is to
meet a 4.4-G Utility category or a 6-G Aerobatic category where an aluminum
structure would have been designed to fail above 6.6-Gs or 9-G's.
respectively, Rutan designed JUST THE SPARS to carry 8.8 or 12-Gs.

An important thing to remember about Burt Rutan is that he worked at Edwards
AFB as a FLIGHT TEST engineer. His design process was always minimal while
his testing was rigorous, because testing is what Burt likes best. And there
is nothing wrong with that. Look at the original VariEze prototype, which
had a VW engine and no ailerons. Burt thought he could get away with the VW
because HE REALLY HAD NO IDEA WHAT HIS PLANE WOULD WEIGH. It was
under-powered so he threw another 70 lbs of engine on board without changing
ANY of the structure except to put some lead in the nose, further increasing
the weight. Ailerons, too, were added because of testing nightmares (canard
elevons turned out to be a bad idea). That same airframe today carries up to
an O-320 and is STILL plenty strong.

These planes don't BREAK, we BUST them.

These aircraft use standardized cloth that doesn't so much take into account
the needs of the design as it does the inventory of the supplier. So on
wings of this type (where the spars carry the majority of loads) a single
layer of cloth on the 45-degree bias offers enough strength to carry any
torsion loads and keep the insides of the wing on the inside. But because we
live in a real world, most designers make the skins two layers thick simply
so they will hold up better to manhandling. Others may opt for three layers
of UNI (0-degrees, 45-right, 45-left) because that's the textbook way to get
the highest performance wing -- performance that wing IS NEVER ASKED TO GIVE
because the spars are carrying the loads.

Here's a dirty little secret about composite aircraft design: most
prototypes aren't "designed" at all -- they are just built. Two layers on
the outside and one on the inside if it is a sandwich structure. And most
are left just that way. Or the prototype is too heavy so they redesign it a
little lighter, which usually means making it lighter then seeing if it
breaks. Because of the variability in materials and production techniques
there is a lot more make-and-test here than there is Finite Element
Analysis. Maybe that will eventually change but not until computers get
better or composite materials get -- like aluminum -- a lot more
standardized.

Martin Hollmann did the structural design on all the early Lancairs -- AFTER
they flew. There was a guy who wanted to fly his Lancair 320 around the
world so he asked Martin to take as much weight out of the airplane as he
could while, at the same time, increasing the gross weight and adding extra
fuel tanks. This may have been the first time a composite aircraft was
scrupulously (re)designed for minimum empty structural weight. Hollmann
dropped the strength target to the Normal category (3.8-Gs), added exotic
materials where he could, accepted a 1.5X safety factory (instead of 2X) and
managed to take 200 lbs out of a 320, dropping the weight to around 850 lbs,
of which 400, remember, was engine, accessories, and prop. Those wings had
single-ply outer skins.

There's another very interesting aspect to this. We go to a lot of trouble
and waste a lot of materials putting two or more layers of 45-degree cloth
on wings and fuselages because that's what we're told we need to carry the
torsional loads. Just roll the fabric out on the wing (0-90) and the
torsional strength is reduced by almost half. But wait -- aren't those two
layers twice as strong as they really need to be? Sure. So in practical
service you can meet the same strength with one layer at 45 or two layers at
0, with the two layers being sturdier. Well, heck, why would anyone do it
any differently than that? Kenny Rand didn't (he was a TERRIBLE engineer, by
the way) and hundreds of KR-1s flew without falling out of the skies.

Which brings me back to my point: these airplanes are under-designed and
over-built to compensate.

Look at the Qs in particular. The only real structural change was adding
carbon spars to the canard and that was in an attempt to keep bad pilots
from breaking their planes during Pilot-Induced-Oscillation (PIO) on
landing. It's questionable whether that really helped, by the way, but other
than carbon spars and improved tail springs (also a PIO issue) there were no
significant STRUCTURAL changes.

It's your plane, take some weight out of it if you like, being sure to keep
the CG where it belongs. Heck, most builders go the other way and add weight
back in for the darnedest things. DON'T DO THAT.

But here's my caution. While composites are easy to make, they don't fatigue
in a traditional sense, and they are generally so over-built that you can
make lots of changes with relative impunity, THEY WILL FLUTTER if you try to
go too fast or too high, which is why I am looking at all-carbon (and
100-percent mass-balanced controls) for my Q1.

Bob

-----Original Message-----
From: L.J. French [mailto:LJFrench@...]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@...
Subject: RE: [Q-LIST] Re: carbon

Bob,
I am building a Q and would like to make it as light as possible. Do you
think I could get by with 2 ply as long as I am careful to not hit my hanger
with it?
Thanks,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

What are the constraints on this design? On most composite designs the
deciding factor in how many layers to use on the wing skins, for example, is
hangar rash. Yes, hangar rash. Less glass could always be used but it would
be damaged too easily. So we sit around speculating about the implications
of changing materials on a design that's overbuilt in glass OR carbon. What
is the history of structural failures on Quickies? Zero. Change it to carbon
and it will still be zero.

Bob

On Dec 19, 2009, at 1:50 PM, "rick_nordgarden" <grnordgarden@...>
wrote:



--- In Q-LIST@..., "Robert X. Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS
Q1.
This is an example of how risky an untutored "common-sense" approach
to engineering can be. Make two identical foam wing cores, then skin
one with fiberglass and the other with carbon fiber. With the same
number of layers of cloth of the same weight per square yard the
carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly
stiffening a wing's skin alters its spanwise load distribution,
shifting load away from the tips and toward the centerline; the wing's
load-carrying capacity and its g-limit at a given load are both
thereby reduced. Stiffness and strength are not necessarily
complementary properties; to a great degree they're antagonistic.
This problem can be overcome by altering the number and/or weight of
the plies when switching materials, but that means re-engineering the
structure -- the fuselage and bulkheads as well as the wing- skins and
spar layups. Before you can build a *safe* all-CF Quickie you'll have
to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction



------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links



------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links



------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links


Re: carbon

L.J. French <LJFrench@...>
 

OK, great. I will make the main wing the same as the canard and try to avoid
too much Bondo. I would really like to make this thing come in under 600 lbs
since weight is the most important criteria for my design. I would also like
to fly up in that 18,000 ft range but want to be able to go faster than 204
KTS. So to do that I want to install a turbo charged O-200 instead of the
VW. That is also part of why I want to save weight on glass. I am in pretty
good health so I think I can fly up there without oxygen. I just don't like
the thought of carrying the extra weight of an oxygen bottle. I am still
thinking that part through. I think for now I will try your idea of starting
with the cowl.
Thanks for the help,

LJ

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
bob@...
Sent: Sunday, December 20, 2009 7:42 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

There is no difference between the to wings in this matter.

How much weight are you hoping to save? Most people use too much resin and
WAY too much Bondo. First improve your construction methods THEN start to
think about changing the ply schedule. But keep your hopes realistic. You'll
find a huge amount of good advice on Mark Landoll's KR-2S web site,
especially his method of laying-up glass (or carbon fiber -- his wings are
CF) first on acetate film then transferring it to the foam with an ideal
glass-to-resin ratio.

If you really want to use carbon fiber start with the engine cowl, a place
where there is quite a bit of weight to be saved. Keep it to one ply with a
few strategic stiffeners and maybe local reinforcement at fasteners.

Bob



-----Original Message-----
From: L.J. French [mailto:LJFrench@...]
Sent: Sunday, December 20, 2009 08:01 AM
To: Q-LIST@...
Subject: RE: [Q-LIST] Re: carbon

OK, I think I understand that you say the carbon spar should be able to
carry most of the loads with minimal glass. Would this be for just the
canard, and what are the minimum number of plies you think I can get by with
on the main wing?

Thanks again,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
bob@...
Sent: Sunday, December 20, 2009 12:00 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

Lighter is always better.

I built two Glasairs -- #102 (the first kit sold) and #123 -- and brought
both in under 1000 lbs empty, which is rarely done. It helped that I built
102 right next to the prototype in Washington with a lot of input from the
designers (I was their guinea pig). This was after I built an earlier
composite aircraft, a Rand KR-1, which had skins made of Dynel, a synthetic
fiber known mainly for its use as artificial hair in wigs. Dynel is NOT
good. Here are some interesting things I learned from building those
aircraft, both of which had substantial wing spars and did not take skin
strength into account in ANY stress calculations. That is, the skins were
not required to carry anything other than air loads and -- in the case of
the Glasair -- to keep the gas from leaking out. If that's the case with the
Quickie, then ONE layer of glass on the 45-degree bias should be enough.
That's all Kenny Rand used on the KR-1, he didn't even use the fabric on a
45-degree bias, and it was crappy Dynel to boot, which was great at
following compound curves but also stretched so much it transferred the
loads completely to the spars anyway.

"Yes, but this Q is a Rutan design we are talking about," you say. "It's
different from those others."

Not according to Burt Rutan when I asked him the specific question of
whether his wing designs required the skins to carry other than air loads to
meet strength targets. Rutan told me he designed the spars to take the loads
in all his homebuilt designs because it was simpler that way from a
computational standpoint. And his spars were designed with ultimate loads
double the service loads as opposed to 1.5X in a metal structure. That is to
meet a 4.4-G Utility category or a 6-G Aerobatic category where an aluminum
structure would have been designed to fail above 6.6-Gs or 9-G's.
respectively, Rutan designed JUST THE SPARS to carry 8.8 or 12-Gs.

An important thing to remember about Burt Rutan is that he worked at Edwards
AFB as a FLIGHT TEST engineer. His design process was always minimal while
his testing was rigorous, because testing is what Burt likes best. And there
is nothing wrong with that. Look at the original VariEze prototype, which
had a VW engine and no ailerons. Burt thought he could get away with the VW
because HE REALLY HAD NO IDEA WHAT HIS PLANE WOULD WEIGH. It was
under-powered so he threw another 70 lbs of engine on board without changing
ANY of the structure except to put some lead in the nose, further increasing
the weight. Ailerons, too, were added because of testing nightmares (canard
elevons turned out to be a bad idea). That same airframe today carries up to
an O-320 and is STILL plenty strong.

These planes don't BREAK, we BUST them.

These aircraft use standardized cloth that doesn't so much take into account
the needs of the design as it does the inventory of the supplier. So on
wings of this type (where the spars carry the majority of loads) a single
layer of cloth on the 45-degree bias offers enough strength to carry any
torsion loads and keep the insides of the wing on the inside. But because we
live in a real world, most designers make the skins two layers thick simply
so they will hold up better to manhandling. Others may opt for three layers
of UNI (0-degrees, 45-right, 45-left) because that's the textbook way to get
the highest performance wing -- performance that wing IS NEVER ASKED TO GIVE
because the spars are carrying the loads.

Here's a dirty little secret about composite aircraft design: most
prototypes aren't "designed" at all -- they are just built. Two layers on
the outside and one on the inside if it is a sandwich structure. And most
are left just that way. Or the prototype is too heavy so they redesign it a
little lighter, which usually means making it lighter then seeing if it
breaks. Because of the variability in materials and production techniques
there is a lot more make-and-test here than there is Finite Element
Analysis. Maybe that will eventually change but not until computers get
better or composite materials get -- like aluminum -- a lot more
standardized.

Martin Hollmann did the structural design on all the early Lancairs -- AFTER
they flew. There was a guy who wanted to fly his Lancair 320 around the
world so he asked Martin to take as much weight out of the airplane as he
could while, at the same time, increasing the gross weight and adding extra
fuel tanks. This may have been the first time a composite aircraft was
scrupulously (re)designed for minimum empty structural weight. Hollmann
dropped the strength target to the Normal category (3.8-Gs), added exotic
materials where he could, accepted a 1.5X safety factory (instead of 2X) and
managed to take 200 lbs out of a 320, dropping the weight to around 850 lbs,
of which 400, remember, was engine, accessories, and prop. Those wings had
single-ply outer skins.

There's another very interesting aspect to this. We go to a lot of trouble
and waste a lot of materials putting two or more layers of 45-degree cloth
on wings and fuselages because that's what we're told we need to carry the
torsional loads. Just roll the fabric out on the wing (0-90) and the
torsional strength is reduced by almost half. But wait -- aren't those two
layers twice as strong as they really need to be? Sure. So in practical
service you can meet the same strength with one layer at 45 or two layers at
0, with the two layers being sturdier. Well, heck, why would anyone do it
any differently than that? Kenny Rand didn't (he was a TERRIBLE engineer, by
the way) and hundreds of KR-1s flew without falling out of the skies.

Which brings me back to my point: these airplanes are under-designed and
over-built to compensate.

Look at the Qs in particular. The only real structural change was adding
carbon spars to the canard and that was in an attempt to keep bad pilots
from breaking their planes during Pilot-Induced-Oscillation (PIO) on
landing. It's questionable whether that really helped, by the way, but other
than carbon spars and improved tail springs (also a PIO issue) there were no
significant STRUCTURAL changes.

It's your plane, take some weight out of it if you like, being sure to keep
the CG where it belongs. Heck, most builders go the other way and add weight
back in for the darnedest things. DON'T DO THAT.

But here's my caution. While composites are easy to make, they don't fatigue
in a traditional sense, and they are generally so over-built that you can
make lots of changes with relative impunity, THEY WILL FLUTTER if you try to
go too fast or too high, which is why I am looking at all-carbon (and
100-percent mass-balanced controls) for my Q1.

Bob

-----Original Message-----
From: L.J. French [mailto:LJFrench@...]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@...
Subject: RE: [Q-LIST] Re: carbon

Bob,
I am building a Q and would like to make it as light as possible. Do you
think I could get by with 2 ply as long as I am careful to not hit my hanger
with it?
Thanks,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

What are the constraints on this design? On most composite designs the
deciding factor in how many layers to use on the wing skins, for example, is
hangar rash. Yes, hangar rash. Less glass could always be used but it would
be damaged too easily. So we sit around speculating about the implications
of changing materials on a design that's overbuilt in glass OR carbon. What
is the history of structural failures on Quickies? Zero. Change it to carbon
and it will still be zero.

Bob

On Dec 19, 2009, at 1:50 PM, "rick_nordgarden" <grnordgarden@...>
wrote:



--- In Q-LIST@..., "Robert X. Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS
Q1.
This is an example of how risky an untutored "common-sense" approach
to engineering can be. Make two identical foam wing cores, then skin
one with fiberglass and the other with carbon fiber. With the same
number of layers of cloth of the same weight per square yard the
carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly
stiffening a wing's skin alters its spanwise load distribution,
shifting load away from the tips and toward the centerline; the wing's
load-carrying capacity and its g-limit at a given load are both
thereby reduced. Stiffness and strength are not necessarily
complementary properties; to a great degree they're antagonistic.
This problem can be overcome by altering the number and/or weight of
the plies when switching materials, but that means re-engineering the
structure -- the fuselage and bulkheads as well as the wing- skins and
spar layups. Before you can build a *safe* all-CF Quickie you'll have
to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction



------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links



------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links











------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links


Re: carbon

Robert Cringely
 

There is one S in Glasair, Sam. It is a registered trademark.

I'm not cutting any foam for my Q. I'm making female molds for all the parts and will vacuum bag and cure them at 250 degrees in my home-made oven. I expect to finish the plane by September.


Bob

-----Original Message-----
From: Sam Hoskins [mailto:sam.hoskins@...]
Sent: Sunday, December 20, 2009 07:42 AM
To: 'Q-LIST'
Subject: Re: [Q-LIST] Re: carbon


Re: carbon

Robert Cringely
 

There is no difference between the to wings in this matter.

How much weight are you hoping to save? Most people use too much resin and WAY too much Bondo. First improve your construction methods THEN start to think about changing the ply schedule. But keep your hopes realistic. You'll find a huge amount of good advice on Mark Landoll's KR-2S web site, especially his method of laying-up glass (or carbon fiber -- his wings are CF) first on acetate film then transferring it to the foam with an ideal glass-to-resin ratio.

If you really want to use carbon fiber start with the engine cowl, a place where there is quite a bit of weight to be saved. Keep it to one ply with a few strategic stiffeners and maybe local reinforcement at fasteners.

Bob

-----Original Message-----
From: L.J. French [mailto:LJFrench@...]
Sent: Sunday, December 20, 2009 08:01 AM
To: Q-LIST@...
Subject: RE: [Q-LIST] Re: carbon

OK, I think I understand that you say the carbon spar should be able to
carry most of the loads with minimal glass. Would this be for just the
canard, and what are the minimum number of plies you think I can get by with
on the main wing?

Thanks again,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
bob@...
Sent: Sunday, December 20, 2009 12:00 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

Lighter is always better.

I built two Glasairs -- #102 (the first kit sold) and #123 -- and brought
both in under 1000 lbs empty, which is rarely done. It helped that I built
102 right next to the prototype in Washington with a lot of input from the
designers (I was their guinea pig). This was after I built an earlier
composite aircraft, a Rand KR-1, which had skins made of Dynel, a synthetic
fiber known mainly for its use as artificial hair in wigs. Dynel is NOT
good. Here are some interesting things I learned from building those
aircraft, both of which had substantial wing spars and did not take skin
strength into account in ANY stress calculations. That is, the skins were
not required to carry anything other than air loads and -- in the case of
the Glasair -- to keep the gas from leaking out. If that's the case with the
Quickie, then ONE layer of glass on the 45-degree bias should be enough.
That's all Kenny Rand used on the KR-1, he didn't even use the fabric on a
45-degree bias, and it was crappy Dynel to boot, which was great at
following compound curves but also stretched so much it transferred the
loads completely to the spars anyway.

"Yes, but this Q is a Rutan design we are talking about," you say. "It's
different from those others."

Not according to Burt Rutan when I asked him the specific question of
whether his wing designs required the skins to carry other than air loads to
meet strength targets. Rutan told me he designed the spars to take the loads
in all his homebuilt designs because it was simpler that way from a
computational standpoint. And his spars were designed with ultimate loads
double the service loads as opposed to 1.5X in a metal structure. That is to
meet a 4.4-G Utility category or a 6-G Aerobatic category where an aluminum
structure would have been designed to fail above 6.6-Gs or 9-G's.
respectively, Rutan designed JUST THE SPARS to carry 8.8 or 12-Gs.

An important thing to remember about Burt Rutan is that he worked at Edwards
AFB as a FLIGHT TEST engineer. His design process was always minimal while
his testing was rigorous, because testing is what Burt likes best. And there
is nothing wrong with that. Look at the original VariEze prototype, which
had a VW engine and no ailerons. Burt thought he could get away with the VW
because HE REALLY HAD NO IDEA WHAT HIS PLANE WOULD WEIGH. It was
under-powered so he threw another 70 lbs of engine on board without changing
ANY of the structure except to put some lead in the nose, further increasing
the weight. Ailerons, too, were added because of testing nightmares (canard
elevons turned out to be a bad idea). That same airframe today carries up to
an O-320 and is STILL plenty strong.

These planes don't BREAK, we BUST them.

These aircraft use standardized cloth that doesn't so much take into account
the needs of the design as it does the inventory of the supplier. So on
wings of this type (where the spars carry the majority of loads) a single
layer of cloth on the 45-degree bias offers enough strength to carry any
torsion loads and keep the insides of the wing on the inside. But because we
live in a real world, most designers make the skins two layers thick simply
so they will hold up better to manhandling. Others may opt for three layers
of UNI (0-degrees, 45-right, 45-left) because that's the textbook way to get
the highest performance wing -- performance that wing IS NEVER ASKED TO GIVE
because the spars are carrying the loads.

Here's a dirty little secret about composite aircraft design: most
prototypes aren't "designed" at all -- they are just built. Two layers on
the outside and one on the inside if it is a sandwich structure. And most
are left just that way. Or the prototype is too heavy so they redesign it a
little lighter, which usually means making it lighter then seeing if it
breaks. Because of the variability in materials and production techniques
there is a lot more make-and-test here than there is Finite Element
Analysis. Maybe that will eventually change but not until computers get
better or composite materials get -- like aluminum -- a lot more
standardized.

Martin Hollmann did the structural design on all the early Lancairs -- AFTER
they flew. There was a guy who wanted to fly his Lancair 320 around the
world so he asked Martin to take as much weight out of the airplane as he
could while, at the same time, increasing the gross weight and adding extra
fuel tanks. This may have been the first time a composite aircraft was
scrupulously (re)designed for minimum empty structural weight. Hollmann
dropped the strength target to the Normal category (3.8-Gs), added exotic
materials where he could, accepted a 1.5X safety factory (instead of 2X) and
managed to take 200 lbs out of a 320, dropping the weight to around 850 lbs,
of which 400, remember, was engine, accessories, and prop. Those wings had
single-ply outer skins.

There's another very interesting aspect to this. We go to a lot of trouble
and waste a lot of materials putting two or more layers of 45-degree cloth
on wings and fuselages because that's what we're told we need to carry the
torsional loads. Just roll the fabric out on the wing (0-90) and the
torsional strength is reduced by almost half. But wait -- aren't those two
layers twice as strong as they really need to be? Sure. So in practical
service you can meet the same strength with one layer at 45 or two layers at
0, with the two layers being sturdier. Well, heck, why would anyone do it
any differently than that? Kenny Rand didn't (he was a TERRIBLE engineer, by
the way) and hundreds of KR-1s flew without falling out of the skies.

Which brings me back to my point: these airplanes are under-designed and
over-built to compensate.

Look at the Qs in particular. The only real structural change was adding
carbon spars to the canard and that was in an attempt to keep bad pilots
from breaking their planes during Pilot-Induced-Oscillation (PIO) on
landing. It's questionable whether that really helped, by the way, but other
than carbon spars and improved tail springs (also a PIO issue) there were no
significant STRUCTURAL changes.

It's your plane, take some weight out of it if you like, being sure to keep
the CG where it belongs. Heck, most builders go the other way and add weight
back in for the darnedest things. DON'T DO THAT.

But here's my caution. While composites are easy to make, they don't fatigue
in a traditional sense, and they are generally so over-built that you can
make lots of changes with relative impunity, THEY WILL FLUTTER if you try to
go too fast or too high, which is why I am looking at all-carbon (and
100-percent mass-balanced controls) for my Q1.

Bob

-----Original Message-----
From: L.J. French [mailto:LJFrench@...]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@...
Subject: RE: [Q-LIST] Re: carbon

Bob,
I am building a Q and would like to make it as light as possible. Do you
think I could get by with 2 ply as long as I am careful to not hit my hanger
with it?
Thanks,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

What are the constraints on this design? On most composite designs the
deciding factor in how many layers to use on the wing skins, for example, is
hangar rash. Yes, hangar rash. Less glass could always be used but it would
be damaged too easily. So we sit around speculating about the implications
of changing materials on a design that's overbuilt in glass OR carbon. What
is the history of structural failures on Quickies? Zero. Change it to carbon
and it will still be zero.

Bob

On Dec 19, 2009, at 1:50 PM, "rick_nordgarden" <grnordgarden@...>
wrote:



--- In Q-LIST@..., "Robert X. Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS
Q1.
This is an example of how risky an untutored "common-sense" approach
to engineering can be. Make two identical foam wing cores, then skin
one with fiberglass and the other with carbon fiber. With the same
number of layers of cloth of the same weight per square yard the
carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly
stiffening a wing's skin alters its spanwise load distribution,
shifting load away from the tips and toward the centerline; the wing's
load-carrying capacity and its g-limit at a given load are both
thereby reduced. Stiffness and strength are not necessarily
complementary properties; to a great degree they're antagonistic.
This problem can be overcome by altering the number and/or weight of
the plies when switching materials, but that means re-engineering the
structure -- the fuselage and bulkheads as well as the wing- skins and
spar layups. Before you can build a *safe* all-CF Quickie you'll have
to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction



------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links



------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links


Re: carbon

L.J. French <LJFrench@...>
 

OK, I think I understand that you say the carbon spar should be able to
carry most of the loads with minimal glass. Would this be for just the
canard, and what are the minimum number of plies you think I can get by with
on the main wing?

Thanks again,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
bob@...
Sent: Sunday, December 20, 2009 12:00 AM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon



Lighter is always better.


I built two Glasairs -- #102 (the first kit sold) and #123 -- and brought
both in under 1000 lbs empty, which is rarely done. It helped that I built
102 right next to the prototype in Washington with a lot of input from the
designers (I was their guinea pig). This was after I built an earlier
composite aircraft, a Rand KR-1, which had skins made of Dynel, a synthetic
fiber known mainly for its use as artificial hair in wigs. Dynel is NOT
good. Here are some interesting things I learned from building those
aircraft, both of which had substantial wing spars and did not take skin
strength into account in ANY stress calculations. That is, the skins were
not required to carry anything other than air loads and -- in the case of
the Glasair -- to keep the gas from leaking out. If that's the case with the
Quickie, then ONE layer of glass on the 45-degree bias should be enough.
That's all Kenny Rand used on the KR-1, he didn't even use the fabric on a
45-degree bias, and it was crappy Dynel to boot, which was great at
following compound curves but also stretched so much it transferred the
loads completely to the spars anyway.


"Yes, but this Q is a Rutan design we are talking about," you say. "It's
different from those others."


Not according to Burt Rutan when I asked him the specific question of
whether his wing designs required the skins to carry other than air loads to
meet strength targets. Rutan told me he designed the spars to take the loads
in all his homebuilt designs because it was simpler that way from a
computational standpoint. And his spars were designed with ultimate loads
double the service loads as opposed to 1.5X in a metal structure. That is to
meet a 4.4-G Utility category or a 6-G Aerobatic category where an aluminum
structure would have been designed to fail above 6.6-Gs or 9-G's.
respectively, Rutan designed JUST THE SPARS to carry 8.8 or 12-Gs.


An important thing to remember about Burt Rutan is that he worked at Edwards
AFB as a FLIGHT TEST engineer. His design process was always minimal while
his testing was rigorous, because testing is what Burt likes best. And there
is nothing wrong with that. Look at the original VariEze prototype, which
had a VW engine and no ailerons. Burt thought he could get away with the VW
because HE REALLY HAD NO IDEA WHAT HIS PLANE WOULD WEIGH. It was
under-powered so he threw another 70 lbs of engine on board without changing
ANY of the structure except to put some lead in the nose, further increasing
the weight. Ailerons, too, were added because of testing nightmares (canard
elevons turned out to be a bad idea). That same airframe today carries up to
an O-320 and is STILL plenty strong.


These planes don't BREAK, we BUST them.


These aircraft use standardized cloth that doesn't so much take into account
the needs of the design as it does the inventory of the supplier. So on
wings of this type (where the spars carry the majority of loads) a single
layer of cloth on the 45-degree bias offers enough strength to carry any
torsion loads and keep the insides of the wing on the inside. But because we
live in a real world, most designers make the skins two layers thick simply
so they will hold up better to manhandling. Others may opt for three layers
of UNI (0-degrees, 45-right, 45-left) because that's the textbook way to get
the highest performance wing -- performance that wing IS NEVER ASKED TO GIVE
because the spars are carrying the loads.


Here's a dirty little secret about composite aircraft design: most
prototypes aren't "designed" at all -- they are just built. Two layers on
the outside and one on the inside if it is a sandwich structure. And most
are left just that way. Or the prototype is too heavy so they redesign it a
little lighter, which usually means making it lighter then seeing if it
breaks. Because of the variability in materials and production techniques
there is a lot more make-and-test here than there is Finite Element
Analysis. Maybe that will eventually change but not until computers get
better or composite materials get -- like aluminum -- a lot more
standardized.


Martin Hollmann did the structural design on all the early Lancairs -- AFTER
they flew. There was a guy who wanted to fly his Lancair 320 around the
world so he asked Martin to take as much weight out of the airplane as he
could while, at the same time, increasing the gross weight and adding extra
fuel tanks. This may have been the first time a composite aircraft was
scrupulously (re)designed for minimum empty structural weight. Hollmann
dropped the strength target to the Normal category (3.8-Gs), added exotic
materials where he could, accepted a 1.5X safety factory (instead of 2X) and
managed to take 200 lbs out of a 320, dropping the weight to around 850 lbs,
of which 400, remember, was engine, accessories, and prop. Those wings had
single-ply outer skins.


There's another very interesting aspect to this. We go to a lot of trouble
and waste a lot of materials putting two or more layers of 45-degree cloth
on wings and fuselages because that's what we're told we need to carry the
torsional loads. Just roll the fabric out on the wing (0-90) and the
torsional strength is reduced by almost half. But wait -- aren't those two
layers twice as strong as they really need to be? Sure. So in practical
service you can meet the same strength with one layer at 45 or two layers at
0, with the two layers being sturdier. Well, heck, why would anyone do it
any differently than that? Kenny Rand didn't (he was a TERRIBLE engineer, by
the way) and hundreds of KR-1s flew without falling out of the skies.


Which brings me back to my point: these airplanes are under-designed and
over-built to compensate.


Look at the Qs in particular. The only real structural change was adding
carbon spars to the canard and that was in an attempt to keep bad pilots
from breaking their planes during Pilot-Induced-Oscillation (PIO) on
landing. It's questionable whether that really helped, by the way, but other
than carbon spars and improved tail springs (also a PIO issue) there were no
significant STRUCTURAL changes.


It's your plane, take some weight out of it if you like, being sure to keep
the CG where it belongs. Heck, most builders go the other way and add weight
back in for the darnedest things. DON'T DO THAT.


But here's my caution. While composites are easy to make, they don't fatigue
in a traditional sense, and they are generally so over-built that you can
make lots of changes with relative impunity, THEY WILL FLUTTER if you try to
go too fast or too high, which is why I am looking at all-carbon (and
100-percent mass-balanced controls) for my Q1.


Bob



-----Original Message-----
From: L.J. French [mailto:LJFrench@...]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@...
Subject: RE: [Q-LIST] Re: carbon

Bob,
I am building a Q and would like to make it as light as possible. Do you
think I could get by with 2 ply as long as I am careful to not hit my hanger
with it?
Thanks,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

What are the constraints on this design? On most composite designs the
deciding factor in how many layers to use on the wing skins, for example, is
hangar rash. Yes, hangar rash. Less glass could always be used but it would
be damaged too easily. So we sit around speculating about the implications
of changing materials on a design that's overbuilt in glass OR carbon. What
is the history of structural failures on Quickies? Zero. Change it to carbon
and it will still be zero.

Bob

On Dec 19, 2009, at 1:50 PM, "rick_nordgarden" <grnordgarden@...>
wrote:



--- In Q-LIST@..., "Robert X. Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS
Q1.
This is an example of how risky an untutored "common-sense" approach
to engineering can be. Make two identical foam wing cores, then skin
one with fiberglass and the other with carbon fiber. With the same
number of layers of cloth of the same weight per square yard the
carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly
stiffening a wing's skin alters its spanwise load distribution,
shifting load away from the tips and toward the centerline; the wing's
load-carrying capacity and its g-limit at a given load are both
thereby reduced. Stiffness and strength are not necessarily
complementary properties; to a great degree they're antagonistic.
This problem can be overcome by altering the number and/or weight of
the plies when switching materials, but that means re-engineering the
structure -- the fuselage and bulkheads as well as the wing- skins and
spar layups. Before you can build a *safe* all-CF Quickie you'll have
to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction



------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links











------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links


Re: carbon

Sam Hoskins
 

Very interesting perspective, Bob. Your project will be good to watch. How
soon do you expect to start cutting foam?

I think it would be fun to build and fly a Glassair TD.

Sam Hoskins
Murphysboro, IL

On Sat, Dec 19, 2009 at 11:59 PM, <bob@...> wrote:





Lighter is always better.

I built two Glasairs -- #102 (the first kit sold) and #123 -- and brought
both in under 1000 lbs empty, which is rarely done. It helped that I built
102 right next to the prototype in Washington with a lot of input from the
designers (I was their guinea pig). This was after I built an earlier
composite aircraft, a Rand KR-1, which had skins made of Dynel, a synthetic
fiber known mainly for its use as artificial hair in wigs. Dynel is NOT
good. Here are some interesting things I learned from building those
aircraft, both of which had substantial wing spars and did not take skin
strength into account in ANY stress calculations. That is, the skins were
not required to carry anything other than air loads and -- in the case of
the Glasair -- to keep the gas from leaking out. If that's the case with the
Quickie, then ONE layer of glass on the 45-degree bias should be enough.
That's all Kenny Rand used on the KR-1, he didn't even use the fabric on a
45-degree bias, and it was crappy Dynel to boot, which was great at
following compound curves but also stretched so much it transferred the
loads completely to the spars anyway.

"Yes, but this Q is a Rutan design we are talking about," you say. "It's
different from those others."

Not according to Burt Rutan when I asked him the specific question of
whether his wing designs required the skins to carry other than air loads to
meet strength targets. Rutan told me he designed the spars to take the loads
in all his homebuilt designs because it was simpler that way from a
computational standpoint. And his spars were designed with ultimate loads
double the service loads as opposed to 1.5X in a metal structure. That is to
meet a 4.4-G Utility category or a 6-G Aerobatic category where an aluminum
structure would have been designed to fail above 6.6-Gs or 9-G's.
respectively, Rutan designed JUST THE SPARS to carry 8.8 or 12-Gs.

An important thing to remember about Burt Rutan is that he worked at
Edwards AFB as a FLIGHT TEST engineer. His design process was always minimal
while his testing was rigorous, because testing is what Burt likes best. And
there is nothing wrong with that. Look at the original VariEze prototype,
which had a VW engine and no ailerons. Burt thought he could get away with
the VW because HE REALLY HAD NO IDEA WHAT HIS PLANE WOULD WEIGH. It was
under-powered so he threw another 70 lbs of engine on board without changing
ANY of the structure except to put some lead in the nose, further increasing
the weight. Ailerons, too, were added because of testing nightmares (canard
elevons turned out to be a bad idea). That same airframe today carries up to
an O-320 and is STILL plenty strong.

These planes don't BREAK, we BUST them.

These aircraft use standardized cloth that doesn't so much take into
account the needs of the design as it does the inventory of the supplier. So
on wings of this type (where the spars carry the majority of loads) a single
layer of cloth on the 45-degree bias offers enough strength to carry any
torsion loads and keep the insides of the wing on the inside. But because we
live in a real world, most designers make the skins two layers thick simply
so they will hold up better to manhandling. Others may opt for three layers
of UNI (0-degrees, 45-right, 45-left) because that's the textbook way to get
the highest performance wing -- performance that wing IS NEVER ASKED TO GIVE
because the spars are carrying the loads.

Here's a dirty little secret about composite aircraft design: most
prototypes aren't "designed" at all -- they are just built. Two layers on
the outside and one on the inside if it is a sandwich structure. And most
are left just that way. Or the prototype is too heavy so they redesign it a
little lighter, which usually means making it lighter then seeing if it
breaks. Because of the variability in materials and production techniques
there is a lot more make-and-test here than there is Finite Element
Analysis. Maybe that will eventually change but not until computers get
better or composite materials get -- like aluminum -- a lot more
standardized.

Martin Hollmann did the structural design on all the early Lancairs --
AFTER they flew. There was a guy who wanted to fly his Lancair 320 around
the world so he asked Martin to take as much weight out of the airplane as
he could while, at the same time, increasing the gross weight and adding
extra fuel tanks. This may have been the first time a composite aircraft was
scrupulously (re)designed for minimum empty structural weight. Hollmann
dropped the strength target to the Normal category (3.8-Gs), added exotic
materials where he could, accepted a 1.5X safety factory (instead of 2X) and
managed to take 200 lbs out of a 320, dropping the weight to around 850 lbs,
of which 400, remember, was engine, accessories, and prop. Those wings had
single-ply outer skins.

There's another very interesting aspect to this. We go to a lot of trouble
and waste a lot of materials putting two or more layers of 45-degree cloth
on wings and fuselages because that's what we're told we need to carry the
torsional loads. Just roll the fabric out on the wing (0-90) and the
torsional strength is reduced by almost half. But wait -- aren't those two
layers twice as strong as they really need to be? Sure. So in practical
service you can meet the same strength with one layer at 45 or two layers at
0, with the two layers being sturdier. Well, heck, why would anyone do it
any differently than that? Kenny Rand didn't (he was a TERRIBLE engineer, by
the way) and hundreds of KR-1s flew without falling out of the skies.

Which brings me back to my point: these airplanes are under-designed and
over-built to compensate.

Look at the Qs in particular. The only real structural change was adding
carbon spars to the canard and that was in an attempt to keep bad pilots
from breaking their planes during Pilot-Induced-Oscillation (PIO) on
landing. It's questionable whether that really helped, by the way, but other
than carbon spars and improved tail springs (also a PIO issue) there were no
significant STRUCTURAL changes.

It's your plane, take some weight out of it if you like, being sure to keep
the CG where it belongs. Heck, most builders go the other way and add weight
back in for the darnedest things. DON'T DO THAT.

But here's my caution. While composites are easy to make, they don't
fatigue in a traditional sense, and they are generally so over-built that
you can make lots of changes with relative impunity, THEY WILL FLUTTER if
you try to go too fast or too high, which is why I am looking at all-carbon
(and 100-percent mass-balanced controls) for my Q1.

Bob

-----Original Message-----
From: L.J. French [mailto:LJFrench@... <LJFrench%40wildblue.net>]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@... <Q-LIST%40yahoogroups.com>
Subject: RE: [Q-LIST] Re: carbon

Bob,
I am building a Q and would like to make it as light as possible. Do you
think I could get by with 2 ply as long as I am careful to not hit my
hanger
with it?
Thanks,
LJ French

-----Original Message-----
From: Q-LIST@... <Q-LIST%40yahoogroups.com> [mailto:
Q-LIST@... <Q-LIST%40yahoogroups.com>] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@... <Q-LIST%40yahoogroups.com>
Subject: Re: [Q-LIST] Re: carbon

What are the constraints on this design? On most composite designs the
deciding factor in how many layers to use on the wing skins, for example,
is
hangar rash. Yes, hangar rash. Less glass could always be used but it would
be damaged too easily. So we sit around speculating about the implications
of changing materials on a design that's
overbuilt in glass OR carbon. What is the history of structural
failures on Quickies? Zero. Change it to carbon and it will still be zero.

Bob

On Dec 19, 2009, at 1:50 PM, "rick_nordgarden" <grnordgarden@...<grnordgarden%40cox.net>
wrote:



--- In Q-LIST@... <Q-LIST%40yahoogroups.com>, "Robert X.
Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS
Q1.
This is an example of how risky an untutored "common-sense" approach
to engineering can be. Make two identical foam wing cores, then skin
one with fiberglass and the other with carbon fiber. With the same
number of layers of cloth of the same weight per square yard the
carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly
stiffening a wing's skin alters its spanwise load distribution,
shifting load away from the tips and toward the centerline; the
wing's load-carrying capacity and its g-limit at a given load are
both thereby reduced. Stiffness and strength are not necessarily
complementary properties; to a great degree they're antagonistic.
This problem can be overcome by altering the number and/or weight of
the plies when switching materials, but that means re-engineering
the structure -- the fuselage and bulkheads as well as the wing-
skins and spar layups. Before you can build a *safe* all-CF Quickie
you'll have to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction

[Non-text portions of this message have been removed]

------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links

[Non-text portions of this message have been removed]



Re: carbon

Robert Cringely
 

Lighter is always better.


I built two Glasairs -- #102 (the first kit sold) and #123 -- and brought both in under 1000 lbs empty, which is rarely done. It helped that I built 102 right next to the prototype in Washington with a lot of input from the designers (I was their guinea pig). This was after I built an earlier composite aircraft, a Rand KR-1, which had skins made of Dynel, a synthetic fiber known mainly for its use as artificial hair in wigs. Dynel is NOT good. Here are some interesting things I learned from building those aircraft, both of which had substantial wing spars and did not take skin strength into account in ANY stress calculations. That is, the skins were not required to carry anything other than air loads and -- in the case of the Glasair -- to keep the gas from leaking out. If that's the case with the Quickie, then ONE layer of glass on the 45-degree bias should be enough. That's all Kenny Rand used on the KR-1, he didn't even use the fabric on a 45-degree bias, and it was crappy Dynel to boot, which was great at following compound curves but also stretched so much it transferred the loads completely to the spars anyway.


"Yes, but this Q is a Rutan design we are talking about," you say. "It's different from those others."


Not according to Burt Rutan when I asked him the specific question of whether his wing designs required the skins to carry other than air loads to meet strength targets. Rutan told me he designed the spars to take the loads in all his homebuilt designs because it was simpler that way from a computational standpoint. And his spars were designed with ultimate loads double the service loads as opposed to 1.5X in a metal structure. That is to meet a 4.4-G Utility category or a 6-G Aerobatic category where an aluminum structure would have been designed to fail above 6.6-Gs or 9-G's. respectively, Rutan designed JUST THE SPARS to carry 8.8 or 12-Gs.


An important thing to remember about Burt Rutan is that he worked at Edwards AFB as a FLIGHT TEST engineer. His design process was always minimal while his testing was rigorous, because testing is what Burt likes best. And there is nothing wrong with that. Look at the original VariEze prototype, which had a VW engine and no ailerons. Burt thought he could get away with the VW because HE REALLY HAD NO IDEA WHAT HIS PLANE WOULD WEIGH. It was under-powered so he threw another 70 lbs of engine on board without changing ANY of the structure except to put some lead in the nose, further increasing the weight. Ailerons, too, were added because of testing nightmares (canard elevons turned out to be a bad idea). That same airframe today carries up to an O-320 and is STILL plenty strong.


These planes don't BREAK, we BUST them.


These aircraft use standardized cloth that doesn't so much take into account the needs of the design as it does the inventory of the supplier. So on wings of this type (where the spars carry the majority of loads) a single layer of cloth on the 45-degree bias offers enough strength to carry any torsion loads and keep the insides of the wing on the inside. But because we live in a real world, most designers make the skins two layers thick simply so they will hold up better to manhandling. Others may opt for three layers of UNI (0-degrees, 45-right, 45-left) because that's the textbook way to get the highest performance wing -- performance that wing IS NEVER ASKED TO GIVE because the spars are carrying the loads.


Here's a dirty little secret about composite aircraft design: most prototypes aren't "designed" at all -- they are just built. Two layers on the outside and one on the inside if it is a sandwich structure. And most are left just that way. Or the prototype is too heavy so they redesign it a little lighter, which usually means making it lighter then seeing if it breaks. Because of the variability in materials and production techniques there is a lot more make-and-test here than there is Finite Element Analysis. Maybe that will eventually change but not until computers get better or composite materials get -- like aluminum -- a lot more standardized.


Martin Hollmann did the structural design on all the early Lancairs -- AFTER they flew. There was a guy who wanted to fly his Lancair 320 around the world so he asked Martin to take as much weight out of the airplane as he could while, at the same time, increasing the gross weight and adding extra fuel tanks. This may have been the first time a composite aircraft was scrupulously (re)designed for minimum empty structural weight. Hollmann dropped the strength target to the Normal category (3.8-Gs), added exotic materials where he could, accepted a 1.5X safety factory (instead of 2X) and managed to take 200 lbs out of a 320, dropping the weight to around 850 lbs, of which 400, remember, was engine, accessories, and prop. Those wings had single-ply outer skins.


There's another very interesting aspect to this. We go to a lot of trouble and waste a lot of materials putting two or more layers of 45-degree cloth on wings and fuselages because that's what we're told we need to carry the torsional loads. Just roll the fabric out on the wing (0-90) and the torsional strength is reduced by almost half. But wait -- aren't those two layers twice as strong as they really need to be? Sure. So in practical service you can meet the same strength with one layer at 45 or two layers at 0, with the two layers being sturdier. Well, heck, why would anyone do it any differently than that? Kenny Rand didn't (he was a TERRIBLE engineer, by the way) and hundreds of KR-1s flew without falling out of the skies.


Which brings me back to my point: these airplanes are under-designed and over-built to compensate.


Look at the Qs in particular. The only real structural change was adding carbon spars to the canard and that was in an attempt to keep bad pilots from breaking their planes during Pilot-Induced-Oscillation (PIO) on landing. It's questionable whether that really helped, by the way, but other than carbon spars and improved tail springs (also a PIO issue) there were no significant STRUCTURAL changes.


It's your plane, take some weight out of it if you like, being sure to keep the CG where it belongs. Heck, most builders go the other way and add weight back in for the darnedest things. DON'T DO THAT.


But here's my caution. While composites are easy to make, they don't fatigue in a traditional sense, and they are generally so over-built that you can make lots of changes with relative impunity, THEY WILL FLUTTER if you try to go too fast or too high, which is why I am looking at all-carbon (and 100-percent mass-balanced controls) for my Q1.


Bob

-----Original Message-----
From: L.J. French [mailto:LJFrench@...]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@...
Subject: RE: [Q-LIST] Re: carbon

Bob,
I am building a Q and would like to make it as light as possible. Do you
think I could get by with 2 ply as long as I am careful to not hit my hanger
with it?
Thanks,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

What are the constraints on this design? On most composite designs the
deciding factor in how many layers to use on the wing skins, for example, is
hangar rash. Yes, hangar rash. Less glass could always be used but it would
be damaged too easily. So we sit around speculating about the implications
of changing materials on a design that's
overbuilt in glass OR carbon. What is the history of structural
failures on Quickies? Zero. Change it to carbon and it will still be zero.

Bob

On Dec 19, 2009, at 1:50 PM, "rick_nordgarden" <grnordgarden@...>
wrote:



--- In Q-LIST@..., "Robert X. Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS
Q1.
This is an example of how risky an untutored "common-sense" approach
to engineering can be. Make two identical foam wing cores, then skin
one with fiberglass and the other with carbon fiber. With the same
number of layers of cloth of the same weight per square yard the
carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly
stiffening a wing's skin alters its spanwise load distribution,
shifting load away from the tips and toward the centerline; the
wing's load-carrying capacity and its g-limit at a given load are
both thereby reduced. Stiffness and strength are not necessarily
complementary properties; to a great degree they're antagonistic.
This problem can be overcome by altering the number and/or weight of
the plies when switching materials, but that means re-engineering
the structure -- the fuselage and bulkheads as well as the wing-
skins and spar layups. Before you can build a *safe* all-CF Quickie
you'll have to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction



------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links


Re: carbon

L.J. French <LJFrench@...>
 

Bob,
I am building a Q and would like to make it as light as possible. Do you
think I could get by with 2 ply as long as I am careful to not hit my hanger
with it?
Thanks,
LJ French

-----Original Message-----
From: Q-LIST@... [mailto:Q-LIST@...] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: carbon

What are the constraints on this design? On most composite designs the
deciding factor in how many layers to use on the wing skins, for example, is
hangar rash. Yes, hangar rash. Less glass could always be used but it would
be damaged too easily. So we sit around speculating about the implications
of changing materials on a design that's
overbuilt in glass OR carbon. What is the history of structural
failures on Quickies? Zero. Change it to carbon and it will still be zero.

Bob


On Dec 19, 2009, at 1:50 PM, "rick_nordgarden" <grnordgarden@...>
wrote:



--- In Q-LIST@..., "Robert X. Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS
Q1.
This is an example of how risky an untutored "common-sense" approach
to engineering can be. Make two identical foam wing cores, then skin
one with fiberglass and the other with carbon fiber. With the same
number of layers of cloth of the same weight per square yard the
carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly
stiffening a wing's skin alters its spanwise load distribution,
shifting load away from the tips and toward the centerline; the
wing's load-carrying capacity and its g-limit at a given load are
both thereby reduced. Stiffness and strength are not necessarily
complementary properties; to a great degree they're antagonistic.
This problem can be overcome by altering the number and/or weight of
the plies when switching materials, but that means re-engineering
the structure -- the fuselage and bulkheads as well as the wing-
skins and spar layups. Before you can build a *safe* all-CF Quickie
you'll have to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction






------------------------------------

Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links


Re: carbon

Jeffrey Bevilacqua <jlbevila@...>
 

Rick,
Very well said and thanks for keeping us safe.
Jeff

--- On Sat, 12/19/09, rick_nordgarden <grnordgarden@...> wrote:


From: rick_nordgarden <grnordgarden@...>
Subject: [Q-LIST] Re: carbon
To: Q-LIST@...
Date: Saturday, December 19, 2009, 10:50 AM


 





--- In Q-LIST@yahoogroups. com, "Robert X. Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS Q1.
This is an example of how risky an untutored "common-sense" approach to engineering can be. Make two identical foam wing cores, then skin one with fiberglass and the other with carbon fiber. With the same number of layers of cloth of the same weight per square yard the carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly stiffening a wing's skin alters its spanwise load distribution, shifting load away from the tips and toward the centerline; the wing's load-carrying capacity and its g-limit at a given load are both thereby reduced. Stiffness and strength are not necessarily complementary properties; to a great degree they're antagonistic. This problem can be overcome by altering the number and/or weight of the plies when switching materials, but that means re-engineering the structure -- the fuselage and bulkheads as well as the wing-skins and spar layups. Before you can build a *safe* all-CF Quickie you'll have to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction











[Non-text portions of this message have been removed]


Re: carbon

Robert Cringely
 

What are the constraints on this design? On most composite designs the
deciding factor in how many layers to use on the wing skins, for
example, is hangar rash. Yes, hangar rash. Less glass could always be
used but it would be damaged too easily. So we sit around speculating
about the implications of changing materials on a design that's
overbuilt in glass OR carbon. What is the history of structural
failures on Quickies? Zero. Change it to carbon and it will still be
zero.

Bob


On Dec 19, 2009, at 1:50 PM, "rick_nordgarden" <grnordgarden@...>
wrote:



--- In Q-LIST@..., "Robert X. Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS
Q1.
This is an example of how risky an untutored "common-sense" approach
to engineering can be. Make two identical foam wing cores, then skin
one with fiberglass and the other with carbon fiber. With the same
number of layers of cloth of the same weight per square yard the
carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly
stiffening a wing's skin alters its spanwise load distribution,
shifting load away from the tips and toward the centerline; the
wing's load-carrying capacity and its g-limit at a given load are
both thereby reduced. Stiffness and strength are not necessarily
complementary properties; to a great degree they're antagonistic.
This problem can be overcome by altering the number and/or weight of
the plies when switching materials, but that means re-engineering
the structure -- the fuselage and bulkheads as well as the wing-
skins and spar layups. Before you can build a *safe* all-CF Quickie
you'll have to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction


[Non-text portions of this message have been removed]


Re: carbon

rick_nordgarden
 

--- In Q-LIST@..., "Robert X. Cringely" <bob@...> wrote:

An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS Q1.
This is an example of how risky an untutored "common-sense" approach to engineering can be. Make two identical foam wing cores, then skin one with fiberglass and the other with carbon fiber. With the same number of layers of cloth of the same weight per square yard the carbon-fiber wing will be stiffer -- and therefore weaker. Uniformly stiffening a wing's skin alters its spanwise load distribution, shifting load away from the tips and toward the centerline; the wing's load-carrying capacity and its g-limit at a given load are both thereby reduced. Stiffness and strength are not necessarily complementary properties; to a great degree they're antagonistic. This problem can be overcome by altering the number and/or weight of the plies when switching materials, but that means re-engineering the structure -- the fuselage and bulkheads as well as the wing-skins and spar layups. Before you can build a *safe* all-CF Quickie you'll have to design one.

Rick Nordgarden
Council Bluffs IA
Dragonfly MkIIH under construction


Re: carbon

Sam Hoskins
 

The wing layups use UNI, per plans.

Sam



On Fri, Dec 18, 2009 at 10:24 PM, Jim Staud <staudjf@...> wrote:



Sam,

Is that the standard layup using only uni?

Are there any knowledgeable owners like yourself in the Dallas / Ft. Worth
area and venues to meet them?

Jim Staud

________________________________
From: Sam Hoskins <sam.hoskins@... <sam.hoskins%40gmail.com>>
To: Q-LIST <Q-LIST@... <Q-LIST%40yahoogroups.com>>
Sent: Thu, December 17, 2009 6:07:56 AM

Subject: Re: [Q-LIST] carbon

Jim, there is no all carbon Q.

I don't have any carbon in my main wing. The main wing uses standard UNI
glass, not BID. In preparation for the layups, I draw 45 degree lines on
the foam cores, to help ensure proper alignment of the two first layers,
per
plans. Perhaps, that is what you are confusing,

The only change I made to the new wing was to add one proportionately sized
spar cap.

Sam

On Wed, Dec 16, 2009 at 10:23 PM, Jim Staud <staudjf@...<staudjf%40yahoo.com>>
wrote:



If they did build an all carbon Q1, Q2, Q200, or TRI-Q, were they able to
stress test it, and what were the results?

I noticed what I think is Sam Hoskins aircraft getting a main wing
upgrade
in the Q-Talk 127 Photos. The revised main wing has noticeable carbon
strands in the BID.

Also read somewhere about someone using carbon rods as spars as opposed
to
the cylindrical carbon spar. What were the results of that experiment and
waht was the method of layup.

Did anyone ever add a carbon spar or spar caps to the main wing?

Did anyone ever grow the templates to build an upscaled wing to reduce
landing speeds and wing loading?

Did anyone ever put Q2 wings on a Q1?

Jim S.

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------------------------------------


Quickie Builders Association WEB site
http://www.quickiebuilders.org

Yahoo! Groups Links






[Non-text portions of this message have been removed]