Date   

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@cringely.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



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@wildblue.net]
Sent: Sunday, December 20, 2009 09:13 AM
To: Q-LIST@yahoogroups.com
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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
bob@cringely.com
Sent: Sunday, December 20, 2009 7:42 AM
To: Q-LIST@yahoogroups.com
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@wildblue.net]
Sent: Sunday, December 20, 2009 08:01 AM
To: Q-LIST@yahoogroups.com
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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
bob@cringely.com
Sent: Sunday, December 20, 2009 12:00 AM
To: Q-LIST@yahoogroups.com
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@wildblue.net]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@yahoogroups.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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@yahoogroups.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@cox.net>
wrote:



--- 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



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

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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
bob@cringely.com
Sent: Sunday, December 20, 2009 7:42 AM
To: Q-LIST@yahoogroups.com
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@wildblue.net]
Sent: Sunday, December 20, 2009 08:01 AM
To: Q-LIST@yahoogroups.com
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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
bob@cringely.com
Sent: Sunday, December 20, 2009 12:00 AM
To: Q-LIST@yahoogroups.com
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@wildblue.net]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@yahoogroups.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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@yahoogroups.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@cox.net>
wrote:



--- 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



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

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@gmail.com]
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@wildblue.net]
Sent: Sunday, December 20, 2009 08:01 AM
To: Q-LIST@yahoogroups.com
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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
bob@cringely.com
Sent: Sunday, December 20, 2009 12:00 AM
To: Q-LIST@yahoogroups.com
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@wildblue.net]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@yahoogroups.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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@yahoogroups.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@cox.net>
wrote:



--- 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



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

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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
bob@cringely.com
Sent: Sunday, December 20, 2009 12:00 AM
To: Q-LIST@yahoogroups.com
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@wildblue.net]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@yahoogroups.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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@yahoogroups.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@cox.net>
wrote:



--- 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



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

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@cringely.com> 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@wildblue.net <LJFrench%40wildblue.net>]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@yahoogroups.com <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@yahoogroups.com <Q-LIST%40yahoogroups.com> [mailto:
Q-LIST@yahoogroups.com <Q-LIST%40yahoogroups.com>] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@yahoogroups.com <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@cox.net<grnordgarden%40cox.net>
wrote:



--- In Q-LIST@yahoogroups.com <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@wildblue.net]
Sent: Saturday, December 19, 2009 09:20 PM
To: Q-LIST@yahoogroups.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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@yahoogroups.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@cox.net>
wrote:



--- 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



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

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@yahoogroups.com [mailto:Q-LIST@yahoogroups.com] On Behalf Of
Robert X Cringely
Sent: Saturday, December 19, 2009 2:36 PM
To: Q-LIST@yahoogroups.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@cox.net>
wrote:



--- 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






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

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@cox.net> wrote:


From: rick_nordgarden <grnordgarden@cox.net>
Subject: [Q-LIST] Re: carbon
To: Q-LIST@yahoogroups.com
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@cox.net>
wrote:



--- 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

rick_nordgarden
 

--- 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


Re: carbon

Sam Hoskins
 

The wing layups use UNI, per plans.

Sam



On Fri, Dec 18, 2009 at 10:24 PM, Jim Staud <staudjf@yahoo.com> 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@gmail.com <sam.hoskins%40gmail.com>>
To: Q-LIST <Q-LIST@yahoogroups.com <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@yahoo.com<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.

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


[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

Jim Staud <staudjf@...>
 

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@gmail.com>
To: Q-LIST <Q-LIST@yahoogroups.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@yahoo.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.









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

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

Yahoo! Groups Links


Re: carbon

Robert Cringely
 

I'm not sure I agree with this statement. I get your point about changing materials moving around the stress concentrations, but what you describe is much more of a problem with heterogeneous use of materials -- adding carbon parts here and there. An ALL-CARBON Q1 should carry its loads exactly like an ALL-GLASS Q1. Yes, there is the prospect of loads rising some on certain metal fittings because of the greater stiffness and possibly the higher speeds, but this is a minor percentage of the total weight of hte airframe and can be handled fairly easily by moving up a gauge or two in metal thickness and using more robust fasteners.

Bob


On Dec 18, 2009, at 11:12 AM, Mike Perry wrote:

Earlier Charlie wrote " Carbon should only be used where its properties
are better than other materials it is not the magic material. . . .
Best to follow the plans unless you are a qualified design engineer."
and now "Just bring money and time." Absolutely!

You are talking about a total redesign of the Q type aircraft. Please
don't assume these substitutions are simple. It is actually easy to
make one part too strong so the load is concentrated in another part of
the structure. There will be an article in the next Q-Talk that will
explain exactly how I did that (in a test wing, not a flying airplane).

Earlier Jim Staud 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 would add, don't fly in one that had these kind of mods and wasn't
stress tested.

This entire discussion belongs on Q-Performance.

Mike Perry

oneskydog@aol.com wrote:


Just bring money and time.

Charlie


In a message dated 12/18/2009 1:14:58 A.M. Mountain Standard Time,
afarr@ihug.co.nz <mailto:afarr%40ihug.co.nz> writes:

Would it be feasible to pressurize?
Allan




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


Carbon Q's

quickieflyer <quickieflying@...>
 

I always thought a redesigned sleek carbon Q would be such a great thing. I owned the original GU canard on one of my Q's years back after it was removed for the factory built LS1 Q200. It looked as if there was carbon in that wing, but never worked at verifying it.

My question is why Bob is wanting an naturally aspirated high altitude Q1? Maybe I shouldn't bring it up, just trying to understand the appeal of such a plane.

David Hiatt
Q200


Re: carbon

Leon
 

In the
use that I will be making, pultruded carbon rods can provide 280,000
psi in tension and 320,000 psi in compression.
I do believe that you have your numbers backwards? Nice to know that I'm not the only dyslexic Q builder :-)

If the Q had been
designed with CF spar caps, the plane would be both lighter and
stronger. The time to build would have also been significantly
reduced.

Maybe not. My carbon rod LS-1 Quickie canard weighs virtually the same as my per plans GU canard. The cores were more "dog boned" than I would have liked and I did not vacuum bag. I also used more material than needed so I wouldn't have to do as much fabric cutting. I'm guessing that if I used perfect cores, optimized the skin layup schedule and vacuum bagged I might be able to shave off 5 or 6 pounds.

As for time involved I'd say that it was about the same (not counting design time). If I were to do a second I could make some more user friendly jigs to speed things up a bit.

My carbon rod canard IS considerably stiffer. Stronger? I'd have to test each to destruction to be sure. I don't plan to do so.

Price from AS+S for the rod I used, as of last night, was a touch over $300.
=========================
Leon McAtee


Re: carbon

Mike Perry
 

Earlier Charlie wrote " Carbon should only be used where its properties are better than other materials it is not the magic material. . . . Best to follow the plans unless you are a qualified design engineer." and now "Just bring money and time." Absolutely!

You are talking about a total redesign of the Q type aircraft. Please don't assume these substitutions are simple. It is actually easy to make one part too strong so the load is concentrated in another part of the structure. There will be an article in the next Q-Talk that will explain exactly how I did that (in a test wing, not a flying airplane).

Earlier Jim Staud 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 would add, don't fly in one that had these kind of mods and wasn't stress tested.

This entire discussion belongs on Q-Performance.

Mike Perry

oneskydog@aol.com wrote:


Just bring money and time.

Charlie


In a message dated 12/18/2009 1:14:58 A.M. Mountain Standard Time,
afarr@ihug.co.nz <mailto:afarr%40ihug.co.nz> writes:

Would it be feasible to pressurize?
Allan


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