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Re: FOAM-joint-failure-discussion

Jay Scheevel
 

Looks like my picture did not work when pasted in the body of the note, so here it is as an attachment.

Jay
FOAM-joint-failure-discussion

Jay Scheevel
 

Hi Rob,

I think we have convinced Uzair to do the right thing, but to clarify my point about the vulnerability of horizontal joints versus vertical, I add the following clarification.

For a cantilever beam, let's consider vertical versus horizontal potential shear failure planes (the bonded laminations under discussion). In brittle materials, such as styrofoam, the region where the compressive principle stress orientation is oriented 25-35 degrees to the joint is where shear failure of that joint is most likely. The maximum length of a the joint surface that could fail is limited to the length that lies within that region and where sufficient differential stress exists.

The picture below shows the stress trajectories in a flexed cantilever beam (such as a wing). The solid orange lines are the max compressive stress and the dashed are the min compressive (tensile) stress. In the upper blue region, the stress orientations are optimal for vertical joints to shear. The short green line is the largest extent of a vertical joint that will fit into this region. In the lower blue area, the stresses are oriented to favor shear failure of a horizontal joint. The green line there is the longest horizontal joint that is favorably oriented to shear in this region.


My original point is that in a long thin beam, such as a wing, a horizontal joint has more potential to shear catastrophically than a vertical joint does, thus making failure of a horizontal joint the more critical issue.

Cheers,
Jay
Re: Want to post queries

Sky Hawk
 

@Jay- Al right, no more bonding plans, dropped that idea completely :)



On Thursday, February 9, 2017 11:37 PM, "Rob de Bie robdebie@... [Q-LIST]" wrote:


 
I agree with the recommendation: stick to the plans.

However, I do not agree with your comments on a
difference between vertical and horizontal bond
lines when the foam is loaded in pure shear. The
vertical and horizontal bond lines experience the
same shear stress, and they would fail at a
similar shear load. Therefore, pay a lot of
attention to the vertical joints of the foam blocks.

This does not affect the recommendation, but we should have our facts straight.

Rob

At 18:41 09 02 2017, you wrote:
>I encourage you all of you NOT to encourage
>Uzair to deviate from the plans in any way relative to the wing structure.
>
>Charlie's advice is spot on. Bonding foam
>laminates together horizontally creates stress
>concentrations and may cause the foam to fail
>immediately adjacent to the bond line. The net
>effect would be the same as stacking foam with
>no bonding at all. Vertical butt joints between
>foam core sections, as called for in the plans,
>are perpendicular to shear loads, so are not
>prone to failure from shear loads.
>
>Follow the plans for all wing construction
>details. Small deviations from plans on the
>wingtips are the only exception that will not impact the integrity of the wing.
>
>Cheers,
>Jay Scheevel
>
>
Re: Want to post queries

Rob de Bie
 

I agree with the recommendation: stick to the plans.

However, I do not agree with your comments on a
difference between vertical and horizontal bond
lines when the foam is loaded in pure shear. The
vertical and horizontal bond lines experience the
same shear stress, and they would fail at a
similar shear load. Therefore, pay a lot of
attention to the vertical joints of the foam blocks.

This does not affect the recommendation, but we should have our facts straight.

Rob

At 18:41 09 02 2017, you wrote:
I encourage you all of you NOT to encourage
Uzair to deviate from the plans in any way relative to the wing structure.

Charlie's advice is spot on. Bonding foam
laminates together horizontally creates stress
concentrations and may cause the foam to fail
immediately adjacent to the bond line. The net
effect would be the same as stacking foam with
no bonding at all. Vertical butt joints between
foam core sections, as called for in the plans,
are perpendicular to shear loads, so are not
prone to failure from shear loads.

Follow the plans for all wing construction
details. Small deviations from plans on the
wingtips are the only exception that will not impact the integrity of the wing.

Cheers,
Jay Scheevel
Re: FOAM

One Sky Dog
 

Uzair,

The link below is what you are looking for, I do not know where you are located. If you have lakes around with docks you should be able to find a source. Start at your local lumber supply and ask if they can order it in for your dock.

Regards,

Charlie Johnson



On Feb 9, 2017, at 10:33 AM, Charlie oneskydog@... [Q-LIST] <Q-LIST@...> wrote:

Rich,

As a manufacturing engineer who has worked with pourable foam. In my opinion this method brings nothing to the table over the tried and true follow the plans methods and materials.

Mockup engine blocks have a totally different set of specifications.

Regards,

Charlie Johnson


On Feb 9, 2017, at 10:20 AM, Armilite@... [Q-LIST] <Q-LIST@...> wrote:

In the case of Bonding thin 2" Foam to make thicker Blocks for making Wings is a Bad Idea!
 
But something maybe worth looking into is using Cheap 2 part Liquid Epoxy Plastic that sets up at Room Temperature fairly quick, and even quicker with a little Heat applied. It is impervious to Gas, some Foam isn't, is light weight like Foam, Floats, is Colorable for many different Colors, can be Cast into about any Shape and Hard Points can be Cast in, or Fuel Tanks, Storage, etc, it's Sand able, Drillable, Glue able, etc! It does Expand when Mixed! Can be shipped in Drums, and different size Containers.
 
So the only Bad is, it needs some form of Mold that is Held together by Bolts or Clamps or Weight.
 
The Place I visited years ago that use's it extensively is Payr Products http://www.payr.com/ who Cast Engine Blocks, Transmissions, etc., out of the Stuff. Now I'm 6ft 320lbs and they had a Chevy Engine Small Block on a Engine stand, and I could stand on it. The guy showed me how the two parts can be just poured into a bucket and let sit, while we walked around the shop talking and came back maybe 30-40 minutes later and it was setup hard in the Bucket! They use molds made of thin wall Aluminum that just Clamp together, I don't remember the exact Pressure the Stuff Expands at, but it was fairly low. They were light Weight Clamps like on a Tool Box.
 
With CNC Routers fairly cheap today, even build able by the Home Guy, many Plans out there, you could make your own Molds from Wood, or Aluminum, even this Stuff can be used to make Molds for Fiberglass parts. It is Machine able also.
 
IF, you have ever looked at the Plastic Patio Deck Hardware that even in a 2x4 Size Shape you can't break it very easy, it's very similar stuff, very Strong, but very light Weight like Foam. So this stuff Cast and then wrapped in Fiberglass or Carbon Fiber would be very Strong! Even Stronger than the Foam and Fiberglass!
 
Just My 2 Cents!
 
Rich
 
 
 
In a message dated 2/8/2017 8:26:42 P.M. Central Standard Time, Q-LIST@... writes:

1a

Re: Want to post queries

Wed Feb 8, 2017 5:15 am (PST) . Posted by:

michaelphilips77

Sorry Mike, my bad.

In case of Q1, plans ask for 7" thick styrofoam for wings and canard.
But I can easily acquire 2" thick styrofoam, with same density as being sold on aircraftspruce.
Can I bond a few of them to get required thickness and hot wire them to make wings and canard?
Structural strength comes fiberglass, so I think it might not matter.
But any inputs on this is appreciated.


Uzair

Re: Want to post queries

Jay Scheevel
 

I encourage you all of you NOT to encourage Uzair to deviate from the plans in any way relative to the wing structure.

Charlie's advice is spot on. Bonding foam laminates together horizontally creates stress concentrations and may cause the foam to fail immediately adjacent to the bond line. The net effect would be the same as stacking foam with no bonding at all. Vertical butt joints between foam core sections, as called for in the plans, are perpendicular to shear loads, so are not prone to failure from shear loads.

Follow the plans for all wing construction details. Small deviations from plans on the wingtips are the only exception that will not impact the integrity of the wing.

Cheers,
Jay Scheevel
Re: FOAM

One Sky Dog
 

Rich,

As a manufacturing engineer who has worked with pourable foam. In my opinion this method brings nothing to the table over the tried and true follow the plans methods and materials.

Mockup engine blocks have a totally different set of specifications.

Regards,

Charlie Johnson


On Feb 9, 2017, at 10:20 AM, Armilite@... [Q-LIST] <Q-LIST@...> wrote:

In the case of Bonding thin 2" Foam to make thicker Blocks for making Wings is a Bad Idea!
 
But something maybe worth looking into is using Cheap 2 part Liquid Epoxy Plastic that sets up at Room Temperature fairly quick, and even quicker with a little Heat applied. It is impervious to Gas, some Foam isn't, is light weight like Foam, Floats, is Colorable for many different Colors, can be Cast into about any Shape and Hard Points can be Cast in, or Fuel Tanks, Storage, etc, it's Sand able, Drillable, Glue able, etc! It does Expand when Mixed! Can be shipped in Drums, and different size Containers.
 
So the only Bad is, it needs some form of Mold that is Held together by Bolts or Clamps or Weight.
 
The Place I visited years ago that use's it extensively is Payr Products http://www.payr.com/ who Cast Engine Blocks, Transmissions, etc., out of the Stuff. Now I'm 6ft 320lbs and they had a Chevy Engine Small Block on a Engine stand, and I could stand on it. The guy showed me how the two parts can be just poured into a bucket and let sit, while we walked around the shop talking and came back maybe 30-40 minutes later and it was setup hard in the Bucket! They use molds made of thin wall Aluminum that just Clamp together, I don't remember the exact Pressure the Stuff Expands at, but it was fairly low. They were light Weight Clamps like on a Tool Box.
 
With CNC Routers fairly cheap today, even build able by the Home Guy, many Plans out there, you could make your own Molds from Wood, or Aluminum, even this Stuff can be used to make Molds for Fiberglass parts. It is Machine able also.
 
IF, you have ever looked at the Plastic Patio Deck Hardware that even in a 2x4 Size Shape you can't break it very easy, it's very similar stuff, very Strong, but very light Weight like Foam. So this stuff Cast and then wrapped in Fiberglass or Carbon Fiber would be very Strong! Even Stronger than the Foam and Fiberglass!
 
Just My 2 Cents!
 
Rich
 
 
 
In a message dated 2/8/2017 8:26:42 P.M. Central Standard Time, Q-LIST@... writes:

1a

Re: Want to post queries

Wed Feb 8, 2017 5:15 am (PST) . Posted by:

michaelphilips77

Sorry Mike, my bad.

In case of Q1, plans ask for 7" thick styrofoam for wings and canard.
But I can easily acquire 2" thick styrofoam, with same density as being sold on aircraftspruce.
Can I bond a few of them to get required thickness and hot wire them to make wings and canard?
Structural strength comes fiberglass, so I think it might not matter.
But any inputs on this is appreciated.


Uzair

Re: FOAM

Rich Gillen
 

In the case of Bonding thin 2" Foam to make thicker Blocks for making Wings is a Bad Idea!
 
But something maybe worth looking into is using Cheap 2 part Liquid Epoxy Plastic that sets up at Room Temperature fairly quick, and even quicker with a little Heat applied. It is impervious to Gas, some Foam isn't, is light weight like Foam, Floats, is Colorable for many different Colors, can be Cast into about any Shape and Hard Points can be Cast in, or Fuel Tanks, Storage, etc, it's Sand able, Drillable, Glue able, etc! It does Expand when Mixed! Can be shipped in Drums, and different size Containers.
 
So the only Bad is, it needs some form of Mold that is Held together by Bolts or Clamps or Weight.
 
The Place I visited years ago that use's it extensively is Payr Products http://www.payr.com/ who Cast Engine Blocks, Transmissions, etc., out of the Stuff. Now I'm 6ft 320lbs and they had a Chevy Engine Small Block on a Engine stand, and I could stand on it. The guy showed me how the two parts can be just poured into a bucket and let sit, while we walked around the shop talking and came back maybe 30-40 minutes later and it was setup hard in the Bucket! They use molds made of thin wall Aluminum that just Clamp together, I don't remember the exact Pressure the Stuff Expands at, but it was fairly low. They were light Weight Clamps like on a Tool Box.
 
With CNC Routers fairly cheap today, even build able by the Home Guy, many Plans out there, you could make your own Molds from Wood, or Aluminum, even this Stuff can be used to make Molds for Fiberglass parts. It is Machine able also.
 
IF, you have ever looked at the Plastic Patio Deck Hardware that even in a 2x4 Size Shape you can't break it very easy, it's very similar stuff, very Strong, but very light Weight like Foam. So this stuff Cast and then wrapped in Fiberglass or Carbon Fiber would be very Strong! Even Stronger than the Foam and Fiberglass!
 
Just My 2 Cents!
 
Rich
 
 
 

In a message dated 2/8/2017 8:26:42 P.M. Central Standard Time, Q-LIST@... writes:

1a

Re: Want to post queries

Wed Feb 8, 2017 5:15 am (PST) . Posted by:

michaelphilips77

Sorry Mike, my bad.

In case of Q1, plans ask for 7" thick styrofoam for wings and canard.
But I can easily acquire 2" thick styrofoam, with same density as being sold on aircraftspruce.
Can I bond a few of them to get required thickness and hot wire them to make wings and canard?
Structural strength comes fiberglass, so I think it might not matter.
But any inputs on this is appreciated.


Uzair

Re: Want to post queries

Rob de Bie
 

Hi Uzair,

In theory you are right: a wing *could* be built
from 2 inch thick foam bonded together to form an
8 inch thick foam block. If you use micro, the
bond will be stronger than the foam itself.

But it's the risk of having areas that are not
well bonded, due to entraped air, not enough
clamping pressure, thickness variations in the
foam, and other mistakes. Let me give an example - see the attached pictures.

I've supervised a number of design & build & test
exercises at university. In the design of one
group, balsa wood was used as the core of a
sandwich beam. To achieve a desired core height,
they had to bond no less than seven layers of
end-grain balsa wood together. I addition, this
end-grain balsa wood comes in matts of blocks of
balsa, that are not glued together, so they had to glue that too.

All in all the group had to do a lot of bonding /
gluing to build a proper core. Their design
failed *way* below the target load (maybe 10% of
the target 1000 kg). It's always difficult to
point out the starting point of the failure, but
I'm sure it was a disbond somewhere in the core.

All in all I would stay away from this solution.
Keep the number of foam bonds to an absolute minimum.

Rob

At 09:27 09 02 2017, you wrote:
Ok, that's resolved.

Outboard and inboard in both wing and canard are
also butt joined. Will that not be a problem at
high speeds since they are also bonded.
My queries might seem lame, but I am a newbie and trying to learn. :)


On Wednesday, February 8, 2017 8:31 PM, "Charlie
oneskydog@... [Q-LIST]" <Q-LIST@...> wrote:



Uzair,

The core of a sandwich beam transmits the shear
loads from the bottom (tension) side to the
top(compression) of the beam. Discontinuities in
the shear web concentrate loads like bond lines
that are stiffer than the foam. Shear is the
highest at the center of the beam. Trying to
bond thin sheets together will not produce a sound structure.

As others have noted documented deaths occurred by trying this.

Shear loads are real.

Regards,

Charlie Johnson

Sent from my iPad

On Feb 8, 2017, at 4:04 AM,
<mailto:michaelphilips77@...>michaelphilips77@...
[Q-LIST] <<mailto:Q-LIST@...>Q-LIST@...> wrote:

Sorry Mike, my bad.

In case of wing and canard for Q1, plans ask for 7" thick styrofoam.
I can easily acquire 2" thick styrofoam with
same density as being sold on aircraftspruce.
Can I bond a few of them to get the required
thickness and then hot wire to make wings and canard?
The structural strength comes from fiberglass,
so I think it might not matter.
But any inputs on this can be helpful.

Uzair
Re: Want to post queries

One Sky Dog
 

Uzair,

I understand you may have concerns not being a composites designer. The bottom line is that a Q built to the plans is a proven airframe flown within the envelope.

Where people get in trouble most of the time is by altering the structure during the build thinking it will be ok, without a proper engineering review.

Designing robust light structures is harder than it looks, follow the plans and the approved mods and you will have a safe airplane.

Regards,

Charlie Johnson
Ogden, Ut



On Feb 9, 2017, at 1:27 AM, Uzair Khan uzair850@... [Q-LIST] <Q-LIST@...> wrote:

Ok, that's resolved.

Outboard and inboard in both wing and canard are also butt joined. Will that not be a problem at high speeds since they are also bonded.
My queries might seem lame, but I am a newbie and trying to learn. :)


On We dnesday, February 8, 2017 8:31 PM, "Charlie oneskydog@... [Q-LIST]" <Q-LIST@...> wrote:


 
Uzair,

The core of a sandwich beam transmits the shear loads from the bottom (tension) side to the top(compression) of the beam. Discontinuities in the shear web concentrate loads like bond lines that are stiffer than the foam. Shear is the highest at the center of the beam. Trying to bond thin sheets together will not produce a sound structure.

As others have noted documented deaths occurred by trying this.

Shear loads are real.

Regards,

Charlie Johnson


On Feb 8, 2017, at 4:04 AM, michaelphilips77@... [Q-LIST] <Q-LIST@...> wrote:

Sorry Mike, my bad.

In case of wing and canard for Q1, plans ask for 7" thick styrofoam. 
I can easily acquire 2" thick styrofoam with same density as being sold on aircraftspruce.
Can I bond a few of them to get the required thickness and then hot wire to make wings and canard?
The structural strength comes from fiberglass, so I think it might not matter.
But any inputs on this can be helpful.

Uzair
Re: Want to post queries

Sky Hawk
 

Ok, that's resolved.

Outboard and inboard in both wing and canard are also butt joined. Will that not be a problem at high speeds since they are also bonded.
My queries might seem lame, but I am a newbie and trying to learn. :)


On Wednesday, February 8, 2017 8:31 PM, "Charlie oneskydog@... [Q-LIST]" wrote:


 
Uzair,

The core of a sandwich beam transmits the shear loads from the bottom (tension) side to the top(compression) of the beam. Discontinuities in the shear web concentrate loads like bond lines that are stiffer than the foam. Shear is the highest at the center of the beam. Trying to bond thin sheets together will not produce a sound structure.

As others have noted documented deaths occurred by trying this.

Shear loads are real.

Regards,

Charlie Johnson


On Feb 8, 2017, at 4:04 AM, michaelphilips77@... [Q-LIST] <Q-LIST@...> wrote:

Sorry Mike, my bad.

In case of wing and canard for Q1, plans ask for 7" thick styrofoam. 
I can easily acquire 2" thick styrofoam with same density as being sold on aircraftspruce.
Can I bond a few of them to get the required thickness and then hot wire to make wings and canard?
The structural strength comes from fiberglass, so I think it might not matter.
But any inputs on this can be helpful.

Uzair
Re: Want to post queries

One Sky Dog
 

Uzair,

The core of a sandwich beam transmits the shear loads from the bottom (tension) side to the top(compression) of the beam. Discontinuities in the shear web concentrate loads like bond lines that are stiffer than the foam. Shear is the highest at the center of the beam. Trying to bond thin sheets together will not produce a sound structure.

As others have noted documented deaths occurred by trying this.

Shear loads are real.

Regards,

Charlie Johnson


On Feb 8, 2017, at 4:04 AM, michaelphilips77@... [Q-LIST] <Q-LIST@...> wrote:

Sorry Mike, my bad.

In case of wing and canard for Q1, plans ask for 7" thick styrofoam. 
I can easily acquire 2" thick styrofoam with same density as being sold on aircraftspruce.
Can I bond a few of them to get the required thickness and then hot wire to make wings and canard?
The structural strength comes from fiberglass, so I think it might not matter.
But any inputs on this can be helpful.

Uzair
Re: Want to post queries

Sam Hoskins
 

No, no, no! Follow the plans.

Early on there was a fatality in Canada where the builder did just what you are suggesting. He was doing a high speed fly-by and his wing came apart.

Sam

Sent via wireless Gizmo.

On Feb 8, 2017 7:15 AM, "michaelphilips77@... [Q-LIST]" <Q-LIST@...> wrote:
 

Sorry Mike, my bad.


In case of Q1, plans ask for 7" thick styrofoam for wings and canard.
But I can easily acquire 2" thick styrofoam, with same density as being sold on aircraftspruce.
Can I bond a few of them to get required thickness and hot wire them to make wings and canard?
Structural strength comes fiberglass, so I think it might not matter.
But any inputs on this is appreciated.

Uzair
Re: Want to post queries

Michael Philips
 

Sorry Mike, my bad.

In case of Q1, plans ask for 7" thick styrofoam for wings and canard.
But I can easily acquire 2" thick styrofoam, with same density as being sold on aircraftspruce.
Can I bond a few of them to get required thickness and hot wire them to make wings and canard?
Structural strength comes fiberglass, so I think it might not matter.
But any inputs on this is appreciated.

Uzair
Re: Want to post queries

Michael Philips
 

Sorry Mike, my bad.

In case of wing and canard for Q1, plans ask for 7" thick styrofoam. 
I can easily acquire 2" thick styrofoam with same density as being sold on aircraftspruce.
Can I bond a few of them to get the required thickness and then hot wire to make wings and canard?
The structural strength comes from fiberglass, so I think it might not matter.
But any inputs on this can be helpful.

Uzair
Re: Want to post queries

Mike Dwyer
 

Hi Uzair,
You won't get any response from a non question.  Tell us where you live, what you have flown, what airport are you near... Then ask a question!

Check out my building web page on the Q200 website and the flying videos.

Fly Safe,


Mike Dwyer N3QP Q200

Q200 Website: http://goo.gl/V8IrJF




On Sat, Feb 4, 2017 at 9:42 AM, Uzair Khan uzair850@... [Q-LIST] <Q-LIST@...> wrote:
 

Hi,

I am a electronics cum software techie. But I have real love towards flying machines. Want to start with Q1.

Have a lot of questions, which I want get clarified.



Thanks,
Uzair
Re: Want to post queries

Norm Parmley <norm_parm@...>
 

Uzair,
May I suggest this site as a great place too start. http://www.fastlittleairplanes.com/

Of course the Q-List forum is great to ask questions.

Regards,
Norm Parmley


From: "Uzair Khan uzair850@... [Q-LIST]"
To: Q-LIST@...
Sent: Saturday, February 4, 2017 9:42 AM
Subject: [Q-LIST] Want to post queries

 
Hi,

I am a electronics cum software techie. But I have real love towards flying machines. Want to start with Q1.

Have a lot of questions, which I want get clarified.



Thanks,
Uzair
Re: fastlittleairplanes.com

Bruce Crain
 

fastlittleairplanes.com

mylittlemgb@...
 

Just wanted to invite everyone to come and checkout the updated website for Fast Little Airplanes. As we continue to move forward we will continue to update photos and parts, and would love to hear what you think. The new shop is getting up on its feet and diversification did become required in order to move forward with the new kit and pay the bills. Wendy and I are still living on Spam and Raman noodles but we now get a chicken dinner on date night. At this time we are working on 350JD to get her back in the air by hopefully Sun N Fun. Once again this year we will be hosting the Sunshine Express 400 and a fun little challenge the day before called the Bootlegger Challenge you can check it out at www.sportairrace.org . Hope this has been a productive and blessed winter for all. Oh and before we forget our tenitive wedding date will be June 3rd 2017 at the Ona Airpark in Ona, WV.


Richard & Wendy

www.fastlittleairplanes.com
Demo Ride Request

Martin Skiby
 

I would like to see if we could bribe any Q200 drivers to come to KMIT on the 10th or 11th and provide my son and test pilot a ride in a Q200?  He has 40+hrs in the TriQ and quite a bit tail wheel time, but would like to get a ride in a Q200 for the experience and looks for any advise while testing the Q200.


Please let me know if anyone can make it over please,  It is worth a meal of course, at least.


Sincerely


Martin Skiby
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