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BrianW

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Jul 2, 2018
Messages
130
Location
Altus SW Oklahoma
Hi Home Built Airplanes Enthusiasts,

My name is Ollie Krause /snip/

View attachment 95404



Fuselage:
Our fuselage was inspired by the Legal Eagle and uses 6061 T6 aluminum tubes gusseted together. We are designing the fuselage such that no coping is needed to minimize design complexity and make it easier to construct. Please note the fuselage is in a much earlier design phase than the wing and we are yet to determine our wing attachment method.
/snip/
We'd love to hear the Home Built Airplane Community's thoughts on our designs and are open to any suggestions, concerns, comments, questions, etc. /snip/
Nicely triangulated fuselage behind the wing attach - could possibly even remove a stick or two? But forward of the wing attach, I see four diagonals in bending - same could be said for the forward structure too. Early days though.
 

Ollie Krause

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Joined
Feb 26, 2020
Messages
103
Nicely triangulated fuselage behind the wing attach - could possibly even remove a stick or two? But forward of the wing attach, I see four diagonals in bending - same could be said for the forward structure too. Early days though.
Thanks! We've come a long ways since that initial post and our fuselage design has changed a TON. Our physics team did a ton of XFLR5 simulations to ensure its dynamically stable and we're simulating it in Fusion360, Solidworks, and GrapeFEA to cross-compare results. Now that school has started up again, we're all super busy and haven't been able to keep this thread updated with our latest progress but I'll do my best to get an update out in the next few days.
 

maya.ayoub.32

Active Member
Joined
Apr 6, 2020
Messages
43
Hello!

Hope y’all are doing great, and thank you for the rib stitching idea, we’re going to try that as soon as the wing is in a good enough shape to cover it with fabric.

We recently changed the position of our spar since it did not have enough foam surrounding it to hold all of the weight, which makes the leading edge even more of a necessity. However, we’re having trouble with how to fasten the leading edge to the ribs.
Rib change (we’re also going to post soon about all the updates we’ve made to keep you all in the loop)
Old:

New:




We’re tentatively planning on using a long and thin sheet of 0.016” Aluminum 5052 H32 as our leading edge. We’ve started experimenting with different ways of bending our leading edge, and thought we could do a similar thing to the Legal Eagle or this antique reproduction of the Curtiss-Wright Model 12W biplane with the straps tying it down.
Legal Eagle:

Curtis Wright:



But we have foam ribs, so instead of nailing in the edge we epoxied it down but kept the same process with the tie-down. Unfortunately, it did not stick as well as we hoped and sprung back immediately after we took off the ties a day later.


This being said, one of the major problems was with the metal not having much contact with the fiberglass, which we have seen can be solved by adding blocks of wood between the tie and the foam, like so: (from Tom Porterfield’s restoration)


We were thinking of using gorilla glue as well instead of epoxy to see if it would stick better (since it expands), but we haven’t tested it yet.

We’ve also looked into vacuum bending it, but it seems like it just makes the metal more workable rather than completely bending to the exact shape we need.

I guess the real question here would be: Is there any other way to secure the leading edge without inserting something into our foam ribs?
Since all other planes we’ve researched/ encountered have inserted something into their ribs to keep down the leading edge, will the glue alone be enough in any scenario? If not, what could we use to function as a leading edge?

As always, thank you all for your support!
Cheerio,
Maya
 

proppastie

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Feb 19, 2012
Messages
4,762
Location
NJ
1604082968742.jpeg
We’ve also looked into vacuum bending it, but it seems like it just makes the metal more workable rather than completely bending to the exact shape we need.
need a slightly smaller tube to bend around.....you will over -bend the aluminum and spread it back onto the ribs.

I am not sure how well epoxy or any glue will work with aluminum and foam.......aluminum is hard to properly glue
 

Protech Racing

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Joined
Jul 10, 2020
Messages
187
Gorrilla glue and 9/16 in staples into the foam . The gorilla glue works very well aas prior noted . Paint it for extended life if exposed.
Scuff up the alluminum at glue points . It may still not stick. You have to over bend it for sure.
I did away with the solid LE covering and simply added extra half ribs.

Pou-Guide - "GRETCHEN", le Pou de Mike OGREN I thought there were more build pics, sorry.
 
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Protech Racing

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Jul 10, 2020
Messages
187
You can also use the green masking paper glued on the LE and a thin layer of glass over it.
Apply the paper with glue. Let it set a day. Spray/mist it with water. It will shrink.. Paint the hard points with epoxy very lightly. Cover with cloth .
 

Dana

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Apr 3, 2007
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CT, USA
You're going to want something attached at the skin edge, rather than just having it free floating. And I think you'll want a better way to transfer the rib loads to the spars beyond just a hole in the foam (unless you're skinning the foam with glass or something.

This is a design I was working on some years back. The front spar is the leading edge, the size was chosen to match the leading edge radius. The aluminum cap strips are riveted to the leading edge, and the angles that run spanwise at the thickest point (they're not spars, just light stiffeners to support the ribs). With the extra false ribs, I felt I didn't need a sheeted leading edge. Of course, this was for a biplane, so the shorter span and wire bracing meant lighter spars would work. Note this was a work in progress and was never actually built... someday I may pick it up again.

1604093931003.png
 

karmarepair

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Jan 13, 2011
Messages
283
Location
United States
View attachment 103580

need a slightly smaller tube to bend around.....you will over -bend the aluminum and spread it back onto the ribs.

I am not sure how well epoxy or any glue will work with aluminum and foam.......aluminum is hard to properly glue
I endorse ALL of the above. My suggestion: use .016 aluminum bracket behind the spar cut to fit both the spar and the airfoil, with 90 degree tabs to the top and bottom surfaces of the leading edge skin, and one to touch the tangent of the neutral axis of the spar. One aluminum pop rivet top to skin, tab to neutral axis, bottom to skin. Said skin needs to overlap the spar, and you can glue it or not.

Quick, Christmas-y sketch attached.
 

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maya.ayoub.32

Active Member
Joined
Apr 6, 2020
Messages
43
You can also use the green masking paper glued on the LE and a thin layer of glass over it.
Apply the paper with glue. Let it set a day. Spray/mist it with water. It will shrink.. Paint the hard points with epoxy very lightly. Cover with cloth .
Thank you for the staple idea we'll test it out! Checked out your project and was wondering what the replacement trailing edge is? Looks like carved out foam, but just wanted to be certain.
1604106531793.png

Very interesting process! So metal glued to masking paper, then glue that to fiberglass? Our ribs are capped with fiberglass so the attachment would definitely be stronger thanks for the advice!

General question here: Really like the idea of using more half ribs than a leading edge, so would an LE really be used for anything other than keeping up the fabric?

Thanks!
 

maya.ayoub.32

Active Member
Joined
Apr 6, 2020
Messages
43
Don't use gorilla glue. It expands to fill the gap, but turns to a brittle foam with no peel strength.
Will not anymore- thank you for saving us some prototype foam!

You're going to want something attached at the skin edge, rather than just having it free floating. And I think you'll want a better way to transfer the rib loads to the spars beyond just a hole in the foam (unless you're skinning the foam with glass or something.
Your design looks super interesting I hope it gets built! We have a sort of similar design to yours where there's foam going down the middle like so:
1604107228895.png
Where the grey foam is used as a support block to prevent any torque in the wing + small compression and tension forces. It's about 23 inches farther back than where our leading edge stops (green surface), so you recommend we create another or bring it forward, cap it with aluminum, and rivetting the leading edge to it? Genius! This could definitely work, and with Protech Racing's method of gluing the aluminum to foam this could be our winner. Thank you!

As for the stresses on the foam ribs, we've been doing testing and our best method is looks like this:
1604108025024.png
Where the foam is capped by fiberglass and a donut-shaped piece of 0.016" 5052 H32 aluminum is also epoxied on to support the spar's weight. This is a picture of our test where we were surprised that each could carry 300 lb!

Thank you again for your suggestion, and we'll test it out tomorrow + give updates.
 

Protech Racing

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Jul 10, 2020
Messages
187
MY TE was trimmed foam and a folded sheet of aluminum . Maybe 6in a aside.

I tried the alluminum LE and the glass over paper LE, and found the false ribs to be simpler, lighter and cover better due to not having the hard straight line across the rear edge.

My next wing will be the same LE and TE. The Bottom of the wing will be sheeted with 3/4 foam and the ribs placed on the sheet at angle to form almost geodetic load paths.
My spars are at 28% and 92%
 
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maya.ayoub.32

Active Member
Joined
Apr 6, 2020
Messages
43
I endorse ALL of the above. My suggestion: use .016 aluminum bracket behind the spar cut to fit both the spar and the airfoil, with 90 degree tabs to the top and bottom surfaces of the leading edge skin, and one to touch the tangent of the neutral axis of the spar. One aluminum pop rivet top to skin, tab to neutral axis, bottom to skin. Said skin needs to overlap the spar, and you can glue it or not.

Quick, Christmas-y sketch attached.
Very interesting design there (and it is indeed Christmas-sy)! It may be a lighter alternative to Dana's design, but I'm a little worried the aluminum bend will be unsupported, but there's only one way to check. Thank you for the drawing, and we will try it out tomorrow!
 

maya.ayoub.32

Active Member
Joined
Apr 6, 2020
Messages
43
Do some glue test... Gorrilla glues works well. Better than epoxy for any foam joints. 3M 5200 is also good and should be in your test .
Gotcha alright! Gorilla seems to have different results for different people so we'll check it out on the foam and see the reaction after a few days. the 3M 5200 seems to not be great with aluminum but awesome with fiberglass so we'll keep that in mind for the future- thank you!

We'll try out a few more adhesives and keep you guys updated on the results as well
 

maya.ayoub.32

Active Member
Joined
Apr 6, 2020
Messages
43
need a slightly smaller tube to bend around.....you will over -bend the aluminum and spread it back onto the ribs.

I am not sure how well epoxy or any glue will work with aluminum and foam.......aluminum is hard to properly glue
The tube I vacuum bent around for my tail-feathers was slightly less than 3/4 dia EMT electrical conduit....the size for the LE of the wing was
1 5/16 (1.312) dia. water pipe.
Gotcha so the pipe needs to be smaller than the diameter the actual LE needs to go around. With all these amazing ideas, it looks like the aluminum leading edge is still a possibility, so vacuum bending the leading edge would be worth it. Thanks for the tip and we'll do research into the infrastructure needed for a proper bend!
 

karmarepair

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Joined
Jan 13, 2011
Messages
283
Location
United States
Very interesting design there (and it is indeed Christmas-sy)! It may be a lighter alternative to Dana's design, but I'm a little worried the aluminum bend will be unsupported, but there's only one way to check. Thank you for the drawing, and we will try it out tomorrow!
I'm presuming foam ahead of the spar. And the aft edge of these little tabs should be flange to keep the free edge from buckling.

Another idea: Scallop the free edges, top and bottom, of the leading edge aluminum, in between the attachment tabs, so that most of the free edge is supported on the spar. The tension of the fabric will hold it in place. ASCII Art follows
=======================| <= End rib
| | |L < tabs |
| | | ( <scalloped edge | <= Trailing edge
| | |L |
| | | ( |
| | |===================
| | | ^ full length rib^
| ^
^ s
L p
E a
r

you can also "tweak" the free edge ever so slightly to give it a little rigidity. This is a good tool to do this on long, straight edges 8 in. Sheet Metal Clamp or you can use a sheet metal brake, or use a piece of aluminum bar stock or hardwood with a .020" wide slot about 3/4" deep sawn into the end to give you enough leverage to put a 10 degree or less crease in the edge. Bend a little, move the tool, bend a little, move the tool.
 
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