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Old Mar 12, 2012, 10:04 PM
Tony Audsley Retired Locksmith
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Australia, WA, Perth
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Airfoil wings from Depron

I have watched very informative and well-made video’s (on You-Tube) by Experimental Airlines, on making wings from dollar tree foam board.

Unfortunately, we are unable to get this foam board in Australia but have a local distributor of Depron foam.

I have seen lots of guys bending Depron using heat guns, hot water etc etc and none of them seem to work that well for me, I either burn and melt the foam or end up burning myself.

So I decide to try the same ideas to Depron to see if it would work … COLD … and WOW .. to my amazement it did work after trying a few different methods of scoring the back of the foam.

I found that if a BEND (90 degrees or more) is requires then you need to score the back of the Depron fairly deep and fairly wide (in fact to actually break the surface skin) BUT if a more gentle CURVE is needed then it is better to score lightly (so as NOT to break the skin) with a fork … all this with tape of the face (front) of course.

Here are a couple of my attempts

Lockey
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Old Mar 12, 2012, 11:03 PM
Tony Audsley Retired Locksmith
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I am not happy about the drooping aileron or step on the upper surface if you lift the ailerons so you have a flat bottom … this is more obvious when you don’t have the full length ailerons (see pic 1 and 2)

So, I am now working on a “real” airfoil section, I can’t see why this wouldn’t work the same, here are my initial drawings. (see pic 3 and 4)

Has anyone else played around with this? .... with Depron

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Old Mar 12, 2012, 11:34 PM
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Hey Lockey,
Check out Sparks' cartoon warbird threads for the way that he makes his airfoil wings out of depron. Tapered tips, dihedral, and virtually sparless (you actually use strips of depron as spars. They are very lightweight and surprisingly strong. They are a little time consuming, but very rewarding when you get it done!
6mm depron for the spars and 3mm for the skin. When I did mine it was my first time working with depron and it turned out just as planned.
Here is a link to page 3 of the Cartoon P-40 thread:
http://www.rcgroups.com/forums/showt...1525775&page=3
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Old Mar 12, 2012, 11:49 PM
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Quote:
Originally Posted by Lockey View Post
I am not happy about the drooping aileron or step on the upper surface if you lift the ailerons so you have a flat bottom … this is more obvious when you don’t have the full length ailerons (see pic 1 and 2)

So, I am now working on a “real” airfoil section, I can’t see why this wouldn’t work the same, here are my initial drawings. (see pic 3 and 4)

Has anyone else played around with this? .... with Depron

Lockey
Hey Lockey, I do my wings exactly like you show in 3 and 4. I have had excellent results that way. When I do the ailerons, I sometimes have to put a "doubler" around where the aileron outline is and sand that to the correct taper in order for the wing top skin to "fair" into the bottom skin, if that makes any sense. Then simply cut out the aileron and sand it to the correct profile.
I hope this helps. Good luck!
Mike
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Old Mar 13, 2012, 03:15 AM
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Quote:
Originally Posted by Lockey View Post
Has anyone else played around with this? .... with Depron
Yes. I myself am slowly perfecting this technique. However this technique is old (and I thought quite well known) and I was not the first to do it. Here are some of my builds using this technique:

Planktastic: http://www.rcgroups.com/forums/showthread.php?t=1484974


Night Razor: http://www.rcgroups.com/forums/showthread.php?t=1576472


I first read of the technique several years ago from here: http://www.lecun.org/hobby/dzepron.html

And what inspired me to try it was UAVPilot's beautiful black widow: http://www.rcgroups.com/forums/showthread.php?t=1344306

In his thread he shows how he bends depron. No heat is needed to bend depron (as you have discovered).

Actually, the first time I tried bending depron I didn't use it to build a wing. I built a fuselage instead: http://www.rcgroups.com/forums/showthread.php?t=1429539


Just to clarify. I think what you have there is skinned/clay-coated depron otherwise formerly known as zepron (before the company that owned the zepron trademark went out of business). Virgin depron doesn't have a skin and doesn't need to be scored (read UAVPilot's Black Widow thread). Indeed it has the opposite problem and you need to apply tape to it to prevent it from cracking when you bend it.

My Planktastic was made out of virgin depron and my Night Razor was made out of zepron. Mainly because my supplier is inconsistent and sometimes stocks regular depron and sometimes zepron.

There is also the newer, lighter, more expensive depron aero that needs neither scoring nor tape backing. Reportedly you can bend and fold it like paper. I don't know personally because I've never used it (I'm cheap). It's what UAVPilot used to build his Black Widow.

But for me, the absolute master at building with depron has to be this Taiwanese guy who built an awesome scale He-111. He uses regular depron but only 1mm and according to him he needs neither scoring nor tape backing to bend. Let me see if I can find his thread... here it is: http://www.rcgroups.com/forums/showthread.php?t=259789
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Old Mar 13, 2012, 05:42 AM
Tony Audsley Retired Locksmith
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Thanks for the replies guys, glad to see someone else is playing with this

Yes there are some very clever guys and great modellers out there, including yourself slebetman, you have some nice looking models there

3 things I wanted to try and avoid:

1. Have the wing in 2 pieces and have to sand the front (leading edge)
2. Using 3 mm Depron (I think it is very weak and brittle)
3. Not having a “proper” airfoil section.

I think I can achieve this

Lockey
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Old Mar 13, 2012, 08:13 AM
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Lockey. Here is link to my scale model built from the Dollar store foam.
http://www.rcgroups.com/forums/showt...ghlight=basler
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Old Mar 13, 2012, 09:32 AM
Tony Audsley Retired Locksmith
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Absolutely fantastic and impressive work there Laddie, I am envious

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Old Mar 13, 2012, 09:56 AM
DLC
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I have been experimenting with similar construction, except after a couple of experiments I have eliminated all spars and made the wings full monocoque. Unfrotunately I don't have any construction photos, but photos of a couple of planes are attached. The monoplane has a 30 inch span and 3mm foam. It is a scratch design, except I used tha airfoil from plans for a builtup Sukhoi wing. The wing has a foam rib at the center, one at each tip and one at the niddle of each half span - and they are all that is inside the skin. The wing has received a lot of rough trreatment because when I started flying it I was recovering from eye surgery and the plane to ground distance was not always what I thought it was. In fact the fuselage is the second for the wing - the first was destroyed in a crash from which the wing emerged intact. It has proven to be so stiff and sturdy that if I make another one I will use 2mm foam. With the SE 5, I decided to go all of the way aand use 1mm foam. I figured that I could use the iner wing struts and fuselage mountings to form a box structure to add stiffness. That turned out to be completely unnecessary. The standalone wings were plenty stiff enough. Incidentally, the airfoil is a Clark Y. The SE 5 has also received some rough treatment. I usually fly it in a small area and it has encountered fences and trees often and the wings have not been damaged. Each wing has only one short spar. This spar is cut to provide dihedral and goes through the flat midsection and about 1 inch into each half span.

One thing I have learned is to be VERY careful about getting the trailing edges lined up, otherwise you will built a warp into the wing.
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Old Mar 13, 2012, 05:25 PM
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Quote:
Originally Posted by Lockey View Post
2. Using 3 mm Depron (I think it is very weak and brittle)
My rationale for using 3mm was because most of my flat plate planes are made out of 6mm depron. I figured folded over 3mm is just 6mm depron with air in the middle.

I suggest you just try it on one build. If still don't like it it's OK but I think you'd be surprised how strong folded over 3mm is. I was surprised myself. You could always add a layer of light glass or newspaper to further protect the foam.
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Old Mar 13, 2012, 07:07 PM
Up-Out-&-Gone
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Hi Lockey here is how I form my airliner wings from 3mm depron!

How DemonDriver Builds His Airbus A300 Wings! construire Airbus A300 aile (21 min 19 sec)
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Old Mar 13, 2012, 08:51 PM
Tony Audsley Retired Locksmith
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Thanks for the comments , pics and video guys … WOW demondriver that’s a big wing to be made from 3mm Depron

Here is my wing … or ˝ wing… (made it last night) from 6mm Depron and got what I had set out to achieve

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Old Mar 13, 2012, 11:08 PM
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Quote:
Originally Posted by Lockey View Post
Here is my wing … or ˝ wing… (made it last night) from 6mm Depron and got what I had set out to achieve
I have to say.. that's a really nice hinge. Much neater and cleaner than any of my hinges.
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Old Mar 14, 2012, 04:12 AM
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I like to roll the 3mm and 6mm depron using a piece of PVC conduit, works well and you can get some great undercambered airfoils. No need for scoring and strong.
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Old Mar 15, 2012, 08:18 PM
Tony Audsley Retired Locksmith
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Had a go at a 3mm wing, …. Don’t like it (see pics)

Here is my finished wing with slightly thinner trailing edge

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