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Old Sep 20, 2008, 08:45 PM
"what ever just crash it"
luger007's Avatar
South Kingstown, RI
Joined Apr 2005
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pre-fab composite wing skins

Just wondering if anyone has made flat composite skins on a sheet of waxed glass, then covered with peal ply and vacuumed down. The glass side would give a great surface finish and the peal ply side would give a great bonding surface. After its cured, cut out the appropriate size skin like you would with plywood and attached them to a foam wing? I'm having a hard time finding 1/64 plywood in anything larger than 12"x 48" long, and I have a large wing that is wider than 12" to cover.



Just a thought, anyone tried it?

Matt

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Old Sep 20, 2008, 09:07 PM
Knowledge increases life's FOV
Sled Driver's Avatar
Third Stone from the Sun
Joined Nov 2003
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It works great, back in the dark ages, e.g., the 1990's, that is the way we started getting some light composite HLG's, but the technique worked fine with heavier laminate also...

Quote:
Originally Posted by luger007
Just wondering if anyone has made flat composite skins on a sheet of waxed glass, then covered with peal ply and vacuumed down. The glass side would give a great surface finish and the peal ply side would give a great bonding surface. After its cured, cut out the appropriate size skin like you would with plywood and attached them to a foam wing? I'm having a hard time finding 1/64 plywood in anything larger than 12"x 48" long, and I have a large wing that is wider than 12" to cover.



Just a thought, anyone tried it?

Matt
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Old Sep 20, 2008, 09:50 PM
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United States, CA, Mission Viejo
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Plywood ? How about Aircraft Spruce?

Does any of this look like what your looking for?


Plies Thickness Half Sheet Full Sheet
Nom. In. mm Part No. Price Buy Part No. Price Buy
3 1/64 0.4 02-20250 $24.25 02-20200 $48.50
3 1/32 0.8 02-20350 $13.75 02-20300 $27.25
3 -3/64 1.00 02-50050 $16.00 02-50000 $32.00
3 1/16 1.5 02-20450 $16.75 02-20400 $33.50
5 3/32 2.5 02-20550 $26.25 02-20500 $51.65
5 1/8 3 02-20650 $28.75 02-20600 $57.50
10 3/16 5 02-20750 $35.00 02-20700 $73.50
12 1/4 6 02-20850 $45.50 02-20800 $90.00
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Old Sep 21, 2008, 08:54 AM
"what ever just crash it"
luger007's Avatar
South Kingstown, RI
Joined Apr 2005
906 Posts
rzzzz, Thanks for the heads up on Aircraft Spruce. The first item on the list looks like what I am looking for, now I need to find out what shipping is going to cost?! I'm pretty sure Maurice L Condon Lumber in White Planes, NY has the super thin aircraft plywood too, BUT it's a 4+hour round trip! I'll have to weigh the cost of fuel against the shipping cost.

I have the fiberglass as well as a bit of carbon and kevlar, so I just thought I'd throw the idea out there for pre-fab composite skins to see if it's been done before and how it worked out. (0hr. driving, $0 shipping

M
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Old Sep 21, 2008, 09:24 AM
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United States, CA, Mission Viejo
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Pre Cure Skins

I pre cure when I am working with the Honeycomb Core all the time. There is no reason not to do it with Foam Cores. I have seen some magazine articles in the past about doing it that way.

For the plywood, check with some hardwood suppliers, they can usually get it for you and if you pick it up save on the shipping.

For the 1/64" they can roll it up for you and I cant imiagine that the shipping would offset the fuel ant time value. I am shopping online all the time, and Aircraft Spruce is 30 miniutes away from me. My problem is that I am like a kid in a candy strore whan I walk in. There is a great place for breakfast (Flos) at Chino Airport, thats how I justify the trip, that way I just pick up my order while I am out there.

How much of the Plywood do you need? I may have enough here to hook you up ???

Good luck

Rick
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Old Sep 21, 2008, 10:02 AM
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United States, MS, Amory
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Quote:
Originally Posted by rzzzzz
I There is a great place for breakfast (Flos) at Chino Airport
Ooooo airports and foooood!!!

My two favortest things.
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Old Sep 21, 2008, 10:05 AM
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Pleasant Grove, UT
Joined Jul 2005
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Just wondering. Why pre-fab'd wing skins at all? Why not just vacuum glass and carbon directly down to the cores?
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Old Sep 21, 2008, 10:06 AM
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Sled Driver's Avatar
Third Stone from the Sun
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If you have the fiberglass and resin, some thing to lay it up on, and are interested in saving money, I would encourage you to try laying up a piece of composite skin. Fiberglass skins are much cheaper than thin plywood today.

Here's how I do it:

1. I used a piece of plate glass for large pieces, because I got the glass from a friend, but I also use a piece of Mylar adhered with 3M77 to a substrate, e.g., plywood or MDF.

2. Wax and buff the surface like you would Mylars for bagging. Paint the surface if you want a paint transfer finish; I use primer a generic finish.

3. I use a red Sharpie to make alignment lines on the paint or glass, e.g., to make the direction for uni material and bias direction for bias material.

4. Layup the material.

5. Place the layup in the bag. I remove excess resin by covering the layup with a perforated peal ply (I use a Teflon coated fiberglass) covered with a absorbent paper towel.

6. Suck the bag down with your maximum available vacuum and allow to cure completely. Add heat for post cure if desired.

7 Remove from the bag and use compressed air to lift the layup off the surface, you might need to use a piece of tape or razor blade to lift a corner for the compressed air to get under.
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Old Sep 22, 2008, 08:30 AM
"what ever just crash it"
luger007's Avatar
South Kingstown, RI
Joined Apr 2005
906 Posts
Rzzzzz: Thanks for the offer, but I probably need 3 sheets 48x48 to build the PSS and 60" ers I have in kit form. Geez, I WISH I lived 30min from the aircraft supply house.

jfinch: Some kits don't have the nose or trailing edges on the cores because they are intended to have a sub LE & TE put on them, get skinned and then a real LE and aileron stock, then cover with glass or film. Trust me the wings I can bag 'taco' style in mylars and a vacuum bag will get done that way. It is faster easier and probably a little bit lighter. The only negative is if you make a tiny mistake, the wings are no good and get chucked. The 'sheeting' method has a little more leeway since the skins are oversized and get trimmed afterwards. I was thinking with 'composite sheeting' it would save glassing the balsa or ply afterwards.



Sled Driver: I do have both fiberglass and resin as well as mold release, peal ply, bagging film and a 85 x 20x 1/2" piece of plate glass. I have pre-made composite skins in the past for various projects; I've just never used them on R/C sailplane wing skins. I like your idea of using mylar on a piece of plywood, I used glossy Formica over a 1/4" ply bent over a form in the past as my 'mold'. It was a great way to pre-shape the glass in a curve as was the case with the skateboard deck. There is also no reason it couldn't be bent into an airfoil! For a symmetrical wing, you would only have to make one mold, cut exactly to size and glue together with 'splooge' and an appropriate spar inside. I also like the compressed air 'release system' that is exactly how we use to pop racing car hoods out of their mold. It's like magic! Just get the edge started, let the air rip and before you know it, "pop" out she comes .



Looks like I may do some laminating over the next few weeks! (between repairing my house and finishing the electricals on the 2nd floor renovation) The fiberglass will be cheaper and easier to get than the ply, though there is something very nice about working with wood, it's not itchy!



Matt

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Old Sep 22, 2008, 08:52 AM
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Ward Hagaman's Avatar
San Diego
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Matt, have you considered using G10 as a wing skin? G10 is a cured epoxy/fiberglass sheet, available in various thickness (3, 5, 10 thousands). It costs about the same as plywood from some sources, and is available in 36 X 48" sheets.

Ward
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Old Sep 22, 2008, 03:50 PM
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United States, MS, Amory
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This is sounding pretty good. I was just thinking for the top skin, leave it long and make a hinge out of it. I'm thinking it would be easier to finish the ply.

Gene
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Old Sep 23, 2008, 05:22 PM
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United States, TX, Weatherford
Joined Dec 2005
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I'm going to try this on some scrap foam to see how well the skin will stick....sounds like a good idea, especially if the fit-n-finish is better than my last set of bagged wings!
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Old Sep 23, 2008, 06:39 PM
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United States, CA, Lake Forest
Joined Feb 1999
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One of my first jobs was helping build Snipe slope gliders for Jerry Bridgeman. We used G-10 skins over blue foam cores and laid a big rope of uni tow in the leading edge cavity. The method worked well but the thickness of G-10 we used was heavy for better wind penetration and abuse. The only downside is the reduced bond to the core vs wet lay up but the upside was easy to repair skins if there was delam. It was really quick to build those wings once you had templates and the method down.
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Old Sep 24, 2008, 08:04 AM
"what ever just crash it"
luger007's Avatar
South Kingstown, RI
Joined Apr 2005
906 Posts
I had considered using G-10 as skin but not for long, as it's something I would have to order just like plywood. I prefer working with wood and Aircraft Spruce has 48"x48" pieces they can roll up and ship. (ML. Condon in White Planes did not have 1/64ply) However for what the plywood will cost me, I can lay up many, many yards of fiberglass skins with a little carbon tow and many strips of Kevlar. A single sheet of 1/64 x 48x 48 ply from Aircraft Spruce is $48.50! I paid $4/yrd x 50 for my fiberglass years ago.
I was trying to use materials 'on hand' for builds so I didn't have to order the expensive material.

Troy, where the G-10 is finished smooth on both sides, my lamination idea would be smooth on one side ONLY and have a slick opposite side almost ready for paint.. The peal ply in the laminating process would provide superb bonding to the entire inside surface of the skin without any sanding. The slick outsides that were on the waxed glass would require the mold release be removed before any paint would stick to it

Looks like this is going to be a 'go' when I get 'to be fixed projects' off my bench!
Cheers,
Matt
Ps. you could even lay-up a strip of kevlar in the pre-made skin if you knew where your hinges were going to be, for live hinges!
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Old Sep 24, 2008, 06:53 PM
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Yep, if you have some glass to do the lay up it is quick and easy. Using peel ply will be a major plus. You could also pre paint or prime on the glass to do paint transfer after lay up. We use to rough up the G-10 inner surface quite a bit but still wet lay up directly on foam acts like a million little rivets. But if you are doing a thick enough lay up it should behave like G-10, thinner laminates without mylar will likely be a lumpy mess if vacuum bagged. Were you going to bag or press the skins?
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