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need some help, i'm trying to cover some foam cores with fiberglass on an aerobatic airplane, i'm gonna use naca 0018 or 0016 for the airfoil, 18" @ the root and 14" @ the tip, it'll be like 3" for the camber at the root, the core is white foam 2-3 lb density, i don't know what fiberglass cloth weigth i should use to do this, i'm thinking a 3.8 oz./yd is more than enough.. help guys it look really cool on paper, but would like to make it happen...
thanks in advance
dennis

Mike James

Well, it's true that you can fiberglass foam, (You didn't mention sheeting it with balsa first) but...

There are "issues" with just glassing foam, especially for an aerobatic plane, where stresses may be high. You'd have to use several layers of glass to equal a typical balsa-sheeted (glassed or not) foam wing. One of the biggest problems is that if you damage the skin, say by denting or creasing it, you have a very weak wing left, with only foam for structure. Byron offered the foam-glassing option on their kits, but this was not ordinary styrofoam...They were injection molded, and quite a bit stronger, plus they had a molded-in metal spar.

You could use 1 lb. density foam (1/3rd the weight of what you're describing) then sheet it with lightweight 1/16th" balsa, then glass it with very light weight cloth, such as .75 oz. cloth, and you'd have a much stronger wing, that could endure some minor skin damage without failing.

In any case, you'd want to create a spar structure, but I'm sure you know that.

By the way, an 18% airfoil will work, but there are many fine flying aerobatic planes today with airfoils in the 10% to 12% range.

Good luck.

hayman

White foam is an opened cell foam, poor choice for composite core material. You should use blue or pink foam found at Lowes or Home Depot.

Bill


http://www.paonline.com/hayman/video.htm

http://rcgroups.com/links/index.php?...at=237&id=4169

3rd page
http://www.hsl.org.au/news/nl37.pdf

triangle

My Feedback: (3)

thanks mike for the suggestions, i particularly wanted to stay away from balsa, because of the expense, i'm thinking a 3d capable airplane, 80"-90" ws. with great slow flight characteristics, thats why the cord at the root is 18", i was thinking that i could probably sheeted with 1/32" balsa, and then hollow out the wing, using a hot wire, to gain some lightness lost by the balsa sheeting, once the composite is done, fiberglass-balsa-foam and then hollow out the wing... i'm probably going to use a carbon layed up-tapered spar 2 of them to and bottom and at the same time use it to hold the wing in the fuse.
the next step........... destruction test, we'll see how much it holds.......
thanks again