Foam wing construction
 

Hi,

I'd like to try to make my own foam wings for a simple 48" span 'hack' come combat model and just had a couple of questions if anyone could help?

1) I don't want to skin the wings with obechi or balsa due to cost, availability and difficulty so I was wondering what would be a good alternative method; brown paper & PVA/aliphatic, tissue & water based polyurethane varnish (the Miniwax/Ronseal/Polycryllic stuff), glass-cloth and epoxy, etc. ? Preferably the cheaper the better ;)

2) Do I need to use a full length spar or would a shorter, full-chord-thickness brace/joiner be adequate (I'm thinking about having to cut a slot for the spar[:o] )? Panels to be joined at the centre with glass-cloth and epoxy as usual.

I'm not so bothered about impact resistance - as the whole idea is to be able to quickly make cheap wings - but I don't want the things folding in flight (gotta be cheap too! Did I already mention that:D).

Any comments, tips, advice would be much appreciated. Thanks.

Blue

RE: Foam wing construction
 

I have a "slow" combat that is cut from white foam it does have spar on the top and bottom cut into in I think it is 1/4 inch by 1/8th full length with a mono-cote type covering thats it. Full lenght is 42 inches and I use rubber bands to keep it on the plane. I have never had a problem either have the 10 guys that I fly against. I run a .15 os on it so no it's not going fast but. You said that it is a beater type plane I think you would be ok with just full length spars and no glass or balsa sheeting, let us know how it works.

RE: Foam wing construction
 

Blue:
I built a couple of combat wings this way. After cutting the cores, cut slots for 3/16 or 1/4 in spars. I cut the slots with the hot wire with small templates on the ends of the wings. Glass the centre 3 or 4 in wide. cover with plastic stickyback shelf paper. i think I glued on a 1/4 in trailing edge piece to attach the ailerons to. Just used wood glue for the spars. More or less a disposible wing. Have fun.

RE: Foam wing construction
 

Thanks guys - your replies are very much appreciated!

BTW did you use balsa or basswood/spruce spars? Thanks again,

Blue

RE: Foam wing construction
 

Blue:
Hard balsa spars with wood glue. Drainpipe fuse. One with a Fugi 15, the other with a 25 FP. Both are flying wings. You could pull as hard as you want at any speed. both still together. The skin gives it strength as well as spars. Wing held on with rubber bands.

RE: Foam wing construction
 

Flypaper2 (Gord),

Just been shopping for the wire and wood for the bow. I've also found some big sheets of white polystyrene foam in a local DIY store so I'm on my way:)

I was wondering about buying a soldering gun and making a 1/4" square wire tip for it then cutting the spar slots using a long metal straight edge (rule). There should be enough foam to make (or rather, mess up) at least 3 pairs of wings - the great learning curve begins.

I think I have some spare 1/4"sq hard balsa from a Morris Hobbies kit (!). Although it will add some weight I was also thinking that the ol' brown packing paper & PVA glue covering would add extra strength to the wings and can quickly be spray-painted. But I'll glass the centre section join which ever way I finish the wings.

Yup, drainpipe fuse;) and either 1/4" balsa sheet or Correx/Coroplast tail feathers. Should go pretty quick with an MVVS .40 huh ?

I really appreciate you taking time out to reply to my questions - cheers !

All the best,

Blue

P.S. Am going to use a simple symmetrical wing section, constant chord and no dihedral, attached with the rubber bands - SPAD influenced but hopefully lighter.

RE: Foam wing construction
 

Take a look at RACores site. In the Northeast, Gremlin contests (flying wings) have been pretty big for years, and RACores sells the foam cores for the wings, with spar slots cut, etc. for $12. They also have short kits and kits.

http://www.racores.com/current_products.html#Gremlins
Dennis-

RE: Foam wing construction
 

Yes, Dennis , looks much like theGremlin, except my own airfoil.
Blue:
I just use .020 piano wire for the bow. I have three or four bows of different sizes, but the one I use the most is an old beater made from a piece of plastic hot water pipe bent around into a bow with S shaped hooks into holes drilled the ends of the water pipe. Really light. Been cutting foam wings since the 60s. Sometimes I use the soldering gun the way you mentioned, using copper house wire. 10 or 12 gauge I think. Good for cutting out servo pockets too.

RE: Foam wing construction
 

Dennis - thanks for the link but by the time I've imported the Gremlin cores/kit into the U.K. they won't be so cheap. Nice looking plane tho - maybe I'll see how much one is after my flying skills have improved a little;). Lots of info on that site too, cheers.

Flypaper2 - yup I went for a 0.020 S/S guitar string (picked that idea up from another site). Bow will be a wooden 'H' shape with bungee elastic across the top to tension the wire. Supply is a 4amp car battery charger run from a VARIAC (big rheostat that allows variation of the mains voltage into the charger). Seems to work on scraps of white foam o.k.

Just have to make some templates now and practice, practice, practice.

Thanks again guys!

Blue