Stick built u/cambered wing - how to strengthen

[Nigelp]

Hi,

Am building an electric slowflyer - All up weight around 7 oz. Sedate flyer - not capable of inverted flight. The wing is heavily undercambered, no spars (only L.E. & T.E.) covered on upper surface only (Solite). Span 30" - dihedral, chord 8".

Using hard(ish) balsa L.E. the wing is useless - floppy etc and bends when covering is shrunk.

I made a wing with spruce L.E. & T.E. - much better but weighed a ton ! (1.5 ounces !)

My question is: Can carbon fibre help me in terms of stiffening the wings - and if yes, which kind.

(have searched the net for days and really can't find anything that indicates how the various materials can be used and how - other than vac bagging spars !)

Sorry to ramble on,

Would appreciate some help.

Nigel

[davidfee]

It sounds like you need a spar (at least). If you use carbon rods for the LE and TE you might get away without a spar, but I doubt it.

Can you just go without shrinking the solite?

Can you give more details about the areas of weakness? Is it primarily a floppy problem, or a twisty problem?

-David

[Nigelp]

Hi David,

Thanks for your reply.

Primarily a 'twisty' rather than floppy situation.

The wing built with spruce / balsa laminated spars was fine in terms of 'twist' resistance and resistance to the Solite shrinkage - it just weighed a ton (relatively !)

I am obviously not familiar with C.F. and therefore wondered if I could make my laminated L.E & T.E with C.F. (unidirectional cloth ???) either in a vertical format sandwiched between hard balsa (presume this wouldn't solve the shrink problem - or epoxied to the flat bottom of the hard balsa L.E. & T.E. - with a weight saving when compared to spruce !?

Nigel