ORIGINAL: Caygeon Flyer
The advice that I have so far is to use an initial layer of 3.5 oz. satin cloth. Then two layers of 6 oz. cloth, with a sandwich of 2 mm thick foam in key areas, such as the hull bottom, to improve stiffness and rigidity.
Also some carbon fiber reinforcement in high stress areas, such as a vertical run up the large fin to the stabilizer attachment point, and in the tail boom.
Also a couple of bulkheads in the centre cabin area under the wing to provide stiffness and support from the wing and motor mount down to the hull bottom to carry landing loads.
Am I headed in the right direction with this?
Comments are welcome!
Yes I think you are.... A couple things I'd suggest. As your initial fill coat, 3.5 ounce glass is possibly too thick or coarse. You might consider something finer weaved and tightly weaved. There are some very good 1.5 ounce and 2 ounce glass fabrics in various weave patterns that might work better. There is also a nonwoven glass product (looks like silkspan) that is designed as the cosmetic initial layer
Some types of foamare good for noise suppression...polystyrene expanded beads for example. But not terribly strong structurally unless you used higher density foam in the 3-4 pound per cubic foot range.
Airex or Herex foams are much better as structural foams. These are vinyl expanded materials and fairly rigid in the 2 pound density area. That's probably material you should consider. Airex is available in US and Canada and Herex in Europe. For your application, 1/8" thick should be thick enough.
Don't eliminate good ol' balsa from consideration. When sandwiched between 2 layers of 6 ounce glass or carbon, this material becomes incredibly strong and stiff. On the bottom of the hull, 1/8" to 3/16" contest grade balsa will work great. Also in the hull area where it will see lots of wear and tear, maybe a layer of kevlar outside and carbon on the inside. Kevlar is leather tough and should be able to stand up to abuse better, but it doesn't have the max tensile strength or modulus carbon and certain glass have. Something to keep in back of mind....
On the lay-up of the glass and carbon, bias lay-up gives you rigidity in torsion. If you used balsa as the filler run the grain along the long axis of the fuse and the glass and carbon on bias. You will get a good balance between torsional rigidity and longitudinal and transverse rigidity. Fuselages need all of the above
Iassume you know your epoxies. There's an awful lot of them anymore. Several expensive ones are great choices. But there are some inexpensive ones that are also good choices in terms of strength, wet-out and curing with decent pot lives. Aircraft Spruce is one good source. ACP another, CST Sales another, CJ Composites and US Composites are yet other good sources