Is there a resource or rule of thumb for deciding how many layers are needed on a composite airframe tube. I want to try rolling a 38mm carbon tube, 5.7oz cloth, and trying to keep it light. For this exercise, the airframe will not have to survive supersonic flight. Based on my past fiberglass experience, I was thinking 3 wraps. This will be my first attempt at an all carbon airframe. Everything I've done before was wrapped over cardboard or phenolic, so the layer count is something of a shot in the dark. Opinions and experiences are appreciated, but please be clear which one your recommendation is based on. Thanks.
I've seen carbon tubes fly that were a single wrap of 5.7oz fabric. You could nearly flatten it with your fingers, but it was rigid enough for an H motor. It is a matter of what you're trying to do. If you need a single use rocket for an absolute minimum weight altitude project, there you go. However, if you want something a bit more durable, you'll need to have enough wraps for rigidity in multiple directions. If you're building a multi-use sport rocket, I'd do 3 wraps and then cover it with a bi-axial sleeve.
One other thing, if you're using a commercial nose cone, you might consider enough wraps to build up sufficient thickness for the nosecone shoulder. I typically get layer thickness of .01 without vacuum-bagging with 5.7oz fabric. It gets better with v-bagging, about .008"
I'd tend to go with 3 wraps as well. Most commercial composite tubes are thicker than 3 wraps, but honestly, 3 wraps should be more than enough, and it should give you a good, strong, durable tube without it becoming too heavy.
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