Wiker

I'm going to reinforce a pre-buildt fibre glass fuselage (from a sailplane kitt). I want it to be stronger so that it will take more rough "landings" (i.e. uncontroled crashes) before it break. I'm not an experienced pilot so I do go down very hard some times. [&o]

My first though was to use carbone and/or kevlar - carbone is stiffer (stronger?) and kevlar is very impact resistante. Then I started thinking, will these materials (glass, kevlar, carbon) actually work together to handle the forces when the plane hits the ground, or will the materials just work one by one. Carbon is the stiffest and will (obviously?) be first in line and take most/all of the load until it breaks. Then the energy will tranfere to the next material in line (glass or kevlar), which will take over handling the load by itself ut til it breaks. Following this logic the the fuselage, which is already made of glass, should be stronger by an additional layer of glass than a layer of carbon/kevlar - or should it?

canadianjosh

Kevlar and carbon cannot take damaging impact forces together at all!! Carbon is so stiff that it will simply fracture before the kevlar bears any of the load, however when this happens, your kevlae will hold together this mess of fractured carbon which is not easy to repair( think of a broken egg that has been hit hard enough to break it and the shell is still held together by theat stretchy stuff on the inside layer), glass is simply a composite that is cheap and relatively easy to fix, and has both properties of being stiff and somewhat forgiving before fracturing. There are essentially very few functional applications of kevlar in r/c modeling. All composites cannot really be used for reinforcing and object to withstand crash impact, if you're seriously talking about that then maybe you should check out those AIRCORE airplanes that are claimed to be indestructable. Investing time and money into carbon/kevlar even glass fuses if you are going to run it into the ground is not very wise. With that said, relativley speaking, kevlar will withstand inpacts better than any other composites, but it will no be stiff enough unless you do about 6 or 7 layers, at which point you may as well be flying a lead weight, this is where the glass and carbon come in to reinforce this, but again, if it's going into the ground the main fuse may survive, but all of your carbon formers won't, and you'll have the task of replacing them at the expense of more time and money. I suggest if you want to do something really cool, learn to fly first well on a trainer, made from good old trees, or if you absolutley need to try to learn yourself(i know the urge is there) start small and work up from there, seriously look into one of those ugly foam planes, they'll survive rough "landings" better than anything else, then invest time and money into building a nice plane like the glass fuse you have and reinforcing it here and there, or maybe even molding a whole new fuse from carbon, what ever floats your boat!!