One thing I have found about rocket construction is that there’s not just one ‘right’ way of doing things, in other words there can be many different approaches that can work on a given application. Here’s one way I’ve come up with to fiberglass body tubes and come up with a nice smooth finish all at the same time. I usually fiberglass whole lengths of tubes at one time and cut them to the length needed afterwards.
I generally use ‘flex phenolic’ tubing but the method works well on paper tubes also as long as you sand the gloss layer with a course sandpaper such as 80-100 grit to allow the epoxy to ‘soak’ in the tube. Some have recommended peeling the outer layer of ‘glassine’ off but I’ve never been that ambitious and have had good results just sanding. I lay out the fiberglass flat, roll the body tube up in it the desired number of layers (depending on motor impulse level anticipated), and cut the cloth with a little overlap on the joint and the ends. If you cut it straight with the weave in the cloth you will have minimal loose strings to deal with, if you have any pull these loose to avoid them causing lumps in the finished product.
The next step is where you may need a little help, roll the tube tightly in the cloth and while holding the cloth rolled up on the tube have your helper roll a leg of women’s nylons down over the tube to completely envelope the tube and the cloth
At this point I use a twist tie to hold the open end of the nylons leg closed. After you get it tied off you can go back and smooth out any wrinkles that may have shown up under the nylon ‘veil’. This is generally easier if you start with ‘queen sized’ nylons on the tubes 4”- 6”, but is fairly easy with ‘normal sized’ nylons on anything smaller. At this point you have the hard part done; you can don the latex gloves and mix up a batch of epoxy. I generally use the stuff that cures in 30 minutes or so. I’ve found using the cheap paintbrushes available at Wal-Mart on the smaller tubes or the smaller paint rollers on the bigger tubes minimizes the mess and makes epoxy easier to apply. Hold the tube horizontal and start laying that stuff on!
When you get the whole tube coated and the epoxy worked in so the cloth goes transparent work out any bubbles you have and hang it up by the twist tied end to cure. If you didn’t use too much epoxy it shouldn’t run down too much but after 15 minutes or so you can turn it over to even out the ‘flow’. After it’s cured just trim off the ends (I use a power miter saw because I’m lazy), and sand the entire tube with the orbital sander of choice in long smooth strokes while turning frequently. This usually goes quick since the nylons provide a nice smooth finish by themselves.
Well that’s it, this method may not be to everybody’s taste but it’s worked for me for years on a lot of rockets from ‘G’ power level up to full ‘L’ (I couldn’t find big enough nylons for 7.6” tubing).
Tracy “Woody” Wood - TRA#4828 L3
PS - If you don’t care for filling spirals on tubing but don’t feel your rocket needs the extra strength of Fiberglassing just pull a leg of nylons down over the tube with no fiberglass cloth underneath and epoxy coat the same as above (after sanding on paper tube). It will add some strength with minimal weight gain on the finished rocket and fills those nasty spiral marks.