How did you apply the fiberglass?
Consider something like this:
--- Method 1 ---
Thoroughly mix and paint on a thin layer of laminating resin on your initial tube. Let it partially cure, so it becomes tacky. That is critical to this type of method. Also make sure the laminating resin you use does become decently tacky. Not all do!
Lay out your fabric; brush the weave out all nice and neat. Yes, most never think about that step. But it is part of the process. Wavy on the table goes wavy on the part. It looks unprofessional and may be weaker.
Lay the mandrel carefully right near the edge of the fabric; it will now tack on. Start to roll the mandrel carefully on the fabric. When it has lifted the edge of the fabric off the table, brush it down very gently, starting at the center, so you don't introduce waves (or strip out fibers!).
Roll at least half the way around and preferrably a bit more than that.
Iift the mandrel carefully and hang on your rotisserie. It should not lose the fabric!
Use a foam roller, the thinnest foam you can find. DAMPEN the roller with fresh batch of laminating resin. Roll that - gently - on the outside of the fabric that is already on the mandrel almost to the point where the fabric comes off the mandrel.
Roll the rotisserie a little bit; roll on a little laminating resin. Repeat until done. The fabric should not be wet per-se at any point. It should be enough epoxy for the fabric to go transparent (fiberglass) but not really more than that.
Gently roll a little more laminating resin on the outside of the tube if it looks too dry (learning curve here).
Now wrap the tube with whatever compressive method you choose to use. Let it room-temp cure, then post-cure.
--- Method 2 ---
DIY pre-preg!
Lay out a sheet of painters plastic. Tape the perimeter down so it stays flat. Wax the plastic. Don't polish off all the wax, just shine it. Too much pressure removes the wax. Waiting for the wax to dry before buffing is way too long. Best to use a mold release wax, but carnuba based car wax works. I've not waxed painters plastic so I don't know how hard that would be in practice, or whether there is a wax solvent / plastic compatibility issue. I'd try it on some scrap and see if it can be done. It would be better to be waxed. It might not be necessary though.
And there are probably other materials that would be more suitable. But that drop plastic is cheap, large, and readily available.
Roll on a layer of laminating resin. It will bead up; that is fine.
Lay your dry fabric on top. Roll it down, center to outside, following the directions of the fibers, with a DRY roller. You will probably want a helper or control of the dry fabric may prove difficult!
Now dampen the roller and complete wetout of the fabric. Again, center to outside, along the direction of the fibers. You don't want the fabric "wet". For fiberglass, you want it transparent. You also really really don't want it too dry! Learning curve...
For some fabric types such as Kevlar and Carbon Fiber, it is useful to use a wallpaper seam roller and go over all the fabric to make sure it is compacted and fully wet out. Roll only along fiber directions, again, center to outside. If you ever go outside to center you'll immediately know why that is a bad idea! You've been warned!
Now lay another sheet of plastic over the fabric, carefully, trying not to trap air bubbles. Roll it down somewhat gently with the wallpaper seam roller - AFTER you've cleaned off the epoxy!
Now keep a sample of the epoxy out, rolled thin, onto something. Wait until it is in the tacky stage. Once that happens, roll your supply of DIY pre-preg up on some tube (or keep as sheets) and put in the freezer (or possibly fridge if you are working pretty soon). You want to cool it down quickly, halting the curing process.
When you are ready to do the layup, you can pull the sheets out, even mark on them with a sharpie, cut out patterns, etc. Peel off one layer of plastic, and put the sticky sheet onto the part you are making. Carefully remove the other sheet.
Sometimes the sheet might come off cleaner and easier if it is ripped off rather than pulled off. Test on some scrap before starting with your actual layup.
Since this is a tube you are making, around a mandrel, wrap with heat shrink ribbon at least 50% overlap, and a bit of tension. You want to compact the layup.
Put the tube and mandrel in a hot box. Etc.
Gerald
