How many layers of glass is "too many"?

I'm going to be using wraps of fiberglass as a sort of "centering ring" - not for the motor mount, though; I just need to build up a tube so that another fits snugly.

If my calculations are right, 3-4 wraps of 9 oz glass will be about right. As long as I'm diligent about removing air bubbles, is there any reason not to do all of the layers in one fell swoop? I.e. paint the tube with epoxy, wrap with glass, smooth out, repeat until all the layers are there, let cure.

so more specifically: I have a 3d printed transition that is loose. Glass would tighten it up. It's not a structural piece so this doesn't have to be super strong - it's literally just a sleeve that will fit over a tube. Now I'm thinking ... I could probably just use masking tape to locate it then epoxy it in place....cheaper/quicker/lighter than fiberglass....

ActingLikeAKid said:

so more specifically: I have a 3d printed transition that is loose. Glass would tighten it up. It's not a structural piece so this doesn't have to be super strong - it's literally just a sleeve that will fit over a tube. Now I'm thinking ... I could probably just use masking tape to locate it then epoxy it in place....cheaper/quicker/lighter than fiberglass....

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Here's what I do when I need to build up a tube evenly. I wrap rings of tape around the tube in two or three locations with an inch or so between them. Then I screed silica thickened fast epoxy between them, using the tape to guide the edge of a drywall tape knife. Before that epoxy completely cures I remove the tape. Once the epoxy cures, but within 12 hours or so I come back and screed thickened fast epoxy between the built up rings I just made.

To answer your initial question, 3 or 4 wraps of glass should not present any problem at all. I have made repair layups on aircraft that were several times thicker. In thick layups, thermal runaway can be an issue as the resin warms during the curing process but that is a bit of an extreme situation in my experience.

I would think that you need to be mindful of weight. Will you have to add extra nose weight to compensate the CG as well?. I have used masking tape saturated with CA (do it outside and stand up wind) in similar situations (though on balsa) with good results. All depend on what you are building.....

Why not reprint the transition to the correct dimension? I am of course assuming you printed the part in the first place.

I've made tubes from 4 wraps of 9oz glass. I did it in one continuous piece. Just need to squeeze out all the excess epoxy and bubbles.

why not blue tape? you don't need glass...

ActingLikeAKid said:

so more specifically: I have a 3d printed transition that is loose. Glass would tighten it up. It's not a structural piece so this doesn't have to be super strong - it's literally just a sleeve that will fit over a tube. Now I'm thinking ... I could probably just use masking tape to locate it then epoxy it in place....cheaper/quicker/lighter than fiberglass....

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Can you just print a few small rings the correct thickness and bond them to the transition?

First of all, I would not use epoxy for the build up for a friction fit.
Use fiberglass resin. Just my experienced :2:

Will epoxy stick to the plastic the part is made from? My only concern would be build up of heat as the epoxy cures. I'm a bit more frugal. I've done similar build ups using Gorilla glue and wraps of paper. Very tough stuff.

sooner.boomer said:

Will epoxy stick to the plastic the part is made from? My only concern would be build up of heat as the epoxy cures. I'm a bit more frugal. I've done similar build ups using Gorilla glue and wraps of paper. Very tough stuff.

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Very much depends on what plastic & which epoxy. Mix up an ultrs-small batch and test a single drop on an edge or other easily-sanded area?