Fiberglass Removal And Repair

I know this sounds rather stupid but does anyone have any advice for repairing a "botched" fiberglass job? I just attempted my first fiberglassing job on a 5.5" "I-roc" and I have seveal sections that are not up to snuff that I'd like to redo.

Most of the problem areas are at the ends of the tubes and along the seam where the first layer overlaped. The first layer was a 6oz wrap of standard cloth with approximately a 1" over lap. The second layer a 2.4oz wrap of fine weave cloth with again about a 1" overlap.

The problems that I have seem to be related to the amount of epoxy resin I left on the tube. I wrapped the cloth around the tube after coating it heavily with epoxy. The tube had been prepared for fiberglassing by stripping the top, glassine, layer to expose the inner kraft tube. I then used a 3" paint roller to further saturate the fiberglass cloth with epoxy. When the entire tube had been coated I used a roll of toilet paper on a paint roller handle to remove the excess epoxy.

The epoxy I am using is very slow drying, about 5 to 6 hours to setup and 24 hours to completely dry. Apparently overnight the amount of epoxy in the fiberglass cloth decreased, probably by soaking into the kraft tube, and areas along the seam and the ends of the tube dried out.

I was wondering if I could cut out these areas or sand them down and then apply glass and epoxy "patches". Has anyone ever had to do this? If so how well did it work?

Ken Holloway, NAR #78336, L-1

Ken,

I am not the expert in this area but have some thoughts, some of which you probably already know.

Many fiberglass people recommend that you insert couplers, covered with a release agent (wax paper will do), on either end of a tube to avoid end-of-tube problems. You overlap the cloth over the couplers and then trim it after the epoxy is dry.

I guess your super slow dry epoxy drained out of the cloth? I have never had that problem on the few tubes I've done, but know a lot of people build 'rocket rotisseries' (spelling) to avoid the epoxy settling. These turn the tube at some slow rate. I can find a link if you are interested.

Any place the cloth wrap is not well wetted will not be as strong as the rest of the tube, but for most applications I personally don't think it matters much, except for very high performance rockets. Any repair will probably also be weaker. I think you could either trim the end of the tubes or scrape/sand the bad spots and fill them with epoxy filler, autobody glaze, or the like. I've known this to be done when fixing phenolic tubes, so I don't know why it wouldn't work for you too. These fillers will be easier to work than epoxy/glass patches.

The only time I did anything close to this is to fix a zipper. Some sanding, and then soaked the area in thin CA, and more sanding. After it was fixed I covered the end of the tube with a thin layer of glass and did my best to blend it back in.

I bet Carl and sandman will have ideas too. Good luck!

Dick,

Thanks for the advice. I'd only heard of using couplers for vacuum bagging before this. That may have been one of the problems.

As far as building a "rotisserie" it's something I'd considered but had been advised was not necessary. I used to use one years ago when I built custom fishing rods. The windings on the rod guides needed to be sealed with epoxy and by rotating the rod around it's axis you could get an absolutely glass like finish.

Again, many thanks for the help.

Ken

Ken, you are welcome...and may be right about the coupler tube idea coming from bagging. Still, sounds like it might not hurt. Good luck!

Originally posted by kgholloway
I know this sounds rather stupid but does anyone have any advice for repairing a "botched" fiberglass job?

[snip]
I was wondering if I could cut out these areas or sand them down and then apply glass and epoxy "patches". Has anyone ever had to do this? If so how well did it work?

Click to expand...

Ken,

Not stupid at all. It just takes practice. My first fiberglassing project was a real mess. Each one after that was markedly better.

Since it sounds like just the ends are a problem, it should be a easy fix. If the body is fine, then you accomplished what you probably wanted -- a tough airframe. On the ends, you can sand out the blemishes, or cut out larger lumps and bubbles with a hobby knife. I've used patches of just epoxy, but you could add a piece of cloth if desired. Prior to using rail buttons, I've even used 3/4 oz. patches over launch lugs, to give them a better anchor. The edges of the cloth feather out fine with a sander, and you'd never know they were there.

I'm assuming you have a palm sander or something equivalent. Sanding glassed tubes without a power sander is pretty grueling!

Lee,

I checked the tube last night and you're right. It's nice and stiff now and I think I can sand out the bad spots. If not I should be able to save at least the center section of the tube for a future project. Those 5.5" LOC tubes are not cheap and anything I can save will be towards the good.

Ken Holloway, NAR #78336, L-1