filling pinholes in epoxy resin / fiberglass

[fishrdan]

I 'm building a swim platform and found a bunch of pin holes in the epoxy/fiberglass that I need to fill/seal before priming and painting. What's going to be the best way to fill the pin holes?



I tried coating the pin holes with epoxy, but it didn't work as they just came back when I got to their level, they didn't get filled in, just covered up, epoxy too thick. Then I tried epoxy thinned with acetone, but found the same thing, the holes were not filled. It seems that the holes are being filled with sanding residue that I can't blow out with an air compressor, some of the holes clean out, but many of them remain filled with white sanding residue. I can dig some of fit out with a sharp tool, but it's not totally cleaning the pin holes. I have a feeling the sanding residue is sticking in the holes, like it's clogging the sand paper.

I was thinking of painting on some primer and scrubbing it in with my fingers (gloved), but not sure that will work since the holes are plugged with white sanding residue. :faint2:

Any ideas...?????

 

[GT1000000]

Re: filling pinholes in epoxy resin / fiberglass

You need to somehow blow out the residue...you can try some soapy water and blow it out...you can try solvent and blow it out...
Unfortunately, if the holes aren't clean, nothing will stick in them...
Once you get them clean, you can use a filler primer and a bondo squeegee to push it into the holes, you'll have to go in multiple directions to get them full and you might have to do it a couple of times to get them all filled, then sand and fair as usual, then paint...

 

[Bob_VT]

Re: filling pinholes in epoxy resin / fiberglass

Thicken the epoxy with cabosil and spread it with a squeegee.

 

[jigngrub]

Re: filling pinholes in epoxy resin / fiberglass

Epoxy sanding dust is filler, remove as much as you can and don't worry about the rest.

For open pin holes, the cabosil or SM fairing compound mixed with epoxy resin to a paste or mayonnaise consistency will fill and level itself when used with a skimming tool like the squeegee of bondo spreader.

I used a plastic wallpapering tool from Home Depot to spread resin and skim my SM fairing compound.

It's the black tool in the pic, spreads the material well and cleans up easy with mineral spirits. About $5 in the paint dept.

 

[fishrdan]

Re: filling pinholes in epoxy resin / fiberglass

You need to somehow blow out the residue...you can try some soapy water and blow it out...you can try solvent and blow it out...

Soap/water then acetone got most of the holes clean.

Thicken the epoxy with cabosil and spread it with a squeegee.

Good idea. I used some thick 30 minute epoxy as the slow epoxy from US composites takes for ever to cure 8 hour set 24 hour cure. I had 4 coats on the edges in a couple of hours and this morning it was cured out and ready to sand.

Epoxy sanding dust is filler, remove as much as you can and don't worry about the rest.

Yup, I didn't worry about the micro holes. All of my problems were on the edges, (top and bottom were perfect), so I couldn't use a sgueegee, though on the first coat I rubbed it in hard with my fingers (gloved), to force it into the holes.



I laid down 4 coats of thick 30 minute epoxy, about 1" inward top/bottom and on the edges, this gave my enough material to sand. After each coat I hit it with a heat gun on low, working over the whole thing 3 times (top edge, edge, bottom edge) to pop all the bubbles that came from mixing and brushing. When I sanded it this morning I only had 1-2 places with micro bubbles and everything else was all taken care of.

Sorry, no pics of the fixed bubbles as I just got done spraying it with primer. I kept telling myself to take a pic, (take a pic, take a pic, take a pic) but I didn't....

Well, time to go out and wet sand some primer :watermelon:

 

[pauloman]

Re: filling pinholes in epoxy resin / fiberglass

some pre thickened epoxies spread more evenly and smoother than others - especially self made thick epoxy. Most tend to pull and tug, like taffy - following the putty knife. The good ones spread 'nicely' like a hot knife through butter with not 'drag or pull'

paul