I have a wood model coated in epoxy over .75 oz glass cloth. I have kept the epoxy thin and have applied several coats to this point.
My problem is that I have sanded through the epoxy and glass in a couple of small areas. I know I have to fix this before paint or the sanded through spots will always show.
Do I use a bit of fiberglass cloth over the bare spot before adding more resin? I have one spot that I have tried to cover several times now and it seems to keep coming back.
I was told by someone long ago that the cloth was to determine the amount of resin left behind after scraping the excess off , so it would make sense that I might have removed too much material.
I thought I'd ask before spending too much more time on it. Internet searches all seem to be about furniture. I haven't found anything on epoxy coating balsa.
John

John

If you sand through the same area each time I guess it’s higher than the surrounding area. Generally if you go through in spots you just use resin to seal that area again. You are looking for a uniform surface level.
Adding in cloth will never work as you can’t feather the edges, can you post pictures?

Dave

Theres different way to approach fibreglassing surfaces, I only put enough epoxy so the cloth stick to the surface, and used high build primer (2 part automotive) to fill the cloth….it end up lighter and for me a much better finish does take a few applications and sanding in between…..way way easier to sand smooth…but maybe a little more labour intensive…

The problem was not so much that there were high spots, but that I was a little uneven on the pressure I applied while sanding. I also use a palm sander to speed the sanding process and I was a little careless in these spots. The bald spots are fairly small and hard to see, but I know from previous experience that these spots will show through the paint if not repaired. There are two to the right in the picture, and one to the left near the edge.
I guess I could seal the spots with some polyurathane for painting pruposes.
John

John

Just neat resin, brush in a coat, light sanding and then a second coat. sand that to finish

Dave

Dave,
Thanks. I'll try that.
John

As large and plentiful as those spots are, i would just reglass it.

Hello John,

You may find that resin only will probably not be the best long term solution as the balsa weave will most likely show through over time. In addition to applying a light layer of .6 to .75 glass cloth with quality laminating resin to the affected areas as suggested by others, I would also generously apply a lightweight "hi-fill" to the entire surface (brushed/dabbed on) after glassing. Let the hi-fill cure completely, and then sand back using a rigid sanding block. This method will avoid the issues of sanding through the glass into the wood, etc. You will then be left with a perfectly flat surface ready for priming.

Best Regards, Frank

so many way to fix this problem , makes flat first and what I do im using thin CA . clean the spot with alcool and lay you cloth and gently apply the thin CA , dont touch with hand of course, use a plastic bag, . dont use Kicker .when dry send and fill the wave ..