recommend a Guide Coat paint - under gelcoat?

[ktm_2000]

Hi All,

I am fast approaching the end of my construction of fiberglass components and will be working on fairing out under my gunnels and deck with the ultimate goal of finishing those areas with gelcoat.

I've seen a lot of folks spray what I think is just cheap auto based paint in zebra stripes to then long board sand to find high and low spots.

What is the best inexpensive paint to do that with?

thanks in advance

[CamB25]

I used a dry guide coat, 3M. https://shop.hamiltonmarine.com/product ... 22660.html

Worked very well.

Cam

[ktm_2000]

Hi Cam,

If there is a low spot, can you just put more filler in those areas and cover up the guide coat or do you need to clean that out first then add filler?

[neil]

Painting the boat last spring I found that adding liquid food coloring to denatured alcohol and wiping the whole surface down with a rag soaked in it was the best method for a guide coat. Use whatever color will contrast the highbuild/ primer and any low areas will stick out like a sore thumb, and you can put filler overtop of it no problem. Best of luck

[CamB25]

Well, you need to sand before applying more filler or primer, so I would sand all the guide coat off. I guess the approach depends on if you are spot filling, or doing another coat over the entire surface. You can block the high spots off, then mark the low spots for more filler.

If you are working with raw glass you will have 1001 pin holes to fill. Seems unavoidable. Fair out the raw glass with a skim coat of filler. Sand it "smooth". Fill the big surface irregularities with more filler, sand again. Repeat until you think you've got it. I used the guide for this part, too. Then spray a heavy coat of white primer. The pin holes in the glass will appear, like a bad dream. Run around the boat 10 times filling pin holes with filler. I used polyester filler - 3M marine filler. Once all your pin holes are filled, heavy sand everything and start your primer coats. spray/guide coat/block sand, repeat until satisfied, then paint. If you don't take care of the pin holes, they will show through the top coat. I have a couple I missed, of course!

That's basically the way I did it, but I was painting, not using gel coat. Might be different.