by TimC » Wed Mar 08, 2023 11:38 am
Similar to Pat's experience on my two PMF builds. One is from 2016, the other from 2020.
2016 version was PMF over ply. I liberally applied 50/50 TBII to the plywood. Had help applying the canvas and then brushed the canvas all over with a wallpaper smoothing brush. Then immediately applied another liberal coat of 50/50 TBII. Did a light brush of the wallpaper brush again. When that layer coat was tacky I applied another coat of 50/50. Of course inspect throughout and brush where needed. After that I applied more coats at 75/25 TBII until I thought the texture would show with several coats of paint. There are now about seven light coats of exterior latex house paint. First coats were "opps" paint at about five or ten bucks a gallon. Random finish (matte, semi-gloss mixed). Last three coats are semi-gloss exterior. I repainted last summer because I wasn't in love with the color. Other than a good cleaning and a quick light sanding with a hand sander and finish cleaning I just added the new color. No lifting, no bubbles, looks good as new. Full disclosure, there were few vertical surfaces. Just the roof front and hatch back. Hatch was PMF'd on a bench.
2020 version (my son's) was PMF over rigid foam. Before PMF I took an old ratty wire brush and scratched the entire surface of the foam. Wiped it down to eliminate dust and applied TBII. The first three applications of TBII happened before the previous coat was dry, thoroughly saturating the canvas. Then "opps" paint and finish coats of semi-gloss. A small number of bubbles showed up prior to painting on vertical surfaces and I attribute that working too quickly on a hot, 85 degree day. With a syringe we applied more TBII and clamped the surface. That was easy to do since we had not painted yet and a little spackle filled the screw holes necessary for the clamping technique.
I'm a PMF fan and though I have built a couple boats using epoxy/fiberglass I prefer PMF. I might even build a PMF boat if it didn't live in the water. Oh wait, that's just crazy talk!
Used 10oz canvas from bigduckcanvas.com on version 2020. Reasonably priced, no defects, no seams and available in 64" widths at that time. I used Menards 8oz paint drop cloth canvas on version 2016. Seam was in a good location and was able to cut the width in half to eliminate it.
Tim