Hey guys. Been fixing surfboards for a while at an amateur level.
I bought unwaxed and waxed polyester resin from fiberglass warehouse (first time using their product). I am redoing an old longboard after repainting. Glassed with 4 ounce then painted on a coat (hot coat)of waxed resin.
When sanding, I’m getting immediate wax residue on sand paper and even blackish wax ring marks that appear after sanding. I’m using a Milwaukee adjustable speed 8 in polisher/sander.
Questions:
What is happening here? Is there too much styrene/wax?
Am I sanding too hot, should I reduce to lowest speed? What number do pros sand on the Milwaukee?
Is the hot coat not setting right ? I’m in Cali and i set it off with catalyst in 70 plus degree weather under direct sun.
It’s taken me forever to sand this board with a lot of paper changes due to wax on paper, any help is appreciated here
The shiny/waxy/black streaks are usually uncured resin, surf wax, or possibly too much styrene/wax.
I’ve had this happen a few times, I don’t bother with any sanding. I go right back and cover it with another hot coat. If I really want to be sure of no f-ups (or in a hurry) I use Suncure (with wax in there). Once it cures everything is easy to sand.
You never mention what grit you’re using. I usually sand laminations around 1000 with 40/60 grit. Same speed for hot coats with 220 if it’s epoxy/320 if poly.
On the hot coat, I was using 180 at about 1000 to 1500. I assume that is between one and two on the dial setting. I usually move up to 220 to 320 plus from there. Is it also possible to sand hard / hot enough that it heats that top wax layer That it becomes a very hard sticky substance? It all just gummed Up and became very difficult to sand. I did have The laminating coat Sitting outside for two weeks before applying the hot coat and maybe the elements effected curing? I did sand it slightly before applying the hot coat to clean it off.
Prior I would use a 5 inch orbital sander, which I assume is running at lower RPMs than the Milwaukee polisher sander.
I ended up sanding it as best as I could, acetone to clean wax seemed to make things worse.
Tried to refurbish destroyed board and it felt like a much harder project then shaping and glassing a new board.
Yes, refurbishing is harder than doing it new; but also cheaper. It now sounds like you didn’t add enough catalyst, which again can be fixed with another hot coat.
The acetone making things worse was probably because it was eating away at your uncured resin.
Yeah gummy hot coat is usually semi uncured resin, also high speed sanding will gummify da shits. So either a hotter hotcoat. So today in San Diego with 90+ weather I would put 20 cc in 32 oz resin for a hot coat. For lam I’d put 10 cc in 32 oz.
The hotcoat at 20 cc’s and 32 oz will give you about 5-8 mins of max work time. Pour the stuff out, cross strokes it 2x, tip out 2 times…and walk away…just walk away…I repeat …WALK AWAY. This whole process should take 30 secs to 2 mins depending on board size. If the hot coat takes longer than that to kick, or you keep fussing with it… you will get the slab off. aka stick shitz.
The goal here is the have a perfect thickness hotcoat, no air movement in room, and a perfectly waxy surface hard as rock surface. If you have sticky spots, put a peice of wax paper over the sticky area to kill off the air to it, it will harden up in a few hrs to a day.
