I’ve just about finished my first board. Im at the stage where i need to be sanding down the fin boxes and the hot coat. Ive been using my stepdads orbital sander to get the fin boxes flush and for some reason this has smeared black colouring all over the board and it wont come off! From what i can see, the glue on the sandding disks is black underneith the grit and when the grit is gone its just mixing black glue with the resin. Basicaly the fin box area now looks like a marble cake!
If it helps im using clear reasin with no pigments and have not painted the board at all.
Doesany body know how i can avoid doing this on the rest of the board and / or remove it from the messed up bits.?
Yeah i went middle of the road… not cheap but not expensive. I waited about 2 days before sanding. Maybe i should buy some better stuff… Thanks for your help.
Its poly resin. Yeal ill try moving it round. As Oldskull said i might also just go splash out a little more. One of them things no one warns you about so it must not happen very often. Im hoping i can resolve it by just sanding it all off. Although i suppose aslong as it surfs some swirls wont really matter!
Confused here. The top of your first post says “epoxy sanding glassing”.
Then you say you’re using poly. Which is it?
Also, if the sander is a typical random orbital with velcro style pad to attach the paper, that black stuff you see isn’t from the sander.
My guess is you over brushed the sanding resin and it has sticky spots that never cured all the way. Gummy, dirty looking resin happens when you sand uncured poly with too light a grit and too high RPMS. Switch to a heavy grit on a block of wood and hand sand that gunk away. Throw a light cheater coat on the area and don’t brush it too thin or too much. Then go back to using the orbital.
Joe, you stated that you’re sanding the fin box and hotcoat. Did you by chance use laminating resin instead of sanding resin for hot coat? Or if you mix in the sanding solution (wax and styrene) separately, maybe forgot to add the solution to the lam resin?
Use a solvent to take off the black mess. Using a rag and some lacquer thinner; wipe the black residue off the board. Paint Thinner or DNA might do it, but most likely Lacquer Thinner will for sure. Then sand using a paper that will not leave residue. Recommendations would be Indasa, Norton White/Champaign or that new 3M Purple sticky back.
Dont over sand/grind the finbox when you are makin it level with the bottom of the board. Take away material slowly and with gaps in between to allow the plastic to cool off. If the finbox gets too hot the black dust could start to mess with your hotcoat, especially if it did not cure totally tack free. Heat can also potentially warp the finbox. Good luck!
Appologies the top said epoxy, but i diddnt actualy put that in manually? not sure how it got there. but its poly resin.
That sounds about right, i was a bit cautious about getting one big burn through for a board so i started on a 200 grit with high rpm. Ill go out nd get some lower grit stuff and do it by hand. Less room for error again i suppose.
Im completely new to this so im not 100% sure what kind of resin. looking at the cannister it doesnt say which kind… I had to mix in wax and styrene into the resin as advised for a hot coat i know that much!
I did think that, but was a bit cautious of the solvant effecting the resin, but i guess its cured now so it should be fine right? ill check out some of those better sand papers, thanks!
I definately noticed that, i could see the box closing off on the first one, luckily it was still hot and i could get rid! but yeah, its a thruster set up, and you can see where i started on the center and went left then right based on how well sanded they are haha. I guess i gradually realised the technique as i went on. Thats pretty noticeable on all of the stages. Maybe my second one will turn out better.