Having struggled through four boards and doing lots of ding repair I am beginning to better understand the sanding process, but truth be told I surecouldn’t write the book on it.
Can we put together a step by step progressive guide with grit and pad choices taking this procedure from fill coats to final polishing?
I know everyone does things a little differently, so we’re all bound to learn something.
I’ll begin the run down by saying that starting the sanding process with 60 grit seems to be the way to go. Working the rails by hand with diagonal strokes off the deck and more lightly off the bottom going from a hard block to a padded block works well for me. Paying very close attention to holidays and not digging low spots is the key to producing a fair surface quickly. Feathering each stoke makes things go most efficiently.
I grind the bottom lap w/ 60 before i hotcoat the bottom. this helps with final sanding - its alreay smooth and deadly and very unlikely to sand into any weave.
I use 100 on a medium pad to do most of the sanding.
180 on a soft pad for the rails.
then fold the used 100 and hand sand the rails to finish them off.
if glossing - some hand sanding with 60 or 80 on your shaping block can get the surface free of warbles - i do this sometimes so the gloss will be really level.
if a gloss coat:
use dry 320 (medium pad) to sand down zits and sags from the gloss. using it dry, you can see through the dust when the surfcae becomes even. if the gloss is really bad, i will use 150/220 (soft) before the 320. then 400/600 wet (soft pad). then 3M heavy duty rubbing compound on a wool bonnet at higher RPMs. sometimes use a finer 3M polishing compound after that. shiny!
if no gloss:
use 150/220 on soft pad then spray it, finish with a scotch brite. if no spray, use 320/400 and its good. higher RPMs with a soft pad at about 400 grit can hide any exposed weave pretty well (but not as good as a spraycoat!)
i sand at the lowest setting on my sander (maybe 1,000 rpms)and turn it up when doing the final shine up.
I use 80 , 120 . 240 on a normal job and go down to 400, 600.1200 for a gloss . I do alot of short boards that are protec so I don’t gloss much. I use a hard pad and a soft pad and sand some of the rails by hand.
thing about sanding, it’s all in the pads. Hard pads for the flats, Medium pad for the deck, and a super soft pad for the rails. I use 100 grit for all my sanding. If you surform the lamination coat deck laps real flat, 100 grit on a grinder will flatten out a board real quick.
I’ve found out that bumpy laminations and big grits like 60, will tend to tear at the glass and not cut the glass. So you end up with destroyed weave that doesn’t absorb the glossed properly. It’s all in the prep between the lam and hot coat. If done right 100 grit will flatten out the board, and give a good surface for the gloss to grip too. 2 or 3 grinders with the right pads, all with 100 grit. Fast speed on the deck, slow speed on the rails. Stay over the top of the grinder, and keep it flat to the surface, just like a planer.
The finish on gloss. If you strain it, and put it on with a real good clean brush, All I do 320 grit the rail seam line, and polish out with wet paper starting at 600, 800, 1200. I use a 1 1/2 thick soft foam pad on a hard backer pad that I wet sand with on my grinder. Use a GFI inline extension coard, sealed in a water tight bucket. (make sure its grounded, It will save you life. If you don’t do this, don’t machine wet sand. Be warned, you will die!), I put a plastic apron on start polishing, My water source is two ways, if its sunny out I just use a hose, if its cold I use a a 3 gallon garden sprayer. Add a few drops of dish detergent in the water and you’ll have the board polished out real quick, and it will be real shiney. Finish polish with 3M polishing thats made for a highspeed polisher. done
I’d suppose so, but I’m still a caveman polyman. I don’t work with epoxy much, unless it’s used for glueing granite rocks together. I’m going to make a eps/balsa/epoxy board, I promise.
I would suppose with epoxy being harder than poly, you would have to work the grits harder to get the swirls out.
Epoxy is really hard to sand…the bright side is that it tends to lay flat anyways so not much sanding is needed. the guy who i bought my EPS blank from said go 80 110 220 for final (light) sanding.
I do most of my sanding with 100grit on a med/hard pad, then 120 frecut on a soft pad, 240 frecut then spray with 2 pac gloss. Use sanding block on rails. have to be careful not to dig in with hard pad though. The 2 pac can be sanded wth 800 w&d then 1200 then fast cut compound and finally fine polish. I can’t get RR epoxy so don’t ever bother trying to get a shine on epoxy