HI Guys
Do I have to lap the last layer on a shortboard? I keep on getting this horible little ridge on the hotcoat. I have tried to surform the last lap on the underside. But I just cant get it flat enough. I have also tried to sand it but the lam is still gummy and just ends up getting dirty. If you guys have any other tips let me know what they are.
Keep well
small disc grinder…take that edge right off.
Here is what I’ve been doing, and you don’t end up with any ridges or bumps. On the bottom lam, after you have tucked the laps under and the resin is mostly cured flip the board over and baste the edges of the lap with some lam resin, about 1/2 cup is plenty for a shortboard. You’re trying to build a bridge between the edge of the lap and the foam on the deck. This gives you something to sand into when you grind down the lap. When you do the deck lam, do it normally. Then, when you hotcoat the deck, don’t tape the rail line and after the deck is done, paint up under the rails to fill in the lap on the bottom. Then, when you hotcoat the bottom tape it off normally and you shouldn’t end up with a ridge or bump where the lap is. I wouldn’t reccomend not lapping the last layer because of strength issues.
I hope more people comment on this, but the answer is yes.
A lot of a boards structural integrity relies on the rail laps, top and bottom. I’ve seen many bent and broken boards that tried to save weight, time, whatever, by skimping on the laps, not really a good practice.
Sorry to state the obvious, but your ability to do the laps will improve with practice, removing excess, pulling the lap tight.
It’s good you are concerned about it, and in time these small problems will go away.
A small grinder is the trick. Any 4" grinder of decent quality will do, such as Makita, Ryobi, DeWalt, and Harbor Freight, etc. They will come with a round rubber pad used for screwing down a sand disk I use 80 or 100 grit.
There is something about the speed of the disk that keeps the resin from getting dirty. It may gum up over time, but not as fast as when you do it by hand.
Just grind down any high ridges before you hotcoat. Be careful to hold the disk as flat as possible and sort of brush across the high areas lightly. Too much fooling around and you’ll gouge. Doug
Another trick you could try is peel-ply. Just cut a few 2"-3" strips and use them to do along the lap. When cured, rip them off and it’s ready for the filler coat.
Only do this on glass to glass laps, the peel-ply will pull foam.