On my first board, after the hotcoat, there was a little ridge at the lapline on the bottom of the board. I’m about to hotcoat the bottom of my second, and allthough it seems like i’ve sanded plenty, i still can’t get the lap fully flush with the board. I brushed on a cheater coat thinking it would fix it, but still no.
How flush does it have to be clean and flush? Do i need to sand more? it seems like if i sand anymore ill just be getting into the weave- is that ok?
Maybe someone could post a pic of a nice sanded lapline?
Before I hotcoat the bottom, I hit the lap line hard with an 80 grit block… fair it out so you can barely feel it with your fingers. Then, when I put my patch(es) down on the bottom for plugs/boxes, I take some leftover resin and baste the lap line… just pour out a stream of resin right on the sanded lap edge, then take a small spreader and run it around the board so the coats the edge and an inch or two on either side. When the patches cure solid, I fair them out, and sand down the basted resin smooth, again, using the block.
I use 4oz cloth for the patches, so fairing their edges is easy, and the hotcoat alone seems to take car of that. But because I use 6 oz on decks, that lap needs the extra love.
I had this problem my first couple of boards. Soulstices advice is what most will say. Also, if you are going to do this on the first lap (deck side), i would baste past the cutlap line as to protect the foam when getting that border flush. The baste will also help fill in that edge a bit.
looking back, I’d tape off the foam before grinding down the lap . . . also I grind it down, then sand it so its flush. I feel and if it has a bump, sand it. When my fingers ride across w/out that bump, its good.
Howzit FlatSpell, Your sand paper is not up to par, Norton is not the best. I use Hermes and it never leaves any grit on the lammed surface. I also use my grinder to take down the laps and all that happens is the paper gums ( no yellowing ) up because I'm sanding lam resin,this is why I use left over paper from preious board sandig. Aloha,Kokua
If you grind/sand down the lap on a tinted board, then you will not get that “clean cut” look right?..How do they do that, just add another layer of 4oz. over the top and bottom after it is all lam’d?
Howzit tenover, One trick is to styrene the sanded area just before you hot coat the bottom. Open the can of styrene and use a brush to coat the laps and any sanded areas with the stryrene and hot coat before the styrene dries to much,gets rid of the sanding marks.Aloha,Kokua
One neat trick is to contact Keith Melville and buy one of his files. Use it to prep the first lap before glassing the other side. Gene Cooper posted here once about using a roller tool to compress the lap into the foam a little before glassing the other side. Either way will give you less of a ridge to deal with.
Those type of file are fantastic also for smoothing out all the curves when you make fibreglass fins. they work more like a plane and don’t clog. I also have some that have areas of rasp like teeth between the other areas of curved ‘edges’ which really take off material fast. Also some ones with semicircle cross-section for curves. We used to use them for filing (planing) down aluminium sculptures. Very satisfying to use.
huh, i thought the same thing when the sandpaper stuck so i checked and i had bought 3M. Which i figured was sufficient enough. I’ll have to check next time i’m at the store.
I’ve had problems with the grit using Norton and 3M… maybe it’s something to do with temp/humidity, how much catalyst/resin ratios used in the lam, etc.
I actually ended up using my sander @2800 RPM and a 50 grit grinding disk to do the laps and it came out pretty nice. Much quicker than sanding it by hand.
Some guys do add a layer of 4oz. over the deck and then hotcoat both sides. The idea is that on a tinted, opaque or tiger stripe lamination you will be less likly to sand thru your color. If you burn thru the 4oz. a little so what. Basting you laps on colored lams is always a good idea. Use either or both of these steps and lightly grind your laps after each lay-up and you should be fine. I use an angle die grinder with diskit grinding discs, which is pretty much industry standard. I don’t have to hand sand or file anything with this set up.
I use Norton champaigne paper and never have any problems with grit. It is also less likly to gum up. When I can’t get it ,I buy that green paper that Lowes sells(the brand name escapes me). Also very good. I actually like both of these better than that white paper Fiberglass Hawaii sells. Just personal preferance. Any time you use sandpaper on lam resin there is the potential for problems. Sanding on lam resin with a sander and paper excessively will almost guarantee yellowing in the sanded areas of the lam.
