How to sand properly

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AsaBlanchard
Posts: 48
Joined: Mon Mar 29, 2010 10:10 pm
Location: Lexington, KY

How to sand properly

Post by AsaBlanchard »

Fellow Boat Buiilders,
A very good friend of mine makes electric guitars for the band Aerosmith. He came over to give me some pointers on sanding my canoe. I asked him how good they sanded guitars, and the answer was until they had achieved perfection. He explained to me, that once you had the grain of the wood covered with epoxy, it was no longer necessary to sand in the direction of the grain. Get two good cloths, one to clean the sand paper, one to clean the area you are sanding. Do not let the sand paper clog up with debris. Go buy good sandpaper from an auto body repair shop or paint supplier. 3M is the best. Sand in a circular motion, listen to the paper, feel the paper, when it is full, wipe it on the clean cloth, wipe the sanded area with the other cloth to clean the debris away, do not sand loose debris, sand a clean area. Do not rub so hard the paper builds up friction. Let the paper cut its way, clean the paper, clean the area sanded, keep moving, you will sand the hull in very little time building a smooth surface as you go. The color will tell you when it is even, like Ted Moores explains in his book.

This is the very best tip I learned building my canoe, you will sand until you get sick of sanding, but this really helped me understand what I was doing. I sanded it until I was sick of sanding it. And then sanded it again. I used a 2" x 3" foam sanding block with the appropriate sand paper wrapped around it. I did use a homemade sanding board that was 2 1/4 x 15" to cut the rough stuff and sand a "fair line". .
I did not use my random orbit sander on my hull after I got it epoxied, I did it by hand.
After two coats of varnish, I wet sanded with 320grit between coats two and three and 400 grit between coats three and four. Wet sanding is three times easier than dry sanding.

Hope this helps,
Asa
stovetop
Posts: 11
Joined: Fri Oct 27, 2006 9:19 am
Location: South Portland, ME

Post by stovetop »

Good tips Asa - I think that sanding is the least favorite part of woodworking for me, but a neccesary evil nonetheless! Cant wait to get to that part of the build myself :sleepy
One thing I use for my ROS is a "Sander Sitter" it allows you you to set down the sander while it is still running to strech your fingers, arms etc. It also cleans the paper via the crepe pad in it. Just remeber it will only clean your sandpaper, not make worn out paper good anymore. You also might want to consider attching it with velcro or setting it on a non slip mat, as I have chased my sander down the bench a few times :laughing
"I'm up, I'm dressed, what else do you want?
CatFaber
Posts: 20
Joined: Wed Nov 03, 2010 4:55 pm

Post by CatFaber »

Hmm. After epoxying I did practically all my sanding with my longboard--after I had worked so hard getting the hull fair I didn't want any lumps and bumps of epoxy spoiling that. Plus it was so easy to sand into the glass that I was really worried about sanding through it if I used power tools. AND because of the heat I might be starting at 7:00 am and I had qualms about running power tools in the driveway before 9:00. So I guess there were a lot of reasons that lined up here.

I used a wire brush to clean the sandpaper and the sandpaper really lasted pretty well that way.

I'll have to remember that about using a cloth to wipe off the dust--I used a whisk broom, but a cloth would be better both in terms of getting all the dust off and in terms of keeping epoxy dust out of the air, since in Tennessee it's often hot enough that a respirator and glasses just won't play nice with each other.
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Patricks Dad
Posts: 1476
Joined: Wed Oct 13, 2004 1:11 pm
Location: Warrenville, Illinois

Post by Patricks Dad »

In my prior builds, I have only hand-sanded the hull with a block of hardwood and sandpaper. It produces a completely smooth result. It has typically taken well over 20 hours (I try not to keep track - multiple days ot tedious, back-breaking work).

Last night, I started sanding a hull that I glassed last Sunday. I usually let a hull sit longer than 5 days (2 weeks to a month) but I picked up a block of wood and a piece of sandpaper and decided I'd see how "ready" it was. Two hours later, I had done a couple square feet. I was sanding with 100 grit paper. I picked up my ROS (with a 220 grit disk) and went over the area I had just finished to remove the scratches left by the 100 grit paper. Of course that worked fine. But then, I just kept going with the ROS. The epoxy was pretty fair to begin with as I was pretty careful when I glassed. I finished the entire hull by 11PM. The reward for care and attention when glassing was a savings of several days of sweat.

I took a hot shower at midnight to ensure all the dust was off my body (and just got out of bed 30 minutes ago!).

I have a vacuum hose that connects my ROS to my shop-vac. I wear a respirator whenever I sand epoxy (hand or ROS). Given a choice between glasses and a respirator, pick the respirator.... I ruined a pair of (plastic lens) glasses with epoxy a couple years ago so I never wear glasses when using it (my eyesight isn't too bad on close things...)
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