varnish over epoxy

[casem]

I've got some epoxy coated plywood (okoume) on my boat that I want to varnish over. How fine should I sand it before I apply the first coat of varnish? I was thinking of going 80, 100, and then 150 (with a random orbit sander).

[dasboat]

150 should be pleanty.get the first 2 coats on after that,then you can wet sand with 220 and start your final coats.
Das

[casem]

Do you think the jump from 100 to 150 is too much? I can't find 120 to fit my sander, but I want to make sure I get the scratches out from the 100.

[Bruce Taylor]

I'd use 150 and take a few extra passes -- and change the disc a bit more frequently.

[dasboat]

Casem,like Bruce,I would start with 150.Alum.oxide open coat ought to do you fine.
Das

[Concordia41]

As you're probably aware, sandpaper brands vary dramatically by brand and even by type (disks vs. sheets, silicon carbide vs. aluminum oxide, etc.) I've got some Norton low end stuff that I bought at the Orange Store in a pinch that leaves so many deep scraches the work time is increased dramatically. The 3M gold is my favorite [see below]. 3M Gold Resinite 180 does an amazing job of cutting down but leaves few deep scratches that have to be reworked.

So anyway, the point is worry less about the number on the back of the sheet and just look for the result you need. If you're goal is to "varnish over" the epoxy, then you just need to scratch it up enough for the varnish to bond securely. Only if you're taking it down to bare wood would I start with 80 and work my way up through the grits.

BTW I know you're all tired of hearing me quote Rebecca Wittman, but she's doing product development for 3M and one of the things she said was that for oily hardwoods 3M gold was the best bet. The 3M silver, gold and new imperial (purple) were discussed and her preference was the gold fre-cut because, amoung other things, the paper backing on the gold has specific properties that retard curling in a moist environment, i.e. the boating world.

Works for me.

[Bruce Hooke]

I would second Concordia41 in saying that 80 grit sounds too course unless you have some very rough epoxy to deal with. I would start with 100 grit, or even higher if the coating is fairly smooth to start with (and go carefully because it is easy to take off too much). Also, rather than skipping 120 grit I would probably hand sand that grit since I think that will be quicker than trying to sand out 100 grit scratches with 150 grit paper.

P.S. What kind of sander do you have? I'm surprised you can't find 120 grit...

[casem]

Thanks for the replies. It turns out 80 is a bit too coarse so I'm using 100 on the sander, 120 by hand, and then 150 on the sander. That seems to be working okay. The sander is a 5" Porter Cable which I think is the only one with 5 holes so that makes it a little difficult to find paper (most of the others are 8 hole).

Thanks again,
Dan

[mike kelly]

while were on sandpaper. here something you might want to know aboat if you don't already.Klingspor (a sandpaper company) sells cut offs remnents from sanding belts.Its perfect pieces for doing brightwork. and cheap 24.95 for 20 pounds ,good quality as well.phone number is 1800-228-0000.they also have a web site that i havn't been to www.woodworkingshop.com (http://www.woodworkingshop.com) The paper i've been pleased with though