sanding epoxy

Hello-
I am back in the boat building mood after taking the holidays off, and have just spread a layer of epoxy/filler over balsa core. This was done to fill in the space between the balsa blocks as they went around the hull curve, as well as to prevent epoxy absorbtion into the core as I put glass on. My question is, how smooth should I sand this if putting 10 oz. glass cloth over it? I obviously would like a smooth surface Perhaps a better question would be: How rough of a surface can 10 oz. cloth tolerate without bumps showing through?
I did nock down any high spots while the epoxy was green, so I am in pretty good shape.
Thanks for your thoughts.
Rob

 

you should have filled the balsa ,and then placed the roving down while the putty was still wet, this way you dont have to sand

 

Your surface needs to be pretty close to the smoothness you desire from the cloth. Any humps or hollows will show through and you'll be filling again. Get it pretty fair then lay down your cloth. You'll fill the cloth weave anyway, so fill any slight imperfections then.

 

The epoxy absortion into the core is what makes it adhere.

 

FJ- I will do it that way next hull, with a few helpers around. I was happy to see that the filler/epoxy mix did it's job. (I had to prove it to myself on a large scale- not just the test samples)
PAR- hull is Fair, but there is a scattering of filler that is above balsa. I am at 80 grit, and it feels good, and dry cloth looks good on top of it. I'll probably long board it again to 120. I'm doing this for fun, and the exercise is good for me! Was wondering what grit you pros would consider taking it to.
Gonzo-I now have a good anchor into the balsa. I was impressed with balsa's ability to wick the epoxy out of my mix and leave the filler on my scraper! (403 well blended) Made me glad I did this step instead of just trying to lay glass on balsa. Any hints on glassing to dry epoxy? I will be sure there is no "blush".
Thanks again,
Rob

 

Give it a good tooth with some 40 grit, all over and you're as ready to go as you can be.

 

What kind of epoxy did you use? Any wax in it?

 

West epoxy with slow hardener, mixed with 403 filler. Tried thick consistency- peanut butter- at first, but found that a thinner mixture went on much better. I don't think there is wax in this, but i have seen it blush on occasion. I'm pretty comfortable with a good sanding giving me a workable surface.

 

It doesn't matter, blush or not (okay, well it does) it still is relying completely on a mechanical bond, so put lots of big scratches on the surface with some heavy grit.

 

40 grit for mechanical bond.

 

40 grit is a beautiful thing. I was afraid to let you guys know that I was being that "rough" on the project. I thought I might offend some of you true craftsmen!
Rob

 

24 grit is a beautiful thing, 36 is it's smaller, but still healthy brother, 40 is nice, 50 is getting there, 60 is the red headed step child, that everyone tries to peddle to home owners and other amateurs as material removal stuff, then we get into the progressively more lovely ladies of the group.

 

What I like...

16, 24, and 36 for the 4.5" grinder. 40 and 60 for the 6" DA sander.

 

Screw the DA, bring on the 13.4 amp 10". Use the DA when you are interested in a finish of some sort.

 

now thats sucking deisel