Sanding too smooth?

[Patricks Dad]

I have long held a theory that sanding to a finer grit is better than not. I've always taken pride in getting to a very smooth surface on anything I've built. Building canoes has been no exception. My wife calls me "Randy, Randy over-sandy”.

But as I glassed the inside of my Freedom Solo on Sunday it struck me that it may be true that you can in fact sand the hull to be too smooth.

I've always read accounts of people sanding with 80 grit and then finish sanding to 120 (or similar numbers). I worried that 80 grit was too aggressive and worried about taking too much off the hull. I've always started finer and ended finer (this hull was sanded to 220 but I've probably sanded even finer on earlier hulls).

I've had no problems with epoxy soaking into the hull or anything like that, but as I was using the squeegee on the hull and the glass was sliding around more than I'd like, it occurred to me that maybe if the hull was sanded to a coarser grit, it might have stayed in place better. I found that the inside of the shoulder chine required lots of attention to avoid pulling the glass away from that inside corner (which I softened from the original design). Perhaps if the wood had been more rough, it might have not moved around so much.

Thoughts?

[Moonman]

Hi Randy,

I think I agree with your premise but would have to try different sanding schedules on multiple hulls to know for sure. Maybe someone how has done it differently on several hulls will chime in. One thing though is I think sanding heavily on the inside may be overkill if you are only doing one coat of epoxy (for a lighter hull, rougher finish). To my mind, a lighter sanding and one epoxy coat on the inside is a win win.

Moonman.

[vann evans]

I would think that the major problem of not sanding enough would be that the fiberglass would stick to a rougher hull and perhaps create runs in the material if it was moved around while trying to position it or apply epoxy. Most of the glass weaves are fairly tempermental about splinters or rough textures. Certainly, 220 would not create problems like this. I remember sanding my hull to 100 and I didn't have any problems or thinking it was too slick or too rough.

Vann Evans

[Denis]

I used to sand just to 120 grit and thought that was fine but last 3 boats i went to 180 grit and result is a much clearer cedar finish with no problems of epoxy glass adhesion.

I always thought stopping at 120 kinda left a muddy or blurry look if you kmow what I mean lol

Denis

[Rick]

Randy

I was using the squeegee on the hull and the glass was sliding around more than I'd like...

On the inside of the hull, any excess epoxy may be flowing down and pooling up at the bottom and that may be causing the sliding (fiberglass may be floating a little).

Fiberglassing the outside, excess epoxy can drip off the edges onto the floor and there is closer contact so the fiberglass sticks more tightly to the sanded hull.

Just a theory, good luck.

[Patricks Dad]

Rick, the areas where I was having the most problem with the glass sliding wasn't at the bottom but closer to the sheer line (in particular the underside of that shoulder chine on the Freedom Solo design). But your theory about floating epoxy may apply in some cases.

thanks