: I sanding my first boat, a Coho, in preparation for varnish. I know the
: objective is uniform, flat white matt. However, I am getting a mottled
: appearance in many areas,where the mottles are apparent low spots. I am
: using a random orbital with1 150 grit. Tried 100, it cuts too quick to the
: cloth for me. With the 150, I do get into the cloth here and there, but
: not bad, but if I keep sanding to get everything white, I start to hit
: more cloth than seems right.

: I tried a test path with varnish on a typical area, and for my purposes (need
: tobet out while the summer is still here,not too concerned about
: perfection_ the finish after even one coat looks great. My concern- will
: the varnish fleck ooff of those low spots that haven't been thoroughly
: roughened? Conversely, I am afraid exposing too much cloth is weakening
: the boat, and may look worse than those low spots. Hand sanding seems to
: be more effective for spot removal after machine sanding the bulk of it,
: but it is very slow going to get everything white.

: Is there something I am missing with the ROS? Fatter pad, different grit?
: Should I relax and varnish,or sand and sand, not worry about all that
: weave exposed?

: Thanks

Rod, the only thing that is missing is hand sanding. The RO pad is bigger than the panels so it's very easy to take epoxy down to the glass. Use the RO as you already have done, which sounds like enough. Go back with a hand sanding pad with the same grit in the direction of the panels. Where the panels narrow down smaller than the hand sanding pad, ease up and sand lightly or use a piece of folded up sandpaper. It shouldn't take more than an hour of gentle easy hand sanding to get the thing just right. Glass that has been cut into will be slightly visible so don't go sanding crazy, the idea is to sand it enough to varnish it not sand it to some theoretical uniform thickness.

Unlike paint varnish will be very tolerant of surface variations so don't worry too much.