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