I've been checking out the Klingspor site prior to ordering sanding disks. The site lists type PS22,PS23,PS31 and PS33 disks in the size and hole pattern I need. The PS 23 and 31 are "open coat" disks which I've heard are good. The PS33 is "stearate" coated, which is supposed to prevent clogging. The PS 22 and 23 use heavy paper (E and F, respectively) vs. the light paper (B and C) on the PS 31 and 33.

Which type of disks are best for boat building applications?

Are there any sources that are cheaper than buying direct from Klinspor? Someone suggested www.woodysworkshop.com. The prices are better, but they don't give details about the products they sell.