[Rokeby]

Neil,

You got me. I've never done any full size prototyping. I forgot where you're coming from; low cost short term validation of concept. I'd guess you'll be going for less than near-perfect curves and smoothness. Thoroughly understandable, but not an option in my typical buyer expectation driven experience. (There is a truism among boat builders that goes, 'Finish is the modern substitute for build quality.')

I've never used anything other than 'glass/resin for covering purposes. However, I do know that when sanding wood glue you have to be mindful of heating the glue due friction. It causes the glue to soften and roll off in balls. The surface is not smooth. This can be minimized by using abrasives with a built in release agent evidenced by some overall color; typically white, green, or yellow, not the sandy color of the typical craft/shop grade 'sand paper." The little rolly-ball phenomena can also occur with just too much sanding dust between the abrasive and work surface. Use light pressure, and clean the loose sanding dust from the abrasive and work surfaces by frequent blowing/wiping.

I'd guess that you'll be finishing up with waterbased vinyl paint. Good enough. It may be overkill, but a final clear topcoat would add shine/depth/luster.

So, for you, never mind my earlier post, although I hope it has some applicability for other readers.

I'm not aware of a flexible platen pneumatic long board. I think it would lead to rapid heat build up and friction between the moving platen holding the abrasive sheet and body of the tool. It's been quite some years since I bought a new one… like any pneumatic tool -- they are built for commercial, continuous use applications -- they last and last if you remember to squirt a small amount of pneumatic tool lube into the air supply fitting before each use.

A user work-around for a flexible platen might be to attach a somewhat soft foam pad between abrasive and platten. i would think something about the density of those puzzle piece edged shop/playroom flooring squares would be a good start.

[Edit] As a final point; once your baby has a hard external surface you should consider adding padding on perimeter sharp edges. This to prevent unsightly and sometimes not easily repaired dings, the ubiquitous 'shop rash,' as you focus on other matters. Folded strips of the puzzle piece edged shop/playroom flooring squares would do just fine. This stuff is relatively cheap. IIRC, comes in 6 or 8, 2 ft. x 2ft. piece packs at Home Despot,etc. It is also very useful when applied on hard hand sanding blocks used for smoothing as opposed to shaping purposes.