Here's the raw material, from a single sheet of which I made a a deck, a keel and a pair of outriggers for stability during powered testing. If you look carefully you will see that it reads XPS Insulation NoMorePly 20mm 1200x600x20, doesn't it children?
Turning to our textbook we remind ourselves XPS stands for extruded poly-styrene. It is basically one up from the shitty stuff they use in bean-bags, and still too soft to drive a screw into; although you may have used a bean-bag to assist such purposes in your youth.
Accordingly although we need no more ply, as it says on the tin, we do need means with which to attach the spars. Here these have gone back to a lateral variety unlike the longitudinal spars that proved better on the 3rd prototype, incidentally.
Tune in to the next post now to see how this is best done...
