Next I've applied the caps at either end of what will be the box-section supporting the payload between the pontoons. I've popped one of the weights I use regularly* to secure it temporarily, and driven bamboo skewers into the top end to do much the same. I understand that tornadoes are able to drive stalks of grass into trunks of trees, but in the absence of a tornado I've used a bradawl to get us started here.
Next I've applied adhesive to the innermost joints, and smoothed them into a filet with a knife from the cutlery draw. We shall do the same to outside joints once the assembly is complete, and in either case it binds nicely to the substrate applied to the sheet of foam... which is after all the idea, it having being developed as the go-to means of sticking ceramic tiles to walls.
Incidentally if you are sceptical about this as a practical means of joining parts like this, consider that the trendy new ways of building fast boats that US special forces use ~ built from HDPE ~ are joined by applying the same plastic from a hot gun to form a weld. It has the advantage of speed, but then again there are foamed plastic adhesives which are good to go inside an hour or two if circs require.
Ed. insert 'to keep the fire-door open' as appropriate.
