The centre-deck is assembled using the self-same techniques, and in this case foam sheet is applied to the underside. The format of the foam panel is identical to that in the pontoons and between them they displace sixty pounds (27 kilos). This is easily calculated in metric viz. 42 x 87 x 2.54 cm or 9,281 cubic centimetres apiece. No, it's not going to be the world's largest cruise-liner but yes, it's expected to float.
N.B. in the scheme of things each of those spars is supposed to be identical in length at three feet. One reason for a re-build at a slightly reduced size ~ aside from material constraints ~ is that it can then be toted on the roof of the car instead of trailered. On the vehicle in question the distance between the roof-rails is three feet, so the overall width of the craft has to be just that. In view of the fact that the hydroskis overhang the pontoons by an inch and a half, the net effect of this is that the cross-spars have been reduced by around five inches.
