Billby, the 50kg weight for the PT is platform only. The all up boat would be approx 65kg (I was corrected on this in a earlier thread).

Wouter, I can't help but think you are playing word games. The only person who has mentioned a 30kg boat is you. we're all talking around 45-55kg depending on what THE ACTUAL BOATS COME OUT AT.

Since I know you like numbers here are some.

3mm Gaboon DS12 kit 12kg (includes hull skins, bulkheads and longitudinal ring frame)

4mm Gaboon DS12 kit 15kg.

Note. this kit has been designed for easy almost "measurement free" construction and at least 2 kg could be cut out of it if you were looking to save weight.

Weight of glass/ resin / bog in DS 12 approx 4-5kg (much of this could be eliminated but has been included to make the boat more robust)

Carbon mast like Gatos 6kg rigged (his number not mine)

Aluminium mast rigged 6-7kg rigged (depending on selected section)

Weight of beams 4kg

etc etc.

Even the 4mm boat shouldn't come out at much over 50kg.

Rather than theorising build a boat and see where you come out. If you need a hand send me your geometry and I'll generate some cutfiles for you.