OK, so we've decided stiffer is better,
No, we've established that increasing stiffness up to a certain point is better.
Note, that there is an important difference between both statements.
The first statement is open ended where the other is not.
Which shape beam would be stiffer in our application, a round beam or a square beam or a trapazoid? I mean, our beams have (at least) two different directional forces acting on them, up and down type flex, but twisting as well.
Indeed and therefore the distance between the beams is factor here. In my models the largest component resisting the bows moving up and down independently is flexing of the beams in the up and down plane and not torsion. Torsion resistance is actually only a small component overall.
Therefore box-like (rectangular) beams with lots of material in the top and bottom sides is most efficient. However some shaping is needed on the front to allow for fairing of the beam into the hull. Waves hitting a beam with flat frontsides is not a good idea. Of course, flat backsides and top or bottom sides are desireable; that uses less material (weight savings) and makes it easier to fit blocks, dolphinstrikers and other stuff to the beam. Now look at the Falcon and Aussie Blade beams and you'll see these considerations being implemented. That is the reason why for example the trampoline track (the only things implemented for convenience) is situated in the upper backside corner. Here it allows for easy and clean tramp fitting but also adds the most to the stiffness of the platform. Designs with such tramp tracks halfway up the beam are simply not smart.
From memory those custom made F16 beams are equivalent in stiffness to 90x2 mm round beams but they are smaller and fitted with a more practical overall shape. The rectagular shape also looks the beams better in place in the beamlandings then a round beam that can more easily twist in its beam landings.
Wouter
