I meant to have a 0/90 fabric and a +-45 fabric outside and a 0/90 fabric and a +-45 fabric inside. There are tow ideas behind: 1) Having the same layup scheme in- and outside will not cause any bending, warping, etc. if loads are applied. (If you pull on an asymetric sandwich, it will bend, because one skin is stiffer in the direction of the load than the other) 2) Assuming that impact loads are the most critical case, I proposed to have an nearly isotropic layup (0/+-45/90 fibres), because I think it is the best for that case, but I might be wrong. I would build small square testpieces and make impact tests to find the answer)
Regarding the boards, I would start from the an existing F16 (since they have all the same sail area and mast height), check which one has the smallest area and is regarded as a good double hander in light and strong winds. In Profili you will have plenty of sections, but probably none designed for a beach catamaran. When I broke the rudder of my friends T, I redesigned NACA 4 digit foils (e.g. NACA 0012) from 8 to 14% thickness by changing nose radius and max thickness location, to improve maximum lift (which allows to reduce board area), cavitation and drag (it is always a trade off, you can improve two of them but worsen the other one). Since my friend complaint always about cavitation we select a board with better cavitation and lift with equal drag than a NACA section. I still should have the data on my computer, so I can send sectional data, if you tell me, which NACA foil would be your starting point (I need it as reference point) and which of the parameters you want to improve.
