Scantling calculations for a high speed light craft vesel

I am trying to do to Scantling calculations for a 7m high speed catamaran as per the DNV classification society.
Primary aim is to find thickness, spacing of various structural member, Have an autocad design ready.
I went through the classification society rules and only thing i could get out of it were the loads that are actually acting on the catamaran. The material being used for the catamaran are fiber composites.
I could also find out the maximum loads the composite can bear at different places in the ship.
The only problem is I am not able to co-relate both of them as the equations for maximum load is an equation of any variable which are unknown.

So can someone guide on ow to go about this?
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