low speed semi-swath above 100 ft

1-hi! i was inspecting abekin rassmussen swath boats. i realized that they have huge drafts and going in lower hulls are really drawback. why do people not prefer semi swaths?

2-and another issue, how are they designing offshore swaths cross deck clearance height. Is it according to wave heights or is there a calculation for this.

3- Also in semi swaths, adding a bow stem like wave piercing catamaran (with bulbous tubes) should be a positive effect for pitching by adding displacement at bowside, isn't it?

thank you

 

1) Define semi-swath
2) Combination of wet deck (or cross deck) clearance and structure weight.
3) No. The addition of bulbous bows (or WP bows) has a minimal effect. It only really affects the waterline length & length-displacement ratio and its benefits to a vessels design.