[PCW] Overhangs

[Gary Stavrou]

I recently visited the factory of King Catamarans on the Gold Coast  
of Queensland, Australia.
They currently build just one boat, a 38 foot powercat, a Stanyon  
design, and I think it's a very good boat.
They are, however, making a significant addition to their boat, and I  
suspect not with the designer's involvement.
They are adding a HUGE rear platform, four feet deep across the full  
length of the stern.
This will include a large rear-facing seat and a handrail at the  
rear. There is also a substantial stainless steel overhead framework  
to accommodate a canopy, perhaps in canvass.
This addition will be, I'm sure very popular. The expansion of the  
already big cockpit in this way makes it a great "party boat".
My concern is that this extra weight might unbalance the boat in  
rough seas.
There is no compensatory increase in hull length for this huge extra  
rear weight.
I notice that many fine designs have the hulls protruding well to the  
rear of the cockpit.
I assume that the adage used in sailing boats to keep the weight out  
of the ends also applies to powered boats.

So I have a couple of questions to our designers out there.
Is it better (more seaworthy) to have hulls extended aft of the cockpit?
If there is an overhang, in a powercat, should it be kept small and  
light?
As a rule of thumb, if the overhang is, say, one meter above the  
waterline, how far can it extend for safety in a large following sea?  
In other words, what is a safe angle between the back of the hull, at  
water level, and the tip of the overhang.

Gary