Seif bailing cockpit?

[duluthboats]

Is there a rule of thumb for the height above the water line for the sole in a self bailing cockpit? Is there a minimum scupper size in proportion to the cockpit?

Gary

[Tom Lathrop]

Hi Gary,

Assuming you are talking about a powerboat, I'll give you my last experience. The cockpit is about 6 1/2' long and about 7 1/2' wide with a slope to the transom of about 2 1/2 ". Two scuppers of about 12 - 14 sq in are about 4" above static waterline with flaps on the stern. I now consider the slope excessive and would reduce it slightly in favor of more scupper height.

A sailboat is another matter entirely and depends on so many factors that you will need to read a design book to take them all in. Many sailboats are poorly done (as well as a few powerboats) so that they require scupper plugs to keep your feet dry when underway and heeled under sail.

It works well. Once I had way too many people in the cockpit and some water came in through the scuppers. No water has ever entered under normal operations and very hard rains have not given any trouble. I occasionally will stop the boat in rough water to do one thing or another and let the boat idle in reverse with the stern to the waves. It will hang ther for quite awhile and the waves obviously slap against the transom above the cockpit sole. The flaps keep all but a minor amount of water out.

The height you need will depend on the immersion per inch at the transom for expected loads in the cockpit, plus some safety factor if you can afford teh extra height.

[duluthboats]

Thanks for your reply Tom. This is for a power boat, but of course I always have to make things complex. The cockpit is forward, it has 39 sq ft of area on the sole. The hull requires 700lbs for 1” of immersion at CB, the forward bulkhead of the cockpit is 128” forward of CB. How do I calculate how many lbs I would need to get 1” of immersion at the forward bulkhead?

Gary