Re: Cockpit drains
Many thanks for your reply. It seems we both feel the designer (back in 1964 or thereabouts) did not fit adequate drains. The first point I would like you to consider is why you quoted the flow through a drain point 20" underwater. In fact, ours are about 20" underwater, but I've always thought that was just because there is not a convenient point on the hull nearer the waterline to exit them. My point is that the distance underwater should not make any difference to the flow rate - it's the depth of water above the waterline which matters... and we have only 3" + depth of water in cockpit. Would you agree?
If so, and we are only concerned with shifting the top 2000 gallons of water in the cockpit, my feeling is that draining this to just ABOVE the waterline would be safer than installing large ports 20" down, so that there are no huge holes below the waterline, which would DEFINITELY sink the yacht fast if anything went wrong with the pipe connections at any time (yacht on mooring, owner absent for example).
So I am thinking that large horizontal pipes from just above the cockpit floor (currently 3" AWL, but 7" AWL if we raise the floor) would be the safest option for draining the "swamp-water", allowing the existing tiny drains to finish the job. I guess I would put non-return valves in the big drains, so water doesn't get pushed back in when sailing heeled, but these would have to open with only 1-2" head of water or else they would defeat their object. Or else I would fit them with on/off cocks that were in easy reach without having to open a locker, for example.