I seriously doubt that 400 lbs of weight = 1 inch of displacement is a linear equation. My guess is that every inch of displacement would require a progressively higher weight. Most of us have seen the chart on how much water would flow through a one inch hole in your hull, and how dramatically it increases with every increment of depth below the surface. I'm pretty sure that same principle exerts a greater upward force on your hull, the deeper you try to push it down in the water.
But back to scuppers, which were obviously not designed by the top of the class in naval architecture. I had to remove and clean out my oil tank this week-end, and while I had it out, I replaced the scupper hose on that side. I'm not sure why it is a 1 1/2" ID hose, the volume of any fluid system, gravity or pressure, is determined by the SMALLEST opening in the entire system. In this case, the deck drain and the scupper outlet, which are considerably less than 1 1/2". Unless fluid dynamics dictates that for equal volume, flow is greater in a pipe that is half full than it is in a pipe that is full.
Scuppers may be okay for keeping your feet dry, but I would hate to have a wave on deck, and be waiting for their pitiful flow to keep me upright and afloat, especially if the deck got down close to water level, and the scuppers under water. We have had several accidents lately, I heard the CG responding to an overturned vessel while I was working on mine Saturday, and 2 guys are still missing from an overturned 35 footer found 3 miles outside the inlet last Tuesday. It got me to thinking what was the best way to get rid of a dangerous amount of water on deck?
Given my current set up, 2000gph aft(adding a second one the next time I have the live well out) and 1100gph forward bilge pumps, I think the best bet would be to remove the aft deck pie plate, and drain water to the bilge, perhaps in stages. My batteries sit at deck level under the jump seats. First, it would lower the COG and increase stability, and I know that my 2000 Rule will pump at least 20 times as fast as my scuppers will drain. I think that having back up deck drains, that pump directly overboard, using a live well pump, is a damn good idea on a blue water boat. I could do 2 on my boat in an afternoon for under $400.
I had a similar idea while replacing the scupper hose. That was to put a 1 1/2" reducer tee in the line, with a live well pump attached to the smaller outlet of the tee, pumping to a thru hull below the rub rail. That would suck water off a flooded deck many times faster than it would drain by gravity through the scuppers.
Food for thought.
www.go2marine.com
