water ballast sail boats

[cnac]

I am designing a 26 ft sail boat with water ballast tanks port and stbd for stability to reduce heel while sailing. THe tanks hold about 750 lbs of water.
When the 750 lbs of water is transfered from one side to the other, what size of pipe is used (ie what transfer time is acceptable) what type of valve is used? would it be a butterfly valve or ball valve. What type of pumping arrangement is used if water is not transfered by gravity before the tack, but transfered 'uphill' after the tack.
thanks to anyone who could shed some light on the details of this type of system.

[Eric Sponberg]

You should use at least 3" diameter pipe, PVC is acceptable. The quickest, easiest, cheapest valves are Valterra gate valves, also made in PVC and/or other plastics--lightweight and inexpensive--lift the handle for open, push the handle down for closed. At 3" diameter, transfer should take on the order of a minute or less for 750 gallons. Use 4" pipe if you want a quicker time. Valterra also makes 4" valves.

Pumps are another matter. Most pumps are for small diameter pipe, up to 1.5 to 2". They can be used, but at small diameter, they will take some time, on the order of some minutes, to pump 750 gallons. You might not be able to find an inexpensive large diameter pump. You would likely need something on the order of .5 HP to 1.0 HP. check the flow rates on the pumps. There are various manufacturers. Depco Pump Company handles many marine brands.

Eric

[FAST FRED]

We have a 33ft cutter , based on a Maurice Griffiths design.

The water is in 6 tanks ,(105G US ) is in 3 tanks on each side of the hull.

The boat is about 17,000 lbs with 7000 in the keel.

With a 2 inch bronze Edson pump , the water can be transfered in 2 or 3 min.

Easiest work if you flood the leeward tanks before tacking , so gravity helps.

That said , for us it was a complete waste of time as the difference is only 1 or 2 deg or so of angle of heel change

Now if you had a racer that was 5000lbs with 12 ft beam it might be different (think old NY Sandbaggers).

Great to monitor water use , but for a normal ocean boat , not much bang for the bucks.

FAST FRED