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post #1 of 9 Old 10-14-2007 Thread Starter
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Cockpit drain cross over

I remember someone a while back telling me to route the stbd cockpit drain to the port side and port drain to stbd thruhull to prevent water from coming up when heeled. Someone went to a lot of trouble to do this on my boat, resulting in some ugly plumbing that has never given me a warm fuzzy feeling (they used PVC for elbows!!!). And, water still comes up when heeled.
I cant figure out if there is really an advantage to crossed drains or if it is just a trend someone with poor scientific understanding started. Can anyone shed some light on this?
Ben

Last edited by sailboy21; 10-15-2007 at 12:04 AM.
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post #2 of 9 Old 10-15-2007
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Well, if you're on a port tack and the water in your cockpit is down on the starboard side, but the drain goes up to the port side, seems to be counter productive, doesn't it? Its not going to flow uphill very easily. Not sure what the standard is, but maybe some sort of check valve would be a better way to keep the back flow out? If it doesn't inhibit the flow out.

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post #3 of 9 Old 10-15-2007
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Originally Posted by sailboy21 View Post
And, water still comes up when heeled.
bestfriend is right, water won't flow uphill. The water in your cockpit may be coming from all the crazy plumbing draining back when you're heeled.

What kind of boat is this?

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post #4 of 9 Old 10-15-2007 Thread Starter
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Both thru-hulls are low enough where the water doesn't flow uphill, however it does have to go through more hose. The whole setup seems convoluted to me. Add to that neither has a proper seacock, and one thru-hull is a bronze nipple glassed into the hull. Makes me miss my O'Day where the cockpit just drained out the transom.. The boat in question is a Rawson 30.
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post #5 of 9 Old 10-15-2007
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I think the purpose is for when you get pooped - they will drain quickly. Otherwise on a beat the drain may be below the waterline giving backflow, increasing the weight on that side giving more etc. They don't need seacocks as the presumption is they would always be open in case it rains.
The water can only come up when heeled if the outlet is above the inlet but still underwater. The outlets may be misplaced. They should have double clamps.
How big is a nipple? It should be about a 2" drain.
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post #6 of 9 Old 10-15-2007
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Originally Posted by sailboy21 View Post
Both thru-hulls are low enough where the water doesn't flow uphill, however it does have to go through more hose. The whole setup seems convoluted to me. Add to that neither has a proper seacock, and one thru-hull is a bronze nipple glassed into the hull. Makes me miss my O'Day where the cockpit just drained out the transom.. The boat in question is a Rawson 30.
Soo.. what's stopping you from draining it out the transom now??

Just connect your cockpit drains together and run them all to a single through-hull in the stern just above the water line. On the opposite side to your exhaust pipe would be a good idea..

--Cameron
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post #7 of 9 Old 10-15-2007
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i had that cross-over drain thing on my thunderbird. i think the idea was that when the water got in the cockpit, there would be enough room and drop in the pipes so some/most of the water would drop into the pipe and then when you change tack, that water would then dump out the side, and it whatever remaining water was in there would go into the other pipe and sit until you tacked again. we originally just had a center drain but when the boat heeled, the water never drained and just gathered on the sides. anyway, the two drains on the side never worked well and there was always water sloshing in the boat. i think if i was to do it again i would just have them run out directly out the back instead of crossing. sold the boat tho.
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post #8 of 9 Old 10-15-2007
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The Rawson is capable of being a bluewater cruiser. As such much of the sailing will be downwind. Transom drains in that situation are more likely to bring water aboard. They would also have to have the equivalent diameter of 2x 1.5 -2"= 3" if you could get thru hulls in that size.
The crossed-over drains are a blue water system. The reason being that if you get a wave over the stern the cockpit is quite large and the extra weight sets the stern down reducing the bouyancy and making it more likely to catch the next one unless the drains work rapidly.
It is possible to get inlets with no return valves. The pvc angles shouldn't be a problem if there is flexibility in the hoses. I was incorrect to say valves were not required. They may be open usually in case of rain, but the potential to shut off in case of a hose coming adrift is required. Your actual design will depend on the height of the inlets versus the waterline.

Last edited by chris_gee; 10-15-2007 at 05:55 PM.
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post #9 of 9 Old 10-15-2007 Thread Starter
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The Rawson is capable of being a bluewater cruiser. As such much of the sailing will be downwind.

Or if you carry 6 jerry cans and have a good diesel! Just put 400 hrs on her going from San Diego to SE Alaska... Wish I could sail to windward in light air, the saga of a heavy full keel boat....

I was incorrect to say valves were not required. They may be open usually in case of rain, but the potential to shut off in case of a hose coming adrift is required. Your actual design will depend on the height of the inlets versus the waterline.

Anything below or close to the waterline must have a seacock!!!!
As far as draining in an emergency, I felt the two 1 1/4" drains were inadequate for the size of the cockpit, so I did add a 1 1/2" drain which drains out the hull just above the waterline. Incidentally, that is the only proper seacock on the boat.
Thanks for the input
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