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Old 29-08-2013, 18:15   #31
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Re: Cockpit drains

Quote:
Originally Posted by Cheechako View Post
I'm a skeptic when I read these things. A lot of work is involved, plugging two holes low in the boat is involved, longer hoses with possible vibration/wear points are installed. I'm just not one of those people with "fear of seacocks " I guess. You have a simple straight run now. leave it!
Remember, Murphy is alive and well..... If you eliminate all the seacocks in your boat but one... That is the one that will sink the boat!
I went thru the "seacock elimination" scheme years ago because some cruiser wrote it in a book and it sounded logical. Ireduced 12 seacocks down to about 7 or 8 as I remember. In the end I had a bunch of lengths of hoses, with a bunch of fittings/tees etc and hose clamps running through the boat. Frankly, in the end, I felt the boat was more likely to sink after I was done, and of couple of them didnt drain as well as they used to.
Yes, I totally agree with what you are saying here.

I am only contemplating this particular idea as I feel it might be a big gain to get to outlets that are currently well below the waterline to a point above the waterline. If I cannot achieve that I will do exactly as you suggest and keep it simple, in fact, keep it exactly as it is (albeit with new fittings). I am well aware I am trying to second guess a very smart original owner who set the boat up and a very experienced boat builder who designed it that way, and I am not blindly backing myself against those guys.

For the record, I very much subscribe to the theory of one fitting per job, as I agree that the complexity of "T" pieces in the plumbing is probably more risky than a good quality new skin fitting attached properly in the first place.

The large number of fittings I can currently eliminate are because I have chosen not to have a number of pieces of technology that were fitted to the boat when I bought it, such as the watermaker and engine driven eutectic fridge, plus one or two fittings seem to have been made obsolete over the years, they are no longer connected to anything, so I feel glassing over those is also worthwhile. I will however, take the good advice made earlier/elsewhere, and keep one well placed and easily serviced fitting as a backup engine cooling/new technology fitting, just in case.

Matt

P.S. Tall ships leaving Adelaide on Sunday morning. We'll be there to wave them off, might even follow them down the coast for an hour or two... or three.... maybe all the way back to Melbourne... tempting.
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Old 02-09-2013, 19:18   #32
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The drain holes really should be below the water line so that the Bernoulli principle is exemplified. With the holes mounted below the waterline and the boat or water moving (depending on if you're docked in flowing water or underway) the water in the cockpit would actually be sucked out rather then gravity Fed which is considerably slower. Its simple low pressure, high pressure physics. If I were you I wouldn't move the drains. The engineer placed them in that exact position for a very specific reason.
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Old 02-09-2013, 19:35   #33
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Re: Cockpit drains

You make a interesting application of that principle. To me it feels like some kind of venturi effect cover over the outlets would be needed to create the pressure drop, but I can see how the principle might apply, though I think it would be a pretty weak effect given the practical aspect that although there is an increase in flow rate over the outlets, the fluid pressure would be basically equalised by the practically infinite "pipe diameter" presented by the clearance between the underside of the boat and the bottom of the water body you are passing through. Still, the old self bailers from my dingy sailing days did a good job using the venturi effect. Downside of a venturi cover might be that a vigorous application of reverse would jet water up the cockpit vents. Not so good.
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Old 03-09-2013, 08:46   #34
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Re: Cockpit drains

There is no reason why they should be under water other than the fact that cockpit floor is too low to make the exits above the water level. In fact, many boats with high placed cockpits have the exits above the water.

Bernoulli or Ventouri, when the drains may be needed most is after the boat gets knocked down or badly pooped. In both cases the boat will either move very slow or be completely stopped - any suction effects will be probably negligible.

BTW ask a physicist, but something is telling me that given the same levels differential, an exit above the water will drain faster. I might be wrong, so check this out.

b.
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