[Public-list] Crossed drains (was ...drains above the water line)

[Hugh McCormack]

Good day Rachel,

I spent the best part of a year working for a fibre-glas boat builder 
(sadly, not Whitby Boats!) when I was in university.  The boat line I was 
helping to build had crossed cockpit drain hoses leading to transom through 
hulls above the water line.  It was part of my job to crawl in under the 
cockpit and fit the hoses to the drains after the deck was lowered onto the 
hull.  It was explained to me that the crossing of the hoses was to 
prevent/limit water coming in via the lower opening and flooding the cockpit 
when the boat was heeled.  In other words if a transom drain was below the 
water line when heeled the other end of the hose would be, by virtue of 
being crossed, above the water line at the cockpit end.  Any water entering 
the cockpit by any means would accumulate until its level was above the 
level of the transom end of the other drain and then start to run out.  The 
key is to make sure that the "upper" transom through hull is as close above 
the waterline as possible, but not below, at the normal range of trim when 
heeled.  As the boat's angle of heel lessens water would run out of both 
drains.  I hope you can visualize this.  It would be a lot easier to 
illustrate with a sketch.

The straight down drains in our Albergs mean that there is always water in 
both hoses up to the level of the waterline when the boat is stationary.  I 
suspect that during forward motion of the boat there would be a venturi 
effect caused by the passage of water across the outside of the through hull 
fittings and this would tend to draw down the waterlevel in the hoses.  In 
the process it would accelerate the draining of the cockpit.

Hope this helps.

Cheers,

Hugh


>From: Rachel <penokee at cheqnet.net>
>Reply-To: Alberg 30 Public List -- open to all 
><public-list at lists.alberg30.org>
>To: Alberg 30 Public List -- open to all <public-list at lists.alberg30.org>
>Subject: Re: [Public-list] Cockpit drains above water line
>Date: Sat, 17 Mar 2007 10:54:14 -0500
>
>Here's something I've never understood (but I'm probably missing
>something):  If you have crossed drain hoses, and you're heeled over
>and the cockpit takes on water, how does said water exit "up" from the
>cockpit to the opposite through-hull?

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