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Old 01-06-2008
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Cockpit Drains

I sail a 1976 Pearson 28, like the one reviewed in the Jan/Feb edition of "Good Old Boat". In the review Ted Brewer praised the design's seaworthyness but called attention to "...too-small cockpit drains...". So how do you size your cockipit drains? I've read that I should fill the cockpit with water and see how long it takes to drain, but if the two 2 inch drains are too small, how do I compute what would be enough. Its been way too long since I took solid geometry to be able to figure this one on my own. Also, is it feasible to add cockpit drains, or is a bucket a better option?
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Old 01-06-2008
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Ideally, the cockpit should be able to drain itself if filled in just a few minutes... the shorter the time, the better...

Adding drains or enlarging the existing drains are both good ways to decrease the time it takes to clear, but going to large can be a problem too. If your cockpit drains are too big, you can drop stuff through them. Two-inch drains are the largest I'd personally go. A lot of stuff, like keys and such will fit down a 2" drain if you're not careful. Don't ask me how I know.

It also depends on whether you boat has a bridgedeck or not. The way my boat was originally designed, it had no bridgedeck, and if the dropboards weren't in place, any significant amount of water in the cockpit would lead to a lot of water in the cabin. This past spring I built a bridgedeck for the boat, and it's a big help in making the boat more seaworthy. Not only does it help prevent water from getting below, it also takes up five cubic feet or so of cockpit space—that's over three hundred pounds of water that can no longer fit on my boat—since each cubic foot of seawater is about 64 lbs.

Here's a photo of the cockpit prior to the bridgedeck

and one of the bridgedeck installation.

The bridgedeck is about an inch higher than the top step you can see in the left side of the top photo. The top of the panel going across the companionway is the same height as the original first dropboard and a tiny bit higher than the cockpit seat lockers are. The stern end of the cockpit is about two-to-three inches shorter than the cockpit seats, so any real pooping will start to drain rather quickly. There are also two inch cockpit drains on either side of the cockpit.

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Last edited by sailingdog; 01-06-2008 at 01:05 PM.
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Old 01-06-2008
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Look at it this way: If your cockpit is the same size as a bathtub, and your drains similar to two bathtub drains, you can fill your tub at home, clock it, split that in half to see how long your cockpit will be carrying 500 or more pounds of extra water if it is pooped by a wave.
Since 1976 ORC regulations have changed, what was "sufficient" on the market and in racing is no longer acceptable, but what you have is typical. If you're going offshore or out in bad wx, by all means add drains or transom drains (straight out the back, with a rubber flap on the transom to prevent water from splashing in).
There's also nothing to stop you from installing drains that are big enough to swallow keys and such--and also adding covers or screens, that you only remove when you are expecting water to come aboard. In this case you CAN have your cake and eat it too.
You just want to make sure that any additional drains won't allow water to come in when you are heeled (some designs cross the drains under the cockpit) and to the extent possible, they are fitted with seacocks or there are plugs nearby, even if they drain above the waterline.
A bridge deck helps. A fastpin to make sure the first hatchboard can be kept in place to act the same way, helps. Or you can find strong points to lash something like an Igloo cooler in the cockpit--ensuring it is full of floation not water during bad wx. (Fast kludge if you "need it now".)
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Old 01-06-2008
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If your cockpit drains are 2" now, I'd be surprised if they were deemed "too small" - perhaps someone has already addressed the issue. Do you find your cockpit slow to drain??

Lots of manufacturers installed cockpit drains in the 3/4" - 1" size range, and those indeed can be slow to drain, esp depending on what kind of fittings and valves were installed at the time.

A large, straight-through above-the-waterline drain system can work well if the boat design can facilitate that, but sometimes following seas can scooch some water into the cockpit.

And, as SD mentioned, overly large drains need screens of some sort to avoid losing items, but then you immediately defeat part of the up-sizing because the screens themselves become restrictive to flow.

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".. there is much you could do at sea with common sense.. and very little you could do without it.."
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