How do you do a self bailing cockpit?

[myona]

Originally posted by mayona:
I purchased a 1946 wooden boat. Was built in IOW by H Rooke but got no more info. I would like to find out what type is the boat and some hints for its restoration. LOA 8.1m Beam 2.3.

I am restoring this boat and would like to build a self bailing cockpit and benches on either side. Could any body send me some sort of plans or drawings /pics including certain measurments
Any help pls
thanks
http://www.imagestation.com/picture/sraid102/p6044bf1fe3efc1fbdb9f6ac368597d18/f9b3e34f.jpg
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http://www.imagestation.com/picture/sraid102/p9441f57082f448dbd5557cde34a6b1dc/f9b3e3af.jpg

http://www.imagestation.com/picture/sraid102/pc4e75f332d1d4b728ef8e1a4bdae28b9/f9b3e3ab.jpg

[buhmkin]

A self bailing cockpit is pretty simple technology, I think I can explain without pics (for simplicity's sake I'm going to assume you have a cockpit installed-that might not be the case but I can't do much for you there, sorry).

First you need two cockpit drains, across from each other on the either side of the cockpit floor.

These drains are each connected by hose to a valve and thru hull fitting mounted lower than the cockpit floor. To make a cockpit self-bailing you cross the hoses so that the port drain is connected to the starboard thru hull and vice versa. So if you're swamped and heeling to port, the starboard thru hull is out of the water and can drain freely. I used to have an H28 set up this way and was pretty happy with the setup.

[Aramas]

Generally you need to have the cockpit sole narrow enough and high enough above the waterline that the sides stay above water when heeled. It's also wise to keep volume low, since a lot of water up high is generally considered to be a bad thing. You also want hefty drains so the water exits fast. Sink fittings with plugs are popular too, so that it can be filled with water and used as a bath smile.gif

Generally you need 30 cm between the cockpit sole and the seat, then something like 40-45 cm from the seat to the coaming for decent back support. It's also common to have the spacing between the seats (ie cockpit sole width) set so that you can brace your feet on the edge of the opposite seat with you back against the seat back.

Make sure you have the back and side sloping outward at a comfortable angle so you don't feel like you're sitting in a church pew.

Pretty boat btw.

Just an impromptu rule-of-thumb thing is to take an arbitrary height above the waterline (we'll use 30 cm here) and assume that it will be self draining up to a desired angle (45 degrees here for simplicity). Then just use basic trigonometry to work out how wide the cockpit sole can be before it hits the waterline when heeled.

So we have a triangle with the 90 degree angle at the top and the hypotenuse on the bottom. The height (0.3 m here) is the opposite side to the heel angle (we can use 45 degrees here for starters) and the adjacent side is the cockpit sole width. Since we chose 45 degrees then the two angles other than the 90 degree one are the same, both sides of the triangle are the same and you can have a cockpit sole width equal to twice the height ( so 60 cm)

Since the tangent of an angle is given by the ratio of the opposite side over the adjacent side, we get

tan theta = opposite/adjacent

which becomes

adjacent (sole half width) = (cockpit sole height)/(tan of heel angle)

So half width = 0.3/(tan 45)
= 0.3/1
= 0.3m

Therefore you could have a cockpit sole 0.6m wide with a height of 0.3 m if you were happy to have it stay dry at heel angles up to 45 degrees. Use whatever numbers float your boat.

Simple smile.gif

Note that it's just using an arbitrary heel angle and height. Play with it until you're happy with it.

Additionally, most boats 'roll up' as they heel, so the cockpit sole effectively rises relative to the waterline, but don't worry about it - it just gives you a bit of leeway.

Someone should check this since I just made it up and didn't bother checking any books. I think it's right though. I got it backwards and hit the post button instead of preview, but I think it's fixed now. Did I overlook anything?

[ 04-20-2004, 02:57 AM: Message edited by: Aramas ]