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post #1 of 22 Old 10-30-2013 Thread Starter
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Cockpit Flooding

Is the cockpit of a sailboat always designed to handle the weight of being full of water? Say you are swamped by a wave, cockpit full of water- that could be 1,000's of pounds of weight acting on the cockpit floor (all dependent on you cockpit volume), are they designed for this? Or should they be strengthened.
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post #2 of 22 Old 10-30-2013
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Re: Cockpit Flooding

The bigger question is whether the scuppers are sized to empty it quickly enough. Many are not.


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post #3 of 22 Old 10-30-2013
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Re: Cockpit Flooding

What is considered "big enough" for the scuppers?

The footwell of the cockpit is somewhere in the 60-100 gallon size range I think (note that this is under 1000lbs). The two scuppers are 1.5".

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post #4 of 22 Old 10-30-2013
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Re: Cockpit Flooding

Mine drains pretty fast. But it can fill pretty fast too. Let's just say I try to avoid heavy following seas.



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post #5 of 22 Old 10-30-2013 Thread Starter
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Re: Cockpit Flooding

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Originally Posted by Minnewaska View Post
The bigger question is whether the scuppers are sized to empty it quickly enough. Many are not.
Unless your cockpit is wide open at the stern, no matter what the scupper size the cockpit will completely fill (on getting hit by a big breaking wave) with water. Scupper size will only determine how fast at that point is drains. Until it starts draining, cockpit will have full weight of the water.
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post #6 of 22 Old 10-30-2013
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Re: Cockpit Flooding

Cockpits SHOULD be designed to handle the weight of the water that might end up in them. Some definitely are. Is yours? We don't know. Plugging up the drains and filling the cockpit with a garden hose may give you an idea, but even that's not the same as having a wave drop from ten feet above you and hit your cockpit and cabin trunk with the force of a freight train. A good resource for this type of question is probably Desirable and Undesirable Characteristics of Offshore Yachts, edited by John Rousmaniere.
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post #7 of 22 Old 10-31-2013
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Re: Cockpit Flooding

I like to use the published ISAF offshore rules for target values like this. While generally the design should ensure that a cockpit full of water will not capsize or otherwise dangerously impair the boat, that is only guaranteed when the boat is certified (i.e. a CE certification to ISO 11812 or similar).

ISAF Special Regulations - Category 4 Monohull

Quote:
3.09 Cockpits - Attention is Drawn to ISO 11812
3.09.1 Cockpits shall be structurally strong, self-draining quickly by gravity at all angles of heel and permanently incorporated as an integral part of the hull. **
3.09.2 Cockpits must be essentially watertight, that is, all openings to the hull must be capable of being strongly and rigidly secured **
3.09.3 A bilge pump outlet pipe shall not be connected to a cockpit drain. See OSR 3.09.8 for cockpit drain minimum sizes **
3.09.4 A cockpit sole shall be at least 2% LWL above LWL (or in IMS yachts first launched before 1/03, at least 2% L above LWL) **
3.09.5 A bow, lateral, central or stern well shall be considered a cockpit for the purposes of OSR 3.09 **
3.09.6 In cockpits opening aft to the sea structural openings aft shall be not less in area than 50% maximum cockpit depth x maximum cockpit width. **
3.09.7 Cockpit Volume
i) earliest of age or series date before April 1992
the total volume of all cockpits below lowest coamings shall not exceed 9% (LWL x maximum beam x freeboard abreast the cockpit). Extract File Only MoMu2,3,4
ii) earliest of age or series date April 1992 and after
as above for the appropriate category except that "lowest coamings" shall not include any aft of the FA station and no extension of a cockpit aft of the working deck shall be included in calculation of cockpit volume Extract File Only **
IMS-rated boats may instead of the terms LWL, maximum beam, freeboard abreast the cockpit, use the IMS terms L, B and FA. Extract File Only **
3.09.8 Cockpit Drains
See OSR 3.09.1. Cockpit drain cross section area (after allowance for screens if fitted) shall be:-


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post #8 of 22 Old 10-31-2013
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Re: Cockpit Flooding

Quote:
Originally Posted by casey1999 View Post
Unless your cockpit is wide open at the stern, no matter what the scupper size the cockpit will completely fill (on getting hit by a big breaking wave) with water. Scupper size will only determine how fast at that point is drains. Until it starts draining, cockpit will have full weight of the water.
Right, that's why I said "sized to empty it quickly enough"

Here is the rest of the ISAF reg that Zanshin posted....

Quote:
3.09.8 Cockpit Drains
See OSR 3.09.1. Cockpit drain cross section area (after allowance for screens if fitted) shall be:-
a) in yachts with earliest of age or series date before 1/72 or in any yacht under 8.5m (28ft) LOA - at least that of 2 x 25mm diameter (one inch) unobstructed openings or equivalent **
b) in yachts with earliest of age or series date 1/72 and later - at least that of 4 x 20mm diameter (3/4 inch) unobstructed openings or equivalent
Note these say "at least". If one is questioning whether the cockpit can withstand the weight of the water, as the OP asked, they should really be focused on how quickly they can get it out.


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post #9 of 22 Old 10-31-2013
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Re: Cockpit Flooding

too many cockpit scuppers are only designed to drain away rain and washing out water. I think the minimum of 1.5 inches should be the very minimum anybody should consider. My boat has two at that size, I will be upgrading to 2 inches by spring

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post #10 of 22 Old 10-31-2013
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Re: Cockpit Flooding

Another issue is making sure that water in the cockpit will not go into the cabin due to poor design (low bridgedeck). That is at least just as important as draining speed.

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