what's the logic of a cockpit drain ending under the waterline???

[rotrax]

On or 27 ft yacht we have 2 x rigid 4 inch cockpit drains though from cockpit to stern via lazerette. They took a wave over the stern mid Atlantic that filled the cockpit, it took 30 minutes to drain via standard 2 x1 1/2 inch flexible pipes.

Brian

I was on the tiller in the Needles Channel 15 years ago. We should have not been there, but it was anothers decision.

We were pooped, the cockpit completely full. The washboards were in, the rogue wave hit the mainsail and the weight of water split the boom, pulling the mainsheet fitting from its track. My lifejacket went off-the water was 2 feet above my head- and my skipper was thrown across the cockpit, hitting his ribs on a winch.

27 foot aft cockpit yacht.

It was only ten minutes or so before the cockpit was clear of water.

Our Motor Sailer might get a rear cockpit full of water-any vessel of similar size could-and opening the door to the swim platform might clear it very quickly.

 

[Slocumotion]

Yes, you've completely misunderstood it.

(Re Bernoulli effect)
Really? Seems to me that this and "hull staining" are the only two suggestions actually addressing the original question.

 

[Momac]

Yes, you've completely misunderstood it.

I agree a submerged discharge will restrict the flow rate of water in the pipe.


I have frequently experienced this issue with underground surface water drainage systems at coastal locations where the tide rises above the outfall. The outcome is often a need for underground storage using oversized pipes or attenuation tanks to cater for the tide locked situation , (these solutions would not be applicable on a boat).

In the case of a boat the pipe being longer and exiting at lower level does not help but adds resistance . Therefore a cockpit drain discharging below the water line is not a very good design and should be avoided.

 

[johnalison]

Therefore a cockpit drain discharging below the water line is not a very good design and should be avoided.

I think that below-water discharge is now all but non-existant. On the other hand, older cockpits were always lower before wives insisted on aft cabins and it was not at all uncommon for the cockpit sole even to be below sea-level. My Mystere sole was just above the waterline, and in fact water could enter when motoring fast, thus draining underwater was the only option, as with many boats of the period.

 

[steveeasy]

I don't understand the point of crossed pipes too...when the boat heels, the water gathers on the "heeling side" of the cockpit and will be drained to the level of the sea level, no more no less, wether the pipe is crossed or not...

Well I thought they were crossed so when your boat heeled over, the cockpit would not fill from the drain ,so to speak. there could be a possibility the cockpit drain actually could be below the sea level.

Steveeasy

 

[steveeasy]

Aren't crossed drain pipes to prevent cockpit flooding from below when heeled?

Sorry, never read your post before replying. That was my understanding of why drain pipes were crossed as well.

Steveeasy

 

[alexlago]

Well I thought they were crossed so when your boat heeled over, the cockpit would not fill from the drain ,so to speak. there could be a possibility the cockpit drain actually could be below the sea level.

Steveeasy

Indeed...thxs, bobgarrett and steveeasy, got it now...

 

[john_morris_uk]

In the case of a boat the pipe being longer and exiting at lower level does not help but adds resistance . Therefore a cockpit drain discharging below the water line is not a very good design and should be avoided.

You obviously don’t sail on a centre cockpit yacht. Our cockpit drains go straight down (through seacocks) and drain water away very quickly and efficiently.

 

[john_morris_uk]

I never fail to be bemused by the paranoia of some regarding through hull fittings and seacocks.

I consider our boat is far more likely to sink after being t-boned by a rogue motor boat than a hose spontaneously splitting or ‘falling off’ a seacock.

We have 14 through hulls at last count and they mostly stay open all the time. They all have good quality seacocks in them that are well maintained.

 

[vyv_cox]

I never fail to be bemused by the paranoia of some regarding through hull fittings and seacocks.

I consider our boat is far more likely to sink after being t-boned by a rogue motor boat than a hose spontaneously splitting or ‘falling off’ a seacock.

We have 14 through hulls at last count and they mostly stay open all the time. They all have good quality seacocks in them that are well maintained.

+1. The only problems I have with our skin fittings is getting hoses off when I want to replace them. The likelihood of them falling off, even when the hose clips have been removed, is remote in the extreme.

 

[Graham_Wright]

This front cockpit is known as the Jaccuzi. It is rumored-but not yet substantiated-that some US owners have blocked the drains, filled the area with water and relaxed.

It does look very much like a hot tub in truth.

UK.

I have a photograph of SWMBO covered in bubbles in our anchor locker.

 

[nevis768]

What an excellent old thread. I just googled this very question when wondering why I had these 2 cockpit seacocks below the waterline. I'm still learning about older boats. I will now leave these open, thanks.