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From: <Seakayakerjb_at_aol.com>
subject: [Paddlewise] Bulkhead Pressure Relief
Date: Sun, 20 Jul 2003 10:55:15 EDT
I seem to recall reading here sometime in the past that some have drilled a 
small hole in their bulkheads to aid in relieving pressure that sometimes 
builds up, particularily while transporting to and from put-in/take-out.

What's the experience with leakage from cockpit into "dry" compartment?

What size hole was drilled?

Where was hole positioned--top-center; middle-center; etc?

I paddle British boats and am concerned with "popping" a hatch cover, or 
worse--blowing a bulkhead.  On my Romany I have a lot of cracks in the gel coat on 
the deck and the hull where the bulkheads are.  Might this be from pressure 
build up inside, or just quality issues?

Finally, if leakage is a problem, I would cover the hole (small hole) with a 
piece of Gore-tex on the wet side to allow pressue to pass, but not water  
(electronics manufacturers use this technique--seems to make sense here too).

Appreciate any thoughts PaddleWisers have on this..

Regards.

John Browning
Milwaukee, WI--warm air, cold water changing to cold air and warm water in a 
few months
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From: Michael Daly <michaeldaly_at_rogers.com>
subject: Re: [Paddlewise] Bulkhead Pressure Relief
Date: Sun, 20 Jul 2003 14:20:27 -0400
On 20 Jul 2003 at 10:55, Seakayakerjb_at_aol.com wrote:

> What's the experience with leakage from cockpit into "dry"
> compartment?

Minimal leakage.  If I'm doing lots of rolling and rescue practice, 
the rear compartment gets maybe a tablespoon of water in it.  The 
forward compartment gets less.  With normal paddling, things stay 
bone dry.

> What size hole was drilled?

The smallest bit in the set - 1/16 inch.

> Where was hole positioned--top-center; middle-center; etc?

As close to the geometric centre of the bulkhead as I could guess by 
eye.  That way, the hole is furthest from the water regardless of the 
orientation of the kayak.

> Finally, if leakage is a problem, I would cover the hole (small hole)
> with a piece of Gore-tex on the wet side to allow pressue to pass, but
> not water  (electronics manufacturers use this technique--seems to
> make sense here too).

I thought of that, but have never got around to it.  Leakage hasn't 
been enough to worry me.  I've never been able to figure out if the 
GoreTex would breath fast enough to handle pressure changes.  The 
electronics devices (like my GPS) don't have a lot of volume to deal 
with compared to a kayak.  Taking a hot kayak and dropping it into 
cold water used to cause the hatch covers to suck in very noticibly 
before I drilled the holes.  That's several cubic inches of air in a 
short time.

You could also use a bit of tightly woven cotton and rely on the 
cotton swelling when wet to reduce water intrusion.   If the 
compartment heats, the cotton will breath easily.  If it cools, the 
wet cotton will likely allow a bit of water to be sucked in, but 
nothing serious.

Mike

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From: Gary J. MacDonald <garyj_at_rogers.com>
subject: Re: [Paddlewise] Bulkhead Pressure Relief
Date: Sun, 20 Jul 2003 14:44:21 -0400
Michael Daly wrote:

> You could also use a bit of tightly woven cotton and rely on the 
> cotton swelling when wet to reduce water intrusion.   If the 
> compartment heats, the cotton will breath easily.  If it cools, the 
> wet cotton will likely allow a bit of water to be sucked in, but 
> nothing serious.

Hmmmmm.  Of course.  So a bit of cloth tape, like hockey tape, would do 
the job just fine.  You could even put a pair of smaller holes (like 
3/64 or so) to minimize water flow while allowing air to equalize easily.

GaryJ

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From: Steve Holtzman <sh_at_actglobal.net>
subject: Re: [Paddlewise] Bulkhead Pressure Relief
Date: Sun, 20 Jul 2003 15:10:19 -0700
Jeff,





I too paddle a British designed boat, mine is a CD Gulfstream. The boat came
from the factory with holes drilled in all of the bulkheads. The holes are
about 2/3 of the way up from the bottom of the bulkhead and are about 1/16".





I normally have absolutely no leakage into the dry compartments. Occasionally
on a "wet play day", where we are doing numerous rescues, wet exits, etc I'll
pick up a couple of teaspoons to several oz of water in my day hatch and front
hatch. The rear hatch stays dry because the day hatch is still pretty much dry
and there isn't much water to transfer around.





Otherwise, the boat stays completely dry.





Steve Holtzman


Southern CA.


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From: Dirk Barends <dbarends_at_xs4all.nl>
subject: Re: [Paddlewise] Bulkhead Pressure Relief
Date: Mon, 21 Jul 2003 10:31:45 +0100
>Finally, if leakage is a problem, I would cover the hole (small hole) with a 
>piece of Gore-tex on the wet side to allow pressue to pass, but not water  
>(electronics manufacturers use this technique--seems to make sense here too).

Lettman uses this technigue in the flotation tanks in their FRP canoes.
Haven't tried those myself and haven't heard others about it, so I cannot tell you
how (good) it works, but I think for bulkheads in a kayak it could
work well enough.

Dirk Barends


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