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iGRF View Drop Down
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Post Options Post Options   Quote iGRF Quote  Post ReplyReply Direct Link To This Post Topic: Breathers / Drain holes
    Posted: 08 Aug 17 at 8:41pm
Anyone ever considered/experimented with Goretex breather valves?
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maxibuddah View Drop Down
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Post Options Post Options   Quote maxibuddah Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 17 at 9:57pm
we have them on things in work to help along those lines so don't see why they shouldn't work in this instance. There will probably be some class rule preventing them though as exotic materials  Wink

Edited by maxibuddah - 08 Aug 17 at 9:58pm
Everything I say is my opinion, honest
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JohnJack View Drop Down
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Post Options Post Options   Quote JohnJack Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 17 at 10:03pm
Do you really need a breather hole? 
You aren't building up that much pressure are you?
Boats should be stored with hatches open to let the air circulate

Wouldn't more pressure make a boat stiffer/panels less likely to flex under load??

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423zero View Drop Down
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Post Options Post Options   Quote 423zero Quote  Post ReplyReply Direct Link To This Post Posted: 08 Aug 17 at 10:23pm
Johnjack,
when pressurised hull is placed in water, cooler water reduces pressure in hull causing a vacuum, this can suck in air/water to equalise pressure.
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PeterG View Drop Down
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Post Options Post Options   Quote PeterG Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 17 at 10:57am
You aren't building up that much pressure are you?

You don't need a large pressure difference across a hull to end up with a significant load on the deck/hull seam (or elsewhere). If you have any sort of weak point it's likely to be made worse if you don't have a breather. Assuming your hatches are vertical, and only under water exceptionally, a 2-3mm hole drilled in the middle of the cover should be all you need to prevent damaging pressure differentials, with little likelihood of significant water influx. 
Peter
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Cirrus View Drop Down
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Post Options Post Options   Quote Cirrus Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 17 at 11:15am
Boats can very easily leak without a breather.  Cold water and a warm day when you seal the hatches creates a partial vaccum as already described.  Additonally as you move abround the deck it flexes very very slightly and guess what you can pump air out and .. water in.  This can happen anyway, which is why sometimes it is very difficuly to find some leaks when off the water but you are loading the dice if the sealed hull is already likely to be at -ve pressure.  

So always have a breather .... btw some of the most common causes of leaking are 'O' ring seals around hatches and drain bungs.  Consider replacing the 'O' rings just occasionally ! 
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Post Options Post Options   Quote zippyRN Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 17 at 11:20am
Originally posted by JimC

Oh yes, I'd definitely put a breather in. Don't know about a hole in a hatch cover though, I'd look for a spot which is never under water and never sitting in a puddle - or else, as you say, going through a tube to have the same effect.


iirc the breather hole  on  the Laser is at the  the front of the cockpit just under the toestrap plate , presumably  that was felt t o be a place  that matched that description ... 

 also intetersitng to note  that how even quite old   GRP boats can  have that styrene  smell smell if you ope nthe bungs  / hatches after a long  time ... 
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Post Options Post Options   Quote zippyRN Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 17 at 11:27am
Originally posted by iGRF

Anyone ever considered/experimented with Goretex breather valves?


and what if any advantage  would they offer over  small holes  or a  u-bend  on a larger  breather?
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PeterG View Drop Down
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Post Options Post Options   Quote PeterG Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 17 at 12:17pm
and what if any advantage  would they offer over  small holes  or a  u-bend  on a larger breather?

Probably depends how much time you spend upright!
Peter
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GarethT View Drop Down
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Post Options Post Options   Quote GarethT Quote  Post ReplyReply Direct Link To This Post Posted: 09 Aug 17 at 1:48pm
From memory my old moth (magnum 9.9 I think) had a piece of thin rubber membrane glued over a reasonably large breather hole, so it would move in and out like a diaphragm but stay waterproof.

I may have this completely wrong, but it's what I assumed it was for!
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