Breathers / Drain holes
Printed From: Yachts and Yachting Online
Category: Dinghy classes
Forum Name: Dinghy development
Forum Discription: The latest moves in the dinghy market
URL: http://www.yachtsandyachting.com/forum/forum_posts.asp?TID=12816
Printed Date: 04 Jul 25 at 5:00pm
Software Version: Web Wiz Forums 9.665y - http://www.webwizforums.com
Topic: Breathers / Drain holes
Posted By: Jack Sparrow
Subject: Breathers / Drain holes
Date Posted: 08 Aug 17 at 11:35am
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I've just bought back Sacré Blue the Farr 3.7 I imported to start the class a few years ago, and the boat has had the drain holes in the stern filled in. But has been made water / air tight. i.e undo hatches and get a rush of air. Question - is this going to make the boat over pressurises and do something bad? Does it need a breather pipe. Farr 3.7's are built quite light - 4mm ply hull skin. The only boat I've had that was like this was a Moth and it had a breather. But then again I think it also had drain plugs? ------------- http://www.uk3-7class.org/index.html" rel="nofollow - Farr 3.7 Class Website https://www.facebook.com/groups/1092602470772759/" rel="nofollow - Farr 3.7 Building - Facebook Group |
Replies:
Posted By: JimC
Date Posted: 08 Aug 17 at 11:57am
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I can't imagine the pressure doing any good at all. I'd definitely put a breather in. How odd to fill in the drains. Wooden self draining boats are enough of a rot trap as it is.
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Posted By: peterthomas
Date Posted: 08 Aug 17 at 12:15pm
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Many of my previous grp boats had breathers in the hatch cover so I think, as a start, I would drill a very small hole in the centre of your existing hatch cover. Then think about reinstating the drain holes for the reasons Jim has mentioned, depending I suppose on why they have been filled in. Might be worth asking that question. Peter
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Posted By: Jack Sparrow
Date Posted: 08 Aug 17 at 12:29pm
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Yes, what I thought. Just needed to check I haven't missed some new way of doing things. I think the idea was to make the boat water tight. But of course this eventually is always never the case. And then you have the internal condensation which can't get out to consider. Oh well another job to do. Jim / Peter - breather worth it on a lightish ply hull as well as drain holes? ------------- http://www.uk3-7class.org/index.html" rel="nofollow - Farr 3.7 Class Website https://www.facebook.com/groups/1092602470772759/" rel="nofollow - Farr 3.7 Building - Facebook Group |
Posted By: Riv
Date Posted: 08 Aug 17 at 12:31pm
| Reminds me of my topper silliness post a few weeks ago. I expect a build up of pressure in a light boat will add volume to the underwater shape and so it will go quicker on hot days when there is little wind as it will float higher out of the water. On the other hand the moment it goes in the water the air will cool and contract and you might get the opposite affect.......I dunno. |
Posted By: peterthomas
Date Posted: 08 Aug 17 at 12:47pm
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Thinking about it a bit more, I would doubt it was the most recent owner (given his occupation and the repairs he made) so must therefore have been the one before. The most recent owner would however perhaps have a view on it. I don't think my boat has a breather at the moment so perhaps just drain holes will do. I will check tomorrow (if I remember). Peter
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Posted By: JimC
Date Posted: 08 Aug 17 at 12:57pm
| 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. |
Posted By: 423zero
Date Posted: 08 Aug 17 at 1:02pm
| What can happen without a breather is hull expands goes in water cools and can suck in water, put a permanent breather somewhere similar to a Laser, stop hull panting. |
Posted By: Jack Sparrow
Date Posted: 08 Aug 17 at 2:09pm
Pretty sure it was most recent owner, we discussed it. Sort of why I was checking things out here. ------------- http://www.uk3-7class.org/index.html" rel="nofollow - Farr 3.7 Class Website https://www.facebook.com/groups/1092602470772759/" rel="nofollow - Farr 3.7 Building - Facebook Group |
Posted By: Jack Sparrow
Date Posted: 08 Aug 17 at 2:18pm
Previous ply hulls have had then on the foredeck near the king post. Not had them in any of the Cherubs I've had or built though. Is there a relationship between tube diameter and air pressure? i.e whats the max / min silicon / pvc tube internal diameter you can use to create the breather with so when you make the loop in it and instal it, it breaths. But creates the air bubble necessary to keep water out. ------------- http://www.uk3-7class.org/index.html" rel="nofollow - Farr 3.7 Class Website https://www.facebook.com/groups/1092602470772759/" rel="nofollow - Farr 3.7 Building - Facebook Group |
Posted By: iGRF
Date Posted: 08 Aug 17 at 8:41pm
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Anyone ever considered/experimented with Goretex breather valves? ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: maxibuddah
Date 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  ------------- Everything I say is my opinion, honest |
Posted By: JohnJack
Date Posted: 08 Aug 17 at 10:03pm
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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?? |
Posted By: 423zero
Date Posted: 08 Aug 17 at 10:23pm
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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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Posted By: PeterG
Date Posted: 09 Aug 17 at 10:57am
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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 Ex Cont 707 Ex Laser 189635 DY 59 |
Posted By: Cirrus
Date Posted: 09 Aug 17 at 11:15am
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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 ! |
Posted By: zippyRN
Date Posted: 09 Aug 17 at 11:20am
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 ... |
Posted By: zippyRN
Date Posted: 09 Aug 17 at 11:27am
and what if any advantage would they offer over small holes or a u-bend on a larger breather? |
Posted By: PeterG
Date Posted: 09 Aug 17 at 12:17pm
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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 Ex Cont 707 Ex Laser 189635 DY 59 |
Posted By: GarethT
Date Posted: 09 Aug 17 at 1:48pm
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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! |
Posted By: iGRF
Date Posted: 09 Aug 17 at 2:16pm
Wel they're a one way valve, fairly easy to fit and not expensive, but... My recall of Goretex is that it doesn't like saltwater, which clogs it a bit if I recall correctly, may be wrong and the technology may have improved, but a Goretex valve in a hatch cover probably wouldn't be a bad thing, do hatch covers leak anyway, I've never thought of them as totally watertight? ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: JimC
Date Posted: 09 Aug 17 at 3:43pm
| The hatch covers currently available, with rubber gaskets and the cover concealing all the fastenings, are airtight if well installed and maintained. The ones we used to get in the 70s, on the other hand, leaked like sieves. |
Posted By: Presuming Ed
Date Posted: 09 Aug 17 at 6:10pm
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Gore tex vents: https://www.gore.com/sites/g/files/ypyipe116/files/2016-07/PTV-Datasheet-Screw-In-Series-US.pdf  |
Posted By: iGRF
Date Posted: 09 Aug 17 at 8:22pm
------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: 423zero
Date Posted: 09 Aug 17 at 9:03pm
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Would a releasing one way valve work ? bake the boat in midday sun, valve allows air to escape, cool it in the water, no air can get in to relieve vacuum.
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Posted By: Rupert
Date Posted: 09 Aug 17 at 9:08pm
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Love those Gore valves. Don't own any airtight boats, though! ------------- Firefly 2324, Puffin 229, Minisail 3446 Mirror 70686 |
Posted By: iGRF
Date Posted: 09 Aug 17 at 9:21pm
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We had them in windsurfing boards, well boards that were built with 16gms foam and needed venting, around the turn of the century, an attempt to replace the screw valves that folk often forgot to undo. ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: maxibuddah
Date Posted: 10 Aug 17 at 7:09am
Goretex isn't one way though is it? I thought it was fully breathable while being waterproof. ------------- Everything I say is my opinion, honest |
Posted By: 423zero
Date Posted: 10 Aug 17 at 7:28am
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I was referring to iGRF's earlier post regarding non return valve, forgot to put quote, using phone.
Goretex 20,000 times smaller than water molecule, until it gets clogged, will act like air filter in car. |
Posted By: iGRF
Date Posted: 10 Aug 17 at 9:13am
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Yes a bit misleading my first explanation, it is of course one way for water, not air. A Test we used to show dealers and the public at shows, was to put your hand in a bucket of water, then place it in a Goretex glove (a good one) then place the gloved hand back in the water and leave it for a few minutes, eventually your hand will dry inside the glove.
Sold lots of Goretex gloves in my time. ------------- https://www.corekite.co.uk/snow-accessories-11-c.asp" rel="nofollow - Snow Equipment Deals https://www.corekite.co.uk" rel="nofollow - New Core Kite website |
Posted By: Cirrus
Date Posted: 10 Aug 17 at 10:42am
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I don't understand why all the complexity is suddenly needed - a 1mm drill through the centre of a hatch is all you need ... If you don't want it later for whatever reason a simple blob of glue or mastic on the inside can effectively remove it. Job done .... next. |
Posted By: maxibuddah
Date Posted: 10 Aug 17 at 11:51am
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It's technology ain't it mike? Got to have it. You don't need any gadget but you have them. Move with the times ------------- Everything I say is my opinion, honest |
Posted By: Cirrus
Date Posted: 10 Aug 17 at 12:17pm
It's technology ain't it mike? Got to have it. You don't need any gadget but you have them. Move with the times  And there was me thinking 'simplicity' needed championing when all that was really wanted was another techie and pricey solution to another 'non problem'. Still 'some' and their money are soon parted I guess ....  |