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Old 28 October 2009, 19:27   #1
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Avon adventure 450 hull cavity

Hi
I have recently purchased a 2002 Avon Adventure 450 RIB which seems to be in excellent condition. However, when I undid the screw plug on the transom to the hull cavity about a litre of water ran out.

I just wondered if anyone knew about the design of these hulls and whether this is supposed to be a sealed cavity, or if not, where can water get in?

Cheers

John
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Old 28 October 2009, 19:30   #2
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It is supposed to be sealed. Is there any sign of cracking to the hull?
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Old 28 October 2009, 20:10   #3
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Thanks for the response.

External hull condition is mint, unpainted high gloss conditon with just a few minor surface scratches on bow and keel.

Nothing obvious on the deck area, though a few non-standard tie-down hoops have been screwed on in front of the console with no evidence of sealant.

I have yet to empty and check the forward anchor locker with sealed lid which is full ok loose kit - does the locker have a drain?

The overall condition of RIB suggests it has been well cared for and I would think that the 40HP Johnson is unlikely to have pushed it to design limits, though there is a hint of stress cracking to the gel coat at the top of the transom supports!

Presumably Avon anticipated a requirement to drain the cavity by fitting the plug - my Narwhal 360 doesn't have one - and I notice there is a new complete drain plug assembly in the spares box which seems an odd spare to carry!

Unfortunately, I wasn't quick witted enough to taste the water to see if it was fresh or salt which may have given a clue as to source.
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Old 28 October 2009, 20:27   #4
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Someone (sorry, I don't remember who) on here suggested filling the boat with water to an inch or so above the deck, then putting an airline into the drain socket and watch for where the bubbles come from. Don't you go mental with it now and end up blowing the deck off.
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Old 28 October 2009, 20:34   #5
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though there is a hint of stress cracking to the gel coat at the top of the transom supports!
thats possibly more worrying?
Quote:
Presumably Avon anticipated a requirement to drain the cavity by fitting the plug - my Narwhal 360 doesn't have one
its probably more common to have a drain than not
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- and I notice there is a new complete drain plug assembly in the spares box which seems an odd spare to carry!
Well, as anyone who has ever turned up at the slipway having left the bung in the garage will tell you - that is a good idea!
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Unfortunately, I wasn't quick witted enough to taste the water to see if it was fresh or salt which may have given a clue as to source.
Yes -if you search here you'll find other boats which commonly have some "leaking" and this is a common trick. I'm not sure how the construction of your hull/deck/anchor locker seal together but on some boats thats the culprit. I guess the other thing you want to understand is how quick it fills up. If it takes several days in the water to get 1L under there - it may not be worth worrying about (especially if you don't store it afloat)
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Old 29 October 2009, 04:48   #6
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HI JOhn - I have the 4m Adventure & while the void is technically sealed from new if you have the std Avon set up I'd expect some water may have found its way in either through the bung not being screwed in right , or via holes in the deck . I have all my cabling etc under the deck so a couple of big holes that while sealed up could leak a little.

Personally I'd not worry too much about 'smal' (I mean literally hairline) cracks in the Gel - it just doesn't flex as much as the fibreglass & having seen fibreglass/ gel Glider wings with Gel that would make you think they are about to fall apart, but then taken the gel coat off to find all is fine I'd be happy to ignore it.

Oh & I think the anchor locker is sealed with no drain ( tis on mine).
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Old 29 October 2009, 07:01   #7
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Thank guys for all your helpful comments.

The RIB will be kept ashore so no worries in the short term. Now I know there could be a potential problem I monitor water ingress when I get afloat.

I must say I like the idea of flooding the deck and carefully introducing low pressure air through the drain and looking for air bubbles, that should produce pretty conclusive results!

The captive drain plug assembly doesn't look too clever and I suspect the hull seal arround the fitting may not be perfect - perhaps that is why the previous owner had a complete new spare assembly (housing & captive bung)!

The stress cracks would be better described as hairline crazing and similar to those that have been on the Narwhal for the last 5 years and on other boats I have had, so I don't think they are anything to lose sleep over at this time, but I will see what happens once I get afloat and exploit the RIB's capabilities!

Cheers

John
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Old 29 October 2009, 07:27   #8
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water in the hull cavity has been a common issue with every boat I have owned from fishing boats and ski boats to ribs. No joint is perfect and the hull to deck one is no exception esp when three or four persons are bouncing about on it at speed. The deck is bound to flex and the joint is bound to have some porosity to it somewhere. When there is underfloor foam buoyance then this becomes a problem in the form of sodden foam and extra and excessive weight. Just drain the cavity as a matter of course.
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Old 29 October 2009, 10:09   #9
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Bungs themselves are a bit of a leak source. Best bet is to clart it in Vaseline before inserting it. (I'm going to regret phrasing it like that, aren't I?..... Bilges here we come.....hang on, we're talking about the bottom of the hull under the floor so are we there already......)

Anyway, I uysed to get loads of water out mine, a smear of your favourite petroleum jelly later and I now get more out if it;s been stored outside in the rain than I do after a trip.
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Old 29 October 2009, 14:29   #10
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I must say I like the idea of flooding the deck and carefully introducing low pressure air through the drain and looking for air bubbles, that should produce pretty conclusive results!
Unless the problem is with the drain bung.




or cracks in the hull
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