Drip, drip . . .

Grehan

Grehan

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Joined
11 Jun 2001
Messages
3,729
Location
Inland France + Oxon.
www.french-waterways.com
Little drip inside from around our cabin top dorade vent.
So, I removed the inside sleeve.
But . .
Drip isn't coming from the vent, it's a-creeping and a-seeping out from within the balsa core (which obviously has a hole cut through it at the vent position)

But where's it getting in?

Any suggestions for tracking the source of the problem?
Do I have to investigate every deck fitting for metres around?
The balsa is a bit soggy - is this a serious problem?

Help/suggestions very gratefully received.

Worried of Poole
 
Oh dear, of dear.

Tracking the source of the leak could take forever - it could be almost anywhere as capillary action will wick the water for large distances.

As for structural integrity - I wish I could be positive, but in truth it could be very, very nasty. The purpose of the core is to maintain a fixed separation between the two faces (GRP) of the laminate. To resist bending the force needs to be transmitted through the core to other skin - the distance between the two skins defines the strength. If the two skins become closer together the strength (moment of inertia) of the total laminate degrades.

The wet core causes a number of problems - firstly it becomes more easily compressible (think of the analogy of a dry piece of toast v untoatoasted bread) and secondly the balsa becomes more prone to failure in shear - neither of these are good.

What I cant tell you is how much of the structural integrity can return by simple dring out - I think you need good quality advce from someone who is well versed in cored composites.
 
Yes, it could be serious. I would suggest that you try and obtain a copy of "The Fibreglass Boat Repair Manual" by Allan H. Vaitses, Published by Adlard Coles Nautical, London. ISBN 0-7136-3520-7. See pages 77 to100 before paying for professional help - it being a good idea to know a bit about it before discussing with a professional.
 
I wouldn't worry about it at all at this stage. You can't carry out any repair whilst the core is wet so I would wait until next summer, remove the vent and let things dry out. You will need to identify the source and if it's obviously a deck fitting remove it and rebed it. The usual balsa repair is to drill a series of small holes and inject resin. But this is why I say wait until next summer.
 
Not good advice

This is a problem that will definitely not go away. Leaving it for a further winter (assuming the questioner is in UK) will do nothing but harm. And hands up all those who think that next summer will be blissfully warm and dry, to enable drying out a saturated balsa core. Exactly.

Get some specialist advice and take immediate action to prevent further water ingress. Even some tarpaulins will help.
 
Grehan, after the other replies you have had I guess you are not very happy. A friend of mine had this problem and did rectify the problem himself, but it took a lot of work.
Is the inner skin of the cabin top visible inside the cabin? Or do you have a separate headlining that covers it?
 
Grehan

This is a copy of an email from an american fourom of mainship owners.

Tom


Gentlemen,

I have recently replaced most of the core in my cabin top on my 1982 MK II. Prior to cutting into the top, I too had your basic tea party running down my side saloon windows. To drain the tea from the top, I removed the curtain track that is attached in the saloon to the top liner at the aft end of the saloon by the side windows and drilled weep holes where the track was. (Once the track is replaced it will hide repaired holes) I drained five...count em...five gallons of tea from inside the top. After the brown rain stopped (a couple of days in august heat), I placed tape over the weep holes and proceeded to cut the skin from the top side of the top and remove the core (see photos in files, photos under Cherry's Float). Once the core, skin replacement and repairs were complete on the topside, I removed the tape from the previously drilled weep holes, filled them with a thickened mixture of West System and Colloidal Silica and applied new tape to prevent the mixture from leaking out. After it cured, I removed the tape, sanded the repair carefully as not to extend my sanding past the width of the curtain track (not much to sand as the tape kept the area smooth) then reapplied the curtain track. No more tea!

Good Luck and Best Regards,

Pat Cherry
Cherry's Float
'82 34' MK II
 
Folks

Thanks so much for the advice and comments.
Well, I guess I should thank you . .

Yes, I'm in the UK (Grehan's at Port Solent over the winter, although not normally)
I'll certainly tarp over as soon as poss.
I should reiterate that the problem has very minor symptoms at this stage, but I'm now well and truly on my guard!
I will devote significant efforts over the winter, rather than just thinking this is just one of those run of the mill phenomena.

Thanks (seriously)
 
I've used moisture cured polyurethane resin (from www.cfsnet.co.uk) to add strength to a small area of wet balsa by drilling and injecting a number of small holes under the offending deck fitting after drying the balsa as best I could and re-bedding the fitting. It seems to have worked .. but I'm not an expert.
 
Im no expert but my last but one boat was a Pacesetter29 that I fitted out myself. Point is that it not only had a balsa sandwich deck but hull as well.

As you can imagine I was fairly concerned as to how this stuff performed.

I dropped a piece of sandwich in a bucket of water in 1984 and pulled it out in 1989 and it was in pretty much the same condition as when it went in (bar the slime).

Also in my experience most balsa sandwich is layed up in endgrain "tiles" and the laminating resin runs down between the tiles and should effectively seal one from the other, joining the inner and outer skins. So in theory at least a leak should not spread to far.

As I say Im no expert but this info my help you draw some conclusions.

Regards Nick
 
If you have not been before have a look on www.yachtsurvey.com.
A mine of information on the assorted little problems that affect cored grp boats.

Just hold tight dear it will not be so rough when we get round the corner,trust me.
 
Kontiki

It didn't work for Thor Heyerdahl. Kontiki was almost awash by the end of his trans-Pacific trip. I don't know how much resin runs down the balsa and I take your point that it will certainly help. However, there is a wealth of received information that balsa cores rot when wet.
 
Re: Kontiki

I think that a lot of problems come when the core is damaged by crushing ie. a bolt being put though without the laminate being closed or a hard point instaled.

The other thing is if the laminator has been mean with the resin and the endgrain is not saturated.

I cant remember if thor Heyerdahl's logs were green, or if he dried them, but I would guess that the water came in through the endgrain not the sides. Also the areas where the ropes chaffed.

I wouldnt be suprised if the water in this case is not going through the balsa but between the resin saturated balsa, and the laminate, where the two have become detached.

In my limited experience the resin soaks in about half a mm into the endgrain and should create a very complete seal, unless damaged, delamination causing a void is far more likely

Regards Nick
 
Balsa Rotting

I have seen a brown gunge running out from the saturated hull of a certain swedish manufacturer who recently changed to Balsa sandwich below the water.
By the way the boat was only 1 year old and was a right off - they settled out of court.

If thats not rot - i suspect it was anaerobic bacterial action......
 
Drip, drip . . .update

Haven't managed to get down to Grehan for some (very wet and windy) weeks. I was worried about what I'd find . . but everything's all ok!

It's certainly been wet 'cos rain's blown in through the door vents and seeped in through a deck cable gland, but the dorade vent area - and the surrounding cabin ceiling laminate - is as drizabone.
I'm going to take seriously and investigate the problem as has been suggested in this thread, and I've now covered the whole area with a tarp, but I am nevertheless relieved.

Thanks again folks.

I'm in the phonebooth. It's the one across the Hall
 
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