Watery bilges!

[Feedman]

Brilliant forum, with so many interesting tips & tricks!

Last September, bought a mid-seventies Shetland 536 which needs cosmetic TLC. Has been on a trailer all this time, in the garden. Had a new canopy fitted to cockpit so is reasonably weatherproof yet I can't for the life of me, understand how after emptying bilges, they refill after a couple of days, whether it's been raining or not!

I have sealed all the tiny holes left by previous deck fitting and screws; have sealed with mastic the interior connection of the deck where it meets the hull section; siliconed inside & out, around the window rubbers. I have placed a crystal/granular dehumidifier within the cabin area and sealed the door and still water accumulates on the cabin floor.

I could understand how condensation might play it's part but using a Pela 6000 pump, I often get over 4lts out of the bilges in a week. I have read extensively how other Shetlands with the foam-filled double-hull, often fill with water but I have assumed that was during use, whilst IN the water!

Can anyone shed any light on where this water volume might be originating?

 

[cimo]

hello Feedman
obviously rain water. tried the talcum trick?
when you next pump out dry the hull interior as best you can & sprinkle talc inside the hull. around the lowest point initially. You should see the little river trails when you next look. work "upstream" with the talc until you find the source(s).
rgds
c

 

[Playtime]

I could understand how condensation might play it's part but using a Pela 6000 pump, I often get over 4lts out of the bilges in a week. I have read extensively how other Shetlands with the foam-filled double-hull, often fill with water but I have assumed that was during use, whilst IN the water!

Can anyone shed any light on where this water volume might be originating?

I assume you've checked all the obvious things like leaks in the freshwater system?

Do you think the foam in the double skin is getting saturated (with fresh water or seawater even) and then this slowly drains out later?

 

[Ubergeekian]

I have sealed all the tiny holes left by previous deck fitting and screws; have sealed with mastic the interior connection of the deck where it meets the hull section; siliconed inside & out, around the window rubbers. I have placed a crystal/granular dehumidifier within the cabin area and sealed the door and still water accumulates on the cabin floor.

It's amazing how much water can get in through a small hole. Years ago I was doing some work on the Jouster, and took off the genoa tracks. I though I had sealed all the holes, but I missed on 4mm one in the scuppers. When I went back to the boat after two days of rain there was something like 4 in of water in the flat bilges from that one hole.

 

[Feedman]

Watery Bilges!

Yes, thanks cimo, but the talc-trick was one of the first I tried and it was the reason I used sealant on the inside to effectively seal the outer upper-deck mould to the inner hull-mould. What I should perhaps try (a variation on a theme) is something like blue chalk-dust, as the inside GRP is beige and it's not that clear in the crevices of the boat, when trying to see trickles through pale or white talc!

Playtime, there is no freshwater system installed. It really is just a double-skinned, factory-filled foam hull, which hasn't been in/on water for almost a year! Other Shetland owners speak about the saturation of the foam between the skins, which is why I've propped-up the bow of the trailer in order to encourage water to migrate to the rear bilge for extraction. I just didn't expect so much accumulation!!

I'm beginning to suspect & agree with what Ubergeekian has said, which is why I guess I must have another bash with blue chalk-dust. I will be installing a vent soon but I rather fancied knowing beforehand that the envelope was watertight.

 

[vyv_cox]

Yes, thanks cimo, but the talc-trick was one of the first I tried and it was the reason I used sealant on the inside to effectively seal the outer upper-deck mould to the inner hull-mould. What I should perhaps try (a variation on a theme) is something like blue chalk-dust, as the inside GRP is beige and it's not that clear in the crevices of the boat, when trying to see trickles through pale or white talc!

Playtime, there is no freshwater system installed. It really is just a double-skinned, factory-filled foam hull, which hasn't been in/on water for almost a year! Other Shetland owners speak about the saturation of the foam between the skins, which is why I've propped-up the bow of the trailer in order to encourage water to migrate to the rear bilge for extraction. I just didn't expect so much accumulation!!

I'm beginning to suspect & agree with what Ubergeekian has said, which is why I guess I must have another bash with blue chalk-dust. I will be installing a vent soon but I rather fancied knowing beforehand that the envelope was watertight.

I would look again at your sealing actions. A few points that I notice from what you have said so far:
Sealing leaks from the inside is rarely successful. Check the joint at the outside, dig out old, hard, cracked sealant and replace with new.
Silicone sealant is not very effective, has poor adhesion, little strength and leads to all sorts of future adhesion problems. Use some decent marine sealant, Boatlife or Sikaflex.
Slapping sealant around the windows rarely fixes leaks. Give each in turn a good blast with a hosepipe, while someone else checks inside. Spray upwards as well as downwards, as windows is one of the places where water does flow uphill. If you find a leak take the window out and seal it properly.

 

[cimo]

yes - silicon is no more than a cheap gasket and requires compression between surfaces to have any chance of providing any sort of water tighness. much better to use an adhesive based sealer as per vyv_cox recommendation.

Just recall another method for tracking down leaks, although I have not yet had to employ this myself.

You'll need a vaccum cleaner with blowing capibility (or similar) to pressurise the the boat interior. mix some washing up liquid & water and "paint" it over all external seams/joints and thru deck fixings. You will need to seal off all normal openings with duck tape/binliners really well in order to generate suffcient overpressure in the cabin area (it will take a while to buildup depending on the vaccum you have, but it will get there). It may be a quicker route to identifying your leaks? probably more difficult to do this when checking the cockpit locker areas (how are the locker gutters looking?). just thought I'd mention it as an alternative.

good luck. can't beat a dry boat!
rgds
c