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Mike Adams

Best Method of sealing weedhatch

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Following a number of boats sinking I thought I would have a look at the weedhatch on a boat I have been renovating. The weedhatch cover height from the counter is only about 6" and there is a removable baffle plate at the base in line with the counter. It does not leak during normal operation although clearly it is not watertight. It is a long time since I had a boat with this arrangement. The hatch is not easily removable being bolted down with eight bolts. Now I have it apart there is some corrosion on the faces so now they are cleaned up there will not be a perfect seal. I am thinking of using some closed cell neoprene 30mm x 10mm to form a gasket. Would this be too soft? Any  other suggestions for a gasket material? Are most NB,s with a weed hatch fully sealed or do people hope that it never gets to the situation where the top of the weedhatch goes below water level.

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6 minutes ago, Mike Adams said:

Following a number of boats sinking I thought I would have a look at the weedhatch on a boat I have been renovating. The weedhatch cover height from the counter is only about 6" and there is a removable baffle plate at the base in line with the counter. It does not leak during normal operation although clearly it is not watertight. It is a long time since I had a boat with this arrangement. The hatch is not easily removable being bolted down with eight bolts. Now I have it apart there is some corrosion on the faces so now they are cleaned up there will not be a perfect seal. I am thinking of using some closed cell neoprene 30mm x 10mm to form a gasket. Would this be too soft? Any  other suggestions for a gasket material? Are most NB,s with a weed hatch fully sealed or do people hope that it never gets to the situation where the top of the weedhatch goes below water level.

 

I tried that and 10mm is too soft, I now use I think its 5mm sheet, I will check and get back to you

2 minutes ago, ditchcrawler said:

I tried that and 10mm is too soft, I now use I think its 5mm sheet, I will check and get back to you

It was 5mm and this is what I ordered https://www.ebay.co.uk/itm/202326666794

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I cut a piece from a camping mat and glue it on. Probably starts off 20mm thick. £5 from Millets for enough to reseal it every year until 2025.

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3 minutes ago, pearley said:

I cut a piece from a camping mat and glue it on. Probably starts off 20mm thick. £5 from Millets for enough to reseal it every year until 2025.

I started with bedding mat but I think that was much thinner than that, that's why I bought 10mm after I used it all up which was useless, the 5 mm is working OK, The bed mats I looked at were all bumpy finish, not smooth 

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I carry two large tubes of waterproof silicone sealant on board.

If I lift the weedhatch I peel off the previous coating.  After rummaging I squeeze another thick bead around the edge and clamp it back down.

Being a liquid when applied it doesn't need to be a spotless, rust free and smooth surface.

Once a tube is empty I buy another so I always have more than enough.

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I was talking to one of the boatyard staff on our marina recently and he told me about this guy who wanted his boat lifting out so he could clear the prop.  But you have a weed hatch, the engineer explained... oh I'm not touching that the skipper replied, I've got a really good seal...

 

I had a boat that whatever I did the weedhatch would not stay watertight.  I tried numerous sealing materials, had the lid sanded down, thinking it might be slightly warped I had it pressed flat and then had reinforcing strips welded to it... the damn thing still leaked, not really serious but I had to keep an eye on it and so annoying.   I reckon it's why those Wilson boats have that chute arrangement, so you can just forget about sealing it.  

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4 minutes ago, zenataomm said:

I carry two large tubes of waterproof silicone sealant on board.

If I lift the weedhatch I peel off the previous coating.  After rummaging I squeeze another thick bead around the edge and clamp it back down.

Being a liquid when applied it doesn't need to be a spotless, rust free and smooth surface.

Once a tube is empty I buy another so I always have more than enough.

And does that seal straight away?

Edited by ditchcrawler
speeling

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43 minutes ago, pearley said:

I cut a piece from a camping mat and glue it on. Probably starts off 20mm thick. £5 from Millets for enough to reseal it every year until 2025.

+1 on camping mat. Mine was around 10mm thick. A single sheet across the inside face of the top plate. Not a drop gets past.

 

Jen

  • Happy 1

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How do you work out if the seal is watertight if it doesn't leak when underway but only leaks if the boat sinks below the level of the top of the weedhatch? ie testing the seal for watertightness -not easy I think?

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Just now, Mike Adams said:

How do you work out if the seal is watertight if it doesn't leak when underway but only leaks if the boat sinks below the level of the top of the weedhatch? ie testing the seal for watertightness -not easy I think?

Can you go boating with the lid off then? Mine leaks under way when the seal is knackered, I don't wait for it to sink below the lid to find out

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Our boat has some pretty thin self-adhesive foam strip, I’d guess it started out at 2-3mm. No leaks.

Edited by nicknorman

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2 minutes ago, ditchcrawler said:

Can you go boating with the lid off then? Mine leaks under way when the seal is knackered, I don't wait for it to sink below the lid to find out

With a knackered seal, mine leaks when the prop is in reverse, but not when in forward. All to do with the relative position of the weed hatch and the prop. On my boat the weed hatch opens over the shaft as it exits the stern tube. A good place as this is where the rubbish tends to end up. Don't boat with the lid off. Boats can and have sunk within seconds when people set off after forgetting to put the lid back on.

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I don't have a weedhatch. Its not really much of a problem. You can pull stuff off with a short shaft, working most easily from a low bank.

Mike, if your weedhatch has 8 bolts rather than the usual quick-release arrangement, then I can well imagine you may be better leaving it untouched and using a shaft instead.

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Care is needed when replacing the lid, they rarely fit properly if not the correct way round. usually the cavitation plate baulks on something if wrong. Once certain its the right way round mark it with paint F for front or something.

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5 minutes ago, ditchcrawler said:

Can you go boating with the lid off then? Mine leaks under way when the seal is knackered, I don't wait for it to sink below the lid to find out

Yes there is a 8mm steel plate that drops into the base of the weedhatch and it is quite a good fit so no water reaches the top of the plate but I haven't tried it out on anything bouncy like the tidal thames

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3 minutes ago, David Mack said:

I don't have a weedhatch. Its not really much of a problem. You can pull stuff off with a short shaft, working most easily from a low bank.

Mike, if your weedhatch has 8 bolts rather than the usual quick-release arrangement, then I can well imagine you may be better leaving it untouched and using a shaft instead.

I don't intend to use it often but I did once(1978) get a log jammed between the prop and the counter on a previous boat below Tower Bridge and I was very glad of the weedhatch at the time but given the high speed traffic in that area now and the swell it creates I don't think it would be safe to remove a weedhatch down river now.

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Whats wrong with weedhatch sealing tape?????

 

Keeping the metal surfaces in good condition is important, a good back to bare metal job and then some epoxy. Make sure epoxy is 100% set before clamping the weedhatch down, and then open if everyday for the first week.

 

I have experimented with neoprene for making porthole sealing gaskets etc and have had mixed results, I suspect some of the eBay stuff is not 100% closed cell and gets waterlogged after a time, and does appear to go a bit sticky under compression so can disintegrate when taking things apart.

 

...............Dave

and if the weedhatch top really goes below the waterline then maybe get it raised with a bit of neat metalwork and welding, though don't worry too much if it does not meet the 10 inch clearance or whatever it is.

 

.................Dave

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19 minutes ago, dmr said:

and if the weedhatch top really goes below the waterline then maybe get it raised with a bit of neat metalwork and welding, though don't worry too much if it does not meet the 10 inch clearance or whatever it is.

 

I didn't know about this 10 inch thing - is that the same as outlets and openings in the hull? I can't raise the hatch because the steering quadrant (wheel steering) is only just above the hatch so there is not enough room to raise it.

Thanks for all the helpful comments. I think I will bolt it down with the 8 s/s bolts with a seal yet to be decided and only use the weedhatch in the most dire of circumstances and hope that this will be OK with a surveyor when a survey is needed.

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It all depends where you go boating. If you want to do Birmingham or Manchester etc then a quick release type mechanism would be much better than bolts, and should not be too difficult for a boat welder to fabricate.

 

Yes, I think the weedhatch now has the same "rule" as other hull openings but as long as the seal is water-tight then its not important, but I would be unhappy about a weedhatch always below the waterline under some conditions  (like with an empty water tank) due to the risk of a long term slow leakage, or the obvious problem if needing to open it :).

 

............Dave

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8 minutes ago, dmr said:

Yes, I think the weedhatch now has the same "rule" as other hull openings...

It does. But as with other hull openings it’s only advisory. 

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8 hours ago, David Mack said:

I don't have a weedhatch. Its not really much of a problem. You can pull stuff off with a short shaft, working most easily from a low bank.

 

 

If you can find a low bank you can easily stop at I guess that's ok. You'll be fine on most canals but I wouldn't fancy a fouled prop on a river with much of a current. Even if you drop an anchor what are you supposed to do? Fortunately I suppose most prop foulings occur on canals rather than rivers, but I suspect it would only have to happen once and turn into a difficult situation for you to change your mind about it not being a problem.

 

Personally I'd always want a weed hatch, they're just such a good idea.

Edited by blackrose

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1 hour ago, David Mack said:

I don't have a weedhatch. Its not really much of a problem. You can pull stuff off with a short shaft, working most easily from a low bank.

Mike, if your weedhatch has 8 bolts rather than the usual quick-release arrangement, then I can well imagine you may be better leaving it untouched and using a shaft instead.

I would suggest that the underwater profile of your back end is quite different to a modern leisure boat, likewise the location and shape of your stren gear.

 

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I'm finding this topic very interesting, and I think most of the posters are old maids!  I used to worry about my weedhatch seal, because of the doom and gloom on the forum. 

 

The thing that swayed my thinking was this year's BCN 24hr challenge.  On the final run to the finish, we had been up for 30+ hours and the last bolting down of the weedhatch didn't go as well as it should have!

 

Between Icknield Port and Oozell's Street Loop we managed to add 6" of water in the (rear) engine room.  We crossed the finish line with MrsBiscuits bailing the engine room out of the side hatch as fast as she could, and fixed it the day after ... @Mrs Tawny Owl was quite concerned about us when she heard!

 

I have learned that better seals are better, and that a tired BCN crew member chucking a neoprene gasket in the binbag because it was in his way and looked like litter does not help with water tight sealing!

 

The point is that if it leaks a few gallons, or even a few tens of gallons into your boat, it's not a problem ... AS LONG AS YOU KNOW ABOUT THE LEAK!  Sorry for the shouting, but if you are leaking gallons a minute into your boat and do not know it, it is going to sink! 

 

It took us 10 minutes to get from where the leak started to the finish line, and without the bailing out we would have sunk our boat.  We won't ever make that mistake again, because even as tired as we were, we knew that wasn't good.  Ankle deep water is a hint!  

 

What I am getting at is that even if you have done everything wrong - like we did! - you still have time to notice and to rectify the problem, as long as you are paying attention.  If you are not paying attention, then I believe the phrasing is :

 

"They that go down to the sea in ships that do business in great waters these see the works of the Lord and his wonders in the deep."

 

:D

 

  • Greenie 3

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If I had some sort of level-in-the-bilge indicator, I would have discovered my diesel leak before the full 46L got there. 

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