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Posted

Wonder whether anyone could advise me on a boat I viewed today? It's a trad stern, and from a structural/watertight integrity perspective the weed hatch is inside the hull with a robustly clamped-down lid such that, if the lid were left off and enough water came through the hatch, the whole boat would flood. The engine's in the middle of the boat, so no possibility of a transverse bulkhead. I understand the implications of all this; just describing the layout to give some context for the next bit.

 

Either side of the weed hatch and maybe 6-12" forward of it, there are two air vents built into the side of the hull, one on each side of the boat. A recent survey describes them as 190mm above NWL; I measured them today at about 90mm above the actual waterline. Photo attached (the adjacent through-hulls are connected to things, so less of a concern). I believe the diesel tank is full, which may explain the difference between NWL and actual waterline, but are vents in this sort of location a common thing? Most of my experience is in boats that lean over, so I'm not used to any sort of opening below deck level that doesn't a seacock and a set of softwood bungs kept nearby.

 

The boat has a current BSS, but the relevant part of the BSS requirements (Section 10.7) only applies to hire boats, so this wouldn't have been in scope.

 

The purpose of the vents is unclear, it looks like they may have been part of the original build. Would sealing them cause any unintended issues?

20250201_151110.jpg

  • Greenie 1
Posted
3 minutes ago, Wafi said:

The purpose of the vents is unclear, it looks like they may have been part of the original build. Would sealing them cause any unintended issues?

 

What's on the inside?

 

I suspect this is a back cabin and the air vents do nothing other than substantially raise the risk of the boat sinking. Narrow boats tip over too under a wide variety of circumstances and with just 90mm of freeboard, I'd be welding those over before even taking my first trip. 

 

 

P.S. What are the two skin fittings for? I'd be checking those carefully for swan necks on the inside too, given the complete lack of risk appreciation demonstrated by the vendors. 

 

 

  • Greenie 1
Posted

Yes, the missing information is "what's on the inside of those vents.

 

What engine does the  boat have, or, at the least, is it air or water cooled?

  • Greenie 1
Posted
48 minutes ago, Wafi said:

Either side of the weed hatch and maybe 6-12" forward of it, there are two air vents built into the side of the hull, one on each side of the boat. A recent survey describes them as 190mm above NWL; I measured them today at about 90mm above the actual waterline.  

 

I good reason not to take an old survey at face value

Posted

Thanks for the quick responses!

 

I don't have a photo, but the vents lead into the void below the rear deck, which contains nothing of note apart from the weed hatch, bilge pump, back end of the drive shaft and stern gland. From a ventilation perspective, this space is contiguous with the rear cabin. The inside of each vent looks a lot like the outside, there's nothing connected to them; they're effectively holes through the side of the hull with louvres. One of the round through-hulls in the photo is connected to a bilge pump (currently no swan neck, but easy to add one), the other to a drain around the rim of the deck hatch (no swan neck required).

 

In the rear cabin there's a cocooned generator under the seat/berth. I guess this could be getting its air supply from the vents described, though there are plenty of other ways for air to get in. It's raw water cooled with a sensible water intake (with a proper seacock) and wet exhaust; I'm happy with the layout and integrity of these. I suspect the vents are original and the generator fairly recent, so I doubt that was their original purpose. The engine is in a traditional engine room forward of the rear cabin, water cooled with a skin tank.

  • Greenie 1
Posted
56 minutes ago, Peanut said:

I wonder, has this boat been overplated at some time?

 

It looks that way doesn't it?

 

Given how far underwater the uxter plate is...

 

 

 

Posted
6 minutes ago, MtB said:

It looks that way doesn't it?

 

Given how far underwater the uxter plate is...

 

 

Something Wafi might like to consider, if he still intended to buy it.

Posted

I am not particularly risk-averse but even I would be significantly concerned by that one!

 

Alec

Posted

At risk of being accused (again) of scaremongering, here is what happened to a boat whose 'vents' are too low when it goes on the river.

 

NB-Sinking-on-Thames-1.png

 

NB-Sinking-on-Thames-2.png

 

 

It was noted by the PLA that the vessel had been the subject of extensive overplating. Whoever had recommended the overplating had also recommended partly blocking off the engine room air jalousie on the port side as its bottom edge was considered even then to be too near the waterline. The following Figure 1 below shows the effect of the overplating and the number of persons seated aft.

The buyer of the MINI MOO bought the boat on the strength of a survey report provided by the seller. The marine surveyor concerned had estimated the height of the engine air intake jalousie from water level marks on the hull although the vessel had been out of the water for a considerable time prior to his survey. He had estimated the intake to be 200 mm above the waterline but when it measured after the salvage it was only 65 mm. The marine surveyor had covered himself with the caveat that it was an estimate only. In that particular case, when the vessel sank, no life jackets were on board and at least one person on board could not swim. The survivors were very lucky that nearby boats managed to pluck them from the water immediately. The fact that a marine surveyor’s report perhaps covers him with words such as estimated does not provide much comfort if bodies have to be pulled from the water.

  • Greenie 1
Posted
25 minutes ago, Alan de Enfield said:

At risk of being accused (again) of scaremongering, here is what happened to a boat whose 'vents' are too low when it goes on the river.

I quite like referring to that incident when people advise buyers to rely 100% on a surveyor's report as gospel, rather than interpreting it carefully - it goes to show that a survey doesn't always mean that the boat is safe. It is however the only narrowboat that's sunk on this bit of the tidal Thames...

 

I know South Dock marina fairly well, having done bits in their boatyard and I have a friend who has a boat there. It's a very tight marina to move around in (most people use ropes to get out!), and there's no space inside to take a boat for a test cruise. It's straight into the lock and onto the Thames, and if you turn left upstream you're into the busiest bit with the roughest water! Lots of RIBs charging around, Clippers racing back and forth and the big Citycruises trip boats which are slow but produce a decent wake.

 

Pretty nuts to not wear lifejackets. When Limehouse Lock was run by Aquavista, they used to advise you on this if you were to leave via there, but now it's under CRT they don't seem to care.

Posted
4 minutes ago, Alan de Enfield said:

At risk of being accused (again) of scaremongering, here is what happened to a boat whose 'vents' are too low when it goes on the river.

Thanks - not scaremongering at all! I hadn't read that report, but it's exactly the sort of risk that came to mind.

 

I've yet to find any evidence of overplating on this hull. It's not mentioned in the surveyor's report or the historical documentation on board; the hull thickness part of the survey shows minor pitting, fairly uniform across the hull, and consistent with surveys I've read for other well-maintained boats of similar age. None of that constitutes proof, of course, but it's the best information available at this stage.

 

I'm now wondering whether the difference between NWL and actual waterline is due, at least in part, to the boat having a full diesel tank in the stern and an empty water tank in the bow? I didn't think to look at the waterline level further forward, and I'm trying to figure out whether putting 3/4 tonne of water in the bow would also raise the stern a bit. That's at least something that can be tested for free without committing to a survey.

 

If that explained the waterline discrepancy, my instinct would still be to get these vents sealed if I did ultimately purchase this boat; even if they're further from the waterline in "normal" operation it feels like an unnecessary risk. In any case, it seems common sense that the boat should be safe with any configuration of full/empty tanks; you never know what might happen.

Posted

I wouldn't get hung up on the term NWL. Judging by the weed growth, the hull has been at that depth for some time. Those vents are too low, and from what you describe, unnecessary. Get them welded up.

Posted
32 minutes ago, David Mack said:

I wouldn't get hung up on the term NWL. Judging by the weed growth, the hull has been at that depth for some time. Those vents are too low, and from what you describe, unnecessary. Get them welded up.

 

 

I'd go further than that. Even if they are necessary, get them welded up. They are downright bloody dangerous that close to the waterline. 

 

Have new vents cut in the cabin wall above gunwale level if they turn out to have a purpose. 

Posted (edited)

Boats tend to acquire the odd hole for various purposes, particularly older boats which may have had engines changed and the cabin layout altered. The engine can be changed from raw water cooling to sealed coolant loop; the position of bilge pumps gets altered; sinks and showers are relocated etc. What should happen is that the old fittings are removed and the holes welded up. What often happens is that the internals are removed and the fitting is at best covered internally with a cap. We have just addressed a small fitting which was probably for a sink, eight bolts (four on each side) that nobody could work out what they had originally been for and the water outlet for a Bolinder BM15 that was removed from the boat circa 1980!

 

If you do go ahead with this boat, I would be looking over the length of the hull, both sides, and getting all such surplus holes capped off at once. I would also be looking at the vents being capped as either something the seller should get addressed or which should be considered in the price. There was a recent thread on here about another boat being purchased that had corrosion issues around a sink waste outlet and there are distinct parallels with your situation. I recall that the boat was being sold by Rugby Boats and @matty40s had some knowledge of the boat so may be able to point you at the appropriate thread - it's worth reading as it shows how a good outcome for all can be reached in this kind of situation. I can't remember the ID of the person who purchased the boat, but he would potentially be worth contacting if you are in the same general area, as he may be able to point you at someone who can provide a sensible quote for the work.

 

Alec

Edited by agg221
Posted (edited)
1 hour ago, cheesegas said:

I quite like referring to that incident when people advise buyers to rely 100% on a surveyor's report as gospel, rather than interpreting it carefully - it goes to show that a survey doesn't always mean that the boat is safe. It is however the only narrowboat that's sunk on this bit of the tidal Thames...

 

But the survey quoted said they were 100mm higher than they actually are, an old survey as I read it.

59 minutes ago, Wafi said:

 I've yet to find any evidence of overplating on this hull. It's not mentioned in the surveyor's report or the historical documentation on board; the hull thickness part of the survey shows minor pitting, fairly uniform across the hull, and consistent with surveys I've read for other well-maintained boats of similar age. None of that constitutes proof, of course, but it's the best information available at this stage. 

Was this a survey you commissioned or one the buyer has shown you ?

Edited by ditchcrawler
Spilling
Posted
15 minutes ago, ditchcrawler said:

But the survey quoted said they were 100mm higher than they actually are, an old survey as I read it.

Was this a survey you commissioned or one the buyer has shown you ?

 

Maybe mistakenly but I read it as a 'sellers recent survey' - it of course not totally implausible that the survey has been doctored with the addition of a '1' in front of the '90'.

(The risks of reading an earlier survey and a dishonest seller).

Posted
22 minutes ago, Alan de Enfield said:

 

Maybe mistakenly but I read it as a 'sellers recent survey' - it of course not totally implausible that the survey has been doctored with the addition of a '1' in front of the '90'.

(The risks of reading an earlier survey and a dishonest seller).

Who did that survey? Can you not contact them to clarify the situation? They would have kept a copy and have an interest as they are being misrepresented?

Posted

Correct - survey was commissioned a few months ago by the seller. I've no reason to suspect it was done (and provided to me via the broker) in anything other than good faith. A number of other waterline-related measurements from the same part of the boat that are all consistent, so I'm pretty sure the discrepancy is down to the assumed waterline at time of survey (with the boat out of the water) differing from the actual waterline now.

 

I don't mind getting another survey done if it confirms the boat is sound; what I don't want to do is spend money on a survey that reveals a significant issue which I could have found for myself.

Posted
3 minutes ago, Wafi said:

Correct - survey was commissioned a few months ago by the seller. I've no reason to suspect it was done (and provided to me via the broker) in anything other than good faith. A number of other waterline-related measurements from the same part of the boat that are all consistent, so I'm pretty sure the discrepancy is down to the assumed waterline at time of survey (with the boat out of the water) differing from the actual waterline now.

 

 

My guess would be that the sureveyor saw a freshly blacked boat, so he actually had no idea where the actual waterline was. He took it to be the uxter plate which is normal, but in your photo is shown to be 4" under water.

 

 

  • Greenie 3
Posted
1 minute ago, Wafi said:

Correct - survey was commissioned a few months ago by the seller. I've no reason to suspect it was done (and provided to me via the broker) in anything other than good faith. A number of other waterline-related measurements from the same part of the boat that are all consistent, so I'm pretty sure the discrepancy is down to the assumed waterline at time of survey (with the boat out of the water) differing from the actual waterline now.

 

I don't mind getting another survey done if it confirms the boat is sound; what I don't want to do is spend money on a survey that reveals a significant issue which I could have found for myself.

You might be able to find issues yourself but a survey would give you a good tool to renegotiate the price and/or pull out of the purchase with your deposit if necessary works cost more than a certain amount. Can I ask what the boat has been used for in the last couple of years? Has it sat in a marina or has it been cruised? If cruised, I'm surprised these vents haven't caused issues to the current owner. Which broker is selling the boat?

Posted
13 hours ago, MtB said:

It looks that way doesn't it?

 

Given how far underwater the uxter plate is...

 

40 minutes ago, MtB said:

My guess would be that the sureveyor saw a freshly blacked boat, so he actually had no idea where the actual waterline was. He took it to be the uxter plate which is normal, but in your photo is shown to be 4" under water.

 

 

I'm sorry, despite trying to read though the thread multiple times, I am failing to see any image that gives an idea as to where the uxter plate is sitting in the water.

Could somebody please direct me to the exact post that shows this detail.

Thank you.

Posted
2 minutes ago, alan_fincher said:

Could somebody please direct me to the exact post that shows this detail.

 

The photo is in the OP.

 

 

Posted
1 minute ago, alan_fincher said:

Could somebody please direct me to the exact post that shows this detail.

Thank you.

 

The post with the photo. There is no actual dimension, but looking at the weed growth and rusty/muddy area below the water, I would say the uxter plate being ABOUT 4" below the surface is a pretty accurate inference/estimation. In fact, as the lower portion of that area is not very distinct, it might be more than about 4"

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