Keel-based fuel tank repair

[dtynan]

I'm looking at a Hallberg Rassy which seems to have a leak in the fuel tank. The one in the keel. I haven't actually seen the boat yet, so consider this pre-research!

Apparently the leak is about a quarter of the way up, so the tank is good for 30 litres. The first thing that makes me wonder is how did a leak form in the tank at that spot? Was it a hard grounding, or is there corrosion right through and this is the first place where the corrosion has gone right through the tank wall or seam?

More importantly, exactly how hellish of a job is it to remove the tank? The engine would definitely have to come out, and I seem to recall that 'Rassy's have a fibreglass cover over the top of the tank. It might be easier to open up the keel around where the leak is, unless (as per point #1), this is the first leak to make its way through the tank wall, and many more will follow.

I guess I could just isolate that tank completely, and switch to the 90L tank instead, but it seems a shame to lose 150L of fuel capacity.

Has anyone done this? Lifted the tank out for repair/replacement?

 

[pandos]

Is this an old 352? If so, there is a series of YouTubes of a guy dealing with this very issue.

It is unlikely to be from a grounding as this is at the back of the boat and there is a sump in front of the tank.

Your suggestion of using another tank and ignoring this one is definitely an easier option. It would be madness to try to do this from the outside.

How many trips will you ever make that requires more than a 100l of fuel. For those rare events you could add a few Jerry cans...

 

[dtynan]

Thanks for that! I did do a few searches and didn't find anything. Will watch those this evening.

I hear ya on the whole "who needs 240L", especially seeing as it's a sailboat, and we're supposed to use those big white things to move us forward. But some day, on some long and windless passage, I'll end up wishing maybe, just maybe, I shoulda, coulda, woulda...

 

[Daydream believer]

Just a thought. If the tank had been left part full for long periods at the same level with a large quantity of water in the fuel one might ask if a seam of water may corrode the tank. That tank may not have been used if it had been contaminated. Say by inadvertently filling with water.

 

[Whaup367]

If it's a 352 (as seems likely from the tank sizes and configuration described) then this link is a good place to look for info, I believe:
https://www.hr352freyja.app/

Including links to pictures of another owner who replaced his keel tank by removing it though the keel.

Looks like a big job to me, he suggests there are two approaches- removal through keel or by taking the engine out & dismantling the galley... a fair bit of work, unless you expect to have to remove the engine for some reason, anyway?

Might be possible to drop a smallish flexible tank into the accessible section of the existing one- if the baffles are evenly spaced that might get you 50l or so? Not ideal but a useful addition to the 90l secondary and one that should prevent further diesel leaking into the bilge. Depending on your plans, you could plan to replace the original tank if & when the engine needs to come out?

 

[dtynan]

Just a thought. If the tank had been left part full for long periods at the same level with a large quantity of water in the fuel one might ask if a seam of water may corrode the tank. That tank may not have been used if it had been contaminated. Say by inadvertently filling with water.

I did wonder about this, but diesel is lighter than water so you'd expect the water (and the corrosion) to be at the base of the tank.

If it's a 352 (as seems likely from the tank sizes and configuration described) then this link is a good place to look for info, I believe:
Hallberg Rassy 352 Freyja - Maintenance & Upgrades

Including links to pictures of another owner who replaced his keel tank by removing it though the keel.

Looks like a big job to me, he suggests there are two approaches- removal through keel or by taking the engine out & dismantling the galley... a fair bit of work, unless you expect to have to remove the engine for some reason, anyway?

Might be possible to drop a smallish flexible tank into the accessible section of the existing one- if the baffles are evenly spaced that might get you 50l or so? Not ideal but a useful addition to the 90l secondary and one that should prevent further diesel leaking into the bilge. Depending on your plans, you could plan to replace the original tank if & when the engine needs to come out?

Yeah, I don't really want to have to remove the tank either with the engine or by cutting open the keel. If it were a small hole, making a 10cm hole in the keel might be OK, but I'm thinking the best approach is to ignore it. Use the 30 litres below the leak, or just switch to the 90L port-side tank.

Thanks for the Frejya link. I'd actually seen that web site but hadn't scrolled down to see the info on the tank. It's comforting to know it's relatively common. It used to be with car radiators, you could dump some low-melting-point solder in there, and in theory, it would weld your radiator holes. I don't remember that ever working for me. A pity they don't have something similar for fuel tanks. Something along the lines of "Completely empty your tank. Now fill it with Compound "A" for 45 minutes. Use a pump to remove all of Compound "A", (which sets when in contact with stainless steel). Refill your tank, and hey presto!" Maybe I invented the solution and all I need to do is patent it, and find a lab full of chemists who'll actually make it, sell the company, and buy a new HR instead. Yeah, that definitely sounds easier...

 

[Whaup367]

Had a look at the HROA forum for info (if you buy the boat, it might be worth joining) but didn't find much more information, however there's a link on there to the fb (& youtube) page of another 352 tank replacement on "Wanda":

A boat called Wanda

...from the owner (2017). In the post there he makes reference to the PO of this boat installing a small aluminium cylinder to take the filler from the secondary and the pickups for the services within the main tank. Similar to the idea of using a flexible insert but probably lower capacity vs. more robust.

I don't know how your tank fillers are set up: I've seen reference to having two deck fills but that presumably doesn't preclude having a single set of take-offs in the main tank with the secondary used to top it up rather than having separate outlets? On our 36 there's a single deck fill that goes into the upper/secondary and the transfer pipe gravity-drains into the main when open, all pickups are off the main tank, so the fix with the cylinder would allow the upper tank to operate on it's own, with the cylinder being a sump & take-off point. The interconnecting hoses would need to be perfect, as they would always have fuel in them instead of just when transferring.
On the 36, there's a similar setup (with different plumbing) for the water tanks. Indeed, the space used by the upper water tank on my boat could be re-purposed to act as additional fuel storage if that was more useful than the additional water capacity. If your 352 is similar that might be possible (but I think the 352 has a single 300l freshwater tank as standard, rather than the split setup on the 36?).

Edit: I see the youtube for Wanda is linked above: apologies, this post probably adds nothing.