Split fuel tanks.

eupa · 10 March 2007, 13:48

Voila un probem.

I have two 55 gallon fuel tanks encassed in the hull under the cabin which is
bolted to the hull , it can be removed - but it would mean a lot of work.
Have just finished my yearly over-haul and put a usb camera down to inspect the tanks. Unfortunately , it revealed each tank has a 5 cm crack at the top of the seam.( This must have been when I dropped 15 meters into a black hole... The tanks are side by side. Access will have to be by cutting a panel in the deck of about 50 x50 cms to weld the cacks.. Is there a prouduct that you can use that could chemically seal the leaks( I am reminded of Holts
rad weld)- or is there a another way ( a rubber bladder??). I do not want to really go about cutting the hull as this could weaken it??

any advice would be appreciated, and somebody coming up with a brilliant idea gets 4 bottles of Chilean cabernet sauvignon 2003. Santa Helena.

jonathan

Pete7 · 10 March 2007, 13:53

No chance, if they cracked its because they flexed or moved and split the seam. Glueing them up isn't going to hold. Tried the sealant stuff on a 110 landie fuel tank once. Didn't work and had to replace the tank.

Rip them out and get new ones made.

Think codders has the same problem, since you both get on really well perhaps you could do a job lot

Pete

codprawn · 10 March 2007, 13:57

My problem is TOTALLY different!!! Eupa maybe you could use bag tanks - they work very well as long as you can get them in.

jwalker · 10 March 2007, 14:12

Quote:

Originally Posted by codprawn

Eupa maybe you could use bag tanks - they work very well as long as you can get them in.

Have you ever seen the back of a TIG weld? How long before they fret through?

I'm with Pete, there must have been flexing.

Pete7 · 10 March 2007, 14:32

Quote:

Originally Posted by codprawn

My problem is TOTALLY different!!!

I do hope so, but how do you know

you haven't looked inside the tank yet, but when you do you should see a vertical pipe going to the bottom of the tank. You could use an endescope to check were your fuel is leaking too.

55 gallons is a big fuel tank, and lets be honest BWM was know for high quality fabrications. Cheap tank perhaps or just lots of serious commerical work over the last 12 years means they are now at the end of there useful life.

Just replaced the ali water tank on Fly By for the same fault. 14 years old and at the end of its life, the ali corroded from the outside btw.

Pete

eupa · 10 March 2007, 15:43

55 gallons is a big fuel tank, and lets be honest BWM was know for high quality fabrications. Cheap tank perhaps or just lots of serious commerical work over the last 12 years means they are now at the end of there useful life.

Thanks Pete 7. 55 gallons is not that big.. They are some 14 years old and Stainless. BWM dont make their own tanks- so I do not understand where you are coming from. Yessir, I do stress the bloody boat a bit- but that's whats ribbing all about.Unfortunately, I think you are right- tear them out and put some plastic ones in.

Jonathan

codprawn · 10 March 2007, 17:45

Quote:

Originally Posted by jwalker

Have you ever seen the back of a TIG weld? How long before they fret through?

I'm with Pete, there must have been flexing.

Depends how they are done - bloke who used to have a unit opposite mine was a great tig welder - did loads of work for the chemical and food industry. His welds were smooth as a babies bum inside so that glass liners could be slid into the pipes and valves. The way they do it is to fill with Argon first.

codprawn · 10 March 2007, 17:46

Quote:

Originally Posted by Pete7

I do hope so, but how do you know

you haven't looked inside the tank yet, but when you do you should see a vertical pipe going to the bottom of the tank. You could use an endescope to check were your fuel is leaking too.

Pete

I haven't got a leak - grrrr..... I think the pickup pipe has moved or kinked - is this possible?

Nos4r2 · 11 March 2007, 11:22

Are the cracks in exactly the same places?

If they are I wouldn't weld up the crack, I'd patch it with a circular patch across the seam/crack so it shifts the stress points. Filling with argon works but the tanks will need flushing/washing out with detergent first.

Bigmuz7 · 11 March 2007, 11:31

Quote:

Originally Posted by codprawn

I haven't got a leak - grrrr..... I think the pickup pipe has moved or kinked - is this possible?

Yes .. I had a tank once where the flexible pick up pipe used to float

when the level dropped to about 1/3rd in the tank, and if you were in the rough stuff, bingo, no fuel, and engine cut out, just what you need in a force 6. I had to wire a heavy nut onto it to hold it down. Manufacturers shouldn't get away with poor design like that

Jono · 12 March 2007, 17:12

Quote:

Originally Posted by codprawn

Depends how they are done - bloke who used to have a unit opposite mine was a great tig welder - did loads of work for the chemical and food industry. His welds were smooth as a babies bum inside so that glass liners could be slid into the pipes and valves. The way they do it is to fill with Argon first.

...interestingly "Baby's Bum" is a colloquial expression, in welding terms, for a poor weld profile whereby there is sink/suck back in the centre of the weld bead causing it to have the profile of a "Baby's Bum"... so a weld that looks like a “Baby’s Bum” is considered poor….not a lot of people know that…

Penetration is properly controlled with weld prep profile, gap and welding speed/technique. ….

codprawn · 12 March 2007, 17:26

Bloody hell I learn something every day!!!

Aidan · 14 March 2007, 23:04

Hi Eupa,

Just thinking about your split tanks.
It seems to me that if both went, then the tanks were of iffy condition before they went. Did they go at weld section from corrosion or split weld.
If they went by corrosion, then where else need attention.
If the weld split, then it can continue to split.

Do you have photos of situation, I am thinking along the lines of stent but I think there seems little choice except surgery.

Maybe I am missing something so photos needed.

Aidan

Pete7 · 15 March 2007, 10:22

Quote:

Originally Posted by eupa

Thanks Pete 7. 55 gallons is not that big.

For rib tanks 14 years ago it was.

Quote:

BWM dont make their own tanks- so I do not understand where you are coming from.

Correct, they would have sourced the cheapest tanks to do the job. My point is they didn't use expensive fittings, they couldn't if they wanted to compete at the budget end of the rib market.

Quote:

Yessir, I do stress the bloody boat a bit- but that's whats ribbing all about.

Agreed, and those tanks have earned there money, time to replace with some nice new ones with lots of baffles inside.

Pete

Alan · 15 March 2007, 17:15

Quote:

Originally Posted by Pete7

lets be honest BWM was know for high quality fabrications. Pete

Oh Mr 7 you are so funny. The 1997/1998 interation of BWM, built by a chap in Bridport who I believe has since fled the country was not reknowned for high quality fabrications. Our DS21 split it's fibreglass underdeck fuel tank first time out - 40 galls of petrol sloshing around the hull/deck void is not an experience to be easily forgotten. The tank was replaced by a stainless steel one which of course involved cutting a dirty great hole in the deck. In hindsight we should have rejected the boat then but we were in the whole learning curve thing. Other things that fell off were most things screwed to the console, the A frame screwed into the deck with self tappers and the drivers pod seat. By the time we sold her all of this had been fixed with the help of people who gave a damn about what they were doing.

EUPA you have no real choice for peace of mind other than removing the tanks and replacing with new. Occupational hazard of a 14 yr old boat unfortunately.

Pete7 · 15 March 2007, 23:46

Oops, well spotted Alan, I seemed to have missed a little word out and completely changed the meaning. Stick not in the sentence. Interesting they tried fibreglass tanks, they also tried plastic tanks from a dubious source, which promptly melted when filled with petrol

Pete

bedajim · 16 March 2007, 13:59

If you have got to cut them out can you then make the hole into some kind of hatch nice frame to cover the cutout edges and stiffen the deck, waterproof hatch so it looks like it should be there?

James

Downhilldai · 16 March 2007, 21:24

Quote:

Originally Posted by bedajim

If you have got to cut them out can you then make the hole into some kind of hatch nice frame to cover the cutout edges and stiffen the deck, waterproof hatch so it looks like it should be there?

James

I'm yet to see a hatch you could get two 55 gallon tanks through

bedajim · 17 March 2007, 08:30

Quote:

Originally Posted by Downhilldai

I'm yet to see a hatch you could get two 55 gallon tanks through

One at a time

Jono · 17 March 2007, 09:39

Quote:

Originally Posted by bedajim

One at a time

Still be a 'uggin big hatch.. Ponder the size of a 45 Gallon oil drum...... then add 25%.....