new fuel tank

[WolfgangSeaLife]

I have read the May 2007 Practical sailor article but did not find the answer:
In 1998 my original aluminum fuel tank had corroded at the bottom due to bilge water contact (also the water tank).
So I replaced both with bladder tanks, custom-made in Holland, ordered through Vetus Marine. These tanks are used on airplanes and coast guard and navy vessels.
Definitely no corrosion, fitted easily. Easily removed and cleaned. I had the well carpet lined, 500 liter capacity for each tank. Disadvantages: No gauge (measure by the height to a certain degree). No baffling walls. The fittings are flange mounted that need inspection and leaks have occurred but were fixed easily by tightening the flange.
These tanks have lasted well without problems for 17 years, but now I detected a leak near a corner that appears to be a tiny almost invisible 1/8” cut. No idea how it could have been caused. No sharp objects anywhere. On a recent ocean voyage with a full tank and a lot of splashing there could have been some extreme stress in the area. The manufacturer recommended to use cargo straps over the tanks which I did not use. But since the cargo straps are not tightened when the fuel goes down and the bladders are attached with extension straps at the upper corners, the cargo straps would not have prevented stress from the corners.
I fixed it with Hyperlon adhesive and a patch from my AB inflatable.
Now I am afraid of another leak and am considering a new diesel tank, but definitely not aluminum.
The shape is a V-shape with a step.
Any advice?
Thank you
Wolfgang/SV SeaLife E43 Ketch

[Stonefloat]

Wolfgang ,
We too have vetus bladders for fuel
( used as 2 saddle tanks) and a main tank in the bilge that we just had made of 5055 aluminum from coastline tanks in Bellingham Washington . I too was worried about the corrosion issue but after a lot of research they were installed using strips of g10 glued on with 5200 to stand the tank proud and at slight angle to drain off any water that finds the top. We generally only fill the 15 gallon vetus tanks if on a long trip and use a transfer pump to move fuel to the new main aluminum tank.
I have much more peace of mind with a well secured rigid tank in place.
Cheers , Stonefloat


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[WolfgangSeaLife]

Surprise, the first user of a bladder I found.
Have you experienced any issues with the bladder?
I am still using it. It holds 500 l of Diesel.
Problem was no gauge and I could measure only by the depth of the top from the ceiling. This worked to 18" down, about 1/3 of volume. So I cut a flange though the top with an opening screw for measuring with a stick. That leaked a little fuel and I had to reseal it. But then the leak continued. It was not my screw but I fund a tiny invisible 1/8" cut 5" above one of the corner fastening straps. My only explanation is that I had filled the tank to really full to a bulging maximum and then went on the ocean in 6" seas where there was extreme stress on the material at the corner. I put a hypalon patch from my AB dinghy repair kit on it, which seems to hold well, but no one could tell me a proper repair procedure for Alcryn, the tank material. The navy sends theirs to repair facilities.
In the near future I will not over fill the tank.
But like you, I am scared of another tear. Never thought this was possible.
So, like you I am thinking of an aluminum tank again, this time well epoxy coated and raised above bilge water.
One problem I have is that the whole tank won't fit through the companion way. Endeavour had installed it before the deck. So I may have to get two half tanks.
I appreciate your thoughts.