how to wedge an ally tank.

[Dignity]

I've now pulled out the underfloor aluminium fuel tank and need to do some maintenance before putting it back, there are 2 things I would like to do but not sure how to go about it.

The tank basically just sits there in the well and I would like to somehow use some wedges to secure it between the tank and the well as at the front end there are signs where the bottom corners are starting to wear through the floor with sideway movement. The rear end is where the fuel entry/exits are so it doesn't move here. What sort if material would I use.

The clearance above the tank in some places is mere millimetres, there is evidence where the tank has rubbed at times, this would occur in heavy seas which the boat has seen quite a few times. Would a sheet of neoprene work here, I have read where rubber products can accelerates corrosion and cause pinholes. What other material could I use, I was also thinking of some sort of cloth type material like woven fibrglass or kevlar but once again what are the issues.

[scottar]

You don't want anything that can hold moisture. Ideally you want a air gap below the tank (usually done by gluing strips of nylon or similar under the tank so water can't get between the strip and tank itself) but with the clearance mentioned it sounds like that may be an issue. It might be worth considering coating the tank in something in an attempt to stop corrosion. As for anchoring it in position, I would be inclined to squeeze a bit of sika down the sides in areas where you will be able to get a knife or similar later to cut it away if you need to remove the tank again. On a slightly different topic - fitted some gear to a 24 Ocean Angler for a client - wasn't too happy with Allison when the non anchored fuel tank slid back in heavy weather and snapped the through hull water pick up off . Lucky it had a decent bilge pump.

[Dignity]

Scottar, the well is tapered, and clearance at the bottom is about 15mm and at the top about 30 mm so sika won't do it, and at the front is similar. The tank appears to have sat directly on the floor and after 27 years or so has ground the glass to nothing and moisture has made a bit of a mess of the timber below (the 3rd piece ive found in a boat that's not supposed to have any). I'm investigating ways of somehow embedding nylon into this area but of course this would make the tank more prone to moving around which is why I'm looking to somehow supporting the tank from the side.

I did think of making wedges out of seaboard, I only have some pieces 20 mm thick, or something similar and facing them with neoprene. Was wondering if there was anything else I could use. But I'm still wondering if neoprene is suitable to have against alum especially if there's any moisture there, I'm trying to waterproof the area but I'm not sure of a 100% success rate.

[Fed]

Can you get some bits welded on to the tank while it's out?
(I have NFI what those extra brackets are for, one of life's little mysterys)

[Stressless]

I've glassed my ally tank in under the deck in my Haines rebuild, never to be seen again, I hope!!!

Used these to convince me it was the way to go:

http://www.yachtsurvey.com/fueltank.htm

https://www.youtube.com/watch?v=sAzpPO4Hn7I

[Chimo]

Long teflon strips similar to your cutting boards but narrow ie couple of inches wide is what Seafarer fitted under my replacement fuel tank.

I seem to recall one in the middle and one on either side. The intent is to allow any water to move down and back to the rear sump to be be removed as needed

As you will appreciate the idea is to allow an air space between the bottom of the tank and frp bed. The electric current fed to the sender unit and salt water seems to lead to the creation of pin holes or it did in my SS fuel tanks case.

Nothing more annoying than ULP dripping out of the centre rear bung holes when the intent was to allow salt water to exit while the boat was in the carport! Having an almost full fuel tank was another story.

Teflon is also the material used to separate the motor mounting bracket from the frp transom on my Vag too. At least teflon is not expensive and you can sit it on the frp bed after you repair ie fibreglass the damaged bed.

Cheers
Chimo




I wonder if you could also use teflon spacers to lock the tank into a fixed position?

[Dignity]

OK, so now it's off to Miles Plastics down the road for some plastic strips. The link Stressless gave was invaluable. I suspect the points of contact with the deck has been when the tank pops when being filled, it certainly does when I pressurised it to check for leaks. I'll put the endoscope down today for a look as possibly a baffle has separated and if so I'll get that fixed before I put her back.

On another note when I drained the fuel tank and took it out there was barely a litre of fuel left in the bottom and it was clean with no debris or water. I was surprised as I was expecting some crap. I had drained the tank once before as it was down to a very low volume and took the opportunity to try and have everything fresh but nOT know ing how much was left. Also if I ever run out of fuel, fingers crossed, I'll know it is EMPTY.

Edit. I will also get some lugs/brackets welded on the top to act as spacers.

Thanks everyone for their invaluable input.

[Dignity]

Oops, not the end of this story yet, cleaned the floor up and it was a spongy mess, no f/g over the ply, there was but I think over the years it got ground away. Fortunately not a big job,cut it all away, relaid but so itchy right now.

[Moejoes]

Sam, I bought a 2400 x 1200 x 10mm Neoprene

cutting board

( I think ) and cut it into 50mm strips and sika flexed them into the floor cavity.
I then cut about 8 hard wood wedges and wedged the tank into position.
Works fine and wont' go anywhere.

[Dignity]

Sam, I bought a 2400 x 1200 x 10mm Neoprene

cutting board

( I think ) and cut it into 50mm strips and sika flexed them into the floor cavity.
I then cut about 8 hard wood wedges and wedged the tank into position.
Works fine and wont' go anywhere.

Thanks Mojoes, now get back to your painting.😂😂😂
I have a roll of neoprene around 8 mm so will be using that instead of the nylon. Thats a coupleof days away as I have justripped out the floor as I hadn't really looked at it and found it less than in a useful state. All cut out, new floor in place using 2 sheets 450 gm chopped strand mat 1 layer cross ply mat followed by another layer 450 gm chopped strand. Polish up the tank and reinstall. By the time we're both finished I think it might be time to go fishing.

[tunaticer]

I think you mean polyethylene not neoprene. Neoprene is sponge rubber.

[Moejoes]

Yep, I'm up for that.
Just make sure there's no holes worn thru the bottom of your boat!!!!

[Dignity]

I think you mean polyethylene not neoprene. Neoprene is sponge rubber.

Neoprene also comes as a solid polycloroprene sheet or block, I just happen to have a roll of it about 100 mm wide by 8 mm thick, not all like the closed cell foam strips that you buy from places like Clark Rubber.

Oops just realised I think you were responding to Mojoes post.