Aluminium fuel tanks

[slimtim]

Its been discussed a little on hear before but not in great depth. I may be getting an aluminium fuel tank made up to my spec but was wondering about the pro's and cons. I know it doesn't work harden like ss so it shouldn't crack as easily but I am a little worried about the old galvanic issue when using ss screws to secure the filler plate to the top. How do you stop the galvanic corrosion? Can you just use some silicon gunk around the screws to seperate the metals? Will the silicon degrade in/contaminate the fuel?

How do I secure the tank down? Should it sit on something softish rather than straight on the deck?

Also, what about aluminium a-frames? If I had one made, would I be able to secure it with ss fastenings and use silicon to seperate the metals?

thanks in advance for the help.

Tim

[swginn]

I've got an ally tank and from what I've heard they are the business.

Will check out how the filler is fixed on mine and let you know. Will have to wait a while though as the RIB is in Baltimore and I'm in Cork for the next 2 wks studyin for exams . You could ask Pettal/Limeydal as they've got ally tanks as well.

[limeydal]

SlimTim,
not an expert on this ,but do have a little experience regarding my own tank.
Not sure why the filler plate would be bolted on as usually the pipework is welded on and just the fuel sender probe sometimes bolted on with a flange.
On mine the filler pipe/fuel take off and tank breather pipe are all welded directly to the tank and the hoses attach directly to them.

The fuel sender gauge was attached by a flange bolted on with SS bolts.
However I believe Barnett Marine now instal tanks with the tank directly threaded for the probe to eliminate problems.

Maybe on your tank you can get a thicker plate welded onto the tank to be tapped to accept the probe directly.
On mine although bolted on with a gasket ,I coated with a high tack gasket sealant that is unaffected by fuel.
So if all your take off pipes are welded and the tank is threaded;there would be no need to bolt anything to it.

cheers dal
You should not ,I believe us silicone.

[slimtim]

thanks for the responses guys. The reason I ask about aluminium is because my dad is doing some design work for a company that has an aluminium fabricating workshop and so may be able to get a tank made. It will probably just have a circular hole in the top to take a filler/sender plate that I already have.

The plate is a plastic one, the same as those found on the top of Plastimo fuel tanks, so I will be able to use a standard plastimo sender.

If I can't use silicon to seal the plate on, what can I use? Is sikaflex suitable?

Cheers

Tim

[Hightower]

Won't one of these do Tim, they're all plastic!



http://www.tempoproducts.com/2004/bd_fuel_tanks1.html

[slimtim]

I was going to get one of these after you showed me the link before I think? Trouble is, none are the right size/dimensions. In an ideal world, the fuel tank will fit through the hatch hole I will have in the front of the console, this way I can take it out without ripping out the console and it is easier to install. Hopefully dad will be able to get an ali tank made on the cheap....it'll solve a whole host of problems!

Tim

[Matt]

Re Aluminium & Stainless issue.
Have a look at zinc chromate paste, available from most good chandlers.

[slimtim]

Thanks Mat, I knew it was something like that. I will make some enquiries.

Cheers

Tim

[eksrae]

Make sure your sending unit has the ground clip on it. do not run the ground off your tank. I have seen alot of corrosion problems from this. As well I would use a gasket rather than paste to seal the sending unit. I never use pastes of any sort. Just proper gas teflon tape on the stainless screw. As limeydal suggest your fittings should be welded to your tank. The sending unit that threads in from my experience does not last that long but does seal well. Your standard tempo sending unit is your best option.

[Scary Des]

Tim, I don’t know what size tank you are thinking of but I would suggest that you think hard about the baffles and venting in the tank

Bad baffling will result in the fuel surging from front to back of the tank at speed and can have allsorts of funny effects It is worth considering horizontal baffles as well as vertical ones

Venting is important to stop a partial vacuum while the tank is in use and the vent should be somewhere high (out of the water) and safe away from points of ignition.
Equally venting is important when filling the tank, make sure that if you have a higher spot in the tank than the filler neck that you vent this possibly back to the tank

Oh and incidentally aluminium does work harden but, depending on how it is used, it can take more time Des

[slimtim]

Thanks guys. The tanks dimensions are about 400mm high x 240mm wide x 800mm long and at the moment I am having one horizontal baffle in the middle. This baffle will consist of a plate extends the whole height of the tank apart from 25mm above and below to let the fuel through.

The tank will not be filled by means of a seperate filler cap and hose, but by lifting my jockey seat, and filling from the cap on the plastic plate I have (same as those supplied on Plastimo tanks). The cap has a built in vent thingy so was just going to have this as the tank vent and obviously a small vent down low on my jockey seat.

Any problems with this?

Cheers

Tim

[Scary Des]

Originally Posted by slimtim

Any problems with this? Tim

I think you might need more baffles and do think about a filler neck
The filler neck allows you a bit more vertical height above the level of the fuel which helps to stop spills and also helps the breather to work. The last thing you want is fuel dripping out through the breather Des

[slimtim]

Sorry meant to say one vertical baffle in the centre, NOT horizontal.

Good point about the filler neck, it will however be a hassle to sort that out because I will need to make a recess for the filler cap and stuff.

Thanks for the help.

Tim