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gumb01
09-03-2008, 03:54 PM
Im having an underfloor fuel tank made for my tinnie and have come across a few hurdles and i was hoping someone onboard could steer me in the right direction. Are there any advantages/disadvantages when it comes to using aluminium over stainless? (obviosly ali is much cheaper than stainless) Does the device that connects the fuel hose to the tank have to be on the top of the tank? My tank capacity could be greatly increased if i was able to mount the connection device on the side of the tank. If anyone has any other hints or tips they are willing to share in regards to under floor tanks, the input would be appreciated. cheers

Roughasguts
09-03-2008, 04:18 PM
If you have an under floor fuel tank make sure it has a 'T" piece in the fuel line and a tap with enough hose on it to get through the rear bung.

Trust me you will need this when you have to drain all the old stale fuel out of the tank.

I don't see any reason why the fuel conection should be on top of the tank.

But just having said that mine are. And it did spring a leak a while ago and if the conectors where down the bottom of the fuel tank when I got the leak the hull would fill with fuel I suspect.
And not just weep from the top and be easily repaired while on the water.

So yep I think there maybe a reason.

Any_Weather
09-03-2008, 04:23 PM
Hi Gumbo, mate I dont see any disadvantages in using aluminium over stainless at all. Obviously the aluminium used would be quite a bit thicker than the stainless that would be used but would still be cheaper I would expect. The fuel line suction pipe can be mounted anywhere on the tank so long as the end of the pickup is close to the bottom of the tank for obvious reasons (and probably nearing the rear of the tank so when the boat is planing with the nose up a bit, there is fuel still available when the tank is nearing empty). The breathers are the most important part of a fuel tank and really do need to be at the highest part of the tank. I usually try to put 3 breathers in the tanks I have made, usually 1 each side at the front and one in the middle at the back and dont have any dramas. Be sure to get baffles put in when getting it made to stop the fuel slopping eccessively. Just reread your post, were you talking about the fuel filler hose? If so, you can probably fit it in the side of the tank if you must so long as the tank is well vented but I would expect it to be quite a bit slower to fill ( I may be wrong here though).

Lee

INTIMIDATOR
09-03-2008, 04:24 PM
Hey gumb01
If it's a glass boat go the stainless.
Sounds like your talking alu here so; the device that connects the fuel hose to the tank is called the pick up so if that's the way you want to set it up it still needs it's feed from the botton of the tank.
However if your fuel line comes lose for whatever reason the tank will empty into the hull:-[
Worth a mention is the fact you will also need a breather on top of your tank that is usually run to the heighest point possible on your transom.
You simply cannot have an air tight tank!!!
Have you decided how your going to fill the sucker up, as most gunnell fill tanks are pig's to fill,deck fill works better if possible!
Hope this is a little help
Cheers Payney;)

gumb01
09-03-2008, 05:12 PM
Hey Any_Weather,
Thanksheaps for the info. Can you please explain baffles to stop the fuel slopping. Are these just verticle panels in the tank?

Hagar
09-03-2008, 05:26 PM
G'day Gumbo

I had a custom alloy tank made for my glass hull and it's been great - no problems . All previous advice is good . Baffles usually consist of just a rectangle with the corners cut off to allow fuel to get past but not slosh too badly that is welded into the tank during construction . At least two in my opinion . You can have the outlet on the side but have it bent so the fuel line is connected up high as already mentioned . Other tips - buy a good large sized filler connection if it's not a gunnel filler setup that has an O - ring seal and room for the servo fuel pump spout . Make sure they use the right marine grade aluminium .

Chris

snelly1971
09-03-2008, 06:49 PM
I am currently having a SS one made for my boat, it had to be made to survey as well...tank diam is 900 x 900 by 500 high....Aluminium is ok as well but they preferred SS, One of the pluses of using SS was that tank fitting are available in SS but not Alloy...My cost alone just for materials at cost price was $2700 + GST...2 baffels installed with an emergency fuel shut off as well

Mick