Under Floor Tank in tinny

[Lancair]

After having to cutshort a few fishing trips due to fuel shortage and lack of suitable sapce to put a live bait tank, I'm considering an underfloor fuel tank. Only problem is itll have to be custom made as there isnt enough space to fit a ready made tank but I reckon a custom tank will give the capacity I want and free up the space in the rear under the casting deck for a live bait tank.

Are there any rules re custom tank construction ? What materials can a tank be made from ? Any points to consider other than breather, filler and outlet points ? Are baffles worth it ? Considering it would have to be a tank running across the boat under the floor and between the ribs, possibly 2 tanks joined with a large ID pipe in the middle to get the capacity I want. (Around 40-60 litres would be ideal). I was thinking without baffles to slow the cross flow in a lean as it could get heavy on one side very quickly. (aircraft have them to stop slosh and weight transfer occuring rapidly)

Thanks.

Andrew

[Luke G]

Take it into any good aluminium welder and he will knock one up quickly. They should build baffles into the tank anyway and get it tested. Take the boat to them and show them what you want done.

Cheers

[Chimo]

Here you go

Cheers
Chimo

Guess what :) gave me for Christmas? A nice new fuel tank for the Express. Got it off Phil this arvo. Quality craftsmanship...... pics are at this thread.... http://www.ausfish.com.au/vforum/sho...=142915&page=2 (http://www.ausfish.com.au/vforum/showthread.php?t=142915&page=2)

cheers, HR ;)

[Ally Jack]

Lancair,

I put a 60ltr stainless cruisetank under the floor in my 445 Allycraft. Bias boating has them.
Filled it thru the floor, ran the breather up and along under the side deck.

Ally Jack

[CreelReaper]

Hey lancair,
How big is your boat mate and is it fibreglass or aluminium?? A lot of what you will want to do will depend on how much freeboard you are willing to sacrifice by having to raise the floor.

One point you might like to consider also is how much flex the tank will give to the hull between the ribs. It might spell disaster with fatigue cracking over time.

For mine if it is a 'tinnie' I would be looking at putting in a nose tank that would fit snugly in front of the front thwart and shaped to fill the area beneath the seat also. I am sure you would have to have baffles to decrease the movement of the fuel. I believe that aluminium might not only be a fair bit cheaper than stainless but is more easily shaped to contour to the intended area you want to put it.

Shane

[cormorant]

Lancair,

I put a 60ltr stainless cruisetank under the floor in my 445 Allycraft. Bias boating has them.
Filled it thru the floor, ran the breather up and along under the side deck.

Ally Jack

What clears the bilge air after filling the tank.

The problem is not only with a tank breather itis that when filling all the fuel vapour overflowing and going into the bilge. I hope you don't smoke as if that filler isn't sealed to floor or you have abilge blower you are stitting on a bomb waiting for a spark.

If you are using a portable tank it should be out of the boat to fill to stop vapours or overflow accumulating in the bilge.

Portable tanks have a lot of advantages in regards to keping fresh fuel

There is Australian standards for tank , design construction and fitting in regards to survey. Mostly common sense so if you get one built it done by someone who knows the standards and can quote on that

[cbs]

What clears the bilge air after filling the tank.

The problem is not only with a tank breather itis that when filling all the fuel vapour overflowing and going into the bilge. I hope you don't smoke as if that filler isn't sealed to floor or you have abilge blower you are stitting on a bomb waiting for a spark.

If you are using a portable tank it should be out of the boat to fill to stop vapours or overflow accumulating in the bilge.

Portable tanks have a lot of advantages in regards to keping fresh fuel

There is Australian standards for tank , design construction and fitting in regards to survey. Mostly common sense so if you get one built it done by someone who knows the standards and can quote on that

Bingo! (Boom)

Freestanding underfloor petrol tanks can be a bomb waiting to happen. I can recall a couple of explosions from petrol to hit the news in the last couple of years (VIc? and one at sanctuary cove)

Take a look here http://www.nmsc.gov.au/documents/NSCV/PARTC5A.PDF under fuel systems for fuels having flashpoints less than 60deg. Chapter 4.

You will note that they require a seperate vented fuel tank spaces to prevent buildup of vapour. Construction info there too.


cbs

[Flex]

I took my 4.5m seajay to a aluminium fabricator in brissy. for $450 he made me a 75l fuel tank for the bottom of my boat, made to full Aus standards/tested etc. All I did was install the fuel line and breather(which is deadset easy)

A fabricator will make one to fit your boat, instead of buying a premade

[cormorant]

A lot of fabricators will makes tanks and even make them to the standards but won't get involved with fitting them as it isn't just a case of slipping them in. This especially applies to tanks with fillers that allow vapours to enter the boat or bilge.

Have seen amnufactured boats that in my mind don't comply and are dangerous as portable tanks can't easily be removed for filling.

Yeah I know it isn't going to blow up every day but I wouldn't want to be around when it does on dry land let alone on the water. It does happen and a lot of people get away with it

You can just about forget insurance as well if shit hits fan and someone on your boat gets hurt.