fuel tanks and electrics-All in one box

[JSP]

I know many Ribs have a fuel tank inside a console with electrics in there too.
But I need to know your opinion on this.....

Tank sits at the bottom of the console, it's vented and filled externally. 20-30cm above the tank there's the back of the radio, gps, ignition, switches etc.
Should I build a bulk head to separate the two or stick a vent in the side of the console and leave it as it is?

[PeterM]

Stick the vent in & have done ..........

BHG( the BIG Avon dealer down south) rigged mine this way & I have NEVER hear of a real life case of thier being a problem - by problem I mean big bang & fire etc.

I'm at 120 hours & no probs at all so far.

Anyone actually seen this happen first hand ?

Pete

Oh I've got the battery in the same console .........

[Leapy]

Originally Posted by Blackroady

Stick the vent in & have done ..........

John...I understand your concern. My previous boat had a 40litre tank sat next to an 85ah battery. Not ideal engineering practice.

But the positives are that petrol requires a very precise ratio with oxygen to ignite and permeation through the hoses is unlikely to provide that. A serious leak possibly would, but I guess you're managing the maintenance of the boat and are diligent about it, plus, and most importantly, you're aware of the risk and are prepared to manage it. Even if you're not, you still need a spark of sufficient energy and in the right place and at the right time. The odds are stacking up.

The world is full of installations such as you describe. Not only boats, cars too. A certain British prestige manufacturer used to have a 20 gallon tank sat next to and above a 100ah battery with no dividing bulkhead.

As Blackroady says "Stick the vent in and have done..." but then manage the risk with diligence

[chewy]

In an ideal world you would separate the two you'd also pay someone to do the work for you!

I built a bulkhead in mine as I had all sorts of ideas, batteries under the seat and fuel in the head of the console, I also wanted all the cables exiting the rear of the console. I ended up drilling a hole in the said bulkhead for my steering cable!

[Nos4r2]

Originally Posted by Leapy

petrol requires a very precise ratio with oxygen to ignite

It doesn't... Anything above 5% vapour is explosive from memory.

[chewy]

Originally Posted by Nos4r2

It doesn't... Anything above 5% vapour is explosive from memory.

The lower explosive limit (LEL) is around 1.4% by volume and the upper explosive limit (UEL) is around 7.6%. Above and below these limits, the fuel will not explode.

[Nos4r2]

Originally Posted by chewy

The lower explosive limit (LEL) is around 1.4% by volume and the upper explosive limit (UEL) is around 7.6%. Above and below these limits, the fuel will not explode.

Fair enough-it's a while since I read the figures.
Point is, it takes relatively little vapour by volume to be explosive, and given the 1000:1 liquid to vapour ratio it takes a very small spillage to reach that 1.4%.
The vapour is heavier than air, so without a vent at the lowest point you've got an explosive mixture sitting low down very quickly.

[JSP]

Thanks for the replies lads. Only thing with bulk head idea is I'll have to have the filler pipe and vent pipe going through it.

So an air vent at the lowest point?

[doggypaddle]

Originally Posted by chewy

The lower explosive limit (LEL) is around 1.4% by volume and the upper explosive limit (UEL) is around 7.6%. Above and below these limits, the fuel will not explode.

never mind the petrol, the H and O from the battery is explosive even when vastly diluted with air, so you need a vent in the top too as its lighter than air.

[JSP]

Forgot to say, Battery is in the double jockey seat.

What should I do?