Fuel tank in main console

[whackywoody]

Hi, on my humber project I will be mounting a 120L fuel tank on deck but in the base of the following console shown in the photo. The battery's will be located under the suicide seat at the front of the console and the other wiring will be located in the upper end of the console above the fuel tank. Obviously I want this to be as safe as possible and am considering the following options:

1.) I glass in a shelf above the fuel tank and any wiring that is passed through the fuel tank area will be in trunking and with cable glands to seal entry and exit points. The fuel tank gauge/sender will be accessible via a 10" deck hatch

2.) Build a purpose box around the fuel tank and screws box to floor. Any cabling / fuel pipes out of the box will again have glands etc.

3.) Open to suggestions

Just wondering if anybody has had any experience of doing this and which option do you think is best?

Thanks

Gareth

[Hightower]

Providing you have a fill and vent tube permanently mounted on the outside of the console there shouldn't be any fumes inside the console to give you any problems in the first place.

It's also a good idea to fit ventilation slots to the upper part of the console, helps out with all sorts, condensation, battery fumes, fuel spillages/accidents/leaky pipes.

[Nos4r2]

You shouldn't seal the tank in too well-you'll have problems with expansion/contraction of the air in the box round it.

[whackywoody]

Thanks, I plan to put the fill and vent on the outside.

It's an old optimax engine so not sure the harness will be as thick as the modern ones. But I may run s 2nd 2" tube for hydraulic cables etc

Thanks for the input

[Nos4r2]

Originally Posted by whackywoody

Thanks, I plan to put the fill and vent on the outside.

It's an old optimax engine so not sure the harness will be as thick as the modern ones. But I may run s 2nd 2" tube for hydraulic cables etc

Thanks for the input

What year opti? If it's the 8 pin plug it's the same harness as mine.

[whackywoody]

Originally Posted by Nos4r2

What year opti? If it's the 8 pin plug it's the same harness as mine.

Its a 2000. If its the same harness is it the actual harness that's thick or is it because its got big connectors (as I'm thinking the connectors could be removed and refitted)

Thanks

Gareth

[Nos4r2]

Same harness.

The connectors are big and it's not really feasable to remove/refit them as they're sealed to the end of the loom.You'll have water ingress issues if you remove it, and if you take the ignition off to do it, you'll have loads of connectors in the electics. Not a good idea as they're all weak points.

I just measured the old loom for you (I had to fit a new one) and the plug is 30mm diameter with spiky pins coming out (though a coke bottle cap taped over them covers them nicely for routeing through).
The cable is 15mm diameter.

Bear in mind when I routed my opti cabling through the 2" outboard rigging hose, the hydraulic hoses didn't go through that (they come out of the deck somewhere else) and it was still tight.

[Nos4r2]

If it's any help, I routed my electrics through first. I think you're REALLY going to struggle (ie, it may be impossible)if you're still thinking of using 2" tube under the deck though. I'd forgotten I don't have the hydraulics through the same trunk when I posted about it earlier. With hydraulics through there it WILL be impossible.

Without hydraulics, improbable and an absolute bastard to work on/replace anything.

You'll risk damaging stuff as it goes through as well. You need at least 3", maybe 4" under the deck and really it needs to be rigid with smooth edges. You've got to get outboard control cables through it and they like to catch for a pastime.

<edit> You'll need to tape up the additonal wires on the outboard electrics plug to get it through as well, or if it gets stuck you may not get it back.

[whackywoody]

Originally Posted by Nos4r2

If it's any help, I routed my electrics through first. I think you're REALLY going to struggle (ie, it may be impossible)if you're still thinking of using 2" tube under the deck though. I'd forgotten I don't have the hydraulics through the same trunk when I posted about it earlier. With hydraulics through there it WILL be impossible.

Without hydraulics, improbable and an absolute bastard to work on/replace anything.

You'll risk damaging stuff as it goes through as well. You need at least 3", maybe 4" under the deck and really it needs to be rigid with smooth edges. You've got to get outboard control cables through it and they like to catch for a pastime.

<edit> You'll need to tape up the additonal wires on the outboard electrics plug to get it through as well, or if it gets stuck you may not get it back.

Thanks for your help with this one. I think you right I am now considering a 3" pipe. Not sure if I will put the hydraulics down a separate trunk yet? 4" is another consideration might need to think about soil pipe - LOL

[Nos4r2]

FWIW, I think my underdeck pipe is 4 inch and it's bloody tight. I might get an extra bit of RG58 down it if I really tried, but I'd rather not!

Whats in mine is....

RG58 for VHF ariel
an 8 core cable for a-frame/bilge pump wiring
Opti 8 pin loom
2xopti oil lines
2x35mm squared battery cables
2xhydraulic lines
Gear/throttle cables
ISo approved fuel line (it's quite thick).
Lazy line.

It's a lot of cabling and took a good 3 hours to get it all under there.

[whackywoody]

Now built the console ready for the fuel tank, please see pictures and explanations

1.) Photo #1 showing deck fill and vent point outside console

2.) Photo #2 showing inside top half of console and the back of fill and vent point. The boxed section has been sifaflex in but will also get fibre glassed on every joint and there is obviously another section of wood to add. This will therefore mean fuel pipes and vents will be sealed off

3.) Photo #3 showing inside fuel tank area. The wood shelf / divider has been glassed in and the two 32mm copex tubes have a tightened conduit and sifaflex as well. There is 4cms around the width, height and length to allow for expansion but don't forget there is a vent so not sure if tank will expand.

4.) Photo #4 showing conduit into battery compartment which is separate housed area to fuel tank as it came out of the fibreglass mould.

5.) Photo #5 shows self sealed fuel tank

Next jobs

1.) Main engine/steering trunk will come up through the fuel tank area. I will be using a CV boot type seal on the floor joint and upper shelf/divider I have glassed in

2.) Fit tank and pipes and finish off box section

3.) Fit electrics to upper compartment

As safety is at the front of our minds is there anything additional I could do, what do the manufacturers do?

I was thinking about putting two additional vents in the lower compartment / fuel tank zone in case there was a leak it would vent to atmosphere - not sure if worth doing?

Thanks

Gareth

[Nos4r2]

Looking good!

You'll need to put at least one vent in the compartment with the tank in, or air expansion will cause you a problem. Put it very low down where it can self drain of water as well, or you'll have water buildup problems and (if it leaks fuel) petrol fumes sitting in there. .

Is it just the main battery cables going through those conduits?

[whackywoody]

Thanks, I assume the vents (stainless) are effectively 1 way valves and will stop water getting in.

Yes the 32mm conduit is only for the battery cables.

Thanks again for your help and advice

Gareth

[Nos4r2]

Originally Posted by whackywoody

Thanks, I assume the vents (stainless) are effectively 1 way valves and will stop water getting in.

No. They need to be able to flow air both ways.

Put them somewhere water either won't get in, or where water will all flow out.Personally I'd put a drain into the bilge in there as well.

Basically, petrol fumes are heavier than air, and any enclosed/sealed space needs a vent or atmospheric pressure and temperature changes will cause you a problem. Hence needing vents at floor level.

[whackywoody]

Originally Posted by Nos4r2

No. They need to be able to flow air both ways.

Put them somewhere water either won't get in, or where water will all flow out.Personally I'd put a drain into the bilge in there as well.

Basically, petrol fumes are heavier than air, and any enclosed/sealed space needs a vent or atmospheric pressure and temperature changes will cause you a problem. Hence needing vents at floor level.

Sorry for being a bit thick but are we suggesting a hole (as air will flow both ways)

I have no bilge pump but do have a bilge drain at the rear of the boat do you mean therefore a hole in the deck to (in console) to allow water and fumes to drain away?

Thanks

[Nos4r2]

Yes.