Fuel tanks, under deck or above...

[chewy]

Still looking at what to do with the tanks on my 21. I have two stainless tanks that are made for the RIB but my only concern is that if I have problems in the future then the deck will have to come up.
The fillers will come up next to the console, I can fit an inspection hatch above the tank fittings and another at the stern to get access to the lines and through deck fittings.
Usually the deck on the Atlantic is screwed down but I'm going to screw it down and glass over it so its watertight and it seems a shame to run the fuel lines through it.
The only other solution apart from a big tank on the deck is a couple of Mr Tilley's flexible "race" tanks strapped on the tubes.

Discuss.....

[HUMBER P4VWL]

Above. Easier to check level, easier to change, easier to fill, just easier. Unless you want pure distance. Then go under deck and over.

[chewy]

Cheers fella, next question is where to put them if I don't use flexible ones?

[Turbodiesel]

Under the deck with some good fuel filters!

[chewy]

So apart from a hatch over each tank for access to fittings and on at the stern would would recommend anything else?
There is two fixing points at either end, I also want to bed them into something, is sikaflex ok for this and if so which one?

[Polwart]

Chewy, I would go under. If at somepoint they develop a fault in the future and you can't fix it without major expense / time&effort then you can always revert to "on top" tanks. Once you've glassed that deck in you can't really decide they would be better down their afterall...

[Nasher]

Chewy

Under gets my vote, the weight is then low down where it works best, and you save deck space.

For some reason I noticed that a lot of RIBs at the Southampton show this year had large removable panels in the deck to get to the tanks.
I’ve not noticed this before, which is either me being blind or the manufacturers are now taking a different approach.

All of them were screwed down, and in some cases Consoles, seats etc were screwed down over the top of the join, so would also need to be removed to get underneath.
Obviously unscrewing stuff and a bit of faffing around is preferable to cutting and re-glassing.

If I can ever afford a new boat it’s something I’d build in from the start.
If you are doing major surgery anyway, why not build some extra strength in around the hole and have a removable panel.

Nasher.

[GordyP]

Can you not have a similar set up to the Arctic where the top of the under deck tank is flush with the deck? I can send you some photos of mine of you like.

[jyasaki]

Originally Posted by Nasher

For some reason I noticed that a lot of RIBs at the Southampton show this year had large removable panels in the deck to get to the tanks. [snip] All of them were screwed down, and in some cases Consoles, seats etc were screwed down over the top of the join, so would also need to be removed to get underneath.

That's how mine is set up, though it's an aluminum hull. There's a roughly 2.5' x 7' plate screwed down, then the console is mounted over the rear part of that. Though it allows access to the tank (theoretically, anyway), it would be a major PITA to actually get to it. As you say, still better than having to cut access to it though.

jky

[wavelength]

for me-above in the consol. We have a 90litre in there fits fine. Can dip it to see what is actually in there, the volume is stacked vertically in a column, if ya see what I mean, so there is less surface area. Which helps as the level gets low. The CofG may be higher but it doesn't move as the boat changes trim angle, or move violently to the back as it can with a shallow underfloor tank when the boat is launched over the side of our particularly unpleasant slipway. On long trips we have two extra 30litre portable tanks that are handy for balancing the boat and to take to the filling station when we get to a non petrol marina.