Retro-fitting an underfloor tank

[Thud]

G'day all,
I'm toying with the idea of fitting an underfloor fuel tank in a Haines Hunter 445F fibreglass centre console, but I don't know where the stringers are located, therefore can't work out the best location. Is there an easy way to find out how much room I have under floor, and where it is located? Would a "stud finder" work to locate stringers or is there a better way.

Cheers,
Tim..

[blaze]

I think if you are going to go to the exspense of under floor tank you will need to have it made perfectly, so the only sure way is to cut out the floor and have it made to suit. Mine is located at mid ship
cheers
blaze

[NQCairns]

Hi Thud, this might sound weird but you could use a sounder, the transducer will give you a pic of whats down there? While playing with my first one it did a great job of finding what was inside of a door and the garage walls.
A plastic hammer tapped on the floor should find the extra hard spots where the stringers are up against the underside of the floor (might find rot also? ). Iff your bung hole is in the middle a piece of wire pushed up there should hit the middle stringer if it has one The middle stringer may only be half height and not meet the underside of the floor. Good luck. nq

[peterbo3]

Thud,
How much extra fuel do you want to carry? Could be a very expensive job. 2X25L carryon plastic fuel tanks with fuel line fittings would be cheaper. A larger plastic tank (60L?) is also available.
If you really want to look under the floor cut a circular hole of a size that a heavy duty inspection cover can be fitted to.
If you pull out of the job you will have caused no damage to your floor & will be able to ventilate your underfloor area.
I would contact Haines first as there may be sealed buoyancy chambers underfloor.

[Thud]

Thanks for the input guys.
I'm on leave at the moment so been a bit slack getting on the net. Too busy fishing and stuff... it's a real problem
The reason for the idea is that I travel some serious distances for a small boat and carry 75 litres of fuel in portable tanks (3x25L) in the back. Plus two batteries and an esky all toward the stern AND I've just upgraded to a 60HP from a 48. Serious weight distribution problem so I'm looking at solutions that don't take up any more room.
Shifting the fuel load up under the console seems like a good idea if it can be done. That would put it midship like Blazes' and would free up some room down the back. I also wouldn't ming carrying another 15-20 litres)
I have done a bit more research and think I have a midline stringer from the bulkhead aft, but still need to check forward of that point.
Peter, I like the idea about cutting the hole for an inspection cover, and will also try NQs' sounder trick. (didn't think of that)
Blaze, did you have your tank custom built and if so, what material is it AND, are you happy with the result? Also do you remember the cost?

Cheers,
Tim..

[blaze]

Hi Tim
I had mine custom made of 3mm aliminum,it has 2 baffle plates and cost $450 from memory. I wish I had it made 200mm longer now, was a lot more work involved to do that though, mine only holds 70l and the extra would have give me close to 100l, I have never had a problem with the 70l as i carry a couple of 25l tanks on longer trips.
cheers
blaze

[familyman]

A mate of mine is a welder and is going to weld up a 100 litre tank from 3mm ally, 500mm wide 170mm deep and 1200 mm long.I intend to put this in the under floor kill tank area as i have no need for a kill tank this large.USCG have a HUGE amount of info about tank standards of construction,mountings and plumbing on their site.Most importantly make sure the thing does not leak either liquid or fumes.Also see previous topic about bilge pumps and fuel tanks{back about 1 month}.

[oscar]

Thud,
If you get onto Haines Hunter they will supply you with the information you need. When I had my 445C they supplied me with all the exact pieces for a new windscreen. They appear to have drawings of all the boats they have ever made.
oscar