Below Deck Fuel Tank

[Seadog]

I'm considering putting my fuel tank under the floor, with an access panel over it.  The tanks were above the floor, stuck under the console.  Wanted to see if anyone has done this before, or knows of anybody who has, in those old Aqusports and what problems you might have come across.  Theres nnot to much room under there so it is going to be a challenge for sure, the tank will have to be only about 7" - 8" deep.  Any help would be appreciated!

[oystercatcher]

I don't know what year they started building tanks in-deck, but my '75 had an access port under the console.  made replacing the tank in 2000 much easier.

Also, don't those early 70's hulls have very little deadrise (?).  that may mean little room for a tank under the deck.  Remember, you'll need room for a platform to support it too.  You won't know how much room you've got between teh stringers until you get in there and start digging around.

You'll need a good fabricator to build it for you, once you figure out how big.

good luck

[Radioshop]

Due to the lack of deadrise, there's probably a shortage of space to locate a decent sized tank under the deck.  Since you've ripped out the deck anyway, you could cut out the floor under the console which would create a storage well.  This would be like the new offshore boats with the in-console head compartments (that only seem to be useful for causing seasickness).  This would vastly increase the storage are under the console and would probably allow you to install a decent sized square fuel tank.  Not to mention, you wouldn't have to crack open the deck if there was ever anything wrong with the fuel tank.  The only challenge I can think of would be keeping water out of the well and, draining it if water ever did get in there.

[Seadog]

Dead rise.





In the second picture you can see the stringer lay out.  The center floor compartment, that is to the left of the pieces of wood planks laying on the side of the hull, is where the front of the console will be.  You can see there are 5 stringer systems:  Two on the sides, one in the middle and two on each side of the middle.  My options for the tank are.  1 - remove the middle stringer, behind the floor compartment and add the tank, 2 - put two saddle tanks, one on each side of the middle stringer - not my favorite idea, or 3 - just use the above floor design it had originally.  I've thought about making a different stringer grid system layout, similar to Gause Built, but have been advised against that by the guys at Aquasport.  That system would be easy to accomodate a below deck tank but may not be structurally sound.  If I make a place for the tank along the mid-line it will be as far forward as possible, up to the floor compartment.  Whatcha think?

[Argo]

That is one flat bottom.  Can you make twin tanks to run between the stringers? Run them together so the fuel comes out of both of them at the same time.

[Seadog]

Argo - do you mean have two tanks on each side of the middle stringer, connected by a fuel hose, run at the bottom of both tanks, thru the stringer? And have the fuel drawn out of one location? Not sure that would work, but it's an idea.

[Argo]

Have the tanks like you say with a fuel line coming off the rear of each one and connecting down the line at a 3way stopcock or continuous flowcock of somesort that alows the fuel to be fed from both tanks to the engine rather than runing it in a circuit.  I guess the circuit would work but would take more plumbing.

[Radioshop]

You could put in one small tank in the middle and have both feed into the small tank.  Then feed the engine(s) off the small tank.  That Y fitting in the fuel line sounds kind of dicey.  It would be kind of like a "day tank" in a generator.  Day tanks are typically used when the primary fuel tanks are below ground and the engine is above ground.  An electric lift pump fills the day tank and uses a float switch to activate the pump.  In your case, gravity could be used since both tanks would be higher, albeit not by much.  

Also, more food for thought, fibeglass fuel tanks.  Several high end builders, such as Bertram use fibeglass tanks.  While you don't want the bottom to be part of the fuel tank, I wonder what about turning a portion of the stringers themselves into fuel tanks.  Build short stringers, then use the rest of the height as fuel tanks.  Now that would be bizare!  Conversely speaking, if you were to make tanks out of fiberglass, it would give you lots of flexibility on what could be done.  

By the way, that stringer system is a beast!  Were they foam filled?

[Argo]

The dicey Y connector is used by quite a few manufacturers in dual tank setups.  Worldcat being one of them.

[Seadog]

I don't know much about fiberglass tanks but it may be worth researching.  As you can see from the pixs, the stringers were foam filled.  15 thirty gallon trash bags full of that nasty stuff. God what a job that was!  Smelled like a soaking wet dead billy goat

[Wilson]

Whoa!!! you cut the stringers completely out?!?!?!  Couldn't you have simply cut off the tops and dug out the foam, then reglassed the tops?

I had soooo many bags of foam too.  I really think it smelled worse than something dead.

[Seadog]

Wilson - I tried to get it all out with a shovel, but was not happy with the result.  There was still some wet foam stuck down where the stringer attached to the hull that I couldn't get out.  Didnt want to glass the thing over knowing some wet foam was still in there. So I probably went a little saw crazy - cut out a little of the first stringer down to the hull, got all the foam out, liked the result and just kept goin down to the bare hull.  Nothing like a little extra work, huh?

[Wilson]

I gotcha.  I had to do the same thing, but I had wood stringers.  Grinding all that stuff down was awful, especially since it was in the middle of the summer

[Radioshop]

Trashbags, the best place for foam.....

[Anonymous]

Is it safe to say that the foam served no purpose other than creating a form for the stringer? I am planning on stripping out my stringer and now just glassing them over and not putting any foam back in.

Mike