Fuel tank idea

Da Nag · Posted: Sat Sep 04, 2004 4:10 pm Post subject: Fuel tank idea

On my last cruise, a simple idea hit me. Somebody must have thought of this before...I'm wondering if there's reason not to do it.

Why not put a fitting at the bottom of each fuel tank, and run a fuel hose between them? Wouldn't this keep the volume of fuel relatively equal between the two tanks, and possibly help in keeping things better balanced during longer cruises?

If you wanted to retain the ability to adjust balast by keeping more fuel in one tank than the other, a valve could be placed inline, which when closed would prevent the fuel levels from equalizing.

Thoughts?

Almas Only · Posted: Sun Sep 05, 2004 7:39 am Post subject:

I'd be careful with this kind of connection between the tanks. Although it would be handy, I see two potential problems: first, if you aren't careful and let yourself run dry, you are totally dry, with no backup, because both tanks will be empty. Second, and more serious, is that you are cutting holes in the sides of the tanks, near the bottom, and installing fittings and hose. If anything fails or gets knocked loose, you've got a lot of gasoline flowing into a confined space, with all kinds of electrical connections and switches which are not explosion proof. And, since gas vapors are heavier than air, you would have a ponding of vapor with enough volume to blow you and the boat to never never land.

Sneaks · Posted: Sun Sep 05, 2004 9:51 am Post subject:

Gotta agree with Alma's Own about the safety issues. In retrospect, I've never seen marine fuel tanks with fittings other than from the top. Gotta be a CG reg covering it. Much safer to walk back and periodically switch the fuel tank selector.

Mr. Fisherman · Posted: Sun Sep 05, 2004 9:54 am Post subject:

Bill,

Part of the beauty of a dual tank set up is that they are two separate and isolated supplies. If one is contaminated or has an issue you still have one to fall back on. Fuel management is key but trim tabs are the answer to solving the ballast issue.
As mentioned above, any modification to the fuel cell is dangerous and should not be treated lightly.
I recently assisted a qualified friend of mine in the removal and modification of my fuel cell. We welded improved supports to the cell after draining, rinsing, rinsing, rinsing the tank. took more time to prep than to do the work.

Da Nag · Posted: Sun Sep 05, 2004 10:38 am Post subject:

I guess the above replies are why nobody has done it...

Good points, folks - I'll put the drill away.

Sea Wolf · Posted: Sun Sep 05, 2004 1:41 pm Post subject:

Bill-

Difficult issue, with several valid points about the value of two isolated supplies and the dangers of outlets below fluid level.

But the idea of self-leveling tanks, and not having to switch tanks mid-journey is still a good one. I'm sure it would be possible to splice in a couple of "T"'s in the fuel lines that come up out of the tanks and set up a siphon system to level the tanks out. It would require a means to eliminate the air in the siphon hose between the "T"'s, and a shut-off so that either tank could be used individually.

A third "T" in the middle of the siphon tube and a primer squeeze bulb could be used to do pump out the air to one of the tank vents and another "T" installed there.

To isolate the tanks, a simple shut-off valve would have to be placed in the siphon line.

All we need is a siphon tube, three "T"'s, a primer bulb, another length of fuel line (to the vent hose)and a shut-off valve....... I think that's about as simple as it can be done.

I'd strap the siphon tube up against the underside of the motor well to keep it up out of the way so has less chance of accidental damage as it crosses over between tanks. Paranoid folks could use a metal braided armored fuel hose for the siphon line.

It's a bit Rube Goldberish, and some will invoke the Kiss Principle in criticism, particularly in regard to the danger of fuel spillage, but if one want self-leveling tanks, it could be done. The primer bulb siphon "prime" would be good until you accidentally ran a tank dry and lost it.

Sawdust · Posted: Sun Sep 05, 2004 10:29 pm Post subject:

Hate to see good friends screw up a great system. You can see how much fuel is in each tank, just burn the high tank -- no fuss no mess. Before my much-loved trim tabs I'd burn fuel to assist in levelling the boat. And having two separate systems lets you suck up any crud (hope none) in the bottom as you run each tank dry -- then check your see-through filter for water or debris.

Lots of ways to skin a cat (ooh Brock what I said), but IMO KISS is the only way to go. Tabs are great (we all know that), but if not used properly they can cut down range, increase fuel consumption, and get you in trouble in a heavy following sea. Trim the boat first, then use tabs if you can't move stuff in the boat. Would not have a 22 without them...

Dusty - still rockin'

Larry H · Posted: Fri Mar 10, 2006 11:04 pm Post subject:

I seem to remember that the US Coast Guard prohibits openings in the sides or bottom of gasoline fuel tanks.

Sea Wolf · Posted: Sat Mar 11, 2006 5:25 am Post subject:

Larry-

"I seem to remember that the US Coast Guard prohibits openings in the sides or bottom of gasoline fuel tanks."

And for good reasons. There's probably also some historical / anectodal evidence that his is a bad idea!

What I was proposing on the other thread was to combine the output or supply tubes above the tanks to sos as to equal out their levels and and in the process empty them evenly to keep the boat balanced.

Joe.