Adding a baffle to a poly diesel tank - SailNet Community

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Go Back   SailNet Community > On Board > Gear & Maintenance
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Old 08-14-2008
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Adding a baffle to a poly diesel tank

I'm replacing a rusty old steel tank with a brand new 28 gallon cross-linked polyethylene diesel tank. This tank has no internal baffles. I'm concerned that with a less than full tank, a pitching sea could cause the fuel to slosh away from the pickup line and cause it to suck air for a moment.

I'm thinking of adding a small baffle to make sure this does not happen. I'd have to glue it to the inside. I would have a small hole at the bottom to allow fuel to slowly fill the area around the intake. Since the fuel tank is new, there's no diesel to contend with.

Has anybody ever done this? What kind of glue would I use? Epoxy? Could I use a material other than cross-linked polyethelene? Any other gotchas?
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Old 08-14-2008
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Epoxy and for that matter every adhesive I know of won't stick well to Polyethylene. Maybe you could plastic weld a baffle in place, but I would not want to mess around with that as there is a chance of weakening the wall of the tank.

Could you attach a baffle to something else in the tank like the inspection port or the fuel intake line?
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Old 08-14-2008
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You're probably going to cause more problems than you solve by modifying the tank. You should probably talk to the tank manufacturer before proceeding.
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Old 08-14-2008
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the only way to add anything to poly items is by thermal "welding". I had a custom holding tank made and this is how the company did it - using polyethylene rods and fusing panels with those. This could be done to your tank too, but it will make the tank very expensive.

It does seem like looking for another tank should be the thing to do. There are numerous tank catalogs, if you need help locating them - ask, and I will try to dig up a few.
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Old 08-14-2008
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West has a new epoxy with an additive to bond to plastics, which might work. The question is how you would get something into the tank and set into position with limited access, since cutting into a rotacast tank is a sin against nature. And the dollar.

I suspect the most effective answer will be getting a different tank, or two smaller tanks.
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One thought, Insted of glue or plastic welding. Could you cut a piece of plastic, drill a bunch of holes in it, coil it or fold it to fit the access hole, insert it and unfold it internaly like a boat in a bottle. But it may slosh around and bump a bit. There should be some form that would fit. I would have to play around with that one a bit. Just thinking out loud. Al
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Old 08-15-2008
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There are some indentations in the sides of the tank designed to accommodate hold-down straps. I can use these indentations to secure a baffle to the inside of the tank without gluing anything to the to the tank.

By avoiding gluing, I can also postpone this project until winter since having residual diesel won’t be a problem. In the meantime, I can just keep the tank full and/or avoid heavy weather.

Thanks for all the ideas. You guys are great!
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Old 08-15-2008
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I once read of a patent / application useing expanded metal mesh blocks for use as baffle. The orginial claim I believe was to stop the explosion hazzard. But thinking about this if a source of expanded mesh matrix could be found it could fit in the clean out hole then the three dimensional mesh pattern would be a continous baffle. I did not have any luck goggling to see if I could find a source of the baffle material but found a few patents that are for car application of this. Might be easy to do if a source of the mesh could be found, since the mesh would not take up a much volume in the tank being thin. One patent link is below.

Filler assembly for automobile fuel tank - US Patent 6415942
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If the patent wasn't denied, it should have been. Military "explosion safe" fuel tanks have been made that ways for ages. the tank contains either a foam rubber filler, or a metal mesh filler, which completely fills the tank. The metal mesh absorbs heat, preventing combustion if the tank has been penetrated by live rounds.

Nothing new here. You DO, however, need to wiggle the block into the tank (easier before assembly) and make sure the components are fuel-proof. And for boats--engineer a well for the fuel sender float, and consider that you will be creating a "honeycomb" nest where dirt and critters can accumulate.

Things are a little different for combat aircraft.
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I agree on the patent that it should be denied, but alot of things the patent office does is mind blowing. (patenting a standard machinery handbook thread because of the application / use of the thread).

Just thought it would be interesting if a colaspable stainless or plastic mesh matrix was available it might be easy to cut it just oversize and slide in let expand / open up, replacable when needed / cleaning tank, all done through clean out port. For the fuel sender and the pick up I was thinking that a solid mesh sleeve could be place around the sender and mounted to the sender flange.

Just thinking on the keyboard. I have alum tank with built in baffles in good condition.
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