so it looks like im going to fab some auxillary gas tanks for my boat. im thinking 1/8" will be thick enough. what do you guys think?
also im thinking of putting a "low spot" (sump) at the bottom of the auxillary tanks. the 2 auxillary tanks will be positioned higher than the main tank in the belly of the boat. i was thinking of having this "sump" drain directly into a "T" on the fuel return line to the main.
my theory is that as the main tank loses gas the 2 auxillary tanks will automatically gravity feed the main tank. does this sound like it will work?

 

found the answer as far as thickness. as far as how it will or wont work what do you think?

 

no if the borrom tank is not sealed up completly air tight it which im sure it has a vent and the fill cap is olw also. the top tank will just drain in and over flow the bottom tank

 

the fill cap and vent of the main tank are higher in in elevation than the 2 auxillary tanks.

 

Here is a post where I made a tank for my car.

https://honda-tech.com/forums/welding-fabrication-53/oem-location-fuel-cell-2691148/

As far as the two tank set up goes, you can hook it up like you said, as long as the top level of the two extra tanks does not excedes the top level of the main tank. Or you can put them higher and move the vent from the bottom tank to the highest tank in the system.

Stefan

 

both the auxillary tanks will be positioned physically higher than the main tank. the fill and vent tube of the main tank is positioned higher than the auxillary tanks though. make sense?

 

then it should work out just fine for you

 

i thought it would work but thought id get other opinions. thanks to everyone that responded. much appreciated.

 

wont the pressure from the 2 aux. tanks push the fuel up and out the vent and fill cap of the 1st?I dunno, these things confuse me too.

 

i dont know. i didnt think they would because the fill and vent of the main tank is set higher than the auxillary tanks. i guess worst case scenario i just put a valve in there to stop flow to the main tank until i see the guage get low. that should cure all problems.
i will only run these tanks 2-3 trips a year when i need the extra gas. i would feel plenty comfortable with 100-110 gallons for these trips. 60 just isnt cutting it.

 

No. It will only go high enough to have equal heights in the aux tanks and the filler neck/vents as long as everything has an equal pressure on the top of the fluid.

Think of a simple manometer:

 

so if everything has atmospheric pressure on top, than as long as the filler and vent are the highest, it WONT over flow?