Determining capacity of a tank

My "favorite" use of the inch system is building stairs, where odd spaces get divided into whole numbers of treads and risers. Like 12' 11 1/4" divided by 14. Has to be done decimally, then converted back to fractions. That is when I envy the rest of the world.
I've heard that old Swedish carpenters still use the "Thum" (? spelling), or thumb, which is, I think, an inch. Raggi might know about that. Inches are actually convenient at times.

 

Me too! That's not a problem!

 

L X H X W / 231 will give you the number of gallons. The Dims that are given in the catalog, is the space the tank will take up.

 

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????? Huh? That's what a dimension is, "space occupied".
A tank that measures L X W X H, should hold the gallons responding to the math of it's dimensions. This is, within reason of course, the thickness of the tank material, strap indentations, neck fills, vapor space etc., will alter the pure math. BUT.... the demos I posted are 8+ gallons off! 1, too little & #2, too much. 8 gal, off is not acceptable in my book.

 

does this tank in question have handles? fill cap above the tank? You are correct 8 gallons is too much difference, if you are dealing with a 20 gallon tank. At the same time it does not take all that much area to use up 8 gallons. Ex: a tank that is 1 foot by 1 foot by 1 foot will hold 7-1/2 gallons.

 

These tanks are permanent mount boat fuel tanks. 1 is a below deck model, the other is a on exposed mount tank. The catalog is "Overton". I just picked it up and used those tanks as a model to test the formula. When they (I computed several more, none made sense), came out so far off the stated gallons, it made me doubt the math. So, I came here. The math is correct, so what are we buying?
No handles or other unusual construction, just plain plastic tanks. I could even understand if the applied math always fell on one side of advertised capacity, but one tank is too much, another too little. It's crazy.
I have other catalogs, maybe I'll try the math on them tonight & see how they fair.

 

Just an stupid question: are those tanks parallelepipedic of square or rectangular section, or not?

 

It does make one wonder if honesty is still something we take with pride or is it something that we fudge on when it comes to our benifit. I'm at a lost on why there is so much difference between what is stated and what you get. If you get it figured out as why it is, I would like to know also.

 

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"Parae.....?? My ignorance is revealed I guess. A tank that is 14.5" X 8" X 24" is a rectangle (I think).
All I was doing was checking my math skills. What better way than to compare to a known quanity? Thanks to ya'll, I know the method is NOT the problem. Thanks.
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Those with interest in these "advertised" tanks can get a catalog & pick a size. I've checked 8 sizes & none of them come close. I'm thinking that hand filling each with a gallon container is the only syre way to know the truth.

 

You don't need to fill them Ted.

Put a dipstick in the tank, mark where the fuel goes to, put in a gallon, make a new mark where the fuel is then.

The difference between the marks is a gallon.

Measure the distance, assume 1 3/16" then mark the stick every 1 3/16" from the bottom.

The mark at the top of the tank is the total gallons.

Also to calculate how much is in your tank you are going to need a dipstick anyway so you kill two birds with one stone.

Poida

 

My last post was largely sarcasim. I now have faith in the math and less in the integrity of catalogs. Thanks to all.