Fuel Tank build
 

Here's some things I've learned. When testing a tank under preasure.
1st you only need about 1lb of preasure. I took it to the high side of 1lb. IE the needle on a 0 to 15lb guage was just to the right of the 1lb mark and it was touching that mark.
THAT'S IT NO MORE!

My brother has a really sharp guy working for him he said if you take it to 4lbs that sucker will unzip itself. I belive him.[^]

http://www.classicmako.com/bobby/P1010111.JPG

http://www.classicmako.com/bobby/P1010114.JPG


Here's some interesting data from brother Rick.

Here is something you can show to the people that think you should
pressurize your tank to several psi for testing. I put together a quick
model and analyzed it in my finite element program (stress analysis). I
modeled it to the same dimensions as your tank and even put in the interior
baffles as they add to the rigidity of the tank. I then put a load of 1 psi
internal pressure. You can see the results. The max stress is the orange
area which equals 130,599 psi. Just so you know, the material we used
yields (permanently bends) at about 100,000 psi. I assume what is happening
is that the area that is permanently bending is small and that is why it is
not showing up. However, it probably won't take much higher pressure to
open this thing up. The orange areas show you where it will most probably
open up first.

http://www.classicmako.com/bobby/fuel%20tank.jpg

Re: Fuel Tank build
 

Gotta love CAD, Nice welds, looks great. That's aluminium isn't it? USCG won't certify stainless tanks anymore.

Re: Fuel Tank build
 

nope.. she's Stainless Steel... [img]/images/graemlins/shocked.gif[/img] [img]/images/graemlins/shocked.gif[/img] [img]/images/graemlins/shocked.gif[/img] [img]/images/graemlins/shocked.gif[/img]

Warhog.. why SS tank?

Re: Fuel Tank build
 

Yes it's ALL stainless steel. It will still have a Coal Tar epoxy coating on the outside.

Re: Fuel Tank build
 

Yeah, I had a beautifull 130 gallon belly tank that I tired to get recertified and no one would touch with a stick. And the USCG doesn't like them because the welds are prone to give out. The freak'n thing had to weigh 300lbs. [img]/images/graemlins/shocked.gif[/img]

Re: Fuel Tank build
 

I'm not sure I understand ....

Bobby .... feel like we are ganging up on ya with the questions... but the pressure testing ... is 1 "lb" (psi I assume) appropriate ?? I ask only because of what the Federal Regulation states (or at least how I read it) ....plus I know the tank builders around here all mention and build to the CG/Federal standards and they typically test to 5 psi …even mentioned on their websites

Does the 1 psi pressure test fit within the Federal requirements ? Is the caveat in #2 below ?

Maybe I don’t understand the methods of testing or the numbers being thrown around here….or maybe it has to do with the malleability of Aluminum vs Stainless?


Quote from Boatbuilder handbook
Title 33 CFR, Sections 183.501–183.590
FUEL SYSTEMS
Revised November, 2003

“FEDERAL LAW:
183.542 Fuel systems.
(a) Each fuel system in a boat must have been tested by the boat
manufacturer and not leak when subjected to the greater of the
following pressures:
(1) Three pounds per square inch; or
(2) One and one-half times the pressure created in the lowest part of the
fuel system when it is filled to the level of overflow with fuel.
(b) The test pressure shall be obtained with air or inert gas.”

Re: Fuel Tank build
 

Scott I understand your consern. Does anyone really put that much preasure on them? The guys I get my imfo from all all in the Naval Medical Reserch Facility. They build all kinds of WILD $hit. One of the guy's there said "If you put 4lbs in that sucker it will unzip itself". he's a pretty sharp guy and has fooled with this stuff a fair amount.

Here's a quote from another guy who builds fuel tanks.

Accurate Towers
Member

Offline

Member #4826
262 posts
Naples Fla USA

Report this post to a ModeratorAdd this post to My NotepadSend Instant Message
Re: Fuel Tank Build (warthog5) 7:43 AM 12/7/2004 Reply to this post

Warthog...

Yes 3 lbs. is ALOT, you dont need that much air at all. Just fill up the tank till it bulges a little bit, don,t over fill it at all. Use a soapy water mixture in a spray bottle to find leaks. Wow, Stainless is definate overkill. That tank will break your back. Stainless is ok for a tank but usually for hundreds of gallons. A 70 gal.
tank could have been made of aluminum and weighed less overall. The gas
pickup should be no less than 3/8ths dia. tubeing. Any less will starve your
motor and stall eventually. Do not put any back flow devises on your gas line
they tend to starve an engine as well. Use a good recomended cartrage in
line filter. The vent, nothing less tan 5/8ths hose, anything less will make it a
hard slow filling tank. Try to make your gas fill tube a straight run to make it a faster filling tank, any bends or 90 degree fills will drasticlly cut down filling of the tank. Bet you'll never try another tank again, only if you must.

Good luck... http://www.AccurateTowers.com

Re: Fuel Tank build
 

Warthog, I'm not trying to bust your nuts but I do know stainless tanks are a no no. You can do anything you like in your boat (looks great btw) and you've worked hard, but don't try and sell yourself on a tank that can't hold 4 psi.

There's a reason why you don't see stainless tanks in new boat manufacturing, and it's not becauce they're expencive.

and notice the fact that coal tar epoxy has peeled off in sheets...


every time I read ANYTHING this guy types I laugh !

warthog ?? should "bobby the butcher"...

So you never screwed up before? My guess is you got booted out of kindergarten for not playing nice.....

strick