We have a local guy here that teaches welding at the college and he's a
persnickety perfectionist and very very knowlegible about all types of
welding. I know another guy up in Homer, Alaska that is also extremely
top-notch and an excellent welder. I'll do my homework with both these guys
on the tank design, and then will spec it out. I'm hoping the local college
guy will weld it up for me ...he's such a perfectionist, not just with the
welding but all the structural issues. His students pass the certifications
at very near the 100% level, one of the highest rates of successful
certifications in the country. I don't know if he's willing to do custom
work but I sure hope so. I just want to get all the answers I can before I
go chase him down.

Having the tank suspended by the longitudinals means free open air under the
tank and prevents corrosion. I guess I could put a support stringer under
the tank and weld on a sacrificial strip of aluminum that'll rest on it.
Something like 1/4" thick...take a few lifetimes to corrode that away,
assuming you seal-weld the edges and don't trap water between it and the
tank via capillary action. Education is ongoing ...I'll keep looking into
this stuff. And I *do* own the full set of ABYC and USCG specs ...need to
go read the fuel tank stuff too.

Dave Gerr has a couple of articles, a 2 part series, in the current
Professional Boatbuilder and the last one (Number 84 and 85,
August/September issue and October/November issue, 2003).

Brian

--
My boat project: http://www.advantagecomposites.com/tongass


"Stephen Baker" wrote in message
...
Brian says:

Is there any issue with bends becoming weak?


No, there is an issue with bends BEING weak. ;-)
Take a sheet of aluminum, bend it 90 degrees, then bend it straight. Now
try
to rip it.
See what I mean?
Welding will lose you a lot of strength, yes, but it is a well-documented
loss,
and folks will generally use only strength figures for the welded
condition.
If you use bent plate, and calculate for the un-welded strength, you
_will_
suffer for it.

Steve "not an aluminum expert...."