Working on my fuel system and am totally confused. I have a tank
manufacturer here in town who is willing to build a couple of 5086
aluminum tanks for me for considerably less than the other tank makers I
have found. Naturally I want to check out his proposed specs against the
regulations.

"SAFETY STANDARDS FOR BACKYARD BOAT BUILDERS” (for all intents usless
once you get past a skiboat) refers to 33 CFR183.580 which concerns
gasoline tanks. Basically it says an acceptable tank has to be built,
beat to death, pressureized to 5 psi and if it doesn't leak, you can use
it. How far back in the hull determines how much you have to beat on it.

46 CFR 58.50 and 182.440 specify 5000 series aluminum with a minimum
thickness of 1/4" for diesel tanks. That seems a bit excessive for a 40
gallon tank but 46 CFR is for passenger vessels.

What are the requirements for a recreational diesel tank?

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Glenn,
ABYC states a min. thickness for alu diesel tanks (5052, 5083, or 5086 alloy)
of 0.090", and all fittings should be 6061-T6 or 300-series stainless.
There is a lot more to the "recommendation", let me know if you want it.
Steve

That sounds more reasonable. #12 MSG is .1046" thick so that puts me a
little over the minimum.

Stephen Baker wrote:
Glenn,
ABYC states a min. thickness for alu diesel tanks (5052, 5083, or 5086 alloy)
of 0.090", and all fittings should be 6061-T6 or 300-series stainless.
There is a lot more to the "recommendation", let me know if you want it.
Steve

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

By now you may have found the online articles about tank failures and 0.090"
walls, right? Big improvement if you go to 0.125". Number one reason for
failure on thin tanks is metal fatigue, especially at or near weldments.
Number one reason for failure on heavier tanks is corrosion. Number one
reason for corrosion is tank immersion (in water) or standing water on the
tank. If the tank is kept dry, ventilated, and built with 0.125" or thicker
walls and lid, then you've nixed 99% of the tank failure problems. Add
baffles, I think 20" to 30" apart? Stephen? What's the spec here? A
friend that builds tanks drills holes in the lid and sides, makes baffles
(lots of holes and limbers) with a bent over tab on top and both ends. He
welds the bent tabs to the tank through the holes, then fills the holes with
fill material. Grinds flush. Having baffles welded to lid and sides means
that regardless of tank mounting, that the lid-to-tank weldment is prevented
from fatigue failures since the baffles are doing double duty and
transferring load to the tank sides. He either glass beads or etches (can't
remember which) the whole tank, primers and paints. He doesn't use a
special anti-corrosion primer such as zinc chromate, but you could if you
want. The paint is some kind of epoxy paint. Ameron Devoe 229h I think
....industrial grade epoxy paint.

He puts the pick-up at the aft end, an inspection plate above that point,
sometimes a well (water and sludge collection) below that point. He uses
1-1/2" filler and a vent ...what was it? 5/8" or so? Can't remember. He
doesn't put sending units in the tank...FloScan instead. When my boat is
nearer being ready, I'll probably let him build me a tank ...

Brian

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


"Glenn Ashmore" wrote in message
news:jcnjb.77205$sp2.22847@lakeread04...
That sounds more reasonable. #12 MSG is .1046" thick so that puts me a
little over the minimum.

Stephen Baker wrote:
Glenn,
ABYC states a min. thickness for alu diesel tanks (5052, 5083, or 5086
alloy)
of 0.090", and all fittings should be 6061-T6 or 300-series stainless.
There is a lot more to the "recommendation", let me know if you want it.
Steve

--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

I picked up on most of that already. It was the thickness that had me
flustered. You are right that .125" would be much better. Easier to
get good welds on too. Baffels are required every 30" and rosette welds
are what those filled holes are called. Fillers must be a minimum of 1
1/2" and vents 5/8". Those things I expected.

Other things I found that I was not expecting: 46 CFR 183.518 for small
passenter vessels says ALL fittings must be on top. 46 CFR 58.10-10(a4)
allows cleanout plugs and supply outlets on the bottom of the tank.

What has me really confused is the relationship between 33 CFR 181 - 183
and 46 CFR. They are not easy to figure out in the first place and the
way they are presented on the web makes it a lot worse.

SAFETY STANDARDS FOR BACKYARD BOAT BUILDERS has nothing in it that
applies to diesel powered vessels over 20'. I guess I will have to
spring for the ABYC guides but from what I have seen so far they don't
track exactly with the CFRs either.

Brian D wrote:
By now you may have found the online articles about tank failures and 0.090"
walls, right? Big improvement if you go to 0.125". Number one reason for
failure on thin tanks is metal fatigue, especially at or near weldments.
Number one reason for failure on heavier tanks is corrosion. Number one
reason for corrosion is tank immersion (in water) or standing water on the
tank. If the tank is kept dry, ventilated, and built with 0.125" or thicker
walls and lid, then you've nixed 99% of the tank failure problems. Add
baffles, I think 20" to 30" apart? Stephen? What's the spec here? A
friend that builds tanks drills holes in the lid and sides, makes baffles
(lots of holes and limbers) with a bent over tab on top and both ends. He
welds the bent tabs to the tank through the holes, then fills the holes with
fill material. Grinds flush. Having baffles welded to lid and sides means
that regardless of tank mounting, that the lid-to-tank weldment is prevented
from fatigue failures since the baffles are doing double duty and
transferring load to the tank sides. He either glass beads or etches (can't
remember which) the whole tank, primers and paints. He doesn't use a
special anti-corrosion primer such as zinc chromate, but you could if you
want. The paint is some kind of epoxy paint. Ameron Devoe 229h I think
...industrial grade epoxy paint.

He puts the pick-up at the aft end, an inspection plate above that point,
sometimes a well (water and sludge collection) below that point. He uses
1-1/2" filler and a vent ...what was it? 5/8" or so? Can't remember. He
doesn't put sending units in the tank...FloScan instead. When my boat is
nearer being ready, I'll probably let him build me a tank ...

Brian


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com

Don't forget that Subchapter K (the 46CFR passages) are for vessels
carrying passengers for hire. Their rules are much stricter than
those for rec. vessels, presumably because recreational vessels are
used more "voluntarily." Subchapater K covers vessels up to 100 tons,
so they are not really thinking of 40-gal fuel tanks.

ABYC publishes a book that puts together in one place all the federal
regs for recreational boats -- a good thing to have.

Cheers,
Michael Porter




Glenn Ashmore wrote:

snip

What has me really confused is the relationship between 33 CFR 181 - 183
and 46 CFR. They are not easy to figure out in the first place and the
way they are presented on the web makes it a lot worse.

SAFETY STANDARDS FOR BACKYARD BOAT BUILDERS has nothing in it that
applies to diesel powered vessels over 20'. I guess I will have to
spring for the ABYC guides but from what I have seen so far they don't
track exactly with the CFRs either.


Michael Porter Naval Architect / Boatbuilder
mporter at mp-marine dot com
www.mp-marine.com

Brian D says:

Add
baffles, I think 20" to 30" apart? Stephen? What's the spec here?

No spec listed, but 30" or so is reasonable. The other thing to make sure of
with baffles is that the size of the holes does not exceed 25-30% of the
cross-section area.
On alu tanks, I would recommend as little plug-welding as possible, say limited
to the top surface. (i.e. build the tank without the top, then insert baffles,
then close) Each plug becomes a hard point, albeit small.

Steve

Steve,

I've seen tanks made the way you suggested, but with the tank top oversize
so it extended an additional inch-plus on either side. This was for
suspending the tank by the lip. With all the pounding that a boat goes
through, I feel concern that the top weldment would be prone to fatigue and
cracking. OTOH, I do know lots of people do it this way (1/8" sides/bottom,
3/16" top). What do you think?

Brian


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

Add
baffles, I think 20" to 30" apart? Stephen? What's the spec here?

No spec listed, but 30" or so is reasonable. The other thing to make sure
of
with baffles is that the size of the holes does not exceed 25-30% of the
cross-section area.
On alu tanks, I would recommend as little plug-welding as possible, say
limited
to the top surface. (i.e. build the tank without the top, then insert
baffles,
then close) Each plug becomes a hard point, albeit small.

Steve

I had my aluminum gasoline tanks built by Ezell Industries one of the three
marine tank builders in Perry Fl. I let them decide where the baffles were
( a wise move) also they provided the tank fitting and valves which some of
need to be al. rather than ss or brass. One thing to consider also is the
pickup tubes, they made these with nylon? tubing swaged onto the al tank top
fittings. Some other people I talked to were not up to speed on the issue of
not using metal pickup tubes as they are subject to vibration and fatigue.
Wouldn't want the pickup to break!!! I was very happy with Ezell and the
good work they did.
Then Painting, which I did. This system is my standard and I use it on any
alum. thing I make for boats.
1, clean with acid ectching solution ( like, Ditzler DX533)
2 prime with dupont Variprime 615S self etching primer.
3 finish with several coats of 2 part epoxy primer.
For exposed alum. things, add about three finish coats of a urethane
enhanced enamel like Limco 1234.
All of the products are availble from automotive distributers I think the
key is using the variprime as is bonds to aluminum like nothing else I know
of..

--
Ron White
My boatbuilding website is:
www.concentric.net/~knotreel

I am beginning to wonder if locally built aluminum tanks are a good
idea. Every shop around here is tooled up for 6061 but marine tanks
need to be 5000 series. I will have to supply my own 5086 and TIG
welding rod and the best price I can find is in New Orleans. $130 a
4x10 sheet plus about $100 shipping. Still, a lot better than $300 a
sheet in Atlanta but not as good as $65/sheet for 1018 mild steel locally.

If I go with aluminum I think I will have to machine my own fittings.
There are very few sources of 5000 series aluminum fittings and the
selection is limited. It will be fairly simple to mill and tap some
NPTF fittings from 1" round for welding onto the tank.

I would like to hear some discussion of mild steel vs aluminum. Total
cost of mild steel tanks is about half that of aluminum but weighs about
twice as much. In this case a pair of custom 40 gallon would cost $600
in aluminum with some effort on my part to get the alloy vs $320 for
mild steel and weigh 72 pounds vs 125 for steel. From what I hear, a
well painted and installed steel tank will last just as long as
aluminum. Longer if the aluminum is not properly installed.

Ron White wrote:

I had my aluminum gasoline tanks built by Ezell Industries one of the three
marine tank builders in Perry Fl. I let them decide where the baffles were
( a wise move) also they provided the tank fitting and valves which some of
need to be al. rather than ss or brass. One thing to consider also is the
pickup tubes, they made these with nylon? tubing swaged onto the al tank top
fittings. Some other people I talked to were not up to speed on the issue of
not using metal pickup tubes as they are subject to vibration and fatigue.
Wouldn't want the pickup to break!!! I was very happy with Ezell and the
good work they did.
Then Painting, which I did. This system is my standard and I use it on any
alum. thing I make for boats.
1, clean with acid ectching solution ( like, Ditzler DX533)
2 prime with dupont Variprime 615S self etching primer.
3 finish with several coats of 2 part epoxy primer.
For exposed alum. things, add about three finish coats of a urethane
enhanced enamel like Limco 1234.
All of the products are availble from automotive distributers I think the
key is using the variprime as is bonds to aluminum like nothing else I know
of..


--
Glenn Ashmore

I'm building a 45' cutter in strip/composite. Watch my progress (or lack
there of) at: http://www.rutuonline.com
Shameless Commercial Division: http://www.spade-anchor-us.com