Fuel tank frustration
 

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

Fuel tank frustration
 

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

Fuel tank frustration
 

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

Fuel tank frustration
 

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

Fuel tank frustration
 

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

Fuel tank frustration
 

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

Fuel tank frustration
 

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

Fuel tank frustration
 

I have that section. The problem with it though is that the first
paragraph on aplicability says it is for gasoline engines. Most of what
I have found in 33 CFR 181 through 183 relates more to smaller gasoline
powered boats than to diesel cruisers.

Thanks for the home page for the CFRs though. I have been searching
piecemeal.

Leo Petipas wrote:
Hello again Glenn,
I think you want Title 33 instead of 46.
I am sending you the PDF for 33CFR 183.5.
It looks like you have a couple of materials that you are not allowed to
use.
Otherwise, you just have to pass the pressure test.
Leo
I hope you don't mind me downloading your boat project for my own use.
Here's the link for future searching of the Code of Federal Regulations.
http://www.access.gpo.gov/nara/cfr/index.html#page1


--
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

Fuel tank frustration
 

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

Fuel tank frustration
 

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

Fuel tank frustration
 

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

Fuel tank frustration
 

Glenn Ashmore wrote:
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..



Either aluminum or steel will probably outlast both you and me. I've
seen diesel tanks for equipment on trucks made from steel that have
never been painted that were over 30 years old. I'm thinking about
making mine out of steel, but I plan on some type of coating inside and
out, just not sure what brand yet. Weight is no problem for me with a
steel boat and no plans for racing, just cruising. I would think that
would be a major deciding factor for you. Can you stand the weight.
Cost is always a major deciding factor for me. I have to build on the
cheap. I would think you would have more resources available. Is $300
or $400 a deciding factor? What about a poly tank? I'm sure you've
priced those, about the same as aluminum, but they're ready built.

Good Luck,

Donald

--
I'm building a Steel Robert's 434. You can sneak a peek if you wish by
clicking on me link below.
http://bellsouthpwp.net/d/o/donrayp/
'USA, Home of the best
politicians money can buy'

Fuel tank frustration
 

Brian says:

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?


I'm not exactly fond of that method. As you say, too risky. If you want to
hang something make up a bracket properly sized, and then all you have to
replace is the bracket if it fails. THat's the same reason why my stereo
system is component rather than "boom-box" style. I don't have to replace
everything coz the turntable dies (yes, I'm that old ;-))

I love things that work, and can be depended on. That includes gravity. If
gravity will hold something in place when static, then a simple strap to take
care of the dynamic situation is all you need. And it's cheap!

Steve

Fuel tank frustration
 

Donald Phillips wrote:

Either aluminum or steel will probably outlast both you and me. I've
seen diesel tanks for equipment on trucks made from steel that have
never been painted that were over 30 years old. I'm thinking about
making mine out of steel, but I plan on some type of coating inside and
out, just not sure what brand yet. Weight is no problem for me with a
steel boat and no plans for racing, just cruising. I would think that
would be a major deciding factor for you. Can you stand the weight.
Cost is always a major deciding factor for me. I have to build on the
cheap. I would think you would have more resources available. Is $300
or $400 a deciding factor? What about a poly tank? I'm sure you've
priced those, about the same as aluminum, but they're ready built.

I don't think interior coatings on diesel tanks are a good idea. Diesel
is not going to attack the metal and is a pretty good corrosion
preventive. Any coating carries the possibility of flaking off and
finding its way into the filters.

$300 would not be a deciding factor but now that I am on the down hill
side of the project I find Everett Dirksen's comment about "A billion
here, a billion there, pretty soon we are talking real money."
particularly relevent. :-)

I checked every maker of poly tanks but could not find a shape that
would work without wasting a lot of space or leaving the COG of the fuel
way to high and getting molds made for custom tanks is way to expensive.

I considered building my own out of glass/epoxy but I don't like the
risk. I built two water tanks and found it took a lot of effort to get
really solid laminations in the corners. If there is even one pin hole
there will be some weeping. I can live with a little fresh water
weeping but not diesel.

--
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

Fuel tank frustration
 

Did you check Ronco for a tank? They make more stock shapes than anyone I
know, and are very easy to work with. http://www.ronco-plastics.com/.

I'd stick with regular steel for the tanks if you can't find one at Ronco. I
have a pair that are 17 yrs. old and fine. You are right about the inside,
the diesel is a good anticorrosion treatment, as long as you keep the water
out. The outside should be painted with a good coating of some kind, and the
bottom should be supported so that air can circulate under it. Obviously,
you've got to keep the water off the top of the tank as well. Be sure to
have the maker put a sump with a dip tube from the top in the tank so you
can suck out any water that might end up in there.

"Glenn Ashmore" wrote in message
news:EoRjb.78877$sp2.14422@lakeread04...

Donald Phillips wrote:

Either aluminum or steel will probably outlast both you and me. I've
seen diesel tanks for equipment on trucks made from steel that have
never been painted that were over 30 years old. I'm thinking about
making mine out of steel, but I plan on some type of coating inside and
out, just not sure what brand yet. Weight is no problem for me with a
steel boat and no plans for racing, just cruising. I would think that
would be a major deciding factor for you. Can you stand the weight.
Cost is always a major deciding factor for me. I have to build on the
cheap. I would think you would have more resources available. Is $300
or $400 a deciding factor? What about a poly tank? I'm sure you've
priced those, about the same as aluminum, but they're ready built.

I don't think interior coatings on diesel tanks are a good idea. Diesel
is not going to attack the metal and is a pretty good corrosion
preventive. Any coating carries the possibility of flaking off and
finding its way into the filters.

$300 would not be a deciding factor but now that I am on the down hill
side of the project I find Everett Dirksen's comment about "A billion
here, a billion there, pretty soon we are talking real money."
particularly relevent. :-)

I checked every maker of poly tanks but could not find a shape that
would work without wasting a lot of space or leaving the COG of the fuel
way to high and getting molds made for custom tanks is way to expensive.

I considered building my own out of glass/epoxy but I don't like the
risk. I built two water tanks and found it took a lot of effort to get
really solid laminations in the corners. If there is even one pin hole
there will be some weeping. I can live with a little fresh water
weeping but not diesel.

--
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

Fuel tank frustration
 

Keith wrote:
Did you check Ronco for a tank? They make more stock shapes than anyone I
know, and are very easy to work with. http://www.ronco-plastics.com/.

My holding tanks are Roncos. No question that Ronco has the best
selection and best quality but the last time I checked they only build
water and holding tanks. HDPE is fine for water and holding but not for
diesel. They do use cross linked PE in their industrial chemical line
but for some reason they don't want to use it in their marine line.

--
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

Fuel tank frustration
 

Glenn,

FWIW: The Diesel tanks on Viking Star are 42 years old 1/4 steel and
are just fine. I scrapped down surface rust and repainted them this
last Spring, so I was all over them :-)

So, Steel does work well, as long as you keep water off of them.

( A dock mate with a 15-20year old CHB is looking to replace his
tanks. Engine room vents are set up to allow sea water ready access
to the top of the tanks.....)

One thing that I attribute to the good shape of my tanks is the fuel
pickup is at the bottom of the tanks, and the tanks are kind of wedge
shaped... At least in my mind, this has prevented standing water
from sitting in the bottoms of the tanks.

I have seen people talk about putting in a small 'well' or sump in
the bottom of tanks, and have the dip tube go into that well. That
way, and water in the tank will make its way into the well and at
least most of it will be drawn out.

-al-



On Thu, 16 Oct 2003 20:56:19 -0400, Glenn Ashmore
wrote:

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.

Fuel tank frustration
 

OK, Check with Ezell Industies Perry Fl. they made my tanks with 5052 H2 and
they were beautifuily done. Mine were 100 gallon but the prices you
mentioned should no problem not that money makes any difference. phone 850
578-2558 Dave Miller
Try also Rds Mfg also in Perry 850 584-6898
no personal experience with Rds but they make for some nice boats I have
been on.
Get some pro help here and move on to some good stuff like sanding and
grinding. I do hope you take take my advise on priming first with self
etching primer! The dupont Variprime has chromates as well, good for you
too.

--
Ron White
my boatbuilding web site is:
www.concentric.net/~knotreel

Fuel tank frustration
 

Steve, or an aluminum expert:

In general bends are better than welds (in aluminum) since you don't have
the heat treatment hardening of the tank in the area of bends, but do in the
area of welds. What if the aforementioned lips on the side, the sides, and
bottom, were all made from one sheet that was bent to make the shape. The
end caps would be welded on, as would the lid, but the welded-on lid would
not be carrying the weight. Is there any issue with bends becoming weak?

Brian


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

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?


I'm not exactly fond of that method. As you say, too risky. If you want
to
hang something make up a bracket properly sized, and then all you have to
replace is the bracket if it fails. THat's the same reason why my stereo
system is component rather than "boom-box" style. I don't have to replace
everything coz the turntable dies (yes, I'm that old ;-))

I love things that work, and can be depended on. That includes gravity.
If
gravity will hold something in place when static, then a simple strap to
take
care of the dynamic situation is all you need. And it's cheap!

Steve

Fuel tank frustration
 

My theory is that the least amount of welding the better. It weakens
the material much less and is a whole lot less expensive.

Brian D wrote:
Steve, or an aluminum expert:

In general bends are better than welds (in aluminum) since you don't have
the heat treatment hardening of the tank in the area of bends, but do in the
area of welds. What if the aforementioned lips on the side, the sides, and
bottom, were all made from one sheet that was bent to make the shape. The
end caps would be welded on, as would the lid, but the welded-on lid would
not be carrying the weight. Is there any issue with bends becoming weak?

Brian


"Stephen Baker" wrote in message
...

Brian says:


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?


I'm not exactly fond of that method. As you say, too risky. If you want

to

hang something make up a bracket properly sized, and then all you have to
replace is the bracket if it fails. THat's the same reason why my stereo
system is component rather than "boom-box" style. I don't have to replace
everything coz the turntable dies (yes, I'm that old ;-))

I love things that work, and can be depended on. That includes gravity.

If

gravity will hold something in place when static, then a simple strap to

take

care of the dynamic situation is all you need. And it's cheap!

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

Fuel tank frustration
 

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...."

Fuel tank frustration
 

I must disagree. Especially with non-heat treatable alloys like 5052
and 5086 used in marine applications. These alloys are work hardened.
You are confusing bent strength with fatigue cracking. If you bend any
metal back and forth it will crack but if you bend aluminum once it gets
stronger. Aluminum can be bent and stretched more than almost any
metal. A beer can starts of as a flat disk.

Aluminum sheet usually comes hardened to some degree. The hardness
comes primarily from the rolling process. The amount is indicated by
the H number that follows the alloy number. For example H0 is anealed,
the softest and weakest. H1 is hardened only. H2 is hardened and
partially anealed. H3 is hardened and then stabalized. The second
number is the amount of hardening and the third number defines hardnes a
little colser. H116 is between 1/8 and 1/4 hard only. H34 is half hard
and stabalized. When you bend them the hardness and therefore the
strenght goes up slightly. When you weld any of them they drop back to
the anealed H0 condition and are up to 20% weaker.

Also if the weld is not done exactly right or it is a little windy when
it is done blowing the shield gas away you run the risk of hydrogen
enbrittlement which results in cracking.

Stephen Baker wrote:

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...."

--
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

Fuel tank frustration
 

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...."

Fuel tank frustration
 

So, the bending may be OK after all...but if the lips for hanging the tank
are bent, then a lid is welded in, the weld will run right along the bend
that makes the lip. Probably not so good again. There must be *some* way
to make an aluminum tank that can be suspended by stringers. I want the top
of the tank to be 3/16" so that together with the welded in baffles, it'll
make a stiff deck to walk on. I know lots of people who've built the boat
that I'm building have used tanks like these, but they let them 'hang by the
lid weldment'. The biggest tank that I know of like this is about 8 feet
long and contains 80 gallons of fuel, or about 60 pounds per foot ...30
pounds per weldment, pounding in the waves. Is that OK or are these guys
driving around with a failure waiting to happen?

Brian

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


"Glenn Ashmore" wrote in message
news:h83kb.79220$sp2.58042@lakeread04...
I must disagree. Especially with non-heat treatable alloys like 5052
and 5086 used in marine applications. These alloys are work hardened.
You are confusing bent strength with fatigue cracking. If you bend any
metal back and forth it will crack but if you bend aluminum once it gets
stronger. Aluminum can be bent and stretched more than almost any
metal. A beer can starts of as a flat disk.

Aluminum sheet usually comes hardened to some degree. The hardness
comes primarily from the rolling process. The amount is indicated by
the H number that follows the alloy number. For example H0 is anealed,
the softest and weakest. H1 is hardened only. H2 is hardened and
partially anealed. H3 is hardened and then stabalized. The second
number is the amount of hardening and the third number defines hardnes a
little colser. H116 is between 1/8 and 1/4 hard only. H34 is half hard
and stabalized. When you bend them the hardness and therefore the
strenght goes up slightly. When you weld any of them they drop back to
the anealed H0 condition and are up to 20% weaker.

Also if the weld is not done exactly right or it is a little windy when
it is done blowing the shield gas away you run the risk of hydrogen
enbrittlement which results in cracking.

Stephen Baker wrote:

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...."

--
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

Fuel tank frustration
 

Now here I agree with Steven that tanks should be supported from below.
While the static load per inch may be low the dynamic cycling from
pounding through the waves can cause stress corrosion and cracking in
the weld. A thicker top could actually make it worse. Think about what
happens when 500 pounds of diesel bounces. The bottom of the tank
flexes pulling the sides together. The flange therefore pulls against
the weld. The top goes into compression and because metals are stronger
in compression than tension it deflects less so the weld has to bend.
Being the weakest point it will bend the most. Also having lost any
resistance to stress corrosion during the welding it will corrode faster.

If you are hanging the tank a better solution would be to at least add
angle irons across the bottom every couple of feet to reduce flexing
and possibly up the sides to mounting points on the stringers to take
the load off the weld.

Brian D wrote:
So, the bending may be OK after all...but if the lips for hanging the tank
are bent, then a lid is welded in, the weld will run right along the bend
that makes the lip. Probably not so good again. There must be *some* way
to make an aluminum tank that can be suspended by stringers. I want the top
of the tank to be 3/16" so that together with the welded in baffles, it'll
make a stiff deck to walk on. I know lots of people who've built the boat
that I'm building have used tanks like these, but they let them 'hang by the
lid weldment'. The biggest tank that I know of like this is about 8 feet
long and contains 80 gallons of fuel, or about 60 pounds per foot ...30
pounds per weldment, pounding in the waves. Is that OK or are these guys
driving around with a failure waiting to happen?

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

Fuel tank frustration
 

Keith wrote:

Did you check Ronco for a tank? They make more stock shapes than anyone I
know, and are very easy to work with. http://www.ronco-plastics.com/.

I'd stick with regular steel for the tanks if you can't find one at Ronco. I
have a pair that are 17 yrs. old and fine. You are right about the inside,
the diesel is a good anticorrosion treatment, as long as you keep the water
out. The outside should be painted with a good coating of some kind, and the
bottom should be supported so that air can circulate under it. Obviously,
you've got to keep the water off the top of the tank as well. Be sure to
have the maker put a sump with a dip tube from the top in the tank so you
can suck out any water that might end up in there.

In a sailboat, maximizing tank size is going to result in an irregular shape
with the fuel pick up at the deepest point. A sump is an unnecessary
embelishment. Water is going to be of concern only with contaminated
supply in a well designed system. If water in the fuel causes sleepless
nights tee into the fuel pump discharge so a liter or so can be pumped
into a container for disposal.

Fuel tank frustration
 

I've never felt comfortable about hanging the tank. I'd use poly, but I can
get more volume with a custom aluminum tank. I'll support the tank, either
by shelves that run along the sides of the tank (extending beneath the tank
to carry it from below of course) or will put an on-edge stringer under the
tank. Either way, will use neoprene between the support and the tank. The
tank will be etched, primered, and epoxy painted to prevent external
corrosion and I'll lift the tank out every 5 years or so for an inspection.
I'll maintain the "use the top as a deck" concept and will place enough
baffles in the tank, welded to the top, and use a 3/16" top too, to make
sure it is a stiff deck. Might be a gas fumes sensor in the tank area since
the drain plug from that chamber will lead into a fish box, which means
it'll be closed until the boat's back on a trailer.

Thanks,
Brian

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


"Glenn Ashmore" wrote in message
news:%79kb.79853$sp2.33451@lakeread04...
Now here I agree with Steven that tanks should be supported from below.
While the static load per inch may be low the dynamic cycling from
pounding through the waves can cause stress corrosion and cracking in
the weld. A thicker top could actually make it worse. Think about what
happens when 500 pounds of diesel bounces. The bottom of the tank
flexes pulling the sides together. The flange therefore pulls against
the weld. The top goes into compression and because metals are stronger
in compression than tension it deflects less so the weld has to bend.
Being the weakest point it will bend the most. Also having lost any
resistance to stress corrosion during the welding it will corrode faster.

If you are hanging the tank a better solution would be to at least add
angle irons across the bottom every couple of feet to reduce flexing
and possibly up the sides to mounting points on the stringers to take
the load off the weld.

Brian D wrote:
So, the bending may be OK after all...but if the lips for hanging the
tank
are bent, then a lid is welded in, the weld will run right along the
bend
that makes the lip. Probably not so good again. There must be *some*
way
to make an aluminum tank that can be suspended by stringers. I want the
top
of the tank to be 3/16" so that together with the welded in baffles,
it'll
make a stiff deck to walk on. I know lots of people who've built the
boat
that I'm building have used tanks like these, but they let them 'hang by
the
lid weldment'. The biggest tank that I know of like this is about 8
feet
long and contains 80 gallons of fuel, or about 60 pounds per foot ...30
pounds per weldment, pounding in the waves. Is that OK or are these
guys
driving around with a failure waiting to happen?

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

Fuel tank frustration
 

On Sat, 18 Oct 2003 12:39:43 -0700, w kensit
wrote:


In a sailboat, maximizing tank size is going to result in an irregular shape
with the fuel pick up at the deepest point. A sump is an unnecessary
embelishment. Water is going to be of concern only with contaminated
supply in a well designed system. If water in the fuel causes sleepless
nights tee into the fuel pump discharge so a liter or so can be pumped
into a container for disposal.

Disagree. Tanks that are less than completely full condense water
during thermal cycles, and water being heavier than gas or diesel, it
collects at the low point. This really ought to be a small sump, need
not be more than a tea cup - where it can be checked via a sampler.
Nothing stops an engine better than water in the fuel.

Brian Whatcott Altus OK

Fuel tank frustration
 

Guys, Dave Gerr (Elements of Boat Strength, pg.186) and others have
written volumes about 5000 vs. 6000 series aluminum alloys. They all
recommend 5000 series for marine applications, but caution that it's NOT
taboo to substitute 6000 series for use other than hull plate--including
non-intregal fuel tanks.
Welded aluminum sounds horribly weak from the drift of this discussion.
I guess that's why aluminum tankers supply the fuel to our local gas
stations? Think about it. That tanker you passed on the freeway this
morning held 5000 gallons of gasoline enclosed inside an aluminum
skin--0.180" sides/top and 0.220" belly--and it bridged 30' kingpin to
center of axles. The girth weld, 15' from the nearest bearing support is
a simple butt joint and was probably hand mig welded by a kid who didn't
finish high school.
Forget the semi trailer, the 50 gallon round or rectangular saddle tanks
hung off brackets bolted outboard from the truck chassis were most
likely welded aluminum and at 0.161" to 0.250" plate thickness--thicker
than they need to be--for added protection against puncture. And they
are hung--suspended by fabricated straps and/or U-brackets.
So please don't malign welded aluminum tanks. They've been the fuel tank
of choice for 50 years where light weight, low maintenance and cost
effectiveness are appreciated.
Regards,
Boat Dreams

Fuel tank frustration
 

boatdreams lifted the trapdoor, peered around and
wrote:

So please don't malign welded aluminum tanks. They've been the fuel tank
of choice for 50 years where light weight, low maintenance and cost
effectiveness are appreciated.

http://www.tek-tanks.com/

Would probably be my choice.

Fuel tank frustration
 

steveb wrote:

http://www.tek-tanks.com/

Would probably be my choice.

Tek-Tank will make welded HDPE water and holding tanks but their line of
fuel tanks is very limited. Fuel tanks have to be cross linked
polyethylene and you can't weld XLPE. It has to be rotomolded so you
are stuck with the tooling cost.

--
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

Fuel tank frustration
 

boatdreams wrote:
Guys, Dave Gerr (Elements of Boat Strength, pg.186) and others have
written volumes about 5000 vs. 6000 series aluminum alloys. They all
recommend 5000 series for marine applications, but caution that it's NOT
taboo to substitute 6000 series for use other than hull plate--including
non-intregal fuel tanks.

6000 series can be used but with limitations. First it does not weld
anything like as well as 5052 or 5086 and second it is much more
susceptible to corrosion than the 5000 series.

Welded aluminum sounds horribly weak from the drift of this discussion.

Nobody has said welded aluminum is "horribly weak" but it will loose
about 20% of its strength in the area of the weld which has to be taken
into consideration when designing the structure.

I guess that's why aluminum tankers supply the fuel to our local gas
stations? Think about it. That tanker you passed on the freeway this
morning held 5000 gallons of gasoline enclosed inside an aluminum
skin--0.180" sides/top and 0.220" belly--and it bridged 30' kingpin to
center of axles. The girth weld, 15' from the nearest bearing support is
a simple butt joint and was probably hand mig welded by a kid who didn't
finish high school.

Only about 20% of those shiny tankers are aluminum. Most are stainless.
Aluminum tankers must meet DOT406-AL standards. They have a
longitudinal structure, either chassis rails and cross members or
internal webbing to prevent excess flexing of the tank. They are also
built with 5000 series material. The design is fairly standardized and
carefully refined and that kid that welded it has 2 or 3 years of
training, uses a $5K TIG welder and lays the same bead 8 hours a day 5
days a week. The guy I am working with can hardly write his name but he
lays a beautiful full penetration bead. :-)

Forget the semi trailer, the 50 gallon round or rectangular saddle tanks
hung off brackets bolted outboard from the truck chassis were most
likely welded aluminum and at 0.161" to 0.250" plate thickness--thicker
than they need to be--for added protection against puncture. And they
are hung--suspended by fabricated straps and/or U-brackets.
So please don't malign welded aluminum tanks. They've been the fuel tank
of choice for 50 years where light weight, low maintenance and cost
effectiveness are appreciated.

It is very hard to compare automotive tanks to marine tanks. While
automotive tanks have to deal with vibration they don't get the constant
cyclical loading of marine tanks. They also don't have to contend with
a constant exposure to a highly corrosive environment.

Again, nothing wrong with aluminum tanks but they are not the ideal tank
for all situations. They do weigh between 20% and 50% less than mild
steel but they are more than twice as expensive. They are also more
susceptible to stress cracking than mild steel. Removing weight from
consideration I would rank the material for diesel tanks under about 40
gallons like this:
#1 Mild steel
#2 5086 aluminum
#3 5052 aluminum
#4 Cross linked polyethylene (XLPE)
#5 stainless steel (either 304 or 316)
#6 FRP.

Over 40 gallons XLPE drops to fifth place because of the difficulty in
adding baffles and the limited selection of stock shapes.

Now, before Lew gets to upset, ;-) because fiberglass can be molded on
site to the required space it is the most efficient for the use of
volume but it is almost impossible to keep diesel from permeating site
fabricated FRP. (duck'n and run'n) :-)

--
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

Fuel tank frustration
 

Glenn Ashmore wrote in message news:Gytkb.80009$sp2.24474@lakeread04...
steveb wrote:

http://www.tek-tanks.com/

Would probably be my choice.

Tek-Tank will make welded HDPE water and holding tanks but their line of
fuel tanks is very limited. Fuel tanks have to be cross linked
polyethylene and you can't weld XLPE. It has to be rotomolded so you
are stuck with the tooling cost.

I know this will not solve your problem, but on the twenty footer I
will be building, I planned areas such as fuel storage areas to use
common size readily available marine fuel tanks. Easily replaceable in
any marine store.
I don't need to carry as much as you, but I have two 6 gallon tanks
(mains) in the rear of the boat, with a third stored in the bow. I can
just plug them in as I need them. Just thought I would note that to
anyone else is in my situation and watching this thread.
Scotty

Fuel tank frustration
 

Sorry if this is off topic.
A few NOTs from someone with 15 years hands-on experience building
welded tanks--aluminum, steel and stainless:

First it {6061) does not weld anything like as well as 5052 or 5086

NOT. Welders don't even notice when they're moving from 5000 to 6000
unless one or the other is extrusion instead of plate. They're apt to
wire brush the extrusion a little more whichever alloy it is. They
don't change gas or rod/wire and don't even adjust their current if the
thickness and position are similar.

second it is much more susceptible to corrosion than the 5000 series.

NOT. 5083 and 5054 create a slight electrical potential and with 6061
you have slightly more. Don't use it in direct contact with salt water.
Bill Gates could afford to specify 5083 throughout a boat, but even he
could not guarantee that every piece of alloy on his boat is exactly
what he specified and probably paid for.

Only about 20% of those shiny tankers are aluminum. Most are
stainless.

NOT. ALL the shiny tankers you see dropping off fuel at the gas station
are aluminum.

They have a longitudinal structure, either chassis rails and cross
members or internal webbing to prevent excess flexing of the tank.

NOT. Truck tanks like semis and pull trailers are supported front and
back on bearing pads or short subframes. There is no longitudinal
stiffening other than the shell, rings, baffles and bulkheads that form
a structural tube. By excess flexing, you probably mean 'failure'. Any
aluminum semi tanker driver will tell you his 5000 gallon balloon flexes
with a period equal to the period of his suspension...And the first 50
years he drove the damn thing it scared the hell out of him.

The design is fairly standardized and carefully refined

NOT. There are off-the-shelf tanks and off-the-shelf boats. Every time
the customer buys a new tanker he recalculates the proportions of
regular, midrange and premium or diesel--always moving the baffles,
bulkheads and piping and often demaning a custom tube shape. Kind of
sounds like boaters. Everyone wants a 40' boat, but there are a lot of
interpretations of what goes in a 40' boat.

kand that kid that welded it has 2 or 3 years of training,

NOT. He completed a 60-day welding course at the county ROP training
site and the rest of his training was on-the-job training working with a
lead welder, definitely doing his share of weld-offs on the girth seams
of the semi-tankers we're talking about.

uses a $5K TIG welder and lays the same bead 8 hours a day 5
days a week.

NOT. All welded aluminum production tankers are mig welded. Period.
And nobody in a tank fabrication shop welds off every day. Your
aluminum hull might be a 90-day building project followed by 5 days of
weldoff. Tanker fabrication has a similar ratio of building : welding.

The guy I am working with can hardly write his name but he
lays a beautiful full penetration bead. :-)

NOT. One pass full penetration in butt welds is a myth. Your guy does
it the same way everybody else does. 1st he tacks it all together. 2nd
he runs a solid weld around the inside of the seam. 3rd he runs a
portable skill saw around the outside of the seam to remove
contamination and increase penetration. 4th the welds off the outside.

It is very hard to compare automotive tanks to marine tanks. While
automotive tanks have to deal with vibration they don't get the constant
cyclical loading of marine tanks. They also don't have to contend with
a constant exposure to a highly corrosive environment.

NOT. The Principle of Uniformitarianism assures us that the
mathematics, physics and chemistry on the 3rd rock from the Sun is the
same as on the 3rd rock from Polaris or anywhere else. Granted, the
period of waves is going to be different from the period of any given
set of trailer springs. The bending moments will differ. The number
and placement of anodes will differ. But we're talking about different
numbers, not different sciences.

Cheers,
Boat Dreams

Fuel tank frustration
 

Brian Whatcott wrote:

On Sat, 18 Oct 2003 12:39:43 -0700, w kensit
wrote:



In a sailboat, maximizing tank size is going to result in an irregular shape
with the fuel pick up at the deepest point. A sump is an unnecessary
embelishment. Water is going to be of concern only with contaminated
supply in a well designed system. If water in the fuel causes sleepless
nights tee into the fuel pump discharge so a liter or so can be pumped
into a container for disposal.


Disagree. Tanks that are less than completely full condense water
during thermal cycles, and water being heavier than gas or diesel, it
collects at the low point. This really ought to be a small sump, need
not be more than a tea cup - where it can be checked via a sampler.
Nothing stops an engine better than water in the fuel.

Brian Whatcott Altus OK

Which all the more reason to end the season with full tanks. The only
time I experienced problems was from a load of contaminated fuel in mid
summer. My point is that unless your tank has a large flat bottom you
are in fact adding a sump to a sump.

Fuel tank frustration
 

Brian Whatcott wrote in message . ..
On Sat, 18 Oct 2003 12:39:43 -0700, w kensit
wrote:
....
Nothing stops an engine better than water in the fuel.

Other than me putting a wrench on it! ;) Scotty

Fuel tank frustration
 

Brian,

Something a tank builder in RI suggested to me was mounting the tank on
something like UHMW material attached to the tank with 5200. That way no
water can get between the mounting device (UHMW pad) and the Al tank.
That would take care of keeping the tank from going any lower (gravity
again) and I guess straps across the top, but there you go again with a
water entrapment problem. Maybe more UHMW pads and a strap over them?

I'm leaning more and more toward a plastic tank, looking for a small one
but it has to fit under the cockpit and behind the mizzen step of o my
Kenner Privateer 26, a bit over 10 gals would keep me quite happy.

And I found out just the other day that Todd no longer makes the small
tanks, apparently only larger ones.

Do the makers (Tempo and who else) put baffles inside these plastic tanks?

Dave Cannell
--
In article %L4kb.805694$Ho3.219150@sccrnsc03, Brian D wrote:
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

Fuel tank frustration
 

Hey! Now we're talking. I can use SikaFlex 291 to put UHMW (thin) on the
bottom of the hull or whatever support stringers I put in (removable), then
use 3M 5200 to put UHMW strips on the bottom of the tank (permanent). No
water can gather between the tank and the support materials, nor between the
support materials and the epoxy/glass/wood either, and the UHMW will prevent
chafing forever...

Thanks for the inspiration ...I think I have a solution: custom tank, and
artful use of UHMW and supports!

Brian


"Dave Cannell" wrote in message
.. .
Brian,

Something a tank builder in RI suggested to me was mounting the tank on
something like UHMW material attached to the tank with 5200. That way no
water can get between the mounting device (UHMW pad) and the Al tank.
That would take care of keeping the tank from going any lower (gravity
again) and I guess straps across the top, but there you go again with a
water entrapment problem. Maybe more UHMW pads and a strap over them?

I'm leaning more and more toward a plastic tank, looking for a small one
but it has to fit under the cockpit and behind the mizzen step of o my
Kenner Privateer 26, a bit over 10 gals would keep me quite happy.

And I found out just the other day that Todd no longer makes the small
tanks, apparently only larger ones.

Do the makers (Tempo and who else) put baffles inside these plastic tanks?

Dave Cannell
--
In article %L4kb.805694$Ho3.219150@sccrnsc03, Brian D wrote:
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