Conference vicki::boats

    There was a big article about this in Powerboat Reports a while ago.
    As I remember the claim was that this was simply another example of
    the marine industry continuing to do things "because they've always
    done it that way" (like non-EFI engines).   Cross-link polyethelyene 
    tanks are stronger, completely corrosion resistant, don't need to
    be inspectable, and are not significantly more expensive.  In short,
    there is no reason other than inertia for not using them (at least
    according to this article).

    	I've often wondered about my Aluminum tank. Its sealed under the
    deck but I assume eventually problems will arise. Has anyone out there 
    had any problems? 
    	The tank is 5 years old now. I hate the thought of it but I was going 
    to remove the deck cover this year; inspect, reassemble and reseal it 
    (assuming everything is okay). Am I overdoing it?
    	Also does anyone have experience or in depth knowledge about the 
    cost vs longevity of the polyethelyne tanks or others?
    Thanks,
    Paul   

I checked mine last year.  It's not a difficult job; just reseal when done
I found the factory had not installed the gound wire very secure and that
one clamp was slightly loose.  I feel a lot better about it, knowing it's not
leaking.

The reason I checked it was the season before a couple of times I smelled 
fumes after gasing up.  I wanted to make sure it was just the calm day and not
a small leak in the tank.

Gordon

    
      I've experienced/hassled with/lived through aluminum and stell tanks
    springing leaks. My Larson has a poly tank and I am VERY happy that it
    does..
    

    I have a galvanized steel tank in my 27 year old Century and there is 
    absolutely no signs of rust or corrosion at all but if I were ever to
    replace it, I would certainly use a poly tank.  You don't see them
    using metal tanks for in ground gas storage at gas stations anymore
    because they just can't afford the chance of a law suit caused by a
    leak.
    Wayne
    

    re: .5
    
    I ass-u-me the reason your tank has lasted so long as that your's
    is a fresh water boat.  Steel or aluminum are both very succeptible
    to salt of course, but are generally OK for fresh water use only.
    The problem lies in that the boat mfg'er has no way of knowing what 
    the boat will be used for, so poly tanks are becoming more popular.
    
    Another advantage of poly, is that the tank can be custom molded
    to fit an odd shape.  The tank in the Sunbird I owned was shaped 
    to fit a very restricted space, and would not have been cost effective
    to build from steel or aluminum.
    
    Rick

    
    Rick - While you're right about steel and aluminum being very
    suseptable to corrosion in a salt water environment, there are ways
    around it. There are alloys of aluminum that are very long lived even
    in the worst of salt environments. I don't know exactly their names,
    but for example. On my father's boat. It has a built in 90 gallon
    aluminum tank. This boat has seen as harsh a salt water use as I can
    imagine and yet, the aluminum of this tank is not corroded at ALL after
    7 years of this use. 
    
      Of course the problem is that you can never tell if you have 
    the 'good' aluminum or not. I'm sure that many manufacturers
    count on the boat seeing limited salt use or lake use and like
    everything else, tradeoffs are everywhere. I really like the poly tanks
    too, but for some reasons (which I can guess at but do not know) they
    have been very slow to gain acceptance. I know that within the last few
    years it was still illegal (to the Federal Department of
    Transportation) to use poly tanks on motorcycles, while steel, aluminum
    and fiberglass were all ok. I don't know why for them. I DO know that
    older and/or cheaper 'poly' tanks allowed some migration of fuel through
    them. I don't know if it was the precise material or the thickness or
    what. That would of course be disasterous for a boat.
    
    					Kenny

re: .7
Kenny,
I'm no metallurgist so I'll take your word that there are grades of
aluminum that are extremely resistant to salt.  The problem then is,
like stainless hardware, deck rails and fittings, fiberglass resins,
etc. in "new" condition they all look the same.  So only a few of the 
best mfg'ers will spend the extra bucks to use the best material 
available for longevity.  The rest of them will choose to save a few 
bucks, since about 99% of boat buyers won't know the difference til 
the stuff starts to deteriorate anyway.

I s'poze you could ask the mfg'er which grade of aluminum they're
using.  Those using the good stuff will be proud to tell you. If
they "don't know", you can probably assume it's the lesser quality.

After everyone switches to "plastic" tanks, we'll probably find that
there are good grades of plastic tanks and cheap grades of plastic
tanks.  Naturally, most boat mfg'ers will automatically pick the cheap 
stuff.  (Pardon my skepticism...).   8*)

Rick

    Is there a proper grounding issue when using built in plastic tanks?
    I think of the possibility of a spark at the fuel fill nozzle to a
    nearby fitting.  But I suppose that plastic being a non conductor
    answers that.
    
    Jeff

    
      I know what you mean Rick and I agree. Most boats have the 'cheaper'
    grades of metals and such. Hey it all looks good in the showroom. It
    really is a reason why some boats (Like Bertrams) cost so much more
    than some 'similar' boats. I'm sure that will never change. You get
    what you pay for.
    
      As an example. The tanks in my father's old boat (Annacapri) were
    VERY thick (more than 1/4") aluminum. THOSE tanks corroded a fair bit,
    but they were also made much thicker than they needed to be. Maybe
    the builder traded off with thick for cheaper metal?
    
    				Kenny

    re.9
    
      Jeff - You're right. It is not possible to ground plastic. The metal
    fuel fill should certainly be grounded.
    
    					Kenny

    Aluminum is aluminum, and it gets corroded by saltwater.  Yes, you
    can do the same things as with steel (make it thick, use exotic
    "stainless" alloys, use all manner of anti-corrosive coatings, etc).
    And this will give you a quality tank, but it will then cost a *lot*
    more than a poly tank with the same strength/longevity/etc.  So why
    bother?
    
    

    Just as an aside on the issue of metals used in boat building is that I
    recently read an article on the truth about stainless steel - And it
    seems that there is a huge range of types available, and interestingly
    enough the highly touted "316" type which the high end boatbuilders
    claim to use (and furthermore claim is the "best"), isn't even close to
    mid-range on the overall scale (topped by stuff made in Sweden used in
    surgical instruments and ultra high-precision machinery, and wickedly
    expensive).   I would imagine Aluminum is produced in a similar range
    of types.
    
    There always seems to be something better than the "best" when it comes
    to boatbuilding materials. 

re: .13
Yep, I've seen a few articles recently on the quality of (or lack thereof) 
stainless hardware used in boats.  That's what I was allluding to in .8
when I said "like stainless hardware, deck rails and fittings, fiberglass 
resins, etc. in "new" condition they all look the same.".

There are different grades of stainless, and from what I've read, there's
a lot of foreign stuff being imported that is of *very* poor quality. And
it's actually being used in boats.  A recent issue of BOAT/US reports
mentioned something about this, and said that there have been documented
cases of boats even sinking because of low quality clamps and hardware.

The problem is, there's no way for a boat buyer to verify the quality of 
every piece of hardware that goes into his/her boat.  You rely on the mfg'er 
to do that.  And in the highly competitive boat market, where the emphasis 
is on delivering a high quality boat at a relatively low price, stuff like 
this is what gets scrimped on.  If you buy an ultra cheap boat, at least 
you know that this is what you're getting. If you buy a Bertram or a Hatteras
you know you're getting the good stuff.  If you buy a mid-priced boat, you 
can probably assume that there are some top quality parts and some el-cheapo 
parts.  The question is, which ones?  The answer I guess is, "you'll know in
about 5 years".

Rick

re .1:      

>>> Cross-link polyethelyene tanks are stronger .....

How do you reach this general conclusion? The last time I looked at the 
physical properties of polyethylene, its tensile strength, etc, were 
less than those of steel or aluminum. It seems to me that no general 
strength comparision is possible. Some polyethylene tanks may be 
stronger than some metal tanks, and visa versa. And what do you mean by 
stonger? Impact resistance, tensile strength of the materials, 
resistance to chafe, etc?

re .others

Small tanks without internal baffling can be easily (cheaply) molded,
but large tanks, with proper baffling to keep the fuel from surging in a
rough sea, might be as expensive as a properly made metal tank. 

The 45 gallon aluminum diesel fuel tank in my boat is now 13 years old 
and shows no visible corrosion. It is accessible enough that it can be 
washed with fresh water easily (my boat has lived its entire life on the 
ocean). The tank has enough internal baffling that I've never heard the 
fuel sloshing inside even in quite rough seas. 

Another thought: What is the melting temperature of polyethylene? In the 
event of a fire, I'd suspect that a plastic tank would be considerably 
more likely to melt, which would have truly disastrous results. Are 
plastic tanks approved by the Coast Guard for passenger-carrying 
vessels? 

Finally, if a metal tank develops a small leak, there is some hope of 
temporary repair using epoxy or something. I've never found anything 
that bonds effectively to polyethylene. This might be a significant 
consideration for boats used in out of the way places far from 
specialized plastic tank builders or even just well offshore. 

    I too wondered about the fire risk with poly tanks.  But I figured that
    if there is a fire the construction of the won't matter much for long.
    Flames externally licking a metal or poly tank would heat the fuel and
    cause the fuel to blow out the vent and fuel fill likely catching on
    fire.  The boiling fuel would 'cool' the tank (like a paper cup
    full of water on a campfire) at least to the liquid level.  The 
    poly tank would melt/burn through above the fuel level very quickly
    and expose a large expanse of fuel to air thus propogating the fire
    quickly, whereas the metal tank (Aluminum) would hold out longer than
    poly before melting.  But as I said in the first line, once you have
    a fire involving the fuel tank I suspect the tank material won't matter
    much for long.  So you have to weigh the lack of corrosion and the various
    other plusses for poly against the minus of it.  The chances of a fuel
    tank fire in any given boat are low, so the other plus factors for poly
    may make them very attractive.
    
    Jeff

    
    I agree, if there's a fire, and all of us are "gas burners" 
    
    metal or poly won't make much difference. I'll say one thing
    
    if there's a fire, i'm gone, i ain't hangin to find out which
    
    one is better.  I have a poly water tank, and i can see the 
    
    expansion when it full.  How about a poly lined alum. tank.
    
    
    JIm.

re .16:

The chances of a fire involving the fuel tank probably depend on the
particular boat. On some boats the fuel tank is not close to the engine,
on others it is. On our boat, the 45 gallon aluminum fuel tank is about
a foot aft of the engine, so that any fire around the engine will
certainly involve the fuel tank. Our diesel engine has multiple fuel
filters, shut-off valves, high-pressure injector lines, etc, and a fuel
leak isn't unlikely. Last summer, in fact, an O-ring on the injector
pump failed, and rather a lot of diesel fuel found its way into the
bilge. (Thank the gods it wasn't gasoline.) The vent on our tank is
copper pipe and any vented fuel is discharged overboard through the
transom. 

Moreover, there is a not insignificant chance of an electrical fire
around the engine. We have a 100A alternator charging three batteries
and the power bus to the power panel runs over the engine. The 
alternator is also about a foot from the fuel tank. 

Finally, two 10 lb propane tanks for the stove live maybe four feet
from the engine and less than a foot aft of the aft end of the fuel tank. 
The propane piping is well away from the engine. 

The non-corroding virtues of plastic tanks notwithstanding, on my boat I 
prefer a metal tank.

    re prior.  I thought copper wasn't supposed to be used with diesel
    fuel?  You mentioned the diesel fuel tank vent pipe is copper.
    Something about a chemical reaction between diesel and copper.
    
    
    Jeff

    
    Alan, i question the legallity of the propane tanks in their
    
    current location...???????????????
    
    
    JIm                 (seems a fire and diesel fuel arn't your problem)
    
    
    

re .20:                    
    
>>>    Alan, i question the legallity of the propane tanks in their
>>>    current location...???????????????
    
Both quite legal and quite safe. The tanks are in a compartment sealed
from the interior of the boat. The compartment has an overboard drain
for accumulated water and a vent. The compartment just happens to be
quite close to the fuel tank. The system also includes a pressure gauge
for leak detection. Our boat passed a careful professional seaworthiness
and insurance survey before our trip to Bermuda. 

re .19:

The copper vent pipe comes out the top of the tank and goes to a through 
hull fitting near the deck. There is virtually never any liquid diesel 
fuel in the vent pipe. However, I've never heard of any problems with 
copper and diesel fuel. Most fuel line fittings and shut-off valves 
are brass (a copper alloy). 

    For a compartment vent the copper would be ok.  But for FUEL (diesel
    not gas) I am almost positive copper is a no no.
    
    Jeff
    

re .22:

"FUEL PIPING
	We recommend copper tubing together with suitable fittings, both 
for the supply line and the return line."

Factory technical manual, Westerbeke L25 diesel (one of which we've 
owned for 13 years)



Copper fuels tanks are not recommended because the diesel fuel
apparently reacts with the solder used to construct the tanks. None of
the many boatbuilding and diesel engine books in my library say anything
about not using copper fuel lines. 

    re: .15
    
    (Strength of poly)
    
    As I understand it, we are talking about a relatively new form of
    polyethelyne called "cross link", which I suppose refers to some 
    exotic arrangement of molecules.   According to what I read, this
    stuff is stronger than aluminum in all aspects - tensile strength,
    impact resistance, chafe, etc.   
    
    I don't necessarily believe that all new hi-tech stuff is better, but
    in this case, I don't understand why you would want to stick with
    aluminum of the claims for this material are true.  It would appear
    to be no contest,,,
    

    What do they use for fuel cells in race cars?  Could that be adapted
    for use in boats?  I would think that a race car's fuel cell must be
    designed to be very shock and flame resistant so that the driver
    doesn't get fried in a major accident.  We've all watched films of
    crashes where the car totally disintergrates but hardly ever any fires
    occur.  Why?
    Wayne

    re: .25
    I had a fuel cell in a street driven car I owned several years ago.
    It was made by ATL (Aero Tech Labs), and was a steel tank with a 
    foam filled rubber bladder inside.  I believe some of the newer 
    versions are made with an outer skin of hi-tech plastics or resins.
    A steel tank probably wouldn't be a good choice for marine use.
    
    The cost of a fuel cell for marine use could also be prohibitive. 
    The one in my car had been installed by the previous owner, but I 
    seem to remember he paid over $300 1975-vintage dollars for the
    20 gallon model.  It could be that prices have come down since then,
    but it's still an expensive option.  Production model fuel cells 
    also only come in standard square or rectangular shapes, which 
    isn't always the best fit in the space available in a boat.  For
    custom fitted applications, molded plastic tanks still offer the 
    most flexibility and best use of available space.
    
    Rick

    Ok on the soldered copper tanks.  I knew that I had read somewhere that
    copper (lead) and diesel don't mix.
    
    Jeff

	As for Race Car's I believe they have built in Fire Supression Systems
	like halon (sp?) or some foam type which activate upon hard collision?


	My guess anyway
	-< Tuna Tail >-

    re: .28
    Yes, but the halon fire supression system is totally independent of 
    the fuel cell or tank.  You could aim a halon nozzle at the tank, 
    but the two are essentially independent systems.
    
    The foam inside a fuel cell is not for fire extinguishing. It's an
    open cell foam that absorbs fuel, and is primarily to prevent sloshing
    which can throw off the car's balance. It will also help prevent fuel
    fuel from gushing out as quickly if the tank ruptures, but will not
    prevent spillage and a resulting fire.
    
    Halon systems of course are as popular in larger or more expensive 
    boats as they are in rece cars.  The systems are activated by heat, 
    so by the time they're activated, it's a bit late if the heat source 
    is a major fuel explosion. The primary goal is to prevent leakage by
    using the best available tanks, lines, and periodic inspections. What
    the best tank material is, is what seems to be open for debate. Each
    type has pro's and con's, like anything else.
    
    Rick

    If I remember correctly, the characteristic aluminum tank failure is
    stress, not corrosion, induced.  It typically occurs at the point at
    which an internal baffle is attached.  I'll try to put in a pointer to
    the Powerboat Reports article.
    
    Note that a welded seam failure has the potential to suddenly release a
    large ammount of fuel, and a sudden failure of this sort would be most
    likely to occur in the worst conditions, i.e. rough seas...
    
    J

    
    A slight correction on Halon.  Halon is normally used in a closed
    comparment i.e. your engine area. The idea behind Halon is that
    when Halon represents 5% or more of the enviornment, a fire
    cannot be supported.
    
    How do they do this in a race car.
    
    JIm.    
    
    

    re: .31
    Halon is used in race cars, although with well ventilated engine
    compartments and all, it'd probably not as effective as in the
    engine compartment of a boat.
    
    Some race cars, such as funny cars, which are likely to become
    *extremely* well ventilated after a blower explosion pops the
    body off the car, still use a powder type extinguisher.  It
    makes quite a mess though!
    
    Rick

re .24:

I looked at some data sheets and plastics catalogs last night. I 
couldn't find specific physical data on cross-linked polyethylene, but .....

The tensile strength of high-density polyethylene is on the order of 
15000 or so psi. The tensile strength of ordinary aluminum alloys is 
around 50000 psi and much higher for more exotic alloys. It seems 
unlikely to me that the tensile strength of cross-linked polyethylene is 
three or more times greater than that high-density polyethylene. The 
tensile strengths for plastics seem to be in the 5000 to 15000 psi 
range (including polyester and epoxy resins).

The maximum recommended working temperature of cross-linked polyethylene 
was listed as 100 deg C (212 deg F). This would imply that temperatures 
below those of an open fire could be a problem. 

Cross-linked polyethylene was not recommended for storing kerosene or 
fuel oils. High-density polyethylene seems to be ok. 

Cross-linked polyethylene cannot be welded, ie, a tank made from it
cannot be easily repaired if it can be repaired at all in case of damage
or a leak. 

There was some not very clear data that indicated that plastic tanks are
to a small extent permeable to water as well as to the contents of the
tank, meaning that water can get into the tank through the walls and the
contents (eg, gasoline) can get out. Presumably increased wall thickness
minimizes this. 

It would appear that the exact composition of the plastic used in tanks 
is critical -- just any old stuff may not work. 

By the way, fiberglass/polyester tanks (which are used for fuel) are
permeable to water also, with the result that tanks integral to the hull
can be contaminated by water (which is not at all a good thing,
especially with a diesel engine). 

So, it looks to me like one needs to be very careful about the materials 
used in making a plastic tank and the construction before buying one. 

Oh yes, the capacity of the tank should not exceed 25 gallons without
internal baffling, according to one of my references. Molding a tank 
with internal baffles might be difficult (see non-weldable above). 

Alan

    The best discussion that I have read on problems associated with
    aluminum fuel tanks was in Powerboat Reports, Volume 5, Number 1,
    January 1992.
    
    I scanned the article last night and they mentioned corrosion and
    hairline cracks at baffle welds as the two major causes of failure.
    
    J

re: .29
	Rick,
		Thanks for the update on Halon for cars.
		Wasn't sure about the details.
		I guess the powder type mentioned in anohter note would
		definetly make a mess on the track.  Watching races in
		the past I alway's wondered how they clean this powder mess
		up after it layers the track?
	Dick

	PS: regarding your personal name....I can't be blamed either ;-)
					    Neither can my wife ;-)

    Not meaning to get off track here, but I read somewhere that Halon
    would be banned in a few years as a part of the stricter EPA guidelines
    due to kick in in a few years. (The same ones that are causing outboard
    manufacturers to scramble to clean up their two strokes or develop four
    stroke engines.)  I was going to install a halon system in my engine 
    doghouse but won't bother if it is going to be outlawed.  Is this true?
    Wayne

    
    I think its on the table, however, i understand its very expensive
    to get a refill.  Something call a "Tax".
    
    JIm.

    re: .37
    Jim, so essentially what you're saying is, halon will still 
    be available and it'll be OK to deplete the ozone and all, as
    long as the guv-mint makes money on it?
    
    Nah, that sounds too far fetched.   8^)
    
    Wayne, as long as your conscience (I'm not judging one way or
    the other, although a burning boat is bad for the environment 
    too) allows you to install a halon system, go ahead and do it.
    If halon does become illegal or sin-taxed, I can't imagine that 
    it would be made retroactive and that they'd come and take your 
    halon system away.  Just hope you don't ever have to discharge 
    it, refilling could be expensive or impossible.
    
    Rick

    Rick, what about outboard emission on older outboards.  Will stricter
    emission controls in your opinion be retroactive to older engines
    (shudder) or will they be grandfathered with the new emission standards
    applied to new engines being sold?
    
    How are you doing anyway?
    
    Jeff

    
    Rick, Halon is only a hazard when discharged. Unless we have 
    a rash of boat fires, we don't have a major problem.
    
    Here's what i remember reading, is that it would be sin taxed
    until a substitute i found.
    
    JIm

re: .39
>> Rick, what about outboard emission on older outboards.  Will stricter
>> emission controls in your opinion be retroactive to older engines
>> (shudder) or will they be grandfathered with the new emission standards
>> applied to new engines being sold?
   
    When the new emissions standards come in, older motors will definitely
    be grandfathered, just like older cars were.  Otherwise, billions of
    dollars in boats and motors would have to be scrapped.  Besides, how 
    the heck am I gonna bring my 1927 thru 1950's outboards up to 1990's 
    standards!?  8^(

>> How are you doing anyway?

    Simply mahvelous.  Waiting for spring - got cabin fever REAL bad. Did
    some moonlighting this past weekend, worked a boat show for a local 
    dealer and sold my my first new boat!
    
    How are you doing?
    
    Rick