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Subject: Re: TWL: CHB 34 fuel tank curse
From: Mark Richter (Richter-Pooh@XXX.XXX)
Date: Mon Dec 02 2002 - 12:16:05 EST
<<Did the list ever decide the ideal material for replacement
diesel tanks?>>
There is no "ideal" material for fuel tanks; each material has
advantages and disadvantages. Mild steel (commonly mis-called
black iron) is inexpensive and needs little skill to weld
properly, so it is often used in Taiwan built boats and large
displacement ocean crossers.
Aluminum is lighter in weight, and slightly less subject to
corrosion; most smaller (say, under 150 gal) replacement tanks
are of aluminum. Alloys 5083 and 5052 are good for tanks. For
normal shaped tanks of 100-150 gal, figure about $6-8 a gallon.
Be very careful that any metal parts in contact with the aluminum
tanks are compatible; no copper or brass. Don't mount any metal
tank in contact with surfaces that are likely to remain damp.
Prime the tank outside with zinc chromate primer, and then coat
with a good enamel or epoxy paint.
Fiberglass may be the best material for diesel tanks, since it
won't corrode. But making custom one-off tanks of fiberglass is
likely to be expensive. Make sure the fabricator knows what he
is doing. Ask for references and check them.
Finally, try to design your new tanks so that the lowest point
isn't a big flat, horizontal plate. Some "V" to the bottom, or
slope in the installation can help prevent having a large amount
of undrainable volume, where water and sludge will collect. I
prefer a bottom-tapped drain with a ball valve for cleaning out
water and sludge, as required on aircraft. Some tank companies
don't like to add this feature, since it is Coast Guard
prohibited on Gasoline (but not diesel) tanks.
=====
Mark Richter, M.E., aboard M/V Winnie the Pooh,
custom Morgan 46 Pilothouse Efficiency Trawler.
"Mark's Mobile Marine" electrical systems repair & consulting. Homeport Stuart, FL
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