CFR Commercial requires that metal
diesel tanks be made only of nickel-copper,
steel or iron, aluminum, or fiberglass. Stain-
less is not accepted. Further, CFR Commer-
cial insists that all aluminum tanks—even
tanks of just 1 or 2 gallons (3 or 4 L) be a min-
imum^1 / 4 inch (6.35 mm) thick. This is con-
siderable overkill for such small tanks, in my
opinion; however, if you’re building a crewed-
charter or passenger vessel, you must
comply.
Except for integral tanks, tanks cannot
be used as part of the structure. You cannot
mount or attach machinery to tanks.
Aluminum Tank
Preservation
Marine aluminum tanks are probably the
most common fuel tanks. They’re relatively
inexpensive to fabricate into custom shapes,
and they are robust and fairly light. They
have just one serious drawback: they can cor-
rode. If aluminum tanks have been installed
with proper ventilation all around, with
sloped or rounded tops to drain water, and
placed on proper chocks with Neoprene
padding they’ll last a long time. For really
long life, however, aluminum tanks should be
painted (on the outside only) with a good
epoxy-based paint system (Figure 5-16): a
prime coat plus at least two finish coats
(three or four are better still). An aluminum
tank built and installed like this will last a
lifetime.Glass Tanks
and Integral Tanks
Interestingly, fiberglass tanks are not only
acceptable, but also superior for diesel.
(They were once superior for gasoline, too,
but ethanol has changed this. See sidebar
“Fiberglass Tanks and Ethanol.”) FRP tanks
have some great advantages: they don’t cor-
rode, they don’t conduct electricity, they
weigh less than metal tanks, and they can be
molded to fit the hull more closely than any
but the most expensive metal tanks, yielding
greater tank capacity. Bertram and Hatteras
are just two of the quality builders who install
fiberglass tanks.
Though the CFR Yacht and Commercial
rules permit integral fiberglass tanksChapter 5: Fuel Tanks and Fittings
Figure 5-16.
Painted alu-
minum wing
tanks