Re: T&T: Fuel Tank Materials
Last winter, I replaced the four fuel tanks on our 1985 Defever 49 RPH
because of a leak that developed in one of the aft tanks. As it turned out,
the forward tanks were still in perfect condition. This was not determined
until after the new tanks were already being fabricated.
The original tanks were 3/16" mild steel. The leak was caused by the drain
fittings on the aft tanks being located about one inch above the bottom of
the tank. Condensation would settle to the bottom and it was impossible to
remove it without draining the tank and taking off the access plate (which
was never or seldom done). The leak developed below the drain fitting where
water had set for years. Had the fitting been located at the bottom of the
tank and equipped with a valve (plugged of course), it would have been easy
to periodically drain all the water from the tank.
Another installation problem was discovered after removing the acoustical
tile from the aft tanks. The engine room air intakes were originally
located on the sides of the hull which would allow water to splash onto the
tops of the fuel tanks. This was corrected by one of the PO's. However,
there was a narrow area where dirt had collected and this water kept it
moist and considerable rusting was evident on the outsides of one of the
tanks in this area. This exterior rusting was concealed by the acoustical
tile.
The original tanks were cut out using a reciprocating saw. The entire
bilge area was painted with two coat of "Bilgecoat" and the acoustical tile
on the overhead and bulkheads was replaced with FRP paneling of the type
found in restrooms. I had new tanks fabricated from 1/4" 5086 Aluminum.
Each baffled section has an access plate for ease of cleaning. The cost of
the fabricated tanks including access plates and all welded fittings was
approximately $7500. The tanks were pressure tested to 5 psi. Aluminum was
selected because the new tanks would have to be man-handled into place and
steel would have been too heavy. I followed the suggestions on David
Pascoe's website for mounting which requires 1/4" fiberglass sheet pads
glued to the tanks with 5200 to prevent any water collection next to the
aluminum. These pads then set on Buna N rubber for cushioning.
During this project, the batteries and inverter were moved to back of the
engine room which is cooler than the original location. All battery cabling
and switches were replaced. New copper fuel lines and all fuel valves were
installed. New supports were constructed for the air conditioners and
battery boxes along with new shelving for oil storage. All wood items were
coated with two coats of CPES followed by two coats of Bilgecoat. The total
cost of the project including the tanks was approximately $15,000 and
involved about 1000 hours of my labor.
I elected not to coat the aluminum tanks for fear of moisture collecting
between the coating and the aluminum. Aluminum self heals and will last a
lifetime if kept dry. I would prefer mild steel for a diesel fuel tank if
the weight can be handled. I will not cover the sides of any tanks as this
conceals potential problems. Getting rid of the acoustical tile gives an
easier to clean surface and as far as I am concerned, did not increase the
sound level appreciably.
Gary Brobst
m/v Waypoint
49' Defever RPH
In the courtyard of Oak Harbor Marina
Slidell, LA
My tanks are still in good shape as far as I can tell but in the 7 years
I've owned her, I've never done anything to my tanks. I have wondered in
the past however about this possible eventuality and considered how I'd do
this. The only way I can see is to cut BIG holes on either side of the
hull. Otherwise it's wreck out the salon and pull the engines. So Gary,
how'd you do it?
Greg Bowers www.seaplanetearth.com
-----Original Message-----
From: trawlers-and-trawlering-bounces@lists.samurai.com
[mailto:trawlers-and-trawlering-bounces@lists.samurai.com]On Behalf Of
Gary Brobst
Sent: Saturday, September 17, 2005 7:00 AM
To: trawlers-and-trawlering@
Subject: Re: T&T: Fuel Tank Materials
Last winter, I replaced the four fuel tanks on our 1985 Defever 49 RPH
because of a leak that developed in one of the aft tanks. As it turned out,
the forward tanks were still in perfect condition. This was not determined
until after the new tanks were already being fabricated.
The original tanks were 3/16" mild steel. The leak was caused by the drain
fittings on the aft tanks being located about one inch above the bottom of
the tank. Condensation would settle to the bottom and it was impossible to
remove it without draining the tank and taking off the access plate (which
was never or seldom done). The leak developed below the drain fitting where
water had set for years. Had the fitting been located at the bottom of the
tank and equipped with a valve (plugged of course), it would have been easy
to periodically drain all the water from the tank.
Another installation problem was discovered after removing the acoustical
tile from the aft tanks. The engine room air intakes were originally
located on the sides of the hull which would allow water to splash onto the
tops of the fuel tanks. This was corrected by one of the PO's. However,
there was a narrow area where dirt had collected and this water kept it
moist and considerable rusting was evident on the outsides of one of the
tanks in this area. This exterior rusting was concealed by the acoustical
tile.
The original tanks were cut out using a reciprocating saw. The entire
bilge area was painted with two coat of "Bilgecoat" and the acoustical tile
on the overhead and bulkheads was replaced with FRP paneling of the type
found in restrooms. I had new tanks fabricated from 1/4" 5086 Aluminum.
Each baffled section has an access plate for ease of cleaning. The cost of
the fabricated tanks including access plates and all welded fittings was
approximately $7500. The tanks were pressure tested to 5 psi. Aluminum was
selected because the new tanks would have to be man-handled into place and
steel would have been too heavy. I followed the suggestions on David
Pascoe's website for mounting which requires 1/4" fiberglass sheet pads
glued to the tanks with 5200 to prevent any water collection next to the
aluminum. These pads then set on Buna N rubber for cushioning.
During this project, the batteries and inverter were moved to back of the
engine room which is cooler than the original location. All battery cabling
and switches were replaced. New copper fuel lines and all fuel valves were
installed. New supports were constructed for the air conditioners and
battery boxes along with new shelving for oil storage. All wood items were
coated with two coats of CPES followed by two coats of Bilgecoat. The total
cost of the project including the tanks was approximately $15,000 and
involved about 1000 hours of my labor.
I elected not to coat the aluminum tanks for fear of moisture collecting
between the coating and the aluminum. Aluminum self heals and will last a
lifetime if kept dry. I would prefer mild steel for a diesel fuel tank if
the weight can be handled. I will not cover the sides of any tanks as this
conceals potential problems. Getting rid of the acoustical tile gives an
easier to clean surface and as far as I am concerned, did not increase the
sound level appreciably.
Gary Brobst
m/v Waypoint
49' Defever RPH
In the courtyard of Oak Harbor Marina
Slidell, LA
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