[PUP] Fuel management ( was: Fuel consumption )

[Truelove39 at aol.com]

Hi Arild - 
 
Congrats on the new job! Must be nice to work in a NA office. I worked with  
some of those folks and long ago was a member of SNAME myself but let it  
lapse. Amazing stuff, what those guys know. 
 
We like the two tank system much better than the one on the  sailboat, where 
we have one large center tank and two smaller wing tanks to feed  the main. 
Here is how we manage our two-tank FO system on Seahorse:  Our P&S tanks are 835 
gallons each located under the galley sole  forward of the ER. At 7 knots and 
2.2 GPH we can travel far and can't see a  difference that the extra 5 tons 
makes. But our prismatic is better  than that of a trawler hull. Management is 
easy - we supply the ME  from the stbd tank and always transfer to it from the 
port  tank. Reason being that we have a slight list to port with equal tank  
levels and so use the fuel to keep an even keel. Transfer takes place through  
a Racor 800D recycler/blender, so the fuel in the stbd tank is always  
water-free and clean to 10 microns. Filling only one tank from  shore makes fueling 
easier. 
 
There is also a 40 gallon day tank aft, filled via a separate line from the  
Racor. That tank serves the heating plant and the pony engine, but can also 
feed  the ME if needed. We don't have a problem with condensation because the  
tank tops are below the waterline and so the temperature is stable. We  really 
think this concern with condensation from "breathing" moist air through  the 
vents is overblown. Seahorse is out of the water for 4-5 months a year  in 
North Florida where, in winter, there can be large temperature changes  daily, and 
we have never had a problem with condensate. We think this particular  bit of 
concern comes from metal boats with skin tanks. We stopped  using Biobor and 
the like years ago and have never had a problem with  the dreaded critters. 
Biobor has problems of its own. A while back someone  mentioned getting a 
desiccant cap for the vent on a hydraulic SG tank. Sounded  like a good idea to me. 
Our tank is in the ER, and the oil temp runs about 160F.  Must be some water 
in the bottom, I thought, as I had neglected to check since  buying the boat 
almost 3 years ago. There wasn't.
 
Regards,
 
John
"Seahorse"
 

> Scott, you have touched on a key point.
FUEL MANAGEMENT and  tankage arrangement should be one of the key design
elements when considering  a vessel design.
Having one or two large tanks may prove a handicap in  dealing with a large
quantity of bad or questionable fuel.
Several smaller  tanks may be a better bet despite the increased cost of
additional piping and  valves.





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