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From: Arild Jensen (no email)
Date: Sun Mar 02 2008 - 18:00:44 EST
> -----Original Message-----
> From: Robin Brueckner wrote:
> I have always been concerned about drawing fuel from multiple tanks
> simultaneously because glop or water in either means both engines are at
> risk, <snip>
REPLY
Drawing from multiple tanks simultaneously also ignores many decades of
experience and sound practice by professional mairne engineers on ships. In
essence you lose control of your fuel management.
The preceding discussion seems to involve only two tanks both installed at
the same level.
Rob rightly pointed out the main disadvantages. Ther are however other
configurations wher two or more tanks are installed at differnt levels. One
obvious use is to have at least one tank mounte dhigh enough to provode
gravity feed to the engine mounted lift pump. A second useful is the
designantion of one of these tanks as a "day tank" Fuel transfer witin th
evessel should only be done vi a fuel polishing system.
The engien shoudl always draw from one tank which is also designated the
"clean fuel" tank. By always transferrring fuel on a frequent basis you
know that the fuel pumped to the designated clean fuel tank is filtered.
This should to a large extent eliminate any issue with stale fuel, water
and biological crud build up in a tank etc.
An elevated "wing" or "day" tnak usually also means the very bottom of the
tank is accessible and facilitates the installation of a bottom drain to
draw of any acumulated water.
A belly tank makes the most sense from a stability point of view. Wing tanks
of substantial capacity can help in managing vessel trim.
The more I learn about yacht design the more I appreciate and now miss the
features on my very first boat.
It had nearly all the features we now discuss as being desirable. I now
realize that those old time boat designers probably knew and had forgoten
more about real yacht design than most contemporary buat building yards now
know.
My old boat had belly tanks storing 75% of the total tankage. It had two
wing tanks of 40 gallons each. The fuel tanks all had sediment traps and
the fuel piping had three stages of filtering. This included a dual filter
setup with a single lever to change over elements that looked ever so much
more elegant than anyting I have seen RACOR offer. There was also a filter
located between the lift pump and the injection pump. ALL of the above was
made of bronze. The port engine was fittted with a PTO driving a hydrualic
pump that powered the anchor winch. That winch was powerful enough to draw
down the bow rail to the waterline. I heard about this experiment from an
eyewitness. Ther was space for storing two large anchors forward. Ther was
also a smal ldavit for lifting the 100 lb anchor.
The vessel was essentially all DC lighting and had a DC genset on board. In
those dayss a 40 amp 12V charging plant was considered sifficient. The 9
foot tender was equipped with a centrally mounted INBOARD engine ( Stuart
Turner) complete with bronze seacock and water cooling plus forweard and
reverse gear. The seacock was fitted with a bypass so it could pump out th e
bilge via the engine cooling water pump. Yuo could hand crank it or use an
emergency rop pul lstart. The tender was carried on top of the coach roof
and lowered over the side in davits mounted on the starboard side.
Originally the vessel was also fitted with a midships accomodation later for
the owner to board or depart from the vessel int o the tender via this
accomodation latdder. The paid crew had their quarters forr'ard with its
own acces ladder to the deck. The vessel did have hot running water in the
galley using a gravity fed Instahot propane fired boiler.
Sounds pretty much like a very nice modern trawler, ezxcept this boat was
designed around 1934 and commissioned in 1936.
I'm amazed at the ingenuity displayed by those designers of yore.
Arild
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