[PCW] Fuel economy, Chrysalis across the Atlantic

[Candy Chapman and Gary Bell]

Ocean passage of 1,800 nautical miles:

>>		Chrysalis        Bluewater       Seahorse
>>
>>Average speed    8.3 knots       6.2 knots           7.3 knots
>>
>>Fuel consumption    4.0 gph     4.4 gph            3.24  gph
>>
>>Time underway    9 days        12  days                10 days
>>
>>Fuel burned    865 gal       1,275 gal                  757 gal.
>>
>>Seahorse is a 1978  Skookum 53 motorboat with a Lugger 130HP engine. She is
>>built on a sailing hull  and equipped with paravanes, one of which was in use
>>for 4 days and both for three more.
>  
>

Thanks, John, for adding to the knowledge base with real-world 
numbers. The Skookum obviously is a very slippery monohull. It's also 
somewhat smaller.

But your numbers do point out that, for trans-oceanic passagemaking, 
power catamarans don't offer as huge an advantage in performance as 
many people would expect. Power cats do of course have other 
compelling features, such as space, comfort, stability, shallow 
draft, etc.


Very interesting indeed Georgs.  Would an ocean crossing power catamaran 
smaller than 50 feet long still have all those advantages like space, 
comfort, etc.?  I still stand my my rather offhand previous statement 
that the ocean passagemaking power catamaran is presently limited to the 
larger boats in the greater than fifty foot lengths, and most 
significantly with six figure prices.  

The smaller power catamaran will be limited to coastal cruising until 
somebody comes up with a revolutionary improvement so that the smaller 
hull can hold enough fuel for long passages.  Slipping over to Fantasy 
Land here for a moment, I note that fighter jets carry drop tanks which 
carry considerable amounts of extra fuel held outside the 
airframe/hull.  I don't want to trust in towing a fuel barge that could 
be lost in bumpy weather, but how about a semi-submerged, or fully 
submerged tank, rigidly slung between the hulls, or alternatively a pair 
of such tanks firmly affixed to the bottom of each hull.  It/they could 
be a good deal longer than the boat if desired, and fitted with 
adjustable trimming floatation and/or water ballast.  One could perhaps 
drop the tank when arriving in a coastal cruising destination.  It might 
look rather like a modern submarine, or perhaps a torpedo, or like the 
hull of a beach cat (think Hobie), or even like the hull form of the 
host power catamaran...  A temporary trimaran if you like....

Of course there are a lot of other design choices present in 
contemporary power catamarans that seem to me to limit them to nearshore 
work.  They have features that would likely not fare well over the long 
term in deep water storms.  Features like large windows; lengths and 
beams that seem easier to capsize in large waves; hull strengths perhaps 
inadequate for the long open water passages; or high speed hulls with 
large thirsty engines. 

Could a contemporary power catamaran design be modified to carry 
sufficient fuel and have the features needed?  If so, would anybody in 
their right minds build and try to market it?
I also stand by my previous suggestion of modifying the fuel tankeage 
etc. of a suitable under fifty foot sail catamaran to gain the range 
needed.  I know, it's not a power catamaran anymore, but I don't see a 
non-sailing catamaran design under fifty feet long that would give me 
the confidence for ocean crossing bluewater cruising.

Kite sails?  Have any of our listees actually seen one of these?  I 
haven't noted much activity their web pages seem to me to still be 
showing the same images I noted several years ago. 

Cheers,
Gary Bell