[PCW] Fuel Economy, was Fountaine Pajot Cumberland 44 & Cat A rating

[Alexander Veis]

Dear Gary
My one year power cat is a Fountaine -Pajot  Highland 35 (I suppose that is
a boat with the same concept with your PDQ 34) and either with the Volvo D2
75hp or with the optional volvo D3 110hp has a range 900-1000 miles at
7knots. My flow scan shows 0.9lit/mile at this speed. However at 15kn the
consumptios is about 1.5 lit/mile and 2 lit/mile at the top speed of 19kn.
As you see still you can find some producers that offer low consumpion power
cats
Alexander
----- Original Message ----- 
From: "Candy Chapman and Gary Bell" <tulgey at earthlink.net>
To: "Power Catamaran List" <power-catamaran at lists.samurai.com>
Sent: Tuesday, January 08, 2008 6:55 PM
Subject: [PCW] Fuel Economy, was Fountaine Pajot Cumberland 44 & Cat A
rating


> I don't intend to spike the conversations about the Cumberland engine
choices,
> nor of the presence or lack of quality boat makers, please carry on.  I
note,
> that the Cat. A rating part of the original posting got little comment, as
the
> discussion moved into F. P. construction quality.
>
> I would like to add a thread about the seeming lack of low powered
'trawler
> style' power catamarans, rather like my beloved early model PDQ 34 (hull
12 of
> 114 sold).  In these times of perpetually rising fuel costs why can't the
> marketplace provide any fuel efficient (and slower, with economical
motors)
> models that capitalize on the real future of boating for the many of us
who
> face rising fuel costs with fixed or even reduced retirement incomes?
Will
> any of the makers recognize what I see as a clear need for Prius like
> performance, rather than the headlong rush to make only larger, faster and
> more powerful SUV's, Hummers and Maseratis?  I don't see much in the mass
> production of slender hulled power catamarans with smaller fuel efficient
> engines anymore (with L/B ratios for the individual hulls in the 10 or 12
to
> one range, and ondeck beam about half the length, like virtually all
sailing
> cats, which are after all optimized for just the speeds I'm talking about
> here).  I know, there are several larger efficient power catamarans made
on a
> custom basis, but I'm thinking of the mass production boats available to
the
> more modestly funded buyer.  Rather the other major sort of mass produced
> power catamaran which dominates the market today is the high powered, high
> speed boats with distinctly planing hulls, with only a small tunnel like
> passage between hulls, and performance more akin to the fast 'express'
boats
> and without the ability to emulate the long range trawler style cruiser,
or
> the well discussed motorsailer.  Will the manufacturers abandon my sort of
> boater leaving us to move into sailing catamarans?
>
> The very first PDQ hulls had Westerbeke motors in the 50 hp range
somewhere,
> and the factory had some serious difficulties with those installations, so
> they switched to the Yanmar 4JH3 55 hp normal aspiration engines.  By the
time
> my hull was built, they were offering the 55 as standard, with the
> turbocharged 75 hp as an option -- which I chose.  Within a couple of
years
> the 75 became standard and the 100 hp intercooled turbo model the
recommended
> option.  Interestingly, they claimed that the 100hp installations got
better
> fuel economy as well as pushing the top speed up a couple of knots from 19
for
> the 75hp to 20kts for the 100hp.
>
> Based on factory data, only anecdotally supported by my own experiences
> (limited to measuring distances and guessing average speeds between
fill-ups),
> I seem to be getting 4 gal. per hour at 15 to 17 kts, which works out to
> roughly 4 miles per gallon (given reasonably flat water, of course).  At
least
> one of our loyal listees has published detailed and extensive fuel economy
> data with the 100hp model.  I won't quote his figures (in part because I'm
too
> lazy to look them up!) but I will tell about my own 75 hp experience:  I
get
> the published WOT top speed of 19 kts in nice flat water (noted in an
article
> on my boat in Pacific Yachting), and a couple of times I've kissed 22 kts
> (downhill with a significant tailwind).  Our slender hulls don't have a
> 'planing step' speed that you can sense, the transition past our wave trap
> hull speed of 7.8 kts seems smooth and continuous.  I suspect that a peak
in
> fuel economy could be found if one took highly detailed fuel economy data
at
> such speeds, but is probably masked by the similarity between displacement
and
> planing behavior because it happens at down about 1/3 throttle, where
there is
> abundant power available, and because most of us don't spend much time
> cruising there (for now).  But, "the times they are a changin'."
>
> I don't have fuel consumption instrumentation (flow meters), but I think
at
> least one or two other PDQ 34 owners do, and so I guess my next question
is:
> could one of you do a little reporting on the fuel consumption,
particularly
> regarding what I suspect will be a peak of fuel mileage at just below hull
> speed?  Are there any other makers or designers of power catamarans who
have,
> or could gracefully produce fuel economy data, with an eye toward nice
long
> ranges at reasonably low fuel cost?  I further suppose that significant
> changes in props would also provide gains in fuel economy -- namely
putting
> engine peak performance at a lower speed to promote greater range/fuel
> economy, although that might effectively trim the higher speeds.  Or, how
> about variable pitch props?  I suppose I should add flow meters and
variable
> pitch props to my wish list, put a little of my own money where my mouth
> is...
>
> Well, that ought to stir up a comment or two...
>
> Regards,
> Gary Bell
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