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Old 12-12-2013, 01:51 PM   #121
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...60 HP from a 150-300 P engine is not efficient , even with a modern electronic injection engine.

Using a Cummins 6BT5.9-M as an example, at full rated power of 210HP its BSFC (pounds of fuel burned to produce one hp for one hour) is 0.397.

At a moderate output of 120HP it will burn the same amount to produce one horsepower ... 0.397 pounds.

If you pull the throttle back to 60HP, that engine will burn 0.385 pounds of fuel to produce each horsepower.

It is more fuel efficient at 60HP than at its rated maximum power output and a moderate "cruising" power.

While that particular BSFC relationship may not apply to every engine, in every installation, it shows very clearly that the statement you keep making about "low efficiency" at less than some arbitrary high power output is incorrect. It is misleading, and it is based on docktalk and rumor.
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Old 12-12-2013, 01:55 PM   #122
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Here is a Passagemaker mag boat review (nice pics also of quality built interior):

http://www.journeycatamarans.com/wp-...JourneyCat.pdf


....excerpt...
THE TEST
Underway, the twin 220hp
Cummins QSD diesels turning 20
x 20 x 4 props through Seatorque
drive shafts produced a smooth and
quiet ride at the lower helm. New
21 x 19 x 5 Michigan Wheel M500
series props are planned for hull
number one, adding about 30 percent
more surface area and an anticipated
increase in economy and performance.

Beginning with hull number two,

standard 260hp Yanmar 6BY diesels
spinning 24-inch diameter props will
be standard propulsion, adding 40
more horsepower and blade area, and
reducing weight by 100 lb. per engine


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Old 12-12-2013, 02:14 PM   #123
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Quote:
Originally Posted by RickB View Post
Using a Cummins 6BT5.9-M as an example, at full rated power of 210HP its BSFC (pounds of fuel burned to produce one hp for one hour) is 0.397.

At a moderate output of 120HP it will burn the same amount to produce one horsepower ... 0.397 pounds.

If you pull the throttle back to 60HP, that engine will burn 0.385 pounds of fuel to produce each horsepower.

It is more fuel efficient at 60HP than at its rated maximum power output and a moderate "cruising" power.

While that particular BSFC relationship may not apply to every engine, in every installation, it shows very clearly that the statement you keep making about "low efficiency" at less than some arbitrary high power output is incorrect. It is misleading, and it is based on docktalk and rumor.
So you are saying that if you pull back the throttle and cut the RPM's of the engine significantly, you will save almost no fuel??

Just the greatly reduced volumetric intake would seem to counter this??
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Old 12-12-2013, 02:23 PM   #124
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No. There is a big difference between BSFC and fuel consumption. BSFC is how much fuel an engine burns to produce one horsepower for one hour. Fuel consumption is how much the engine burns in one hour.

Most engines are have the lowest BSFC at some power level other than the lowest or the highest, that range is where they are most efficient at converting fuel to power. That doesn't necessarily mean that the system in which they are installed is most efficient at that point however.
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Old 12-12-2013, 05:57 PM   #125
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Rock is right. The fuel/Hp curve on modern diesels is a shallow curve with the most efficient RPMs towards the center - the least efficient at the ends both high and low.

If one is designing a boat where maximum efficiency is an important goal, then engine choice would take into consideration using the RPMs at cruise where the motor is delivering the maximum HP per unit of fuel. Since this part of the curve is towards the center, then there would always be plenty of HP in reserve.
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Old 12-12-2013, 09:56 PM   #126
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...but we are talking 'efficiency' here , not lowest fuel consumption ....correct?
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Old 12-13-2013, 01:42 AM   #127
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Deltaville, VA June '13. First boat I saw after tossing the lines headed solo for Maine Sorry the pics are grainy but it was about 5 am I think.
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Old 12-13-2013, 01:58 AM   #128
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Deltaville, VA June '13. First boat I saw after tossing the lines headed solo for Maine Sorry the pics are grainy but it was about 5 am I think.
Nacelle appears to be shocking overkill.
I have delivered similar sized powercats before without anything even remotely like that.

I also have my worries about the bluff wall of metal at the front, especially if you were to encounter seas that required such a large nacelle
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Old 12-13-2013, 02:47 AM   #129
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Deltaville, VA June '13. First boat I saw after tossing the lines headed solo for Maine
I was curious. It has a site: FAQs About the Boat

Said to be a 12 Knot Crowther built by AF Theriault. Interesting url, BigDumBoat.
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Old 12-13-2013, 02:49 AM   #130
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The Coot is the antithesis of all of this. Fat, heavy, and plowing the water, burning 2-minus gallons an hour going six knots using a fraction of its 80 horsepower.

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Old 12-13-2013, 06:25 AM   #131
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...but we are talking 'efficiency' here , not lowest fuel consumption ....correct?
Correct? Who knows?

What kind of efficiency are you talking about?

Fuel efficiency?
Transport efficiency?
Engine efficiency?
Propulsion efficiency?

You guys appear to be trying to measure some undefined parameter without a real gauge or even a common vocabulary.

I'm waiting for someone to come up with an equation to describe how much elbow room each angel has when dancing on the head of a pin. That would probably have more practical application.
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Old 12-13-2013, 06:52 AM   #132
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Greetings,
Mr. Rick B. Here ya go....
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Old 12-13-2013, 11:27 AM   #133
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Originally Posted by Daddyo View Post
Deltaville, VA June '13. First boat I saw after tossing the lines headed solo for Maine Sorry the pics are grainy but it was about 5 am I think.
Looks more like in the tradition of Pacific Expedition or Trawlercat Marine designs, both below. Huge hulls. My interest in cats are more along these industrial styles, even though I don't consider them attractive. I too, am puzzled about the bluff bow.

Photo 1, Pacific Expedition, Photo 2, Trawlercat Marine
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Old 12-13-2013, 09:11 PM   #134
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Deltaville, VA June '13. First boat I saw after tossing the lines headed solo for Maine Sorry the pics are grainy but it was about 5 am I think.
http://www.trawlerforum.com/forums/showpost.php?p=198529&postcount=127

Butte ugly as well
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Old 12-13-2013, 09:43 PM   #135
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I hoped Healhustlers pics in #133 above were photoshopped, seems they are not. Maybe something was cut down the midline and a beam extension inserted in-between. Why do some cat designers use a school bus as their inspiration?
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Old 12-13-2013, 11:40 PM   #136
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Looks more like in the tradition of Pacific Expedition or Trawlercat Marine designs, both below. Huge hulls. My interest in cats are more along these industrial styles, even though I don't consider them attractive. I too, am puzzled about the bluff bow.

Photo 1, Pacific Expedition, Photo 2, Trawlercat Marine
Pretty sure I read in the blurb once that they to are a crowther, all I can say is I hope it was Brett and not the legend, his father Loch who penned it.
And if it was Brett, that would go a way's to explaining why there is no Crowther designs anymore.

Heres something similar in steel


Steel Workcat 55' “Stay Calm” | Commercial vessels | Boat Sales Tasmania
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Old 12-13-2013, 11:41 PM   #137
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Something?? What the hell is that??
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Old 12-14-2013, 01:42 AM   #138
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Quote:
Originally Posted by healhustler View Post
Looks more like in the tradition of Pacific Expedition or Trawlercat Marine designs, both below. Huge hulls. My interest in cats are more along these industrial styles, even though I don't consider them attractive. I too, am puzzled about the bluff bow.

Photo 1, Pacific Expedition, Photo 2, Trawlercat Marine
That thing looks like it's made out of Lego.
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Old 12-14-2013, 02:27 AM   #139
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Bluff bows, Sharp Shooter is one of 2 (Straight Shooter) that I did a bit of work on.
Both were tuna long liners, Economic, ugly but bloody terrific work platforms and comfortable so less fatigue for the crew working long hours.

Can't recall the builder/designer from down south in NSW but I did approach him re design for a smaller version when I was going thru my cat phase.
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Old 12-14-2013, 07:07 AM   #140
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I find something rather ruggedly beautiful about "Sharp Shooter" pictured above. Then again, I drive an old FJ62 Landcruiser and love the 80-90's Suburban's, so maybe that's it?
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