Dave Gerr H.M. Pope iii

Discussion in 'Boat Design' started by fpjeepy05, Feb 27, 2010.

  1. fpjeepy05
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    fpjeepy05 Senior Member

    I'm interested if anyone has attempted to make this boat. I figure with today's materials, Lightweight diesels, and surfacing drives it might be possible to make a very fuel efficient vessel. Why isn't anyone doing this? What is everyones fascination with outboards?

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  2. Ike
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    Ike Senior Member

    You obviously haven't read the last few issue of PwoodenBoat Magazine. Look at December 2009 for a start. In fact that is pretty much what everyone is working on now. Fuel efficient boats.
     
  3. tom28571
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    tom28571 Senior Member

    Not sure how a comment on outboards got tied in with a post on the 1600hp H.M. Pope. There have been a couple ridiculous example of stacking monster outboards across the stern. Pope may be an efficient boat in some regard but it is certainly not an efficient hauler of two people.

    As Ike said, there is an increasing interest in fuel efficient boats. Its not apparent by looking at the usual crop of motorboat magazines but we have our niche.
     
  4. mark775

    mark775 Guest

    "it is certainly not an efficient hauler of two people." - Why do you say that?
     
  5. Hunter25
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    Hunter25 Senior Member

    Call Dave Gerr.
     
  6. fpjeepy05
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    fpjeepy05 Senior Member

    I didn't know I was an inferior human for not reading the December issue of PwoodenBoat Magazine. Sorry if I insulted you. I also find it ironic that such a topic would be discussed in a Wood boat building Magazine. Guess I'll have to read it.
     
  7. mark775

    mark775 Guest

    I would have liked to see the thread go somewhere, as well. A perfectly reasonable question - the only answer to which, I have to assume, is that most people forgot such great designs exist. Somewhere in Gerr's writings, I recall, he addressed the Merlin diesels and suggested that he drew them in "as an example". A couple of Yanmars would go well there, tho I am predisposed towards single engine designs. If I were building a comfortable commuter for an area of light chop, I can think of few boats better, nor more efficient - given the constraints of comfort and semi-protected waters.
    Outboards are good these days but not for everybody or every boat. I'm with you gravitating towards inboard designs.
     
  8. TollyWally
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    TollyWally Senior Member

    I think Gerr was using the Merlin motors as an example because he could get good power to weight out of them. Quoting directly from his book, pg 177, The Nature Of Boats, he states (Pope)achieving a fantastic .21/hp/kt, (Pope's)1600 horsepower gives her 12.2 lb/hp and 12.2/hp divided by 58 knots(estimated top speed)= .21/hp/knot.

    FWIW burning 80 gallons of diesel an hour may be efficient but for me it is not economical! :)


    Oh Lord, give me one more boom. I promise not to piss it away this time. A little bit of philosophy I remember scribbled in a bathroom in Kodiak in the 80's.
     
  9. Hunter25
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    Hunter25 Senior Member

    Considering her size and speed, this is nicely efficient, even if out of our class or reality. I have a friend that crosses to the med each year. He does not have any problem with the 15k fuel bill.
     
  10. TollyWally
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    TollyWally Senior Member

    Flat out that baby's burning through $250.00/hr of oil. 15 g's gets you 60 hours. Nice boat, it'd be nice to be able to afford to run it, let alone build it. I guess I need to crank up the ambition a little bit.
     
  11. fpjeepy05
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    fpjeepy05 Senior Member

    Agreed

    I agreed a pair of 480hp Yanmars, some Bmax or Imco Sterndrives, Cored hull and keeping everything lightweight. I could easily see a 65 mph boat. 50 mph Cruise. 25 gph. 2 mpg. Now thats pretty sweet.
     
  12. tom28571
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    tom28571 Senior Member

    Maybe, but it is also just speculation.
     
  13. marshmat
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    marshmat Senior Member

    I take issue with the reference to the ratio (weight/power)/speed as a measure of efficiency, as mentioned in that chapter of "The Nature of Boats". Note that if you increase the weight, or decrease the power, the ratio as described in that book goes in the opposite direction to what would actually happen to the efficiency (increased weight in this formula results in increased ratio, ie. less efficient, when more weight at the same speed and power should mean more efficient). Power / (weight * speed) would seem to be the proper comparison.

    Having said that, the H.M. Pope is still an extremely efficient hull for what she does. Not within the financial realities of most of us, but very hard to beat for moving a lot of stuff really quickly.
     
  14. TollyWally
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    TollyWally Senior Member

    I've noticed that anomaly but hesitated to bring it up at this point in the conversation.

    "Power / (weight * speed) would seem to be the proper comparison."

    This makes sense to me. Another thing that I wonder about, I don't know if anyone else has the book handy as I do but the exhaust appears to exit the bottom of the hull just forward of the transverse step. I've puzzled over that, I'd think it would be better in the vacuum hole aft of the step if I am at all understanding the theory.
     

  15. marshmat
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    marshmat Senior Member

    It looks to me like the exhaust duct on H.M. Pope III is routed to a plenum chamber that exhausts out the step, as would be logical; however, I don't have a sufficiently complete set of drawings to say for sure.

    Again, I do think one would be hard-pressed to come up with a more efficient way to make nine tonnes go 58 knots on the water.

    Our OP's question was:
    To the first part, I answer: Because few of us want to, need to, or can afford to propel nine tonnes at 58 knots. There are some circles, though (oil rig supply, pilot boats, uber-weathy fishing nuts) where such a boat would be ideal, and where designs such as H.M. Pope III are highly sought after.

    To the second part, I answer: Under about 150 hp or so, the modern outboard engine is really, really hard to beat for total cost of ownership on most small craft. They are cheap to buy, cheap to run, and relatively straightforward to repair for the first 15 years or so (until the spare parts are discontinued in favour of newer models).

    Obviously, they're not for all applications- relatively heavy, slow boats don't tend to fare as well under O/B power as do lighter, faster ones. And above about 150 hp, sterndrives become seriously cost-competitive. Above 300 hp, there are no O/B options unless you go to twins/triples, at which point the fuel savings of an inboard or sterndrive diesel are starting to translate into seriously improved range and cost-per-mile.
     
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