Help With Economical Semi-Planing Designs

Discussion in 'Powerboats' started by SAQuestor, Apr 5, 2007.

  1. fcfc
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    fcfc Senior Member

    Yes. The real reason is that this efficiency has NEVER been measured. And never compared in scientific reproductible way.:p

    I just guess most powerboats with the same weigth, same LWL, same BWL, same engine, same propeller, but normal aft form will have at least the same, and probably better efficiency since they have less wetted area. But they will probably have more draft.

    There is no free lunch in box keels.

    There are worldwide numerous model bassin, for over a century, that run daily model tests on every conceivable hull form, including self powered models if that is a problem for your specific hull form. And you have found one, plans available over half a century, that beats all in term of efficiency. :D

    Just look the report I posted above. You will see that some people go to test models of 18 ft lengh, with accuracy checked better than 0.03 inches. Just to win 3.7% of fuel (flaps only). And they would ignore a magical hull form. Be serious.
     
  2. Tad
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    Tad Boat Designer

    What Fc is saying above is correct, their is no "known" efficiency gain coupled to a box keel or Sea Bright form. What is "known" is exactly the opposite.

    Thomas C. Gillmer is a respected NA and he has tank tested several of the Sea Bright hull forms against a series of typical Eastern US fishing vessel types. In his book, A History of Working Watercraft of the Western World (1994), he states "it was most evident that this type of configuration suffered an added drag of approximately 20 to 25 percent over hulls of similar shape but without boxed keel forms." "The survival of Sea Bright skiffs for their fifty years or more is undoubtedly due to other qualities."

    There are a number of reasons for using a "box keel" hull form, transport efficiency is not one of them.

    Tad
     
  3. fcfc
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    fcfc Senior Member

    For production semi displacement "small" boats, you should look also at the nordhavn 35:
    http://www.nordhavn.com/glance/not_production.php4

    Retired from production after two dozen built.

    One of the reason (but I can no longer find where in their site ) is that they were trying to sell a 12 kts cruise boat when the market (customers) where asking for a 18 kts cruise speed.

    I am not aware of "small" (under 40 ft) currently in production displacement or semi displacement hulls with significant market share. Seems all are planning. (or sailboats ...).
     
  4. tom28571
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    tom28571 Senior Member

    Thanks Tad, fcfc

    Everyone seems to be looking for magic but there just ain't none to be had. The most "efficient" monohull powerboat I ever heard about was "Coyote" and its predecessor in Weston Farmers' "From My Old Boatshop". This was designed specifically for highest mpg over its speed range up to about 18mph. Had no superstructure, had a high length/beam ratio and was, according to Farmer, considerably more stable than a round log but it worked best if you parted your hair in the middle. The hull was somewhat like a round hull unballasted sailboat would be.

    Rating efficiency between two boats might well be to compare their pocketbook values, whether we are talking about mpg, cost to build or whatever. Even that makes no sense unless the two boats are doing the same thing with the same accommodation, load, etc. Auto pubs make me gag when they talk about the great fuel efficiency of some car that costs $50K to $70K.
     
  5. SAQuestor
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    SAQuestor Senior Member

    Tanstaafl

    So... If I read all of this correctly it's yet another case of TANSTAAFL.

    Or is there some little thing that I've missed?

    Best,

    Leo
     
  6. FAST FRED
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    FAST FRED Senior Member

    TANSTAAFL.

    Could be, as the main proponent of these boats was the designer Atkin, who claimed sea worthyness , load carrying and good speed with moderate sized motors for the 15 -18 mph range.

    However the Power Keel folks in Austria did make many interesting claims,
    which could only be more advertising hype or ???

    FF
     
  7. fcfc
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    fcfc Senior Member

    From http://www.alsphere.at/alsphere/index.shtml

    "The company was set up in February 2001 to design and market a hull concept for fast displacement vessels. The founders of ALSPHERE came from aluminium yacht building industry and started in the early 1990s to develop a new hull form, the so-called Displacement Glider ("DG"), ..."

    We are in 2007 now. How many boats do use that hull form ? If it had any interest, there would be more by now. Even if it was only for other independant verification of the conceptor claims.
     
  8. Tad
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    Tad Boat Designer

    The Camano 31 and 41 use a box keel hull form which they claim is revolutionary. About 25% of displacement is in the box keel, the remainder of the bottom is very shallow and flat. http://www.camanomarine.com/index.htm

    But the 31' requires a 200 HP Volvo to cruise at 14 knts with a maximum not much higher than that. I think a round bottomed Maine Lobsterboat Hull will do better than that at equal loading.

    Tad
     
  9. FAST FRED
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    FAST FRED Senior Member

    The Shannon 38SRD claims a top of 20.4K and a cruise at 18.5K on 11gph with twin Yanmar 160 hp LH series diesels.

    Sounds quicker than the camano boat.

    Interestingly the designer a Walter Shultz , developed a "unique " underbody " combining sharp forward and deep midsections with inverted V aft sections", Shultz calls this reverse deadrise.

    Kind of sounds like Atkin to me .

    The usual claim "soft riding , fuel efficient , stable , fast with moderate Hp "also sounds like Atkin.

    shannonsrd.com

    They are working on a next model,same claims. 50% improvement in fuel use , smooth stable sea ride.

    The program used for the design was:

    http://www.aerohydro.com/

    FF
     
  10. tom28571
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    tom28571 Senior Member

    Shultz claims a patent on his design. It would be interesting to know just what is patentable in his SRD since I did not see any single feature that has not been used or suggested before. Maybe it's a "Hinkley" style patent:rolleyes:
     
  11. longliner45
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    longliner45 Senior Member

    tad ,,look at the 31 jc hull and you will see it is what your decribing,
     
  12. fcfc
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    fcfc Senior Member

    http://www.motorboating.com/motorboat/seatrials/article/0,12696,553628,00.html
    19.4 kts, 2 * 100 hp. No fancy hull form. Figures independant from builder.

    http://www.classicsolution.nl/frameset.html
    35 kts, 1 * 250 hp. Cruise at 25 kts on 7 gph. No fancy hull form.

    http://www.yacht-design.nl/bosgraaf/designs/motoryachts/hawk41.html
    Yet another one with 1 *250 hp that should be 30+ kts. Still no fancy hull form.

    Where is the efficiency of the Shannon :p I do not even speak of the Camano.
     
  13. fcfc
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    fcfc Senior Member

  14. FAST FRED
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    FAST FRED Senior Member

    .

    The Parker,
    The vessel is light, narrow and easily driven, making her both fast (20 kts) and fuel-efficient.
    POWER
    Shown with twin Yanmar 4JH3-DTE turbo diesels (86hp).

    The weight was given as 10,000lbs

    Couldn't find a speed /power for the others , but there sure NICE looking!


    Seems the main thing they have in common , 10,000lbs or 4.5T is good light weight construction.

    SO far nothing seems to be close to the speed/fuel at 70% of "efficient" as published in PBB.

    The Latitude 46 ,,"Once on plane, I found the boat had a couple of sweet spots on the acceleration curve: one at 1500 rpm (7.3 knots) and another at 3000 rpm (14.3 knots). According to Rodgers, the 40 gets 2 mpg at 15 knots for an approximate range of 264 nautical miles."

    About 2nmpg is where the Shannon is , nothing special.

    FF
     

  15. fcfc
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    fcfc Senior Member

    They mistook Kw and hp. 4jhe DTE is 86 Kw 125 hp ( http://www.barrus.co.uk/pdfs/4jh3-dte.pdf )

    The powering of the Andreyale is in the specs. (beware, the price is old. Seems the current one is double).

    specs of the Van de Stadt design is in the contact menu.

    Yes the key id the weigth.

    18.5 / 11 make 1.7, not 2. And the andryale has NO special hull form.
     
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