Hickman Sea Sled Information

Discussion in 'Boat Design' started by DogCavalry, Feb 12, 2021.

  1. DogCavalry
    Joined: Sep 2019
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    DogCavalry Senior Member

    IMG_20240529_101854457.jpg

    Some real world data of the only sea sled I can work with.

    The boat is 26'*10', or 7.9*3m. Weight is roughly 5500#, or 2500kg. Power is a 2014 Evinrude Etec 250HO. X-axis is RPM at the crank. Reduction is 1.85, turning a 16"*17" SS prop with moderate cup. Y axis shows speed in knots, one per square as noted, and for the red curve, fuel consumption in liters per km traveled. To convert to gallons burned per mile traveled multiply by 0.428. This gives the worst mileage at 8.5 knots, of 0.54 gallons burned per mile, or the inverse 1.87 miles per gallon.

    Tests were done on a calm, rainy day at North Vancouver, BC.
     
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  2. DogCavalry
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    DogCavalry Senior Member

    @Steve W , we need that article.
     
  3. Steve W
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    Steve W Senior Member


    So, that article i mentioned can be found by googling "sea sled, a real corker" it is on spoonercentral.com. Sorry, i don't know how to link things.
    I have a few questions for those members who have actual experience with using this hull form.
    1/ Sneezing, how much does this happen and does a sneeze guard solve it.

    2/ Most of the small sleds were powered by a single outboard. It seems to me that if you followed the recommendations from the outboard manufacturers of placing the anti cavitation plate 1" below the transom the prop would be operating in very aerated water which does not seem right. I wonder at what depth they settled on, on the original boats. Maybe i'm overthinking this as all boats have disturbed water coming out from under the transom but most are some sort of Vee so the prop is deeper by default so in cleaner water. The reason why the leg is typically just an inch down is to reduce drag.
     
  4. Steve W
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    Steve W Senior Member

    Ok, if you google "sea sled baby orlo" you will find the beautifully restored baby Orlo, if you scroll to the bottom of the page and click on new old sea sled stuff you will find a few more photos, one shows a small sled on the ways and it does show the motor to be deeper than normal for a vee bottom boat. The last photo is the one with a guy and a large dog in the boat and towing 3 people on some kind of sleds, (not water skis). Look at the physical size of the motor, it is not large by today's standards and it has a built in tank. It looks about the size of the one on the ways, i wonder what horsepower it is. It's impressive.
     
  5. DogCavalry
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    DogCavalry Senior Member

    @Steve W , sneazing is infrequent on my sled. I mostly don't care about it. Aerated water however has been a huge issue. Enough so that I wish I'd bought a pair of smaller engines rather than the one bigger engine.
     
  6. Steve W
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    Steve W Senior Member

    It seems to me that all the small ones had a single outboard on center but it does look like they were deeper in the water if you look at the photo of the boat on the ways. The Knapps built a lot of the 13ft models so it must have worked pretty well. Regardless, the deeper you go, the more drag on the leg you have to the detriment of performance.
     
  7. C. Dog
    Joined: May 2022
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    Location: Coffs Harbour NSW Australia

    C. Dog Senior Member

    Did not Hickman invent a surfacing propeller because of this issue? Maybe if one had the time and resources the outboard could be raised (watch cooling water inlet) and experiment with propping to maximise performance. I would suggest that if a surface drive propeller fixes it then an inboard engine (or motor) might be a better option. Keel cooling can be investigated then.
     
  8. DogCavalry
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    DogCavalry Senior Member

    Actually Hickman patented the surface piercing prop a few years before he patented the hull. He patented the non tripping chine some years later.
     
  9. C. Dog
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    Location: Coffs Harbour NSW Australia

    C. Dog Senior Member

    If I got the link right, this boat has the outboard mounted about 100mm lower than normal, it also has a lot more prop diameter than a contemporary outboard of similar hp.
    https://spoonercentral.com/2006/1931.jpg
     
  10. DogCavalry
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    DogCavalry Senior Member

    My prop is 5" lower than normal, and the largest diameter I could fit on the OB. Maybe ⅛" space between the blade tip and the AV plate.
     
  11. Steve W
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    Steve W Senior Member

    I was aware of the surface piecing prop on the larger, inboard Sleds but i don't see them as practical for my application as a tender to a sailboat where it will be beached regularly. Clearly outboards must work as all the smaller Hickman sleds used them. It seems to me that i would need to use a long shaft motor and live with the extra leg drag. I find the use of surface piecing props a bit puzzling really as you would have only half the blade (even though it would be larger) operating in aerated water. Modern ones like Arneson can be trimmed up and down but in some of the Hickman photos i have seen they are fixed. I would like to get a measurement from the top of the transom to the center of the prop of an original 13ft Hickman sled as the Knapps apparently built over a thousand of the things so they must have got it figured out.
     
  12. C. Dog
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    C. Dog Senior Member

    Steve it is not the extra drag that will punish you if beaching regularly it is the extra draught.
     
  13. BlueBell
    Joined: May 2017
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    BlueBell . . . _ _ _ . . . _ _ _

    Yes, and an electric Jack Plate, anecdotally.

    OR

    An Arneson style drive might be best, but not the cheapest.

    EDIT: Steve I wonder if you should move these posts to a new thread about your build. If you reread John's first post here you'll see it's meant as a repository for Sea Sled info. Cheers
     
  14. Steve W
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    Steve W Senior Member

    C.Dog,
    When you come in to the beach with any tender you tilt the motor up before you hit the beach so the draft is not an issue.
     

  15. Steve W
    Joined: Jul 2004
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    Steve W Senior Member

    BB, I agree, i will start a new thread. Re the Arneson drive. I'm planning on a 10ft length, which is typical for a RIB style tender for a bigger boat, an outboard is about the only propulsion that makes sense on this size boat.
     
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