Step Positioning On Wooded Hydroplane

Discussion in 'Boat Design' started by niska, Sep 17, 2013.

  1. niska
    Joined: Sep 2013
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    Location: Ontario Canada

    niska New Member

    Designing a step hull Hydroplane wood racer

    I'm in the middle of designing a wooden flat hull hydroplane boat with two steps in the hull. if i decide to build this boat it will be be the first time i ever build a boat. Since i'm building it in high school i have the tools i need to build it, The only issue is money and TIME TIME TIME hoping i get it finished before next July. it will 12 ft long and 4 ft wide.i did lots of research of boat building by simply looking at the way they were constructed using the internet and going to boat museums. i came up with the plans myself but have some questions about step positioning. i read elsewhere on this forum that steps should be farther forward so they are just before the center of gravity. but it makes more sense that they are where the wight is, i designed it so the steps are all evenly spaced where the water contact points are, i did this so each step touches the exact same foot print of water as each other while hydroplaning. my inspiration to this design is the the allez IV a race boat currently at the Muskoka boat and heritage center. here is the link to the boat restoration http://www.johnslittleboatshop.ca/kirkracer.html my design is a blocky version with two steps instead of 1. these are only 6 pages of the 13 pages of plans i have
     

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  2. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Placing steps in the ideal locations is very complex and difficult to get right, for the professionals, so a novice has little chance at a reasonable outcome. Without a serious look at Savitsky, the '63 - '64 series USN tests and several other texts on this and related subjects, you'd be best advised to build a scale model, rather then a full size stepped hydro. Some good elementary information is available free in the October/November issue of "Professional BoatBuilder Magazine. Do yourself a big favor and study it carefully.
     
  3. Clyde2001
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    Clyde2001 Junior Member

    Sounds like you have done enough research.
    Go ahead and build a boat!
    We built a number of step hydros back in the 60's. None were designed by "experts" or marine architects..........but they still worked. "Never know until you try!"
     
  4. gonzo
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    gonzo Senior Member

    You can just build the boat and see what she does. Learning from experience is a good thing. However, don't make the usual mistake of novices and expect to get a masterpiece the first try. It will be an experiment, with flaws and strengths.
     
  5. Clyde2001
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    Clyde2001 Junior Member

    You have that right!
    And each one you build will be better than the last.
     
  6. ondarvr
    Joined: Dec 2005
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    ondarvr Senior Member

    While at a Boat Show I was with one of my customers as they were presenting their new stepped hull design to the public (this was when stepped hulls were just becoming "the thing" for pleasure boats). I asked him how they decided where to put the step, he said, "well, it looked good there and it was easy to incorporate it into the mold in that location." I asked if they did any testing and he said they had, but in testing they found that even when done correctly, on this size and style of boat it didn't yield a big gain in performance, it was almost not enough to even mention. So they just put where it looked good and was easy to work into the design.
     
  7. PAR
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    PAR Yacht Designer/Builder

    Steps serve only one useful purpose and complicate a build, so arbitrarily located it is silly, adds to build time and materials. It's not a big marketing feature, so just "winging it" or using the "hunt and peck" method generally is a costly way of doing things, usually with little if any gain.
     
  8. Clyde2001
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    Clyde2001 Junior Member

    You may be right but many boats were built with steps and were quite successful until the advent of the 3 point hydros.

    My point in this whole discussion was that if a kid wants to design and build his own boat, Let Him! Please don't tell a kid that he needs a professional designer or expert before he can build. His boat may not be "optimum" in performance or design, but chances are that it will work and he will enjoy it. And he will learn from it.
     
  9. SamSam
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    SamSam Senior Member

    Would this hull have a tendency in turns to either trip on the vertical sides, or spin out on the flat bottom or both? I had a flatbottom jonboat that would spin out and then trip, which a few strakes cured.
     
  10. SamSam
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    SamSam Senior Member

    Also, what would be a plan to prevent rot? It will be hard to get inside to work on it and those steps and frames will collect water. Treated wood? A removable plank or two the length of the deck to give access?

    I just realized the plan is in inches instead of metrics, are these regular Amurican inches or some sort of Imperial inches? ;) What is used in the UK, inches or metrics?
     
  11. johnhazel
    Joined: Jun 2008
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    johnhazel Senior Member

    Yes! Build it. That's how to have the most fun.

    Also look at this:
    http://www.foils.org/02_Papers dnloads/Clement dynaplane.PDF
     

  12. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    Having lost a buddy of mine a few years back, in a step boat that was professionally designed and built, yet still "swapped ends" at over 60 MPH after "catching a chine" on another racer's wake, it's fairly important to get centers, balance and design features in reasonable locations. In small, often over powered boats, it's pretty easy to stuff a bow, trip or "drive over center" and have the puppy do a 180 at speed. This is fine if you're adventurous and if you get hurt, well, lesson learned, but what if it's your kid or wife that's the one that get hurt or worse. My friend was unlucky and was run over by the prop when he was tossed over the side, as the boat came around. My point is it can happen to anyone, including this racer with of 40 years experience.

    Most of the comments about "the good old days" where "they just winged it" is not entirely accurate. Yeah, the just made it up as they went, but they also used tons of previous model and racing experience, typically taking little step, by little step, developing the evolution of the design. They didn't jump off the turnip truck, design a high speed step hull, place a 1,000 HP engine in it and said, "well, what's the worst that could happen", because they knew what was the worst that could happen. They, like me have lost plenty of friends at speed, in these types of adventures and experiments and had the respect and intelligence, to know to make small, subtle changes to known, sound designs, rather than a big swing at something they didn't fully understand.
     
    Jimboat likes this.
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