Designing a tunnell hulled boat, need help.

Discussion in 'Boat Design' started by willfishforbeer, Nov 25, 2006.

  1. willfishforbeer
    Joined: Jun 2006
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    Location: Florida

    willfishforbeer Junior Member

    What calculations go into putting a tunnel into a small, 16 foot, outboard skiff? Can i do it? Can you tell me how to do it? Thanks.
     
  2. im412
    Joined: Jan 2005
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    Location: australia

    im412 Junior Member

    one of our local builders, as the story goes
    puts an empty acetylene bottle in his mould, when needed, to form a tunnel option in his range

    will be interesting the hear the NA correct numbers on it
     
  3. willfishforbeer
    Joined: Jun 2006
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    Location: Florida

    willfishforbeer Junior Member

    Hah wow thats great. But im talking a serious tunnel, that has been designed for maximum (or close to it) shallow water efficiency.
     
  4. Pericles
    Joined: Sep 2006
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    Location: Heights of High Wycombe, not far from River Thames

    Pericles Senior Member

  5. Chris Ostlind

    Chris Ostlind Previous Member

    When you say tunnel hull, FishforBeer, to what, exactly, are you referring?

    Do you mean like a tunnel from bow to stern. Do you mean a tapered tunnel. Do you mean a partial aft surface tunnel.... What?

    You also mention absolute shallow water operation.

    My experience with boats like this is that you will not get an absolutely shallow water hull if you start taking away parts of the hull that you need for buoyancy. As you remove material to get your tunnel, you also make the hull sink deeper to make up for the lost buoyancy. It ends up being a losing game in the end.

    Here's a piece on a particular design and methodolgy that I agree with in total. http://www.bateau.com/studyplans/XF20_study.htm Jacques Mertens is an excellent designer and has thought this through very nicely.

    With this design you get the shallow water operation you seek without giving the draft right back again through deeper displacement requirements.

    Chris
     

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  6. lewisboats
    Joined: Oct 2002
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    lewisboats Obsessed Member

    I did up a sketch (sorta) in the shallow water tunnel venu...what I did to replace the lost bouyancy was add motor pods to the transom, on either side of the motor. This should help support the weight of the motor. I did this a while ago, but it seems to fit the thread like a glove.

    Steve
     

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  7. Chris Ostlind

    Chris Ostlind Previous Member

    Good Looking

    That's a nice looking ride, Steve. That baby has come along nicely since I saw it last. Way to stay with it.

    I got into this design idiom when I had a query from a customer who asked about my Swamper design and started telling me how he'd like to see a 16' design if he had some input. He suggested the XF20 boat by Mertens and I drew-up an adaptation of that model at the shorter length.

    I really liked Merten's take on the whole tunnel approach for thin water use and did-up a compact tunnel design that would be easy to build and provide the necessary effect.

    My friend wanted to go into very close quarters environments with very thin water, so I pointed him to the 16' design to make life a whole lot easier. And so, like any other boat that fits in the vast hodge-podge of flats/tunnel/cat designs, this one is a sliding scale of design compromises to get to the end result as directed by my customer. I call it Blackwater

    Chris
     

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  8. lewisboats
    Joined: Oct 2002
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    Location: Iowa

    lewisboats Obsessed Member

    Thanks for the kind words Chris...I'm still jealous of your great renderings, I wish I could show off my stuff like that.

    Steve
     
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