Sea Sled madness. It’s in my brain.

Discussion in 'Fiberglass and Composite Boat Building' started by DogCavalry, Nov 11, 2019.

  1. DogCavalry
    Joined: Sep 2019
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    Location: Vancouver bc

    DogCavalry I aim to misbehave.

    After more days lofting than I expected, I finished the lines last Saturday. Offsets by Sunday. Built the transom on Monday. Back tonight for the first permanent bulkheads, of which there are 5, and a hefty ring frame, per Dave Gerr’s Elements of Boat Strength.

    I guess the most important part of that is that I have offsets.

    J
     
    bajansailor likes this.
  2. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

    Did you create the lines by lofting full size? If so what will you use the offset for? Can you pick up frame shapes, etc directly from the lofting?
     
  3. DogCavalry
    Joined: Sep 2019
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    DogCavalry I aim to misbehave.

    Bluebell, I only just now noticed that your houseboat is the same size as my sled. Sled-rot in my brain I think.

    I’ll be living aboard when I’m working well away from home. How does the size of your houseboat strike you?
     
  4. DogCavalry
    Joined: Sep 2019
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    Location: Vancouver bc

    DogCavalry I aim to misbehave.

    I did. First I had to insulate, vapour barrier, and surface the walls of the shop. Well, before that I had to clear out 15 years worth of accumulated crap, and heaps of rat invested nesting.
    Then I lofted full size. Yes, I am taking frames directly from the lines. Offsets are for my friends (that means you). And a few very kind folks, who are genuine naval architects unlike my semi-literate self, have generously offered to do some hydrodynamic analysis for me. Once I convert fractional inches to millimetres like a civilized person would use.
     
  5. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    BB and DC, could you perhaps post even a rough general sketch of your houseboat (BB) and your proposed general arrangement on the sea sled (DC)?
    DC, I know that the thread on here about tank testing got quite contentious, but would it be worthwhile building a model of your boat and doing some basic tests with it, or are you pretty confident in your final design now?
     
  6. DogCavalry
    Joined: Sep 2019
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    Location: Vancouver bc

    DogCavalry I aim to misbehave.

    Bajansailor, I’ll post photos of the lines, sections, and my current thinking on layout, before the weekend.

    I’m as confident as I can be, before it hits water (sleepless nights the week of). I can’t afford innovation - I can barely afford to eat these days - so I bought the plans for the TX18 from bateau.com, which included the lines and panel plans for a 1957 Jackson sled sled. The tx18 is a Hickman sled lowered to be a fishing boat for the Texas gulf waters. I took what I could from those. Both are successful boats, built in reasonable numbers.
     
  7. DogCavalry
    Joined: Sep 2019
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    Location: Vancouver bc

    DogCavalry I aim to misbehave.

    Both the TX1I and the HS18 have too little freeboard for me. And some very slight rocker in the last station to transom, mostly in the way the non tripping chine was developed. So I vertically stretched them to increase deadrise in the forward sections, and straightened out those chines. Those boats are meant to be safe despite the wild slaloms a young user might push them through. I can forgo a little trip resistance, for better fuel mileage.
     
  8. DogCavalry
    Joined: Sep 2019
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    DogCavalry I aim to misbehave.

    I also added a vertical extension at the bow,
    Like the bumper on a car. I call that the ram. For pushing against a cliff face in a fjord, while crew mount or dismount their ride.
     
    Last edited: Nov 14, 2019
  9. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

  10. DogCavalry
    Joined: Sep 2019
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    Location: Vancouver bc

    DogCavalry I aim to misbehave.

    You are right about their site. Considering how much effort I went through to give them a hundred bucks, you’d think they’d try to encourage that sort of thing.

    Mostly I wanted to see current thinking on non-tripping chines, and distribution of curvature in the tunnel. For my lines, I was more inspired by the drawings Hickman provided with his 1945 patent application, and sections I got from historical photographs of the boats being built. It was informative though that both sets of lines had the tunnel rising in a straight line from the transom to about station 6, and curving up to the deck from there. But both had the rise under 2 degrees - Far too low for safe deadrise from stations 0 to 4. Slamming and porpoising are bad, and Marcus Lee tells me the only tendency to porpoising was in a boat where the forward sections were too flat. Which is to be expected. Savitsky’s paper clearly lays out the relationship between deadrise and porpoising, although he left it to us to figure out why. Maybe he thought it was too obvious to mention.
     
    Last edited: Nov 14, 2019
  11. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell "Whatever..."

    The size is fine.
    I have a displacement barge 6-tons gross, glass on ply, on 2x6 frames, 24" centres with flat 2x4 stringers.
    9' ceilings and a queen-sized, centre-loft bed above.
    The cabin is 17' x 8 1/2'.
     
  12. DogCavalry
    Joined: Sep 2019
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    Location: Vancouver bc

    DogCavalry I aim to misbehave.

    Great! I need to make 30 knots, so some sacrifices will be made. But still...
     
  13. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

    BlueBell, could you maybe post a few photos of your fine houseboat please?
    Did you design and build her yourself?
     
  14. Mr Efficiency
    Joined: Oct 2010
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    Mr Efficiency Senior Member

    Probably the stagnation line shape
     
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  15. DogCavalry
    Joined: Sep 2019
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    Location: Vancouver bc

    DogCavalry I aim to misbehave.

    Bulkhead 6. At 264”.

    Kind of heavy for 1 guy.
     

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