New design plan questions

Discussion in 'Boat Design' started by Newickspark, Jun 14, 2019.

  1. Newickspark

    Newickspark Previous Member

    See 44 seconds.... that’s how they stack,
    And see the tree orientation....
    I would have to add a lip to keep the straps from sliding down. That could be small, on the forward edge of the mast and back edge of the two tubes aft.

    Maybe it’s just me, but I think this idea for this boat is incredible.

    I posted in the multi section, but not much advice or reaction.

    I would have an engineer design two strong tubes and connection to the aft end of the floats. That gives me three “trees” using the main mast for forward connection.

    You could stack two of these that would offer very comfortable sleeping in all but the real nasty stuff, while on the hook.
    These tents are super comfortable, very dry.

    The one I would use is the safari connect, it’s bomb proofed ‘ with grade 4 mesh for the tropic bugs.
    It’s also much stronger material. 5 yr warranty no questions asked

    Attached Files:

    Last edited: Jun 15, 2019
  2. Alik
    Joined: Jul 2003
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    Alik Senior Member

    One can buy the 'plans' for 200$ and what he gets is the shape and general arrangement drawing. Not event the table of weights to follow during construction ;)
  3. Newickspark

    Newickspark Previous Member

    Not sure that’s true with the spark plans, see above. There are 6 Mylar pages

    Two full
  4. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    I dont think Duracore is even sold anymore.
    Carbon - gain a lot of cost in materials, not gain any weight loss unless you hire an engineer, gain a lot of cost in an engineer.
  5. Newickspark

    Newickspark Previous Member


    No weight savings? Dura core core with
    Glass’ vs Corecell and weight savings?

    Roll of 6k
    2000 USD

    Not really a big expense, if your worried about the cost of the cloth, you Probably shouldn’t be building a 28’ tri

    You could find a 2nd year, collage marine engineering student to do the conversation from dura core and glass To core cell and carbon.

    Just need to determine the loads on each point
    Of the tri, once you have that, change the lamination schedule to be lighter, exceeding the original design
    Load requirements, while keeping the lamination equal in size to the original plans.

    Not an engineer, but to me it’s pretty easy numbers..
    Will the carbon/Corecell in the same lamination size be Stronger Stiffer Lighter then the dura core/glass. I’d be willing to bet yes.

    Last edited: Jun 16, 2019
  6. HJS
    Joined: Nov 2008
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    Location: 59 45 51 N 019 02 15 E

    HJS Member

    Development of the Ljungström rig
    The following is based on my own many years of experience with the Ljungström rig.
    For the sail to have an effective area even when it is partially rolled up, the circumference of the mast should be approximately equal to at the top as at the root. To achieve this, the mast must be wing-shaped at the top. See attached illustration.
    To get more sailing area at a given mast height, the sail can be provided with vertikal battens. This also helps to control the shape of the sail.
    On my own boats, the sail has not been double. However, it has a spacious pocket at the front to avoid interference from the mast and create a favorable profile.
    The mast must be dimensioned so that it bends as desired at load. The dimensions is based on experience from other boats with free standing masts, such as the Finn dinghy.
    In order to be able to control the twist and camber, the rig must be equipped with some form of boom. Based on the experiences I have made, I suggest today a Hoytbom.


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    Last edited: Jun 16, 2019
    Manfred.pech likes this.
  7. upchurchmr
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    upchurchmr Senior Member

    You need someone better than the second year engineering student that I was.
    It is easy to just substitute carbon for glass in the same thickness, but to get the long term strength right you need real numbers and analysis.
    I'm talking carbon/ corecell vs glass/corecell.

    It's easy enough to overbuild in Carbon to get safety, but that kills the weight savings and increases cost. Of course, hand layed/ vacumn bagged will typically weight more than infusion, and have less strength.

    Good luck.
  8. Newickspark

    Newickspark Previous Member

    Thanks for posting, the info is useful.

    Wondering, could you Redesign the jib tube in carbon, so that tube splits into two, then comes back together and attaches flush, For use on the split sail design.

    When together, sails as a normal boom
    Then split the boom tube, and swing out for spit sail downwind.

    If you want to get really forward thinking, you could then add one forward facing also
    This would give you so many sail options...
    Head and jib
    Head and mizz
    Head split and jib
    Head split with mizz
    Stay sail between mizz and headsail
    Ect ect
    might be too much, but sure would create a lot of sail options to play with!

    That would be some kind of trick!

    Hoyt jib boom

    Attached Files:

    Last edited: Jun 16, 2019
  9. HJS
    Joined: Nov 2008
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    HJS Member

    Follow the KISS rule
    Keep It Simple Stupid, Dick Newick

  10. Newickspark

    Newickspark Previous Member

    Yes, solid advice. I like thinking out load,
    But to be honest, it’s probably going to be the rig as designed, with whisker poles for butterfly mode!

    I do like the idea of the whisker poles somehow doubling as a boom.

  11. luckystrike
    Joined: Feb 2010
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    luckystrike Power Kraut

    the full scale mylar sheets will be the templates for the Stations of the moulds.

    have fun, Michel
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