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Thread: Cosmo 16-5 - a grown-up one sheet design

  1. #1
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    Default Cosmo 16-5 - a grown-up one sheet design

    I received some positive replies when I presented this one sheet boat some time ago: http://forum.woodenboat.com/showthre...und&highlight=

    Encouraged by the reception I toyed with the idea to scale the design to a more usable size which resulted in this design:




    Further tinkering led to the final design. Once again my emphasis is placed on maximizing the plywood sheets used for the hull.

    The panels for the hull and the panels for the interior structure are tightly nested on 5 sheets of 8 mm plywood. It is definitely a cramped layout but if you are in favor of low-waste utilization of your material you may find some beauty in it.

    Cosmo 16-5:

    LOA 500 cm (16' 5")
    Beam 140 cm (55")
    Draft 15 cm (6")
    Displacement 315 kg (700 lbs)









    Last edited by flo-mo; 09-14-2018 at 10:36 AM.

  2. #2
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    Default Re: Cosmo 16-5 - a grown-up one sheet design


  3. #3
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    You are a wizard.


    Peace,
    Robert

  4. #4
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    Very good looking!

    What size engine do you recommend?

    Thanks,

    Woody

  5. #5
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    Leinwand

  6. #6
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    I like it a lot!
    The best helping hand you will ever receive is the one at the end of your own arm.

  7. #7
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    Based on the experience of Algis regarding his Tweak http://forum.woodenboat.com/showthre...Lithuania-2016, which in many aspects is similar to Cosmo and after some email exchange with the more knowledgeable forumite Whiskeyfox, my recommendation for the engine size is a 10 HP outboard motor.

    Quote Originally Posted by Woody Jones View Post
    Very good looking!

    What size engine do you recommend?

    Thanks,

    Woody

  8. #8
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    Default Re: Cosmo 16-5 - a grown-up one sheet design




  9. #9
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    Default Re: Cosmo 16-5 - a grown-up one sheet design


  10. #10
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    As I received two requests by prospective builders, I made a 1:10 scale model to be sure that all parts match properly.

    Fortunately they do:












  11. #11
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    This

    is

    awesome

    !!

  12. #12
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    I once drove myself almost insane working out effective ply layout on a bigger craft (without computer). Excellent job.

  13. #13
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    That is a wonderfully clean shape.

  14. #14
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    Nice design, do you have detailed performance data you could share? It seems to be of the type I was exploring in the thread http://forum.woodenboat.com/showthre...+planing+craft. On Low HP planing boats.

    Also what type of conditions are you designing for? Intuitively it seems like a fast an stage lake boat, but the low freeboard while understandable from a weight/performance perspective seems low for a coastal craft?

    Thanks for sharing your design.

    Max

  15. #15
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    Default Re: Cosmo 16-5 - a grown-up one sheet design

    After some study I hope I am able to provide somewhat reasonable performance data.

    Corresponding to the design data in this informative WoodenBoat Magazine article by Tad Roberts here are the figures for my design:

    COSMO 16-5

    LOA: 16' 5"
    LWL: 15.4'
    Beam: 55.5"
    Draft: 6"
    Displacement: 800 lbs
    D/L: 98
    Power: 10/15 hp
    Top speed: 11.7/14.8 knots
    S/√L: 2.98/3.77
    FN∇ : 2.28/2.88
    cp: 0.69
    B/L: 0.28

    LCB at 59% of LWL


    I used the Wyman speed formula for predicting top speed.

    (See article by Dave Gerr on "Practical Speed and Powering Calculation": http://www.westlawn.edu/news/Westlaw...d06_June08.pdf)

    Using Crouch's planing speed formula (Crouch constant 175) produces significantly differing results:

    Power: 10/15 hp
    Top speed: 19.2/23.5 knots



    Because of the low freeboard this design is only suitable for protected waters.
    Last edited by flo-mo; 02-08-2019 at 02:23 PM.

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