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  1. #1
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    Default 6 streak plywood coble design

    Some time ago I posted a thread about building this model of a 4 streak Cullercoats coble of 1820


    I lofted the boat in Freeship, and created the plank expansions within it.

    This sparked the idea of designing a 6 strake boat that could be built from 16 foot by 4 plywood with a minimum of scarfs. It would be a motor boat suited for working off of our flat sandy beach, so a motor in a well on a tunnel stern was selected, that way the propeller would be protected between the scorvels, and she could back onto or motor straight off of the beach. The only framing would be the floors supporting the inner bottom and buoyancy tanks serving as thwart and bow and stern sheets.

    This is the lines plan that came out of the exercise.




    The GA



    and the plank developments, nested on a 16 x 4



    From these I was able to print off plans at my favoured scale of 16th or 3/4' to the foot in order to build a proof of concept model, (see following posts).
    It really is quite difficult to build an ugly wooden boat.

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  2. #2
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    Default Re: ^ streak plywood coble design

    First off, the components, cut from 1/8th, 1/16th and a crook of 1/4 inch for the stem.

    I also built a generic short shaft OB.

    The full size building jig would be assembled out of 2x4s, but plywood does here.


    The inner bottom, stern, ram plank, buoyancy tanks/motor well. and stem were erected on the jig and faired up.



    Then we could start hanging plank.

    Garboards, with a lot of twist to create the tunnel sides.



    Second and third strakes complete the bottom





    Sides next
    It really is quite difficult to build an ugly wooden boat.

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  3. #3
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    Default Re: ^ streak plywood coble design

    Next the rising strake, followed by topsides and shear.



    I needed to extend the jig with temporary moulds. These had to be temporary due to the tumblehome of the shear strake.



    You can see where the temportary moulds were glued to the base board.





    The skorvels complete the "externals"



    Next the standing knees to strengthen the shear strakes.
    It really is quite difficult to build an ugly wooden boat.

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  4. #4
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    Default Re: ^ streak plywood coble design

    The knees are canted, as on the big cobles, as it increases the gluing area.



    The motor well is supported by a beam to allow more open space.

    Fit out complete with breasthook, external gunwales and scut board across the stern.



    She needs a rudder and oars.



    A view down the motor well, the cavitation plate must be enlarged to alloew the prop to pass through the ram plank and then close the opening.



    Ready to go



    Next, general views of her shape.
    It really is quite difficult to build an ugly wooden boat.

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  5. #5
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    Default Re: ^ streak plywood coble design

    General views of her shape, including an "up skirt" of the tunnel.







    The lower gudgeon is an eyebolt that may be used to winch her up onto her trailer.

    That,s all Folks.
    It really is quite difficult to build an ugly wooden boat.

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  6. #6
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    Default Re: 6 streak plywood coble design

    Curves in the right places....



    That tunnel looks like it would be a challenge. I like the canted knees.

  7. #7
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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by skaraborgcraft View Post
    That tunnel looks like it would be a challenge. I like the canted knees.
    Yes, that is my only worry, with soft fir at scale thickness it twisted OK, but it might need a bit of heat to persuade ply to behave.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: 6 streak plywood coble design

    Do you have full scale build in mind Nick ?
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by PeterSibley View Post
    Do you have full scale build in mind Nick ?
    It would be fun, but I don't really need another boat.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Peerie Maa View Post
    It would be fun, but I don't really need another boat.
    Do any of us? Build it for the enjoyment of building.

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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Jim Ledger View Post
    Do any of us? Build it for the enjoyment of building.
    That's why I'll build my next boat !
    '' You ain't gonna learn what you don't want to know. ''
    Grateful Dead

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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by PeterSibley View Post
    That's why I'll build my next boat !
    That's why I'm building the catboat...that and it makes a damn good thread.

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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Jim Ledger View Post
    That's why I'm building the catboat...that and it makes a damn good thread.
    Wait. There's a catboat build thread?

    Peace,
    Robert

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    Default Re: 6 streak plywood coble design

    Nick,

    Lovely model, eh.

    But, you're wrong. That's EXACTLY the type of boat you NEED.

    Okay, back to serious. I really think those are lovely craft. I think a six strake sailing version would be dreamy looking.
    Peace,
    Robert

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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by amish rob View Post
    Nick,

    Lovely model, eh.

    But, you're wrong. That's EXACTLY the type of boat you NEED.

    Okay, back to serious. I really think those are lovely craft. I think a six strake sailing version would be dreamy looking.
    Peace,
    Robert
    For a sailing version without the motor well, i can do you a 4 strake hull.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Peerie Maa View Post
    For a sailing version without the motor well, i can do you a 4 strake hull.

    Now if there is ANYONE here who does NOT need another boat project, it's me. Haha.

    The four strake is lovely, too, though. Something about the cobles I just like. They are sort of odd, but just perfect at the same time, eh?

    Peace,
    Robert

  17. #17
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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by amish rob View Post

    They are sort of odd, but just perfect at the same time, eh?

    Peace,
    Robert
    Very much horses for courses. Perfectly developed for backing onto a flattish beach through surf.

    It really is quite difficult to build an ugly wooden boat.

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  18. #18
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    Default Re: 6 streak plywood coble design

    Those pictures are great! That's exactly what I mean. One look at the boat would cause one to wonder as to the unusual shape, eh?
    Then, once the boat is explained, her shape makes all the sense in the world.

    For the record, I find the hull shape quite pleasing.

    Peace,
    Robert

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    Default Re: 6 streak plywood coble design

    Those garboards might be a bit of a challenge,but hugely satisfying when the finished boat materialises.Did the various home ports have a tendency to any particular colour schemes?

  20. #20
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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by John Meachen View Post
    Did the various home ports have a tendency to any particular colour schemes?
    Yes, but I think that they changed with time. At Culklercoats in 1820 each strake was a different colour. Now painted cobles are mainly one colour with an occasional white shear strake, whilst at Flamborough they favour varnished topsides. The fishing registry numbers and port hail are often decorative as well.
    It really is quite difficult to build an ugly wooden boat.

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  21. #21
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    Default Re: 6 streak plywood coble design

    Nick I've got to say this although I appreciate the effort entailed I cannot understand your desire to change a craft that "evolved" over centuries.

    Being polite can be carried to extremes when comments are posted, but come on that looks awful.


    These buoyancy spaces you mention, how will one access that area to render any damage that should need attention once ashore?

    PS. I don't think that rudder will work efficiently either, it's not "grabbing" enough depth of water?
    Last edited by Chippie; 07-14-2017 at 03:45 AM.

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    Default Re: 6 streak plywood coble design

    Access hatches are common in glass or plywood boats for either stowage access or just venting. If in need of a bigger hole, use a jigsaw, no more work than having to remove the entire furniture structure on a "traditional" boat if repairs are needed.

  23. #23
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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Chippie View Post
    Nick I've got to say this although I appreciate the effort entailed I cannot understand your desire to change a craft that "evolved" over centuries.

    Being polite can be carried to extremes when comments are posted, but come on that looks awful.These buoyancy spaces you mention, how will one access that area to render any damage that should need attention once ashore?

    PS. I don't think that rudder will work efficiently either, it's not "grabbing" enough depth of water?
    The only difference apart from size is that the tunnel is formed from the only the garboards rather than 3 or 4 narrower strakes. The stern is slightly wider in proportion, but I think that to be OK on a smaller motor coble.

    You may be right about the rudder. End plates may be the solution, or if that doesn't hack it a longer rudder but less convenience may be required.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Peerie Maa View Post
    The only difference apart from size is that the tunnel is formed from the only the garboards rather than 3 or 4 narrower strakes. The stern is slightly wider in proportion, but I think that to be OK on a smaller motor coble.

    You may be right about the rudder. End plates may be the solution, or if that doesn't hack it a longer rudder but less convenience may be required.


    Forgive me "end plates" escapes me?

  25. #25
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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Chippie View Post
    Forgive me "end plates" escapes me?
    Here you go


    They increase the effective aspect ratio of the foil by affecting the tip vortex.
    It really is quite difficult to build an ugly wooden boat.

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  26. #26
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    Default Re: 6 streak plywood coble design

    I was thinking more on the "balanced rudder" idea, but let us avoid simplicity.

  27. #27
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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Chippie View Post
    I was thinking more on the "balanced rudder" idea, but let us avoid simplicity.
    It would help, but be impossible to unship for trailering.
    It really is quite difficult to build an ugly wooden boat.

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  28. #28
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    Default Re: 6 streak plywood coble design

    "Prevarication"


    An appropriate name for her just sprang to mind Nick.


    http://forum.woodenboat.com/showthre...with-Endplates

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    Default Re: 6 streak plywood coble design

    Nick,

    Thanks for posting this, it is a really interesting design.
    i have a few questions:
    -what is the 'scut' board for?
    -why does the Coble have such a deep section (forefoot?) at the bow?
    -why were these boats backed into the beach?

    Thanks in advance!
    Ralphie

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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Ralphie Boy View Post
    Nick,

    Thanks for posting this, it is a really interesting design.
    i have a few questions:
    -what is the 'scut' board for?
    -why does the Coble have such a deep section (forefoot?) at the bow?
    -why were these boats backed into the beach?

    Thanks in advance!
    Ralphie
    The scut board forms both the quarter knees tying the stern together and is bored for the upper gudgeon.
    She has a deep forefoot so that when she is backing onto the beach the stem grounds first and keeps her head to the seas.
    They are backed onto the beach so that the bow parts the waves.
    It really is quite difficult to build an ugly wooden boat.

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  31. #31
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    Default Re: 6 streak plywood coble design

    Why not just ensure the outboard can turn 360 degrees and dispense with the rudder?

  32. #32
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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Chippie View Post
    Why not just ensure the outboard can turn 360 degrees and dispense with the rudder?
    You will be suggesting a vertical transom to hang the OB on, using the tilt mechanism when on the beach, doing away with the scorvels, and not designing a coble at all next.
    It really is quite difficult to build an ugly wooden boat.

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    Default Re: 6 streak plywood coble design

    Quote Originally Posted by Peerie Maa View Post
    You will be suggesting a vertical transom to hang the OB on, using the tilt mechanism when on the beach, doing away with the scorvels, and not designing a coble at all next.
    You cannot "design" a coble Nick it EVOLVED through generations of observations and adjustments to achieve the perfection they are for the particular job they are required to do. All without a Naval Architect in sight. But you already knew that I know.

    I was treating this as some inexperienced persons attempt at a pleasure craft until I reread this statement @ #1...

    "It would be a motor boat suited for working off of our flat sandy beach, so a motor in a well on a tunnel stern was selected,"

    Now a tunnel is nothing new (we've already discussed that) neither is tweaking layouts, but you are throwing conventional layouts out of the window most work in cobles involves the working from the stern to slightly abaft of amidships. you choose to eliminate that with an engine obstructing most operations one would encounter.

    And, no I would not have been advocating anything hanging off the stern (I tried that path but to be successful it would have required a "long shaft" motor, but I had already purchased a "short shaft" and I had to adapt by piercing the ram and it worked , but that's another story.

  34. #34
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    Default Re: 6 streak plywood coble design

    Yippie! all is not lost Nick.

  35. #35
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    Default Re: 6 streak plywood coble design

    ^ LOL...wheres the damn like button? Surely one can be considered to "work" off a beach, even if going fishing with a rod and reel? I dont think Nick had commercial fishing in mind.

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