Rocker aft

Discussion in 'Boatbuilding' started by Knarf, Nov 23, 2019.

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  1. Knarf
    Joined: Nov 2019
    Posts: 3
    Likes: 1, Points: 3
    Location: North Alabama

    Knarf New Member

    Hi, I am building the Big Ben Garvey. I have the frames built and noticed there is some rocker just forward of the transom frame. (note that the frames are only temporary) I am wondering if anyone has built this boat and has any input on it ? I know at the sheer there is a "swoop" to it and maybe that is just the style and shape the boat takes. Back to the rocker, is it necessary and what purpose does it serve ? any input would be Great. I tried contacting Hylan and Brown (the designer) and I haven't heard back from them yet. If it matters I will be putting a 70 yamaha on it. Thank you

    20191123_154009[1].jpg
     
  2. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    What does the plans show ? Pictures on the net suggest no rocker aft
     
  3. BlueBell
    Joined: May 2017
    Posts: 860
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    Hi Knarf,

    Welcome to the forum.
    I have not built that boat.
    Yes, the rocker is necessary or the designer wouldn't have put it there.
    It may serve many different purposes, it's complicated.
    Too bad the designers aren't responding.
    Include it because to not include it, would be a big mistake.
    Unless the plans don't call for it...
     
  4. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    @Knarf, the boat doesn't seem to have rocker aft. Is it possible that the base you have taken to place the frames is not correct?. The photo seems to guess that the sheer line is a straight line, which is not correct.
     
  5. bajansailor
    Joined: Oct 2007
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    Location: Barbados

    bajansailor Marine Surveyor

  6. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

  7. Knarf
    Joined: Nov 2019
    Posts: 3
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    Location: North Alabama

    Knarf New Member

    @Mr Efficiency Plans don't necessarily show rocker at the chine but there is rocker at the sheer (as per picture). I am going to loft a side panel with cardboard and see what it shows. I have measured and measured and checked angle of transom etc. and cannot find a mistake.
    @TANSL The sheer will be straight if I make the chine straight and that is why I am not sure where to go. Picture shows rocker (an arc) in the sheer but not the chine. everything else measures out. I've lofted everything on plywood prior to building the frames so I have a good place to double check my measurements
    @BlueBell Thankyou. I will wait until Wed morning, hopefully designer will respond

    I am hoping designer was out of office last week and they respond early this week.

    Thank you everyone
     
  8. TANSL
    Joined: Sep 2011
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    Location: Spain

    TANSL Senior Member

    Thats correct.
    In the photograph of post # 1 it follows that the sheer line is a straight line, which is not correct.
     

  9. Knarf
    Joined: Nov 2019
    Posts: 3
    Likes: 1, Points: 3
    Location: North Alabama

    Knarf New Member

    I see that picture in the plans. The lofting numbers are the same at the chine for frame 8 and the transom frame but different at the sheer which will give it the arc at the sheer. I'm guessing that the angle of the transom is what is creating the rocker at the transom. (all measurements are from a baseline).
    Well I think Thankyou for helping me walk through this. I went to the plans and apparently I didn't check everything. The plans show a table of numbers for the lofting but there is also measurements at the bow and stern (measured along the angle of each) which don't add up to the (table of measurements) but it would put the bottom flat. Now I have to fix the bow and stern :) Good thing I enjoy this
    Once again Thanks to all
     
    BlueBell likes this.
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