Transom knee´s and their position

Discussion in 'Fiberglass and Composite Boat Building' started by Dragonsailor, May 4, 2010.

  1. Dragonsailor
    Joined: Aug 2008
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    Location: Uddevalla, Sweden westcoast

    Dragonsailor New Member

    Hi

    I am currently making some redesign of a small racing catamaran, just above 4 meters length.

    My question is; were to place the two knees supporting the transom, in an optimal way.

    The catamaran will be fitted with an engine bracket. Should the knees be positioned just "outside" the bracket screws (app. 400 mm apart), or halfways to the transom end (600 mm apart)?

    If you want to get support from the side hulls (not the tunnel), can you place the kness with let´s say 45 degrees angle from boat centerline so you get a "connection" between the transom and the side hulls? Is this a common way or not?

    The attached picture shows the inside of the hull with the two knees 600 mm apart. The two small horisontal lines on the transom shows the bracket screws centerline.

    Thank´s in advance!
     

    Attached Files:

  2. Dragonsailor
    Joined: Aug 2008
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    Location: Uddevalla, Sweden westcoast

    Dragonsailor New Member

    Another question for my understanding: how are the loads/forces distributed in this area. The engine want´s to rotate around its pivot point, the engine bracket. The bracket want´s to twist the transom, the upper edge backwards and the middle/bottom forwards. Right? The transom knees then handles a lifting force away FROM the bottom of the hull. When reversing the engine, the knees will handle a force TOWARDS the hull bottom. Right?
     
  3. alan white
    Joined: Mar 2007
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    alan white Senior Member

    It's very hard to see what you're doing there. Could you draw a picture that illustrates the thing better? it may just be that you've got too much detail where you need none and not enough where you do.
    Maybe it's me too, dunno.
     
  4. Dragonsailor
    Joined: Aug 2008
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    Dragonsailor New Member

    Hi Alan

    Sorry for to many details... for me working with this everyday, everything is clear regarding the drawing. Not for others, of course... However, we decided to have the knees as usual, along the boat centerline. The hull and tunnel are stiff enough. Anyway, thanks for your reply!
     
  5. GG
    Joined: Jan 2008
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    Location: MICH

    GG offshore artie

    [​IMG] these knees are on a 32 on a Skater .
     
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  6. Dragonsailor
    Joined: Aug 2008
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    Location: Uddevalla, Sweden westcoast

    Dragonsailor New Member

    Thank´s for picture G.G

    I can see three knees, but the fourth should be closer to the camera, to the most right of the pic. Good picture showing the framework for the tunnel. I gess the boat and transom is rebuilt and therefore no holes for the engines.

    Thanks again:)
     
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