s there a handling benefit to having a flatter back end of the boat?

Discussion in 'Wooden Boat Building and Restoration' started by ncuster, Jun 18, 2007.

  1. ncuster
    Joined: Jul 2006
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    ncuster 1968 Chris Craft Ski

    I am re-fiberglassing the hull of a 1958 CC Ski, and have run into an issue that stumps me!

    After removing the fiberglass (which we used just a crow bar and circular saw - directed to last poster), we found that there were cedar barn-style siding screwed to the mahogany planks. Each piece of siding was a wedge shape about 6 inches wide and 8 feet long. These were in bad shape since the bottom was glassed in 1970. These cedar planks were placed on the outside corners of the hull seemingly to flatten the hull. It increased the dept of the hull at the outside corners about 1/2 inch.

    My question is: Is there a point to having these on? Is there a handling benefit to having a flatter back end of the boat? I imagine there was a reason the refinisher did this... but I am stumped as to what it is.

    It handled so well before the bottom needed replacing, I'd hate to change it, but this seems odd to me.

    Thank you all for any feedback/advise.

    Nathan
     
  2. charmc
    Joined: Jan 2007
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    charmc Senior Member

    I'm not sure from your description if the shallow wedges flatten a very shallow V, or project below a flat bottom. If the boat was used for tournament skiing, a modification like that might have been done to produce a "flatter" wake. I can't think of any other purpose, but others with ski boat experience might know more.
     
  3. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    It's possible the boat developed a hook and this was removed with the wedges. It's also possible the boat needed to run flatter, for some trim reason, so some hook was added to the run. Not knowing exactly what you're referring, makes for little more then guess work, unfortunately. Some photos will be necessary, but it's very likely the hull displayed some bad habit and the wedges were an attempt to correct. If these bad handling manners could be removed without the wedges, is again guess work, without further information and images of the area.
     
  4. ncuster
    Joined: Jul 2006
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    ncuster 1968 Chris Craft Ski

    I'll post some pictures as soon as I get them uploaded.

    The cedar planks didn't project below the flat bottom, they were only placed on the outside of the boat so it created a flatter bottom.

    The wake on this boat was perfect for high speed skiing, and maybe the planks have something to do with that. Thanks for the info.
     
  5. Ike
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    Ike Senior Member

    On most planing boats the after planning surface should be flat when you lay a straight edge on them (the straight edge should be pointing fore and aft). Most ski boats do not have a vee, they are pretty much flat across the back of the boat, some may have a slight curve. This is to lay down a nice flat wake for skiing. I suspect this boat had some curvature and they were trying to flatten the bottom at the transom. Pictures would help.
     
  6. ncuster
    Joined: Jul 2006
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    ncuster 1968 Chris Craft Ski

    Pictures of the pieces of siding to clarify

    Attached are several pictures of the pieces of cedar siding.

    In one of the pictures all cedar trim pieces are removed, but you can still see the shadow of the one on the end where they once were. There were three 8" wide pieces overlapped on each side, then covered in bondo to smooth out the ripples, then fiberglassed over.

    I hope this give you a better idea of the situation. Unfortuanately I don't have any pictures of my holding a level to the back to see what effect in flattening out the bottom the strips of wood had.

    Nathan
     

    Attached Files:


  7. Ike
    Joined: Apr 2006
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    Ike Senior Member

    It appears to me that the hull had a slight vee at the transom and someone wanted to make it a flat bottom. For a ski boat this is good because it flattens the wake. It would also make it a little heavier in the stern, again flattening the wake but throwing a bigger stern wave behind the boat.
     
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