Hull design improvements

Discussion in 'Powerboats' started by livinxs, Dec 28, 2003.

  1. livinxs
    Joined: Dec 2003
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    livinxs New Member

    I currently have a 250 BAja Sport with a single Merc 7.3 and TRS drive. I'm looking for suggestions on designing hull improvements (or other suggestions) for improving top end. The boat seems to ride bow down at speed, I assume ddue to the location of the engine further forward than with a Bravo drive. Is it feasible to notch the transom or install steps in the hull without ruining the boat? I have the ability to do fairly extensive fiberglass work, but I'm not sure where to start with the mods. Thanks.
     
  2. Willallison
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    Willallison Senior Member

    If it is a problem of having weight too far fwd, then I'd try moving other on-board weights aft before going to the rather drastic measure of making hull mods.
    Move the batteries, perhaps tanks etc aft and see if that makes a difference.

    The other obvious question is whether you have the drive and tabs correctly trimmed....
     
  3. gonzo
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    gonzo Senior Member

    Why were the modifications made? More often than not going to the original design solves the problem.
     
  4. livinxs
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    livinxs New Member

    The TRS drive was standard equipment when the boat was new. I've considered moving "other" items as well, the fuel tank may be difficult because of the general lack of space in the stern. The trim tabs are rarely used except for trimming side to side, they just aren't needed. Thanks for your responses.
     
  5. Ami

    Ami Guest

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  6. Willallison
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    Willallison Senior Member

    As a start, you could always grab 4 of your burly mates and stick them down the back - see what happens....

    What about the drive? What happens when you trim that up - it may even be that the rams need new seals - take a look over the transom and make sure that the leg remains trimmed out after you've been running for a few minutes.
     
  7. gonzo
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    gonzo Senior Member

    Good call Will. What happens at different angles of trim?
     
  8. Willallison
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    Willallison Senior Member

    Failing all that, I s'pose you could pull the boat out of the water and check to see if the hull has a hook in it...not unknown, even from a reputable builder to pop an occaisional dud from the mold.
    Run a straight edge along the bottom, bow to stern. If the ruler touches at the tips, but not in the middle, then the boat has a hooked bottom - if speed's what you're after, chuck it and buy a new one..:(
     
  9. livinxs
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    livinxs New Member

    Thanks for all of the input! I will check the bottom over the Holiday's. When the drive is trimmed up the nose does rise, slightly. However, You still get the feeling that the boat will nose into the next big wave instead of fly over it. From the responses I'm getting a major retooling of the hull may not be worth it.
     
  10. Stephen Ditmore
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    Stephen Ditmore Senior Member

    What would you all think of cutting away a slice of the forefoot from midships forward, creating a forward "pad"?

    (This is not a recommendation, just conjecture. I agree with checking for hook, changing drive trim, and moving weight aft.)
     
  11. gonzo
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    gonzo Senior Member

    I have done "aftermarket fixes" with well placed lifting strakes. They may create drag, but the improved trim will make the speed increase and fuel economy improve.
     
  12. Willallison
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    Willallison Senior Member

    Interesting thought Stephen.......never seen it done up for'ard before so I don't know what effect it might have. You would create additional lift forward - though at speed, I would have thought most of this region should be running clear of the water. Same with your suggestion Gonzo.....have you installed 'lifting strakes' on high speed craft before? Where are they placed - fwd or aft?
     
  13. gonzo
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    gonzo Senior Member

    I have installed them both forward and aft depending on the correction needed. Also, I used spray rails to produce lift and reduced wetted area in lobster boats. A 38' Duffy increased top speed by about 5 mph.
     

  14. scottydog
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    scottydog New Member

    Weight Problem.



    :idea:

    WEIGHT DISTRIBUTION PROBLEM , I CAN HELP.
    :idea: SEND ME PICTURES OF VESSEL IN/AND OUT OF THE WATER SO I CAN DETERMINE THE WATERLINE. ALSO IF YOU HAVE ANY SPECS ON THE HULL IT MAY BE HELPFUL. AS WELL,I NEED AN ACCURATE WEIGHT ON THE POINTS I CONFIGURE FROM THE PHOTOS YOU SEND ME.
    DETERMINE WHERE THE CENTER OF GRAVITY AND DETERMINED WATERLINE ARE LOCATED.
     
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