new project

Discussion in 'Projects & Proposals' started by garrybull, Sep 11, 2013.

  1. garrybull
    Joined: Nov 2010
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    Location: portsmouth england

    garrybull Senior Member

    it tracks fine in pretty most all situations but it dont like the side on wind and tide too much.

    its fine but i have to keep correcting the steering to keep it straight.

    was out today and it was a tad choppy on the way back with wind and tide side on all the way back in.

    the boat handles the bigger waves no problem at all.

    i was doing around 16-20 knots all the way back in in what was probably a force 5 side on.

    other than that its spot on.
     
  2. SamSam
    Joined: Feb 2005
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    Location: Coastal Georgia

    SamSam Senior Member

    Congratulations! Very well done! Now all you need is a bigger shop with more room for upgraded calendars!
     
  3. Mr Efficiency
    Joined: Oct 2010
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    Location: Australia

    Mr Efficiency Senior Member

    OK, it does not sound too onerous, I have heard complaints about directional stability in similar boats that sounded worse.
     
  4. garrybull
    Joined: Nov 2010
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    Location: portsmouth england

    garrybull Senior Member

    thanks mate.

    now a bigger workshop with more calendars sounds great lol.
     
  5. garrybull
    Joined: Nov 2010
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    Location: portsmouth england

    garrybull Senior Member

    stability wise in any direction whether wind over tide or side on wind and tide or following tide its great.

    i have been out in some rough stuff lately and never felt unsafe at all.
     
  6. JSL
    Joined: Nov 2012
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    Location: Delta BC

    JSL Senior Member

    The directional stability motion sounds like it could be early 'progressive heeling' (sometimes called chine walking) and possibly bow steering. Many boats will do it if heavy and or trimmed to run level and plow through the water. My favorite was 33' assymetrical hull cat (not my design,fortunately) that would get up on a plane, increase speed to about 25 knots and then flop over (port or stbd) to about a 15 deg. heel. The speed would slow but before any other 'events' happened the skipper would chop the throttle. Overall, it was quite scary.
    The irony here was that the problem was worse when the seas were flat calm or 'glassy'. The best explanation might be that rough water helps ventilate the bottom and reduce 'negative' lift that causes the problem.

    The boat was essentially useless and the owner called me in to help make it useable. The 'fix' did not totally solve the problem but at least it made the boat useable and did not terrify the occupants. The costs added about 30% to the end price. Not cheap!
     
  7. garrybull
    Joined: Nov 2010
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    Location: portsmouth england

    garrybull Senior Member

    thats interesting to know.

    so how did you overcome the healing problem?

    mine does it slightly but if i move gear around that sorts it out and it runs flat as it should.
     

  8. JSL
    Joined: Nov 2012
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    Location: Delta BC

    JSL Senior Member

    One major culprit is weight & LCG. Heavy planing hulls with level or bow trim are sometimes afflicted. When testing a planing hull one trial I do/suggest is to trim the boat level, run up the speed, and see what happens.. all in smooth water. Quite a number of boats will 'heel' and if it is rapid it could lead to a violent broach and real trouble. The boat would not normally be operated like this but it could be... by an inexperienced operator. It is always nice to know. Catamarans can sometimes have the same characteristics.
    The cat mentioned was some years ago so the 'fixes' are from memory:
    (a) Move LCG aft- Repower - heavier engines -Fuel tank added onto transom swim grid- etc.. We moved loose stuff (anchor, stores, etc) as far aft as we could.
    (b) Improve bottom ( a bit of a gamble) -add strakes, chine rails.
    (c) We also fitted strakes on the tunnel wall because it was a bit narrower than usual design practice and had excessive 'wetting'.
    The original speed was about 28 kn. (if you could get there), the final top speed was 44 kn. A bit skittish... but useable.

    attached photo not the best but gives you an idea

    on one 23' monohull it was so bad we tried transvers steps-. but is did not work. It was a poor design and I cautioned the owner about this prior to any work/modifications being done.
     

    Attached Files:

    Last edited: Jun 23, 2016
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