efficient 10m displacement powercat (build thread)

Discussion in 'Boatbuilding' started by groper, Apr 15, 2012.

  1. DennisRB
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    DennisRB Senior Member

    Congrats. Finally its pay off day. What a great personal achievement this has been.

    Is it worth it to get new props? I guess a low 20 cruise is fine with these props? Would cruising economy suffer with less pitch? If so it seems a waste just to get bit more top end, but then again the boat is only going to get heavier so less pitch might not be a bad thing.
     
  2. groper
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    groper Senior Member

    Yep - its going to get a bit heavier and we only had the fuel tanks half full... I think it should get better economy if the engines are loaded correctly rather than over loaded, im not doing it for top end speed - ill never run it there, for me its more about efficiency and with less slip but same diameter the propeller efficiency should improve a bit - which mean less fuel at the end of the day.

    Had her out to the reef and back - 40Nm round trip - sat on 20kts on the way out and came home at 17kts... all went well, no problems showed up yet so im pretty chuffed :)

    Ill put up some videos soon...
     
  3. Mr Efficiency
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    Mr Efficiency Senior Member

    17 knots would be close to an optimal speed, imo. You may need to go down to 17" props by the sound of it, and top speed would be little different, imo. You'd only want top speed for bar crossings, not an issue in your part of the world really.
     
  4. isladelobos
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    isladelobos Junior Member

    Yeah man!! well done.

    We need see beers, fisheds and nice womans taken sun in this beautiful deck. :D
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    It's a sterling achievement that gives hope to a lot of budding builders, and feelings of inadequacy to others, perhaps.
     
  6. groper
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    groper Senior Member

    Running at 20kts

     
  7. groper
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    groper Senior Member

    Running at 17kts...

     
  8. waikikin
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    waikikin Senior Member

    Sweet!!
    An absolute joy to behold.
    Well done Groper:D
     
  9. Mr Efficiency
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    Mr Efficiency Senior Member

    I was a bit concerned about the nice womans falling off into the water !
     
  10. Jim Caldwell
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    Jim Caldwell Senior Member

    Great Job, don't you love it when a plan comes together!!!!
     
  11. Mr Efficiency
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    Mr Efficiency Senior Member

    Big effort considering he works full-time.
     
  12. Saqa
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    Saqa Senior Member

    Mate thats really awesome, congrats on it all coming together and working as expected. Now get out there and blood it :)

    Decided on her name yet? Well done mate, love it!
     
  13. Richard Woods
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    Richard Woods Woods Designs

    I haven't been reading this forum much the last few weeks as I am on my Skoota 28 powercat at anchor in the Bahamas and wifi is shaky at best. (Too slow today to watch the videos)

    Congratulations on your launch and first trial. Had I read the thread last week I would have said that 27-28 knots would be a good speed for your first test. I have found that (rule of thumb) for every extra knot you need another 10hp once past about 15 knots

    I assume you will temporarily ballast the boat before changing props. Will you also check the fuel consumption when running on one engine instead of 2 at 17 knots? It may be better. The engine offset angle is only a few degrees, so that is how we run when not in a hurry

    If you do that then you'll need to rethink the prop pitch

    I also didn't like the dangling feet, although I assume the bodies were well attached to the boat!

    Richard Woods of Woods Designs

    www.sailingcatamarans.com
     
  14. Tungsten
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    Tungsten Senior Member

    awesome!! I'm going outside to shovel snow now.
     

  15. groper
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    groper Senior Member

    after our first trip i pretty much decided that i have to add a trampoline up the front... Without it you loose such a great space to lay down on and relax, its also much quieter up there away from the engine noise etc and it has great utility for dealing with the anchor and not falling overboard etc - one thing i cant improve is the shade from a sail above ! - oh well there is always the next boat :D

    So is there any propeller gurus reading this thread? I need to work out what props will suit this boat - currently have 13 7/8 x 21 - 3 blade SS. This boat will never be run much above 20kts and im interested in best fuel efficiency between 17-21kts...

    There happens to be 2 counter rotating props for sale - almost new - 14.25x17 4 blade SS.
    Going from 3 blades to 4 and dropping 4inches of pitch, slight diameter increase - how do you work all this out ?? One thing iver never studied up to this point is propellers...
     
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