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Feathering Propeller

  • December 08, 2015 1:40 AM
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    Message # 3687290
    Deleted user

    I have been offered an as new Autostream RH feathering prop as a replacement. This prop has been set at a pitch of 8"and bored with a shaft of 1"

    I want to know if that propeller is suitable for my WS32 ( s/v Loukia hull # 518) now powered with a BETA 35 hp with a 1" shaft and gearbox reduction ratio of 2:1

    If the offered prop is appropriate then I'd like to go ahead as I currently have Loukia on the hardstand and I need to replace the cutlass bearing.

    Any advice on this will be most welcome.

    David Timbs
  • December 08, 2015 3:06 PM
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    Reply # 3688684 on 3687290
    Deleted user

    David you missed an important number = the diameter

    but if it is around 17" then yes it should work.

    if it is less say 16" you may want to adjust the pitch up to 9" to 10" of pitch +/-

    Hope this helps but please do your own cal cal  for prop = mostly OK

    it will give what it calculates as the best, but there is room on either side.

    Fair winds :

    Norm

    Last modified: December 09, 2015 7:02 PM | Deleted user
  • December 08, 2015 11:23 PM
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    Reply # 3689467 on 3687290
    Deleted user

    Thanks Norm,

     The diameter is 15". So you reckon I'd need to have it pitched up to say 10", or more? I'm in Queensland, Australia and I'm hoping to learn a lot through this great site. I've been a member for quite a while but only now have I become a proud owner.Your good advice is much appreciated.

    Dave Timbs
  • December 09, 2015 11:26 AM
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    Reply # 3690375 on 3687290
    Deleted user

    David:

    If you are at 15"od I would GUESS some where between 10" to 12" pitch would work. If the prop is adjustable then you are set! Pick the middle and then after 2 years of motoring / sailing and and at the next haul out, you will know if it was right. If you can NOT get to max rpm = over pitched, or if you hit the governer easy = under pitched.  If you have it close to correct you should be able to hit 5.8 to 6.2 kts. the higher # would = close to best setting.

    I would think Autostream would have a calculator to give you an estimate (better than mine)??

    But best of luck

    Norm

    Last modified: December 09, 2015 7:13 PM | Deleted user
  • December 10, 2015 3:00 PM
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    Reply # 3692730 on 3687290
    Anonymous member

    Ahoy David,

    In my own opinion, Norm is being a little too conservative in his speed estimate.  Engineers tend to be that way.  I believe that you should be able to realize 6.8k to 7.0k as a top motoring speed with that engine. 

    My engine is a Westerbeke of the same displacement as your engine.  It is rated at a slightly higher HP and RPM than your engine, but at a slightly lower torque rating.  At 2100rpm, running the measured mile, my speed is 5.61k,  That is my cruising speed.  My top speed is 7.3k at 3200rpm.

    Norm gave good advice though.  Make a guess of about 11" pitch and then adjust it accordingly the next time.  Ideally, if your engine is governed at 2800rpm, then you should be able to turn about 2750rpm when wide open in gear.  You should be real close to 7.0k.

    I would like to know what others are seeing, as a top speed, with the Beta.

    Good luck with your new boat.  I'll keep an eye open for you, down the road.

    Dave
  • December 11, 2015 5:01 PM
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    Reply # 3694607 on 3687290
    Deleted user

    Dave,Norm and others,

    I think I've now got this sorted; many thanks for good advice on very interesting technical issue.

    Dave Timbs