Determining prop thrust

Discussion in 'Inboards' started by YuriB, Sep 29, 2008.

  1. YuriB
    Joined: May 2008
    Posts: 56
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: Russia

    YuriB Junior Member

    Hi everyone.
    Who knows how to find out what thrust bearing size i should install on my boat? The boat was former navy and was towing an array, so that existing thrust bearings were too big and were dismantled because of wear. Is there any formula to calculate the thust?
     
  2. FAST FRED
    Joined: Oct 2002
    Posts: 4,519
    Likes: 109, Points: 63, Legacy Rep: 1009
    Location: Conn in summers , Ortona FL in winter , with big d

    FAST FRED Senior Member

    A rough rule of thumb is each HP the engine can deliver will give MAX 25 lbs of thrust.

    Very few are better than 20 lbs per hp in real life.

    FF
     
  3. YuriB
    Joined: May 2008
    Posts: 56
    Likes: 1, Points: 0, Legacy Rep: 15
    Location: Russia

    YuriB Junior Member

    Thank you Fast Fred
     

  4. DMacPherson
    Joined: Mar 2005
    Posts: 138
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    Location: Durham, NH USA

    DMacPherson Senior Member

    More than 25 lb/hp is possible...

    Just a follow up. The figure of 25 lbs/hp is a fairly traditional value that is still a reasonable estimate for free-running vessels. However, for vessels with propulsion systems designed for towing (i.e., bollard pull) it is not uncommon to see values approach 30 lbs/hp or even higher. For example, we evaluated a bollard test for one of the newer ducted systems (with a contemporary propeller design and high-efficiency nozzle) which reached 32 lb/hp.

    Regards,

    Don MacPherson
    HydroComp, Inc.
     
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