Help with Propulsion

Discussion in 'Boat Design' started by standman, Nov 27, 2021.

  1. standman
    Joined: Mar 2015
    Posts: 51
    Likes: 7, Points: 18, Legacy Rep: 10
    Location: Cebu

    standman Junior Member

    Hi All,
    I enjoyed a 16ft. boat I built and decided to built a 49' version. I am now at the stage where I need to install the propulsion.
    Power will be from twin 360HP 2200 RPM Diesel
    ZF V drive 2.06:1
    Waterline length 45'
    draft 2ft
    beam at waterline 12'
    vessel weight about 13 tons loaded
    Target max speed 24 cruising 18 knots
    propeller 28 x 34.8 x 3 (55% coverage) (recommended size by prop maker)
    So what I have available are 2 or 2.5" Stainless 304 shafts. I'm worried with 2" ( should I be?)
    rudder is twin 3.06 sq. ft. - adequate?
    The propeller strut i need to fabricate, single or v type?
    about 6' of the shaft is exposed - will this need 2 struts?
    30KG Delta anchor ok?
    TIA for the input
    propulsion.jpg
     
    kapnD likes this.
  2. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,386
    Likes: 1,042, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    Quite a step up in size, shall we say about 30 times ? Any pictures or drawings ?
     
  3. standman
    Joined: Mar 2015
    Posts: 51
    Likes: 7, Points: 18, Legacy Rep: 10
    Location: Cebu

    standman Junior Member

    will resize pics and video as I can't seem to upload them boq-2.jpg boq3.jpg
     
  4. standman
    Joined: Mar 2015
    Posts: 51
    Likes: 7, Points: 18, Legacy Rep: 10
    Location: Cebu

    standman Junior Member

    boq5.jpg
     
  5. Mr Efficiency
    Joined: Oct 2010
    Posts: 10,386
    Likes: 1,042, Points: 113, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    OK, that gives a fairly good idea, what is she made of ? Is it a scaled-up version of the small boat ? My initial thought was she might slap on those very wide chines.
     
  6. standman
    Joined: Mar 2015
    Posts: 51
    Likes: 7, Points: 18, Legacy Rep: 10
    Location: Cebu

    standman Junior Member

    FRP, very close to the design of small boat. I thought too the wide chines would cause slamming but the much deeper kiln actually push water to those chines and somehow acts like a suspension and allows to plane quicker.
     
  7. tonipu
    Joined: Dec 2014
    Posts: 175
    Likes: 11, Points: 18, Legacy Rep: 10
    Location: croatia

    tonipu Senior Member

    With 3 blades 55%
    Some cavitation problem and strenght
     

    Attached Files:

  8. tonipu
    Joined: Dec 2014
    Posts: 175
    Likes: 11, Points: 18, Legacy Rep: 10
    Location: croatia

    tonipu Senior Member

    4 blades 67% blade area
     

    Attached Files:

  9. tonipu
    Joined: Dec 2014
    Posts: 175
    Likes: 11, Points: 18, Legacy Rep: 10
    Location: croatia

    tonipu Senior Member

    4 blades area 75%
     

    Attached Files:

  10. tonipu
    Joined: Dec 2014
    Posts: 175
    Likes: 11, Points: 18, Legacy Rep: 10
    Location: croatia

    tonipu Senior Member

    i will go with 2.5 shaft, and if you can find with aisi630
     
  11. tonipu
    Joined: Dec 2014
    Posts: 175
    Likes: 11, Points: 18, Legacy Rep: 10
    Location: croatia

    tonipu Senior Member

    and 4 blade prop
     
  12. tonipu
    Joined: Dec 2014
    Posts: 175
    Likes: 11, Points: 18, Legacy Rep: 10
    Location: croatia

    tonipu Senior Member

    from the strut to propeller is better to go out, no more than a shaft diameter
     
  13. tonipu
    Joined: Dec 2014
    Posts: 175
    Likes: 11, Points: 18, Legacy Rep: 10
    Location: croatia

    tonipu Senior Member

    Prop and strut
     

    Attached Files:

  14. standman
    Joined: Mar 2015
    Posts: 51
    Likes: 7, Points: 18, Legacy Rep: 10
    Location: Cebu

    standman Junior Member

    First, thank you for the input. I'm not familiar with aisi 630 but a google check says it is equivalent to stainless 304 which is what I will use. I wonder why the prop maker gave me those specs? Is it because they are confident with their material? ( Hypothetical) As for the strut to propeller, anything beyond shaft diameter cause vibration? TIA BTW, How's your boat coming along?
     

  15. tonipu
    Joined: Dec 2014
    Posts: 175
    Likes: 11, Points: 18, Legacy Rep: 10
    Location: croatia

    tonipu Senior Member

    it is about 3 times stronger than 304
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.