Brainstorming! Suggestions to propel a FRP Trawler

Discussion in 'Propulsion' started by SixMadrid, Apr 22, 2013.

  1. SixMadrid
    Joined: Apr 2013
    Posts: 31
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Madrid

    SixMadrid Marine Engineer UPM (Mad)

    Brainstorming!


    I am gathering ideas to propel a new beam trawler made of FRP with :

    Displacement 577 ton

    Length wl - 32.7 m

    Beam wl - 7.8 m

    Draft - 3.5 m

    Block coefficient - 0.63

    Think about how to apply new technologies...

    Thanks!
     
    Last edited: Apr 23, 2013
  2. Adler
    Joined: Jan 2010
    Posts: 162
    Likes: 14, Points: 18, Legacy Rep: 139
    Location: PIRAEUS - GREECE

    Adler Senior Member

    Propeller Part Of The Project

    An estimation of your needs with the referred hull regarding a conventional propeller is attached.
    If that ship will work as trawler [towing nets at 2.5-3 knots] you have to note that using a fixed pitch propeller
    you will not reach more than 10.5 knots at top speed without to be involved cavitation issues at trawling speed or the opposite.

    I think that you have to study a solution with Controllable Pitch Propeller System
    before to proceed to the energy plan.

    How you think about that?
     

    Attached Files:

  3. SixMadrid
    Joined: Apr 2013
    Posts: 31
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Madrid

    SixMadrid Marine Engineer UPM (Mad)

  4. Adler
    Joined: Jan 2010
    Posts: 162
    Likes: 14, Points: 18, Legacy Rep: 139
    Location: PIRAEUS - GREECE

    Adler Senior Member

    Choice

    One or two propellers?
     
  5. SixMadrid
    Joined: Apr 2013
    Posts: 31
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Madrid

    SixMadrid Marine Engineer UPM (Mad)

    I try to compare the advantages and disadvantages about all the propulsion systems for this ship.

    Two propelers is another option.
     
  6. Adler
    Joined: Jan 2010
    Posts: 162
    Likes: 14, Points: 18, Legacy Rep: 139
    Location: PIRAEUS - GREECE

    Adler Senior Member

    Ducted Propeller Kaplan 37

    See the attached. One Propeller.
     

    Attached Files:

  7. Adler
    Joined: Jan 2010
    Posts: 162
    Likes: 14, Points: 18, Legacy Rep: 139
    Location: PIRAEUS - GREECE

    Adler Senior Member

    Notes

    According to the chosen displacement on Lwl 32.7m and the elementary speed of 10.5 knots the choice of One propeller will provide a remarkable increment to the propeller's volume plus the volume of the duct structure.
    A such kind of installation will modify extensively the aft part of the hull regarding to smooth the flow into the suction of the Duct.

    Maybe you have to exam and install two propellers [ probably ducted ].
    That option has important benefits.
    Safety
    Better row into the ducts' and propellers' suction.
    Improved Manoeuvring [ compared to one ducted propeller ]
    Low Maintenance Machinery Cost.
     
  8. SixMadrid
    Joined: Apr 2013
    Posts: 31
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Madrid

    SixMadrid Marine Engineer UPM (Mad)

    So If we want to reach at 13 knots, is the best solution a Controllable Pitch Propeller System?? Any other system?

    About the reports... how do you get it?? I mean, is it with a specific software? can you share that?

    thanks!
     
  9. rxcomposite
    Joined: Jan 2005
    Posts: 2,100
    Likes: 226, Points: 63, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    Disp=L * B * T * Cb * 1.025

    32.7 * 7.8 * 3.5 * 0.48 * 1.025 = 439.2 tonnes

    Typo Error?
     
  10. Adler
    Joined: Jan 2010
    Posts: 162
    Likes: 14, Points: 18, Legacy Rep: 139
    Location: PIRAEUS - GREECE

    Adler Senior Member

    ???

    If you want to reach 13 knots you have to choose two Fixed pitch propellers without acceleration Duct.
    The one Ducted Controllable Pitch Propeller system could be useful on that case but limited to 12.2 knots.
    The software is officially purchased from Hydrocomp and any sharing is prohibited.
    The note from rxcomposite regarding your calculations should be answered.
    I had already found the paradox when I did the input process but I ignored the
    Cb value giving weight to preferable method of you in your previous thread
    where you often liked to calculate the trawler concept on what you need in
    displacement magnitude basis. [Cb 0.646]
    On that basis I supposed that Cb and not the Displacement value was your error.

    Anyway when you ready regarding the hull dimensions I can help you regarding to calculate few options
    of your propulsion concept and to have a design drawing of the propeller and duct which you will decide to be applied on.

    We remain to see your thoughts.
     
  11. SixMadrid
    Joined: Apr 2013
    Posts: 31
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Madrid

    SixMadrid Marine Engineer UPM (Mad)

    Yes! Typo, sorry...

    Block coeficient 0,63

    -edited-
     
  12. SixMadrid
    Joined: Apr 2013
    Posts: 31
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Madrid

    SixMadrid Marine Engineer UPM (Mad)

    are two fixed pitch proppeler the best option to get 13 knots in this kind of boats? explain me more, please
     
  13. Adler
    Joined: Jan 2010
    Posts: 162
    Likes: 14, Points: 18, Legacy Rep: 139
    Location: PIRAEUS - GREECE

    Adler Senior Member

    Plan

    If you install Acceleration Ducts on the propellers you will never exceed 12.3 knots because of them first. The acceleration Duct improves the thrust
    [ and the fuel consumption at trawling loads ]
    but when the speed increases more than 12 knots the produced drag on them suspends the increasing of speed.
    Over that even if you don't install the Ducts and choose Fixed Pitch Propellers on that hull with Cb value at 0.64 and Lwl 32.7m
    you will need a huge amount of power [ 2700 mHp ] and the propellers over the speed of 12.2 knots will suffer by cavitation issues. Main reason is that they
    operate at full power and at two different speeds Cruising [12.2 kts] and Trawiling [3.7 kts] with the same pitch.

    A suitable solution if you insist to cruise at 13 knots is to install two Controllable Pitch Propellers without ducts that will be driven by two engines 1350 mHp each.
    Controllable Pitch Proppeller's Dia 1820mm and Gearbox Reduction Ratio 3,4.

    Is that good for your budget ? CPP is much more expensive than FPP.

    Note: A Ship at Lwl at 43m the same Beam/Draught and Displacement of 577t needs only 1600mHp Totally to exceed 13 kts with two Fixed Pitch Propellers
    without cavitation issues on them.
    If you consider the market fuel price , the difference on the installed propulsion power consumption and the difference in cost between
    Fixed pitch Propellers and Controllable Propellers System then the adding cost to build an elongated hull will be amortizable in two working years at Sea.
     
  14. rxcomposite
    Joined: Jan 2005
    Posts: 2,100
    Likes: 226, Points: 63, Legacy Rep: 1110
    Location: Philippines

    rxcomposite Senior Member

    Fn 0.30 to 0.33 is a good number for least wavemaking resistance but at Cb 0.63, you are a little bit of the top of the W & G optimum Cb. Series 63 hulls also will not fit so you will be designing around the Seres 60 lines.

    If you wanted ideas on tweaking the propulsion, here are some approach with the corresponding merits. I am sure Adler is well qualified to discuss these.

    IMO, I will exploit the single prop, big wheels, low rpm, low Bp approach. You have a deep draught and indicates the most potential for improvements.
     

    Attached Files:


  15. Adler
    Joined: Jan 2010
    Posts: 162
    Likes: 14, Points: 18, Legacy Rep: 139
    Location: PIRAEUS - GREECE

    Adler Senior Member

    Info and Papers

    Dear SixMadrid,

    Please find attached few specific info and papers that could be relevant to your project plan issues.

    We are waiting your next input/comments.
     

    Attached Files:

    1 person likes this.
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.