Choosing main engine and propeller

Discussion in 'Boat Design' started by Furkan, Dec 14, 2021.

  1. Furkan
    Joined: Nov 2020
    Posts: 6
    Likes: 0, Points: 1
    Location: Turkey

    Furkan Junior Member

    Hello all,

    Please forgive my ignorance and try your best to answer my question. Accorgding to what and what kind of data we choose propulsion and main engines for our vessel? How do we do the required calculations and over what sort of concepts do we think?

    Thanks.
     
  2. Olav
    Joined: Dec 2003
    Posts: 334
    Likes: 49, Points: 38, Legacy Rep: 460
    Location: Filia pulchra Lubecæ

    Olav naval architect

    Furkan,

    that's a very broad question and one that's not really possible to answer without giving a complete lecture in naval architecture/marine engineering since all decisions on the propulsion system are related with heaps of other aspects of the vessel's design...

    Think of speed and thrust requirements, draught limitations, safety, reliability/redundancy, maneuverability and other operational aspects, weight concerns, availability of components and spare parts, initial and operational cost constraints, fuel consumption, system integration matters, automation, rules and regulations that must be adhered to, etc. etc.

    Maybe you can narrow your question down to something a bit more specific.
     
    bajansailor likes this.
  3. BlueBell
    Joined: May 2017
    Posts: 1,969
    Likes: 581, Points: 113
    Location: Victoria BC Canada

    BlueBell . . . . .

    Hello Furkan,

    That's a complicated question you ask.
    How big is the boat and how fast do you expect it to go, steady, cruising speed?
    Max speed?
    What is the use of the boat?
    Drag. How much resistance is offered at speed.
    You can measure this by towing the boat with a scale in line and measure the drag.
    I don't know that you can calculate it.

    Do you have any pictures or plans you could show us?
     
  4. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    I think that target speed and vessel resistance are the first two parameters to start with.
     

  5. Barry
    Joined: Mar 2002
    Posts: 1,600
    Likes: 347, Points: 83, Legacy Rep: 158

    Barry Senior Member

    A small boat with a low cost,
    You can compare deadrise, weight, type of service, target speed with others in the market. You can get close enough. Thinking recreational vessels here.

    A large vessel, which costs a lot of money, and it sounds like this may be one, "what kind of data we choose propulsion and main engines for our vessel", with a large cost outlay, you would be unable to do the calculations yourself
    if you are not a Naval Architect. Too many variables and if the cost for" propulsion and main engines" is large, you risk over spending with more hp than you need or underspending and not meeting required targets, weight, speed
    optimized fuel costs and running the additional machinery. Assume the PERFECT engine, (defined as meeting the best optimization for your requirements) is 2000hp. Consider that you guess or take the advice of non-NA's, and put in 1600 hp. You will not meet your operating requirements. What is the cost of this to you? OR alternatively, you take non-professional advice and put in 2500 hp. The cost could be in the hundreds of thousands of dollars and perhaps not meet fuel efficiency requirements.

    Your "cheapest" bet on a large vessel is to supply a NA with the drawings, weight, SOR, expected wave height, range etc etc etc etc, and pay to get a "designed" propulsion system.

    As per Olav above
    "not really possible to answer without giving a complete lecture in naval architecture/marine engineering since all decisions on the propulsion system are related with heaps of other aspects of the vessel's design..."

    It would take much more than a complete lecture for YOU to develop the correct hp requirement

    If you needed brain surgery, would you go to a forum or go to a trained doctor with 12 years of education??? Not meant to be flippant, but if it is a large vessel and you want a good outcome, "write the check to a NA"
     
    Last edited: Dec 19, 2021
    bajansailor and DogCavalry like this.
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