Choosing main engine and propeller

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.

 

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.

 

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?

 

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

 

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"