# Speed Optimization - need to calculate the optimum speed for a given voyage

Discussion in 'Boat Design' started by Chris Pap, Jun 10, 2015.

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### Chris PapJunior Member

Hello,

I would like to ask what are the factors that we should take into account for speed optimization, and what kind of data do we need, in order to conduct that kind of optimization?

Thank you,
Chris Pap.

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### gonzoSenior Member

Ever possible factor has to be taken into consideration. For example, all the hydrodynamic and aerodynamic calculations, engine power/gear combinations, total displacement (light, medium and heavy), etc. Also, you need to define what you mean by "speed optimization". Do you want maximum speed, maximum range, minimum fuel per hour?

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### Chris PapJunior Member

By speed optimization I mean minimum fuel per voyage. So I need to calculate the optimum speed for a given voyage. Still need to consider all these parameters? And if this is the case which are the dominant ones?

Thank you
Chris Pap.

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### rxcompositeSenior Member

What type of vessel are you optimizing for speed? Barges at 4 to 8 knots can be optimized for speed, fast cargo vessel running at 25 knots can be optimized also. Compromises are tugboats and military vessels.

What is the size of your boat?

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### daiquiriEngineering and Design

Are you:
1) optimizing the speed of a given and non-modifiable vessel
2) optimizing the vessel design for a given speed?
3) optimizing the vessel design and the speed for a given... something?

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### Chris PapJunior Member

Dear rxcomposite,

Right now I am studying about cargo ships. How exactly can I optimize the speed for a given route. So I do not have a standard size. It mat lie from 15000 tonnes DWT to 300000 tonnes DWT. It may be bulk carriers or tankers etc.

Dear Daquiri,

It is the option 1.
As I previously mentioned I am studying about cargo ships. More specifically about energy efficiency at operation.

Finally, due to the fact that I am conducting a small study and not a paid project I would like to start from scratch and create a simple tool that can do that speed optimization with the basic components. That is why I need the parameters to put in and hence the data that I should collect. And from a small research from google I did not find anything very useful.

Thank you very much,
Chris Pap.

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### BertKuSenior Member

Chris, That is no easy task. You will have to have in your calculations, what is the influence of the headwind or tailwind on your ship, also the currents, in favor or against you, not to forget the wave heights, flat sea or 6 meter waves. Good luck with your studies. Bert

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### rxcompositeSenior Member

Chris, for a start, you can check the preliminary group of ship you want to evaluate as shown in the diagram. Then you can consult Principles of Naval Architecture for the ratios and coefficients of the type you have chosen. Go to Lindblad and Todd tabulation. For Watson and Gilfilan line you have to consult Watson's Practical Ship Design.

After that, you have to study Resistance and Powering of Ships to get a grasp on the approach. Hull shape and resistance is different from powering.

Lastly google "Ship Design for Efficiency and Economy". My file wont upload.

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### baeckmoHydrodynamics

"Minimum fuel per voyage...." is easy, go as slow as possible! But that is probably NOT what you are searching, so there must be other constraints as well. Crew endurance, cargo quality, delivery time scedule; the list goes on. The OPTIMUM speed is most certainly NOT the minimum fuel speed.

Fuel costs go down with speed, but other costs like manning et c increase with time at sea. The cargo has a value that is costing an interest rate and locking an investment for your client during the transport, all of which is influencing the earning capacity of the vessel in total.

So, in reality, it is the earning capacity over a time period, not the single fuel bill that is interesting. I guess that is why you won't find any google answers; it is simply "the wrong question"!

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Can't say it any better than that...

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### rxcompositeSenior Member

Well. he did say in the second post that it is a cargo ship for a given route and did include the possibility of a bulk carrier or a tanker.

As for the manning, the international manning regulation will take care of that.

Still, it is like finding a ball in a ballpark. He needs to be more specific and unless he is an NA or a ship designer, he will find it very challenging to learn he/she has very limited knowledge of.

Trade routes- will it be passing Suez Canal, Panama, or any other small canals?
Cargo ships- Perishables or containers?
Bulk- Grain, Ore, or oil?

The first approximation will be the general size of the ship limited by the trade routes.
The second approximation will be the optimum shape based on the type of cargo.
Then choice of power- limited by depth and choice of engine.

The second set of criteria would be economic criteria which is;

Operating cost
Daily running cost-crew, provisions, store
Voyage cost-FO, FW, Pilotage, port and canal charges, port expenses
Cargo handling cost
Maintenance and repair

I think there is a special division in shipbuilding/design called Ship Economics.

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### Chris PapJunior Member

To be more specific I need to say that I do not have a standard ship at a standard route.

So I need to create a general tool that will take as inputs all the economic criteria (the operational costs of the ship, the
RFR etc.), and also the ships parameters (for example sea trials maybe to associate the speed and rpm with the power).

Regarding all these, there are no design criteria because the ship will be given and it will be non-modifiable.

Moreover the phrase "Minimum fuel per voyage...." is wrong and I am very sorry. I meant "Minimum cost per voyage..".

Finally, we won't have a route optimization. The path will be standard. So if I receive the weather as input it will be a small approximation of added resistance in order to add it to power required from sea trials.

So that is the outline of the tool, and I'm trying to gather all the parameters (at least to add the to an excel file to start make some very basic calculations).

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### daiquiriEngineering and Design

The real pain will IMO arrive if you try to include the weather forecasts along the route. That's where the statistics and probability will come into play.
For example, say that the forecast indicates a possibility of a strong and nasty storm along the route:
- Heading straight into it increases the probability of damage or loss of the ship with all the goods aboard, and imply a consequent increase of insurance costs. Hence, that choice puts you at the local maximum of the cost function.
- Going all the way around it increases all the other costs of the trip (fuel, crew hours, penalties for delayed delivery of goods etc.). Hence, this choice puts you at another local maximum of the cost function (probably lower than the previous one).
Therefore, in between the two local extremes exists a route which will place you at the local minimum of the cost function. How to find it? That will be the tricky part.

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### BertKuSenior Member

Ok if that is the case, should you make a software program which has all the parameters. like all the members has suggested, both extremes like Daiqairi suggested, you may have a winner there, which you could sell to many shipping lines. over and over again. However, you have a hell of a task on what will be the impact on the final cost, with tornado's or beautiful weather with no waves. If you can in your software come up with a practical sliding scale, you definitely will have a winner.

You remind me to a staff member who asked me whether he could keep the computer, if he wrote a good software package for our division. When he was finished he resigned and parallel he wrote a software package for outside company managements to see for how long and at what cost a staff member was making a private call. He could prove to the buyer that they would get a financial gain.
After 1 year he bought his first Mercedes cash and after 3 years he had a well oiled company with 7 Mercedes Benz cars all bought for cash, not on credit. That happened 25 years ago.
Moral of the story, get as many parameters written down and then judge the impact of those parameters.
Again , good luck. Please do offer me a ride when you buy your first Mercedes Benz 500. Bert

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### DCockeySenior Member

"Minimum cost per voyage" or "Maximum profit per year"?

Minimum cost per voyage yields maximum profit only if the revenue per year is independent of how long the voyages take. If revenue per year is proportional to the number of voyages per year then maximum profit will result with the vessel operating at a speed higher than the minimum cost per voyage speed.

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