Power/Resistance Calculation for Planing V-Hull & Fuel/Engine Required

The power is a very rough estimate and as I said it may be possible to halve it.

A big modern diesel consume less than 200 g/kW/h and even 160 g/kW/h is possible (over 50% efficiency). 4000 kg/h is about 4800 l/h.

Joakim

 

Hmmmm.... It is becoming a big mess in this site with the units, indeed. I had read l/h instead of kg/h when reading your data.
No problem, it means that we both have used the same fuel consumption per HP.

 

I gave you the expected efficiency in post #3.

Rick W

 

If this is for a fast attack boat I think you need to consider that it will actually operate in two modes. The first is long distance range at some optimal cruising speed, the second is in attack mode running at or near full speed. Since you really can't carry enough fuel to operate at high speed all of the time the trade off is to take longer getting to the expected operational location while keeping the ability to operate at high speeds when necessary. In addition if this is a proposed ship for the US fleet, then keep in mind that under way refueling is a possability as well.

I stole this from Trinity Yachts Concept page, but it is a semi-displacement jet yacht carrying a lot more ammenities than you would need with a max speed of 27.5 kn, and a max range of 4,000nm at 10kn. http://www.trinityyachts.com/168hssdwaterjetmy.asp The ship leaves the dock with 22,000 gallons of fuel, so that works out to be about 5.25 gallons per mile. Which is pretty much in line with what you can expect from such a large vessel.

 

guys I've found a savitsky spreadsheet, can any of have a look, I don't konw if it is a good one http://www.hawaii-marine.com/templates/Products/Savitsky/description.htm

Regards,
CAS

 

Why not plug your numbers in here:
http://illustrations.marin.ntnu.no/hydrodynamics/resistance/planing/index.html
It is free.

Rick W

 

Joakim
I am being picky but they should be kWh not kW when you are referring to energy. I know you made a simple mistake but given the knowledge displayed by some here they may not realise what you meant.

A little Bukh diesel I had years ago was specified to get 186g/kWh and my estimates at the time indicated that this was close to what I achieved.

Rick W

 

You are right and I corrected that to my original post. I think it is very important to be careful about units, but wrote too fast.

Joakim

 

Have you heard of Project 305 , a boat built at Devonport Dockyard in Plymouth for the Aga Khan which must be a nightmare to build as the speed requirements for this craft have been extremely problematic .

http://www.telegraph.co.uk/news/uknews/1568954/Aga-Khan's-andpound100m-boat-after-Blue-Riband-title.html

 

Yeah, I've read about it few months ago, and that fire incident in the engine room during the trials had struck me. That accident, plus the subsequent change of propulsion type is not a good sign, imho. Applying patches (and this one is big) to a new project is never a good sign to me. They are stretching to the technological limits the structural and propulsive requirements of the ship and it looks to me that it's birth and future life will not be easy.

I have a headache and some fever so all glasses look half-empty to me today.