Quote:
Originally Posted by Reaper' date='19 April 2010 - 12:04 PM
Hi,
Is anyone able to point me in the direction of a reliable resource that will help me work out how powerful an engine a displacement vessel will require?
I'm interested to work out what an appropriate replacement engine would be for a yacht (monohull) in terms of horsepower/kilowatts, given its LWL, beam and displacement. Going by the previous engine may not be a good option in case it was underpowered to start with (unless it is the original in a production yacht, then maybe it'd be ok).
Thanks!
|
"In the case of displacement yachts, a motor performance of approximately. 2.5 kW pro 1 metric ton displacement is required, in order to be able to attain the theoretical hull speed. If this speed is to be exceeded by 5%, at least 25% more performance is required (approx. 3 kW / 1 t). 90% of the hull speed is achieved with a drive performance of 1.5 kW / 1t (41%). The performance requirement increases enormously, when reaching and exceeding the hull speed. It therefore does not make much sense to attain 100%, in the case of a sailing yacht using a motor, if 90% hull speed can be attained with 50% performance. If, in spite of this, a sailing yacht has a motor performance of approximately 3 to 4 kW / 1 t displacement, this is because the high performance is required in the lower speed range to be able to manoeuvre in bad weather. This can be designated as „extra manoeuvring power”."
I found this info*
here under point 8. To my understanding these numbers apply to a traditional Diesel engine, even though this site is dealing with diesel-electrical engines.
Almost always older yachts are underpowered regarding today's expectations and needs as in older days the engines of
sailing yachts were only auxiliary engines used for manoeuvering and in dead calms. That is different today - no matter what, today's yachts must reach hull speed also under conditions of beating against wind and sea following the philosophy "If the wind does not bring you home in time, the engine will. No matter what". But that is off topic here...
Uwe
SY Aquaria