dkm
Well-Known Member
what does \'cruising speed\' mean?
is it the most fuel efficient speed, or something else?
is it the most fuel efficient speed, or something else?
what does 'cruising speed' mean?
- Thread starter dkm
- Start date
Whitelighter
Well-Known Member
Re: what does \'cruising speed\' mean?
I have always taken it to mean the speed that the boat is most comfortable at and therefor the speed likely to be easily maintained over a longer passage.
You arent going to go everywhere at wot because tides, seastate or general comfort will dictate that for more than about 20 minutes its very tiring on the helm and crew.
You will normally find cruising speed is about 70% of max speed.
I have always taken it to mean the speed that the boat is most comfortable at and therefor the speed likely to be easily maintained over a longer passage.
You arent going to go everywhere at wot because tides, seastate or general comfort will dictate that for more than about 20 minutes its very tiring on the helm and crew.
You will normally find cruising speed is about 70% of max speed.
DavidJ
Well-Known Member
Re: what does \'cruising speed\' mean?
I believe it to be just after you have got on the plane and nicely flattened out. For me thats about 20-22 knots although my top speed is 32 knots (2x KAD43 on an S37)
I believe it to be just after you have got on the plane and nicely flattened out. For me thats about 20-22 knots although my top speed is 32 knots (2x KAD43 on an S37)
jimmy_the_builder
Well-Known Member
Re: what does \'cruising speed\' mean?
Max range planing speed, isn't it?
Cheers
Jimmy
Max range planing speed, isn't it?
Cheers
Jimmy
dkm
Well-Known Member
Re: what does \'cruising speed\' mean?
I've heard it described as max revs minus about 2-300 rpm. Apparently this is the most fuel efficient
I've heard it described as max revs minus about 2-300 rpm. Apparently this is the most fuel efficient
DAKA
Well-Known Member
Re: what does \'cruising speed\' mean?
I think that is the old days when max revs were 1500-2000
My engines rev to 4000 rpm, yes I could travel sustained distance at 3800 rpm 26/27 knots so that could be described as max cruising speed.
I prefer to reduce revs to 3400 as that is the most economic cruising speed 24/25 knots
If I reduce to 20 knots then my engines are less economic (slightly)
in answer to your question , I dont know either
I think that is the old days when max revs were 1500-2000
My engines rev to 4000 rpm, yes I could travel sustained distance at 3800 rpm 26/27 knots so that could be described as max cruising speed.
I prefer to reduce revs to 3400 as that is the most economic cruising speed 24/25 knots
If I reduce to 20 knots then my engines are less economic (slightly)
in answer to your question , I dont know either
MapisM
Well-Known Member
Re: what does \'cruising speed\' mean?
[ QUOTE ]
Apparently this is the most fuel efficient
[/ QUOTE ]No way. The most fuel efficient speed for any boat of any size, bar none, is the hull speed.
Oh, and the quick reply to your question is 'nothing'.
[ QUOTE ]
Apparently this is the most fuel efficient
[/ QUOTE ]No way. The most fuel efficient speed for any boat of any size, bar none, is the hull speed.
Oh, and the quick reply to your question is 'nothing'.
Chris_d
Well-Known Member
Re: what does \'cruising speed\' mean?
Thats Volvos advice for the maximum engine speed for cruising. Your actual cruising speed will depend on your hull type, mechanical sympathy, acceptable fuel consumption or size of wallet and sea conditions, so could be anything from 5-35knts.
Thats Volvos advice for the maximum engine speed for cruising. Your actual cruising speed will depend on your hull type, mechanical sympathy, acceptable fuel consumption or size of wallet and sea conditions, so could be anything from 5-35knts.
[2068]
...
Re: what does \'cruising speed\' mean?
A speed where you are making sensible progress, and both the engines and hull seem happy to continue all day.
dv.
A speed where you are making sensible progress, and both the engines and hull seem happy to continue all day.
dv.
realslimshady
Well-Known Member
Re: what does \'cruising speed\' mean?
[ QUOTE ]
A speed where you are making sensible progress, and both the engines and hull seem happy to continue all day.
dv.
[/ QUOTE ]
i.e. the speed you're cruising at.........
[ QUOTE ]
A speed where you are making sensible progress, and both the engines and hull seem happy to continue all day.
dv.
[/ QUOTE ]
i.e. the speed you're cruising at.........
dkm
Well-Known Member
Re: what does \'cruising speed\' mean?
Just found this on volvo website;
http://www.volvo.com/volvopenta/uk/en-gb...conomically.htm
Seems like the answer is just above planing speed
Just found this on volvo website;
http://www.volvo.com/volvopenta/uk/en-gb...conomically.htm
Seems like the answer is just above planing speed
mm1
Well-Known Member
Re: what does \'cruising speed\' mean?
very helpfull sir keep up the good work, regards m m 1.
very helpfull sir keep up the good work, regards m m 1.
colingr
Well-Known Member
Re: what does \'cruising speed\' mean?
Can't agree I'm afraid. Doesn't apply when on the plane.
Can't agree I'm afraid. Doesn't apply when on the plane.
nonitoo
Well-Known Member
Re: what does \'cruising speed\' mean?
My gut feeling would be that whatever speed just on the plane is would be the most comfortable and efficient (other than max displacement speed of course).
In my case max displacement gives approximate values of 6kts @ 2ltr/hr and a comfortable cruising planing speed of 20 kts @ 22ltr/hr.
If I go to WOT I will achieve 28 kts consuming, according to the engine performance figures, 46ltr/hr. Needless to say I have never tried this because
a. It's very uncomfortable in anything other than a flat calm
b. My wallet hurts !!
Tom
Tom
My gut feeling would be that whatever speed just on the plane is would be the most comfortable and efficient (other than max displacement speed of course).
In my case max displacement gives approximate values of 6kts @ 2ltr/hr and a comfortable cruising planing speed of 20 kts @ 22ltr/hr.
If I go to WOT I will achieve 28 kts consuming, according to the engine performance figures, 46ltr/hr. Needless to say I have never tried this because
a. It's very uncomfortable in anything other than a flat calm
b. My wallet hurts !!
Tom
Tom
mm1
Well-Known Member
Re: what does \'cruising speed\' mean?
Hi yes i think that is about right,just above planing speed is normally the most frugal,however i tend to favour 2 to300 rpm of wot as my best cruising speed,it will vary from boat to boat,you do get a feel when the boat is running good regards m m 1.
Hi yes i think that is about right,just above planing speed is normally the most frugal,however i tend to favour 2 to300 rpm of wot as my best cruising speed,it will vary from boat to boat,you do get a feel when the boat is running good regards m m 1.
gjgm
Well-Known Member
Re: what does \'cruising speed\' mean?
anything over 40knots, isnt it? The rest is sailing, I think. /forums/images/graemlins/grin.gif
anything over 40knots, isnt it? The rest is sailing, I think. /forums/images/graemlins/grin.gif
Sammo
Well-Known Member
Re: what does \'cruising speed\' mean?
If your looking for most economical speed then anything below the hull speed before you start to climb the hump…..
For cruising speed get over the hump and onto the plane then find a comfortable speed ….the boat will tell you what speed it likes…..low noise, vibration ect…
….
If your looking for most economical speed then anything below the hull speed before you start to climb the hump…..
For cruising speed get over the hump and onto the plane then find a comfortable speed ….the boat will tell you what speed it likes…..low noise, vibration ect…
….
MapisM
Well-Known Member
Glad to serve!
I guess from your sarcastic reply that you read my post as ironic, whilst it wasn't.
First of all, 'hull speed' is commonly used to define the displacement speed of a given hull, and that's what I meant - just in case you thought I was joking. Secondly, when I said that cruising speed means nothing, I also said it was a 'quick reply'.
There are in fact many different possible answers, each of them correct:
1) if (as Volvo suggests in the above linked site) you assume cruising speed=economy speed, then it's the displacement speed. Mind, it is not - as Volvo says - the speed 'just above the planing threshold'.
2) If by cruising speed you mean the max constant speed sustainable for long cruises, that depends not only on the hull, but also on the engines. Max rpm minus 200/300, or minus 10%, are rules of thumb frequently used. For boats with continuous unrestricted duty engines (which are indeed very rare, when talking about pleasure boats), that's the same as max speed.
3) If you mean the best compromise between economy and speed, this is usually 'just above the planing threshold', obviously for a planing boat.
4) Last but not least, as anyone with some offshore cruising experience well know, quite often the cruising speed is just what the sea conditions allow for a given boat.
Hoping to have been - if not helpful - at least clearer.
PS for jokaboat: I guess you didn't agree because you also couldn't see what I meant - does the above sound more acceptable now?
I guess from your sarcastic reply that you read my post as ironic, whilst it wasn't.
First of all, 'hull speed' is commonly used to define the displacement speed of a given hull, and that's what I meant - just in case you thought I was joking. Secondly, when I said that cruising speed means nothing, I also said it was a 'quick reply'.
There are in fact many different possible answers, each of them correct:
1) if (as Volvo suggests in the above linked site) you assume cruising speed=economy speed, then it's the displacement speed. Mind, it is not - as Volvo says - the speed 'just above the planing threshold'.
2) If by cruising speed you mean the max constant speed sustainable for long cruises, that depends not only on the hull, but also on the engines. Max rpm minus 200/300, or minus 10%, are rules of thumb frequently used. For boats with continuous unrestricted duty engines (which are indeed very rare, when talking about pleasure boats), that's the same as max speed.
3) If you mean the best compromise between economy and speed, this is usually 'just above the planing threshold', obviously for a planing boat.
4) Last but not least, as anyone with some offshore cruising experience well know, quite often the cruising speed is just what the sea conditions allow for a given boat.
Hoping to have been - if not helpful - at least clearer.
PS for jokaboat: I guess you didn't agree because you also couldn't see what I meant - does the above sound more acceptable now?
Its_Only_Money
Well-Known Member
Re: Glad to serve!
My petrol Fairline Sprint engine runs horribly inefficiently at hull speed so although the hull resistance is optimal, my fuel consumption is not. Just fully planing (22-23kts) gives better economy as although the hull is running slightly less efficiently than at Hull speed, the engine is running much more efficiently and this wins out in overall economy.
My petrol Fairline Sprint engine runs horribly inefficiently at hull speed so although the hull resistance is optimal, my fuel consumption is not. Just fully planing (22-23kts) gives better economy as although the hull is running slightly less efficiently than at Hull speed, the engine is running much more efficiently and this wins out in overall economy.
oceanfroggie
Well-Known Member
Re: what does \'cruising speed\' mean?
It's difficult to generalise, but if one had to, then cruising speed is often roughly 75% of available engine power assuming the sea state is suitable.
As others have said the boat should be planing well and comfortable on the sea but not laboured or stressed.
It's difficult to generalise, but if one had to, then cruising speed is often roughly 75% of available engine power assuming the sea state is suitable.
As others have said the boat should be planing well and comfortable on the sea but not laboured or stressed.
