alec
New member
What does the team think.
Say on a full tide sail 10%, 20% or more ? or not much at all ?
Say on a full tide sail 10%, 20% or more ? or not much at all ?
Motoring v Motorsailing, Do you save much on fuel ?
- Thread starter alec
- Start date
jonathankent
New member
Depends on the wind direction. If its on the bow, then having the sail up is likely to just add more resistance and slow you down/use more fuel. If however, the wind was anywhere else then the sail is going to give some extra drive and therefore should reduce the amount of fuel used.
I've always understood the idea of having the main up is to reduce the roll and balance the yacht better when under engine, so would make for a more comfortable ride.
If you've got wind... sail - I've found yachts will go alot faster under sail than engine anyhow.
All IMHO of course.
I've always understood the idea of having the main up is to reduce the roll and balance the yacht better when under engine, so would make for a more comfortable ride.
If you've got wind... sail - I've found yachts will go alot faster under sail than engine anyhow.
All IMHO of course.
oldharry
Well-known member
<<yachts will go alot faster under sail than engine anyhow.>>
Depends on the size of the engine. Most yachts nowadays are engined to be able to reach waterline speed without difficulty. I have often found that in lighter weather when the sails are not providing much drive, using the engine at a low throttle setting will often enable the boat to keep up a decent speed while using very little fuel. Useful if a tidal 'gate' has to be passed before a certain time.
Depends on the size of the engine. Most yachts nowadays are engined to be able to reach waterline speed without difficulty. I have often found that in lighter weather when the sails are not providing much drive, using the engine at a low throttle setting will often enable the boat to keep up a decent speed while using very little fuel. Useful if a tidal 'gate' has to be passed before a certain time.
bluedragon
Active member
Agree with this. I'm not sure a tightly sheeted main that is not drawing is doing anything, but last week I was motoring into a building sea and headwind to clear a headland and its overfalls, and when we could bear-away a little bit unrolled a scrap of genoa (something a bit more than storm jib, but less than working jib)...went off like a rocket and could drop the throttle right back.
Lizzie_B
New member
I generally only get the sails out when motoring if they give me about an extra 1/2 to 1knot.
My engines comfortable cruising speed is about 6.5 knots at approx 0.7 US gal per hour.
Assuming actually on a point of sail not head to wind when I get the sails out I expect to see 7 plus.
I frequently ease the throttle down to check that I'm not sailing that fast anyway.
My engines comfortable cruising speed is about 6.5 knots at approx 0.7 US gal per hour.
Assuming actually on a point of sail not head to wind when I get the sails out I expect to see 7 plus.
I frequently ease the throttle down to check that I'm not sailing that fast anyway.
Malcb
Active member
As has been said, depends on wind direction.
When I came back from the West Country this year, because of the weather I had to do Brixham to Chi in one go (singlehanded). The wind was F6 gusting 7 NW. I needed to average at least 5 knots to get the tidal gates round Portland and then into the Solent (missed that one, too early). So I motor sailed with 2 reefs in the mainsail and no jib. I did better than planned, 5.3 knots over the ground. Fuel consumption, with a 10 hp engine, was just a tad over 1 litre per hour, for 100+ miles. Probably motoring alone I would have used 1.5 liters per hour at that speed.
When I came back from the West Country this year, because of the weather I had to do Brixham to Chi in one go (singlehanded). The wind was F6 gusting 7 NW. I needed to average at least 5 knots to get the tidal gates round Portland and then into the Solent (missed that one, too early). So I motor sailed with 2 reefs in the mainsail and no jib. I did better than planned, 5.3 knots over the ground. Fuel consumption, with a 10 hp engine, was just a tad over 1 litre per hour, for 100+ miles. Probably motoring alone I would have used 1.5 liters per hour at that speed.
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Anonymous
Guest
I practically always have the main up and gain at least 1/4 kt (usually much, much more) and reduce roll. When the wind is on the nose, to stop the main flogging I often take the boom well to windward with the traveller. I feel sure that any repeated flogging, even mild flogging, wears the sail but that's just my intuitive feeling which could be wrong - I have no evidence.
Richard10002
Well-known member
[ QUOTE ]
I practically always have the main up and gain at least 1/4 kt (usually much, much more) and reduce roll. When the wind is on the nose, to stop the main flogging I often take the boom well to windward with the traveller. I feel sure that any repeated flogging, even mild flogging, wears the sail but that's just my intuitive feeling which could be wrong - I have no evidence.
[/ QUOTE ]
Definitely reduces roll in most instances, and running the engine at lowish revs often gets us up from around 4 knots to 6 knots or so.
Convinced that any flapping or flogging costs money.
I practically always have the main up and gain at least 1/4 kt (usually much, much more) and reduce roll. When the wind is on the nose, to stop the main flogging I often take the boom well to windward with the traveller. I feel sure that any repeated flogging, even mild flogging, wears the sail but that's just my intuitive feeling which could be wrong - I have no evidence.
[/ QUOTE ]
Definitely reduces roll in most instances, and running the engine at lowish revs often gets us up from around 4 knots to 6 knots or so.
Convinced that any flapping or flogging costs money.
mortehoe
New member
Does it matter?
I sail when the wind is available for where I want to go. But sometimes there are either tidal gates which have to be achieved (Anglesey/Menai Strait) or I need to be able to point higher and so the engine is needed. (This is for local sailing ie EU)
Yanmar 1GM10 - Generally 3/4 litres per hour and over a year that amounts to 85 litres of motoring time averaged over the last 15 years. Sailing time average is currently down to 680 hours per year ....
I sail when the wind is available for where I want to go. But sometimes there are either tidal gates which have to be achieved (Anglesey/Menai Strait) or I need to be able to point higher and so the engine is needed. (This is for local sailing ie EU)
Yanmar 1GM10 - Generally 3/4 litres per hour and over a year that amounts to 85 litres of motoring time averaged over the last 15 years. Sailing time average is currently down to 680 hours per year ....
ccscott49
Active member
Re: Does it matter?
I own a motorsalier, my sails provide a generous fuel saving, un less the wind is right on the snotter! I have my sails up as much as possible and they do limit rolling. with a decent wind (f4-7) I can save huge amounts of fuel and easily run on one engine at 1200 rpm and manage 8.5 knots.
I own a motorsalier, my sails provide a generous fuel saving, un less the wind is right on the snotter! I have my sails up as much as possible and they do limit rolling. with a decent wind (f4-7) I can save huge amounts of fuel and easily run on one engine at 1200 rpm and manage 8.5 knots.
Amari
New member
I have read several times that motor sailing is bad for the engine because it has insufficient load. Not sure that I believe this dogma. BTW, I've also read this year (but sorry can't remember where) that it is best to have small engine working hard/high revs than larger engine at lower revs. Again, not sure I believe this. Larger engine = bigger prop = more in reserve aginst big sea/tide/wind, and surely it's petrol engines that 'enjoy' high revs whereas diesels OK running slowly
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Anonymous
Guest
That will attract varying opinions! Firstly, technology has changed. The old marine diesel was a slow-revving machine with a designed maximum power output in the mid 2000s RPM whereas more modern, lighter, diesels give maximum power in the early 3000s.
Diesels work by compressing the gas in the cylinder until it explodes spontaneously - the temperature of the gas rises due to compression and it just explodes without a spark. If the piston rings and valves don't make a good seal then the compression falls (especially at starting) causing poor starting and reduced power output. If you let the engine tick over or run at very light loads (e.g. less than 5% of the rated output in horsepower) then the cylinders can glaze and the rings can stick (causing a poor seal). Sometimes this can be rectified by running the engine at high output for a few hours but sometimes it needs to be stripped down.
You shouldn't run a diesel at full load continuously. Most manufacturers state a max output for a given time (e.g. 80% = continuous, 100% = one hour in every 24, 110% = 30 mins in every 24 hrs). If you are anywhere near using full power, it is worth checking with the manufacturer if the details are not to hand.
I like to run my Yanmar at 1800 RPM which in my system gives me 20 hp (my engine is 110 hp) so I am running just under 20% loading. I have not seen any signs of problems and have asked a couple of friends who are experienced diesel engineers to take a quick look, and they have confirmed that I am not causing a problem.
One final point, every so often it is sensible to test the engine at full power for at least half an hour, until the temperature has settled. Not only will it help to clean up any unburnt deposits it will show up any weakness in the cooling system. Better to find out near to base than when cruising miles away just after you've heard a gale warning!
Diesels work by compressing the gas in the cylinder until it explodes spontaneously - the temperature of the gas rises due to compression and it just explodes without a spark. If the piston rings and valves don't make a good seal then the compression falls (especially at starting) causing poor starting and reduced power output. If you let the engine tick over or run at very light loads (e.g. less than 5% of the rated output in horsepower) then the cylinders can glaze and the rings can stick (causing a poor seal). Sometimes this can be rectified by running the engine at high output for a few hours but sometimes it needs to be stripped down.
You shouldn't run a diesel at full load continuously. Most manufacturers state a max output for a given time (e.g. 80% = continuous, 100% = one hour in every 24, 110% = 30 mins in every 24 hrs). If you are anywhere near using full power, it is worth checking with the manufacturer if the details are not to hand.
I like to run my Yanmar at 1800 RPM which in my system gives me 20 hp (my engine is 110 hp) so I am running just under 20% loading. I have not seen any signs of problems and have asked a couple of friends who are experienced diesel engineers to take a quick look, and they have confirmed that I am not causing a problem.
One final point, every so often it is sensible to test the engine at full power for at least half an hour, until the temperature has settled. Not only will it help to clean up any unburnt deposits it will show up any weakness in the cooling system. Better to find out near to base than when cruising miles away just after you've heard a gale warning!
mortehoe
New member
Perhaps you would care to explain ....
" ....I like to run my Yanmar at 1800 RPM which in my system gives me 20 hp (my engine is 110 hp) so I am running just under 20% loading ... "
Perhaps it was a typo??? ie [what it should be] ... "so I am running just under 60%" .... = BIG difference in fuel consumption!
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" ....I like to run my Yanmar at 1800 RPM which in my system gives me 20 hp (my engine is 110 hp) so I am running just under 20% loading ... "
Perhaps it was a typo??? ie [what it should be] ... "so I am running just under 60%" .... = BIG difference in fuel consumption!
/forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif
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Anonymous
Guest
Re: Perhaps you would care to explain ....
No, I mean 20%. To obtain the loading for your boat you have to go to the power/speed curve in the workshop manual and read off actual figure. At 1800 RPM my engine/gearbox is delivering 20 hp into the propshaft.
If you check your workshop manual you should find a curve of specific fuel consumption in gm per hp-hr i.e. grammes of fuel for every horsepower-hour, which has an almost flat response from 10% to 90% power. The big saving in fuel at low power/RPM is due to lower hull friction and hydrodynamic forces, not a increse in fuel consumption in the engine - the same is true of cars, of course.
No, I mean 20%. To obtain the loading for your boat you have to go to the power/speed curve in the workshop manual and read off actual figure. At 1800 RPM my engine/gearbox is delivering 20 hp into the propshaft.
If you check your workshop manual you should find a curve of specific fuel consumption in gm per hp-hr i.e. grammes of fuel for every horsepower-hour, which has an almost flat response from 10% to 90% power. The big saving in fuel at low power/RPM is due to lower hull friction and hydrodynamic forces, not a increse in fuel consumption in the engine - the same is true of cars, of course.
Boathook
Well-known member
If I can motorsail it can nearly halve the fuel consumption and makes the boat motion easier.
Drascomber
New member
In a cruising boat there is a usually a course where you think "I can't sail well that close to the wind so I'll motor" but by motor sailing you can sail closer to the wind and save the juice you would use if you were just motoring. Even on this kind of course in a stiff breeze I can see my fast motoring 5 knot cruise lifted to 6 knots - or reduce revs by 700 and keep the noise and fuel consumption down.
BlueSkyNick
Active member
In addition to the fuel consumption and speed debates, another benefit of having the mainsail up is to provide an immediate source of power and hence control, if the engine fails.
Not a big issue if in open water, but definitely helpful if passing through a busy channel or similar.
Not a big issue if in open water, but definitely helpful if passing through a busy channel or similar.
Caer Urfa
Well-known member
I had a twin engined diesel Motorboat for years before changing to my present Colvic Watson motorsailor.
Best thing I ever did, presently have a 27hp diesel in a 24' boat,it's good to have something in hand as power can also get you 'out of trouble'.
Cruise under power at 2000rpm @ 5.5-6 knots.
Sail with mainsale + Genoa only depending on wind but average 4.5 to 5 knots, best at 6.4 knots.
As others I sail 75% of the time and motor 25% depending on the wind, running costs since January this year £45,
Motorsailors give you the best of both worlds as long as you are not in a hurry,and protection in heavy weather!
Hope this helps
Best thing I ever did, presently have a 27hp diesel in a 24' boat,it's good to have something in hand as power can also get you 'out of trouble'.
Cruise under power at 2000rpm @ 5.5-6 knots.
Sail with mainsale + Genoa only depending on wind but average 4.5 to 5 knots, best at 6.4 knots.
As others I sail 75% of the time and motor 25% depending on the wind, running costs since January this year £45,
Motorsailors give you the best of both worlds as long as you are not in a hurry,and protection in heavy weather!
Hope this helps
