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Old 07-11-2015, 06:57   #46
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Re: are the new sail boat overpowered?

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Originally Posted by Dockhead View Post
Polux is spot on here. Autoprop is brilliant for keeping a load on a normal or even better, somewhat oversized engine. Would be terrible for a boat with an undersized engine.
Yep sure..

Here is the magazine

http://www.sigmadrive.it/1/upload/vo...avril_2009.pdf


About 20-30% less pushing power from standstill...but it's the faster at same RPM...

For this i GUESS that bigger is better...


@Tuffr2 Are you joking?
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Old 07-11-2015, 07:00   #47
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Re: Are The New Sailboats Overpowered?

if your engine can get your boat away from the rocks in a stiff breeze when there is a leeshore pulling you, and if you can manage to get your boat uphill at more than 2.1 kts every hour, if you can manage to make it successfully into a port with what you have in a storm, then you are not overpowered.
screw the numbers. try reality. it is better to know you will be able to pull out of a dangerous situation than face it with less power than you need.
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Old 07-11-2015, 07:11   #48
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Re: Are The New Sailboats Overpowered?

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Originally Posted by tuffr2 View Post
Remember all HP calculations need to take elevation into accout...just saying.

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I often worry about my hp derating when the tide is up........


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Old 07-11-2015, 07:20   #49
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Re: Are The New Sailboats Overpowered?

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I often worry about my hp derating when the tide is up........


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At least you can take comfort that your teapot will boil faster......
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Old 07-11-2015, 07:35   #50
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Re: Are The New Sailboats Overpowered?

LMAO

I really like this forum
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Old 07-11-2015, 08:04   #51
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Re: Are The New Sailboats Overpowered?

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At least you can take comfort that your teapot will boil faster......

I do draw the line at adjusting recipes though.......


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Old 07-11-2015, 13:58   #52
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Re: Are The New Sailboats Overpowered?

Joshua had a 8hp air cooled mixed fuel gas engine, essentially a lawn mower motor and Moitessier was very content with it. However, he was pretty nutty too. And for all his seamanship skills he sank a lot of boats. Still a personal hero though.
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Old 07-11-2015, 17:25   #53
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Re: Are The New Sailboats Overpowered?

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Originally Posted by stefano_ita View Post
Very interesting...

What engine do they had? Max hp? At how many rpm? Gearbox? Prop pitch/diameter? How many rpm and fuel consumption in cruise with the 2 engine?

Well for sure i'd trust more an engine in the middle of the ocean with waves and maybe very strong wind that doesn't allow to use the sail, to motor for hours if not days no stop, maybe slow...and you need a quite big, powerful engine...

I don't think in that condition have saved 2.000 euro and die without engine would be a nice idea...

I would get a pool about my ordinary question LOL
Sorry for not being able to answer to all your questions but in what regards sailing I am more on the sailing side of things and I don't know what is the gearbox ratio, not even on my boat, but I can get you some more information.

The first boat was a Salona 41, with 7500kg of displacement with an optional 53hp Yanmar engine (saildrive) I suppose the 4jh5E (2011 boat). The Salona was only 3 or 4 months old, I charted it for two weeks and the gearbox was already a lot of problems to engage the gear. I charted that boat for 15 days. The propeller was a folding propeller, the one that is used by Salona. Don't know the brand.

The other is my own sailboat, 2007 a Comet 41s, with a 8000kg of displacement that has a Lombardini LDW 1404M that supposedly has 40hp but that a guy from Comet says that it really has only 36, also with a saildrive.

Due to the smaller than advertise power the Comet 41s comes with a foldable J prop that is too big for the engine power. Under advise from the guys from Comet I changed the propeller for a flexofold. it become just a little bit better especially at high revs, with more pull on dificult situations, but nothing special.

Regarding using the engine with bad weather, the Comet 41s is a very good sailboat and when there is wind it can make a decent VMG sailing upwind. Against waves and wind I can do a bit better than sailing if I motorsail using, even with considerable wind, all the (big) mainsail up and going at about 15 of the apparent wind.

But that is just a bit better not a lot better since that with strong wind I can do between 26 and 35 (depending of the size of the waves and type) and I can sail faster (about 1 to 2K) sailing at those points, than motoring closer to the wing with the mainsail up. With really bad weather the boat goes better sailing than motoring against wind and waves.

The positive side of it is the really low consumption of the engine at 2000 rpm with good sea conditions (5.0/5.5K) or going downwind where it can waste between 2 and three liters hour, closer to two, I believe. That will give it an autonomy of about 300 to 350nm, for a 150L tankage.

Normally, considering the time I sail and the time I use the engine, on the Med, that has a lot of variable and weak winds, I need to make the full of water (400L) two times more frequently than what I need to put diesel. I sail alone with my wife and need to fill the water tank each 15 days.

Anyway my sailboat with that engine is truly a sailboat with an auxiliary engine and with little wind I can go faster with sails than with the engine.

I feel that the sailboat in heavy conditions sail better with sails than with the engine. If it is that bad and the wind so strong that will not allow even the use of a storm sail, on my boat, I would say probably 50/60K, then I don't need any sail to sail since the boat will sail with bare pools and you will have some steerage.

I only tried once in big gusts of wind coming at 90 and I could maintain the course. I had took all the sails out and I did not want to run the engine since the heel was considerably more than the recommended 15 and sometimes the boat heeled to about 40/45.
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Old 07-11-2015, 21:49   #54
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Re: are the new sail boat overpowered?

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Originally Posted by stefano_ita View Post
thanks..
i calculated only the theorical engine fuel consumption...in theory with more turque and less rpm= more efficient...


your boats brands\model? gearbox ratio? prop size?
tayana 48, box ratio unknown, 19x17 I think.
Quote:

quote the last message...3 cylinder...more vibration, unbalanced...naa..
VW makes a car with one, and now chevy does too. Kubota and cummins make a 3. Its a sailboat, how much motoring are you doing, and why?
Quote:

went this summer with a stefini 36ft with 76 hp....12 ton...i don't know else data but was about 3 liter per hour according to the owner...rpm counter was broken
I knew a man on a twin 350 32' boat that claimed 9mpg on plane.
People are not very trustworthy most of the time/results are biased.
I had a 25' with a single 305, and maybe got 1.8mpg...

Point is, the smaller the displacement, the slower the speed, the less RPM, the less fuel used. A cummins turning at 1800rpm under about 40-60% of max power at RPM would be the most efficient fuel engine.
Thats what I would size for. 1800rpm, 40-60% load at RPM.
The bigger the prop the better. I can fit a 30" wheel, and I plan to. The added drag under sail is worth the NMPG when doing the loop.
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Old 08-11-2015, 01:15   #55
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Re: Are The New Sailboats Overpowered?

Quote:
Originally Posted by zeehag View Post
if your engine can get your boat away from the rocks in a stiff breeze when there is a leeshore pulling you, and if you can manage to get your boat uphill at more than 2.1 kts every hour, if you can manage to make it successfully into a port with what you have in a storm, then you are not overpowered.
screw the numbers. try reality. it is better to know you will be able to pull out of a dangerous situation than face it with less power than you need.
I would second that!
Once you finish with theoretical calculations, you need to consider extreme conditions.
Engine problems - it works, but not to full power/rpm
sailing against current
sudden evasion manoeuvres
Breaking waves
etc., etc,...
And, larger engine, does not automatically means more fuel, as you will normally cruise at lower rpm. Just take care that the engine is not too big in extreme, where cruising rpm will be too low for its health.
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Old 08-11-2015, 06:21   #56
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Re: Are The New Sailboats Overpowered?

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Originally Posted by Polux View Post
Sorry for not being able to answer to all your questions but in what regards sailing I am more on the sailing side of things and I don't know what is the gearbox ratio, not even on my boat, but I can get you some more information.

The first boat was a Salona 41, with 7500kg of displacement with an optional 53hp Yanmar engine (saildrive) I suppose the 4jh5E (2011 boat). The Salona was only 3 or 4 months old, I charted it for two weeks and the gearbox was already a lot of problems to engage the gear. I charted that boat for 15 days. The propeller was a folding propeller, the one that is used by Salona. Don't know the brand.

The other is my own sailboat, 2007 a Comet 41s, with a 8000kg of displacement that has a Lombardini LDW 1404M that supposedly has 40hp but that a guy from Comet says that it really has only 36, also with a saildrive.

Due to the smaller than advertise power the Comet 41s comes with a foldable J prop that is too big for the engine power. Under advise from the guys from Comet I changed the propeller for a flexofold. it become just a little bit better especially at high revs, with more pull on dificult situations, but nothing special.

Regarding using the engine with bad weather, the Comet 41s is a very good sailboat and when there is wind it can make a decent VMG sailing upwind. Against waves and wind I can do a bit better than sailing if I motorsail using, even with considerable wind, all the (big) mainsail up and going at about 15 of the apparent wind.

But that is just a bit better not a lot better since that with strong wind I can do between 26 and 35 (depending of the size of the waves and type) and I can sail faster (about 1 to 2K) sailing at those points, than motoring closer to the wing with the mainsail up. With really bad weather the boat goes better sailing than motoring against wind and waves.

The positive side of it is the really low consumption of the engine at 2000 rpm with good sea conditions (5.0/5.5K) or going downwind where it can waste between 2 and three liters hour, closer to two, I believe. That will give it an autonomy of about 300 to 350nm, for a 150L tankage.

Normally, considering the time I sail and the time I use the engine, on the Med, that has a lot of variable and weak winds, I need to make the full of water (400L) two times more frequently than what I need to put diesel. I sail alone with my wife and need to fill the water tank each 15 days.

Anyway my sailboat with that engine is truly a sailboat with an auxiliary engine and with little wind I can go faster with sails than with the engine.

I feel that the sailboat in heavy conditions sail better with sails than with the engine. If it is that bad and the wind so strong that will not allow even the use of a storm sail, on my boat, I would say probably 50/60K, then I don't need any sail to sail since the boat will sail with bare pools and you will have some steerage.

I only tried once in big gusts of wind coming at 90 and I could maintain the course. I had took all the sails out and I did not want to run the engine since the heel was considerably more than the recommended 15 and sometimes the boat heeled to about 40/45.

thanks, with autoprop the best benefit would be motor sailing, even in quite adverse condition, with the engine maybe at 1200-1300 rpm helping the sails...
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Old 08-11-2015, 06:26   #57
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Re: are the new sail boat overpowered?

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Originally Posted by sailnow2011 View Post
tayana 48, box ratio unknown, 19x17 I think.

VW makes a car with one, and now chevy does too. Kubota and cummins make a 3. Its a sailboat, how much motoring are you doing, and why?

Because in the Med there are even week with just a almost 0 wind


I knew a man on a twin 350 32' boat that claimed 9mpg on plane.
People are not very trustworthy most of the time/results are biased.
I had a 25' with a single 305, and maybe got 1.8mpg...

....wait i take the ticket out...3,6 liter/hour..going 5,5 kts and 6-6,2 with a 5 kts wind...

Point is, the smaller (the bigger i guess) the displacement, the slower the speed, the less RPM, the less fuel used. A cummins turning at 1800rpm under about 40-60% of max power at RPM would be the most efficient fuel engine.
Thats what I would size for. 1800rpm, 40-60% load at RPM.
The bigger the prop the better. I can fit a 30" wheel, and I plan to. The added drag under sail is worth the NMPG when doing the loop.
I quote 100% the last paragraph
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Old 08-11-2015, 06:34   #58
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Re: Are The New Sailboats Overpowered?

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Originally Posted by meirriba View Post
I would second that!
Once you finish with theoretical calculations, you need to consider extreme conditions.
Engine problems - it works, but not to full power/rpm
sailing against current
sudden evasion manoeuvres
Breaking waves
etc., etc,...
And, larger engine, does not automatically means more fuel, as you will normally cruise at lower rpm. Just take care that the engine is not too big in extreme, where cruising rpm will be too low for its health.
Extra quote on this,

With the stefini 36, this summer, had a evasive manouver twice in the entry of a very very very busy port, all rudder right side, almost full throttle, and 2 second after the boat has turned 90 degree...ok we were going about 4,5 kts...but heel what a power
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Old 08-11-2015, 07:02   #59
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Re: Are The New Sailboats Overpowered?

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Originally Posted by stefano_ita View Post
thanks, with autoprop the best benefit would be motor sailing, even in quite adverse condition, with the engine maybe at 1200-1300 rpm helping the sails...
Yes, I had an autoprop on my previous boat and sometimes the RPM where even less, so little that you forget that you had the engine running but as it was pointed out an auto-prop would be a bad option on my case. Not a good option if you have just an auxiliary engine and not a relatively powerful engine (for a sailboat).
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Old 08-11-2015, 07:16   #60
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Re: Are The New Sailboats Overpowered?

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Yes, I had an autoprop on my previous boat and sometimes the RPM where even less, so little that you forget that you had the engine running but as it was pointed out an auto-prop would be a bad option on my case. Not a good option if you have just an auxiliary engine and not a relatively powerful engine (for a sailboat).

Yes, i was more oriented on a motor sailer...

I'd mean, strong wind, only sails powered, medium winds, sails+ engine just above idle, and well no wind motoring
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