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-   -   If it's not luffing, it's helping? (http://www.sailnet.com/forums/general-discussion-sailing-related/84868-if-its-not-luffing-its-helping.html)

steveg353 03-11-2012 12:37 PM

If it's not luffing, it's helping?
 
This question pertains to motor sailing directly into the wind with mainsail only.
Is it true that if you pull the traveler all the way over(whichever side seems closer to windward) and sheet in tight, that as long as the main is not luffing, it is helping to move the boat forward. I was told that if you cannot “hear” the sail, it is helping.
It feels like it helps to me but I wanted to see what the salts had to say about it.
I have a trip this week that, according to the reports, I will be running about 20 miles dead into the wind in a very busy ship channel.

Faster 03-11-2012 12:47 PM

Re: If it's not luffing, it's helping?
 
If you're truly "head to wind" and haul the traveller to one side or the other to stop the noise I'd say it's just drag.. if your apparent wind is, say, 20 or 25 degrees off the bow then you're probably getting some drive.

In any event it's WAY better for the sail to stop the luffing, and way easier on the nerves and ears. However if you know the whole trip is upwind and it's not rough, I'd douse the sail. If it's rolly then there's a stabilizing effect that's worthwhile, as long as you're not beating the sail to death.

steveg353 03-11-2012 01:09 PM

Re: If it's not luffing, it's helping?
 
That is what I was wondering...does it cause forward drive or dreaded drag when the sail is tight and silent. Hopefully, the wind will be off the nose enough to help but I'm pretty sure the diesel is going to get a workout this week.
I love my diesel...I just hate using it.

overbored 03-11-2012 02:22 PM

Re: If it's not luffing, it's helping?
 
Quote:

Originally Posted by steveg353 (Post 843831)
That is what I was wondering...does it cause forward drive or dreaded drag when the sail is tight and silent. Hopefully, the wind will be off the nose enough to help but I'm pretty sure the diesel is going to get a workout this week.
I love my diesel...I just hate using it.

it depends on the wind speed and the angle of the wind if you are motoring at lets say 6 kts and the wind is on the nose then it is drag. if you are motoring at 30 dergees to the wind and motoring at 4 kts and the wind is blowing 20 then it maybe helping if the wind is only 6kts then it is drag. basicly if you are motoring at a given speed that there is not enough wind to make the same speed while under sail alone then the sail is drag.

chris_gee 03-11-2012 03:17 PM

Re: If it's not luffing, it's helping?
 
Not sure about the above. Because of the motoring the apparent wind moves forward and increases. As a result one might sail as if in 10 knots v 6 say at 4
instead of 2. The drive the sail produces depends on the angle to the apparent wind, and therefore requires the true wind to be somewhat further abeam. It may be that at 30 apparent you get drive whereas at 10 you get less drive than drag. In practice if you are getting more speed than the revs of the motor would give some of the force is coming from the sail as a result of the apparent wind increasing. Often the revs may be as low as 1000. However you still require an apparent wind angle which produces a force with a forward component. This may be say 30 meaning the twa is greater.
If the wind is in fact dead ahead not just light having the motor on will increase its strength but not produce a force on the sail other than drag think flags. Holding the boom to windward would produce a backward force.

CapnBilll 03-11-2012 03:30 PM

Re: If it's not luffing, it's helping?
 
The science factor is if the vector of force on the sail is forward of abeam, then it is helping, (you get better gas milage if too low to increase speed).

Sailormon6 03-11-2012 04:24 PM

Re: If it's not luffing, it's helping?
 
I can't explain the theory, but I have done a lot of motorsailing up and down the Chesapeake, alone as well as in company of other boats, and can say that motorsailing increases speed and saves significantly on fuel. Also, you can motorsail much closer to the wind than you can sail. I don't think you gain by moving the traveler hard to windward, although you can prevent the sail from luffing that way, and I do it occasionally, when I'm motorsailing head-to-wind, or nearly so, in a narrow channel, where I don't have room to tack. If you have room to tack, the better choice is to approximately center the boom, or "cheat" it a little to windward, and then motorsail at an angle to the wind that produces good drive from the sails and good speed. If you tack with the wind shifts, you'll help yourself even more. Even though you will add distance by tacking back and forth, you'll gain enough in speed and fuel savings to make it worthwhile.

SloopJonB 03-11-2012 05:31 PM

Re: If it's not luffing, it's helping?
 
Quote:

Originally Posted by Sailormon6 (Post 843886)
can say that motorsailing increases speed and saves significantly on fuel. Also, you can motorsail much closer to the wind than you can sail.

That's essentially why motorsailors were created in the first place. You get a much smoother and less rolly ride as well

steveg353 03-11-2012 06:33 PM

Re: If it's not luffing, it's helping?
 
I am just wondering if there is a point(dead into wind) when the main would hinder more than help. I am guessing, by what has been said, that if you must pull the sail past the centerline to stop luffing, it probably isn't helping power the boat forward or helping with fuel.


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