I think I know what you mean, a frequent phenomenon in my experience. It's very common to explain differing performance with mast that isn't completely vertical. I am not saying it is necessarily wrong, but I have my doubts that it would be the main problem here. E.g on a 10 m mast, if the shroud length differs 2.5 cm (something that is hard to achieve if one pays any attention when stepping the mast), the top is off centerline by 10 cm. That's less than 1 degree off vertical. While not nothing, I doubt the difference in performance is dramatic, and could be hiked away at least temporarily to see if that's the problem. There is, however, another possible cause, and you mentioned two things that got my attention: light wind and exactly same sail setup for both tacks. When we are sailing in light wind, the vertical wind shear might contain not only speed gradient, in which case symmetric sail setup is fine, but also direction gradient, in which case symmetric sail setup is wrong. I have sailed in conditions where we are pointing incredibly high on one tack (judged by the wind indicator), and on opposite tack had to go disappointingly low. On one tack the mainsail needed no twist whatsoever, and on the other no amount of twist seemed to be enough. Yet the resulting tack angle was about 90 degree. These conditions have always been in light air, often when the water surface has cooled somewhat and an inversion layer has formed over sea surface. Trimming the sails so that the streamers are happy and there's right amount of pressure on the rudder might result in very different trim on opposite tacks in special conditions. In more wind, the turbulence kills the direction gradient, leaving the speed gradient which means some twist in sails is still needed. I'd be interested to know what you think about this theory.
Hi, that's a very interesting theory and might well explain it. I should have caveated my video by saying that my access to accurate wind information was limited, as both my mechanical wind vane and electrical wind sensor were out of action (seagulls!). In hindsight it's difficult to accurately assess how well we were pointing other than in relation to other boats. I will say that next time out, the boat did seem better balanced... however it was not in light winds, so I expect a lot of what you are saying above, regarding direction gradient in light winds, probably accurately describes what we were seeing.
Given the fact that the difference is in the center of the mast, it could still make a difference as the mainsail would be either a bit convex or concave depending on the tack
It was very light airs that evening, but it was also very low current. It didn't help that my wind instruments weren't functioning, as that made it difficult to tell how close to the wind I was sailing.
I think I know what you mean, a frequent phenomenon in my experience. It's very common to explain differing performance with mast that isn't completely vertical. I am not saying it is necessarily wrong, but I have my doubts that it would be the main problem here. E.g on a 10 m mast, if the shroud length differs 2.5 cm (something that is hard to achieve if one pays any attention when stepping the mast), the top is off centerline by 10 cm. That's less than 1 degree off vertical. While not nothing, I doubt the difference in performance is dramatic, and could be hiked away at least temporarily to see if that's the problem.
There is, however, another possible cause, and you mentioned two things that got my attention: light wind and exactly same sail setup for both tacks. When we are sailing in light wind, the vertical wind shear might contain not only speed gradient, in which case symmetric sail setup is fine, but also direction gradient, in which case symmetric sail setup is wrong. I have sailed in conditions where we are pointing incredibly high on one tack (judged by the wind indicator), and on opposite tack had to go disappointingly low. On one tack the mainsail needed no twist whatsoever, and on the other no amount of twist seemed to be enough. Yet the resulting tack angle was about 90 degree. These conditions have always been in light air, often when the water surface has cooled somewhat and an inversion layer has formed over sea surface.
Trimming the sails so that the streamers are happy and there's right amount of pressure on the rudder might result in very different trim on opposite tacks in special conditions. In more wind, the turbulence kills the direction gradient, leaving the speed gradient which means some twist in sails is still needed.
I'd be interested to know what you think about this theory.
Hi, that's a very interesting theory and might well explain it. I should have caveated my video by saying that my access to accurate wind information was limited, as both my mechanical wind vane and electrical wind sensor were out of action (seagulls!). In hindsight it's difficult to accurately assess how well we were pointing other than in relation to other boats.
I will say that next time out, the boat did seem better balanced... however it was not in light winds, so I expect a lot of what you are saying above, regarding direction gradient in light winds, probably accurately describes what we were seeing.
Given the fact that the difference is in the center of the mast, it could still make a difference as the mainsail would be either a bit convex or concave depending on the tack
And I guess the difference as measured at the dock is probably a fair bit less than when under sail as it would be under load.
I always assumed there was just a slight current or wave angle vs wind angle that sets up a favorable tack.
It was very light airs that evening, but it was also very low current. It didn't help that my wind instruments weren't functioning, as that made it difficult to tell how close to the wind I was sailing.
Interesting. I always thought my boat was not symmetrical under the waterline.
As in symmetrical port side and starboard side when the boat is on the mooring/upright?
More likely the difference is in the water.
Yeah that's a possibility.
In hindsight it's difficult to verify the actual performance as both my mechanical weather vane and electronic wind sensor were out of action.