I love the folk who comment on my confused posts on the theory of wind and sails, such as the one on Gradients, Tacking Angles and Coriolis, itself an attempt to clarify some questions raised in an email from a Dutch reader. It is pure joy to me to see how an apparently simple question can send my readers off in all directions with such a varied mix of answers.
Carol Anne and Ant shared with us their experiences of wind variation sailing on inland lakes, while JB and Litoralis gave us a technical briefing on wind shear, gradients, viscosity and friction - not to mention fake forces. Fred gave us an insight on how wind varies with height on open water and even managed to explain how this whole issue is related to why there was so little sailing in Valencia last week. Tim and Milo focused in on one area that I had hoped somebody would pick up: why the apparent wind direction at the top of the mast will be different from that at the bottom.
But wait. I see some disagreement here. Tim believes that "the wind will be more on the beam the higher up the sail you go" whereas Milo claims that "the apparent wind is more beamy at the bottom."
Hmmm. They can't both be right, can they? What do you think?
But none of these comments support the suggestion in the original email that the Coriolis effect (fake or otherwise) can cause an asymmetry between port and starboard tacks such as in the claim that "on starboard tack .... sailors experience more need for twist high in the main then on the port tack." It would seem to me that this would be true if there were some consistent change in true wind direction (as well as speed) between the top and bottom of the mast. Are we all sure that this is never seen? Are higher altitude winds generally shifted the same direction from low altitude winds? If so, does this effect apply at the scale of a boat's mast?