Greg Fisher's "gears"

Submitted by frank barbehenn on Thu, 12/29/2005 - 16:34
I have read his articles and the book he did and I still do not understand exactly which gear is what. I understand the idea, and I understand some of what he is saying. But I cannot picture "first" "second" "third" and fourth" and tie that to terms like power, acceleration, speed and pointing yet. Can anyone clear up the mystery? I'd like to pair up the terms of speed etc with the gears and pair those to the actual positions of the boat going upwind. So for example, is "pointing" considered fourth gear? Is footing considered acceleration, and first gear? Is in the groove, between pointing and footing considered speed, and third gear? What is second gear? If you get my question and understand please advise.
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Comments

Frank, The idea of "gears" is a practical way to describe sai

Submitted by Gallus 102 on Tue, 01/03/2006 - 11:54.
Frank, The idea of "gears" is a practical way to describe sail settings for a sailor on the race course. If you do as Fisher describes, you will be fast through a variety of conditions and scenarios that happen to all of us in every race. If I understand your questions correctly, it is how to tie all these different settings and concepts together. Here's my interpretation of the gears: When sailing to windward, you typically sail the rig within a range of 55 to 40 degrees angle of attack (centerline of the boat to the true wind). Your tiller controls the angle of attack because your rig is attached to the boat. Your sheet and vang are the primary sail controls used to manage the sails' lift and drag in real-time; outhaul and cunningham are secondary (i.e. not adjusted as frequently). The higher the angle of attack, the more lift (power) is available to make the boat go faster or accelerate. The trade-off is in distance to windward (you are not sailing as close to the windward mark. (NB---my angle of attack examples are an estimations of a range for the FS) 1st gear corresponds to a high angle of attack (about 55-50 degrees). There's lots of lift available and you use this to get the boat moving and accelerate from a major loss of speed. Second gear is probably between 50 and 47 degrees. Not quite as much power, but gives you acceleration when you already have momentum. Third gear is in the "groove" just either side of 45 degrees. It's for when the boat is up to speed and represents the best trade-off between boat speed and distance to windward (VMG). Fourth gear is low power and low drag. It is only sustained for a few seconds at a time to point high (e.g. 43-40 degrees) when you have speed to begin with. As soon as you feel the speed dropping, fall off (i.e. go to a higher angle of attack) to accelerate back to your VMG and start the cycle all over again. Think of it as a continuum within the angle of attack range. The sail settings of the "gears" are the optimal lift/drag configurations at four points with in the range. Jim Davis FS 784

Jim: Most helpful!! I guess I was close.

Submitted by frank barbehenn on Tue, 01/03/2006 - 13:24.
Jim: Most helpful!! I guess I was close. To "tweak" this then and make sure I understand, pointing will decrease speed, unlike a true fourth gear. The trade-off is that it is more direct to the mark versus loss of speed. Footing will give more power and more speed relative to pointing and the groove, but lose the direct route to windward. If one stayed at the foot (cause the direction was okay let's say), and one worked the mainsheet, then that "gear" would actually give rise to greater speed than the groove--speed increases as one moves the angle of attack of the boat to the beam reach position. In this way, "first gear" increases power relative to pointing but also is higher in speed relative to pointing and groove--unlike a real "first gear". And footing is slower than beam reaching. Is this correct thinking? Frank

Frank, You're quite close--sailing to windward is all about t

Submitted by Gallus 102 on Tue, 01/03/2006 - 14:49.
Frank, You're quite close--sailing to windward is all about trading off speed for distance. Most of us (myself included) sail pretty much be feel and intuition and don't think a lot about the dynamics behind it (though we should pay a bit more attention to it!) For most wind ranges we sail in, the fastest point of sail will be a beam reach (90 degrees angle of attack). Head up and you go slower, fall off and you go slower. By the same token, if you need to pick up some speed on any other point of sail, just aim the boat a little closer to a beam reach and you'll go faster. Jim Davis FS 784

quote:[i]Originally posted by Gallus 102[/i] [br]Frank, For

Submitted by Transom on Wed, 01/04/2006 - 08:43.
quote:
[i]Originally posted by Gallus 102[/i] [br]Frank, For most wind ranges we sail in, the fastest point of sail will be a beam reach (90 degrees angle of attack). Head up and you go slower . . .
I'll add that this seems to confuse some people, because they think that they are going faster when they begin to point up from a beam reach (right until they point to high and the sail luffs). However, you are going slower - it only seems faster because the apparent wind increases.

Transom makes a good point.

Submitted by Gallus 102 on Wed, 01/04/2006 - 09:30.
Transom makes a good point. The apparent wind will change your perception of the actual boat speed. Below is a link to the Unofficial Flying Scot website where they have a polar printout for FS performance prediction. It shows how your speed varies by angle of attack and in most light to moderate wind ranges, the fastest boat speed is at 90 degrees. It isn't until you get into the planing mode that the best angle starts to go above 90. http://home.att.net/~unofficial-flyingscot-page/images/FSPolar.pdf Jim Davis FS 784

Jim: I took a look, actually several!, at the site you mentio

Submitted by frank barbehenn on Fri, 01/06/2006 - 15:24.
Jim: I took a look, actually several!, at the site you mentioned. Fascinating, and potentially satisfying my interest in being specific! At this point in trying to understand and assimilate the material, I have several questions. 1. Was this an empirical study with instrument readings or a computer generated model? 2. The AWA doesn't make sense to me. If the TWA is for example 34 degrees at 8 knots, it doesn't make sense to me that the AWA (at measthead) is only several degrees (3-5 degrees). Such twist in the wind direction is enormous and the wrong direction--forward not aft, and I thought we were talking about 5-10 degree twist at most as we went up the sail (for wind above 5 knots). I must be reading the meaning of the numbers wrong, but can't discern how. 3. Is it really true that one need not flatten the mainsail upwind until 16 knots or so, and then only slightly? (I know he used three crew member weight, but still...) Thoughts? Frank

Frank, I believe this is a computer simulation rather than an

Submitted by Gallus 102 on Mon, 01/09/2006 - 06:31.
Frank, I believe this is a computer simulation rather than an empirical study. I don't know which algorithms and assumptions were used, so any thorough explanation should really come from whoever ran the program. Re the AWA--it seemed low to me, as well, but (per the above) I can't offer any insight. Re flattening the mainsail--again, this seems to be an assumption in the model. I would recommend following Fisher's gears rather than the print-out tables for sail trim. The "take-away" from the polars is the trade-off between boat speed and distance-made-good over the race course. You need to understand that. There are also two pages at the end on boat trim. One has a table giving the wetted surface of the hull at various angles of heel (the more you heel, the less wetted surface). At lower boat speeds, most of the hull drag is from the wetted surface. This changes as the boat goes faster when form drag and wave making resistance become more significant. The last page is a stability curve for the Scot. It shows very clearly why a Scot will almost always turtle when it capsizes. Stability vanishes at 87 degrees and had little positive righting arm before that. The Scot floats very high when on its side, so it takes only a little wind or wave pressure to send it the rest of the way over. And since high winds are frequently associated with capsizes, you are going for a swim..... Jim Davis FS 784