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post #1 of 16 Old 06-23-2014 Thread Starter
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tacking angles

I always thought that, since I can sail approximately 45 degrees off the wind, that I should be able to tack 90 degrees. But in practice, I'm not getting anywhere near that. My angles look closer to 45 degrees to me.

(I also don't know how much leeway is normal for my boat).

Here are a couple of tracks from recent sails in approximately 10kt winds. You can easily see where I'm running and where I'm beating. What do you think of the angles? Am I making decent windward progress, or should I expect more?

My boat is a swing keel, if that makes any difference, and the keel is in excellent condition.

Thanks for looking!





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post #2 of 16 Old 06-23-2014
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Re: tacking angles

Assuming little or no current on such a lake, those do look like rather wide angles! Unfortunately the GPS track includes effects of leeway and current, so it's difficult to analyze without being on the boat.

Ron

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post #3 of 16 Old 06-23-2014 Thread Starter
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Re: tacking angles

Yes, I don't think there is any current to speak of in either of the lakes pictured. And leeway is something I understand, of course, but I have no way of knowing how much progress it is costing me. The ninety degrees I "should" be able to tack, minus the 45 degrees I'm actually getting, makes it seem that I'm losing 45 degrees. This is more than I would have expected, but of course I'm a newbie and have nothing to base that on.

By the way, I understand how excessive heeling leads to excessive leeway, so I do try to keep my boat on her feet for the most part. I use the traveler and the mainsheet to limit heeling to generally 15 degrees or less, and weather helm to a minimum.
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Re: tacking angles

A more revealing index would be the change in compass heading between tacks. THAT's what should be somewhere between 90/100 degree difference, though I suspect many non performance boats will be closer to 110 degrees as a rule.

If there's negligible current, and your compass numbers are "OK" then the wide angles on your GPS track will most likely be due to the leeway you're experiencing.

Ron

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post #5 of 16 Old 06-23-2014
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Re: tacking angles

Dixie, the good news is I’m seeing a lot of consistency in your sail trim. Remember that your wind fly is measuring apparent wind which is forward of where the true wind is. Subtracting your compass headings (you can also measure this with a protractor off your plots.) will give you your tacking angle. Remember also, that your swing keel boat isn’t the most efficient and the simple C22 standing rigging won’t allow for the tightest of sheeting angles. You can work to see if you can “dial in” your boat. Start experimenting with mast rake as more rake induces more weather helm and gets you pointing better. Then go on to stay tension, fairlead car position etc. You will also need to look at your boat speeds while you’re doing this to make sure you are not sacrificing VMG for tacking angle. In the FWIW department my C34 is in the neighborhood of a hundred degrees.

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post #6 of 16 Old 06-23-2014
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Re: tacking angles

Looks to me like something is off on your port tack. Maybe check the slack on the shrouds.
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Re: tacking angles

Gamayun, are you looking at the Lake Harris plot? I attributed that tail-off on port as 1) getting headed along that shore (persistent wind shift) and, 2) perhaps a little heating up before they tack. I like the symmetry from the Lake Eustress one. The tacks are pretty much running parallel to each other and they are in the center of the lake where I assume the wind is pretty consistent. If one tack was performing much better than the other, I’d look to see if the mast was in column first. For me, uneven shroud tension shows up in VMG but not necessarily in tacking angles.

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Re: tacking angles

Thanks guys, I'm getting some great info here. I'll definitely use the compass and a little math to get my "real" tacking angles next time, both port and starboard.

Now speaking of tension, may I stray just a little? I recently bought a Loos gauge, and tensioned the shrouds and stays according to North Sails' guide. While I was pleased to see that my "by ear" tensioning had at least been quite consistent, I had them a fair amount tighter than North recommends. And now when I sail, I see a little slack in the leeward stays. Is this normal?? I had not expected it.

Incidentally, this change in shroud tension happened in between the two sail days shown above. It didn't seem to make any change in the angles, which I just used a protractor on, and they seem to average about 60 degrees, which is at least better than I thought.
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post #9 of 16 Old 06-23-2014
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Re: tacking angles

Dixie, you are well on your way… Most sailors don’t really think about tacking angles, VMG and the like. They think that those of us who do are “nuts” to wrangle the last tenth (or is it the last half) knot out of our boats. I just like to sail well…

Standing rigging: What you did using the North guide was to static tune your boat. The next step is dynamic tune. You do this during a sail in your “typical” wind conditions by tightening the shrouds to eliminate the slack on the leeward ones. Then use the Loos to confirm the tension so you can replicate the tension later. Headstay is a little tougher insomuch that you want to reduce (eliminate) the “sag” to leeward (note that this is also adjusted out by using your backstay adjuster). Too much rigging tension will make your boat a pig in light air and too little will make your upper portion of the sail inefficient. Out here in SF, I have a heavy air, “summer”, tension and a lighter tension for the winter. When you are doing your tuning, you want to keep your mast in column and with the proper rake. Too little rake will again, make you boat a pig and not point. Too much and you will have excessive weather helm.

Shroud tension affects VMG. Rake affects tacking angle.

A little war story. Back in ’09 we took the Cal 40 to the Rolex Big Boat Series. We noticed that a Cal, whose owner, with a really big checkbook, had Stan Honey optimize the boat for performance. The thing that struck us was the total lack of lower forward shrouds. The morning of the second day we went aloft and removed ours. Another boat did the same, and another until by the end of the regatta, no Cal 40 had lower forwards. We have been racing that way ever since.

PS. I've been thinking about Gamayun's comments, and you actually might be seeing the effects of leeway in your track. That would show up as an "opening" of the course angle as your boat sags off to leeward. Don't worry, all boats have it.
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post #10 of 16 Old 06-23-2014
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Re: tacking angles

What size jib do you have? Are you sure your jibsheet leads are set correctly?
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