I've been thinking a lot about this lately. I totally understand the concept. I can see it operating every time I go sailing. My question is about chasing the tell tails when heading upwind. You've sheeted in as hard as you can, and as you build speed you start to bear away, bear away some more, and some more…to keep the tell tales streaming and the sail efficiently full with good angle of attack, until you are reaching back and forth with the true wind at 90 degrees to the boat (ie. not making upwind progress at all). This is fine if recreational sailing (as I've been doing) and just wanting to go fast. But if I get back into racing, do I understand correctly that pointing as high as you can to the upwind mark means ignoring the tell tales (which will suggest that you are luffing, which you are, relative to the changing apparent wind) and reading the wind on the water instead?
I copied this from a bother forum thread somewhere, which puts it well:
"… if you are sailing upwind on a triangle course, if you just sail to the apparent wind you can end up chasing it into a big speed building, bearing away curve that keeps the tell tales flowing, but isn't doing your VMG any good. Same thing downwind ( with a spin especially) , relating to the true wind v. your speed build is key for VMG, and deciding if it's a velocity header".
My thinking is specific to efficient VMG upwind during a race scenario.
Thanks
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Tom
Hobie Getaway, Nacra 5.5, Hobie Tiger
Wish list: A-cat classic, F16 Viper!
Northern California
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Apparent wind
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Posted: Jul 29, 2015 - 07:32 PM
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Posted: Jul 29, 2015 - 08:47 PM
I sheet the jib to conditions and follow the jib tells. If I head down too far, my tells on the leeward side will start to act up. I basically try to keep the windward side just about to break. During racing, I think you will find yourself constantly searching for as high a heading as possible. It always seems that everyone else is higher than you already.
Sometimes I do find myself heading down too far as the wind dies searching for speed. I think discipline is the answer there.
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Greenville SC
Offering sails and other go fast parts for A-class catamarans
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Posted: Jul 29, 2015 - 09:16 PM
I agree with the above more or less. You sheet the sails in for an upwind heading and then steer to the telltails. Telltails should be flowing at all times, not luffing. Once the wind gets to double trap conditions, you should be sheeted in hard and steering to keep the windward hull just skimming. A lot of it comes down to experience on your particular boat. Once you know where the groove is, you will drop in and it just becomes a matter of fine tuning.
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Posted: Jul 29, 2015 - 10:25 PM
sierracat:
I have been thinking about the same thing in my recreational sailing. And your logic makes perfect sense. You can graph it on paper.
I have not done much racing. But have raced in both really low winds, and really high winds. In the low winds, I keep the philosophy of never stalling the sails. And because you cannot see or feel a stall very well, you should allow the windward tells to act up. I read this in a book, so it must be true.
Regardless, in low winds, I don't think the problem is as pronounced.
In high winds, I have been sheeted hard in and still get luffing on the main. But not on the jib. And I am screaming along. I am not sure what all this means except that letting the main luff a bit will minimize the effect you describe.
It sounds like a go-pro or GPS experiment is needed. If I bear-off, will I go faster? Will I reach the mark sooner?
Edited by yelkenli1 on Jul 29, 2015 - 11:38 PM.
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Ted
Hobie 16
South Carolina Lake sailing
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Posted: Jul 30, 2015 - 01:20 PM
Most likely it means the slot between the main and jib is closed. You are backwinding the jib into the main. In very high wind, this may be unavoidable because you need to travel out the main a little bit but still keep the jib sheeted hard to prevent the jib from luffing and upsetting the balance of the boat. Ideally though, you want to travel out the jib a little if possible to keep the slot open. In the extreme case, the air coming off the jib will backwind the main so much that it causes the mast to counter-rotate.
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Posted: Jul 30, 2015 - 05:11 PM
Pointing and apparent wind shift is part of the black art of performance boat sailing as there are so many variables in play and it is very condition dependent. That you're thinking about is a really good thing!
In general, I think a true wind angle of about 45° is a good starting point. I've learned that in general, in bigger waves it pays to foot just a bit to keep the boat powered up and moving. In smooth water you can get away with a higher line.
Another big variable is the hull plan. Boats with daggers point higher, H16's seem to foot like crazy.
For keel boats they often publish polars so you know exactly what target boat speed should be for a given true wind speed and this is used as feedback for how high or low to steer (along with sail trim). Beach cats are not as limited by hull speed and the crew weight is often nearly equal to boat weight. Moving that weight around on the boat has a huge effect on boat trim and related drag. Therefore, polars have much less meaning (that's why it's super hard to find them).
One thing you might try is to either use a GPS device that calculates VMG, or use an app such as raceqs on your smartphone. Drop a couple of buoys out in the water about 1/4-1/2 mile apart upwind downwind of each other and then sail up/down a few times. You'll be able to see where you get best consistent VMG for all the variables of that particular day. Do it often enough and you'll learn where the sweet spot is and the factors that most affect it.
Edited by rehmbo on Jul 30, 2015 - 06:12 PM.
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Jeff R
'88 H18 "Jolly Mon"
'10 C2 USA1193
NE IN / SE MI
cramsailing.com
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