the Weekly Whiffle
Wayfarer news of all kinds that's crossed Uncle Al's desk this week
Monday, December 3rd, 2007
....
Subject: Uncle Al tries to explain upwind angles to Andrew Haill
----- Original Message -----
From: Andrew Haill (W9657)
Sent: Tuesday, November 27, 2007 11:52 PM
Subject: a question of angles

Hi Al
 
... I've never quite got figured who benefits from shifts and any tactical considerations that might imply... you know the leeward boat gains with a header or whatever it is.  Have you ever come across anything that explains that easily and for the slow learner?   On the other hand, I should probably concentrate on boat speed  .. however it will eventually be frustrating to go fast in the wrong direction.
 
cheers,

Andrew


----- Original Message -----
To: Andrew Haill (W9657)
Sent: Wednesday, November 28, 2007 11:22 PM
Subject: angles, etc.

Hi, Andrew:
 
Thanks for the link update which I have corrected and posted, and while enjoying your site, I stole the "animated knots" link which is great - have added it to the WIT under "Useful Sailing Skills ...".
 
Have also changed rules Q caption as you suggested - as I proof-read it - probably around 2 a.m. - the point you make occurred to me but at the time, I said to myself, "Aw, fuck it!" But you have inspired/shamed me into changing it into better form.
 
Now, regarding shifts, can I first point you at two items of mine that I have just moved to a more logical spot on the WIT under Weather, Strategy & Tactics, and one I did for the Rebels:
The basics about angles: It usually isn't as clear cut as the images below, but we have to start the angles principles with all other possible variants removed. So what I have done is the following:
 
 
In the first image, two boats, Black and White, are dead even: White is exactly as far to leeward as she is ahead of Black. If the wind should shift (equally for both boats for the purpose of this angles lesson) one will gain vs. the other who will, of course, lose. How much depends on two factors:
1. separation (how far apart are the two boats?)
2. the size (# of degrees) of the shift
 
For images 2 and 3, I have left the boats exactly where they were for image 1: They have not moved even one inch forward. And yet one or the other boat - in a split second - can gain or lose literally miles of upwind distance on the other, simply due to a windshift, and to the way that this shift rotates the two boats.

Extremes rarely happen in real life, but they do illustrate the point being made in a more striking and, one hopes, unforgettable manner. So, for image #2, I have assumed that both boats get headed by 45°, as follows:
 
Assuming the Wayfarer's standard ability to sail closehauled at 45° to the true wind, such a 45° shift leaves White (the former leeward boat) directly off the bow of Black who was, until seconds ago, well to windward, and dead even with White in terms of distance made good to windward. Here you can really see how the amount of separation between the two boats directly affects the amount gained or lost. And of course, between these two boats (simplified again!), the boat to leeward and ahead gains if both are headed. Which in turn applies to all boats on the same tack that get the same shift: the boat to leeward and ahead gains.
A corollary of this is that, since we are all sailing the favoured tack on a day of oscillating shifts (back and forth) upwind, n'est-ce pas, it most often pays to attack a boat even with you or ahead of you from leeward and ahead since we expect our next shift to be a header, what with our current tack being lifted. Of course, attacking from windward and ahead is even more certain, but one rarely gets that luxury.
 
Which brings us to the other extreme, in which I have given both boats a 45° lift, as follows:
 
This illustration shows that a boat to windward and astern (or even one starting out dead astern) will gain if both boats are lifted. Again,  the gain/loss occurs without either boat moving forward, being caused solely by the rotation of the boats, and the amount of gain/loss depends on the size of the shift and the degree of separation between the boats. 
 
Of course, things are not often as simple as this: One boat may get a different wind strength and/or direction to that experienced by the other. But regardless of those variables, the most basic premise that needs to be understood, is how angles can change the relative positions of boats going upwind: leeward/ahead gains in a header but loses if there's a lift.
 
One last angles matter worth looking at, especially when sailing more open venues (like Lake Ontario) where wind slants tend to last longer, is the situation where you see a boat to windward and astern of you, sailing significantly higher than you are:
 
Here, I have let Black sail in Wind 2 which is backed 15 degrees to Wind 1 being experienced by White. For years, I got axed by playing the waiting game when I was in White's position. These wind splits can last for ages and can cost you immensely. My justification for not tacking always fell into two categories:
1. Sooner or later, we're bound to sail into what Black is getting, or Black will get what we are getting. This is a fallacy. Such a slant can last forever - certainly longer than the beat we are now on!
2. Hell, if we tack, we're only going to get knocked in a few seconds and then have to tack again. True, but it's a sacrifice that has to be made, unless you are OK with falling further and further behind.
 
Tacking if you're White in this situation will indeed always fall into the category of "cutting your losses". But what cannot be ignored here, is the fact that White's version of port tack here is unfavoured (by 15°) as compared to the port tack being enjoyed by Black. Which means that by tacking, White will - perhaps briefly, but then again, perhaps for some time - enjoy a starboard tack that is favoured by 15°. What is most likely to happen to White is that she will soon sail into Black's wind and get knocked. White then should make sure she sails well into this "new wind" (Wind 2) by waiting a few seconds before tacking onto the now favoured port tack. White will have lost distance to Black to be sure, but she has at least "stopped the bleeding" by getting her share of the goodies being enjoyed by Black. And if Wind 1 turns out to prevail for both boats, then White will have lost nothing by tacking, either.
 
More and more, I am finding that this recently digested (though supposedly "learned" long ago!!) strategy pays big dividends in situations like the one illustrated by the image just above.
 
Well, Mr. Haill, I hope this is along the lines you had in mind? I kind of like it and may add it to the WIT? Do let me know what questions this still leaves unanswered!
 
Best regards,
 
Uncle Al (W3854)
 
----- Original Message -----
From: Andrew Haill (W9657)
Sent: Friday, November 30, 2007 6:53 PM

Wow ... that's great, Al ... thanks.  Adding that to the Tactical considerations section of the WIT would be good.  Actually the WIT is another hot button to consider.

I'll have to give this some serious digestion... but I see if the wind headed both boats, the leeward one is now ahead ... Theoretically both boats will tack on the header; is there effectively any gain towards the mark? do you keep some?  ...   if for no other reason, I suppose the front boat needs to tack to consolidate this gain? Which brings up "cross em while you can".

Glad you like the knot thing... I stole that off the Thunder Bay YC site myself.
 
cheers,

Andrew


----- Original Message -----
To: Andrew Haill (W9657)
Sent: Monday, December 03, 2007 12:14 AM

Hi, Andrew:
 
Good thinking about the WIT button - done! Thanks.
 
Regarding the shifts: Over 90% of shifts are oscillating shifts, i.e. shifts that swing back and forth. So, as you say - all else being equal - both leeward/ahead and windward/astern want to tack if they are knocked. If the shifts are indeed swinging back and forth, windward/astern has only to wait for the return oscillation, and when both tack back to starboard, the boats are even again. In other words, as long as both boats stay on the favoured tack, and windward/astern doesn't let leeward/ahead cross him, he's OK.
 
 
But if w/a (Black above) holds the knocked tack, then Black is confirming l/a's (White above) gain ...
 
 
... by letting White cross, and if White likes, he can ...
 
 
... tack to windward and ahead of Black who was formerly windward/astern. Once you put a guy to leeward and astern of you, no shift can let him pass you any more. He can pass you if you hit a big dead spot or he gets a different wind, but those things are rare, and even then, can usually be managed without losing the boat astern and to leeward, if the boat ahead keeps his eyes open.
 
This of course, simplifies the situation to an America's Cup format, whereas fleet racing is far more complex. In the image above, for instance, White would be unwise to tack back onto the knocked tack unless he specifically needs to make sure he beats Black, and losing distance to other boats who play the shifts more correctly is immaterial. In any case, no one ever gets everything just right. Which is what makes racing a bit of an art form and keeps it interesting, but the underlying angles principles need to be the foundation on which one builds - a bit like learning to skate before one adds the dekes and other nifty moves in hockey.
 
About the mark: You want to think more in terms of shortening the distance you need to sail to reach the windward mark, rather than where the mark is. Marc and I tend to think of the mark only insofar as it creates lay lines, port and starboard, which - under normal circumstances - we want to avoid as long as possible. I have tried to explain the reasons for this overriding paranoia about lay lines below:
 

 
Once you hit the lay line (Black in image above) you are out of useful options if any further shifts occur. Look at the two main possibilities:
 
 
If there is a lift for your tack and you are already on the lay line (Black above), you will merely be overlaying the mark while a guy that was even with you but to leeward and ahead, i.e. short of the lay line, can - unlike the guy on the lay line - cut some distance sailed by pointing closer to the mark. Black can foot off and go a bit faster on his reach than White, but that will not make up for the extra distance Black is having to sail. Pointing up would be even worse for Black who would then not only have to sail even more extra distance but would also give up what little extra speed he might get from reaching as opposed to sailing close-hauled.
 
 
If both Black on the lay line and White to leeward and ahead get knocked (above), they can both tack. Then, under normal circumstances, a return shift brings the two boats back to even. But not if Black started on the lay line, and White was leeward and ahead below the lay line. In that case, the return shift only lets Black overlay the mark when he tacks back, and Black has wasted much of the distance that he put in after tacking on the knock. All the windward edge Black had, the edge that was keeping him even with White (leeward/ahead) is now useless, because White, after tacking back on the return shift, is now probably laying the mark and doesn't need any more windward distance. If Black chooses not to tack, he  is letting White cross him and confirm his gain. A no-win situation for Black, and most time, the best that Black, the early arrival to the lay line, can pray for is no shifts, which is the only way he won't lose. And barring pure bull shit luck, there is no way that Black will gain by having hit the lay line too soon. 
 
30° shifts are rare, to be sure, but we got those at this year's Ontarios in Ottawa, as you may recall. And of course there are exceptions to the dictum: Avoid the lay line as long as possible. I just finished writing about one that applied in Saturday's racing at the 2007 NA's at TSCC. These exceptions are usually geographic factors that cause permanent wind bends or better wind out near one lay line or the other. But those cases are rare, and can be learned fairly easily, especially by those who keep race diaries (as I used to - now I'm just too lazy - and/or busy with camera and web work). On other days, guys will hit a lay line early and make out like bandits, having gotten a different, better wind. But relying on this is like relying on the lottery. Neither pays off nearly often enough.
 
An interesting mixture of Sail the lifted tack and Avoid the lay lines can occur on a course where the windward mark is significantly skewed from being dead upwind. One such instance used to be our National Cruise Race when it was held each year (1961-1988) on Trout Lake. We would start across the lake from the McNutts' and sail our first leg of perhaps 5 miles to the very west end of the lake to a mark in Delaney Bay near where we now launch for the Poker Race. More often than not we would get a nice hiking breeze from the WSW that was spiced with the odd short stretch of a veered, more westerly wind. This long, long beat taught Julia and me a very valuable shifts and lay lines lesson which I have tried to diagram below:
 
 
Given the fact that the wind is blowing at a significant angle to the rhumb line (straight line from mark to mark), it is a given that we will spend far more time on one tack (port, in this case) than on the other. It soon became clear to Julia and me that we needed to hoard our starboard tack time if we didn't want to end up on the port lay line way too early. Most of our fellow sailors never did develop an appreciation of this crucial reality. The average guy did what Green does in the diagram above: Sail port until you're forced to tack by the shore. Since there were few shifts, starboard did not feel terribly unfavoured, and it was easy for Green to proceed past point B and on to C. Red, meanwhile, sails to hoard his starboard tack time and not spend it unless absolutely necessary. Therefore, he tacks back to port at point B, as soon as he has enough "sea" room to stay on port for another little while (how soon Red tacks back to port will depend on how much he thinks he's losing each time he tacks). By the same token, if Red meets a starboard boat, it pays for him, in such a situation, to bear away rather than to tack and pin himself in a position where he wastes minute after minute of precious starboard tack time. All this is pretty simple, if you sail with the constant mantra: Avoid starboard tack until the starboard lift comes along.
 
In the diagram, I have made the - short-lived as it always was!! - westerly shift kick in when all three boats reach point C. Until that point, Blue and Green have sailed the identical course. But here, I have made poor Blue tack just as he was about to get the starboard lift - something we've all done, and Blue should, of course, immediately tack back under normal circumstances. But I then forced Blue to stick to the knocked port tack (the Shit! We've tacked now, so that's that syndrome). Green gets his lift at point C and is naturally happy about this and continues on starboard. Just to show Red is not flawless, I have had him sail into the knock before tacking. Not too long afterwards, the westerly slant passes on through and the wind returns to its prevailing direction as the boats reach point D. Green and Red tack in textbook fashion, and remain dead even - Green being exactly as far astern of Red as he is to windward of him. But you can see that Blue is already behind Red, and therefore behind Green as well - all because he sailed on port when starboard was lifted. Red is smiling from ear to ear however - a nervous smile perhaps, because from time to time Green seems to be getting more wind and/or a major port tack lift way over there on the other side of the lake, but that was good for building our mental toughness - and it became easier as year after year, none of these boats ever did pass us as we short-tacked along the north shore.
 
In the only marginally simplified diagram above, the reason for Red's smile is that Green has now reached the port lay line and can no longer benefit from the perhaps half dozen minute-long starboard lifts that are guaranteed to come along between here and the windward mark. And each time one of those eagerly awaited shifts hits - no need to even tell Julia we're tacking, she's been waiting for the port knock as eagerly as I, Red will tack and add to our lead over Green who no longer has anything useful he can do with those starboard lifts, being on the port lay line as he is!! Of course, once Red gets closer to the mark and reaches  a point where the mark is directly upwind, he no longer has to be leery of spending his starboard tack time.
 
Actually, I have just had a revelation: Every race we sail in, has this same element that needs to be managed. The more we get out to one side or the other of a beat, i.e. the closer we get to a layline, the more our race has become what I just described above: our time remaining that we can usefully spend on one tack or the other becomes shorter and shorter as we get ever nearer to a lay line. And as that happens, we need to be more and more leery about wasting that little bit of remaining time on tack X for no good reason. The though process should go something like this: If we are not on the tack towards the lay line, good! And we won't want to be on that tack unless there is an overpowering reason to squander what little time we have left for that tack. If, God forbid, we are actually sailing towards the lay line and getting close to reaching it with significant amounts of sailing still to be done before we reach the windward mark, then we should tack right now, unless there is an overwhelming reason why we just cannot afford to!!

Getting close to the lay line at some distance from the mark should make all of us actively uncomfortable! Doing so for no justifiable reason, makes it look like one does not really know what one is doing. After a race in which I have let myself get to the layline too early, I still come in embarrassed, regardless of whether we won or lost. Even at the NA's this year, I was sure to explain that we had a good reason/excuse for banging the left corner on the Saturday.
 
Hope this helps, Andrew! I had fun creating it but it has used up all the time I was intending to put in on the Weekly Whiffle. So I think I'll throw this material in there tomorrow morning still, in preparation for its going into the WIT.
 
Take care,
 
Uncle Al (W3854)