WINDSHIFTS ... clouds and gusts.

[RichH]

WINDSHIFTS ... clouds and gusts.

Clouds – simple rule:
Always sail towards a cloud and be ‘under’ it, as ‘usually’ there will be more wind ‘directly under’ a cloud. Watch your compass to see if you get a lift or header. (Note - for water temps. above 55-60 F° only: water temp. less than 55-60 F° expect just the opposite)

Gusts = Decision time
You really have to visualize what a gust is doing as it approaches you.
When on a tack, look far ahead look to see if the gust (by its windpattern on the water) is either 1. coming straight at you, 2. moving right or 3. moving left of your ‘present’ course.

Such ‘readings’ are easy:
If you are close hauled and the gust is coming ‘straight on’, you will obviously become ‘headed’; so, the best is to tack early (and take advantage of the ‘lift’ on the opposite tack when the gust finally hits).
If on starboard and the gust is moving horizontally from the right to your left .... plan on getting a lift, so stay on the same tack and expect to ‘head up’ when the gust hits; if the gust is going from left to right, tack over to port and enjoy the lift when the gust 'hits', etc.
If on port and the gust is moving horizontally from the left to the right ..... again, a lift, so stay on the same tack, etc.
Anticipate by watching the ‘relative direction’ of the oncoming gust. Look at the surface of the water for the ‘more rough’ patterns caused by the gust and which direction the gust is 'different' from the 'base' wind.
————————————————————————————————————
Simple guidelines for GUSTS – watch the water 'ahead' of you for which way the gust is ‘moving’ relative to the ‘base’ wind.

Stb. Tack (looking straight ahead)
— Gust moving from right to left – stay on same tack and get lifted.
— Gust moving from left to right – change to port tack and get lifted.
— Gust coming straight at you, - change to port tack and get lifted.

Port Tack (looking straight ahead)
— Gust moving from left to right ---- expect a lift stay on same tack.
— Gust moving from right to left – change over to starboard tack to get a lift.
— Gust moving straight at you – change over to starboard tack to get a lift.

 

[Don Guillette]

Rich: Three great articles, which I've printed for future reference. I'm doing a sail trim seminar in FEB at Lake Havasu, AZ for a very large goup of trailer sailors (close to 100 boats) and I'm going to use your stuff at the presentation. Lake Havasu is a funny place to sail as the wind is either zero or blowing about 90 (not exactly but close) and your stuff will help these guys a gals a lot.

I hope SAIL TRIM FORUM listers apprecaite the time and effort Rich put into these 3 articles and I hope listers study and print them for future reference. Some listers may think this stuff just rolls off our fingers on the key board but believe me it ain't that easy - if you think it is simple to put these articles together just take a swing at it and see how easy it isn't. Alan, Stu and others will hopefully back me up on that fact.

Sometimes, while my wife and I are driving around Tucson, she'll ask me where in the hell is your head at because I'm off somewhere!?! I tell her I just thought of something beginners to intermediate sailors might like to know and I'm writting an article in my head. She thinks I'm nuts. I tell her to call one of her girl friend on the cell phone and leave me alone until I finish.

Rich, thanks again.

 

[OldCat]

Does this make any sense?

I hit a number of gust lines close hauled on port tack today whose character was as follows: First there was a lull and header, enough to backwind the head sail if I was slow on the tiller. Second, the gust and a lift to higher than the original course, more lift than I would expect from just the wind speed. Third, back to the original course and wind speed. The wind was SE, the gust line generally E<->W and I was sailing S. The gust line was moving slowly to the N, but much more slowly than the gust or than the average wind.

These are my observations. It all sounds a bit weird to me, the only thing that I can think of was that the wind headed UPWARDS at the wind line - but I have no idea if that is right. Clear blue ski day, nice wind. I am sailing on a mountain foothill lake and the winds are influenced by the hills around it.

I don't really know what to do with these types of gust lines, except try to follow their rhythm. So, a question: I tend to just steer though these things - only sheeting out if the gust knocks me over too far - but should I do something to power up for the lull/header, then shift gears for the gust and lift?

OC

 

[Alan]

Many skippers tend to head off in the lulls and that is a huge mistake. As the breeze drops the boat carries momentum and takes time to slow down. During this period of 'burning off' speed it is very beneficial to stay on the higher course until all the boats residual speed is used up. Sometimes this can carry through to the next puff and maintaining the higher course means making better upwind VMG than if you had fallen off with the lull. Falling off is reserved for the lull after all the speed the boat was carrying is used up.

 

[OldCat]

Many skippers tend to head off in the lulls and that is a huge mistake. As the breeze drops the boat carries momentum and takes time to slow down. During this period of 'burning off' speed it is very beneficial to stay on the higher course until all the boats residual speed is used up. Sometimes this can carry through to the next puff and maintaining the higher course means making better upwind VMG than if you had fallen off with the lull. Falling off is reserved for the lull after all the speed the boat was carrying is used up.

Does this still hold true if the lull contains a header that backwinds the head sail?

OC

 

[Alan]

OC, no, with a lull the apparent wind will shift aft seeming to create a lift. If the headsail is being backwinded you are experiencing a true wind shift. In this case you have no choice but to alter course or tack. You were probably on the right side of a puff.

 

[RichH]

OldCat -
Fall + Mountains + Weird Gusts = usually Katabatic winds, or winds of cold temperature and high density that are 'draining' from a higher elevation to a lower ... and if you are lower down in altitude the wind temperature is much warmer than higher up due to 'compression' thus a lot of random turbulence. In such a wind whichever side-valley is filling will determine the direction and the back/veer/back/normal oscillation.
That your boat on port tack first experienced a header/veer then a backing wind then another veer and then back to the base wind .... usually encountered along the Atlantic Coast in autumn or winter when the water temps are cool ... or during the height of the winter when sailing on 'real-hard' water.

Also at this time of year the northern hemisphere gets 'equinoctal' gales and winds ... a changeover from summer to winter patterns - so all bets are off as the the sequence of oscillations and which starts first a veer or a backing depending on 'which side' of the temperature gradient (summer/winter) line that you happen to be on. Also in 'equinoctal' conditions you can have a portion of the jetstream 'drop down' to low altitude ... and create all sorts of havoc.

I 'think' from your observation you stated 3 shifts before the wind came back to it base direction .... and thats the 'usual' pattern for all 'shifts' no matter from which direction they 'start' from and you have to get in 'sync' with the oscillations no matter what.

en.wikipedia.org/wiki/Foehn_wind
Also webseach for Santa Anna, Mistral, Chinook, etc.

 

[Gudenuph]

Alan
You really threw me. My experience is that when sailing into a lull, you find a velocity header until the boat slows down. Did I misunderstand???
Geohan

 

[ffaubert]

Rich: Three great articles, which I've printed for future reference. I'm doing a sail trim seminar in FEB at Lake Havasu, AZ for a very large goup of trailer sailors (close to 100 boats) and I'm going to use your stuff at the presentation. Lake Havasu is a funny place to sail as the wind is either zero or blowing about 90 (not exactly but close) and your stuff will help these guys a gals a lot.

I hope SAIL TRIM FORUM listers apprecaite the time and effort Rich put into these 3 articles and I hope listers study and print them for future reference. Some listers may think this stuff just rolls off our fingers on the key board but believe me it ain't that easy - if you think it is simple to put these articles together just take a swing at it and see how easy it isn't. Alan, Stu and others will hopefully back me up on that fact.

Sometimes, while my wife and I are driving around Tucson, she'll ask me where in the hell is your head at because I'm off somewhere!?! I tell her I just thought of something beginners to intermediate sailors might like to know and I'm writting an article in my head. She thinks I'm nuts. I tell her to call one of her girl friend on the cell phone and leave me alone until I finish.

Rich, thanks again.

This has been copied to three separate 1 terabyte hard drives, printed out and put on my boat as well as a copy in my fire-proof safe. This one (whoops, by "this one", I mean this series, sorry about that) especially deserves that treatment.

Thanks Rich, thanks Don, and thanks to everyone else who helps us newbies figure out where we're going and how to get there.

 

[RichH]

Thanks for all the kudos.

Probably the most important and most applicable for everyday sailing is the Wind Shift & Compass article - #3 of the 'series'

 

[Alan]

Geohan, what I was trying to say was do not fall off UNTIL you have burned off the the speed the boat has acquired in the puff. Only after this speed has been bleed off do you fall off to the lull and only if needed. If the puff returns you will be on the correct heading and if not you will be ahead of those who chose to follow the lull. Either way you have gained advantage over the lower course.

 

[OldCat]

I 'think' from your observation you stated 3 shifts before the wind came back to it base direction .... and thats the 'usual' pattern for all 'shifts' no matter from which direction they 'start' from and you have to get in 'sync' with the oscillations no matter what.

Yes - and so now I need to start looking at wind shifts more to see if and how they tend to follow this pattern locally. It had never occurred to me that shifts and gusts would follow any kind of 'typical' pattern - I have just tried to figure it out w/o getting the bigger picture.

Thanks,
OC