Pinching / Pointing

[Don Guillette]

Sinnettc brings up an interesting point on the subject of pinching. A lot of sailors complain to me that their boat doesn't point high enough. My answer is "so what" and then I go on to explain my reasoning. When you are pointing you are sailing closer to your destinatation but slower than if you foot off a bit to where you'rere sailing farther to your destination but faster. With two matched boats sailing head to head, one pointing as high as he can and the other footing off a bit, the footed off boat will eventually overtake and pass the pointed boat.

The biggest problem with trying to point as high as you can is called PINCHING. That is where you are pushing the pointing ability of your boat to the absolute max and you are within inches of stalling both the main and jib.

Next time you're on the water check out what I'm saying and you'll see what I mean.

 

[Gudenuph]

I never fail to read your posts but I can't understand the use of the word "stalling" when pinching to the max. What am I missing?
Geohan

 

[JoeWhite]

Stalling is when the sails loose lift because they loose their shape and are not pulling the boat. At this point the sails are luffing and are backwinded.

 

[Don Guillette]

gudenuph: Joe White is absolutely right. When a sail stalls you're too close to the eye of the wind. Think of every time you tack your boat. Just before you enter the "eye of the wind" your main and jib STALL and flop all over the place. You've probably seen it a million times as you tack your boat back and forth. I'm sorry I didn't explain what I ment. I always try to make things as simple to understand as I can but I missed on this example.

 

[Gudenuph]

Thanks for the clarification.
I agree, reducing the angle of attack also diminishes the lift eventually to zero. I tend to think of stall at the other extreme where increasing the angle of attack eventually causes flow separation and a sudden collapse of lift.
Your point, however, is well taken in that pinching almost never pays off.
Thanks again, Geohan

 

[sinnettc]

Pinching pays off if it keeps you from going directly downwind of Leakin' Lena, the floating outhouse!

That said, next time we're racing our former slip neighbor Tim, in his Catalina 25, back to the finish of a Beer Can I'm going to try swinging a bit further off the wind and see if I can't do a better job of beating him to the buoy.

 

[Paul Mermelstein]

If your electronics allow, see if you can display VMG (velocity made good). This is the velocity towards a particular upwind mark. As you try different angles to the wind, see how the VMG will change. At its max, that is the best angle for your boat in those conditions. Every boat is different.

 

[Don Guillette]

I was talking to a Phoenix sailor yesterday and he didn't agree with me but couldn't explain why. He just thought it didn't make sense because everyone, including him, will try to point as high as possible. To make it work we have to start with the premise that your main and jib sail trim are set up for 100% efficiency with all the telltales streaming as your sailing as high as you can. In other words, you can't have a half ass set up and expect it to work. Actually, it might work if the set of the sails stays half ass when you foot off a bit.

Additionally, when you foot off or fall off a bit you have to make a slight main and jib sail trim adjustment to compensate for the new point of sail and to get all the telltales streaming. To see if this works for you takes less than 15 minutes. Sail as high as you can - push it right up to the stall - and then back off a hair and now record your speed. Turn around and go back to your starting point. Hopefully, the wind is blowing at the same speed so you have to be quick about it. Now fall off a bit, readjust your main and jib and try it again and see if it makes any difference in your speed. The difference won't be the new land/sea speed record and a C22 won't whoop up on a C25 but you will find the fastest closehauled point of sail for your boat.

 

[Cayennita]

Even an outhouse 25 will point as well as a TP 52. It just won't go there. It will side slip of luff it's sails. The ability to go to windward is directly proportional to the draft. Bella Mente, a 66 foot racing machine has an 18 foot draft T Bulb keel. It can do 22 degrees apparent.
I race by maximizing VMG to weather. A speed of 6 knots and 30 degrees apparent will beat 7 knots and 40 degrees apparent. Do the geometry. On top of that, if the wind speed is high you can sail with the inside genoa tell tale straight up. Also you can climb to windward by scalloping the waves. Maybe only a couple of feet each wave, but in a long leg that can be significant.

 

[Alan]

It can be seen very clearly in a typical polar diagram. Having a set of polars for your boat makes choosing the right combination of boat speed vs angle of attack a no brainer.
If you look at the attached polar and draw an imaginary horizontal line across the top of the graph where it is just tangent to the curve you will have found the optimal sailing angle for the given wind speeds. Note that on a beat in 8 kts true the optimal apparent wind angle would be 32 degrees and would produce a VMG of 3.871 kts. The 'target' boat speed is the speed you should sail at to produce a VMG of 3.871 kts. That would be sailing at about 5.2 kts through the water not GPS speed. Sailing any faster means you're sailing too low and therefore too much distance. Sailing slower means you're pointing too high and giving up boat speed and again increasing the time to the next mark. Target boat speed is the best VMG to the mark.

 

[Don Guillette]

Thank you Alan. I can always count on you and RichH to give a good scientific expalation.

At the Lake Havasu Pocket Cruisers convention, many sail trim forum lister were there. A couple of them asked me if I knew you, RichH, Joe from San Diego and Stu J. I told them I never met you guys. One guy asked me if I always understood what you and RichH were saying. I told them "Nope, I really don't". I told him I read the stuff once and then have a couple of beers and read it again. Then it becomes clear to me. All the sailors in the room got a big kick out of that!!

 

[sinnettc]

Don,

Is there a way to build a set of polars without a masthead wind guage & repeater? I've looked online and haven't found a polar for the Capri 22. I've got one of those little hand held ones but it's not very accurate and I don't have the bucks for a masthead setup this year.

 

[JVB]

A sail is operates just like an airplane wing. In fact some sailboats have been built with airfoils instead of canvas sails. Here's an explanation of stalling that applies regardless of the type of airfoil or sail.
http://en.wikipedia.org/wiki/Stall_(flight)

 

[Todd Smith]

JVB,

They are using the term "stall" for a different situation than airplane folks use the term.

Don,
In most of my sailing circles, "pointing" means "best pointing for VMG". So if someone said "my boat won't point" means his boat has a hard time sailing to weather. This might be caused by boat design, lack of skill, old sails or a dirty bottom.

Telling them just to foot off might cause them to foot off 20 degrees and they might never get to weather. In Alan's polar. The best angle for pointing is about 30-35 apparent. If they try and pinch up to 25, they will lose VMG, but if they foot off too much, then they will also lose VMG.

So remember folks, the difference between "best point" and pinching and footing is small. Don't foot off too much or you will never get there.

 

[Alan]

Todd hit the nailed on the head. Sorry if my blurb is a little muddy.

Don it sounds like you fellas had a great time in Lake Havasu. I'm not a great beer fan but Capt'n Morgan will always work, though I have to tell you that Ron Zacapa is the smoothest rum I've ever had. With your sailing and racing experience I don't for one minute believe that you don't understand pointing and VMG, beers not withstanding. I'm quite sure you're a wily advisary on the race course.

 

[Don Guillette]

Todd: Maybe in some sailing circles it might mean "best pointing for VMG" but with the beginners I deal with they have no idea what VMG even is. When they tell me their boat won't point high what they mean is they are having a problem sailing as close to eye 0f the wind as they can. I hope listers noticed that I said at least 3 times to "fall off just a bit". I hope none of you beginners think I was saying to foot off to a beam reach because I didn't mean to imply that. Sorry if I misled you guys.

 

[Don Guillette]

Alan / RicH: I was just kidding with you guys. It was a great group of trailer sailors in Lake Havasu. I try to keep my talks lively so folks don't fall asleep as sail trim can be boring. When you guy's names came up I decided to have a little fun at your expense. I bill myself as a country boy / common seaman but down deep inside I know what your talking about. It was good for a big laugh and I'm doing another presentation for the Lake Pleasant Sailing Club of Phoenix, AZ this May and the joke worked so well I might bait the crowd to get them to ask it again because of the great laughs I got the first time I used it.

 

[David in Sandusky]

Luffing?

I would call pointing so high that the lead edge of the main begins to shake "luffing the main." When we were racing Sunfish in the 70's, without tell-tales, we would deliberately luff the main, and then bear off to be sure that we were in the sweet spot going to weather. Sailing with the angle of attack too high is stalling, but most of us would just say the windward tell-tales are not streaming, and point up.

 

[Alan]

Don, no worries mate, have at it !

 

[red_dolphin]

Six Degrees of Separation

I look at jib trim upwind as being one of these six states, from low to high on the wind:

• Starving the jib - If the course is proper, the jib needs to be eased.
  Otherwise, head up.
• Footing - A decision to go for speed over angle on the wind.
  I use this in light airs and/or moderate chop to maintain speed.
• Pointing - This is your 'best of all worlds' situation on a beat.
  In moderate wind and relatively flat sea, this is the 'max VMG' state.
• Pinching - The sails are still full, but the jib telltales are unhappy.
  Angle on the wind is up. but speed is off more. VMG falls.
• Luffing - The luff of the jib starts to, well, luff.
  When I sailed dinghies, the luff of the jib is what I watched.
• Head-to-Wind [and soon to be in irons] - This is important to the racing skipper.
  You are allowed to 'luff' up to head-to-wind as a tactic.
  For any skipper, recognizing when you are head to wind may be your first clue that the wind has shifted dramatically.
  That happened to us a couple of times last Saturday on a Hunter 38 racing in San Diego Bay.

As for 'stalling', I have heard that word used in two contexts:

1. Telltales on sails 'stall' when they stop flowing aft.
2. Sails 'stall' just like airplane wings.

Personally, I use the term 'stall' for telltales only, and use the terms above for the sail.
Your mileage may vary.

Red Dolphin