true vs. apparent wind

[Jackdaw]

OK, I have to amend my previous post, #16, after reading Jackdaw's post. I can see the value in them when sailing downwind as the sail tell tales will be hanging down. My question: Do you put several of them at different heights on the shrouds as you would put on the sail?

If you are racing put them at every level. If you don't race then having a set at about 6 feet off the deck will be perfect for the driver and crew to monitor apparent wind direction; in particular when you are sailing off the wind.

It really comes down to how actively you trim. It's not really just a racing thing. Having them at every level allows you to see wind shear and the effects of wind gradient.

 

[weinie]

Telltales in the shrouds are vitally important when you are sailing down-wind with Spinnaker, or sailing in very light, shifty airs. Telltales on the sails tell you how to drive. Telltales of the shrouds tell you where the wind is coming from. Hugely important distinction if you want to sail fast.

If you have accurate electronics, TWA is a fantastic way to quantatively know how far up or down you can push it for a given wind speed going downwind if you also keep an eye on the speedo. For instance, if the TWA is 140 degrees, you may find you can get a half knot increase in speed by heading up to 135. Much more accuate than judging by ribbons on the shrouds.

Eta... I think for downwind VMG, knowing the TWA is more intuitive than AWA which is more useful on beats.

 

[Roland5048]

Thanks, JD, I will try that. I don't seriously race but people have told me, on more than one occasion, to relax and and quit tweaking the sails every minute. This is just going to give me one more thing to obsess about.

 

[Anonymous 121765]

Roland,

Downwind telltales are easy to read but, telltales upwind show true performance off true wind. Scott is correct,
what your telltales are telling you is, that the apparent wind across the high & low pressure sides of the sails
are the course that you are able to sail efficiently. The true wind will be different but, your stuck with your boat's layout.

This is not a bad thing what's more, your boat will fly sweet when dialed in. Who cares if it differs somewhat from true wind. You can only sail what your boat can sail.

And, you always have the option of tacking if needed. Or, you have the iron jib.......your motor.
It's all good..........

CR

 

[Anonymous 121765]

Again, I have to agree with Jack.

I constantly tweak my sails when under way, I want every bit of lift.
It sure beats trying to read a book under the circumstances.

CR

 

[Roland5048]

CR, Yes I sail by my telltales all the time. Never thought about the importance of shroud tell tales going downwind. The more info the better. Cheap and low tech at that.

 

[cb32863]

I did not install a vane with the new mast, had the wrong mount. So I added some wool yarn to my shrouds and just go off of that for wind direction. Also have my fleet flag on the back-stay and that helps too. Tell tales across my Genoa at third points for trim plus on the leach of the main. Now when I look up I am looking just at tell tales and not being concerned with a vane. Not sure if I will mount it in the off season or not....

And to quote Jackdaw "Sail trim, it's a full time job." I have finally gotten in that mode and he no longer smacks me in the back of the head when we sail together.....

 

[Parsons]

Since we have both Jackdaw's and Capt's attention on this topic, tell me about tacking angles using the difference between true and apparent. I've seen good racing skippers very accurately predict the opposite tack angles by knowing the difference between true and apparent, and knowing the other tack is the mirror image. The best I can do is add 100 degrees (or site over the winches) and hope it looks good in the other direction. More guidance?

 

[JamesG161]

She'll want to go back and take them off my boat again!

ahhhh haaaa! now we know why the Ospreys are in retreat.
Jim...

 

[Jackdaw]

I'll always have a very good idea of what angle I'll end up on, knowing my current heading and my boat's tacking angle as a function of true wind speed. About 40 true in most breeze so 80 overall.

So do that math first.

But as for the turn, there are three things good drivers do.

1) Get a sight for the other tack. Look down your traveler if that's in a good location. Across your wheel. Winch to winch. That a 90. Get a landmark (if near shore) that you want to turn your boat to.

2) Get your timing down; get used to a standard turn rate you make that your crew and keep up with and is good for the boat. Get a feel for how long that takes.

3) Develop a feel for the wind, and know what it feels like neck, ear, etc when you are at your upwind angle. Remember that moves forward as the boat comes up to speed. Get good at that and you don't have to look up!

Bonus) Use your rig tell tails and windex as needed. That's why they are there. Sanity checks! You cannot uses your sail telltails. The rig tell tails tell you the direction of the wind with respect to the BOAT. The sail telltails do not.

Use all of these things. Always match your turn to the crews ability to tack the headsail. No use getting in front of them.

 

[Scott T-Bird]

Scott,
Please don't tell my sister-in-law that. She'll want to go back and take them off my boat again!

Well, now that I know what they are useful for, I'll have to give them a try! I pay a lot of attention to the wind instrument when sailing downwind and I look at the masthead for verification, but I can see where there are differences from bottom to top. Ward, we'll have to give the spinnaker a go sometime soon, if the wind ever drops below 20 K and the temp drops below 90!

 

[thinwater]

1. If you passed high school trig you should be able to estimate true from speed, angle, and windspeed in your head. In fact, you should do this regularly if you keep instruments set to apparent, just to keep track (it's easy to forget how hard it is blowing when you are rolling downwind).
2. If anything goes wrong with the water speed paddle wheel, then the calculated "true" figures on the instrument are nonsense.
3. True has everything to do with waves and what it will feel like when sailing back up-hill, so saying it is irrelevant is misleading. To my mind, apparent wind is the artifact.

But yes, you trim by sails and ribbons. And post 30 (important if tacking using autopilot, as I often do as a singlehander).

 

[Gunni]

When I am training a driver I always give them a hand compass and the boat's tacking angle. That way they can develop a clear sense of where to point the boat on the opposite tack.

 

[thinwater]

When I am training a driver I always give them a hand compass and the boat's tacking angle. That way they can develop a clear sense of where to point the boat on the opposite tack.

Sometimes I suggest they look at the waves too (assuming they are the same direction as the wind, not deflected by land). Same idea; a visceral reference to the elements.

It's too easy to get your head buried in the cockpit instruments. Really, a new driver should not be looking at ANY instruments. The eyes should be on the waves, the wind, and the break and refilling of the jib.

 

[Roland5048]

It's too easy to get your head buried in the cockpit instruments. Really, a new driver should not be looking at ANY instruments. The eyes should be on the waves, the wind, and the break and refilling of the jib.

s

Exactly! When teaching sailing and, especially, cruising I would put my students on a compass course, (this was before GPS), and get them to focus on their surroundings, i.e. wave direction, point on land, how the breeze feels across their face, how the boat is reacting, how the sails and tell tales look, etc. 'Be The Boat' was my mantra. I would cover the compass as they would always be staring at it and not watching what was actually going on. Once they 'got it' I would uncover the compass and, lo and behold, they were still an course. It's all about situational awareness.

 

[Gunni]

We're talking about two elements of the many aspects of sailing proficiency - boat trim and direction. It is rare to find a new sailor who can maintain directional orientation against a featureless horizon. You have to give them tools or you'll find yourself correcting from a 150 degree tack rather than the preferred 90 degree tack.

 

[Jackdaw]

When I coach on a new boat, one of the first things I do is ask 'where the covers to the instruments are'. So many new owners fixated on NUMBERS, when they need to pay attention to BREEZE and boat FEEL. Stare at those $15K B&G displays for too long and I'll cover them up for the entire race. Use the numbers to validate what you feel. Not the other way around.

 

[Jackdaw]

And to quote Jackdaw "Sail trim, it's a full time job." I have finally gotten in that mode and he no longer smacks me in the back of the head when we sail together.....

True that. ;^)

 

[Roland5048]

We're talking about two elements of the many aspects of sailing proficiency - boat trim and direction. It is rare to find a new sailor who can maintain directional orientation against a featureless horizon. You have to give them tools or you'll find yourself correcting from a 150 degree tack rather than the preferred 90 degree tack.

Yes, I agree. But, if they're looking at the compass they're not looking at how the boat is coming thru the wind. We all, on occasion, except for Jackdaw, I'm sure , over or under compensate on the tack. How quickly and efficiently you recover is key. Especially when racing. Not so much day sailing or cruising. A quick look at the Windex as you come thru helps. It's all in experience and knowing your boat.

 

[Gunni]

I find it very useful to have the discussion with the new driver about what our compass bearing will be on the new tack, know the current bearing and do the math. It eliminates all that yip-yap about a "wind shift" when the driver misses his angle and starts making excuses. Just math Ma'me. New drivers should be focused on making a crisp precise tack, not getting distracted by whatever the trimmers are, or are not doing. This is how we avoid all that race boat backbiting. It is like single handing with an auto pilot - you set the tack and trim to it.