Navigating to "xxx.0" TWA
Post by iconPost by Irish Temper | 2020-04-24 | 17:06:49

Hi All,

Sorry if this has already been covered (search function would be great).

I think I've noticed a trend with some of the big name boats and so maybe it's coincidence...

When I use the dashboard and look at another top boat's TWA, a lot of the time I see: 145.0.

On my boat I'm always between .1 and .4 different. ie. 145.3

When I view the polars, the polar indicates for a given set of conditions that 145.0 TWA is the optimum. I see the good guys TWA set to 145.0. I can't get that to happen on my boat and I usually see something like 145.1 - 145.4.

Is there a way to set my boat's TWA to an exact number? Is this a reason why some boats are just sooo fast all the time because they are more often sailing the optimum angle?

Thanks in advance!

David
Irish Temper

commenticon 11 Comments
Post by iconPost by zezo | 2020-04-24 | 17:34:33
That's been already discussed somewhere on the forum.

You can do it with the programmer:

- Set a program 10 minutes ahead WITHOUT TWA lock.
- Lock the TWA
- Check resulting TWA in the dashboard
- If not proper, unlock the TWA and move the programmer a minute or few again.
- Repeat to point 2 until satisfied
- Move the programmer 10 minutes from now. TWA stays locked

Same thing works when programming your next tack. Find the spot where the TWS is integer, lock and slide the time to the correct one.


Post by iconPost by Irish Temper | 2020-04-24 | 18:43:00
Awesome! Thank you I'll give it a try. :)

Thanks for all you do!

David.
Post by iconPost by Austen | 2020-08-31 | 06:28:12
Hi David, were you successful with the TWA fine tuning? i keep trying to follow these instructions, but can't quite get it exactly right...I've managed to move a few decimal points but can't get it to stay on my desires angle...
Austen
Post by iconPost by YourMomSA | 2020-08-31 | 13:47:12
When the wind is shifting rapidly, moving the unlocked course a minute or two can move the TWA by more than 0.1 degree. So sometimes it's impossible to do it at a particular location. So sometimes you need to push the scheduled maneuver a few hours into the future, to a place where the wind isn't shifting as aggressively, do this process to get the TWA angle you want, and then bring it back to the desired time. Really annoying, particularly if you're in a hurry.
Post by iconPost by BooBill | 2020-08-31 | 14:57:06
Also, check the polars to see if it's even worth the effort. There are peaks and valleys in polars in some places, then it's clearly important to be on a peak. Sometimes it's a smooth interpolation, and wouldn't make any matterial difference. Often it's just important to be on the right side of a particular angle. Going past a max VMG number for instance will usually see a rapid fall off in speed, but being a fraction inside the angle might have an identical VMG.
Post by iconPost by Austen | 2020-09-08 | 05:40:46
thank you Mom and Bill for that assistance. Those comments both make good sense.
Post by iconPost by NumeroDixTV | 2020-12-16 | 13:58:39
Hello,
Sorry to ask again but i can't do it with consistency. Sometimes it's perfect (like .000) sometimes it doesn't work at all.

Could someone please explain again the exact pattern ?

When you say "unlock/lock twa" you mean the one from the programmer or the one we have right now ?
At the end, do you keep the programmer or do you cancel it ?

Thanks for your help!
Post by iconPost by YourMomSA | 2020-12-16 | 14:14:17
It's a royal pain. Don't expect it to be easy.

Also, when this was written, Dashboard had one decimal of accuracy. Getting to xxx.0 is realistic with some patience. Getting to xxx.000 is lunacy.

You set a programmation for the desired TWA, and confirm. Check dashboard to see what locked. If it isn't what you want, you open the programmation page, go into your scheduled move, unlock it, move it a couple minutes, re-lock it, and confirm. Then check dashboard again to see what you got. Repeat this until you get what you want. Then keep it. Your boat won't sail the desired angle until the xxx.0 programmation actually occurs.

Sometimes, the wind is shifting slowly, so you need to move by more than a couple minutes. Sometimes a lot more. Sometimes it's wavering back and forth, so after shuffling your schedule to get to .1, it goes back to .2, which can be really annoying. Other times, the wind is shifting rapidly, and moving even just one minute goes from .9 to .1. So sometimes, it's easier if you push the programmation point several hours into the future, to a place where the wind is shifting at a steady and moderate pace. Then get what you want. Then bring it back.

But also keep in mind that if often isn't worthwhile. It may be worthwhile when you'll be sailing the same VMG angle for many hours, or when you're sailing an angle that the polars show as a sharp angle where being on the wrong side causes a sudden dropoff in speed. In other cases, it isn't worth it. Also, keep in mind that the gains from this are usually tiny. One other mistake, or one unexpected sailchange, will negate days of trying to get the perfect angle.

Post by iconPost by NumeroDixTV | 2020-12-16 | 14:19:47
Thank you very much, that's more than the answer i expected :)
I gonna try again !

Edit : it works perfectly, thank you so much !
Post by iconPost by whereami | 2020-12-17 | 01:10:42
Does the "spin the compass 360 degrees" trick work for TWA like it does for HDG? (I'd test it, but I'm sailing to a waypoint right now.)
Post by iconPost by YourMomSA | 2020-12-17 | 01:21:28
No
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