Transpac Tahiti - New polars?
Post by iconPost by BooBill | 2020-05-27 | 03:20:20

This from Scuttlebutt Sailing News, referring to the VR competition replacing the actual race.

Competitors will use polar performance data from Comanche, the 100-foot current first-to-finish Barn Door Trophy champion in the 2225-mile LA-Honolulu Transpac race, because as Betz explains, “The course record of 11 days 10 hours and 13 minutes is rather old and with the right weather could be beaten by a modern fast boat of this type.”

Are we getting new polars for the 100ft Maxi? I hope so, the old ones were ridiculous. Topping out at 26knts in 20 knts of breeze.

commenticon 28 Comments
Post by iconPost by YC6211 | 2020-05-27 | 04:20:22
Either that or the polars were always based on Comanche with a cap at 26kts. Would that boat really go much faster than that in 20kts anyway? I know it's a weapon, but 26 in 20 is damn quick.
Post by iconPost by zezo | 2020-05-27 | 07:52:26
From Wikipedia:

Comanche holds the 24-hour sailing record for monohulls covering 618 nmi in the 24 hours (averaging 25.75 knots

So it should be capable of higher instantaneous speed.

Could be capped indeed so the lack of waves in the game does not let us overtake it too easy.
Post by iconPost by YC6211 | 2020-05-27 | 07:56:16
That record would have probably been set in more than 20kts. Also that's a crazy average speed. It's essentially a 24h Sydney to Hobart.
Post by iconPost by toxcct | 2020-05-27 | 07:47:48
For what I looked when the race opened, the polars used in VR will be "Super Maxi 100".
Post by iconPost by BooBill | 2020-05-27 | 10:28:05
Check the YB track of Comanche in the 2018 Sydney-Hobart race and you'll it averaging 37 knots for a period crossing the Bass Strait. Clearly, if a boat can average 25.75 across an entire ocean, it can put up 1 hour averages much higher than that.

At one time I had Stan Honey's PowerPoint explaining their entire Transatlantic record navigation strategy and planning. I'm going to see if I can find it and post it here. I'm sure that would be catnip to this crowd. It's actually what inspired me to get involved in VR.
Post by iconPost by YC6211 | 2020-05-27 | 13:14:51
That race was sailed in a lot more than 20kts though. Hell I did that race on a 46ft boat and we averaged over 20 for a few hours. Spent 48 hours running in 30-35kts with the A5 up and a big following sea. Absolute sleigh ride.

There a documentary on YouTube about their run across the Atlantic and how they waited for the one system a year that they could get across in the one front. It was a great little video.
Post by iconPost by BooBill | 2020-05-27 | 18:42:38
I'm not saying Comanche does more than 26 knots boatspeed in 20 knots true. That might even be optimistic. Here are Scallywag's polars to TW and she's only doing 24.

My problem is the VR polars have the maxi slowing down above 20 knots. As YC6211 and anyone who's sailed on or anywhere near (I've sailed ICAP Leopard btw) one of those things knows they go a hell of a lot faster than 26 knots.

I found a presentation that gives Comanche's sail polars. BTW, the x-axis is boatspeed, not windspeed, and it goes up to 32 knots. I'm guessing they are keeping the speed polars close to the chest. You can find unbelievable details of that boat's performance online, but not the actual speed polars.

So, looks like toxcct that you've checked and VR's polars match yours. That's all I wanted to make sure of. Thanks.

Post by iconPost by zezo | 2020-05-28 | 07:51:30
Amazing stuff. Thanks for the links. Should read the presentations about the Pacific right now and see what applies to this races. Is that high W of California a regular feature etc.

I'm somehow familiar with the Atlantic and Southern Ocean patterns after 10 years of virtual sailing, not so much with the Pacific

Post by iconPost by YC6211 | 2020-05-28 | 05:42:06
The IRL race requires Catalina Island to be left to port. Is that true for the VR race as well?
Post by iconPost by zezo | 2020-05-28 | 07:51:01
Nope. Only the Mataiva Atoll is defined as a mark. That's interesting as Catalina looks like the start of a big route split. The tracks would be even closer with the island left to port.

Post by iconPost by YC6211 | 2020-05-28 | 09:11:46
I've been seriously considering that route. It is so close to being prefered as a no option boat. It just seems like such a huge risk though. It only works because you follow a corridor of wind moving south in 5 days. If the forecast changes in that time you'd be screwed.
Post by iconPost by zezo | 2020-05-28 | 10:55:49
I'm probably going with the crowd this time. Lost 16 VSR points with the Madagascar experiment. But it's close.

P.S. But that high we are going around seems a bit more likely to move NW than SE?

Post by iconPost by Hardtack | 2020-05-28 | 12:05:26
Which route do you mean? I don't see a corridor but a rather stable looking wind field of ~15kn south east of Hawaii that could get us down to 8°N.

On the other hand the south route looks very unclear around 2020-06-03. We might be forced to go west or continue south at that point, neither of which looks attractive. Or the wind could stabilize in the area providing a much faster passage. Very tough decision in my opinion.
Post by iconPost by YC6211 | 2020-05-28 | 12:35:24
From the point that you turn south you're sitting on the leading edge of a pressure front that moves south with you. Because there is no wind in front of it, your speed would be limited to the speed of the front. If it moves more slowly you'd be stuck. Of course on the other hand, if it moved more quickly you'd make huge gains.

I think I'm going to go for it as this is only my second race so I don't really care about my VSR rating and I'm never going to beat people following the router with a no option boat. Plus my skipper would never go for a route like this IRL so why not do it in a virtual race?

Post by iconPost by zezo | 2020-05-28 | 12:41:43
Thanks. I can see it clearly now, at about T+102h.

I should really think of a way to animate the track/weather. At least with a simple dot moving along the track. It would make it obvious.
Post by iconPost by YC6211 | 2020-05-28 | 12:48:14
PredictWind's departure planner is the gold standard for that. Makes it super easy to the the wind you're expecting to sail in. Here I just lock on the steps at 2% zoom. Give a pretty nice overview.

btw. It feels super weird stating an LA to Tahiti race setting a course WNW. Every instinct is telling me not to do it!
Post by iconPost by zezo | 2020-05-28 | 12:58:36
As Douglas Adams put it,

"As she dabbed each tiny plastic cup into her eyes she reflected that if there was one thing life had taught her it was that there are times when you do not go back for your bag and other times when you do. It had yet to teach her to distinguish between the two types of occasion."

There are cases you should trust the router and there are cases you should not, but you never know which is which.
Post by iconPost by BooBill | 2020-05-28 | 13:29:36
I also have Stan Honey's presentation on planning for the Transpac, which talks at length about the high pressure ridge that sits between the synoptic north Pacific high and the tradewinds. Details when to go south into the trades and when to stay north. Very applicable to Tahiti as well. I'll post it a few hours after the start. Hahahahha

(seriously, I'll post it as soon as my desktop finishes doing a software update, hopefully that's before the start)

Now, I'd like to know Cvetan how you got two routes to display on the isochrones? Looks like two destinations, but how did you get them to overlay? Developer mode? I would be doing that all the time.
Post by iconPost by zezo | 2020-05-28 | 13:36:17
The presentation is there on the site.

To quote a slide called "Rules of thumb":
- Never trust rules of thumb
Then you need a pressure chart.

The picture is photoshopped. Gimp, actually. Screenshot, levels to separate the track, magic wand tool and paste into the other screenshot.

I have to investigate turning the track and isochrones to vector data (SVG) instead of images. Will make a lot of useful things possible. The site still uses about 10-year old technology, and XP and ie8 compatibility is not such a problem nowadays.

But multiple tracks are possible with server-side rendering too. It's actually the user interface part that bothers me most.

Post by iconPost by BooBill | 2020-05-28 | 13:58:01
Up and running on the desktop, but thanks Cvetan for posting the link in the meantime.
Post by iconPost by BooBill | 2020-05-28 | 14:16:27
Silly question after I've been at this almost a year, but must you cross the start line in the right direction? A southern route would have you cross the line from west to east.
Post by iconPost by zezo | 2020-05-28 | 14:22:45
There is no such thing as start line in VR. You cast off and are good to go.
Post by iconPost by BooBill | 2020-05-28 | 14:24:24
Good to know. Thanks!
Post by iconPost by Hardtack | 2020-05-28 | 17:37:19
Hah. I think the west option has become more attractive with the latest forecast. I got hull polish, pro winches and light sails and I'll follow YC6211's idea.

Post by iconPost by Shelisteam | 2020-05-29 | 07:01:48
Con anybody explain me:
I am racing very close to another yacht.
TWS, TWD,TWA are the same, both polish hull, both same sails.
and difference of speed is 0,5 kn (in dashboard of course)

Post by iconPost by zezo | 2020-05-29 | 07:08:09
Update time of the other boat?
Do you have a screenshot or another log?
Post by iconPost by Shelisteam | 2020-05-29 | 07:17:45
Time of the update is +-10 sec but I've found one more think. My speed from the top of dashboard is different to fleet list.
So wchitch one is correct to compare to others. Both in fleet tabel or my speed from the top compare to opponent from the fleet list...?
My speed on the top is 13.9 on the fleet tabel 13.3

Post by iconPost by Hardtack | 2020-05-29 | 07:27:14
Your speed in the top is updated automatically with every update from the server (usually every 5min).
The values in the fleet tab are only updated on request - when you enter a race or click on a boat in the game UI. This is true for your own boat as well. That's because the fleet tab uses the Game_GetFleet and Get_Usercard messages and the VR server does not send them automatically.

That's very confusing, I know. I should probably explain it somewhere in the manual.
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