The Ocean Race 2023 leg 3: Capetown to Itajaí, Brazil


Super Anarchist
I just don't buy Team Malizia having a better downwind mode. Not after what I saw in Leg 1 and in Leg 3 shortly before the Scoring Gate when they had that 595,26 Distance Record. Kevin has some minor damage and probably has deliberately slowed the Boat down. I think it is the rough sea state that contributed to this lead.
Earlier, in the Pacific ,there was commentary about Holcim having a better downwind mode, but now TM is better. So much so that Holcim may soon need to gybe away from the coast while TM cruises along.

Sea State? I think there was a video quote just a bit back about following seas, worse for Holcim. On Thurs for most of the day it did take TM an extra 0.2 kts to make same VMC, better boat speed, worse mode, but then things blew up.
Someone must have the OBRs the day off, as there is not much "content from the boats" so far today. Either that or they are all preparing elaborate April Fool's jokes. To be fair, the boats are all a bit busy at the moment.


Super Anarchist
The Netherlands
Quick update. TM still has 230 nm to go and currently doing 20 kts = 11,5 hrs sailing. That would be 02 UTC if nothing changes. But wind will come down.

Backtesting for wx this morning shows both TM and HPRB are +/- 20 nm behind earlier projections, which is +/- 1 hr sailing with current speed.
Backtesting v3.png

Wx routing and table with latest GFS GRIB file (08Z run) shows that the ETA for Team Malizia has been pushed back accordingly to the early morning around 05Z. Will probably be earlier though as they will skip my virtual Mark 1 which I need for routing purposes.

ETA for HPRB is also further pushed back to april 2nd lunch time, after powering-up from 90 to 95% of polars (same as Team Malizia). Winds are coming down tomorrow morning from 07Z onwards from 18 kts to 3 kts from Mark 1 to the finish.

Wx routing and table new.png


Are you 100% sure?

I stated there is enough information there, not that all is needed for solution.

TWA and AWA relative to boat HDG are two angles of the wind triangle, so third is (trivially) known, yes?

BTW what is that third angle called, I don't know the word in English?

We have one length/side (TWS) of the triangle, so the two others are (trivially) known, yes?

Other sides being the AWS and SPD, yes?

Did I miss something? How can current and leeway skew a rigid triangle?

TWD and SOG can then be used to solve the remaining unknown vectors, yes, like HDG etc?

Maybe I need to draw this on a sketchpad, I did not think it through so thoroughly...
Define that rigid triangle you are talking about, when there is both current and leeway.
TWA and AWA relative to boat true course are the two angles of the wind triangle, relative to heading they are not part of any useful triangle. But if heading is known separately they can be converted.
You do not know true wind vector, so you can not add that to your boat velocity vector (magnitude=SOG, and direction= COG) to get apparent wind vector. Typically instruments assume there is no leeway and calculate true wind with that assumption, because typically heading is unknown, or only magnetic is known with very significant error margin. These IMOCAs might have gyrocompass based heading which could give correct values if used properly for conversion, but I'm not at all sure that is the case.

In real life you don't even know true wind vector, just what your instruments claim it to be, but apparent wind speed is directly measured by your wind instruments, and apparent wind direction is given by heading and apparent wind angle relative to centerline. In this example we do not have access to all those.

I'm not aware what the angle between apparent and true wind vectors is called in any language.


Super Anarchist
Holcim PRB did a wipe out Chinese gybe in 50 knots and video shows a bit of a mess fwd and water and sail coming down fwd hatch, before getting things back together. Probably now playing safe. Main down and hacksaw ... Video on their Facebook page.
There you go! A Chinese Gybe in 50 Knots of wind!!! How lucky are they not to break the Boat apart. At least they are still sailing and knowing what happened I am extremely grateful of that. Could have been much more worse.
If Holcim's inadvertent gybe, like the previous one (kudos to them for showing video of it), resulted from burying the bow, then TM's bow design will indeed have won this leg for them, fingers crossed. And given how well they competed in the light and/or upwind conditions recently, and with a full sail inventory after Itajai, barring a bizarre navigation decision like the one approaching Cape Town, they ought to lead all legs from here on.
Kevin said it was a pilot issue on both the roundup and the gybe.


Super Anarchist
Define that rigid triangle you are talking about, when there is both current and leeway.
TWA and AWA relative to boat true course are the two angles of the wind triangle, relative to heading they are not part of any useful triangle. But if heading is known separately they can be converted.

TWA and AWA are relative to the boat bow ie heading, as far as I understand, that is how they are usually defined and at least indicated by most instruments, yes (*)?

But this is not even relevant, as TWA and AWA are surely related to each other no matter how you define them and based on the same coordinate system, and thus form a triangle, where knowing both and magnitude of one of the sides makes it rigid, yes?

If TWA and AWA are based on different coordinate frame, then what is their point at all?

And our aim here was to calculate the unknown AWS.

* At least this is how I have calculated them in my DIY instrumentation for my onboard grafana/influx and they seem to agree pretty well with my onboard "real" instruments.
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