Category Archives: Routing

The place for posts about weather routing, tutorials, tips and tricks.

Zigging, Zagging & Polar Hopping

One look at the course, slaloming  through all of the main islands, is enough to explain why this race is The Hawaiian Zig Zag.

SeaCart30diagram
Sea Cart 30 Polar Diagram (click for larger image)

But one look at the polar chart makes it clear that some of the zigzagging will come from avoiding the speed trough on the beam when the wind is in single digits.

Light airs are common in the channels between the islands.  The tradewinds blow in from the east, but split when they encounter Hawaii’s volcanic mountains.

Mauna Kea and Mauna Loa, on The Big Island, extend 13,784ft and 13,680 ft respectively above sea level.  Add in 10,025ft Halealeka on Maui and you get quite a wind shadow.  The combination of the slalom course, the lumpy polar, and light airs made for active skippering.  

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Two Halves

Like a game of Association Football, there is more than an element of luck involved in doing well in a virtual ocean race on SOL. And this element of luck is certainly borne out by my results so far in the SWR 14-15: 75, 287, 47, 9, 52 and now p2!

BonknDikBut if you indulge me in the conceit that I know what I am doing, shared by many football managers, for example like my fellow Haagenees who bankrupted Rangers pursuing glory, and is now certain that he will have saved Sunderland if they stay up, I will tell you the tale of how:

We followed the swings of the wind;
A struggle that seemed without end.
To starboard or port?
Well South, but not North!
To our monitors we were all pinned.

(from) Mouthansar

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Around the Bend on the Bay of Biscay

WindContoursAtStart
The course — with winds at starting time

At first glance, this race looked to be a simple reach up the coast.  At least that is how it would be if the initial winds held.

Yes, there was an island to deal with near the finish.  But odds were we would leave the island to starboard — problem solved.  This race seemed to be routine.

But as the ‘Mad Russian‘ character from Jack Benny’s radio show would have said, “Silly Boy!” The race was far from routine.

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Blown Away by Hi-Res Winds!

When Andrea [ita10267] first suggested that we could race with winds forecast in high resolution I was blown away.  I believed the potential benefit from such winds to SOL and SOLers would be immense — at least in theory.

Starting Route
Route at the start.

But would we be able to see the difference in the winds?

Would the winning routes be different from those sailed with lower resolution winds?

And how would the high resolution winds work with routing software?

Time to put theory into practice.

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Thoughts on how to not hit islands

cargados

Hitting islands is an easy and entirely too common way to ruin your race. The best SOLers do it once in a while. And of course there was the much talked about Vestas grounding. So how do we avoid this?

First off, no, Team Vestas were not taking any ‘risks’. To hit a fairly wide reef right in the middle, they had to be blissfully unaware of the obstacle.

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Blind Strategies

dingo_rhumbBy ‘blind’ I mean that we’re not looking at the actual forecast, these are basic strategies that do have value in the right situation.

1. The rhumbline
The shortest distance between two points is a line. Point at your waypoint, go max VMG if needed.Pros: you get to your destination eventually.

It’s the shortest route, sort of.
Sometimes the fastest route, if only by accident.

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