Swiftsure 2014

24 05 2014

The 2014 Swiftsure starts this morning. Weather looks great for the start, with things getting a bit interesting out at the entrance to the strait. There looks to be a shift to negotiate on the way home, a decision made more difficult by significant contrary currents.

There’s lots of good info posted at http://www.swiftsure.org/ for anyone interested in playing along or just following the race. Live video of the start and tracking should come online in a few hours.

76T will be shadowing Farr 40 Occam’s Razor.





17 07 2012





Griddle me this

9 12 2010

Just some pretty pictures… 7 day average windspeed, and a crop showing 3 days at higher res.





Ramblings on Routers

29 11 2010

Laughing Sally posted a question on SOL’s forum recently asking how much of a difference use of software routing makes and whether using one is a pre-requisite to winning in online sail-races. I drafted a reply, getting partway into it before completely losing track of what I had started out trying to say. Editing wasn’t going to save the response, so I moved it here… It’s still long and rambling, but at least the page format doesn’t highlight that quite so badly.

I’ll take a stab at this one. Nicely posed question.

There are several sub-classes of routing software (and I suppose routing or potential-routing SOLers):

A handful of “super-routers” are using custom software. This gives two distinct advantages – they can take into account the way SOL works, and they understand what the software is doing from the inside out. “Can” doesn’t translate to “do”…

It used to be that the big (huge?) edge was the weather. It’s well known that SOL’s weather doesn’t match up perfectly with public sources and this means that although you can use commercial software for overall strategy you shouldn’t steer by it. Two changes have erased this – brainaid is making SOL’s “grib” available, and SOL has changed the way it sources and resamples the wind. Both are very welcome! Using brain’s weather (and polars for that matter), the gap to commercial software is pretty much erased. There are some very powerful free alternatives now too.

A “perfect” router will give you a perfect solution inside the 6h update interval. This means that races that can be broken down are easier to route with certainty. If there is a waypoint before the next update both the course and arrival time can be “known”. This is maybe closest to the “they just do what the computer tells them” complaint, though a fair number of boats that “could” win these quite handily either don’t bother with this sort of race, don’t route at all in these circumstances, or only use software minimally. I guess it needs to be pointed out that inside of 6 hours the good SOTP guys are very fast as well – it’s a much simpler problem. I can intuit a short leg awfully close to the perfect track, and if you want to work things out with more precision the ideas presented in my blog will squeeze out the last tenth of a percent.

If the forecast didn’t update, there would only be one solution for every race – many boats could make a pretty decent go sailing by feel, while someone with enough ambition could work it out fully by hand. The software guys could just push a button and set some DC. If all three methods were perfectly executed (this decides many short races) the results would be near-identical. I’m pretty sure that with *really* accurate timing you could tell what software someone was using… zero difference in real life.

The fun comes when the changing nature of the weather is taken into account. Every time the weather updates a new “perfect” solution is created, and the old one becomes sub-optimal. On a small shift, a boat that that was “behind” by the old weather can get promoted. On major changes whole races can be flipped upside-down. From this viewpoint, there is little reason to sail the supposedly perfect routed track – it’s guaranteed to be wrong. If you watch some of the best sailors go toe-to-toe (oh for replay) you can see a layer of tactics/strategy at work that makes for most of the game. It can be pretty subtle, but there is constant jockeying for position, gambling when there are decent odds, hedging against loss… It really never makes sense to sail the routed solution. You can’t pass a boat that way and you can’t hold a lead either. There’s a whole lot more racing going on than might appear.

Learning how weather systems behave can have a big impact on how you use routing software. I don’t think that any of the current routers have much in the way of statistical analysis built in – they give a single solution for weather that is assumed to be fixed. Pretty crude. If you can see that a weather event 5 days off is impacting a decision in the next hour or so you need to be pretty sure that it’s a stable/predictable  before you wager too much. A random windhole in the wrong place at the wrong time can disqualify a winning line through some islands for no reason. The software doesn’t know any better. The wind we use is a pretty impressive forecast, and betting *against* the weather rarely works, but there are lots of ways to add value to the routed solution. What are the odds if you sail a little higher or lower than the calculated track? Where does that put you relative to the fleet? Some routed tracks are very risky (though fastest at the time) but going slightly wide is often almost as fast but much less volatile. The unpredictability of the weather is somewhat predictable. Google “ensemble forecast” for some fun reading. How serious to take this?

Long ocean races are particularly interesting due to the lack of accurate long range forecasts. SOL weather only goes out 7 days. It’s far more important to understand what is likely to happen when you get to the trades than what the current model says. There’s a place in all this high-tech stuff for pilot charts.

Depending on the router, identifying options may be particularly difficult. If the router presents the fastest track but there is another wildly different one that is predicted to arrive just a little later you had better take a pretty close look. Even worse are solutions that alternate between two approaches on every update. Think of some of the races we’ve had with competitive splits – the fastest boats are the ones that set a strategy and then look to the router, not the other way around.

There are a few tricks to working with gribs that routing glosses over. Everyone knows that the NOAA data doesn’t match real life perfectly (or at all!) on a small scale, but there are clues “hidden” in the nice smooth weather that are relevant to offshore sailing strategy. The solution needs to be adjusted based on the navigator’s knowledge of how weather works and what is really likely to be there. Shear lines show up as impassable walls, unsettled areas interpret as jumbled low-wind areas where they likely have squalls. If the Navigator is avoiding a 400nm stretch of ocean because the software thinks there is a phantom obstacle there he’s not doing a very good job. The situation in SOL is different in that we sail the actual forecast and that impassable wall really is impassable. It’s somewhat predictable though, and knowing how SOL works can present options that the routing is blind to.

What running routing software does do very well is relieve some of the drudge work of calculating courses. The mechanics of HOW to get from A to B can be handed off, leaving the crucial decision of WHERE B needs to be to the sailor. The “game” that the best routers are playing is not “how to negotiate this shift” but how to set up for the best possible odds vs the fleet. “How to negotiate this shift” is an important lesson that SOL offers, but it’s not a tactical decision.

Routers are very useful for setting DCs, and knowing with some certainty where your boat will be in the morning. They also make snap decisions when you don’t have time for all of the above easy. It might not be the best track, but just doing what the voices tell you won’t lead you too far astray if you’re SOLing while juggling lunches and rushing people out the door in the morning.

Finally – routers are a fantastic way to learn more about sailing and navigation. The absolute biggest advantage that learning to use a router can give is better understanding, even if you never switch it on during an online race. If you like this sort of stuff, you can play for days with different scenarios, see how different boats handle the same weather, watch how the solution evolves over time. Some of the visualisations give you a whole different outlook on the game. Plotting isochrones shows all sorts of information – the weather, polar, obstacles and course are all handily summarized. Time contours plotted backwards from the finish let you assess fleet position. Combined, you can identify areas where potential gains might be made, where it’s safe to deviate from track to try an attack, evaluate risk on laylines… Some software allows you to simultaneously display the fastest track to every point on the course – this highlights the “seams” where there are multiple options, and those are critical areas on the map.

Do you need one to win – absolutely not.

How much difference do they make? – it’s a very useful tool. There’s nothing that the software does that can’t be done by hand, but you can solve in 30s what might take hours. Using the result effectively needs skill.

Disadvantage? – qualified yes? There is a reason that software routing has become a major part of offshore racing. That said, the difference between a well-routed and a good SOTP time is usually far less than the margins of victory while the strategic stuff really adds up quickly. The fleet has boats using identical software that finish very differently, and usually with dozens of places between.

Phew… back to the discussion on SOL.





Polar Hop #1

4 05 2010

Here’s a quick one from today’s practice race. On the downwind leg from Ile d’Aix to Ile Madame, the direct line put you at a twa of 148°. Normally with no shift, the straight line is the fastest, but looking at the polar we can see that 148° is in the middle of a “dent” in the curve.

The black arrow on both the above map and the polar diagram below shows the direct line. We need to avoid that dent to sail the leg as fast as possible, so we “bridge” the gap with the two angles that are tangent on either side. In this case they work out to around 139°. and 167°. We can sail the higher angle until we reach the layline that will take us to the turn on the deeper one, shown by the pink arrows.

How much faster is it? You can find the average speed over and two directions on the polar by connecting the points with a straight line. The yellow line above bridges the “humps” on the polar (but is offset a bit for clarity) you can see that the two-angle strategy gains about a 1/3 of a knot made good. Gain on the leg is around 80 seconds or 0.16 nm!





Fastest route to the finish line

4 05 2010

This situation presented itself during one of the increasingly popular practice races that a dedicated group of SOLers are organising in the time before the official race starts. Races are arranged on the fly, and usually use some interesting courses and are of relatively short duration. Everyone is welcome to join in – it’s a good opportunity to test out setting Delayed Commands, work on boat handling and ask some questions!

In last night’s race, the finish line was defined as the beach just East of the island shown below. The length of the line and the angle of the wind made for an interesting decision at the turn – which angle will get you to the finish fastest? The shortest distance is straight to a point perpendicular to the line, a little ways above where the fleet has gathered for the next race, but sailing lower might give more speed.

One way to approach this problem is to use the steering tool to measure distances and speeds to each end of the line, and do some quick math to find out which end is favoured. (distance is shown with more precision in the upper right corner of the map window, and speed in the lower right of the polar) This works most of the time, but for long lines, the best point might be somewhere in the middle. We can use the VMC concept to pretty accurately pick the fastest angle straight from the polar diagram without any math.

In the screen capture above, I’ve laid in a line defining the finish line and extending a ways beyond the edges of the beach. The beach is angled slightly @184°. The shortest distance is to the point perpendicular to the beach, or a CC of 94° from the boat, and defines our VMC target direction. You can eyeball this angle – use the steering tool to lay in this line and the resulting TWA will be shown on the polar diagram.

The black line on the polar above is the TWA for the shortest distance, and the windcurve we’re on is the black one just outside the red 20kn line. We want to pick the point that is “furthest forward” along that line. If you visualise a line at right angles to the target direction, the point where it touches the windcurve is our fast VMC angle. If you have a small piece of card or tear the corner off a sheet of paper, you can hold it up to the screen and use it like a little set square. In the example, the solution works out to around 93°.

Use the steering tool to set your TWA to your fast angle, and if the predictor hits the beach (or the finish line) enter that course and click “send” 🙂 In this example, the landing spot is marked by the red dot in the first picture.

We can also do the math as a double-check and to see how much we stand to gain: The shortest distance option gives us a speed of 8.36 knots over 4.89 nm, while the second results in a speed of 8.77 knots over 4.98 nm. This gives us times of 35m 6s and 34m 4s. The VMC method gains just over a minute, or  0.15nm – not a lot, but more than enough to decide a race. The top 5 boats finished inside that window last night!

What if your fast VMC angle ends up missing the line? Then you target the pin at that end of the line. This is much more common.





Final Results

23 02 2010

Final results table (I think… will double check calcs) Read the rest of this entry »





Unofficially Handicapping the IMSYC Challenge 2010

11 02 2010

Massive Spoiler Warning

What follows is a quick analysis of the fleet for the 2010 edition of the IMSYC Challenge fleet race on http://www.sailonline.org. IF you want to figure out what boat will be fastest 100% on your own – PLEASE stop reading now. The info presented doesn’t identify one guaranteed winner this year, but it helps narrow the choices, and gives some extra insight on the boats and different ways to interpret the polars. The calculated handicaps give you a pretty good idea of which boats will be fast in what conditions, and how they are likely to compete with each other during the race. They also highlight some of the design decisions chosen by Jakob’s students, which are discussed in the reports available along with the polars at http://www.sailonline.org/static/imsyc_2010 .

The ratings shown are based on ORC-Club, which is described in considerable detail at http://www.orc.org. This implementation suffers somewhat in that I have not applied wind-speed smoothing, and the IMSYC rule produces slightly strange boats. Combined, this tends to lead to”rule-beater” ratings for boats designed for extremes of low or high wind. Overall though, the ratings seem to work out pretty well when software-routed finishing times are compared.

A quick breakdown of the different ratings:

GPH: General-purpose Handicap

This is a “single number” time-on-distance handicap that is probably the most familiar type. The ratings are given as seconds/mile, and time owed can be quickly figured out by subtracting your rating from another boat’s. The allowance is multiplied by the length of the course to give corrected time. In ORC, GPH is calculated using the time required for a boat to sail a circular course in 8 and 12knots of wind, giving a good general reference for overall performance. ILCGA is a TOD handicap that can be used for inshore/windward-leeward racing. It’s based on a matrix of up/downwind VMG and 110° reaching at 6, 10 and 20 knots. Lower numbers are faster.

TMF

TMF is a time-on-time representation of GPH/ILCGA. Your finishing time is multiplied by the rating to give a corrected time. Why do this? Basically, the time on distance schemes give the same time allowed for every course, so boat A needs to beat boat B by 30 minutes over a 50nm course, regardless of how long it takes to complete the course. If there is lots of wind, big fast boats get beaten on time by the little guys, and the opposite is usually the case for long slow races. Time-on-time scoring is supposed to compensate for this somewhat by including the time to finish instead of the race distance in the formula. Whether it’s *really*any better is one of the great debates of simple-system handicapping. Higher numbers are faster.

PLT-?

Club scoring rules for ORC races can use “Performance Line” scoring to try to deal with the limitations of single-number systems. The correction is based on both race distance and time, and boat performance in high or low winds is included. In theory this evens things out a bit, and makes racing more fair. It seems to work out ok in SOL, though you definitely need a calculator to figure out where you stand during the race. IMSYC-rule polars produce slightly funny looking numbers. The formula for corrected time is (PLT*Elapsed_time)-(PLD*Distance). Offshore ratings reflect boat performance over a mix biased toward windward-leeward work at low windspeed and reaching in higher speed, which seems to reflect the makeup of many courses. The inshore ratings are based on an Olympic triangle at 8 and 16 knots TWS.

OTNLOW-MED-HIG: Off(in)shore Triple Number

These are time-on-time ratings that compensate better for boat performance in different wind strength. The LOW ratings are for windspeeds below up to 9 knots and HIG(h) is above 14. You still get the same advantages to the fast/slow boats but now the spread is over a narrower wind range. This makes the rating “more accurate” but is really intended to give racers a common enemy in the guy who drew the short straw and has to choose the wind range to apply. If true wind is close to the transition, the choice of which set of ratings to apply can turn the corrected order upside-down.

The Ratings (Click to enlarge)

Discussion-Boatspeed

The IMSYC race this year is about 1100nm and will probably take about 7 days to finish, so we can use those numbers as a basis of comparison.

The boats are listed ranked by GPH, which is a reasonable “All-around” number. Windigo is rated fastest, with Uprising and Innsbruck not too far off the pace. Windigo owes Uprising ~6.7 seconds per mile, or just over two hours at the finish. That seems like a big gap, but well inside the margin for the top dozen boats on a race of this length.

Uprising has a significantly faster rating using the inshore numbers though, and is rated basically even with Innsbruck. Why the difference? Look at the polars (and read the reports) for these boats and you’ll see that they are using very similar optimisation strategies, but have chosen different wind ranges based on their research. Windigo is fast in light wind but runs out of righting moment much above 10 knots. Uprising stays on her feet a little longer. ILCGA includes 20knots windspeed in the calculation, which is enough to drop Windigo’s rating to 12th.

The “Triple Number” ratings show the story of the top boats. Windigo rates out fastest in light winds under both offshore and inshore schemes, while Uprising wins the 9-14 knot range and Innsbruck takes it in heavy winds.

The middle of the fleet is pretty even. Normandy and Andren stand out in approach a little and will benefit with light wind, while SnAILBOAT is hoping for a hurricane.

Software routing starting at no particular time gives the top five as Uprising, Innsbruck, Sunny-go, Windigo, NumberOne in around 13knots average wind.

It’s important to point out that the ratings are NOT a measure of what boat is fastest. They are an excellent indicator of how a boat will sail over the course and wind range used to produce the rating. GPH accurately predicts race outcome around a circle in 8-12knot winds, but says little to nothing about how fast a boat will get from Bodoe to Gdansk. The boats all sail fast in certain winds. You can work that out from the polars by overlaying the graphs, or you can try to work out something using the VPP. The handicap numbers are NOT software routing or anything too complex – they are basically just average speeds produced by summing one or more columns (windspeeds) or even just looking at only windward-leeward numbers from the text polars. An “in-depth” no-router approach to choosing a boat might be to pick 2 or 3 TWA and TWS that look good for the race date and do a simple comparison that way. This is the same process that many of the students used in their analysis. The ORC-Club “recipes” are just average conditions.

To illustrate the above, and reinforce the true meaning of the ratings, in a simulated rerun a few minutes ago the finish order is completely reordered: NumberOne, Innsbruck, Optimist, Sunny_go, LoveBoat… all home within 18 minutes of 1st in 15 knots wind. Windigo (fastest GPH) is nowhere close. 1 knot more wind and it’s a new game all over again!

What About Corrected-Time Results?

I’m hoping to post corrected-time rankings for this race as it progresses, using the Performance-Line (Offshore) type scoring. In simulated racing, there is a 130 hour difference between first and last, but they correct out within 10 hours of each other. The majority of the fleet is much closer – throw out the stragglers and the standard deviation is about an hour.

Which boat do you choose if you want to try for a Corrected-Time win instead of line-honours? Funny thing about handicap racing… The fastest boats don’t win that often. They destroy the fleet under the right conditions, and by the same token J-24’s can beat everyone on a good day. In SOL, where boats race true to their polars, any boat _can_ win, but the middle of the pack tends to be pretty safe. The fringes have to take their lumps with their glory. This is why everyone loves handicap racing 😛

We’ll gather for beers and griping about ratings post race. It’s traditional.





Cape Horn 50-50

5 01 2010

The run from 50 degrees South around Cape Horn and back to the starting latitude is one of the most spectacular tests of offshore sailing. It was one of the benchmarks against which the fastest Clippers were raced and remains one of the greatest sailing rites of passage. Join us as we commission SOL’s new Clipper and race “wrong-way” around the Horn!

SOL’s Clipper is modeled after the three masted “extreme clippers” built in the US, with an overall length of two hundred forty feet. These ships owned the majority of offshore sailing records for more than one hundred thirty years, only being displaced by modern purpose-designed sporting boats in the last two decades.

The polar we’re using should be pretty close, and gives virtual clipper sailors a shot at some of the old records. Performance originally fell off as the wind increased further, but this feature was eliminated to avoid confusion. In a real clipper, you didn’t expect to make way to windward in strong gale to storm conditions, and reaching was to be avoided at all costs.





Lake Superior Lights Tour

18 12 2009

Will be back to routing strategy in a bit, but for now we’d like to offer a photo-tour of Aetheria on SOL’s “Lake Superior Lights” race. This 600nm race uses some of the great lighthouses as turning marks. In order of appearance:

Wisconsin Point

Micipicoten

http://freepages.genealogy.rootsweb.ancestry.com/~pcaddict/Carpentier-Leask/Carpentier/Carpentier-Pictures/Brassar/Michipicoten_Island_Lighthouse.jpg

Caribou Island

http://marinas.com/view/lighthouse/917_Caribou_Island_Lighthouse_Wawa_ON

Stannard Rock

http://lighthouse.boatnerd.com/gallery/Superior/StannardRock.htm

Passage Island

https://www.msu.edu/user/kilpela/ir0504.jpg

Outer Island

http://picasaweb.google.com/lh/photo/ZmNieWM1THNb-qhOzFHPMA

Chequamegon Point

http://www.lighthousefriends.com/light.asp?ID=695

Ashland Breakwater

http://lighthouse.boatnerd.com/gallery/Superior/Ashland%20Breakwater.htm

All mages sourced from public domain