| INTERVIEW IN "SAILING ANARCHY" WITH
David Brayshaw of Local
I think there are a
lot of us who do not really understand what weather routing is. Please explain.
"weather routing" means planning a course from starting point to destination so
as to minimize the unfavorable weather conditions along the way, and maximize the
favorable. For cruisers, this could mean avoiding storms and finding a route with winds
and sea heights below a certain maximum. For sailboat racing, however, the idea is to find
the quickest route, and this usually means a course on which winds are as strong as
possible, so the boat attains its maximum speed. Boat speed also depends on the angle of
the bow to the wind, and the boat must sail more distance if it has to tack or jibe (if
the boat is heading directly into or away from the wind). In order to find the quickest
course the router must balance distance sailed with wind-dependent boat speed. If there
are currents, they too must be taken into account.
software" the basis of weather routing, and how does it work?
The speed at
which a boat can sail for a given wind speed and direction is a function of its design,
and can be obtained either from the designer or empirically, by measuring boat speed over
water (with the knotmeter) for a broad range of wind speeds and relative wind angles. This
data is often called the "boat polars." If you know the boat polars and have an
accurate wind forecast which tells you wind speed and direction at each point and time,
you can estimate how fast the boat will sail along a given route. Basically, you break
down the route into short segments, compute boat speed for each segment, at the time you
get there, and add up the times for each segment to get overall time. If you do this for a
number of possible routes, you can compare the times and determine which route is
quickest. This isn't something you can do by hand, at least not accurately and in a
reasonable period of time, which is where the software comes in. The computer is ideal for
grinding out all the possibilities in seconds and presenting the results in a way that is
easy to understand, such as plotting the optimal route overlaying an electronic chart.
The Volvo seems to
be as much a navigator's race as it is a boat speed race. What sort of electronic and
software packages are these guys (and gal) utilizing?
SF Big Boat 2001
There are two
elements to successful navigation in an ocean race. The first is the acquisition of the
latest wind forecasts and predictions of ocean current, and the second is the application
of that data in routing computations. Both wind and current forecasts must be acquired in
the form of a digital file, so the PC can read these values directly. It used to be that
these files had to be obtained before the boat sailed, which was a problem for a race as
long as the Volvo since the information becomes stale quite rapidly. In fact, wind
forecasts typically only go out 10 days, and the last few days are nowhere as accurate.
The Volvo boats all have satellite electronics that permits access to the Internet while
at sea. They can tap into websites that have these files and download them in a matter of
minutes. The boats also have one or more brands of routing software that applies the wind
and current data. My routing program is called "Force 4," and there are others
such as Deckman for Windows, Raytheon and MaxSea
You're from Frisco,
which also happens to be where Mark Rudiger is from as well. What makes Mark such a good
I have known
Mark for a number of years, and supplied him with current-prediction software for the last
Whitbread race (the predecessor to the Volvo). We have interacted quite a bit since then,
and my software development has benefited a great deal from his feedback and suggestions.
Mark has used my (then) latest version in a number of races since the Whitbread, including
the last two Fastnet races, the 2000 Bermuda race, Key West to Baltimore, Puerto Vallarta,
etc. I would say that Mark is very open-minded towards new technology and works hard at
locating and acquiring the necessary data to use it effectively. He puts in long hours
both before and during a race, and has a wealth of sailing experience to put it all in
Let's talk about Joe
Twelve Pack and his Tripp 40. He is going to do a 120-mile "overnighter". How
can software help him?
SF Big Boat 2001
wants to sail his boat as fast and effectively as possible and get to his destination
quickly, he can use routing software to determine the optimal route, lay it out over an
electronic chart and reduce it to a series of waypoints with relevant data, including time
and distance per leg, arrival time at each waypoint, average current, wind and boatspeed
per leg, etc. With "Force 4," he can simultaneously compute and display
alternative routes and compare them in terms of overall time and other factors; e.g., a
course may be a bit slower than the optimal but be simpler to navigate, not as close to
hazards or favorable for other reasons than pure boatspeed. Wind forecast files
("grib files") can be obtained free at a number of sites on the internet, and
the software will enable Joe to edit these, or even build his own models based on personal
"local knowledge." By connecting a GPS to his PC, Joe can display his boat
position and compare to the route, compute range and bearing to waypoints and monitor
measured versus predicted wind and boatspeed. He can also save his track and data for
later replay and analysis. All of this is very easy to do, even for a computer novice.
We've all seen
pictures of a boat, (Mumm 30's, even) going upwind in a buoy race with the tactician on
deck working on his laptop. A) What the hell is he most likely doing; and B) Can real
gains be made on a 1-mile beat looking at a screen instead of looking up the course?
typically don't predict wind differences over fractions of a mile, or even several miles,
so in a buoy race the tactician would be assuming constant wind and looking at other
variables, particularly current. In many racing venues there can be dramatic differences
in current strength and direction over that distance, and this can result in a significant
bias towards one side of the course or the other. This is a "routing" problem on
a small scale, but the method and potential advantages are the same. In an upwind beat
(and to a lesser extent downwind) you can pick any route to the mark between the laylines
(the point where the boat tacks to fetch the mark) without sailing any extra distance.
This is an opportunity to make gains on the competition if you get it right, and the
software incorporates a detailed model of the current and compares routes for the
tactician. Current differences can also shift and distort the laylines dramatically, and
this can be hard to judge visually. The programs tell you where the layline is, how long
before you should tack and which combination of tacks gets you the mark in the least
amount of time. For a boat like the Mumm 30 in San Francisco Bay, time differences on a
1-mile beat can amount to 4-5 minutes (a huge difference by racing standards).
Now Joe Twelve Pack
wants to join the high tech set. What's it going to cost him for weather and tactical
software? And what machine should he have?
In terms of
weather data, grib files can be obtained free from a number of websites, but it is still
costly (a couple thousand dollars) to equip a boat to access the Internet at sea. These
costs are decreasing rapidly, however, and for many races Joe could obtain a wind file
before the start that would see him through the finish. The top tactical programs cost
$1,500 to $2,000, but Joe may not need all the bells and whistles. If he is interested
solely in offshore sailing, for example, good routing programs can be found as low as $700
(e.g., the routing and wind file routines used in "Force 4" are included in
"Offchart Racer" at $695). As far as hardware goes, just about any PC you can
buy these days has enough firepower to run these programs (say Windows 98 and up, 16 megs
of RAM, 100 mhz or better). Given how fast prices are dropping, and how soon models become
obsolete, I would not pay extra for a special "marine" PC. Put a regular PC in a
plastic bag or case and buy a new one if it gets soaked or banged up.
Most folks can't
spend enough time to learn how to properly trim a headsail. How in the hell can they ever
learn how to use this sophisticated stuff?
well-written program can be very easy to use. In my routing programs you click once to
pick the starting mark (or boat position) from a list, click again to pick the destination
mark and once more to launch the computation. The results come up as different-colored
routes overlaying your chart, complete with times for each route. Click another button and
you can "step" along the routes simultaneously and see where your boat would be
on each route at a series of common intermediate times. However, there are very
significant differences in terms of ease of use, amount and quality of "help,"
examples, and other aids from program to program, as well as differences in functionality,
presentation and user interface, and so a purchaser is well-advised to ask a lot of
questions and get as much information as possible before deciding which to buy.
If you were asked to
navigate say, the Chicago to Mackinac race, how would you prepare, what would you use, and
once onboard, what would be in your Bag of Tricks?
THE DATE AND COMPARE
THE PATTERN WITH THE NEXT ONE
For Force 4
or Offchart Navigator, I would use the "Chartmaker" utility to create whatever
charts I would expect to need in the race, using free images and shoreline-utilities from
the internet. For another program, I would purchase commercial charts. I would also
acquire detailed, up-to-date paper charts for depths and detail regarding shorelines. For
a relatively short race like this, I would download a short-range wind forecast file (2-3
days). The short-range files tend to have a finer spacial resolution and more closely
spaced timepoints than the longer-range wind files (which cover more days). In a lake race
I wouldn't need current data, but in another venue I would acquire a digital current file
(a specialty of my "Local Knowledge" company). I would then start looking at
routing solutions well before the start, to get a feel for what to expect. I would also
edit the wind input, or use other recent wind files, and do more routing solutions to get
a feel for how sensitive the results are to reasonable variations in wind. I would get
updated files the night before or even the morning of the race, and have a preferred route
and some alternatives in mind before the start.
the race was on, I would monitor the actual wind measured by the instruments and compare
to the forecasts. It might be necessary to tweak the forecast file, or even construct a
custom file on the fly (my programs have a point-and-click interface to do this). Aside
from overall routing, there will be many short-distance decisions to make enroute, such as
whether the boat will be able to round a point of land on the present tack, or whether the
boat's draft will allow it to get as close to land as the computer would like. The program
will show boat position onscreen and forecast where it will be at a given time on the
present heading, which helps in these decisions. Of course, there will always be
adjustments based on localized wind conditions and what the other boats are doing - you
don't need to sail the fastest route, just get there first! Finally, having seen many
expensive boat instrument systems fail just when most needed, I will bring my own handheld
GPS and plenty of batteries, so I can at least navigate with the program and input wind
values by hand if all else fails.
What is next in the
world of navigational and tactical software?
That's a good
question! I have incorporated a number of unique functions and displays in my software,
and every user and developer has his or her own "wish list." There is no doubt
that the programs will do more each year. What is easier to predict is the availability of
good data to feed the programs. Decreasing prices for onboat equipment to access the web,
and a relaxation of the rules which until now have prohibited such access during most
races, will allow navigators to work with wind files which are constantly updated and,
perhaps, from several sources for comparison. Ocean currents can also be very important in
certain locations such as the Gulf Stream, where currents can range to 5 knots. These
currents cannot be predicted in advance in the same way that tidal currents can be
predicted, but satellite data can now be interpreted to derive current estimates which are
good for a limited period, perhaps a week or more. In the past few years I have initiated
collaborations with oceanographers to gather such data, and have developed programs to
refine it and put it in the digital form required by the tactical software. This started
with the Gulf Stream, but during the Volvo will cover currents around the world -
virtually the entire race. These predictions are reduced to files read by the programs,
and these can be emailed to navigators the night before their departure, or even at sea.
Onboard PC's will certainly improve as well, with sunlight-readable touchscreens that you
can operate at the rail.
Thanks David - See
you on the water, er lab!
welcome! Check out my daily routing and tactical analysis of the Volvo race at www.goflow.com/volvo01.htm, complete with a
viewer "navigation contest." Sign up, post a solution and see if you can best
the rockstar navigators! The next portion of the contest starts today, Oct 11, 2001.
Local Knowledge Marine Software