We first looked at Velocitek’s Prism compass in 2019 and found a lot to like: big, easy-to-read numbers, cut-acrylic lenses that allow the numbers to be easily seen in any daylight situation and not get wonky when viewed through polarized lenses, and at just under five ounces, probably the lightest small-boat compass out there.  So, when we learned a new version was in the wings, we had to see what could possibly have been improved.  

In appearance, the New Prism is identical to the original except for one detail—a USB port on the back, sealed with a half-inch diameter plug that can be screwed in or out with a coin. Out of juice after a long day on the water?  Plug it into your computer or a wall brick, and in about six hours you can go from zero to full charge. Most times, you don’t even need to be at 100 pecent since a full charge will last more than 48 hours, so you probably won’t even need six hours of charging. No more setting the compass out in the sun for hours after racing, hoping the clouds don’t roll in before it’s recharged. 

“The USB is more of a sure thing,” says Velocitek’s Charles Swanson. “Cloudy days don’t affect it, and it doesn’t matter if the compass is tucked up in the shade under the boom.”  With this setup, the solar panel is now just a battery-extending backup.  

The other big difference is inside. The New Prism now houses the same, patented, solid-state geomagnetic sensor found in Velocitek’s top-of-the-line ProStart instrument. Two big advantages of this upgrade, says Swanson. “This magneto-inductive sensor is not influenced by temperature changes and is inherently free from offset drift. This means that the factory calibration remains valid indefinitely and in all conditions. ”

More importantly, the new sensor, combined with the more powerful charging supplied by the USB connection, allows a dramatically improved refresh rate—the number of times the screen is updated—going from the earlier Prism’s once a second to four times a second. Want to see it in action? Go through a tack and watch the numbers change. Undetectable lag time.  

Ease of use?  One button positioned on top of the compass does everything. That should put a big smile on the faces of those who have struggled with multi-button processes on various other electronic devices. Press the button and the left screen says “BAT” and displays the battery level on the right screen. Shortly after, it automatically switches to compass mode. And that’s all there is to it, unless you want to set the damping mode, done by briefly pressing the button again.  Toggle through one of three damping levels by tilting the compass. This was the trickiest part of the compass to use, as you have to press the button again at the exact moment the desired damping level appears. Miss that moment and you’re probably onto another damping level. Not a big deal though, as this is something few would often adjust. Turn off the power by holding the button down for about three seconds. Easy-peasy.

For some, the one hesitation about the New Prism is the lack of a timer. The folks at Velocitek don’t apologize for that. After all, their goal was to create a straightforward, easy-to-operate, top-level compass—nothing more. Perfection embodied. And that’s just fine with a lot of sailors. For instance, in some classes, it’s impractical to have a timer and compass in one unit, such as Nacra catamarans, which mount the compass on the bowsprit, or 49ers, which carry the compass forward of the mast. That’s a pretty inconvenient reach to change modes. Others gravitate to a single-use instrument because of a reluctance to be without compass readings in the starting sequence. Yes, you can toggle between modes, but how many of us have found ourselves locked out of one mode or the other at that critical time, often because we accidentally pressed the wrong button or we held it down too long?  

This compass doesn’t meet the needs of everyone, but if you’re looking for a fail-safe instrument that will give you quick and precise readings as well as eliminate concerns about staying charged, it’s definitely worth considering. $579.

The post A Better Electronic Compass appeared first on Sailing World.

In IMOCA 60 racing, singlehanded sailors often rely on their autopilots to drive, and in the Vendée Globe, they can be the singlehander’s best friend or worst enemy.

“The pilot needs to drive the boat reliably through a full range of conditions,” says naval architect Jesse Naimark-Rowse, electronics engineer for Osprey Technical, which outfits Vendée Globe contenders such as Alex Thomson’s Hugo Boss. “On a grand-prix boat, the instruments measure heel, trim, pitch and roll rates, and have very fast GPS and compasses on top of your standard wind and boatspeed [instrumentation]. This information is calculated to allow the autopilot to steer while surfing and respond to whatever else is influencing the [boat’s] behavior.”

There are many capable autopilots on the market for recreational racers, but B&G and NKE dominate the shorthanded grand-prix market. Solid-state components and advanced algorithms can spell the difference between broaches and podium finishes.

Cutting-edge systems such as NKE’s Processor HR autopilot rely on wind sensors with fast sample rates and solid-state 3-D sensors, in addition to conventional inputs, such as rudder angle. “Our processor samples heel, pitch and roll at 25 hertz,” says Bob Congdon, NKE’s technical consultant. “The processor applies information from [the gyro sensor] and takes the boat’s motion out of the wind equation.” This is critical, he says, because vessel motion can influence an autopilot’s computed windspeed and wind. Grand-prix boats place one solid-state 3-D sensor on the hull and a second sensor at the masthead, allowing skippers to compute real-time mast twist.

However, autopilots can’t see or anticipate windshifts or off-­kilter waves and react ahead of time like a human helmsman. “From my experience in waves, particularly upwind slamming, the pilot struggles to match a good helmsman,” says Naimark-Rowse. “In flat water, a good autopilot steering to a wind angle can be so precise that it’s hard for a helmsman to match it.”

Congdon agrees. “Any condition that’s difficult for a human is hard for a computer,” he says, noting that NKE incorporated two new modes — Gust mode and Surf mode — in the Processor HR to help the autopilot compensate. “If the pilot is told to steer a course of 135 degrees true-wind angle and the computer realizes it’s in a puff, it might need to go up to 140 degrees for a moment to keep its speed up and the boat on [its] feet. The computer recognizes the conditions and reacts before a broach.”

Congdon says modern autopilots “use less power because their steering algorithms are so sophisticated, [they] don’t have to overcorrect.” While NKE autopilots provide up to 30 amps to handle the boat, Congdon says that their autopilot-steering algorithms are so accurate that they typically draw only 4 to 5 amps.

Any Vendée veteran will confirm the critical role the autopilot plays in the race. “Most Vendée skippers are hardly hand-steering these days,” says Naimark-Rowse. “The reliability of the pilots has come a long way in the past 10 years, and it only continues to improve.”  It’s important to understand, however, that some driving conditions will always be lower-percentage than others. “When a seriously fast boat [takes] off down big waves in strong wind, the risk of an accidental jibe is still a very real possibility,” says Naimark-­Rowse, “even with the best autopilot or the best helmsman driving.”

The post Autopilot Anatomy appeared first on Sailing World.

Boatspeed to Calculate True Wind Speed

With the increasing accuracy and update speeds of modern GPS units, it’s common for sailors to wonder whether using Speed Over Ground and Course Over Ground would be better than the old technology of paddlewheels and magnetic compass. In other words, is it time for us to throw away the paddlewheel and compass?

To begin with, let’s take a look at where SOG and COG come from, and if we can rely on them. SOG and COG are output from your GPS receiver. There are two methods the receiver can use to derive SOG and COG. The first and most basic is to measure the change in position from the previous fix to the present fix and calculate the speed and direction based on the time between fixes. The second, more complex and more accurate way, is to measure the Doppler shift between the received signal and the primary carrier frequency from the satellite.

Since the U.S. Government turned off Selective Availability in 2000 and WAAS was introduced in 2003, we have seen better position fixing accuracy and as a result more people using and relying on GPS. This has lead to some rapid technology advances and reduction of costs.

Until recently, most GPS receivers transmitted position, SOG, and COG data once per second, making it slow for the purposes of yacht racing. In the past five years, we have seen an increase in the number of GPS receivers on the market that output position, COG, and SOG at five times per second (5Hz). This is much more suitable for racing, especially in a starting sequence when the yacht is maneuvering a lot. Today, top-of-the-range GPS receivers, typically used for precision survey work, output data at up to 20Hz.

As this technology becomes more affordable, we will see it filter down from the America’s Cup and Volvo Ocean Race to become common on every boat. So technologically, with a fast updating GPS antenna and more accurate GPS position fixing, there’s little reason not to trust the accuracy of the SOG and COG data, but as a racing navigator we should question whether this is the correct data to be feeding into our instrument system and what impact it will have on other numbers down the line.

As their names suggest, speed over ground and course over ground are measurements related to solid ground. This means that using SOG and COG as accurate sources of speed and heading is fine if we are in a car, as we are in direct contact with the ground, but in a sailboat we have water moving independently between us and the sea bed. Even on a large freshwater lake, the water often moves compared to the ground.

If we want to be able to quantify the performance of our boat, we need to be able to measure our speed and heading through the water. This is best done with a sensor that measures water flow across the hull of the boat, such as a paddlewheel or ultrasonic speed sensor, and a sensor that measures the direction the bow of the boat is pointing in such as a magnetic compass, GPS compass, or, if the budget extends to it, a gyro compass.

If we rely on SOG as a measurement of boatspeed and we are sailing in waters with any current, we will struggle to reach our targets. With foul current, we will never reach our target boatspeed, and with favorable current we will out perform our targets, leading our crew to have little faith in the polars, the instruments, or worse still, the navigator.

Most importantly, our instrument system won’t be able to calculate accurate sailing wind. Diagram 1 shows a simplified view of how we use boatspeed to calculate True Wind Speed (TWS) and True Wind Angle (TWA), and how we can use heading to calculate the True Wind Direction (TWD).

In Diagram 2, we can see what happens if we substitute boatspeed with SOG and we are sailing in an area with current. In this instance, the favorable current is giving us a faster SOG than speed through the water, but this is reducing our TWS and shifting our TWD. In fact, we are no longer calculating our True Wind Speed, but instead our Ground Wind Speed. The same is true if we substitute heading with COG, we are no longer able to derive the TWD, but instead we can calculate the Ground Wind Direction.

Ground wind has an important use on a sailing boat, it’s the wind that blows across the land and is what’s given in your weather forecast, but it’s not the wind that we are sailing in, so tactically—and navigational—it’s of little use outside of Optimum Routing calculations.

So if we cannot use SOG and COG for boatspeed and heading what can we use them for? If we combine an accurate speed through the water and heading with SOG and COG, we are able to derive the actual effects of the current on our boat. Some instrument systems will take this data and calculate the tide set and tide rate for us, which can have tremendous tactical advantages when racing in areas with significant tidal currents, such as San Francisco.

If you’re fortunate enough to be sailing on a boat where the difference between the boatspeed and the tide rate is very large (such as a large multihull traveling at 30 knots in a 1-knot current) then it would be safe to use SOG as a replacement for boatspeed without many issues. In fact, at these high speeds, SOG is often much more accurate than a paddlewheel sensor, so it has become common practice on large multihulls to use SOG from top of the range GPS receivers as a replacement for speed through the water, especially at higher speeds.

When we are out racing around buoys, or want to be sure we can lay a headland, COG is the essential piece of information to determine whether we’re making that mark or not. It’s good practice as a navigator to note your COG on each tack while sailing to a mark or, if you are using tactical software, to run a strip chart of COG for the past 15 minutes. As an example, if we are sailing up to the starboard layline on port tack, we should know what our last starboard tack average COG was, either from our “wet notes” or a strip chart. Provided the wind has not shifted, or the current changed, this will be the number that we want to see through the hand bearing compass when we tack, though there is still a large element of good luck involved in any layline call.

The post Decoding Your Electronics Readings appeared first on Sailing World.

One challenge we all share is sailing the boat at its most efficient speed for the conditions. We’re talking target speed: a theoretically perfect number where the forward speed of the boat and the true-wind angle are optimized either into or away from the wind. Designers generate a chart of target speeds and angles for a range of windspeeds, and sailors obsess with trying to keep that number for a given windspeed locked on the speedo. The concept seems easy: sail the boat at whatever wind angle and sail trim gets you to the target speed, which should mean you’re getting to the next mark more efficiently than a competitor struggling to maintain its target. Wind and water conditions change the ease with which we reach our targets, but that’s the fun of using theory in a sport that involves nature. Theory gets you started, but every day on the water is different so adapting is critical.

Sailing to a target speed is more than matching a boatspeed to a windspeed. For a given “perfect” theoretical speed, you simply can’t ignore heel angle, wind angle, fore and aft trim, sail trim, mast rake, rudder angle, and so forth. Any one of these being out of balance can affect the rest of the equation. Part of the skill of sailing your boat well is learning how to adjust your setup for the conditions to be as close to that perfect number as you can be. First of all, windspeed may be markedly different at the top and bottom of your sails. Waves or choppy conditions also make it difficult to maintain a constant speed. Puffy conditions can cause you to be too fast against the target, then too slow, as the breeze fills and recedes. All of these dynamics, of course, make using the science of target speeds somewhat of an art form.

So let’s agree targets are in fact “moving,” depending on conditions. What’s the best way to use them? First, as with anything computed, you need quality input. Your compass must be accurate and reliable. Your speedo needs to be correctly calibrated. Then you must carefully calibrate your instruments so you’re seeing similar wind angles tack-to-tack, and similar true windspeeds upwind and downwind. If calibration is outside your skill set, enlist an expert to get everything set up right. The wind gear/compass/boatspeed relationship is vital for getting value out of your target chart.

Once you’re confident in your instrument calibration you can check in against the theoretical upwind and downwind targets. These usually come from the boat’s designer, and then they’re massaged by experience and real-world adaptation. A laminated printout may be all you need. Tape it to the companionway and use it as a guide to get a feel for what speeds you should sail based on windspeed, wind angle, and sea state. I find most inexperienced sailors tend to sail their boat too slowly (pinching), and many experienced teams go a bit too fast (pressing). Both habits inhibit your efficiency. Be careful not to live and die by the numbers, though. They are just as they’re named: targets.

Starting with upwind, let’s talk about using target speed to learn your boat. Suppose your target speed for 12 knots of windspeed is 6.7 knots. If you trim your sails and head upwind with the team hiking and everything feeling good, you should be able to get to your target number easily. The next step is to experiment with trimming the sails a little harder, maybe get the team to hike more aggressively and point a little higher while preserving your speed. It will be more difficult to consistently hold the target, but you can probably do so with greater concentration.

Any gain you make by pointing higher without sacrificing speed becomes a real bonus on race day. Using the target number to continually check in keeps you confident that you’re going well, even without another boat next to you to gauge against. Every time you’re near another similar boat, be sure to check that the target speed you’re sailing to is a good one. There are times when you will need to mentally adjust that speed up or down, and measuring against other boats is the most accurate means to confirm your adjustments.

When you hit a wave or sail into a lull, you’ll have to bear away slightly to try to recover your speed. It may take a few seconds before the speedo climbs back to that target number, even though you have more heel, more rudder angle, and the boat feels as if it has more power. That’s because you’ve lost your equilibrium and you have to make adjustments to let the boat go forward again.

Usually, all it takes to reestablish momentum is an ease of the mainsheet. If you need more, drop the traveler down a few inches. If you still can’t get to your target, ease the jib. Eventually, you’ll see the speed climb and you’ll be back at target. Once you’re there, you can trim in both sails again. It’s a continuous loop of squeezing the most height and speed from your boat, finding the edge, and easing sails to get the boat going forward again. Like a glider pilot riding the updrafts, you need enough speed to make the foils work well, but you also need to ask the boat to climb to make it upwind faster than the fleet.

Targets

It’s the same concept downwind. Speeds will fluctuate more with puffs, waves and sailing-angle changes, requiring trimmers to be more active than they would be upwind. But the concept still applies: If you sail too high and fast, you’re giving away distance to the next mark. If you’re too low and slow, you’re taking longer to get there. Knowing your targets will help you hone in on the best mode for the day, depending on the conditions, as will keeping a keen eye on similar boats, which will to tell how you’re going.

Nail the numbers

Straight-line sailing to target speed is an important skill, but one of the greatest gains you can make in a close fleet is to be more efficient through your turns. Each time you tack, jibe, or turn at a mark, the crew should be focused on getting the boat back to target speed. Knowing the number you’re aiming for and working together to trim the sails, roll, and hike the boat. Easing and then slowly increasing tension on the backstay, can make a difference to efficiently getting to speed. Losing a quarter of a boatlength less than your opponent in each tack means one length gained in a four-tack beat.

Another example is rounding the weather mark. Imagine you’re approaching, slightly overstood, in 10 knots of breeze. Your boatspeed is likely .3 to .5 knots over your upwind target. Your downwind target is likely similar to your upwind target in this windspeed. As you bear away, you’ll accelerate before reaching a downwind angle that needs the spinnaker or gennaker to maintain good speed. At that point, the boat will slow until the kite is flying. If the driver makes a smooth turn and the team hoists the downwind sail efficiently, you can fill the sail at a deep angle, before the speed has dipped below target. Then you head up slightly to sail your downwind course. Anyone who keeps reaching at the top mark may be faster, but they’re giving up lots of ground to the team that uses their momentum to get down the course. As long as you’re above the downwind target, sailing deep, below the target wind angle, should result in a gain.

Wallying: high and low modes

“Wallying” is the practice of sailing faster to the next shift, giving up slight VMG gains for the promise of greater leverage when the shift comes. Using target speed to get more out of shifts is an advanced subject, but lets cover the basics.

Upwind, if you know you’re on a lift and expect the wind to head you before layline, you can gain by sailing faster and lower toward the next shift. When the shift comes, the advantage to you will be greater than if you had sailed your normal, target-speed course. The trick is to know how much faster to go. For most boats and most shifts, something between .1 and .3 of a knot above target speed is best. The worst thing you can do is pinch to the next header.

Alternatively, there are times when your tactics require you to work the boat higher than normal, so learning your boat’s high mode is something to practice by squeezing a little more height out of the boat and learning where the speed crashes. For most boats, you can sail .2 to .4 of a knot slower to get a little better height before the mode gets too difficult to maintain and the speed crashes.

Wallying works downwind, too. When you’re sailing a header, but you’re sure you’ll get lifted before the layline, sailing slightly above target gets you to the new shift more quickly and you can use this leverage as a gain. As with a high mode upwind, a low mode is a good downwind tool. Use your target speed to see how low you can sail before the speed crashes.

The post Staying On Target appeared first on Sailing World.

When Anderson Reggio, a principal race officer, is running a regatta for 400 Optimist sailors, he says his biggest concern is “getting 400 kids off the dock, and then getting 400 smiling kids back at the end of the day.” His focus on safety keeps him up at night.

Reggio notes that the logistics at huge youth events are staggering, and most of the time there are large groups of Opti-Moms with clipboards, making checklists as sailors leave shore and return at the end of the day. The problem is the lists have to be cross-checked manually, and there is no emergency information linked to each clipboard.

Now there’s a better way. What Steve Jobs did for personal computing, past Olympian Graham Biehl and co-founder Chris Jones are doing for regatta management. Their creation, Regatta Toolbox, is a suite of software that simplifies registering for regattas, posting scores, communicating with participants, and keeping tabs on little Tommy.

It all started as a blue-sky concept Biehl pulled together when he was studying for his master’s degree in convergent media at Western Sydney University, in Australia. He was working on creating a way for competitors to scan in and out, which was still in the idea phase when he put his 29er up for sale.

The skiff sold, but Biehl wasn’t home for the arrival of the buyer, so his then-girlfriend, now-wife, sorted out the details. She spied a pile of wristbands and wires in the back of the buyer’s Land Rover.

The new owner of the 29er, Chris Jones, was working on a simple way for kids to scan onto the water and then back ashore. When Biehl’s girlfriend told him about the wristbands, he couldn’t sleep. He called Jones the next day, and the two became business partners.

“This whole thing was conceptualized in Australia because of the safety culture,” says Biehl. “The U.S. tends to sail a bit more inland. We don’t have as wild weather. Every youth event in Australia, standard practice, there has to be some sort of check-in and check-out procedure for all of the kids for insurance reasons and for contact information.”

The two partners set out to make regatta management simpler. One of their goals from the start was to make sure everything they built was 100 percent cellphone-compatible. Today, Regatta Toolbox looks and works the same on your phone as it does on your laptop, desktop computer or tablet. The product launched in Australia and enjoyed success at Sail Sydney, with 300 competitors, and at Sail Melbourne with 500 boats.

Using a scanner similar to what you might see in a grocery store, competitors scan their wristbands on the way out and when they come ashore. “Every time we have a new user for a new event, the organizers say they have never seen kids so eager to check in at the end of the day,” says Biehl. As Biehl and Jones sought to improve their product, they brought on another partner with some serious expertise. Brendan Kopp is a graduate of Harvard, a former sailing team co-captain and All-American. He also writes code.

Kopp’s goal was to make Regatta Toolbox intuitive. He doesn’t compare it to spreadsheet software; an Instagram-and-Amazon hybrid is more like it. “People are excited to move away from Excel spreadsheets,” says Kopp. “My biggest dream for this platform is to let people spend more time on the water and less time at a desk.”

When asked if it would be possible to organize and run a regatta using Regatta Toolbox while locked inside a closet with nothing but a cellphone, Kopp chuckles. “Someone would have to give me the order of the finishers,” he says. “But I could set up a regatta here in San Francisco and it could run in Australia tomorrow.”

The post A Better Way to Manage Big Fleets appeared first on Sailing World.

At the Melges 24 European Season Opener in Proto Roz, I invited multiple World Champion and Italian legend Flavio Favini to sail with me. On the first day, the wind never really filled in enough to race, so we used the time to catch up and bounce ideas off each other. One topic we talked about: electronics.

Favini and I talked about the merits, problems, and availability of having electronics on a smaller boat. Due to the drop in complexity and price over the last decade, we’ve seen an influx of electronic instruments on smaller (less than 32 feet) racing sailboats. We now even see Melges 20s with dual B&G displays, plus GPS units, such as a Velocitek. The displayed information includes boat speed, heading, heel, SOG (speed over ground), and more. That is a lot of information for a 20-foot boat!

As helpful as that information could be, however, electronics may not always be the best option. As Favini and I talked, we realized we share similar opinions. Here are our main thoughts about electronics on small boats.

In order for them to serve you well, they must work perfectly.

The amount of time I’ve spent messing around with badly functioning electronics outweighs the moments when they’ve truly been an asset during racing. So many things can go wrong: dead batteries, corrosion, lost offsets, crazy wind shear – the list goes on, and the frustration level rises.

If you are going to have electronics on board, put a team member in charge of ensuring that they function properly, are periodically calibrated, and are using fresh batteries!

Sailors start chasing target speeds.

Target speeds. These two words make me cringe when I hear them.

“How much breeze do we have?”

“About 12 knots, so according to the target speeds we should be at 6.9 knots upwind and 9.5 knots downwind.”

Target speeds have made their way down to smaller boats, but they provide trimmers, helmsman, and all of the team with a wrong sense of security (if you are easily hitting them) or insecurity (if you aren’t getting to a given target speed).

Personally, I barely glimpse at them. My target speeds for a given day all originate from the tuning I do before racing starts, which makes it really important to get on the race course early! I dedicate a good portion of my time to figuring out the actual sailing conditions (wave state starboard/port), variance in the wind direction and velocity, and tuning with a good, reliable, fast partner.

If you do have a trustworthy speedo, you can obviously consult your notes to see what speeds you were working with in similar conditions. But a slight change in sea state or wind shear can change the way you need to sail the boat at its fullest potential.

Use the target speeds only as a crude reference, but rely on your pre-start tuning and notes to truly hone in on what speeds you should be achieving for the given conditions.

Electronics can dull your instincts.

Top sailors don’t rely on electronics in order to make a boat go fast. Instead they focus on the signals the boat is giving them:

• How does the tiller feel?
• How quickly is the boat heeling?
• How is the boat pitching?
• How do the sails look and react to pressure changes?

They have a finely-tuned inner 6-axis gyroscope telling them how the boat is moving through the water. They also rely on feedback from the crew. Calling relative boat speed to the boat to windward allows changing modes as necessary. This is especially important coming off of the starting line.

Electronics dull your instincts because sailors start depending on them more than on their inner 6-axis gyroscope. It also diminishes situational awareness as focus shifts to numbers instead to the next set of waves and wind patterns.

Even considering these three factors, our biggest concern over using electronics on smaller ships…

Electronics can slow you down!

The problem with electronics is that they are always late. Every bit of information you get is delayed, and your reaction to it is even later. In order to make a boat go fast you need to be pro-active, not reactive!

Whenever I think about using electronics on a smaller ship, I picture Luke Skywalker battling the Deathstar. It wasn’t his high-tech equipment that helped destroy the Deathstar, it was the Force (his instincts), knowing his surroundings, and his abilities.

So the next time you go sailing, make it an inner-gyro day. Turn off the electronics and listen to what the boat is telling you. You might be surprised by what it has to say.

This tip is courtesy of Quantum Sails.

The post Getting Away from Electronics appeared first on Sailing World.

Volvo Ocean Race 2014-15 – Leg 7 to Lisbon

The more I sail, the more I realize that, like most everything, the best approach is a balanced one. Having said that, I think that you can ditch your instruments more often than you think — use what you know — and then use your instruments to validate your seat-of-the-pants feel and as a communication tool.

Most of us carry only one or two instruments aboard our boats — usually a compass and, if you consider a masthead fly a type of instrument, one of those as well. As you move up the technology ladder and the boats get bigger or more complex, you add a speedo and then perhaps some electronic masthead instruments. Of course, there are many more rungs on the technology ladder — the sky’s the limit — but for our purposes, we’ll stick to these basic levels.

Garbage In, Garbage Out

Blinking red lights don’t suddenly appear next to our instruments when they aren’t perfectly calibrated, and if they’re not reading correctly, we can go blindly along, following the numbers right into the back of the pack. This even occurs on some of the most sophisticated boats. I remember sailing TP52s in Spain, and being on the final approach to the weather mark. We were lifted, but once we passed the offset mark and turned down, our true wind direction told us we were headed. This happened at every windward mark for a few days, so I asked the navigator to help me figure out what was going on. We looked at our tracks overlapped on the chart, and it confirmed my feeling that something funny was happening with the instruments.

Our navigator dug deeper and discovered that our compass had a sector that was affected by something in the boat. As a result, it was inputting a heading that was 5 degrees off and changing the true wind direction solution. Luckily, because we were in a sea-breeze venue, our heading was nearly the same out of most windward marks, and we figured it out. With that said, we still missed a few opportunities for an early jibe while we were scratching our heads looking at the instruments, thinking we had missed something in all the action of the spinnaker set.

So how do you know whether your readings are accurate? At the end of the day, the most reliable guide is your heading relative to the boats around you, and how it changes as you go through lifts and headers. If the instruments say you’re getting lifted, but the boat next to you, to leeward and forward, is gaining, you might have an instrument problem. Or, conversely, if you’re the windward boat and your instruments show a big header, yet you start gaining, look to the instruments. Trust what you’re seeing with the other boats and you’ll seldom go wrong.

By knowing your tacking and jibing angles, you can also compare heading, windspeed and wind-direction numbers from tack to tack or jibe to jibe. Are you getting numbers that are consistent with what you saw on the other tack or jibe? If not, you might have a calibration issue.

When to Ignore the Compass

The compass is the most reliable tool you have. For me, it’s the go-to instrument. I never completely ditch the information it’s providing, just override it or let it take a back seat. I might do this when there are some serious geographical considerations. For instance, say I know I must get to the shoreline — perhaps there’s a big header there, or maybe more velocity. As I sail toward the shore, the compass will say we are headed, but it will pay to continue on. A similar situation occurs when one side of the course is favored because of current. It doesn’t make any difference what the compass says; I’ve got to find a way to get over there. Finally, I’ll override the compass when, just after rounding a leeward mark, I have to get to a side to avoid another fleet that’s coming down. If I followed the compass, I’d tack and end up right in the disturbed wind and waves from those boats. I take a piece of sticky-back and write down my heading and the true wind direction on both tacks and both jibes, and post this in the cockpit. For each tack and jibe, I write down my numbers for max lifted, max headed and average. This log starts in the pre-race tune-up, and I update it after any race. I’ll fill in missing numbers by using jibing or tacking angles. By having the numbers posted, you can see anomalies in your computed true wind direction. That’s my backup.

The Knotmeter Is Not God

Many people rely too heavily on the absolute boatspeed number. Most boats read differently on one tack than another because the paddle wheel is off centerline or angled slightly. As you heel, water accelerates differently around the hull. The boat may be going exactly the same speed on both tacks, but because the wheel is deeper on one side than the other, water moves more quickly past the wheel on one tack than another, and you get a higher reading on that tack. If you’re not aware of that tendency, you can spend a lot of time on the so-called “slower tack,” trying to find out what’s wrong with the rig and sails when in fact everything is set up identically, or else reaching around trying to go the same speed on both tacks.

Another common mistake is to compare boatspeed numbers to your target speed or competitors’ numbers without taking both with a grain of salt. I was sailing with a guy who was good friends with a competing skipper, and when they compared notes about upwind speed in certain conditions, my skipper discovered his numbers were a couple of tenths lower than his competition. So he started pressing the boat, always sailing a bit lower for more speed. I remember that the mainsheet trimmer and I spent an entire frustrating event trying to get him to come up. Whenever he did head up, the speed dropped a couple of tenths and our performance improved. He kept saying: “This guy said he was going 8.3. We’re only going 8.1.”

We had tuned with his friend’s boat on many occasions, and I knew this was simply a boatspeed calibration issue. I wholeheartedly believed our numbers, but our performance was suffering, and the helmsman would not listen. Finally, I had to change the boatspeed calibration so we would actually sail upwind and not reach around. The helmsman was simply focusing too much on our competitor’s numbers and not paying attention to how the boat felt. As it turned out, this was all due to a different calibration number for the speedo.

When Average Is Not Average

Imagine you’re sailing upwind, and your instruments say that 8 knots is your target speed. When you tack, the helmsman and sail trimmers will typically work to get the speed back to 8 knots on the new tack as quickly as possible. You have the bow down and the sails eased, pressing the boat to get up to 8 knots.

Once the boat reaches 8 knots, you trim on the sails and head up. But you won’t stay at 8 knots. Instead, you’ll see 8.1, 8.2 or even 8.3. The reason for this is that, usually, there’s a five- to seven-second averaging on the boatspeed. That prevents the number from jumping all over the place, which is good. But the downside is that if you actually wait until you hit that number, you’ll be too late. You tack, go down to 6 knots, and then start leaning on it to accelerate. So you could already be at 8 knots, but because the boatspeed is averaging over the past five to seven seconds, including the current value, it might read only 7.8. To avoid that problem, come up before it gets to the target number. You might need to ignore the target speed for the moment and start coming up at 7.5 or 7.6. If you don’t, you’ll end up pressing too long, and then, as you come up, the number might say 8.4. Then you’ll sail high, trying to get back to the target speed, and the up-down cycle will continue until the instruments slowly get to the right number. And that’s simply because you’re not taking into consideration that the speed is averaging when you’re looking at it. When you’re at the final angle and your sails are fully trimmed, you want to be at your target speed. If it doesn’t jump over, you’ve done it correctly.

Forget the Fly

There are certain conditions in which I typically put the least weight on masthead instruments — even masthead flies, such as a Windex — because the wind at the top of the mast is affected greatly by the sails and how they are trimmed. Sometimes these instruments just aren’t accurate, such as in a light, building sea breeze, especially when the sea breeze is slightly different from the direction of the gradient. The wind is filling in at different layers, and the instruments are not good at detecting that. It’s always worse in light air. The problem is that the instruments are just reading off the top of the rig, so you’re sailing along and look at the water and see less wind, but you look at your instruments and nothing has changed. Any time the wind weight — meaning how well it mixes from the top of the rig to the bottom — is different, it’s an issue. If you were to go up 100 feet, it might be blowing 20 knots, but that would change as you went down, depending on factors such as air temperature, water temperature and topography. It can be 20 knots up high, but it just doesn’t mix well down low. Wind sheer can also produce misleading instrument readings, particularly in light air.

We’ve all sailed downwind in light air, with a symmetric spinnaker, and discovered we couldn’t trim the pole so it was perpendicular to the Windex. That’s wind sheer: The wind is coming from a different direction at the top of the mast than it is down low. When that happens, forget the Windex and focus on correct sail trim.

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To begin with, let’s take a look at where SOG and COG come from, and if we can rely on them. SOG and COG are output from your GPS receiver. There are two methods the receiver can use to derive SOG and COG. The first and most basic is to measure the change in position from the previous fix to the present fix and calculate the speed and direction based on the time between fixes. The second, more complex and more accurate way, is to measure the Doppler shift between the received signal and the primary carrier frequency from the satellite.

Since the U.S. Government turned off Selective Availability in 2000 and WAAS was introduced in 2003, we have seen better position fixing accuracy and as a result more people using and relying on GPS. This has lead to some rapid technology advances and reduction of costs.

Until recently, most GPS receivers transmitted position, SOG, and COG data once per second, making it slow for the purposes of yacht racing. In the past five years, we have seen an increase in the number of GPS receivers on the market that output position, COG, and SOG at five times per second (5Hz). This is much more suitable for racing, especially in a starting sequence when the yacht is maneuvering a lot. Today, top-of-the-range GPS receivers, typically used for precision survey work, output data at up to 20Hz.

As this technology becomes more affordable, we will see it filter down from the America’s Cup and Volvo Ocean Race to become common on every boat. So technologically, with a fast updating GPS antenna and more accurate GPS position fixing, there’s little reason not to trust the accuracy of the SOG and COG data, but as a racing navigator we should question whether this is the correct data to be feeding into our instrument system and what impact it will have on other numbers down the line.

As their names suggest, speed over ground and course over ground are measurements related to solid ground. This means that using SOG and COG as accurate sources of speed and heading is fine if we are in a car, as we are in direct contact with the ground, but in a sailboat we have water moving independently between us and the sea bed. Even on a large freshwater lake, the water often moves compared to the ground.

If we want to be able to quantify the performance of our boat, we need to be able to measure our speed and heading through the water. This is best done with a sensor that measures water flow across the hull of the boat, such as a paddlewheel or ultrasonic speed sensor, and a sensor that measures the direction the bow of the boat is pointing in such as a magnetic compass, GPS compass, or, if the budget extends to it, a gyro compass.

If we rely on SOG as a measurement of boatspeed and we are sailing in waters with any current, we will struggle to reach our targets. With foul current, we will never reach our target boatspeed, and with favorable current we will out perform our targets, leading our crew to have little faith in the polars, the instruments, or worse still, the navigator.

Most importantly, our instrument system won’t be able to calculate accurate sailing wind. Diagram 1 shows a simplified view of how we use boatspeed to calculate True Wind Speed (TWS) and True Wind Angle (TWA), and how we can use heading to calculate the True Wind Direction (TWD).

In Diagram 2, we can see what happens if we substitute boatspeed with SOG and we are sailing in an area with current. In this instance, the favorable current is giving us a faster SOG than speed through the water, but this is reducing our TWS and shifting our TWD. In fact, we are no longer calculating our True Wind Speed, but instead our Ground Wind Speed. The same is true if we substitute heading with COG, we are no longer able to derive the TWD, but instead we can calculate the Ground Wind Direction.

Ground wind has an important use on a sailing boat, it’s the wind that blows across the land and is what’s given in your weather forecast, but it’s not the wind that we are sailing in, so tactically—and navigational—it’s of little use outside of Optimum Routing calculations.

So if we cannot use SOG and COG for boatspeed and heading what can we use them for? If we combine an accurate speed through the water and heading with SOG and COG, we are able to derive the actual effects of the current on our boat. Some instrument systems will take this data and calculate the tide set and tide rate for us, which can have tremendous tactical advantages when racing in areas with significant tidal currents, such as San Francisco.

If you’re fortunate enough to be sailing on a boat where the difference between the boatspeed and the tide rate is very large (such as a large multihull traveling at 30 knots in a 1-knot current) then it would be safe to use SOG as a replacement for boatspeed without many issues. In fact, at these high speeds, SOG is often much more accurate than a paddlewheel sensor, so it has become common practice on large multihulls to use SOG from top of the range GPS receivers as a replacement for speed through the water, especially at higher speeds.

When we are out racing around buoys, or want to be sure we can lay a headland, COG is the essential piece of information to determine whether we’re making that mark or not. It’s good practice as a navigator to note your COG on each tack while sailing to a mark or, if you are using tactical software, to run a strip chart of COG for the past 15 minutes. As an example, if we are sailing up to the starboard layline on port tack, we should know what our last starboard tack average COG was, either from our “wet notes” or a strip chart. Provided the wind has not shifted, or the current changed, this will be the number that we want to see through the hand bearing compass when we tack, though there is still a large element of good luck involved in any layline call.

Boatspeed to Calculate True Wind Speed

Using Speed Over Ground

The post What are My Electronics Telling Me About Boatspeed and Heading? appeared first on Sailing World.

The 7-inch GNX 120 and 10-inch GNX 130 have high-precision glass-bonded monochrome ultra-glow LCD displays that show over 50 marine and vessel parameters, including depth, speed, wind, and navigational data. With fully customizable user profiles, the GNX 120 and GNX 130 allow the screen layout to be configured to the user’s preferred setting. Five display configurations are available, including single, dual and triple functions, plus Gauge and Graph mode.

Easy to set up, calibrate and use thanks to the on-unit capacitive touch buttons, the GNX 120 and GNX 130 are also NMEA 2000® certified and can seamlessly share sailing data between other NMEA 2000-enabled Garmin devices. The ultra-glow anti-fog displays on the GNX 120 and GNX 130 overlay white or color digits on a black background, providing high contrast and visibility no matter the environment. If a different backlight color is desired, the display can be tailored by choosing from seven different pre-set colors, or hundreds of custom colors can be created.

Designed to be mounted at the base of the mast or above the companionway, the GNX 120 and GNX 130 instruments are the thinnest and lightest displays available in the market today. Both units can be flush mounted, and for a unique glass mast look, the GNX 120 can be flat mounted with an optional carbon fiber mast bracket. The GNX 120 and GNX 130 can be controlled from a distance using the new GNX Keypad, an optional accessory that features four different buttons dedicated to preset configurations. The GNX keypad allows sailors to adjust background lighting of all displays from the touch of a button. Another benefit of both the GNX 120 and GNX 130 is power consumption. Only .36 watts is consumed during the day with no backlight, while .4 watts is used at night when only a mid-level backlight is required. This allows for more time on the water without running the boat motor or generator for extended periods of time.

The GNX 120, expected to be available in February 2015, will have a suggested retail price of $899.99, and the GNX 130, expected to be available in May 2015, will have a suggested retail of price of $1499.99. For more information, visit www.garmin.com/marine.

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Marine radar is directional, meaning that the unit must spin so as to scan through 360 degrees. This also means that, in addition to simply measuring the distance of an object, marine radar is able to measure the direction of the object. However, caution should be observed: The design of the spinning dome makes the directional measurement (bearing) less accurate than the range measurement (distance).

The value of radar as an aid depends on the navigator’s understanding of its characteristics and limitations. Whether you’re trying to determine the range and bearing of a single competitor or trying to detect a coastline in heavy seas, knowledge of its principles and characteristics are key. There are five major functions to consider when interpreting radar images.

Resolution in range is the radar’s ability to separate close targets that are aligned on the same bearing. Traditionally, this was one of the most difficult tasks for radar to achieve. However, with Broadband and HD Radar, much of the skill in interpreting these images is eliminated. One should be mindful when using smaller conventional-pulse radar domes, however, because it’s still possible for groups of boats clustered closely together to appear on the radar screen as a single mass, or for objects close to shore to blend in with the shoreline, creating a false coastline on the radar screen.

Resolution in bearing is the radar’s ability to detect targets that are close together in range, but of slightly different bearings. As with resolution in range, modern technologies have come a long way by improving the separation of targets. An example is the “beam sharpening” feature of broadband radar, which acts like a set of binoculars on the radar beam and allows the user to focus in at a higher resolution on the bearings of interest. For traditional radar, the antenna size directly affects the beam width and hence resolution in bearing. A typical 18-inch dome used on a sailboat is relatively poor at resolving targets in this situation. Broadband technologies are not as affected by this constraint.

Antenna height is a key factor regardless of the radar technology. The higher a radar is mounted, the farther it will see, but this comes with a major compromise, as windage and weight are paramount on a raceboat. The higher the dome is mounted, the more it will be subjected to the effects of pitching and rolling, and the movement of the dome will affect the image you see on the radar screen. I hear sailors complain that their radar cannot see a container ship at 3 miles; they don’t recognize their radar is effectively pointing at the sky because it’s not level with the horizon, and it’s also being affected by pitching and rolling.

Reflection quality and target aspect should always be considered when interpreting your radar screen. Echoes from similar-sized objects can return different signals. For example, a metal object will return a much stronger signal than wood, while certain materials, such as carbon fiber, absorb more radar energy than they return, giving a weak or even non-existent return echo.

Clutter, be it atmospheric noise, sea return, or rain, complicates both radar processing and the image on the radar screen. Clutter is often strongest near your own vessel. It’s usually possible to detect clutter by watching the radar screen for several rotations. Genuine targets will appear at the same ranges and bearings on each sweep, while clutter will change randomly.

One of the greatest challenges for the navigator is determining which features on a shoreline the radar is actually acquiring, and which are clutter. This is most common with low-lying coastlines, where the shoreline may be much closer than the radar depicts. This causes a great deal of uncertainty between the radar and the chart, especially when a radar image is overlaid onto a chart. Sand spits and low beaches often do not appear on ranges greater than 1 to 2 miles because there’s little to return the radar signal. Breaking waves, however, may provide a better return signal. These could be breaking well out from the actual shoreline, which can cause further confusion with the actual position of the shore.

How can we use radar tactically while racing and not just as an aid to navigation in reduced visibility? First, it’s a great tool for tracking competitors, no matter what the conditions. In offshore races I usually do a radar sweep just before dusk to plot the competitors and then try to visually confirm these plots with a hand-bearing compass. This gives me the fleet’s “starting positions” for the evening. During the night I can make periodic sweeps to track the range and bearings of the other boats to keep up to date with which boats are making gains and losses. This can also be a great way of tracking which competitors are sailing in better breeze, provided you have some idea of the performance of the other boats around you.

Even more useful than competitor tracking, however, is the ability of the radar to identify rain and, if the radar is correctly tuned, to look through one rain cell and see the next. This allows the navigator to track weather fronts and rain clouds, which is critical tactically, especially in a race such as the Transpac where squalls can have a major effect on the outcome of the race in the latter stages.

Finally, if you have sufficient power to leave the radar scanning, MARPA (Mini Automatic Radar Plotting Aid) tracking allows the navigator to keep track of targets, be they another vessel, competitors, or rain, taking much of the labor out of the tracking of these objects.

The Automatic Identification System (AIS) is a much more recent invention, and it has become extremely popular with sailors. In fact, it’s now mandatory in many of the world’s leading offshore races.

AIS is an automatic tracking system, which shares data with nearby ships, AIS base stations, and satellites (S-AIS). The original intentions of AIS were to assist mariners in collision avoidance and allow maritime authorities to monitor vessel movements. The system makes use of a standard VHF transceiver combined with a GPS antenna (for commercial systems, rate of turn and gyro compass heading are also integrated) and identifies each vessel individually by its Maritime Mobile Service Identity (MMSI). This enables the AIS receiver to calculate navigation information such as Closest Point of Approach (CPA), Time to Closest Point of Approach (TCPA), and collision alarms for each vessel being tracked. The initial requirement for AIS was to provide a text-based list of targets, but today we see more and more AIS being integrated into chartplotter and PC software to give the user a geographical representation on a chart including alternative icons for dangerous vessels, AIS SART, units, etc.

It’s very important to remember that AIS should not be considered as a replacement for radar because not every vessel carries an AIS transponder, and those that have them do not always have the unit turned on.

As with any piece of equipment on board, particular attention should be paid to the installation of the AIS. Because the technology makes use of VHF radio frequencies, it’s subject to the same range limitations as your VHF radio. Installation of the antenna at the top of the mast is ideal to optimize range, as is the use of either a high-quality VHF antenna splitter or an independent antenna for the AIS unit. Another important consideration is the use of high-quality cable and carefully-made cable connections to minimize signal loss through the boat.

Tactically, AIS offers the racing navigator more than radar for competitor tracking, but only if the competitors have AIS and have it switched on. Class B AIS, which is most commonly found on sailing yachts, transmits the vessel’s course over ground, speed over ground, position, true heading, vessel type, and vessel dimensions. Typically this data is sent out every 30 seconds. (Class A AIS units transmit more data every 2 to 10 seconds, but these are most commonly found on commercial ships.) When trying to make use of this data, the racing navigator should remember that the data is sent every 30 seconds and is an instant data capture, not a moving average over 30 seconds, so as with radar, it pays to observe the AIS targets you are tracking and average out their performance over a sensible time period.

Miles Seddon, of the United Kingdom, worked for B&G from 2005 to 2013 before establishing himself as a consultant. While at B&G, he worked with Volvo Ocean Race (developing the electronic package for the VO65), Vendee Globe, and America’s Cup teams. He currently works with Team SCA in the Volvo Ocean Race, managing their performance analysis and instrumentation coaching.

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