The ‘Doppler’ Windshift Effect – by David Dellenbaugh



On a beat, the speed at which you converge with shifts (and puffs) is roughly equal to the sum of the wind speed plus your VMG to windward. In this case, that’s 10 (windspeed) plus 5 (VMG), or 15 knots. But on a run, the convergence speed is the wind speed minus your VMG to leeward. Here it’s 4 knots (10 minus 6). So on a run the shifts are coming at you several times more slowly than on a beat, so you will experience that many fewer shifts.

We all know what happens when a train comes toward us at full speed with its horn blowing, at first the sound is very high pitched, but it drops quickly as the train passes by and becomes quite low-pitched while the train speeds away.

The reason for this is what’s called the Doppler effect. The sound waves in front of the train are compressed very close together, which results in a higher pitch. Behind the train, the sound waves are much farther apart, resulting in a dramatically lower pitch.

The Doppler effect is a useful analogy for what happens on a windward-leeward course. When you sail upwind, it’s like being on the front of the train, since you are sailing toward the wind, you will get the shifts and puffs at a faster rate than if you were sitting in an anchored boat.

Conversely, on a run you are sailing away from the wind, so you get the shifts and puffs at a slower rate, that’s like what happens after the train passes the point where you are standing.

Though you won’t hear any changes in pitch when you go from beating to running, you may notice some subtle changes in the wind. To illustrate this, let’s consider an example, suppose you are sailing around on the starting line and you find that the wind is oscillating every five minutes.

As you sail up the first beat, will the shifts come at you at the same rate?

The answer is no. Since you are sailing towards the shifts, you will get them faster, perhaps every three or four minutes.

How about when you round the windward mark and sail down the run?

Since you are sailing away from the shifts, you will get them less often, perhaps every 7 or 8 minutes!

The strategic implications of this phenomenon are significant. For example, if there are 8 minutes between shifts when you are sailing downwind, it is possible you will only see one shift on the run and if you get only one shift on the run, it means you should treat that as a persistent shift even though the overall wind pattern is oscillating.

The ‘Doppler’ wind shift effect also explains why better pressure is so critical downwind. Since you are sailing with the wind, you won’t see so many puffs, but you can stay in one much longer than on the beats, therefore, getting into the puff and using it fully is critical for optimum performance.

On a beat, the speed at which you converge with shifts (and puffs) is roughly equal to the sum of the wind speed plus your VMG to windward.

In this case, that’s 10 (windspeed) plus 5 (VMG), or 15 knots. But on a run, the convergence speed is the wind speed minus your VMG to leeward. Here it’s 4 knots (10 minus 6). So on a run, the shifts are coming at you several times more slowly than on a beat, so you will experience that many fewer shifts.

Dave publishes the newsletter Speed & Smarts. For a subscription go to www.speedandsmarts.com 

Prepare to Race

On the morning of the race, you will check the local forecast again to see how the predicted weather has changed or whether it is behaving as has been forecast.

Get out on the course at least 60 minutes before the posted start time and sail as much of the first beat as you can, making mental notes of the wind patterns to establish which side of the course appears favoured and whether the wind shifts are oscillating or persistent.

Compare what you are seeing with what has been predicted and start to make your plan for the first windward leg, the main advantage of doing this is that if immediately after the start something changes, you will have the information to make a snap decision about whether to continue standing on or whether to tack.

Whilst sailing the first leg prior to the start you can establish whether your setting for the rig, sails and sheeting positions are correct (these would have been set initially prior to leaving the beach based on information available at that time)

Check that the current at different points on the racecourse matches with what you know about this venue from previous regattas or local knowledge research.

Even the best sailors benefit from lining up against another competitor prior to the start and many of us have a tuning partner but if you are at a regatta and your regular mate is not there, work out who might be beneficial to work with and approach them about the possibility.

So many questions can be answered by positioning your boat two lengths from a competitor and speed testing. These tests can and should be lined up in advance with a reliable competitor whose speed and abilities are known and someone you know will show up on time at the designated spot.

Almost always prioritize tactical and boatspeed research over boat-handling practice, you are not likely to solve bigger boat-handling issues in the short period of time that is available to you.

Finally, allow an 8 to 10 minute chill period before the start, and during this time discuss the upcoming race in a low-stress manner giving the team an opportunity to re-evaluate sail selection, and then to fuel up and hydrate.

You are now ready to tackle any eventuality after the gun goes and to make a snap informed tactical decision when something that was not predicted occurs.

 

 

Left or Right?

This is probably the most asked question in yacht racing, going fast is super important but it is no good being the fastest boat out there if you are going fast the wrong way.

That’s why, no matter how fast you are, you must consider whether you want to go left or right.

When racing, we must employ strategy and strategy is the plan you employ for getting to the next mark as quickly as possible.

A strategy is a plan that takes account of things like wind direction and strength, current, waves and the position of the next mark.

These factors are different every time you go out on the water and they change constantly while you are racing and often vary across the course as a result, the difference between going left and going right can be huge.

On the first beat, you must work hard to take advantage of changes in both wind direction and wind velocity, current and the geometry of the course. The existence or absence of waves is another factor you should consider, but this does not often make a big difference.

Before you can actually plan a strategy, you must observe the racecourse and collect a bunch of helpful information including data about wind and current and do this before you leave the beach. Look up weather forecasts and current charts and don’t forget to tap into the local knowledge of other sailors.

Get out to the course area early and start looking around and make observations about what is actually happening on the course, it may not be exactly what was predicted. After the race starts, don’t stop thinking about strategy, the wind and current are always changing. An added dimension is that now you have many other boats to help you see which side of the course is really favoured.

The best way to plan your strategy would be to view the racecourse from overhead but since that is not possible while racing, you must keep your head “out of the boat” and focus on the big picture.

Your strategic plan could be as simple as, “Hit the left side hard”  or it might be more detailed, like “Start 1/3 of the way down from  the RC boat and play the oscillating shifts up the middle right  side.”

Don’t forget to keep re-thinking your strategy during the race as you will be constantly getting more information about the wind and other strategic factors. 

It is not always obvious which side of the course is favoured and there will be times when you’ll have no idea whether to go left or right and in fact, even the best sailors don’t have a strong feeling about which way to go on the first beat in as many as 50% of the races they sail.

When this happens, what should you do?

Unless you’re sure the right or left side is favoured,  stay near the middle of the fleet and keep your eyes open, the beginning of the first beat is a great time for seeing what the wind is doing and which side is paying off.

Once you get some clues about which boats are gaining, head that way quickly. Of course, you will probably come out behind the boats that sailed straight to the favoured side but you took much less of a  risk than they did, and hopefully, you will still be in the top group at the first mark.

If you can do this every race, you’ll be successful. 

Sailing Specific Fitness

 

I have summarised below some of the nuggets that I read in Michael Blackburn’s excellent book “Sail Fitter” and I highly recommend that if you are serious about getting faster on the race track your fitness is one of the major factors that will influence your results.

Michael’s book is full of excellent advice and training tips from a qualified person, not only qualified academically but with proven on the race-track achievements.

Be Adaptable – If you turn up to go sailing for a heavy air workout in your boat and the day turns out to be a drifter, cancel sailing and hit the gym. If you do end up sailing, follow up with a hard gym session working on the muscle groups that would have copped a hammering if you had sailed in strong conditions.

If you have scheduled a gym session and you turn up in not-so-good condition such as lingering fatigue then you might reduce the volume and/or intensity of the session.

Recovery – Use ice and cold water recovery practices and remember that you don’t get fitter from training until you get a chance to rest and let the body rebound.

You can recover faster for your next training session using recovery strategies like cold water immersion.

Develop Your Back – The back is the part of the body that sees the most injuries for sailors. 

An important part of your fitness training is to include exercises for the lower back and deep abdominal muscles and you should try to do something with each of these muscle groups every day.

Shoulders – These are the sailors next most problematic and injured body part and it is the sudden movements of the arms over a large range of motion that will affect your shoulder joints. 

If you have a weakness in this area or simply want to assist your body and to prevent injuries, sailors should include shoulder stabilisation exercises. Michaels book or YouTube are two great sources of these type of exercises.

Hip Flexors – Because of the way we sit in our boats, the hip flexors are in a shortened state. At the end of the sailing session you need to engage in stretches, this will help the muscles recover, help in reducing lower back issues and help improve your posture.

Equipment – To assist with hiking, consider battened hiking pants, these will enhance your endurance. Grip on the boat with appropriate materials will enable you to move without slipping and sliding and the same goes for having good gloves, effective soles on your boots and a wetsuit with nonslip and kneepads.

A sometimes overlooked fact is that hot muscles are less efficient so correct clothing for the prevailing conditions need to ensure that muscles stay cool.

Be Scientific –  Keep records of your fitness the aim being to find out by trial and error what works and what doesn’t. Body weight is something you should keep an eye on the long term and many classes have an optimum weight or weight range.

Keep a spreadsheet or notebook with exercises and food programs. It is sometimes helpful to look back over the years gone by to see what you have done by way of food and exercise to achieve different results.

Many elite sailors have records stretching back over 10 or more years.

Hiking Exercises – A Swiss Ball makes an excellent hiking bench to train your legs and work on your abdominals. This is a particularly useful exercise if you have had a number of light days and keeps your muscles in peak condition for the next blow.

Better Technique – Michael says that you are better off hiking at 90% rather than if by hiking at 100% you end up fatigued and thus your ability to steer, trim and decide tactics becomes compromised.

What you lose in righting moment you gain in these other areas.

 

Sailing Fast In Light Air

 

Although light air sailing is far from most sailors favourite conditions, it does provide the greatest number of opportunities to make the biggest gains.

A well-sailed boat can develop a great speed advantage and at times it can go literally twice as fast as its competitors – so it is not unusual to see the largest race-winning leads developed in the lightest of conditions.

Boat preparation can also play a much more significant role in the improvement in position on the race track, things like removing any extraneous weight, cleaning and polishing the bottom, taking unneeded purchases out of sheeting systems and using the lightest possible sheets to enable sails to set in the smallest puffs of breeze.

UPWIND

Good telltales are essential to enable you to set draught and twist plus an effective masthead wind indicator, wool tufts on the shrouds work well and I have even seen boats that have taped incense sticks to the shrouds, they burn very slowly and provide a smoke trail to show wind direction.

In most cases in light air, a flatter sail performs best because it allows the airflow to remain attached to the sail. In the case of the mainsail, a firm outhaul will flatten the lower section of the main whilst allowing the leech to be more open. Prebend the mast to flatten out the entry to the mainsail and the Cunningham and vang should be completely slack.

At no time should the leech of the main be angled farther to weather than parallel to the centreline of the boat. In drifting conditions, the technique of trimming the upper batten parallel to the boom is dropped, and the upper batten is set parallel to the centreline.

The traveller is sometimes pulled all the way to weather in super light conditions so that the slightest puff will allow the boom to lift easily, but as the breeze picks up, drop the traveller down again so the boom stays at or below the centreline while you are trimming the upper batten parallel to the boom. 

There isn’t anything slower in light air than having backwind at the luff of the main. With the main angled far off the centreline, the slot is in danger of being closed so to avoid this, flatten the mainsail, this lets you ease the main until the upper batten is parallel to the centreline without backwind. 

In light conditions, the jib should become increasingly full in its forward sections. If you are sailing a one-design that uses the same jib in 0 to 30 knots of breeze, light air is the condition where the jib should be set up with the greatest amount of luff sag.  A full entry is more powerful, and also helps widen out the “groove” so the boat is less critical to steer, mast prebend also contributes to luff sag.

DOWNWIND

Off the wind, the mainsail doesn’t require as much flow across it, so a full shape will make it more forgiving. Ease the outhaul, and mast bend should be eliminated.

On a reach, if the spinnaker is drooping, in many cases it is quicker to sail with the jib and douse the kite.

With a symmetrical spinnaker adjust the pole height so that the clews are level and make sure that the sheet is light enough not to weigh the corner down and that the sheet is well eased.  

BOAT HANDLING

Crew movements must be slow and weight forward to lift the large flat aft area of the boat to reduce drag. To make the boat head up heel to leeward slightly, once turned to the heading you want, flatten the boat to its sailing lines. Rudder movement acts as a brake so keep it to a minimum and use weight to turn the boat.

Avoid pinching because the boat relies on forward movement to create flow over the foils, once flow detaches from the foils the boat will start to slide sideways so foot off get the flow going and as you accelerate steer up slightly by moving your weight to leeward. This is an ongoing procedure and, in a lull, move weight to weather to steer down to accelerate and then repeat.

Keep the crew out of the slot and keep the boat flat unless using weight to steer.

If you have good boat speed, standard tactical situations should be approached aggressively in most conditions, but light-air tactics demand more conservatism and greater anticipation.

In many instances, you can actually gain distance when you dip a starboard tacker because of the speed you generate when bearing off. On the other tack, don’t be afraid to wave an approaching port tacker across if it looks like they might tack on your lee bow to avoid you. 

If a new wind comes in with more velocity, always sail to it as soon as possible, even if this requires sailing a headed tack for a short period to get to it. Since maximum boat speed is extremely important, always aim to get in the position to increase speed through the water. 

Obviously, a massive shift would be an exception to this rule if the shift were to last a substantial length of time.

Anticipation in Sailing Races

In every sailing race, to enhance your chance of success you must keep a constant watch ahead and around the course to see what’s coming and have a plan on how to deal with it before you get there.

Before you leave the beach and before every race, you need to develop a plan to deal with the anticipated activity of the wind, waves, current, and other boats. Follow your game plan as closely as possible and avoid spur-of-the-moment decisions that are made without regard for the big picture.

It’s hard to anticipate when you’re staring at the seaweed in the bilge, you have to keep your eyes looking up the course and all around for signs of things to come.

The helmsperson should concentrate on steering, so the crew really needs to be his eyes. Make sure one person on the boat has the responsibility for watching around the course and is watching for two things: changes in the wind or waves and the movement of other boats.

This person’s goal is not only to watch for puffs, lulls, waves but to warn of approaching starboard tackers or boats on converging courses and to anticipate potential confrontations and to let the helmsman know of possible scenarios.


As an example the crew member who is assigned the task of looking up the course at the wind direction in relation to the marks needs to anticipate that when you come around the windward mark, will you want to do a normal bear away set, or a jibe-set and this needs to be communicated well ahead of time so you are set up at the mark to carry out that maneuver. 

So that the helmsman can be informed about situations before they arise, they should call out in a voice loud enough to be heard by everyone aboard that there’s a puff coming, there is a crossing situation where you may need to duck or tack or the tactic needed at the next mark rounding and why.

In sailboat racing, things are always changing. It would be easy if we could plan ahead for every move on the race course but unfortunately, this is impossible because you can’t always predict what the wind will do or how the other boats are going to react.

What you can do is anticipate a  number of possibilities that might happen then make a plan for each one. 

By giving you time to consider decisions ahead of time, contingency plans help you stay in control of your race.



 

 

5 Steps to Winning a Regatta

 Step 1. Work on your weaknesses.

 We all have different strengths and weaknesses, for some, it is light air and flat water,  for others they are faster in a big breeze and boisterous seas. It is fun to practice in your favourite conditions but you need to get out of your comfort zone and spend more practice time sailing in the conditions that you are slower in.

Keep the boat flat

Step 2. Preparation.

Leading up to an event focus on reducing distractions, cross off all the items on your boat work list and let all work clients, colleagues and friends know that you will not be available during the event. When a regatta begins you need to be rested and ready, and your first and only priority is going sailing.

Complete all tasks prior to leaving home

Step3. Go to a regatta with someone you have spent a lot of time sailing with.

If you are sailing in a multi-crewed boat resist the temptation to link up with a hot shot in your class for a big event. In a crew-driven boat, the helmsperson only does about thirty per cent of the work. If you compete with someone that you have spent many hours in the boat with, you know each other’s weaknesses but also know each other’s strengths, and in tough situations, you remind each other to focus on those and let the rest sort itself out.

Step4. Nutrition and Hydration.

Proper nutrition and hydration could make or break your results. Carry adequate food, snacks and water during the race especially if you are competing in two or three races in one day. Don’t neglect off the water fuel and hydration and resist the partying until the event is finished. Supply your own food rather than what the regatta organizers or canteen provide and don’t neglect to get plenty of sleep during the event.

 

Step5. It doesn’t have to be perfect, it just has to be better than the rest.

It’s easy to give up, but instead, focus on the opportunities that an event presents and sail hard, remember everybody else is hurting too and wrestling with the same issues as you are. Fortunately, great boat speed, developed over the time of working together will allow you to move up through the fleet and this is where all your hard work pays off. 

How to Point, Foot, and Change Gears

Gear changing is what separates the mid-fleet sailors from those who always seem to be a tad quicker and higher.

While most of the fleet starts the race with a similar setup created with the help of a tuning guide, the fast boats are constantly making additional adjustments. When conditions suddenly change—a puff hits or you sail into a lull, the fast sailors shift gears.

Fix Pointing Problems:

Trying to pinch to maintain height is most likely the reason for your pointing issues and by pinching, the boat is actually sliding to leeward. The remedy is to “foot then point”, a boat needs to go fast so the foils can develop lift, so ease the sails a little bear off a couple of degrees to get up to speed then point up and re-trim to the optimum setting.

Once the boat starts to slow down, be sure to ease the sails out, regain your speed, then start the process again.

While it may seem natural to let the boat heel more when trying to point, fight the urge, keeping the boat flat will maintain a balanced helm and maximize the efficiency of your underwater foils.

When sail trim is the cause of the problem, it’s usually the main, not the jib. The upper leech of the main provides most of your pointing ability so be sure to trim the main so the upper batten is at least parallel to the boom.

If you need more pointing ability, try trimming the main tighter. You can hook the upper batten as much as 15 degrees to weather for short periods but avoid the temptation to over-trim the jib to help pointing ability.

Fix Footing Problems:

The easiest fix is to ease the sails because more open leeches on both sails will help the boat sail lower and faster in a straight line but this can create a pointing problem. 

To correct this, first, check your helm balance because weather helm will hinder the boat’s ability to go fast. Instead of easing sheets try to sail the boat more level if you can’t keep the boat flat, induce more mast bend to flatten the main.

The next step is to ease the traveller until the helm is balanced. Other remedies are to tighten the outhaul, tension the Cunningham/jib halyard to pull the draft forward and open the leeches of both sails.

Gear Shift in a Puff:

When a small puff hits.

1. Ease the main.

2. Steer up to “feather” the boat.

3. Re-trim the main.

Because a puff typically lifts the boat due to a change in the apparent wind speed, you need to ease sheets and head up as it reaches you. Let the boat climb to windward and steer toward the upper end of your groove using the jib luff telltales.

If the puff is particularly severe, more adjustment may be necessary. If you can’t hold the boat down after making the above adjustments and there’s still too much helm, do the following until the helm is balanced.

1. Ease the traveller

2. Bend the mast (vang tension, backstay tension, etc.)

3. Tension the Cunningham on both main and jib.

Gear Shift in a Lull:

Lulls usually appear as headers and in a lull, it’s important that you bear off as smoothly as possible. Make sure the boat remains flat and resist the temptation to add heel to maintain “feel” in the helm.

Ease the main so the top batten angles outboard from parallel to the boom, leave the jib trimmed initially until the bow is pulled down to the lower end of your groove with both telltales streaming aft.

At that point, the jib should be eased so the leeward telltale doesn’t stall.

To maintain boatspeed in a lull

1. Ease the main.

2. Allow the boat to heel to weather, creating lee helm, to steer the boat down.

3. Ease the jib.

4. Level the boat.

5. Pull the traveller up (if the boom is below centerline).

If a lull lasts for a longer time

1. Straighten the mast and induce luff sag in the jib

2. Ease main and jib cunninghams to maintain correct draft position

 

How You’ll Know When The Wind Is Oscillating.

 

Oscillating shifts are the most common type of wind pattern, so if you’re not sure what the wind is doing assume it is oscillating until you discover otherwise.

It’s very important to figure out whether the wind shifts will be oscillating or persistent, but this is not always easy to
do. There are some visual clues (listed below) that often mean the wind direction will be shifting back and forth.

The wind is blowing offshore.
When the wind is blowing from the shore, it’s almost a sure bet that the land’s irregularities will cause oscillating shifts.

Your headings on each tack go up and down.
Your pre-race compass headings on port and starboard tack fluctuate around an average direction (which stays
roughly the same). Shifts happen fairly quickly, not gradually.

Boats are lifted and headed on both sides of the course.
As you look across the course, you see boats on both tacks on lifts and headers in a somewhat arbitrary pattern. Boats that
are lifted then get headed and vice versa.

You are sailing in a gradient wind after the passage of a cold front.
Oscillating shifts (and puffs) that come with a vertically unstable air mass.

The wind on the water looks patchy and/or puffy.
You look across the course and you can see lighter or darker spots that show puffs or lulls. Sometimes you can even see ripples indicating changes in wind direction. This wind is almost surely oscillating.

On the first beat, each tack is sometimes longer to the windward mark.
As the wind oscillates, so does the longer tack to the windward mark. That is, sometimes your bow points closer to the mark on port tack, and sometimes it points closer on starboard tack.

Boats gain (and lose) on both sides of the course.
As you sail up the beat, boats are as likely to pass (or be passed) on the right side as they are on the left. It all depends on who is in phase with the shifts, not on who goes farther to one side.

The ‘favoured’ end of the starting line switches from one end to the other and back again.
In shifty winds, most starting lines are set square to the median breeze. So when the wind is in a right phase the right (committee boat) end of the line is favoured. When the wind is in a left phase, the left (pin) end is favoured.

 

We need to deal with congested areas when sailing.

You will perhaps already have noticed that, shortly before the Start, when the boats have lined up in the Start area, that the wind is significantly weaker there, even if you are in the front row and have clear wind.

The reason for this effect is the congestion which forms in front of the regatta field producing a not insignificant resistance to the wind.

 

In addition to this effect, the wind blows around this congestion and is significantly stronger at the edges, as shown by the narrower lines.

If we find ourselves on the left-hand side of the congested area, the wind flows to the right soon after the start and we can run higher. But take care, after the congestion zone the wind turns back to its original direction again.

This left wind shift should not be misinterpreted as an oscillation to the left, and mislead us into a tack to the right-hand side of the course.

If we find ourselves on the other side of the congestion, we have the exact opposite effect and feel a header and the leeward boats can sail closer to the wind than we can. If we have the freedom to tack, a quick tack and a short run to the right is called for. Sailing on port tack on the right side of the congestion we don’t have to sail against the wind shift and can also benefit from the stronger wind at the edge of the congestion.

The starting line is often relatively clear in the middle, and a group of boats forms on the right and left of it, each group forming their own independent congestion ‘cloud’.

In this case, the yellow boat can also benefit from the wind shift. In the middle, between these two congestion zones the wind will be at its strongest for a short time; a further advantage of this position.

However, don’t forget: the pre-requisite for being able to use these effects is a start in the first row. Under cover of other boats, you won’t even notice them.

Special thanks – Article by Peter Czajka – The Tactics of Sailboat Racing

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