March 27, 2014

Sailing in the Middle of the Fleet - Sailing Downwind Part 3

By Doug
Why can sailing by the lee sometimes be fast? It's counter-intuitive that pulling your boom in to catch less wind on a run can actually make you go faster. While this post is to help middle-of-the-fleet sailors, others might benefit from the following.

From a design perspective, the Laser's mast was revolutionary. But from an efficiency perspective, a Laser mast is located, like all other masts, exactly where you do not want it to be.

On the left we see a boat with a jib when going upwind. The drag is in red and is hardly visible because the forestay holding the jib creates hardly any turbulence. Jibs are efficient because they have very little drag and they have a whole lot of lift. On the right is a Laser and there is much more turbulence because of the mast. So much so that the front of a main does not work properly which is why telltales cannot be placed too close to the mast: 

There's something else that is important - having the wind flow across the sail is fast. This is why sailing on a reach is faster than sailing on a run. And why asymmetrical spinnakers are faster than traditional spinnakers. And why a house roof that is low is more at risk in a hurricane than a higher roof with steeper angles. The reason is that the wind creates a lot more lift when it goes across an object than when it’s just trapped by an object.

In a perfect world sailing downwind, masts would not create turbulence and the wind would always flow across sails. But this is not how we sail. As shown below, the boat on the left has its sail all the way out and is trapping lots of wind, creating lots of turbulent drag, and generating no lift. The drag is in the correct direction so the boat is literally being dragged downwind. The boat on the right has the boom pulled in and the main looks a lot like a jib going upwind - but there is no mast at the leading edge to create turbulence and the wind is flowing across the sail:

So the sail on the left is catching more wind while the sail on the right is more efficient. Sometimes more is better and sometimes efficient is better. Sailing by the lee is knowing when to shift from one to the other. Here are some tips:
  • I try to steer with my weight, so bearing off is leaning out to heel to windward. As a result, the end of my boom actually torques back and up at the same time. It feels like I’m “scooping” more pressure and, when timed properly, it feels very fast.
  • With the boom in, the pressure on the main sheet goes from hardly any pressure and wanting to jibe to really powered up and driving forward. Timing this power properly can be a great way to catch even small waves. Again, this can be fast.
  • I like to set the vang so that the leach stretches and “breathes” back and forth about 8 inches. This is a completely natural and legal pumping motion, and a gift from the laws of physics.
  • In addition, you can bear off or use your main sheet to pump the main once per wave. This is significant because you’re pumping the leading edge of the sail which is super effective because that’s where all of the lift comes from. This is the only time in sailing when you can pump the part of a sail that has all of the lift.

March 23, 2014

Sailing in the Middle of the Fleet - Sailing Downwind Part 2

By Doug
More comments and questions from Pam. 'The sailing by the lee explanation finally clicked with me - but how far do you trim the sail in or out to make this work?'

It's a great question because sailing normally, when the wind flows from the luff to the leach, you trim and steer by looking at the telltales and the front of the sail. Does this mean that we need telltales at the leach for sailing by the lee?

The answer is no because people sailing by the lee rarely look at the sail. You sail by trying to feel the maximum pressure on the mainsheet. With the ratchet turned off this pressure will sometimes double, but it does not last long. Your goal is to hold this extra pressure for as long as you can - 5 seconds if you're lucky. You then let your sheet out a little before pulling it in again.

This action is very gentle and is not pumping but this extra pressure is not always easy to find. The lighter the breeze, the harder the extra pressure is to find and below 10 knots, it might not be possible for a beginner to find at all. When it does work your sail is actually generating lift instead of just catching the wind by stalling, which is what it's doing when your boom is out.

As a rule, you'll feel the strongest pressure just before the sail wants to jibe. Here's Tom Slingsby from the Perth Worlds video (at 21:02) where his leach is folding and the sail wants to jibe: 

Tom heads up to prevent jibing, but only slightly because his trim is fast.
So remember, sailing by the lee without the extra pressure can be slow. If you cannot find it within a few seconds, it's best to let the boom out to its regular "stalled" position and then try again in 10 seconds. It's a constant search for extra speed, which is another reason why it's so good for middle-of-the-fleet sailors. 

Sailing on a run downwind the with the boom out is like taking a break. Sailing by the lee makes you more aware of what your boat is doing and gives you things to try when other sailors are taking a break.

This post is about how to make it work. Our next post will be why it works and will include gifts from laws of physics: perfectly legal pumping.

March 11, 2014

Sailing in the Middle of the Fleet - Sailing Downwind Part 1

By Doug
Many of these blog posts start with questions from Pam. Her latest ones were "How do you play shifts downwind" and "Why didn't you do more sailing-in-the middle-of-the-fleet for downwind?" So, here goes.

Going upwind, when everything is even neither green nor red has the advantage:

But this seldom lasts for long. When the wind shifts to the right, green is on a lift and red is on a knock (or a header) and should tack:

And then the wind shifts to the left, green is now on a knock and red is on a lift. Green should tack:

So a rule when sailing upwind is:
·         if the wind helps you to head up on a lift, that's good because you're heading closer to the mark.
·      if the wind forces you to bear away on a knock, that's bad because you're heading away from the mark and you should tack.

There's nothing new here because this is something that most middle-of-the-fleet sailors know. But when you're going downwind, the shifts are harder to feel because you're going with the wind and your sail will not stall, so it's not as sensitive to these changes. Knowing how to play the shifts represents a great opportunity for middle-of-the-fleet sailors to make gains. (A word of caution: the following is how I sail a Laser or a similar boat with just one sail - other boats will do things differently).

Going downwind when it's steady, neither green nor red has the advantage:

When the wind shifts to the right, green might trim the sail in a little and red might trim out a little:

And then the wind shifts to the left, green might trim the sail out a little and red might trim in a little:

This is one correct way to play the shifts downwind, but most middle-of-the-fleet sailors will not notice these shifts and will not make the correct adjustments. If you do, then you'll gain a little.

But when there's a bit of wind, there's a much better way to play the shifts going downwind. Let's start by looking at the fastest point of sailing - being on a reach:

Anytime that you can set your boat up for a reach you'll gain speed. Let's look at this a little more closely:

The wind flows from the leach to the luff of the sail and pushes the boat forward. But here's a really interesting fact - the same force would be generated even if the wind was coming from the the opposite direction:

So why is this important? Because if you rotate this diagram 90 degrees, red is on a run, but the force on the sail is the same as though it's on a reach:

This is called sailing 'by the lee' (leach to luff vs luff to leach) and there are so many reasons why this is really fast that we'll have to cover this in another post. But for now, just remember that that sailing on a reach is really fast.

So when the wind goes right, instead of red trimming the sail out as we have seen above, it can be much faster to trim the sail in:

The wind goes right, one red trims out....                the other trims in.
When sailing downwind, I'm always looking for a way to trim the sail in relative to the wind. Red on the right is the fastest, and green is the slowest and should jibe and sail by the lee ASAP.

And the opposite is true - when the wind goes left, instead of green trimming the sail out, it's much faster to trim the sail in:

The wind goes left, one green trims out...                  the other trims in.
So when the wind is above 10 knots, the rule when sailing downwind is:
·       sail the course that helps you keep trying to trim the sail in.

It's simple! I look for this all the time - I try to sail by the lee as much as possible because it's an easy way to look for speed. It does not always work and I probably jibe more than anyone else in the fleet, but there's always something to try to get extra boatspeed.

It's fast! Using this simple trick, a middle-of-the-fleet sailor can actually start to have the speed of a really fast sailor. How fast? Like Tom Slingsby on his way to winning the Laser Worlds in Perth:

World-class speed sailing on a run... with the sail trimmed in.
Check out this video starting at 20:00. When Tom is on a run, he does everything he can to trim the sail in to sail by the lee. Here's how the wind is moving across Tom's sail at this moment:

There are lots of other ways for middle-of-the-fleet sailors to improve when sailing downwind. We'll look at these in detail next.

March 08, 2014

What's Wrong With This Picture?

By Doug
This is a beautiful watercolor in our doctor's office. The artist took great care to make this picture as realistic as possible, even though the artist was not a sailor. How do we know this?

March 05, 2014

Radial or Full Rig - Part 4

by Doug
Al Clark -(left) and Steve Cockerill (right) - competitive in both a Radial and full rig
How do you choose between a Radial and a full rig when you want to compete at the highest level for your age group and you want a shot at winning?

Two sailors from Sydney showed that you can't choose a rig by your weight. Brendan Casey was at least 180 pounds (81 kg) when he twice won the Open Radial Worlds and Peter Heywood was 150 pounds (68 kg) when he came 5th in the Standard Master Worlds. Each sailor was way outside the recommended weight for their rig, and yet both were extremely competitive as the results show.

So, what does this mean? For me, it's simple: you practice against the people who give you the most competition - if the locals sail in full-rigs, then you will look for ways to join them, and if they sail Radials then you'll consider Radials.

But for the big events (for me a Worlds), you need to take more into consideration: your weight, height, the expected conditions, health, conditioning and which rig you've been practicing and competing in.

It was clear at the Oman Worlds that many of the Masters and Open sailors including Robert Scheidt had lost weight in preparation for the expected light conditions. And in windy venues, many of the tops sailors will arrive with extra weight.

I put on 10 pounds in preparation for Chile and was 185 pounds (83 kg). It was one of the first times I ever felt in control of the boat in a breeze. I was only passed once upwind in the entire 11 race series. When you are light and sailing in waves in a breeze, you tend to get knocked around going up and down waves but with the extra weight that doesn't happen as much. Mark Bethwaite's comment was that between the prior Worlds and the Chile Worlds, the difference was that I had learned to sail in a breeze. For me, the extra weight made a huge difference.

I showed up light in Halifax weighing just 168 pounds (76 kg) unable to put on weight after a change of diet. While very competitive in the light stuff, in the heavy breeze, I was suffering. The front row tended to be even and I would finish within 30 seconds of the front row but that usually meant 5th to 7th place. I was fit and had trained hard for Halifax but just couldn't hang with the front row. The only time I had speed and led was in the light stuff but it was mainly a windy series so my finish position was 6th. For me, being that light put me at least 10 seconds per upwind leg off the pace of the front row. Frustrating to lose ground to the front row every upwind leg.

Some sailors like Al Clark and Steve Cockerill are fortunate to have the choice of being able to switch from one rig to another based on the expected conditions since they get the opportunity to practice against good competition in both rigs. For others, the decision is harder.

If I look back at the conditions in Oman and my lack of practice in a Radial, my decision to sail a Radial was wrong. But if I look at my health issues at the time (shoulder, vision), it was the right decision.

So for the major events, it's clear to me that each person has to make his or her own decision, then enjoy the ride, and learn from the experience.
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