Tag Archives: sailing

Race Night Report – June 23, 2017 (and Spring Results)

Spring Series Results at end of post.

Race Night Report

We had a good turnout for our final outing of the KSC Spring Series, with 13 racers!  In fact, all available Albacores were out on the water, along with a Tasar, a Laser, and 2(!) Hobie 16 catamarans, despite the lighter conditions.

A delay getting people on the water (and finding boats…) meant that race 1 was sailed by 3 double-handers and a Laser.  To the surprise of absolutely nobody, Steve and Carla blasted around the course in the Tasar, leaving a couple of Albacores to fight with a Laser for the remaining places.  Jean skippering her very first race (she just got her blue tag!) and Frank were able to win second, followed by Ray and Chunshu.  Tuan (our first rookie this season) was awarded an on-course-finish in a Laser.

The second race saw the racers joined by Tony/Annie in a Hobie 16 catamaran at the start.  A second, very overloaded,  H16 started later in the race (Norm, Tom N, Jason, and rookie Devin).  Carla/Steve took the win (again) followed by Jean/Frank (again).  This time Tuan took 3rd, with Ray/Chunshu following and Annie/Tony scoring the first cat finish of the season.  The 4-men-on-a-cat was awarded an OCF to allow the 3rd race to get underway.

And what a nuisance that 4-man cat made itself that 3rd race :).  Just before the gun, the overloaded cat decided on an aggressive start at the boat end, enforced it’s rights, and pushed the Tasar across the start line early.  Ha ha, take *that* Steve.  The move was just a couple of seconds too early though, the H16 had to bear off and and the Tasar was able to duck behind the cat, do a dip start, and led the whole way though the race.  Still, it was fun while it lasted.

After rounding windward in 3rd place (behind the Tasar and H16), Jean and Frank made use of the Albacores superior direct light-downwind performance on a wind shift on the second leg, and passed the overloaded cat, who had to head up to maintain any speed.  The overloaded boat made up distance on the second reaching leg (more of a beam reach than a broad reach) and were able to establish overlap just outside the zone and round the leeward mark on the inside.  Remember how I said she made herself a nuisance?  Jean and Frank tacked quickly to get out of the cat’s dirty air, and the cat made a big tactical mistake… she tried to tack to stay in front of the Albacore, and just got stuck in irons, and was passed by Frank/Jean as well as Chunshu/Ray (lesson learned — when sailing a cat, don’t get into a tacking duel).  At the windward mark the overloaded cat was passed AGAIN, this time by Tony/Annie’s H16, who came from behind.  End results, Carla/Steve 1st, Frank/Jean 2nd, Chunshu/Ray 3rd, Annie/Tony 4th, Jason/Norm/Tom/Devin OCF 5th.

Apres-sail was a blast, as always, and a huge shout-out to Ray for bringing the beer/burgers!  Thanks again goes out to our RC (Reese and Sydney) without whom the race would not have been possible.

Spring Series Results

We got in 8 official races over 3 nights, in addition to the 2 races run on the practice night when the water was still too high to keep the boats at the beach.  This means that we have 2 dropped races (1 drop per 4 races) to take into account for series results.

Going into the night Jason had placed first in the prior 5 races, but with two drops, it was anyone’s game if Jason dropped the ball and placed poorly (which he did).  Tony (with a few 1st places), Carla, and Norm (2nd and 3rd place finishes) were all in contention.  Basically, if Jason scored poorly, and either of them got a few firsts, then it would all come down to “how poorly did Jason score”.

And, as we know, Jason scored poorly in the 4-man-cat, while Carla won all 3 races on the final night…

So who won the series?  (drum roll please…) The net result, including dropped races is a TIE at between Jason and Carla at 10 points each!  We now have to go to the score excluding drops for the official series winner, and it looks like Jason wins with 22 points vs Carla’s 40.  Congrats Jason, bragging rights are yours for a few weeks.

We had two rookies come out this series, Tuan and Devin.  Between the two, Tuan takes the “Best Rookie Award” and bragging rights, at least for the next five weeks. (Note: a previous revision of this post said that Devin had won, because I didn’t realize Tuan was a rookie — the official scoring chart, below, will also be updated)

Complete Spring Series Results

Summer Series 1 Starts June 29

Come on out next week when we’ll all start with 0 points for Summer Series 1 (June 29-July 27).  I especially invite our Learn-to-Sail students to come on out and exercise those shiny new blue tags.  We have a “best rookie” award, and great food/company afterwards.  Even if you don’t want to race by yourself, let your humble* sailing director (Jason) know (sailing@kanatasailingclub.com) and we’ll make sure we get a skipper or crew for you.  “Nobody left ashore” policy is still in effect; if you want to sail, we’ll get you on the water regardless of circumstances.

*well, he may not be so humble for the next few weeks — if you want to take him down a few pegs, come on out and beat him around the course!

Race Clinic – June 10, 2017

Tom Saunders managed to condense his one-week Silver Sail program into an hour and a half lecture on the secrets to winning races.  There were a few themes he returned to throughout the talk, and these will be bolded throughout this post.  The class then hit the water for some practice working on what Tom described.

Keep it simple, focus on the basics.  Tom laid out an anecdote about how how he and a buddy were able to place well in a national regatta with a beat up boat that had been sitting under a cottage for 30 years, just by making sure the sheet and vang tensions were right.  Don’t worry about the little stuff until you’ve got the basics nailed.

Tuning.  Rig and boat tuning were covered in an earlier session of the Advanced Sailing Skills course.  Make sure your sail controls work and that things are tensioned the way they are supposed to be, and you’ll have an advantage over all the jokers in the fleet who just rig up and go.  You don’t have to be adjusting the cunningham by millimetres 6 times a leg, but making sure your shrouds, centreboard, vang and sheets are working together is a huge step forward.  Also, proper rig tuning lets you point higher on the upwind legs, and we’ll soon see how important that is.

The start.  You won’t win a race on the start line, but you sure as heck lose a race there.  A good start means you have clean air, and can go where you want to go.  A bad start means you have reduced options, and are trying to sail in the slow turbulent air that other boats are leaving behind.

Tactics – be able to justify your actions.  When doing something, think about why you’re doing it.  Instead of starting a race “somewhere on the start line”, think about “should I start in the middle of the line, at the starboard end, at the port end?”  Have a plan.  If you’re on a leg, think about “why would I tack now?” and what advantage it buys you.  Think about “why would I delay tacking?” and what advantage that buys you.  When you think about doing something, being able to justify it to yourself is much better than tacking “because I was told I should be tacking more”.

In similar boats, with sailors of similar skill, you will never be able to beat someone by following them on the same tack.  If the person ahead of you is on starboard tack, you’ll never be able to pass them on starboard.  Any gust will hit them first.  Any wind shift will affect you both the same.  Any attempt to pass them to leeward will put you in their wind shadow.  Tacking onto port  may or may not be the right move we’ll go into (the “whys” later) but you can’t expect to beat them on boat speed alone.  This is especially true near the end of a race (if you weren’t able to pass them over the the last 6 legs, why do you think you can do it in the last few hundred feet?)

The act of tacking onto the same tack as the person behind you is called “covering”.  Here’s an example (because I love this video).  It’s from the 2015 Laser World Championship.  The boat in second place (USA, Chris Bernard) knows that he can’t beat the boat in the lead (Australia, Tom Burton) while they’re on the same tack.  Tom repeatedly tacks his boat to cover Chris, denying Chris the opportunity to pass.  Chris immediately responds by tacking, forcing Tom to tack again.  This is called a “tacking duel”.  You generally won’t get into tacking duels at club races, but you’ll see them at higher level events.  At 6:07 of the video, Chris (behind) fakes a tack.  Tom tacks his boat (thinking that Chris is tacking) and Chris is able to gain ground.  Tom realizes his mistake, and changes tactics from covering-Chris to just making a dash for the finish line.

One final general tip is to watch the race leaders.  People like Steve, Carla, Ken, the other Ken (and too many others to name), will often be at the front of the fleet, with the rest of us wondering what we’re doing wrong.  So, if you see the leaders all heading the to left side of the course, start thinking about why that is.  You don’t have to follow them, but it helps to figure out what they know (and that’ll help you make better decisions).

Starting Notes

We’ll talk about some properties of the start line before talking about how to execute a good start.

The sag (aka scoop, or dip) of a start line

On the water, it is HARD to judge where the start line actually is.  This leads to boats near either mark being close to the start line at the gun, but those closer to the middle of the start line tend to be a little farther back.  How hard is it to judge where the start line is?  Well, I’m going to go out on a limb, and say Olympic sailors are better than most of us.  And here is what the start line at the 2012 Olympics looked like 3 seconds before a race:

You see the boats how in the middle of the start line are farther back?  This is known as “sag” to the start line.  So, assuming you  want to start in the middle of the line, how can you get the best position?

One way is to assume that the sag is there, and just be out in front of everyone.  This takes a lot of guts.  If you overestimate the sag, you’re over the line early, and have to restart (or are disqualified).

Is the start line square – which end is favoured?

By “square” I mean square to the wind.  Let’s say the start line (and course) was set, and then the wind shifted 30 degrees.  If the wind is coming from the starboard side of the course (for example), the “distance upwind” from the starboard end of the start line (the “boat end”) is less than the distance from the port (“pin end”) of the start line.

Generally speaking, if you put your boat perfectly in irons, it will point towards the favoured end of the line.

The other reason one end of the line might be favoured over the other is that maybe the wind is different on one side of the course.  In the image below, a racer sees a heavy air gust on the starboard side of the course.  They might select the starboard side of the start line so they can tack immediately after starting, and sail to the gust.  Once there, they may choose to tack back onto starboard (the edges of gusts tend to be faster than the middle of gusts, so in the diagram, the sailor is trying to ride the edge of fast air)

One thing that Tom stressed throughout his presentation was having a reason for everything you do.  Here are some reasons you might select one end of the start line over the other:

  • You want to tack onto port immediately to get to the right hand side of the course — start at the starboard end of the line
  • One end is favoured — start there
  • You can’t decide which end of the start line is favoured — start at the middle of the line
  • There is a large clump of good sailors at the favoured end, and you don’t want to get caught in the scrum — start in the middle
  • You have trouble judging sag — start at one end of the line

All this is to say is that there are lots of things to take into account when picking a spot on the line.  It’s up to you to weight the different options and to pick a spot deliberately, and execute your plan.  Don’t just start “somewhere” on the line, start from where you think you can have your best race.

Starting Techniques

Before I start writing about some of the potential techniques you can use to start, I’m going to write a bit about the end goals.  The best case scenario for a start is to cross the start line, with the boat at full speed, into clean air, and with right-of-way over nearby boats, just as the race starts.  Now, that’s a lot to remember, and harder to get right.

Crossing the line at the right time

This is conceptually the easiest thing to get — you don’t want to cross the start line before the race starts (the best case scenario is that you have to turn around and cross again).  But you don’t want to start the race late either.

So whatever technique you use to start, you want to be very close to the start line as the race starts.

Crossing the line with speed

Even if you’re first across the start line, if you’re moving slowly at the start, then someone slightly behind you (but moving fast) can pass you.  So the second thing we have to think about is how to ensure the boat has some speed before we cross.

We know that reaching is a faster point of sail than close hauled.  We also know that close hauled moves us upwind.  This suggests that a good start technique might be to sail close to the start line some time before the start, and sail on a close reach or broad reach in the seconds before the start.  The amount of time it takes your boat to reach top speed will determine how long you have to reach for.  Once your boat is at full speed, you can turn it up to a close-haulled course just as the race starts, and cross the line with lots of speed.  The issue with reaching in the few seconds before a start is that you have to have the space to pull it off, which is why you have to be very careful about other boats and who has right-of-way over whom.

Right of way

Here is where things get complicated.

So far we’ve determined that we want to be near the start line, reaching just before the start, and we’re going to turn upwind to close-hauled just as the race begins.  But there are going to be a bunch of other boats trying the same thing.  How do we ensure there’s no one in our way (and, to a lesser extent, can we give ourself and advantage by getting in the way of other people)?

Let’s look at the Racing Rules of Sailing, specifically rules 10, 11, and 12, and how they apply to 3 different set of boats:

10: When boats are on opposite tacks, a port-tack boat shall keep clear of a starboard-tack boat.

11: When boats are on the same tack and overlapped, a windward boat shall keep clear of a leeward boat.

12: When boats are on the same tack and not overlapped, a boat clear astern shall keep clear of a boat clear ahead.

Given rule 10, it’s obvious that (everything else being equal) we would prefer to be on starboard tack at the start.  This means that we have right-of-way over everyone on port tack.  In the diagram below, scenario 1, the green boat is on starboard tack, so she has right of way over the red boat on port.  The port tack boat must do whatever to avoid the starboard boat.  If you’re the starboard tack boat, it’s customary to yell “Starboard!” to let red know that you are there, and have right of way (but it’s not a rule, they should be watching where they’re going)

Rule 11 means that if two boats are overlapped (that is, part of the “behind” boat is in front of the transom of the “ahead” boat) then the boat that is to leeward has right-of-way over the boat to windward*.  In scenario 2 below, both boats are on starboard tack, so rule 10 does not come into play.  The boats are overlapped.  Because the boats are on starboard tack, the green boat (on the port side of the red boat) is considered the leeward boat.  Thus, red, must avoid green (even if it means crossing the line early, or tacking onto port).  If you’re the green boat, it’s customary to yell “Up! Up! Up!” to tell red that she must head up to avoid you.

Rule 12 is pretty intuitive — you’re not allowed to bash into the back of someone else’s boat (scenario 3).  Note that because the red boat has not crossed the imaginary transom line the boats are not overlapped.  Red must stay out of green’s way.  Red could maybe make a choice here.  If she were to bear off, she could maybe establish overlap with green.  Then rule 11 comes into effect, and green would have to avoid red.  If red were to do this, she’d risk getting caught in green’s wind shadow.  Alternatively, red could try to sail up above green.  Green would maintain right-of-way but red could try to get into some undisturbed air and maybe beat green on speed.

Start strategies

The reaching start

This one is very easy to do if there are a small number of boats racing.  We’ll assume that you’re the only boat, for now.  The idea is to go on a beam reach, from one end of the start line to the other.  This ensures good position (you’re right behind the start line) and good speed (you’re on a beam reach) when the start sound goes off.  You also have a good window of time to pull off the start.

Let’s say that you time your run along the start line at 45 seconds.  If you start your run (pass one of the end-points) at about 22 seconds before the start, you’ll start exactly on time, right in the middle of the start line.  If you make an error in your approach (or the wind speed changes, or something) you have a very large margin of error — even if you’re 20 seconds early (or late) you still are able to pull off your perfect start.

The reaching start version 2

Let’s say there are multiple boats racing, all who are trying to pull off the reaching start (note — this happens frequently at KSC).  Let’s assume that all the boats are about the same speed when they’re reaching (i.e. you won’t be bumping into anyone going the same direction as you).  In this case, all you have to worry about are boats coming the other way.  No problem!  Instead of crossing “any one of the start line endpoints” 20 seconds before the race, make sure you cross the right-hand endpoint 20 seconds before the race.  This means you have right-of-way over anyone coming from the other direction (you’ll be on starboard tack, they’ll be on port).

In the diagram, there are a bunch of boats reaching along on starboard tack (green), and a bunch on port (red).  The port-tack boats have to turn to avoid the starboard ones, and the starboard boats have a nice lead when the race starts.

The “Timed start” – defending against a reaching start

Let’s say that there are lots of boats doing their reaching start, and they’ve all gotten good enough so they’re on starboard tack.  Let’s say the start line is starting to get crowded, and it’s tough to find a place in the line of boats all reaching along.

The Timed start is trickier to pull off, but if you do manage to pull it off then you get to start nicely while also throwing a wrench into the plans of those who are trying a reaching start.  It takes advantage of rule 11 to be the leeward boat over anyone reaching along the start line.

To execute the timed start, you must know how fast your boat can go from some point below the start line, to the start line.  You start below the line at the predetermined time (say, 45 or 30 seconds before the start of the race) and head to the start line on a close hauled starboard tack course.  As you approach the start line, you can start enforcing your rights under rule 11 (“Up! Up! Up!”).

The boats attempting to do a reaching start are forced to avoid you, since you’re the leeward boat.  They have a few options — try to head up (which might force them across the start line early), bear off and go around your stern (costing them time and distance right before the start), slow down to the point where they won’t hit you (costing them speed at the start), tack onto port (costing them time, distance, and potentially putting them over the line, etc)

The diagram shows what might be happening 20, 15, 10 and 5 seconds before the start.  Green is enforcing her rights and forcing red to make a tough decision.

The tricky part about a timed start is getting the timing right.  If you’re slightly early, then you can bear off just before the start line and burn a few seconds (assuming you have room).  If you’re slightly late though, then you end up starting well behind everyone else in the fleet.

The “Vanderbilt start” — A refined Timed Start

A variation of the Timed start is known as the Vanderbilt start.  You pick where you want to start on the start line, and put your boat there, on port tack, about 1 minute before the start.  At the 1 minute sound, you bear away downwind on a port broad reach for about 20 seconds, gybe onto starboard and head up to close hauled (takes about 10 seconds).  The starboard tack approach to the start line takes about 30 seconds, meaning you pulled off the perfect timed start, and started exactly where you wanted on the line!  Because all boats and crews are a bit different, the timing should be considered a guideline only, and you should work with your skipper/crew/boat to fine tune the numbers (maybe you start your gybe at 22 seconds, or 18 seconds after the 1m warning, for instance).

One final note about the Vanderbilt (or timed) start — I’d recommend using it when there are steady winds.  If there is a lull (or gust, or wind shift) in those 20-30 seconds before you hit the start line, then your timing will be way off (either early or late).

The held position start

This one is the toughest to pull off.  It’s a great technique in a Laser, or other boat which can be accelerated quickly, but you won’t see many keelboats trying it.  Furthermore, it’s best done in a big fleet when there are too many boats to pull off another start.

The idea is that you stop your boat on (or just behind) the start line, on starboard tack, but slightly in irons.  Anyone trying a reach has to avoid you (they will either be on port, or will on your windward side).  If you can hold position until a few seconds before the start, you can bear off and accelerate the boat just as the start sound goes.  If someone tries to come in on your leeward side, you can defend by bearing off and getting in front of them before they get their nose ahead of your transom.  This is called “defending”.  Note that defending will move you slightly leeward along the start line, so make sure you have some space (and defend that space)

The held position start is a game of cat and mouse where you’ll be tested on your ability to hold a position without drifting, be able to anticipate what others are doing, and be confident enough in your ability to enforce your rights.  In big regattas where 50 boats are on the start line, everyone is trying to get an edge on everyone else, there is a lot of shouting from boat to boat (“Up! Up! Up!”, “You’re not overlapped!”)  Often, the veteran sailors will “pick on” a new sailor after identifying them as a “marshmallow” (or “soft target”) who isn’t going to defend their start position.  Not nice, perhaps, but…

Anyway, now that you know what the folks on the start line are trying to do (between defend, and ensure they have a bit of space to leeward), you can make sense of what the boats are doing in videos like this:

 

Dip start (not when black/U flag)

Before we talk about the dip start, I should mention the black-flag/U-flag rules.  In a big competitive race, sometimes it’s tough for the RC to identify all the boats who are across the line early.  If they can’t identify everyone, they’ll abandon the race, and restart.  This gets old REAL quick when you have to start a race six times.  So they made the black-flag.  If the black flag is flying from the RC boat before a race, it means if you’re over the line early (technically, if you’re in the triangle formed by the start line and windward mark less than 1 minute before the race) then you’re disqualified — you’re not allowed to turn back and cross the start line again.  That’s a huge incentive to not start early.  The U-Flag is similar (slightly different rules apply if a race is restarted, but basically “if you’re over early, then you’re out”).

So, the dip start.  Instead of reaching back and forth just behind the start line (where everyone else is, or is lining up), you can be reaching back and forth in front of the start line.  Pick a spot that is free of competing boats, and “dip” behind the start line just before the gun goes.  Obviously, you’re not allowed to do a dip start when black/U flag is up, but you can try if only normal flags are showing.  This lets you sail in clean air and lets you pick a spot in the start line where there are holes.  I’ve never had the guts to try to pull this off, so I can’t speak to how hard it is, or how well it works.

 

Windward legs

Generally speaking, upwind legs are about minimizing the distance sailed.  There is an exception to that rule, but I’ll leave that to the end of this section.

Minimizing the distance sailed is important because most boats on a close hauled course will be traveling at close to their hull speed.  I’m not going to talk physics, but generally an Albacore will go the “about” same speed upwind in 10 knots, in 15 knots, or in 20 knots of air, and about the same speed whether the sails are trimmed “perfectly” or “just okay”.  The perfect sails and higher wind will go slightly faster, but we’re not talking a huge difference.  The difference between a good sailor and a great sailor is the great sailor will be able to sail the minimum distance at the same speed.  This mean tactically choosing a shorter route, and making sure that your boat is pointing as well as as it can.

Pointing

Properly trimmed sails allow you to point close to the wind.  If you try to point too high, you’ll start to “pinch” and the boat will slow down drastically.  If a boat with proper set sails is racing against a boat with poorly trimmed sails, they might be able to point 5 degrees higher than the poorly set boat before loosing power.  To make up some angles, let’s say that one boat can point 30 degrees to the wind, but another can point 35 degrees.  The boat that sails at 35 degrees will end up sailing about 40m farther than the boat sailing 30 degrees from the wind over a 1/2 km windward leg.  So the first thing to do to minimize distance sail is make sure your boat is set up to point well.  Get the foot and leech of the jib tensioned right, apply the right amount of vang, and start making your way upwind.

Headers and Lifts

You can’t sail right into the wind.  When the course is square to the start line, this means you can’t sail straight to the mark, you have to be tacking back and forth to make your way there.  But the wind is oscillating slightly left and right from the average direction, right?  This means that sometimes a close hauled course on one tack is “more” at the mark than a close hauled course on the other tack.

When the wind is coming from one side (let’s say the starboard side of the course) then you can put your boat on a starboard tack and travel in a straight line (or closer to a straight line) toward the mark.  This is called a “lift”.  When the wind shifts to the other side of the course, and is more coming toward you, it’s called a header.  A header on one tack is a lift on the other, so it make sense to tack when you’re being headed.  Remember what we said about 5 degrees of difference saving you several boat lengths?  Well an oscillating wind might be shifting through 45 degrees (or more) or arc, so image how much distance you’d save if you could exploit that!

So, to minimize distance sailed, tack on headers, ride the lifts.

How do you know when you’re being headed, or being lifted?  This is a tricky one.  Top level sailors have a hard time figuring it out.  A compass on the boat sometimes helps.  If you know the course is set so the prevailing wind is blowing from (let’s say) 60 degrees, you might expect your boat to be pointing either 30 degrees or 90 degrees (depending on which tack you’re on).  If you’re on a close hauled course between 30 and 90 degrees, then you’re being lifted.  If you’re close hauled course is less than 30 degrees, or greater than 90, then you’re encountering a header, and should probably tack.  This is an example, how close you can actually point is dependent on the boat, on your sail trim, etc.

Another way to tell is to watch the rest of the fleet.  If it looks like those on port tack are sailing better, then tack onto port.  If Steve (probably the best racer at KSC) hits a gust and immediately tacks to starboard, then be ready to tack to starboard when that gust hits you, because it’s probably a local wind shift.

Sailing when no tack is favoured

If the wind is coming directly down the course, and neither port or starboard tack is favoured, then you can choose which tack you’re on for tactical purposes.  I won’t get into covering too much, but remember what I said earlier about having a plan?  Look at the situation and decide if it’s more advantageous to be on port or starboard.

In general, one wants to sail near the middle of the course.  Some people will sail way off to one side, but these people are taking a risk — they have to come back at some point, and if the wind shifts so they are headed on their way back to the course, then they’re screwed.  It’s okay to sail off to one side, but be sure you understand your reasons for doing so  Unless there’s a good reason to go to the edges, it makes most sense to stay close to the middle.  That gives you the most options if the wind shifts to favour either port or starboard.

The starboard layline parade

Some people will hit that starboard layline very early.  Others will make their way up the middle of the course, and tack onto the layline later.  This often leads to a “parade” of boats, one after the other, approaching the mark on starboard tack.  So when do you join the parade?  Generally, as late as possible.  There are two reasons for this:

  • If the other boat is on starboard and ahead of you, you’ll never beat him on starboard
  • It’s HARD to call the layline from far away.  Even if you do call it perfectly, the slightest wind shift will screw up the layline.

Having said that, if there are lots of boats in the fleet, it might be hard to find a spot in the parade if you leave it too late — remember, you’re approaching the layline on a port tack, so all the boats on starboard have right-of-way over you.  You have to aim for a “hole” in the parade and tack into it.

Check out this video — there’s a “wall” of boats on starboard tack, and the approaching boat (on port) has no rights over these.  She’s got to find a hole in the line, and attempt to not be caught in the wind shadow of the fleet

 

Upwind strategy

1st windward leg — you’re trying to establish yourself at the front of the fleet.  Tack on headers, don’t be afraid to take risks, and hit the starboard layline as late as possible to reduce the chances of over-or-undershooting the mark.

2nd windward leg — be a bit more cautious.  Weigh chasing that boat in front of you vs defending your position against the boat behind you.  Still tack on headers, but be careful about giving the boat behind you opportunities to make gains.

Last windward leg — unless there’s a really good chance of you catching him, don’t go for the boat in front.  Defend your position against the boat behind.

A note about upwind sailing in exotic boats

Earlier I had mentioned that windward was all about minimizing distance.  That’s true in the vast majority of cases, and all KSC boats.  There are a few exceptions though.  Some exotic windward planing hulls or foilers (29er, 49er, International 14, RS700, MPS, 18′ Skiff, Moth, etc) can sail upwind faster than their hull speed, given enough wind, and they may choose to sail a longer route if it results in significantly higher speeds.  KSC doesn’t own any of these boats, so don’t worry about it.  I only include this note because I can’t say “it’s always about minimizing distance” when there are exceptions to the rule.

Downwind legs

If upwinds are all about minimizing distance, downwinds and reaches are all about maximizing speed.  This generally means getting the boat up on a plane, and keeping it there.  A boat in 20 knots of air will go much faster than a boat in 10 or 15 knots of wind, so you’re better watching for gusts on the race course, and making your way towards those, if you can hit them.  If you’re faced with the choice of sailing slightly longer distance at a higher speed, take the higher speed.

Reaching legs

Most sailors, after rounding the windward mark, tend to sail too high initially, and then have to do a deeper run as they approach the gybe mark.  This is slow not only because it’s a long distance, but they might not be making best use of the gusts/lulls to maximize speed.

Let’s look at red’s path.  They round the windward mark, and feel the boat accelerate on a plane.  They think “wow, this is great” and ride the beam reach plane for as long as they can, until it becomes obvious that they have to bear off toward the gybe mark.  As they do so, the boat falls off it’s plane, and slows significantly.  By this time, the boat has no choice but to continue to head down toward the mark.

Blue’s path is different.  It establishes a plane, but bears off early as much as it can while staying on the plane.  When a gust hits, the boat can be headed more directly downwind while maintaining the planing speeds.  This lets the good sailor maximize downwind distance traveled during the gusts.  When the gust ends and a lull is encountered, the boat can be headed up onto a beam reach.  This fastest, most powerful point of sail while hold the plane and maximize speed as they eat up the horizontal portion of the course.  When the next gust hits, they can steer for balance, and push the boat deeper again, still at huge speeds.  They zig-zag along, probably doing about the same distance as red (although in an “average” more direct line) but at planing speeds throughout the leg, instead of only for half of the leg.

The above path of blue just takes into account wind speed changes.  There will be wind direction changes as well that a good sailor will attempt to exploit.  The key is to maintain your plane and maximize speed.

Direct downwind runs

Most boats sail faster downwind by going on a broad reach, gybing, and going on a broad reach on the opposite tack.  Tasars, catamarans, 29ers, Bytes, etc typically do this.  A notable exception to the rule is that Albacores tend to sail slightly faster directly on a run.  I don’t know why, but that’s what the Albacore experts tell me.  Lasers used to be considered faster reach-to-reach but modern Laser technique (which I’m not going to get into) is more about waves than wind, so be aware that those top Laser folks are going to be doing some crazy stuff on the direct downwind legs.

Boat-on-boat tactics

Boats sailing close to each other interfere with each others’ wind.  There are two positions you generally don’t want to be caught in — stuck in the wind shadow of another boat, and being lee-bowed by another boat.

A wind shadow is pretty easy to conceptualize — the air hits the sail of the boat in front of you, and is therefore slower, more turbulent and possibly in the wrong direction for boats behind.  This is sometimes talk about as “eating the other boat’s dirty air” or “the other boat is throwing junk” or some other terms like that.  In general, the lighter the wind, the bigger the wind shadow is.  That’s because the turbulent air has less clean air flowing around it to smooth the wrinkles.  I’ve heard that a typical wind shadow is cast about 4-times-the length-of-the-boom behind the boat, but that may be just an anecdote and I have not seen any proof of that measurement.  Take that advice with a grain of salt.

The 2nd situation, being “lee bowed” is tougher to explain.  As a sail encounters wind, the direction of air flow is directed to follow the curve of the sails.  But air is also “sticky” and it’s not just the air that hits the sails that is deflected — the nearby air is also turned.  If you’re slightly behind a boat, you’ll find that the wind you do feel is more “head on” than you expect.  That’s the result of the boat in front bending the air flow.  And what do we know about headers?  They suck!  You’ll lose power since you now appear to be pinching (as far as your sails know).

Now that you know where not to be, you can judge what the boats around you are doing and attempt to avoid those situations (or, even better, but them into those situations)

Resources

Tom, who gave the talk, wrote a book about all this stuff for the old “Silver Sail” standard, although it was never published.  He put the book on the KSC web site.  Note that the parts of the book that deals with how to use rules to your advantage is out of date (the rules were greatly overhauled since it was written) but the “how to tune your boat” and “how to make it around the course fast” parts are great.  http://kanatasailingclub.com/wp-content/uploads/2014/06/Basic-Racing-Skills-Silver-Sail-manual.pdf

The Racing Rules of Sailing published by World Sailing contains all the technical rules about participating in a race.  You don’t have to know this document, but it’s a good reference.  It’s updated every 4 years (after the Olympics).  http://sailing.org/documents/racingrules/index.php.  Inside the KSC club house there is also the book “Understanding the Racing Rules of Sailing” (which covers the 2013-2016 set of rules, which is pretty close to the 2017-2020 rules).  This book is quite good at not only listing the rules, but going into situations when they might apply and understanding what each boat’s obligation under the rules are.

In physical book form, Frank Bethwaite (Olympic coach, and also the guy who designed the Tasar, the fasted monohull in the KSC fleet) wrote High Performance Sailing, now in it’s second edition.  https://www.amazon.ca/High-Performance-Sailing-Frank-Bethwaite/dp/1408124912.  You can also talk to Jason and he’ll lend you his copy.  The sequel “Higher Performance Sailing” is good too (again, talk to Jason).

Online, YouTube is your friend.  For Laser sailors, I also recommend Doug Peckover’s blog Improper Course which contains lots (and I mean LOTS) of tricks and tips for sailing the Laser.  Also check out Dick Tillerman’s Rules of Laser Sailing.

 

 

 

Race Night Report, June 15, 2017

Sit back and hear the tale of the amazing submersible Albacore.

Race night got off to a great start!  We had a good number of people show up, although most elected to take double handers which reduced the number of boats on the start line.  The wind showed up as well, with steady winds of about 12 knots and gusts in the 16-18 knot range, from the East.  A fairly short course set by Sydney and Reese let us get three races in.

Race 1 was all about figuring out the course.  A shift in the persistent wind meant that most people figured out that port tack would be favoured for most of the leg.  Tony and Jason (Tasar) decided to roll the dice and try a port tack start near the pin end.  With only about 5 seconds before the start, Norm and Carla (Albacore) were coming up to Tony/Jason on starboard, and it looked like Tony/Jason would have to cross early or tack (screwing their start), but Norm/Carla elected to tack onto port right as the gun went (giving Jason/Tony a repreve).  Chunshu and Tom (Albacore) decided to not repeat Tom’s OCS start last week, and gave the start line plenty of room.  The positions held through the race, with Jason/Tony winning, followed by Carla/Norm.  Tom/Chunshu ended up taking on some water and decided to abandon the race to bail their boat.

Race 2 found us joined by Ray (Laser).  By this time most of the sailors had figured out that the port tack start was the winner, but it seemed that Tony/Jason had the favoured pin end all to themselves.  They were able to make the windward mark first, but a battle between Ray and Carla/Norm meant it was neck-and-neck through for second.  Bad judgement on Jason’s part during a shift meant that both 2nd and 3rd place boats gained on Tony/Jason during the downwind leg, with Carla/Norm just a few feet away from establishing overlap around the mark.  Tony/Jason held on for 1st, while Carla/Norm took 2nd and Ray 3rd.

The final race, the game was on!  Norm/Carla won the start with Ray and Chunshu/Tom close behind.  Tony/Jason mistimed their start and had some catching up to do.  But what’s this?  Why is Carla/Norm on starboard tack?  A mistook mark and, the Carla/Norm Albacore was off the course, and had a lot of catching up to do.  Meanwhile, Tom/Chunshu had some trouble at the upwind mark!  Oh no, it looks like their tipping!  Capsize!  Jason/Tony went on to win the race, followed by Ray and Carla/Norm.

The amazing Albacore U-Boat

The real fun was at the upwind mark where Chunshu/Tom were still having trouble.  When the boat was righted, it was sitting rediculously low in the water and would capsize again immediately.  Three capsizes later, we find that their tiller has broken completely off from their rudder head.  They were towed to safety by our intrepid RC (thanks, Reese & Sydney!) with a special shout out to Tony who jumped in the power boat to lend a hand if needed as well.  When the boat got back to the shore, we found that not only was the rudder head busted, not only was the boat full of water, but 3 of the 4 bouyancy tanks were filled as well.  No wonder it was so hard to right!

Race 1 Results: 1st Tony/Jason (Tasar), 2nd Norm/Carla (Albacore), DNF Chunshu/Tom (Albacore), DNS Ray (Laser)

Race 2 Results: 1st Tony/Jason (Tasar), 2nd Norm/Carla (Albacore), 3rd Ray (Laser), DNS Chunshu/Tom (Albacore)

Race 3 Results: 1st Tony/Jason (Tasar), 2nd Ray (Laser), 3rd Norm/Carla (Albacore), DNF Chunshu/Tom (Albacore)

A thank you also goes to Jean and Frank who tended the BBQ and great beer/burgers were had by all.

 

Race Night Report, June 8, 2017

Boats are at the water, and race season is off to a start!

We had two races in light but very shifty conditions (the wind flipped 180 degrees, and we raced a Windward/Leeward course since the gybe mark was on the wrong side of the course).

Tom N and Norm took out an Albacore, and an OCS start cost them in the first race.  Ray in a Laser and Jason in an Albacore battled it out to the windward mark when Ray’s mainsheet let go of the boom block and became unthreaded.  Jason took a couple of penalties on the second upwind, but managed to hold on for first.

1 – Jason
2 – Norm, Tom N
DNF – Ray

With Ray’s boat jury-rigged, Race 2 was held.  The wind however unfortunately died further and Jason was just able to finish before we were in drifting conditions.  Rather than go into shore like any sane person (Ray), Norm and Tom elected to spend an extra half hour on the water to complete the final leg and claim 2nd (rather than DNF)

1 – Jason
2 – Norm, Tom N
DNF – Ray

Post race beer/burgers were enjoyed by all (many thanks to Frank and Jean for cooking!) as we discussed the best way around the modified course using paper plates and beer bottles


Photo credit to Frank Boyaner

Advanced Sailing Skills – June 3, 2017

On the water lesson (log entry below).  A couple theory items first…

Surfing

The instructors took advantage of the medium-high winds to talk about surfing.  The idea was to learn to catch a wave while running and have the wave increase your speed.  The instructors recommend watching your transom, and (when a wave is about to hit) giving the sail a “pump” to try to catch the wave, and ride it.

Death Rolls

The Laser boom can be let out all the way to 90 degrees (and even past!).  This is a blessing, and a curse.  A blessing, in that it give you lots of options.  A curse in that one of those options is to put the boat into “death roll” mode.

Imagine you’re going along downwind.  You have your boom out 90 degrees to the centreline of the boat (on port tack) and your sail controls are loose (to generate as much power as you can).  The bottom of the sail (blue, in the diagram below) is happily generating tons of forward power.  The top of the sail however twists off in front of the mast (red).  It’s generating power too.

Where we normally expect the boat to be heeling to leeward (starboard, in this example) so we’re probably sitting on the windward side of the boat (port).  But the top of the sail is actually pushing the boat to windward (port) which will cause the boat to heel to port.  Our natural reaction, when the boat starts to heel will be to move closer to the centreline, to do it “too much” and the boat will get into an osculating back-and-forth rolling pattern (will can capsize you pretty quick).

So, how do you recover if you feel your boat starting to roll?  You have a few options, all of which are valid and easy (as long as you recognize what is happening and respond quickly):

  • Sheet in — get the top of the sail pointing forward, and the bottom pointing a little bit to leeward.  This stabilizes you real quick and allows you to balance the boat
  • Head up into the wind slightly — this will cause the top of the sail to luff and stop generating as much power, meaning you can organize the bottom of the sail before heading back downwind.

One you have avoided the death roll, there are a few things you can do to discourage it from happening again:

  • Sail with the sheet in slightly (maybe the boom is out 80 degrees instead of 90)
  • Put a bit of boom vang on — this costs a bit of power, but prevents the top of the sail from twisting so much, and you can recover some forward power from that area

You can see in this youtube video a sailor who is blasting along downwind with his sail at 70-80 degrees for most of the video.  At about 28s into the video he lets it out to 90, and you can see how quick the death roll happens if you’re not ready to sheet in (or head up)

Log Entry

Weather Forecast: cloudy, steady 10 knots from W
Observed: partly cloudy, wind 8 knots from NW, with occasional gust in 12-15 knot range (from either N or W)
On the water: waves died out meaning it was tough to find a trough to surf the boat in.  Windward beats were good, although my roll tacks were particularly sloppy today.  To work on next time — stay on old side of boat longer through tack, and do a smoother sit down on new side.  Give larger pump when wave approaches to initiate surf.

 

Advanced Sailing Skills – May 29, 2017 – Rig Tuning

Tom was again our guest speaker, talking about the slot effect and rig tuning.  A couple of videos were shown which demonstrated what he was speaking about.

The Slot & Jib

The space between the jib and the main is called the slot.  In a perfect world, the air travelling on windward side of the jib (the “inside” of the sail) is then directed across the back (leeward) side of the main at higher pressure.  The main and jib thus work together to create a jet of air through the slot and generate great sail force.

The tough part is setting up the jib (and main) to maximize the slot effect.  You do want the slot to narrow (scoop up a bunch of air before blasting it out) but if it becomes too narrow then the slot gets “choked off” and can’t generate the power.

There are three edges to the jib: the luff, the leech, and the foot.

The Luff – We can tension the luff by pulling hard on the jib halyard.  A tight, straight, luff will allow us to point nicely.  In heavy air, the wind will try to bow the luff out sideways, making it curved, and you might need more tension.  Some people (better sailors than I) loosen the halyard slightly on downwind legs to try to get some curve in the luff and gain power.  If you try this, remember to tighten it up again before turning upwind.  The Albacores have (or had) “magic boxes” which are sets of lines and pullys that you can use to set luff tension via the halyard.  Some newer racing Albacores have a normal halyard, but also have a “jib cunningham” which allows you to tighten the luff by pulling down at the tack (and this is usually adjustable from the side of the boat, rather than at the mast).

The foot and leech – Tension on the foot and the leech of the sail are provided by the jib sheet.  The position of the jib fairlead controls the angle the jib sheet is pulling, and therefore controls the ratio of how much tension is applied to each edge.  If the fairlead is far forward, the sheet pulls “down” and most of the tension will be on the leech.  If the fairlead is back, the sheet pulls more horizontally, and the tension is on the foot.  A recommendation from Michael McNamara (British sailmaker, who hosted a Youtube video on rig tuning) suggested that if the line from the jib sheet went to just below the middle of the jib, then things were about right.

Note that as the jib is sheeted in and out , the “perfect angle” noted in blue may change.  Recall what we are trying to do — compress the air flowing through the slot, but leave the slot open enough that it doesn’t get choked off.  This implies that the perfect jib tension, and sheet angle, will change depending on wind conditions and point of sail.  Experiment, figure out what works, and what does not.  When something doesn’t work, use your knowledge of what you are trying to accomplish to figure out why it doesn’t work.

Rule of thumb – you often hear people say “move the fairlead forward upwind, and back downwind”.  While that might be a starting point, use your knowledge to tune your setup.  For instance, in light wind, it is easier to cause turbulence because the luff is too tight and the air doesn’t have the momentum to maintain laminar flow.  So you’d want the fairlead slightly farther back than the “full forward” position.  Similarly, in heavy wind, there’s more air flowing, so you need a bigger slot (again, move the fairlead slightly back).  In medium air, all the way forward may (or may not) be justified.  Figure out what works for your boat, for your sail, for that day, etc.

The Main

Tuning the mainsail is vastly different on a boat with shrouds/spreaders (Albacore, Tasar) compared to a boat with an unstayed mainsail (Laser, Invitation, Byte).  I’ll highlight differences in red.

Both types of boats tend to have bendy masts (and stiff booms).  By controlling the tension on the different edges of the mainsail (and on the jib halyard) we can control how much the mast bends, and that lets us control the shape of our mainsail.  On boats with shrouds, we can also control where the mast bends, somewhat, meaning finer grain control on the shape of the main.

There’s a lot of information here to unpack, and no easy “order” to present it all, since each part kinda relies on knowledge of what other parts are doing.

Inducing mast bend via mainsheet and vang

Pulling on the mainsheet pulls the boom “in” towards the centreline of the boat, but also pulls the boom down.  This tensions the luff of the main.  The vang (or “kicker” as UK/Aussies/Kiwis might call it) pulls down on the boom without pulling the boom in, but also pulls the boom forward into the mast.

On an unstayed boat (Laser and friends), cranking on the mainsheet or vang tightens the leech, and bends the mast along its length, flatting the main and reducing twist.  The top of the mast tends to be a bit narrowing (and bendier) to encourage the mast to bend more at the top than the bottom.

On a stayed boat (Albacore and friends), tightening the vang causes the boom to push into the mast, bending it in the lower section and tightening the leech in the lower part of the sail.  This also relieves  the tension at the top of the sail, allowing the top of the sail to twist off,

Laser: vang or mainsheet to tight leech along whole sail and reduce twist

Albacore: vang to tighten leach at bottom, mainsheet to tighten leech at top.

Double-handers require you to manage sail tightness in two locations — above the forestay, the mainsail is acting like a jib (or like a Laser sail) and needs to be adjusted to the wind.  Below the forestay, the main’s job is different as it’s working the air through the slot instead of directly in the wind.  Use the vang and mainsheet tension to manage these two areas.  It’ll take some practice and getting used to (and I’m not confident enough in my ability to write about it).

YouTube for the win

RYA Rig tuning clinic: https://www.youtube.com/watch?v=mVFnnHGUIOs

 

 

 

Race Night Report – Thursday June 1, 2017

The high water (and fact that boats weren’t yet at the beech) meant that the June 1 race night was a practice race, and will not officially count towards the season score.  We did get a few boats on the water though to run through the course and work out some kinks in our race plan.

Weather

This was really the story of the night.  A forecast 10 knots (with gusts of 15) did not come to pass.  Instead, we got about 6 knots with gusts in the 12-20 range.  A couple of capsizes happened throughout the night, but those who managed to hold on were flying in the gusts.

The Results

Chunshu and Norm (Albacore), Ray (Laser), Carla (Byte) and Jason (Laser) braved the couple of races, but end results were not tallied.  Notably, Jason sailed the wrong course in the first race, and others apparently chose to follow (pro tip — never assume Jason knows what the heck he’s doing)

The Apres-sail, the RC, and other comments

Many thanks to Frank and Jean for bringing hamburgers and refreshments, and instructors Sydney and Reese for doing Race Committee duties.  They set a course and ran a couple of quick races, all while keeping an eye on the fleet from a safety perspective.  As a final note, the Ottawa Skiff and Cat Grand Prix (OSCGP) is running this weekend, and Nepean One Design (NOD) is running the weekend of June 14.  KSC members are more than welcome to take a KSC cat to OSCGP and to take an Albacore or Laser to NOD.  See nsc.ca for details on these regattas.

Advanced Sailing Skills – May 27, 2017

Little in the way of new theory discussed.  Carla did show a nifty trick for stepping a Laser mast if you’re light:

  1. Make sure there’s a tire under front of boat
  2. Stand mast beside boat (point head of mast into the wind to have wind help lift it)
  3. Stand on deck of boat
  4. Can now lift mast vertically onto deck of boat and into mast step

Alternatively, just sail a Byte and you don’t have to worry about the mast.

Since there’s not much else to write about, I’ll mention log books.  If you don’t keep a log book, I recommend doing so.  Sometimes it’s fun to look back at past sails.  Sometimes you’ll remind yourself of a long-forgotten tip.  My typical log book entry looks something like this:

May 27, 2017 – KSC Advanced Skills
Forecast: 6 knots from the W, sunny, high of 24
Observed: About 4 knots with occasional gust of up to 6, coming from S.
Boat: Tasar (blue)
Plan: Sail into the gusts, if available.  Work on using heel to facilitate steering both tacks and gybes.  Since this is first time sailing with Frank in a couple of years, focus on communication between skipper & crew.  Tasar likes to be sailed flat (even more so than Laser) so work extra hard on keeping boat level when we’re not trying to turn.
Postmortem: Communication with Frank was excellent in both directions, regardless of who was skipper and who was crew.  Heel during turns was working out well, although occasionally heeled in the wrong direction (1/4 of the time, maybe).  Rounding leeward mark was easy regardless of whether we approached on starboard or port tack.  Had trouble picking starboard layline to windward mark, and often came at mark on beam reach.
Lessons learned: Tasar points higher than the Lasers I’m used to — take this into account when calling layline.  Don’t forget to rotate Tasar wing mast when crew.

Doug Peckover (world class Laser sailor and author of Improper Course blog) goes into much more detail in his log entries than I do (here are his logs from the 2016 Worlds in Mexico)

Advanced Sailing Skills, – May 15, 2017

Introduction

This off-the-water class was concerned with the physics of sailing.  Tom did his “Theory from Hell” lecture (thanks, Tom!) and Reese spoke about how to apply the forces generated to the actual boat.

I’m going to present the information in a bit of a different order than was listed in the class.  I’ll talk about the forces on a boat first, and talk (briefly) about how the sail force is generated later.  We’ll discuss laminar flow, turbulent flow, and finally apparent wind.

But first… ready to take a review of Grade 12 Math?

Vector Math

A scalar (like the number 8) is a mathematical representation something that has magnitude (or size, or quantity).  A vector is a mathematical representation of something that has magnitude and a direction.  Forces on an object can be represented by vectors that are made up of how strong the force is (the magnitude) and which direction the force is pushing (the direction).

On diagrams, force vectors applied to an object are often drawn as arrows.  The direction of the arrow shows the direction in which the force is applied.  The placement of the arrow shows where the force is applied.  The length of the arrow shows how much force is applied (the longer the arrow, the more force).

We use vectors in sailing to understand how forces affect the boat, how apparent wind changes as the boat moves, and to understand how the heck we can sail “into” the wind.  Don’t worry, we won’t be doing number-crunching.  We’re more concerned with “push here to turn left”, not “calculate how fast you turn left when you push here exactly this hard”

Breaking down and summing vectors

Just like scalars can be added together (8 + 6 = 14) vectors can be added.  If the vectors are in the same direction, adding them up is just like adding numbers (if the wind is blowing 6 knots from the north, and speeds up by 6 knots from the north, then the result is that it is blowing 12 knots from the north).  When vectors have different direction, the adding is not quite as simple (if the wind is blowing 6 knt from the north, then speeds up by 6 knts from the east, then the result is 8.5 knots from the north-east).  We won’t be doing any number crunching or trigonometry, it’s just something to be aware of.

Just like adding two vectors into one vector, a vector can be broken down into two (or more) smaller vectors called components.  In the above example, a 8.5 knot wind from the NE can be thought of as “6 knots from the N and 6 knots from the E”.  Vectors are usually broken down into components that are perpendicular to each other (like N and E), but you can break them down into components of any direction as long as they add up to the same thing.

We’ll see summing and breaking down vectors more as we analyze how the foils counter the sail and how the apparent wind works.

Torque

In the real world, when we push or pull on something off-centre, it tries to turn.  Let’s take the example of a canoe floating beside a dock.  If we push on the middle of the canoe, it moves sideways.  If we push on one end, it moves sideways, but also tries to turn.  This turning force is called “torque”.  If we want to turn the canoe only (without it moving sideways) than we can push on both ends of the canoe in opposite directions.  The “sideways” parts of the pushes cancel each other out, but the torque from each push is added.

The torque produced is proportional to the distance from the pivot point.  That is, if you push with the same force at a distance twice as far from the pivot point, then the torque is doubled.  That’s why it’s easier to loosen a bolt with a long wrench than with a short one.

Equivalency Vectors

Dealing with tonnes and tonnes of vectors is hard.  Often times though we can replace lots of vectors with one vector.  Let’s say that you have a bunch of people pulling or pushing on an object to move it.  For the purpose of analysis, you could replace all the forces that people are applying with a single force that represents the sum of their effort.  As long as the equivalent vector applies the same net force as all the individual efforts, and the same torque as all the individual efforts, you can concentrate only on the one vector to make the math easier.

Forces on the Boat – CE and CLR

The Sail, and Centre of Effort (CE)

The wind blowing across a sail generates a force on the sail.  This force is part forwards, part sideways.  Got it?  Good!  Hey, that was easy!

While the sail actually has lots of little forces pushing against the sail all over it (perpendicular to the sailcloth), you can imagine it as one big force.  This force (which we’ll call the effort) is applied about 1/3 the way along the sail and about 1/3 the way up the mast (in other words, not quite the middle, but pretty close to where the sail is “baggiest”).  The point at which the force is pushing is called the Centre of Effort, or CE.

The direction of effort is (roughly) perpendicular to the sail at the sail’s deepest point.  It generally points forwards some amount, and to leeward some amount.  A fuller or tighter sail can change the direction somewhat, but it’s okay to think of  it as pretty much perpendicular to the sail.

CE on Boats with 2+ Sails

The above talks in terms of CE in a boat with a single sail.  The principals are the same for a boat with a jib.  Some points before we take a look at double-handers:

  • There are two sails generated forces — we’ll have to add them up
  • The main is usually bigger than the jib, and usually generates more force — our combined CE will be dominated by the main’s contribution
  • The mast is usually a bit farther back on double-handers

This means that the force generated by the main is a bit farther back in the boat, but we have a new force generated by the jib forward.  The jib force is generally smaller than the main.  The sum of these two forces is between the two individual forces, but closer to the main force.

The total CE generated by the sails will generally be close to the mast, but a little bit behind.

Some boats have a third sail that goes in front of the jib called the spinnaker (typically only raised when going downwind).  This sail also generates force and the CE will be moved forward farther when the spinnaker is raised.  The same principals apply on boats with multiple masts, or multiple sails.

The Foils, and Centre of Lateral Resistance (CLR)

This one is not quite as intuitive as the sail(s).

Picture a canoe.  The canoe is easy to push forwards/backwards, but tougher to push sideways, right?  The shape of the canoe (narrow in one dimension, wide in the other) resists the sideways motion.  This is called “lateral resistance”.

Sailboats have hulls that produce some lateral resistance, and the rudder produces some as well (when it’s straight), but the majority of the lateral resistance comes from the centreboard (or dagger board, or keel, or whatever you call the “fin” that sticks down into the water — I’ll just call it the centreboard).  A few sailboats (like the Hobie 16) don’t have boards, so the hull is shaped to provide extra lateral resistance.  For the purpose of this analysis, we’re talking about boats with boards.

Just like we were able to take all the little forces on the sail and come up with an equivalent force applied at the centre of effort, we can take all the little lateral resistances and do our analysis based on a single force generated at the “centre of lateral resistance” or CLR.  Since we’ve already mentioned that the centreboard is providing most of the lateral resistance, you won’t be surprised to learn that the CLR for the whole boat tends to be pretty close to the middle of the centreboard.

Sailboats generally produce a lot of lateral resistance, much more so than a canoe.  They make so much, that we often “cheat” in our analysis and say that the boat doesn’t move sideways at all.  If we apply 100 pounds of sideways force to a sailboat, we’ll say that the boat produces 100 pounds of resistance, and doesn’t move sideways.  It actually does move sideways a little bit, but for the purpose of this write up we’ll say it doesn’t.

A note on terminology — “foils” or hydrofoils are the thin blades move through the water and generate forces.  In the boats we’re talking about, the centreboard and rudder are the foils.  There are a few types of boats which have horizontal or angled foils.  Rather than produce a force to resist the boat moving sideways these produce an “upwards” force to help lift the hull out of the water.  You can get some pretty amazing results with this, but when this page talks about “foils” we’re taking centreboard and rudder, not lifting foils.

Drag

Just like a boat resists moving sideways, the hull and foils of a boat also resists moving forwards or backwards.  This resistance is called “drag”.  Drag is usually much less than lateral resistance though.  (Warning: math incoming) Drag tends to increase proportionally to the square of speed of the boat.  That is to say, a boat going twice as fast generates four times as much drag, everything else being equal.

In a moment we’ll see a sail generate a forward force on the boat.  We know that an unbalanced force causes something to accelerate (Newton’s 2nd law).  As the boat speeds up, the drag grows until the forward force equals the drag force (at our top speed).  Later on in the class, we’ll be (I assume) talking about things we can do to reduce drag to increase our top speed.  For now though, our analysis does not take drag into account.

Applying CE/CLR

Analysis without considering torque — how does a boat sail  upwind?

We’re going to first consider a beam reach (we’re sailing perpendicular to the wind) because it makes more intuitive sense, at least to me.

For the purpose of this analysis, we’ll consider all forces as if they act on the “middle” of the boat, without generating torque.  That part comes later…

Adding Torque to the Equation

Terms to know – weather helm and lee helm

I’d like to talk about two terms we’ll be using.  For some reason, the direction the wind is coming from is sometimes called “wind” (as in “windward”) but it’s also sometimes called “weather”.  The direction the wind is blowing to is “lee”.  The various forces on the boat might be exerting a torque on the boat, trying to turn it into the wind (“weather helm”) or away from the wind (“lee helm”).  Most boats are designed to have a small bit of weather helm when sailed properly.  This will turn the boat into the wind and stop the boat if the skipper falls off or lets go of the rudder, or something.

Torque to roll the boat

Probably the easiest effect of torque to understand is how a boat stays upright.  That’s because we’ve all hiked out on a boat, and we’ve all experienced the effects of moving around while hiking.

We have the wind pushing on the sail.  For this analysis, we’re looking at just the “sideways” part of how the wind pushes, and not the forward part.  The wind is pushing some distance up the mast, at CE.  Counter to this, we have the lateral resistance in the opposite direction somewhere below the waterline.  Remember our canoe example at the top of this post?  The two forces pushing in opposite directions some distance apart are working together to torque the boat around a pivot point.  In the diagram below, these forces (red) are producing the red clockwise torque around the pivot (purple X).  This is the torque which will heel the boat and capsize if you don’t do anything to stop it

To counter that torque, we need to exert an equal amount of torque in the counter-clockwise direction.  We do this by hiking.  Gravity exerts a force on our body, which is transferred to the boat using our legs as levers.  The heavier we are (the more downward force) or the taller we are (the farther away from the pivot the force is applied) the more torque is generated.  Jason uses this as an excuse to have a second helping of desert.  You want to apply just the right amount of torque such that the boat stays flat.

Let’s look what happens when the boat heels.

First, there is less sail area presented to the wind, so the sideways force (red arrows) become smaller.  Second, the CE moves “down” toward the waterline as the mast tilts.  The CLR moves “up” as well.  All this means the red vectors (which are smaller anyway) are vertically closer to the pivot point, providing less torque.  The net result — less hiking force is needed to keep the boat steady.

In strong winds, even the tall heavy sailors can’t generated enough torque to keep the boat flat.  Most of the time, you’ll see a fleet of Lasers sailing along, all with a bit of heel according to the skipper’s ability to generate righting force.  Good Laser sailors know that sheeting out to spill some wind (reducing the size of the red vectors) results in a flat boat and less drag, and generally go faster than the kids who try to hold all the wind in their sail and heel too much.  To put it another way, the good sailors will generate as much torque with their body as they can, and then adjust their sail to their body.  The other sailors will try to generate as much sail power as they can and then wrench their body trying to tame it (and fail to do so).

If you get a chance to watch Steve Harrington on the water at a KSC club race, he’s a perfect example.  The guy’s 145 pounds, 5’6″ and his Laser is dead flat in even the strongest winds.  He’s also winning every race.

Torque Affects of CE and CLR on weather helm and lee helm

Let’s look at the boat from the top.  This is similar to what we did when we looked at how we sail upwind, but now we’ll look at the torques the different forces generate.

The boat will tend to pivot at some point between the CE and CLR.  The two sideways components (blue and purple) will together torque the boat in one direction.  If CE is behind CLR, then they’ll be rotating the boat into the wind (weather helm).  If CE is in front of CLR, then they’ll rotate the boat away from the wind (lee helm).  If they are perfectly lined up with each other, then they won’t be torquing the boat at all.  The forward component of the sail (green) will however torque the boat (weather helm), even if CE and CLR are perfectly in line, since it’s pushing forwards off-centre to the pivot point

Moving CE/CLR to steer

Let’s take a look what happens to CE and CLR around the boat.

Let’s say you were to move CE forward in the boat.  What would happen?  The sideways components (purple and blue, above) wouldn’t have has much leverage around the pivot point, and you’d have less weather helm.  If you move CE so far forward that it’s in front of CLR, you’re actually generating lee helm with those sideways forces.

Now what about that green “go forward” component?  If you roll your boat to windward (that is, towards the right side of the diagram above) then you can move your CE to the point where it is directly above CLR.  This would eliminate the green torque component.

How would you move CE forward (or back) in the boat?  Sheeting the main in would move CE farther back and in towards the centreline.  Sheeting out would move CE forward, but away from the centreline.  Sitting farther forward in the boat would tilt the mast forward (and tilt the centerboard backwards) to move CE/CLR forward/back.  Hiking the boat to windward would move CE towards the centreline, and heeling to leeward would move it away from the centreline.

So to steer without a rudder you would:

  • To turn into the wind, generate weather helm
    • move back in the boat to move CE backwards behind CLR (more blue/purple torques)
    • stop hiking so hard, let the boat heel to leeward to move CE out and away from CLR (more green torque)
    • sheeting in would increase force from sideways components (more blue/purple force, thus more torque), move CE back (more blue/purple torque) but would also move CE in towards the centreline (less green torque).  Sheeting in is usually a net gain in weather helm
  • To turn away from the wind, generate lee helm
    • move forward in the boat to move CE forward ahead of CLR
    • hike harder, heel the boat to windward to move CE in closer to the centreline of the boat (less green torque)
    • sheet out to move CE ahead (reduces blue/purple torques, but increase green torque).  Sheeting out is usually a net gain in lee helm

On a double-handed boat, you can also use the jib.  Picture the scenario where you let one sail (either the main or the jib) do all the work, while the other one just flaps around

  • if you’re using the jib to generate all your power, the CE is very far ahead of the CLR, and you turn away from the wind
  • if you’re using the main to generate all your power, the CE is very far behind the CLR, and you turn towards the wind

Thus, it’s quite easy for a single sailor to sail a double-hander without a rudder — let one sheet loose, and yank on the other.  You can play with how much of each sail you’re applying until you find a balance that keeps you straight.

How a Sail Generates Forces

I’m not touching this one.

There are countless articles written about how a sail generates force, many of which contradict each other.  Most resources you’ll find online either

  • oversimplify things to the point at which they are flat out wrong
  • present part of the physics while ignoring others, leaving questions unanswered
  • insult people who present a different model of how a sail works
  • all of the above
  • all of the above, and then they claim that you’re just not smart enough to understand

In other words, it’s the airfoil teaching effect:

(image used with permission, original source https://www.xkcd.com/803/)

In my humble opinion, knowing how to use the force is more important than knowing the details of how it is generated.

Turbulent and Laminar Flow

I will speak briefly on turbulence.  A fluid (air, water, etc) will tend to flow in nice straight lines (laminar flow).  When it encounters an object, it has to go around the object.  If the object is fairly small, is nice and smooth, and allows for gradual flow around the object, you can have laminar flow around it.  If the object forces abrupt changes in the direction of the fluid, you create turbulence, and eddies or swirlies are introduced into the system.

When laminar flow is established can be harnessed to generate the sail and foil forces with minimal drag.  When a flow becomes turbulent the amount of force we can generate drops significantly, and the amount of drag increases.  To put it another way, we’d like all the fluids moving around our boat to have laminar flow if possible.

How do you know you have laminar flow?  Look at the tell tales on your sail.  If they are streaming backwards, they’re getting caught in the laminar flow as the wind blows across your sail.   Great!  If your tell tales are spinning around, flapping forwards and then back, or other erratic behaviour, then they are getting caught in one of the eddies, which indicates you have turbulent flow.  Turbulent flow means your sail is not generating as much power, and there is more drag on your rig.

We can’t see tell tales on our foils, but we can look at the water behind the boat.  If the water in our wake is relatively smooth, then then foils are not generating much turbulence.  If our wake is full of bubbles, and little whirlpools, then its and indication that our hull is dragging significantly.  Reducing hull drag is beyond the scope of this write-up, but try sitting farther forward in the boat and using less rudder if possible.

Apparent Wind

True wind is what the wind is doing relative to the ground (or water, or other stationary point).  You may be in a lull, or a gust, or just steady wind.  Whatever the case, if the wind is blowing 10 knots from the North relative to the surface, then that is the true wind at this point in time.

Induced wind or boat wind is the wind that’s created by moving across the surface.  If the true wind is dead still, but you’re riding a bicycle at 30 km/h then you “feel” a wind on your face as if it’s blowing 30km/h right at you.  That’s induced wind — wind created by your motion over the ground.

Apparent wind is the combination of the two.  Let’s say the wind was blowing at 10 km/h and you were riding a bike at 30 km/h directly into the wind.  You would “feel” 40 km/h (10 km/h true wind, plus 30 km/h induced wind).  If you were biking away from the wind, you would feel 20 km/h.  If you were biking sideways to the wind, you’d “feel” the wind come at you at about 32km/h from and angle about 32 degrees.

When you are travelling slow, the induced wind is small, and apparent wind is pretty close to true wind.  When you are travelling very fast the apparent wind becomes closer to the induced wind.

You’re sails operate on what they feel — the apparent wind.  So if you’re at a standstill on a beam reach, your sails “feel” the true wind coming from directly beside you.  As your speed increases, you’ll be generating more induced wind.  This will make the wind “appear” to come from more in front of you.  As you speed up, the boat may move from a beam reach to a close reach, even to close hauled just be speeding up.

Another example is gybing a Laser in strong wind.  You want to be going as fast as possible when you gybe.  If the wind is blowing at 20 knots, and you’re going 5 knots in the direction of the wind, then there’s 15 knots of apparent wind coming behind you.  Tough as hell to gybe that.  But, if you’re going 15 knots downwind, then there’s only 5 knots of apparent wind coming behind you.  That’s a walk in the park!  So catch a wave, get up on a plane, do whatever you need to do to speed up that boat heading into that gybe!

Side note – Some boats can sail faster than the true wind on reaches.  That’s because it’s not the 5 knots of true wind that is operating on the sail, it’s the 20 knots of apparent wind that the sail is using.  The 29er, for example, will sail at a speed of about 18 knots on a broad reach in 12 knots of wind, and you’re actually “tacking” through the apparent wind when you gybe.

 

Social Sailing on Friday Evening

Friday night socials at KSC are now underway.
On Friday night we just sail – no course, no scores. Then we take time to enjoy a Potluck Supper on the deck. It is a great way to bring on the weekend and our deck is without a doubt the best in town.
Social Sailing is every Friday night all summer long.
Grab a burger, grab a beverage and join us on the water and on the deck.