This is a log book for my 49er.

Thursday, August 11, 2005

What to do with no wind

August 11, 2005.

So a couple of weeks ago, we got down to the club, and there wasn't a breath of air (fairly common for English bay on a summer evening). We decided to practice foot work to see if that would make a difference with the boat handling, and it has since resulted in one of the biggest improvements we've had yet.

We left the boat tied to the dolly, setup the rig, put on our harnesses, and took turns experimenting with foot placement, hand coordination, and general positioning. On the water the results have been excellent, and we can now complete most gybes in breeze over 12kts without getting wet. Further, the same footwork generally applies in the tack, although the crew doesn't have to stop in the middle of the boat to sheet. Below, I have some diagrams of our foot placement as we come through the gybe, based largely on the steps from the previous post.




Setup
. Helm calls "ready to gybe," crew responds, then the helm calls "turn," and initiates the bear-away. Keept the boat flat or slightly to windward into the turn. Don't leave the wire too early.

Key tip: as the helm, steer underhand (frying pan style). This way, as you work your hand down the tiller extension when you move into the boat, you never have to let go or shift your angle. The control is much better.

Step 1
. Assuming both team members are on the wire, lead in with your aft feet. Helm is ready to step quickly into the middle since he has the best connection with the boat and its balance as he steers. By leading with your back foot then taking the next step down into the cockpit, you are facing most aft at this point, which is OK: focus on steering for balance. Take extra steps if you need to. Crew is heading for the middle of the boat.




Step 2. Crew has taken two big steps into the boat. He squares up in the middle, crouched under the boom, and sheets the spinnaker across as fast as possible, bringing it tight in. This is also when the helm crosses under the boom. As the helm crosses the middle boat (heading directly downwind), make a small 'S' turn back to centre the helm, flatten the boat, and allow a smooth hand exchange to the new tiller extension. Use the same hand as before. Once crossed, the helm places his old forward foot (red) inside the cockpit, and old aft foot (green) up on the wing: the helm is facing forward, and makes the tiller exchange. Keep the mainsheet in the same hand as the new tiller (new aft hand). Keep you head up and look for your new direction.



Step 3. Move out on to the wire. Helm starts to head up (big turn), clipping in with his free forward hand. Crew moves out to the wing facing forward with the sheet in the new aft hand. The crew feeds some sheet out to power up the boat as he moves out to the wire. He clips in with his free forward hand as well.

For the helm, the key points to remember are
  1. Smooth, positive turn
  2. Steer underhand
  3. Make a small 'S' correction when crossing to the new tiller extension
  4. Make the tiller exchange facing forward with one foot out on the new wing
  5. Keep facing forward with your head up
For the crew, the key points to remember are
  1. Plant your feet in the middle of the boat
  2. Sheet all the way around and pull the kite in tight
  3. Move to the new wing with the sheet in your aft hand
  4. Going out on the new wing, face forward
Practice, practice, practice kids.

Thursday, July 28, 2005

Gybe

July 28, 2005

It has been a while since the last post, but there has been no shortage of sailing in between. Despite a brief hiatus while I went to Ontario for a week, Trevor and I have been out half a dozen times, and Sue and I got some time in a Laser II. Trevor and I have been working on tacks, and as a result we've seen a lot of improvement. The boat is flat through the tack, and my tiller exchange is much better. The steering is more smooth as well. We have done some tacking drills (30s timer) and some of our best tacks have us wire to wire in a little over 5 seconds.

Gybes are a different story. Trevor and I have been out in some 14+ breeze now, and gybing is catastrophic. We are now very good at packing the chute from the capsize position. In lighter wind, the turn is slow enough that we can correct for balance as long as we stay on our feet. As the breeze builds up, things happen much faster. The deceleration in a bad gybe is much more intense and as the boat loads up, it is impossible to control. We have even noticed this with two sail gybes.

There is an instructional video for skiff sailing which has a segment on gybing. A small clip is available on the site where we get to watch two professionals do it in slow motion. We each have two hands and two feet, and they each have one or two important jobs to do in the manoeuver. The following is a breakdown of the gybe.
  1. Synopsis
    • Begin turn on trapeze
    • Both helm and crew move to middle of the boat in tandem
    • Crew stays in the center to sheet the kite through, helm moves to wing and exchanges tiller
    • Crew chokes off kite and helm heads up high, moving on to wire
    • Crew moves to wire, sets spinnaker
  2. Initiation
    • Boat
      • Flat/slight windward heel
      • Sails trimmed for speed
    • Crew
      • Stay on wire until turn is initiated
      • Helm calls "turn"
      • Sheet is in aft hand, forward hand is free
      • Sheet in 1/2 arm length as you draw yourself on to the wing
      • Free hand unclips
    • Helm
      • Steering is underhand
      • Call "turn" and initiate turn while on the trapeze
      • Apply enough helm to drop the windward wing ~30cm
      • Ease mainsheet, and use mainsheet hand (forward) to unclip
  3. Entry
    • Boat
      • Slight/moderate windward heel
      • Main is off, spinnaker is going forward
    • Crew
      • Move directly into the centre of the boat in tandem with the helm
      • Take the new sheet from the block with the hand on that side of the boat (facing forward) as you finish the move to the centre
      • Plant feet stradling the centreline, forward of the main sheet block on the boom
    • Helm
      • Move towards centre of the boat, lagging crew as neccessary for balance
      • "Walk" tiller hand down tiller extension in three steps until holding it nearly at the joint. Hand never leaves tiller.
      • Keep turning lightly
      • Mainsheet remains in opposite hand
  4. Gybe
    • Boat
      • Flat
      • Main soft, kite blows forward
    • Crew
      • Sheet hard to pull the chute across from position in centre of boat
      • Sheet spinnaker all the way in (choked)
      • When the chute is in tight, call "made"
      • Kite should "float" through the gybe (it blows forward when headed downwind)
    • Helm
      • Pause just before centreline on the old side (balance)
      • Steer a slight 'S' before transitioning to new tiller extension
      • Don't stop moving across the boat, passing just behind the main sheet block
      • Work up new tiller extension with old tiller hand until on the new wing
  5. Exit
    • Boat
      • Flat as possible - keep the old wing dry
      • Pump main in, trim spinnaker
    • Crew
      • Spin sheet in new aft hand, spinnaker in tight
      • Move to wing, feed out some sheet to set spinnaker
      • Free hand grabs the puck (facing forward), move out to wire, rotating
      • Use the sheet hand to bring the clip to the hook
      • Trim spinnaker
    • Helm
      • Standing on the wing, complete tiller exchange behind back
      • Keep mainsheet in new tiller hand
      • Accelerate turn when the crew calls "made"
      • Use free hand to move on to the wire (should be on the wire before the crew)
      • Large turn upwind to power up boat - boat should travel through > 90 degrees, up to ~120 degrees
      • Main sheet to free hand, pump main in to support weight on wire, accelerate
Notes about hands and feet.
  • Crew
    • Forward hand is free for the trapeze, aft hand holds the sheet
    • Use the new aft hand to start bringing the spinnaker through the gybe
    • Keep feet planted in the centre while sheeting the spinnaker across
    • Move directly to wire
    • Stay forward of the mainsheet block.
  • Helm
    • Forward hand is mainsheet/trapeze, aft hand holds the tiller
    • Keep the tiller in the same hand until on the new wing
    • Keep the mainsheet in the same hand until on the wire (new tiller hand holds mainsheet)
    • Keep feet moving through the gybe
    • Stay behind the mainsheet block
We'll see if this works. After the call for "turn," there is really no time for communication, and the execution must be highly synchronized. Since balance is so critical, helm control is incredibly important. It will take some practice to get it right.

Wednesday, July 06, 2005

Spinnaker

July 6, 2005

I'm sure that I will run out of words for spinnaker long before I run out of experiences. Picking up where the previous post left off, we had a marathon session Thursday night in a decent easterly. We basically did laps from English bay to Spanish banks and back, working on tacks upwind and gybes down wind. We both fell off the boat on the runs (separately), so we got to practice bringing the boat up with the chute in the water.

Saturday evening, I had a little sail with Sue in light air. We just goofed around, and she's getting more comfortable with the boat. On Monday, we didn't get out because the wind didn't show up, but we made it out in the rain Tuesday. It started out as a moderate easterly, and we had a good sail up wind into English bay. Tacking was ok (we finally tried some twin wire-to-wire tacks), but even better was the boat control. We kept the boat reasonably flat and powered in a good range of gusts and lulls - good balance and good control. Then we popped the kite, and things got interesting.

Thursday June 30, 2005

Tacking. We focused on roll tacks in light air. It's hard to roll a 49er the same way you would a Laser. During the tack, the wings cannot touch the water or the boat stops. To initiate, give the boat a few degrees of leeward heel, but more is unnecessary - a good visual aid is to get the wing horizontal. Start the turn slowly, and accelerate it as you come head to wind. On the new tack, let the boat heel such that the leeward wing is almost in the water. Skipper and crew move to the windward wing to pump the boat: the crew gives a hard tug on the mainsheet and this sets the battens. The skipper stays out to drive while the crew moves back in to balance. As the skipper, it's good to grab the trapeze as you pump the boat, but there's no need to clip in right away - get the boat moving first, then settle in. Once you've established your new heading, get the weight forward to free the transom. Foot a little bit if necessary to establish speed as quickly as possible.

Gybing. Nothing seems to stop and destabilize this boat faster than steering dead downwind. Initiating the turn to gybe takes the pressure off the sails, and the boat tends to roll to windward. A quick sketch below shows why - with the boat moving faster than the wind on a broad reach, the apparent wind (AP) comes from ahead. As the boat bears away and decelerates, the true wind (TW) and boat wind (BW) nearly cancel, and the AP drops nearly to zero. Balance becomes critical.



I discovered on the last gybe a steering trick which seemed to help. On the bear away, the rig will roll to windward. Before the wing reaches the water (near a dead run), stop the turn and jink a little back to windward: this will flatten out the boat and the chute will blow forward, making the gybe a bit smoother. It only takes a little turn to keep the boat from rolling, then you continue with the turn through the gybe. Head up to fill the chute and move out on to the new wing to keep the boat flat as it accelerates.

Tuesday July 5, 2005

Upwind. Under overcast skies with a moderate easterly (8-12kts) we tacked upwind from Jericho. With this wind, we were both trapezing. By the end of the leg, Trevor's response with the main and his body position was really in tune with the wind. It wasn't as weak and shifty as we saw last week, which made things easier, but his movements and sail handling kept us flat and fast. Once we were both wired, Trevor also got his first taste of the wire-to-wire sprint. With the boat moving faster, the tacks are faster. This highlighted the necessity for (a) a clean tiller exchange (which I still suck at), and (b) not oversteering through the tack. For a fast tack, the boat come around with such speed that you must move fluidly from driving on one side to the trapeze on the other side. It is really important to get that weight out on the wing as quickly as possible in moderate breeze so that the helm remains balanced.

Flight. As we entered English bay, the breeze had built, and we were running out of ocean upwind. So why not throw up the chute and cruise down the bay? I am now under the impression that nothing else offers more bang for the buck than this boat on a reach. I have been skydiving. It was the most terrifying, exhilarating, insane experience I have ever had on the water. I've also surfed in overhead waves. The boat was going incredibly fast. The helm is feather light, and every touch, every shift in weight has an immediate effect. Trevor was on the wire, and I was holding mine, but not clipped in. I had given up on the main sheet, and it didn't seem to matter. There was a healthy 0.6m chop, and I am still amazed that the bow didn't submarine. We shot out of English bay and were half way down the harbour off of Stanley park in about 10 minutes. We knew that we had to gybe, but it was not the most appealing manoeuver. However, we gybed without too much incident.

Then, as we headed up to set the chute on the new tack, we lost control of the boat and it rolled hard to windward. The wing dug in and the water washed me off the back of the boat, still holding on to the trapeze. I was dragging along behind the boat like a water skier, but Trevor didn't notice and snapped the sheet in. The boat caught and rolled back to leeward, launching me out of the water. I Tarzaned around back onto the wing, but with his weight in the middle of the boat and mine moving that direction, we had no hope of balancing it. The skiff then rounded up and capsized, turtling shortly after.

Recovery notes.
  • If the boat is capsized with the spinnaker up, the skipper must go and pack the chute in the water. Uncleat the halyard and stuff it in the sock.
  • If the boat is turtled, bring the boat to the capsize position then pack the chute. If the boat doesn't want to come up on one side, go the other way - use the wind against the wings to help you.
  • Make sure the jib is uncleated.
We remained in the water for about 20 minutes trying to get the boat back up. We eventually pulled the spinnaker out of the water and put it on the hull before getting it upright. It is a big ugly bag of water.

On a reassuring note, shortly after we got the boat up, we were visited by a tug, who had apparently been monitoring us. They had called the coast guard, who also showed up shortly after. It takes a lot of energy to get that boat back up once it's been all the way over, and it's a good rule of thumb to get off the water after you've been over twice. We'll give it another shot today, hopefully without all the drama.

Friday, July 01, 2005

New Crew

July 1, 2005 - One week roundup

I've seen a lot of sailing over the last week, hooking up with a new crew on Monday. Before that, Sue and I were out Thursday night for a brief sail up and down the bay, working a bit more on her balance in the boat. The sail was fairly uneventful, as we worked the boat through a few tacks and gybes.

On Monday, Tuesday, and Thursday, I sailed with Trevor. All three evenings brought fairly light, shifty breeze, giving us some good (if not tricky) wind to get into the boat. We experimented with crew positions in light air, tacking techniques, and spinnaker work. All in all, it looks very promising.

Thursday June 23, 2005

Sue and I finally got a night out where the wind wasn't too crazy. Launching in light air, I had my crew go into the boat first and set the blades 1/2 way. From there, with the skipper holding the boat in the water

  • Aim the bow on a beam/broard reach (note: light air)
  • Work back along the wing
  • Push the boat a little from astern, and climb in over the transom
  • Crew sheets in the jib, skipper helms away from the breeze to get the sails working and the boat moving forward

This works very well to avoid auto-tacking near the beach in light wind. Make sure the main stays off. It also puts all the responsibility for the boat with one person (the skipper). The rest of the sail was routine.

Monday June 27, 2005

Light air sailing with Trevor. Most of the interesting parts were upwind, although we did fly the spinnaker. In light wind, when the hull is not planing freely, it pays imensely to get the bow down and the stern up. The difference is immediately audible: when the weight is aft in the boat, the sten drags and water piles up at the back. Moving the weight forward frees the stern and the boat begins to quietly slip through the water. It is not the most comfortable way to sail, but the difference in speed is immense.

  • Crew goes forward, to the bow if necessary. Be careful when sitting on the spinnaker.
  • The skipper should take the main sheet
  • The skipper becomes responsible for boat balance, trapezing as necessary
  • A slight ammount of leeward heel keeps the sails filled, but too much heel is to be avoided - the indication comes when the stern begins to drag again
  • In puffs, the crew must move quickly to stabilize the boat - excess heel is slow

Practially, the last point causes the most difficulty. With the crew up at the bow, he cannot do much for balance. Bethwaite suggests that in a gust in light air, the best move is to ease the sails. The crew can take control of the jib from up forwards by uncleating it in the cockpit and playing the sheet. During tacks, the crew simply rolls under the jib.

We often sailed with Trevor in the cockpit on the leeward wing or between the shrouds (on whichever side was best for balance. He typically maintained control of the mainsheet, which made things easier for me. However, I noticed that the best performance boost came from having his weight in the bow. The key problem with this positioning was that when puffs rolled by, the boat was unbalanced; even with me trapezing and Trevor's weight on the windward rail, the boat would still dip sharply to leeward. We did not try the "easing" technique enough.

Sailing downwind under the spinnaker was fun. As I discovered with my brother, communication is essential, and we were able to keep the boat moving well. I found that I could steer the rig under the sail to control the boat (i.e. bear off as the boat starts to heel too much, and head up as the sails soften). With Trevor constantly updating the sail trim, driving was much easier.

Tuesday June 28, 2005

We went through a great deal of effort to rig the spinnaker correctly on Monday. From top to bottom

  • The tack line
  • The sheet
  • The retrieval line

The spinnaker is rigged for a starboard tack hoist (everything to port). Make sure that the sail is untwisted and the halyard is clear outside of everything (i.e. there is a clean line from the top of the mast to the tack). The sheet must go under the tack line: a triangle forms between the bow, tack (tip of the pole) and the top of the mast, and the clew must pass through this triangle on a gybe. When the tack line is pulled in to the tip of the pole, the sheet must be inside that triangle. The retrieval line goes under the sheet: on a starboard tack, the loose part of the sheet will drape over the retrieval line. When the spinnaker is gybed, the retrieval line will go infront of the forestay and will end up over top of the sheet.

If this makes no sense, try it! It's damn confusing.

After all that work Monday, we took the halyard off the spinnaker, then put it on underneath the sheet - we weren't able to hoist the chute on Tuesday.

So we worked on tacks. Things to remember include

  • Keep the boat flat through the tack. A little leeward heel to initiate the tack and a bit of leeward heel on the new side for a pump is OK, but the wings should stay well clear of the water.
  • The turn into the wind should be slow, increasing in speed through the turn.
  • Face forward, and look for the new course.
  • When the skipper drops the old tiller, pick up the new tiller with the opposite hand, and reach for the trapeze with the other hand.
  • A concerted effort between the crew and skipper pumps the boat on the new tack and sets the batten. The skipper should stay out, and the crew may move back in to balance the boat.

Things to work on include footwork in the transition, picking up the tiller on the new side with the correct hand, and coordination on the balance of the boat.

Friday, June 10, 2005

Chute

June 9, 2005.

Today was our first trip with the chute up. I was sailing with my brother again. The wind was ideal, and the sail was excellent. Another strange weather day brought mostly overcast skies (high overcast) and mild northwesterlies. The wind blew a steady 6kts - none of the shifty and gusty nonsense we'd seen last weekend. We sailed up to Spanish banks and back down to RVYC Jericho with some good tacks and a couple of spinnaker runs.

Sailing.
The launches and landings are starting to get more routine - with the crew taking care of the blades on the way in, landings have been very straightforward. Upwind, I focused on two things.
  1. Staying on the wind. With the jib in so that it is just lose enough to slide to the edge of the track, the sail has a very fine entry angle. I concentrated on steering to keep the boat as close to the wind as possible. I found it hard to judge by the inside telltale, so I would test by letting the boat bear away until the leeward telltale agitated, then I would head up until it stopped. If I was too close to the wind, I could feel the pressure on the sails fade rapidly.
  2. Keeping flow over the leeward side of the main sail. There is a big ribbon that streams from one of the upper battens. If the main were too tight, this ribbon would stall and collapse behind the main. If the main was positioned correctly, it would often stream and occasionally stall.
We kept the boat moving well upwind although my tacks are not that crisp - I'm still unsure about the tiller exchange. As we turned off the wind, we had success with the chute hoisting, sailing, and dousing. First, rigging notes:
  • The spinnaker sheet must go under the line connecting the tack to the pole. A triangle is created between the head of the sail (top of the mast), the boat of the boat (along the forestay), and the tip of the pole (returning to the head along the luff). The sheet must be inside this.
  • The retrieval line will pass under the spinnaker sheet (see this old post).
The handling of the spinnaker is straightforward (especially in light air). The crew passes the main sheet to the skipper. As the crew moves into the bottom of the boat, the skipper assumes responsibility for balance. We followed this hoist procedure:
  1. Bear away to a broad reach. The main will be out. Adjust the jib so that it is choked - when the boat accelerates, the AP wind will go forward. Skipper balances and focuses on driving smoothly down low.
  2. Crew goes on the hoist. The spinnaker goes right to the top of the mast.
  3. The crew regains the responsibility for balance. He takes the spin sheet and moves out towards the wing as he sets the sail with some curl in the upper luff.
  4. The skipper steers up to fill the sail. The crew trims and balances. At this point, the main sail will be soft to hold for the skipper, and will be brought mostly in as the boat accelerates and the wind moves forward.
  5. As the boat accelerates, bear away and establish your course. This should be a smooth procedure that coincides with the acceleration of the boat to keep the AP wind in the optimal position.
Steering downwind, it's best to start out steering under the rig. As you feel the boat start to heat up, heel, and turn to windward, steer to bear away. Communicate with the crew that you are making this adjustment so that he can ease the spinnaker as necessary. As the boat moves too far towards a run and you feel the sails losing pressure, head up. Again, communicate this to the crew so that he can sheet in.

At this point, you're flying and you've figured out why you got into this boat in the first place.

The gybe is also fairly easy to execute (especially compared to a boat with a symmetric spinnaker). An 'S' gybe is safest and easiest to execute. Focus on keeping the boat flat through the turn. The crew should wait until the spinnaker has backed across the forestay before releasing the old sheet - this should happen at the most windward point in the 'S' turn. The crew will set the sail on the bear-away. After everybody is comfortable again, the skipper can head up to heat the boat up on the broad reach.

On the douse, trip the halyard, and pull like crazy. Watch your elbows, etc. on the boom, and be careful that the halyard doesn't re-cleat itself. During the douse, the skipper is once again responsible for balance. After the manoeuver is completed, the crew takes the mainsheet and the boat is headed upwind.

Tuesday, June 07, 2005

Weekend Roundup

June 4-5, 2005

Wow. Was it sailing or swimming? It was probably hard to tell if you were watching us from the beach. With my brother back in town, I decided to take my boat out into some more challenging conditions. It was the weekend of the Jericho Classic regatta, and the weather was sketchy. Saturday brought partly cloudy skies, with a very interesting roll cloud formation.


The wind started out ESE in the morning, moving south by late morning. Surprisingly, the wind "stayed" south (rare), although it was very shifty (one racer reported that they sailed around the committee boat without tacking once). Hard gusts (est. 8-10kts.) would roll off the south shore at approximately one minute intervals, coinciding with the presence of a cloud overhead. Lulls would be in the 4-6kt. range. My brother and left the beach on his first trip. The launch was clean and we got out past the pier. The wind was southerly, so we figured we'd do a couple of tacks west of the pier. Instead, we instantly rounded the boat up and dumped. In the next 90 minutes, we managed to get the boat sideways four more times, reaching down to the RVYC pier and back in a clear demonstration of what not to do. The only saving grace was that we took the boat into the beach with the south on our nose, making the landing hassle free.

Sunday was a great improvement (not in the weather, but in the sailing). Under heavy overcast with the rain coming down, the wind picked up and was gusting from the east and southeast. Despite gusts up over 10kts, we managed to both get wired and keep the boat flowing up wind. We had some trouble (my steering, specifically) down wind, but otherwise had a good sail. Both the launch and landing were again clean, but my turn was still at little early at the beach.

Sailing Saturday.
Launching into the SE can be challenging because it requires a large bear-away starting from a standstill. The skipper goes on board to set the blades
  • dagger board as far down as possible so that the boat pivots around it,
  • rudder down to for steering through the bear-away.
The skipper then tightens the jib sheet as the crew forcibly pushes the bow around, pointing it away from the beach (basically on a beam reach). The crew may do this by working back along the wing and allowing the boat to swing around before climbing in. I witnessed a nimble crew climb over the wing, but if your balance isn't too good, it's best to come in over the stern. The skipper steers to keep the boat moving forward away from the beach.

During a capsize, there are a few things to note.
  • The most important thing to remember is to unhook before the boat goes over (jumping from the top of the wing is fun).
  • Don't step on the boom - step on the mast, or dive over the back.
  • Try not to fall on the sails. If you do, try to fall on your back so that the hook on your harness doesn't go through it. Spread-eagle to distribute your weight on impact.
  • The boat goes over pretty slowly if you do a standard "round-up" capsize. Once the wing is in, the boat doesn't rotate too quickly, so you have a bit of time.
To bring the boat back up, there are also a couple of things we found out.
  • Don't put your trapeeze hook down anywhere - you make holes. When climbing on to the daggerboard, be very careful not to go on your belly.
  • Having the boat turn turtle isn't so bad. Stand on the edge of the wing, lean back, and it will come back to horizontal.
  • You can't bring the boat up if it is sideways to the wind (hull facing the wind). The wing acts like a sail, pushing the boat over. Turtle the boat and bring it up the other way, so that the wind will catch the wing and help you bring it up. Whoever gets on first will need to sprint to the windward wing to keep things flat.
  • It can be a pig. Be careful not to get too tired.
When handling the boat through turns, it is incredibly important to stay out of the bottom of the boat. Every crash we had could be attributed to two things: poor steering and poor balance. This seems like stating the obvious, but is worth thinking about: before initiating a turn, remind your crew and yourself about position and balance. Either heading up or bearing away when underpowered will heat the boat up and both sailors must move out accordingly. It is too late half-way through the turn, and you'll be swimming. Heel to windward is necessary when bearing off, and OK when heading up. You also may be required to grab a trapeze wire to project further off the boat.

Trapezing changes the dynamics of the balance, and a little physics can tell you why. Three forces act to move and balance the boat: the driving force on the sails (pushing at the centre of effort), and the balancing force of the crew on the wing, and the daggerboard in the water (the last two are know as contributing collectively to the "righting moment"). Each of these forces can be thought of as a torque applied to a rigid rod fixed at the mast step. The torque applied to the mast and rigging by the sails rotates the boat to leeward, while the force from the foils and the weight on the wings rotates the boat to windward. Torque is given as the product of rotational force and distance from the centre of rotation. If there's a torque of 400N-m applied by the sails, and a 200N-m restoring torque from the foils, then another 200N-m is needed to balance the boat (The force due to gravity of a 20kg mass is roughly 200N: F = ma, where a = 10 m/s^2). This could be achieved by placing a 20kg mass 1m from the centre of the boat or 10kg mass 2m from the centre of the boat.

When the skipper and crew move out on to the trapeze, the dynamics change. The torque is no longer applied only to the wing, but also to the mast. Further, the force applied to the mast is further from the centre of rotation, which increases the torque. On the down side, the force is applied at an angle, and only the component of the force perpendicular to the mast will contribute to the torque. However, the fact that the length of the moment arm is greatly increased (i.e. where the trapeze is attached to the mast) is enough to make up for this.

Continuning from the previous example, if we take the 10kg that is placed at the edge of the wing, and support 80% of that mass on the trapeze, then only 2kg is left to contribute 40N-m of torque (of the 200N-m necessary). This leaves 8kg, or 80N of vertical force to be supported by the wire. If the wire is at an angle of about 36 degrees from the mast, and the vertical component of the tension force is 80N, then the horizontal component must be 60N. However, this 60N horizontal force is applied at a distance of 5m from the centre of rotation, for a torque of 300N-m!

By staying in place, and transfering your weight to the trapeze, you have increased the righting moment by 70%. You must be aware of the difference in effect of standing at the edge of the wing and trapezing at the edge of the wing to recognize the abrubt change in dynamics when you transfer to it.

Sailing Sunday.
My brother's balance improved significantly on Sunday. Having had a chance to think about the sail on Saturday, we were much better prepared, and picked up a couple of good tips from other crews on the beach before we went out. The most important of these tips was separation of responsibilities for skipper and crew.
  • Skipper. Upwind, the skipper drives and also re-trims the jib when the boat is settled. His other hand is free to go to the trapeze.
  • Crew. Upwind, the crew takes the mainsheet, leaving his other hand free for the trapeze. When the boat is stable, he may hand the skipper the jib sheet.
Both people then have a primary responsibility to balance. The skipper (or helm) achieves this through focused driving. The crew (or sheethand) achieves balance through body movement and mainsheet control. Communication is essential - keep talking about what you're doing.

In contrast to the diagram on tacking from a previous post (which is in the style of older double handed dinghies), the helm does not hold a sheet through the tack. The jib is self tacking and doesn't need attention while turning through the wind. This leaves him a hand to establish himself on the wire at the other side of the tack. The crew is left with the responsibility of controlling the mainsheet and his body position to balance the boat correctly through the manoeuver.

Sailing upwind this way, we kept the boat flat and moving fast in the gusty easterly. We were both wired, and completed a couple of successful tacks this way before getting into trouble heading downwind. Having learned a good lesson on Saturday, our bear-away was well coordinated and positive: we moved out smoothly to keep the boat flat as the boat turned to leeward. Things went wrong when I lost control of the helm, crash gybed, and put the whole thing in. It took a while to get it up.

After getting the boat back up, we luffed upwind for a bit to rest, but ran out of ocean as we approached Kits beach. We made another successful bear-away and started to head back to Jericho. Here I finally experienced first-hand what makes this boat so much different: on a broad reach, the wind comes from ahead on the quarter. This is very different. The boat sails faster than the wind, and since we were not adjusting the sails at that point, we noticed the following pattern
  • We would start with the boat stable in a lull and the wind on the beam. The sails were trimmed and the weight balanced. The boat is moving slightly slower than the wind.
  • A puff would overtake us and the boat would heat up. We would move quickly to windward to balance (I was hanging out by the trapeze) and the boat would accelerate rapidly.
  • The apparent wind would move forward.
  • The sails would luff and the boat would roll to windward - the boat would slow down and the puff would pass
  • We would re-stabilize the boat in the lull with sails trimmed.
Ideally, we would be trimmed to stay in the gust or slightly ahead - as the boat accelarates, we would bring the jib and main in or bear away. However, after I had lost the helm a couple more times, and jumped off the back once (my brother saved the boat and I made the "swim of shame" back), we were more interested in getting back to the beach. This is definitely a lesson for the next trip.

On the landing, the wind was soft near the beach, and we had no real issues. As the helm, I've found it best to have the crew work the daggerboard and rudder blade up 10cm while I steer, rather than trying to bring the rudder out myself. It's also convenient to take the main down while in the water.

Maintenance.
The dolly has eaten into the bow a bit, and the gelcoat needs repair. It hasn't been structurally comprimised, but it should get a little attention - one of these sunny days.

Saturday, June 04, 2005

Birthday

June 2, 2005.

Went for our first evening sail for my birthday. After a long day of solid 8kts from the west, the wind had quietly died by the time we got to the beach. This made launching difficult, and the trip a lazy one. I tried to show my crew what a transit was to illustrate that we were in fact moving through the water, but to no avail. The landing was easy.

Sailing.
The only point of note on this trip was the light air launch. When the wind isn't blowing, there's no flow over the sails, and with the full batten main, it's difficult to get the driving force forward of the CLR and establishing flow. The result is that we would push off, and the motion of the crew climbing into the boat would bring it to a stop. Without forward pressure on the jib to push the boat off the wind (even with the jib in), the main would just tack the boat back into the beach. The solution is to have the crew turn the boat and point it on a beam reach away from the beach. This is done by holding the boat at the wing and working back along the wing so that the pivot point is the aft quarter. The boat aims for open ocean, and the crew climbs in over the stern.

Transit.
A transit is a sight taken between two objects to determine the relative change in position between yourself and the nearest object. Two examples are commonly used in sailing
  1. The rhumb line. When you finally tack at what you think is the rhumb line and head for the mark, you want to know if you're going to make it. If you point as high as possible, you can then use a transit to aid you. Choosing the nearest object to be the windward mark, and a distinctive, fixed object on shore as the second reference, a transit is formed (i.e. the imaginary line between the two). If the mark appears to move downwind along the shore, then you are overshooting. If the mark appears to move upwind along the shore, then you may not make it. If the two objects remain in line even as you move towards the mark, then you are on the rhumb line.
  2. Crossing another boat. If you have just tacked and wish to know if you will 'cross' (in front of) another boat on an opposite tack, use the bow of that boat as the first point of reference and a fixed point on land as the second. If the other boat appears to move up the shore, then you will not cross, but if more shoreline appears, then you are on course to cross that boat.
Here is a picture.