Monthly Archives: August 2010

SL-VT Final Moments

The SL-Vuitton Regatta came to a close this past Saturday, with a five-hour string of fun, final matches unmarred by controversy or excess grid turbulence.

The excitement and fun of the competition was (rather brilliantly) captured by Surfwidow Beaumont’s camera!

Vodpod videos no longer available.

Although Surf said it all above much better than I ever could, that’s never stopped me from writing before, so let me tell you about a couple racing highlights!

Armano vs Hawk

Match racing is all about tactics.
There are only two boats involved, and the course is nearly always a simple Windward/Leeward affair that offers few strategic options.

LDeWell Hawker is a maestro at this; Hawk holds regular teaching sessions at Fruit Islands’ Strawberry Sailing Center to discuss and practice Match Racing skills. Stop by and go over his slideshow there, and try the race course!

Hawk’s own technical finesse was well-demonstrated in Tradewind Yacht Club’s first SLVT Qualifying Round, where he picked up First Place and earned a slot in the Finals line-up. It seemed pretty obvious that any sailor who wanted to win the SL- Vuitton Trophy would need to ‘get past Hawk‘ first.

Armano knows this too; when he and Hawk went head-to-head in their first matchup Saturday, the gloves came off and the fur went flying (Sorry for mixing metaphors 🙂 ). During the three minute prestart, the Terrific Twosome made a series of hair-raising close passes as they jockeyed for position and tried to force each other into a fault.

Click to enlarge.

With forty-five seconds to go, Armano decided he had enough. He turned and broke for the line. From a greater distance, Hawk set a course to intersect Armano at the Start.

The second frame above shows this approach setup with a half-minute still on the clock.  One might argue that in this raceat this point – Armano looked like he had outfoxed Hawk, the Prestart Professor. Armano held Leeward Right-of-Way, and had set course to slice the far starboard side of the line next to the buoy and committee boat. PERFECT.

Hawk had a vested interest in crossing that startline too, of course 🙂 … but Armano held the cards and could stave Hawk off… perhaps even forcing Hawk to miss the line entirely.

If you look at the sequence above however, it’s pretty clear that Armano broke for the line too early; that’s how he caught Hawk with his pants down (Hawk’s pants… not Armano’s 🙂 ). Actually that’s not an Armano error; in fact it’s a pretty interesting tactical nuance, but it meant Armano needed to adjust his plans to avoid crossing over early.

Armano elected to keep on his winning ROW course, but slowed his approach by luffing sails (third frame above). It was a conservative, prudent tactic, but it didn’t take into consideration Hawk’s skill and determination.

When Armano let loose his sheets and slowed his boat, he opened a narrow door  between his bow and the line; Hawk immediately saw it and locked on. Instead of following Armano’s lead and slowing down…  Hawk lit afterburners and strained canvas to speed up, playing a hugely risky juggernaut to clear Armano’s bow before the ‘door’ closed.

Click to enlarge.

Hawk successfully pulled off this gutsy maneuver, cleanly passing Armano with leass than one or two seconds to spare.

With the wisdom of Monday-morning quarterbacking, let me suggest that Armano may have had a second tactical choice here… Instead of luffing, losing momentum, and opening a door… Armano could have gone full steam up to the line, then made a hockey-stop turn to Port to avoid going ‘over early.’ That would have ‘closed the door‘ to Hawk, flashed Armano’s butt in Hawk’s face, and allowed Armano to run the length of the line full speed, waiting for the START signal to cross.

I’ve had 24hrs to look at the pictures though; Armano had under ten seconds 🙂 . Armano won this whole darn regatta, so I’m not criticizing; I’m mentioning alternatives here to help sailors figure out Armano’s weaknesses!

Based on his prestart tactics above, I’m thinking Armano may have a serious character flaw… one sometimes found in otherwise excellent Dutch Sail Racers…
Armano is very Polite and Careful.
🙂

Anywayz, after Hawk’s rather brilliant move, the two boats crossed the line in near-tandem, as shown in A above.

These are two outstanding sailors, and its certainly no surprise that they stayed fairly closely glued to each other on the multi-sim downwind beat. For most of that way, Armano held a breathtakingly slim lead.

As the boats came around Ahab’s Haunt and set sail for the downwind ride to Rachel and then Home, here’s the conversation from the Judge’s chat:

[10:18:11]  Silber Sands: Jane You see them?
[10:18:16]  Jane Fossett: yes
[10:18:22]  Silber Sands: ok:)
[10:18:23]  Jane Fossett: any protest
[10:18:30]  Silber Sands: no
[10:18:37]  Jane Fossett: they are very close;  Armano by one boatlength.
[10:20:17]  Jane Fossett: Here is where Hawk will make the move.
[10:20:33]  Elizabet Foxtrot: nods; There he goes!

As shown above, Hawk swung leeward of Armano and began to pass… Hawk then did another rather surprising move. The ACAv2.53 boats have fairly powerful downwind shadow, so a trailing boat has a fair chance to come even with a leading opponent. However, it’s much tougher to then pass and capture the lead, since the passing boat loses shadow advantage in doing so. There are many, many examples of ‘failed passing attempts’ in the SLVT races.
But look at what Hawk does.

As soon as he came up abeam and overlapped, Hawk fell away, increasing the distance between the two boats and securing ‘clean air’ outside the most intense shadow range. NICE MOVE.

Click to enlarge.

If you look at the sequence above, you can see how the boats next handled the final turn in Rachel sim before they set their eyes on the Finish line. Hawk played his cards adroitly, squeaking ahead of Armano as they approached the turn. Armano was further starboard, and he decided to swing wide of the submerged shipwreck obstruction there.

Room at Obstruction

This is probably a good place for me to bring up a somewhat separate issue, “Room at an Obstruction,” since it came up several times in SLVT, and both Lynn and Takabou commented on it in Rachel.

There is a submerged shipwreck in Rachel, rather inconveniently positioned near the race marker in that sim; the hazard is marked by an old, Linden ‘Nav Can’ buoy. Kaz Destiny hit the wreck in one of the semifinals races two weeks ago, and yesterday Takabou Destiny did the same thing.

Takabou went on to win that race series against Lynn, so the single event made no difference in the outcome. Nonetheless, it looked like the racing fleet was uncertain how to deal with such an obstruction. Here is the public transcript immediately following the race (with spelling corrected and extraneous comments redacted):

[9:25:08]  takabou Destiny: Excuse me. I didn’t call, but can I call ‘ROOM‘ at last mark?
[9:26:08]  Jane Fossett: YES; that is an OBSTRUCTION.
[9:26:21]  Lynn Parkin: Inside boat gets room when overlapped at mark, no?
[9:26:26]  takabou Destiny: Under water object
[9:26:37]  Jane Fossett: The Wreck is an OBSTRUCTION,
[9:26:43]  don Berithos: She really had no room to give.
[9:26:46]  Jane Fossett: but you need to call it.
[9:26:47]  Lynn Parkin: How can I give room…when there is room for only one boat?
[9:26:51]  takabou Destiny: ok
[9:27:10]  Jane Fossett: judges will decide if the call is correct.
[9:27:15]  takabou Destiny: you win Lynn : )
[9:27:22]  don Berithos: I saw it there was no room.

The race was Saturday, and Tak won the three-race series despite hitting the wreck. However, the issue he raised is important, and this is my understanding:

Rule 19 – Room to Pass an Obstruction

19.1. When Rule 19 Applies.
Rule 19 applies between boats at an obstruction except when it is also a mark the boats are required to leave on the same side. However, at a continuing obstruction, rule 19 always applies and rule 18 does not.

19.2. Giving Room at an Obstruction
(a) A right-of-way boat may choose to pass an obstruction on either side.

(b) When boats are overlapped, the outside boat shall give the inside boat room between her and the obstruction, unless she has been unable to do so from the time the overlap began.
(c) While boats are passing a continuing obstruction, if a boat that was clear astern and required to keep clear becomes overlapped between the other boat and the obstruction and, at the moment the overlap begins, there is not room for her to pass between them, she is not entitled to room under rule 19.2(b). While the boats remain overlapped, she shall keep clear and rules 10 and 11 do not apply.

The Rules of Racing are primarily about safety; the goal is to keep all the sailors alive to race another day. If you are traveling at breakneck speed and overlapped with another boat, when an opposing skipper calls ROOM! to avoid a collision with an obstruction, her need should supersede most other agendas on your dance card.

In this case Takabou did not protest; he decided to go around the obstruction, and Lynn had no fault. However, with the boats solidly overlapped, Tak was potentially in his rights to call ROOM! under Rule 19.2(b) to avoid hitting the wreck. In that case, Lynn had free water and could easily turn to port… even if that meant she missed the mark.

Vodpod videos no longer available.
Dave Perry – Rule 19 – RRS 2009-2012, posted with vodpod

Fracas Foments as Hawk and Armano Finish

The picture of Hawk and Armano passing the final mark in Rachel show that Hawk ended wide and leeward of Armano as they began the final sprint to the Finish line.

Both boats were on a near dead run, but Hawk realized Armano was better positioned to win that final short sprint to the line. Hawk’s only chance was to use his leeward ROW in a blocking maneuver to trip-up Armano. You can see a wonderful replay of what happened in Surfwidow’s video above, beginning around 06:30.

As shown in the still images below, Hawk turned to windward and shouted “UP!!” to get Armano to change course. Armano begins the turn, but Hawk needs to push him wide of the course. He aggressively turns into Armano… and hits him! Surf’s video shows what happened next; it confirms the umpire’s report and what the sailors themselves reported. After the boats recovered from the hit, Armano tried to turn back towards the line, but Hawk called “UP!” again… and hit him again! 🙂 How’s that for Relentlessness!

Click to enlarge.

As shown in the sequence below, Armano made it to the far end of the raceline with the help of Hawk’s push 🙂 ; he then broke clear, gybed to Starboard, and limped toward the Finish. Hawk was still on the hunt however, and tried to shove Armano out-of-bounds. Armano at that point was on Starboard tack, however; it was his turn to shout “room” and protest.

Click to enlarge.

The judges considered the statements of the sailors, as well as their own observations; they key points were nicely illustrated and confirmed by Surf’s video. The judges agreed Hawk had ROW and could call “UP” to turn Armano off course. However, the judges all agreed that Armano’s counter-protest was correct; Armano required time to turn, and was in process of turning when Hawk hit him.

Rules calls are often pretty subjective, and facts can get blurred in the heat of the moment; luckily, in this case Hawk came back and did an instant replay, calling UP! and slamming into Armano a second time 🙂

The judges’ decision was unanimous. The sailing was so great, so exciting and audacious, it seemed very wrong to call either sailor DSQ for their efforts. No one wanted to squelch the obvious skill, intelligence, and guts shown by such incredible skippers.  Instead, without specifically ruling on each of the six potential protests, the Judges ruled the Race Results were valid as they stood.

Armano beat Hawk…
BY ONE SECOND!!!!

Race Results:
1: Armano Xaris   IDax56 — 00:11:10
2: LDeWell Hawker   ID12 — 00:11:11
Lap Times:
Armano Xaris   IDax56 — Start: 00:00:03  —  Last lap: 00:11:07
LDeWell Hawker   ID12 — Start: 00:00:02  —  Last lap: 00:11:09

Click to enlarge.

Rule 19 – Room to Pass an Obstruction

19.1. When Rule 19 Applies

Rule 19 applies between boats at an obstruction except when it is also a mark the boats are required to leave on the same side. However, at a continuing obstruction, rule 19 always applies and rule 18 does not.

19.2. Giving Room at an Obstruction

(a) A right-of-way boat may choose to pass an obstruction on either side.

(b) When boats are overlapped, the outside boat shall give the inside boat room between her and the obstruction, unless she has been unable to do so from the time the overlap began.

(c) While boats are passing a continuing obstruction, if a boat that was clear astern and required to keep clear becomes overlapped between the other boat and the obstruction and, at the moment the overlap begins, there is not room for her to pass between them, she is not entitled to room under rule 19.2(b). While the boats remain overlapped, she shall keep clear and rules 10 and 11 do not apply.

Armano Xaris Wins SL-Vuitton Final Top-Spot

Breaking News

After two and a half months and nearly two hundred match races sponsored by many yacht clubs and  marine-themed estates across the grid, today it came down to four championship contenders and a final five-hour match sequence.

Armano, Hawk, Lynn, and Takabou were all well-known household names to the large spectator crowd attending today’s event. The superstar sailors who met on the Fedallah raceline for the final shoot-out had repeatedly flashed incredible sailing skills and demonstrated their undeniable dedication in prior qualifying rounds… and in so many other sailing competitions.

These four are all Kazenojin, in my book.

Thankfully, today’s weather was reasonably cooperative, and all the contenders knew the courses, the potential “tough spots,” and any unique rules issue very well. It turned out to be as good a day of racing as anyone could reasonably hope for on the sometimes-treacherous waters of SL.

When the rounds of semifinals matches completed, only two of the four skippers remained standing: Armano Xaris and Takabou Destiny.

Don Berthios, the GGYC Commodore and SLVT Regatta Chair, recently made a decision to change the format for the final match event to a “Best Three of Five” race series. Many experienced Regatta planners (including myself) groaned at this decision, since it made what we knew would be a long event… even longer.

However, I now agree Don was right! the final competition between Armano and Takabou ended up tied at 2 wins each; their sailing skills were so evenly matched it should never have been decided by just three final races, since lag and grid issues may have invalidated that short result-set.

As it turned out, the five race format provided a fair test of the skills and ability of two truly incredible racers. In the end it came down to just one final race, and just eighteen seconds…

Armano took the top spot, but wow! Everyone in SLSailing came  away a winner.

I’ll have a lot more to tell you later!

SL-Vuitton Champions:

  • 1. Armano Xaris
  • 2. Takabou Destiny
  • 3. LDeWell Hawker
  • 4. Lynn Parkin

Same Boat, Same Shadow, New Graphic!

Two days ago I posted an article here about wind shadow for Trudeau One. ONE is the first serious race boat from Trudeau Yachts since the legendary  J-Class, and ONE’s shadow engine is a truly powerful, tactical weapon. I think any serious sail racer owes this feature considerable thought and attention.
(But I’ve been wrong before.) 🙂

As I mentioned in the last article, I wasn’t too happy with the graphic displays  I came up with for shadow effects, and was still working on it. Today I went back and repeated all the measurements, trying to come up with a simpler graphic that might illustrate the effects but still be useful for race skippers.

Here’s that second attempt below; this time I ran around measuring the shadow intensity leeward of the ‘wind-blocking boat,‘ trying to define the borders of the “WS>20%” blanket zone.

The blue coordinates below show the points where WS=.20 (in other words, a ‘20% windshadow effect’). That new data matches rather nicely with what I posted two days ago.

Here’s the Bottom Line: A boat in the ‘orange bubble zone’ on the below graph will fall into a substantial shadow effect with a serious drop in wind impulse power. At the edges of the Orange bubble the effect is 20%… but central to the bubble and closer to the windward vessel the shadow strength goes to 100%.

In my hands, in this boat there is no noticeable turbulence effects on the Windward side of the shadow vessel; it’s all about Downwind Shadow, and that influence projects a strong, realistically-sized blanket on leeward boats within several mast-height distances from the ONE root prim.

The graphic below also shows the two features I emphasized previously:

  • There is a relatively small but very definite bias for stronger shadow effects aft of the shadowing boat. A boat approaching the windward shadow-caster from behind will get hit sooner with a heavier hammer than one on an opposing tack that passes from the front.
  • Since the shadow script radiates from the root prim, the effective area is shaped like a funnel… or actually a cartoon chat bubble :-). In other words, the Shadow Zone is very narrow immediately next to the boat, but then expands out fairly quickly.
  • A lee boat that that passes very close to the shadowing vessel  [2-4 min horizontal separation) therefore may only see a shadow effect for 5-6m of linear distance while passing. The shadow will be maximal for that short spurt, but if a crew has enough forward momentum, they might well be able to glide through that segment and find clean air on the other side.
  • What’s that line from Winston Churchill? “If you’re going through hell… JUST KEEP GOING.

It’s worth commenting briefly on three more points:

  • Watch out for sim edges. As Alain pointed out yesterday, shadow doesn’t transmit well over sim boundaries. You might play those boundaries  to tactical advantage.
  • For two boats traveling  perfectly parallel on a beam reach, the shadow effect is 100% with boat separations of 2.0 m – 14 m (beyond that, the shadow effect decays progressively with distance; it is minimal around 50m separation).
    This means that a boat passing leeward with 14 m separation sees the same maximum shadow as a boat passing with a scant 2.0 m separation.
  • There is, however, no advantage to giving the Windward boat extra room; the shadow effect will be just as bad a boat length away. I’m bringing this up here to illustrate that ‘funnel shape’ I talked about before.
    With a small 2.0-4.0 m interboat separation, the shadow effect on the passing boat has a very short geographic range. In contrast, if you “stay a safe 12 m away from the windward boat,” the actual intensity of shadow is the same, but the linear effective range while passing is far, far greater.
    Passing a Trudeau ONE on a course set 2m leeward to the shadowing boat is an interesting tactical option in my opinion… a gutsy crew might be able to pull that one off and grab the lead.
  • However, if you trying that same leeward maneuver with a larger 14 m interboat separation, the ‘course distance” you’ll spend under strong shadow is far greater. In my opinion, passing parallel and leeward at 14 m isn’t ‘tactics…‘ it’s suicide. 🙂
  • Hey! You try it!

    And please tell me if the new graphic makes more sense to show effective shadowing than the last one I posted!

Shadow Boxing

Wind shadow is a powerful tactical weapon in sailboat racing. A skipper that successfully maneuvers between the wind and an opponent can effectively ‘blanket’ the downwind boat by stealing the air.

In real life, the magnitude and extent of the shadow a boat can cast depends on a number of variables, but a shadow’s effective range is usually three-to-five times the mast height.

How does this translate in SL Sailing? What’s the shadow magnitude and how wide is the blanket? It’s hard to get accurate, practically useful numbers for different boats, so this past week I’ve been playing around with the 1.12 upgrade for Trudeau ONE, collecting data on the wind shadow effect. (Huge thanks to Bunnie Mills and Chaos Mandelbrot for their help with this).

I thought some race-aholics might want to see the numbers!

The image above shows one easy way to collect shadow data. Two boats catch racewind (in this case 9.0 m/s from compass North, no variance). They drop sails and sit stationary in the water, with the windward boat on a beam reach heading. The leeward, ‘shadowed’ boat then moves to a series of stationary downwind coordinates to measure the intensity of the shadow and check the resulting effect on wind speed.

Since all the measurements are for ‘stationary’ positions, there is no lag effect and the findings are easy to reproduce.

The HUDs for several Trudeau boats give numerical readouts for shadow intensity; they indicate the fractional WS effect from 0.00 to 1.00. On the charts posted here I’ll express those numbers as a percentage of the max Shadow effect. With the windsetter blowing at 9.0 m/s, the chart above shows that the boat’s wind is inversely related to the percentage of WS effect. With WS= 100%, the wind  powering the boat is cut from 9.0 to 3.6 m/s, a 71% shadow-reduction.

That’s pretty consistent with other boats in the Trudeau fleet, going all the way back to when wind shadow was introduced to the Trudeau line in the TWENTY.

The curve above shows the drop-off of shadow intensity with increasing distance between two boats. To get these measurements, the boats were overlapped and the shadowed boat was progressively moved further leeward. The image above shows an example of the setup, with a separation distance of 50 meters.

The resulting curve shows that T-ONE throws a maximum intensity blanket that extends over one boat length leeward (14m). At 20m separation, the shadow effect drops to 75%; it then continues to decline with increasing distance but is still present at 50m.

These findings seem well-consistent with the real-life predictions for the boat, and are confirmed by the wind speed changes on the shadowed boat with increasing lee distance, as shown above.

I admit I haven’t looked at Trudeau Shadow very closely for many months… but the numbers I got this past week are pretty encouraging. Two years ago a very large fleet of beta testers played ‘sailboat sandbox‘ with Trudeau TWENTY, trying to come up with just-right shadow parameters. When the boat launched, I was convinced a windward skipper could use shadow to keep any lee challenger at bay… but only if they were experts at it and knew what they were doing.

Conversely, I was pretty sure an excellent leeward skipper had all the tools needed to trash the best laid plans of some overconfident, windward Shadow-Maven. 🙂

(HEY, just like REAL-LIFE!)

Trudeau ONE  fits right in that tradition, but with far more intelligence and subtlety. 🙂

Passing Data

OKOKOK… I know the above numbers-and-graphs stuff is boring, and for most sailors it’s all probably pretty obvious, anyway. But…

I’ve been trying to think of a way to represent the racing-important data in a way that would provide the real numbers but might also make quick sense to a skipper who wants to know the best way to beat a shadowing boat. I’m trying to figure out a way to say “Please don’t believe me, look at the real numbers, come up with your own tactics.

I’m still working on it, but here’s what I think.

The chart below is a 2D-grid. It shows red lines that indicate shadow measurements for a boat trying to pass a shadowing boat on a course set to leeward separations of 2, 7, 10, 20, 30, 40 and 50 meters. This is what happens in real life; you want to pass that boat; you need to know when the shadow kicks in, and how to beat it.

(Conversely, if you are the windward shadow-commander, you need to know the best way to put an iron lock on that upstart pretender trying to sneak up on you….)

The 'bow' of the red boat rectangle is facing Left above.

Take a look at the 20m line above. It gives you the percent WS effect as you approach on a parallel course 20m leeward of the shadow boat.

When you are 25m away from ‘overlap’  (roughly a 50° angle from the shadowing boat), an 8% wind shadow kicks in. Don’t kid yourself, 8% is a lot, and in the next second when you hit 45° on that 20m course, it’s going to double to 15%. You can read the numbers above, and see the distance you’re going to need to cover to get past that Windward hammer. You got the momentum for that big jump? 🙂

I’ve looked at Trudeau wind shadow for two years, but I learned a few new things this week by collecting the numbers above. Maybe I’m slow, but perchance you missed them too. 🙂 Here are the two big items that might help win a race:

  • I’m not sure why, but it looks very consistent and very clear that Trudeau Shadow angles backwards given the setup I described above. A boat traveling a parallel, 20m leeward course will see 15% shadow when they are 20m aft of ‘mast abeam.’ When they are 20m ahead, they only get 3% shadow. Factor that in, someplace… 🙂
  • Trudeau shadow radiates downwind as a cone, and it’s extremely narrow right next to the windward boat. With a minimal, 2m boat separation the shadow only affects the passing boat for 5 meters (it’s pretty much a 100% sledgehammer there, though)! A lee boat with mega-guts and deep-seated momentum should be able to cross its fingers, close its eyes and blast past by snuggling very close to the shadow-boat while holding its breath. (GRIN!! Good Luck on That, You Try it First! Let Me Know!)

OMG; that’s enough numbers for today! Go sailing!

SLVT Finals August 28

Destiny – Hawker – Parkin – Xaris

Saturday Shootout in Dire Strait



SL-Vuitton Trophy Finals

Golden Gate Yacht Club

August 28 2010
9:00am SLT

Fedallah Raceline, Dire Strait

______________

 

Three is the Trick: ACA33 3.0 Launches

The Americas Cup competition holds a unique spot in the history of sailing. It embodies a century and a half of tradition, uncompromising excellence, and personal dedication. Although the 20th century was pockmarked by global disater and warfare, I think many would agree the AC challenge stood as a distant beacon, an iconic bright star that held the common hopes of so many sailors trying to express their common beliefs in this fragile, watery world.

I admit it, I inevitably end up thinking of the Coppola movie version of the Cup:

\

I know, I know the movie got the sailing all wrong and it should make any real sailor cringe, but wow, Coppola got the spirit right.

ACA in Second Life

Not surprisingly, that tradition found its way into Second Life.

Please, give Florencia007 Csak a standing ovation! In Spring 2007, Florencia and 9TH.com helped organize and sponsor the ACA-SL America’s Cup Regatta in Second Life. It was a truly wonderful event that became a defining moment for all SL Sailing, clearly demonstrating the metaverse potential — and opportunity —  for a RL-SL sailing emulation.

Surfwidow Beaumont’s video captured the true essence and the excitement of that rather glorious event:

The ACA32 Racer was the competition boat originally designed for the Americas Cup Anywhere- SL event. It was a combined, creative effort that involved several builders and scripters. Jacqueline Trudeau provided the ACA32’s sail engine, and the boat’s visible hull and hardware were part of a wearable attachment (remember, this was way before sculpties!). The boat was majestic and impressive, and immediately won the hearts of a generation of SL sailors.

However, it’s fair to say that as boat design evolved in Second Life, the ACA Racer failed to keep pace. This was a tad ironic, since in Real Life the AC boats are often considered on the cutting edge of nautical design, continuously pushing the limits of technology and construction.

Two years ago I wrote a short article humorously complaining about this, asking for an ACA fix and whining “ I want a new gun.” Since Christmas was approaching, I included a letter to Santa Claus, asking for a new ACA, something to push the envelope. I got pretty specific, too: I wanted a boat with Apparent Wind, Realistic Shadowing, and omg… a Spinnaker!

Well, it turned out that upgrading the ACA was no easy matter. Over time, several scripters had tinkered with it, and any major upgrade was going to take somebody smart who had a clear vision, a large commitment and a fresh approach.

Caf Binder stepped up to the plate a few months ago and took on that rather daunt-laden challenge. This past Saturday his new ACA33 3.0 officially hit the water, and sailors finally got to see what Caf’s been up to late at night. 🙂

The new 3.0 has all the things I begged Santa for, and much, much more!

ACA33 Quick Look

Quirky Torok has a pretty great introductory video that can give you a rundown of the new features on the boat and also get you going sailing if you’ve never skippered an ACA before:

I’ll try to focus my initial, brief discussion here on some background and issues not covered by Q; I’ll have a lot more to say later!

Sail engine

Most sailing vessels in SL are “derivative.” In other words, they are based on a prior sailing algorithm, such as Kanker Greenacre’s public Tako scripts.

I mentioned above that the original ACA32 sail engine was scripted by Trudeau, and I admit with a degree of chagrin that I’ve always thought of the ACA32 (and early versions of ACA33) as sort of a ‘buggy prototype’ for the Trudeau Larinda that launched several months later.

Well, Caf Binder didn’t go that route; he went back to square one and redid everything in the ACA, incorporating some of the best ideas from Trudeau, Mothgirl’s Fizz engine, and Caf’s own Jangars.

The result is a new sail engine; if you ask Caf what the 3.0 is based on, he grins and quickly answers “The real ACC v 5.0.” Caf’s vision is to build a boat that uncompromisingly reflects the Real Life sailing properties of recent Americas Cup monohulls. Quirky’s video above mentions a few simple examples of this penchant for reality, including such items as when you raise/ lower the spinnaker, there’s a ten second delay, and the jib can’t trim tighter than 10°.

When you sail the 3.0, you’ll find how serious Caf is about this approach. After you click the “Anchor” button on the HUD, for instance, it takes a full 60 seconds for the boat to come to a complete stop. When I asked about Caf about this, he replied “How long does it take the Real boat to stop?”  Actually, it was hard to disagree with that logic! 🙂

performance

I have lots to say about this boat, and a lot I still haven’t yet figured out; today I’d just like to give you some basic performance plots I’m working on, and say some nice things about Neron’s spinnaker!

Since Caf’s design target was to realistically model an IACC Class boat, let’s begin by talking about those real performance characteristics. The plot below shows data for upwind Boat Speed (BS) as a function of True Wind Speed (RWS).  The numbers are for the Swedish Victory Challenge Team’s IACC racer “Orn”  and adapted from figures published in Joel Nielsen’s Master’s Thesis.

If you look closely at the above best-fit curve, you can see that under low wind conditions, Orn’s boat speed can exceed RWS; with a 6 kt breeze, the boat will do 9 kts!

Wetted contact area produces friction and turbulence

However, as wind intensity picks up, multiple factors resisting the boat’s forward motion become more prominent, and the boat is less responsive. In a 20kn breeze, Orn does around 10.4kn. My whole point here is just  to say that a RL sailing vessel has a nonlinear response to increasing wind speed.

Caf Binder’s  evidently modeled that into the new ACA33 3.0. I don’t know where Caf’s getting his numbers, but I’m impressed the boat I’m sailing comes close to the actual RL performance values for IACC.

Take a look at the chart above. At low wind speeds the 3.0 matches or exceeds RWS. However, around RWS =10kn the boat becomes less responsive and at RWS= 20kn the boat speed is approximately half RWS. A pretty close match to the RL numbers!

Here’s my initial ‘polar’ for the ACA33 3.0 with RWS= 9.7kn, flying just the Main and Jib (no Spin). The 3.0 uses a “full-dose” Apparent Wind calculation, so there’s a big shift in Apparent Wind heading towards the bow as the boat accelerates. In a 9.7kn breeze, an Apparent Wind Angle of 60° actually corresponds to a Real Angle of nearly 120° !

The HUD in 3.0 has a nice feature that alternates the AWA and RWA displays, so it’s actually pretty easy to keep track of this stuff.

I mentioned the above numbers correspond fairly closely to the RL IACC racer. However, it’s also fun to note that 3.0’s performance matches the the published polars for the Virtual Skipper VSK5 ACC boat.

If you click on the image to the right, you’ll get an enlarged view that shows a response curve for RWS=10kn that’s pretty similar to the above results for 3.0.

I’s nice to see how closely all the versions match up!

Spinnaker

A boat without a spinnaker is like a day without sunshine. 🙂

ACA33 3.0 has a megaprim sculptie Spinnaker and hull that are both crafted by Neron Blanco.  Since there can be “mismatches” between the visible sculptie and the underlying collision mesh that actually bumps into obstructions, one of the first things I usually do with a new boat is to go around hitting stuff in order to check out the sculptie. 🙂

Neron’s spinnaker and hull pass that silly test very nicely! As you can see below, the front and sides of the ‘chute’ bump into a test object with nearly perfect contact. There’s a small  ‘gap’ near the top of the spinnaker when it is the first touch point, but that’s really irrelevant for sailing or racing, even under truly extreme circumstances.

Since we’re talking about bumps and spinnakers, let me also comment that the spinnaker pole is low enough to hit buoys… or boats… or sailors, so be careful! 🙂

It’s actually not a trivial issue, since the spinnaker on 3.0 automatically rotates in response to the wind heading. (I’ll tell you more about that next time).

Today I just want to add the plots for the spinnaker and jib to emphasize the differences, and to give you some data so you can decide when you want to switch head sails.

The curves below show Boat Speed v Wind Angle for Spinnaker and Jib used alone, with the Main down. The spinnaker provides a big boost for AWA headings over 60°; it’s easily twice as effective as the Jib from AWA= 70° – 160°.

Having said that, please be very careful using the spinnaker below 70° Apparent. When the parachute collapses, there’s a sudden loss of power and the boat careens as the bow drags leeward.  Be afraid!! 🙂

I have a lot more to tell you about this boat… and I’m still figuring a lot of it out. I’ll fill you in next time!

But for today, let me just say

Thank you Santa.
And Thank you 9TH, Caf, Quirky, Neron and Flor.

I Got a New GUN !!

ACA 3.0 Launch Party on August 21

The long-awaited ACA33 v3.0 will hit the water this Saturday!! Don’t miss the launch celebration and party!

Saturday August 21 2010
12:00 noon SLT

Hollywood Bowl