Category Archives: RM 12

Cruisin’ #3: The Rene Marine 12, Tofinou

RM12

This month I’m reviewing three popular, contemporary cruising boats in Second Life. I’ve already posted about Analyse Dean‘s Bandit 50 and Kain Xenobuilder‘s Café del Mar 75. Both are large and fast cruisers that use the new BWind 2.5 wind engine.cruiser trio Bandit and Café also come with many on-board accommodations, including rather extensive cabin space and over two dozen animations. The boats compare favorably with my previous, ultimate 2012 favorite cruiser: Motor Loon‘s remarkable Loonetta 31.

Today I want to talk about the third cruiser on my personal short-list; it’s Rene Underby‘s RM12 Tofinou, and it’s available at the Rene Marine boatyard in Thalipolli.  The boat is modeled after the French Tofinou 12, a 40ft  Joubert/Nivelt  sloop design.  SteveLL Resident  (aka Justin) likes this boat a great deal, and his enthusiasm got me interested (thank you SteveLL !!!).

Having said that, let me also add that the RM12 is the first Rene Marine boat I’ve put under the Metaverse microscope, so please bear with me; I might not get everything right. Nonetheless, I’ve spent five months testing this boat, and think I have a reasonably good feel for it. 🙂 if I get something wrong, hopefully SteveLL will correct me here!! With those provisos on the record, let’s talk about the boat.  🙂

The RM12 is substantially smaller than the cruisers I’ve recently reviewed; RM12 might be best classified as a daysailor rather than a Coastal Cruiser.

Compared to Bandit and Cafe, RM12 has fewer animations and less “jazz” throughout, but actually that’s quite intentional. The contrast between the different design styles is present in real life, and nicely summarized by Peter Nielsen in Sail

“The aesthetic differences between American and European boats are nowhere more pronounced than in the daysailer niche. The average modern U.S. daysailer has a refined, gentlemanly air; it’s a boat your granddad would have been proud to own. A typical sporty Euro-daysailer, on the other hand, is a dashing rogue of a boat; Grandma might send it coy glances, but Granddad would eye it with suspicion.

Tofin12“If there is a boat that straddles this divide with hardly a wince, it is the Tofinou range from France. Tofinou was building pretty little daysailers long before the idea caught on in the United States. Its hulls have the sweetest of lines, and on its bigger boats, the 8, the 9.5 and the 12, gleaming varnished teak and mahogany woodwork is integrated seamlessly with expanses of black carbon fiber and subtly contoured fiberglass. …

“The 40-foot Tofinou 12 is… moderate of beam, lean and low-slung, and drawing almost 8 feet—which would be a drawback in many areas of the U.S. East Coast, but makes for an impressively stiff and precise ride to weather. Hull and bulkheads are lightweight fiberglass/foam composites, and the bare minimum of interior furniture and systems—along with a carbon fiber spar—help keep weight down to a svelte 10,500 pounds—about 40 percent less than a typical 40-foot production boat. …”

And here’s a clip of the Tofinou 12 in action:

The Rene Marine 12 “Tofinou”

Rene Marine.  Rene Underby and Jethro2112 Sands are Rene Marine. They have worked together for several years now, building boats with clean scripts and thoughtful designs; you can see the whole ReneMarine fleet over at their main location in Thalipolli. You can also hear about their philosophy of yacht building by watching the Treet.tv documentary on SL Sailing; René and Jethro are prominently featured.

René builds sailing vessels that genuinely emulate classic boat designs, and the RM12 is just one vessel in her long line of authentic sail craft that you can see at her marina.

Her RM12 is a skillful mesh build. The boat weighs in at a trim 57 prim with a Land Impact of 37. For comparison:

Bandit 50                 41 prim     32 Land Impact
Rene Marine 12     57 prim     37 Land Impact
Cafe del Mar           67 prim     48 Land Impact
Loonetta 31            32 prim    32 Land Impact

Sailors will find the RM12 mesh design to be clean, simple, and true to the real boat, and it has multiple features that should make any seasoned skipper smile.

RM12 cockpit 017

The Hull and Topside

The cockpit is nicely arranged with an ample number of port and starboard self-tailing winches within reach of the dual helm. topsideThe detailing and finish is quite thoughtfully executed, and full of fun; there’s even a winch handle already loaded, ready to crank!

The skipper and crew have a choice of multiple sit options that can be accessed through a simple hierarchical menu system that automatically pops up. A few of the poses are shown in the image sequence to the right. (click to enlarge)

Is your avatar is an odd size? Don’t worry! The sit positions are easily adjustable. 🙂

Although this boat is a solid cruiser that will carry several crew, remember when you go below that RM12 is designed for performance, and matches the real life Tofinou 12. Don’t be disappointed because there’s no shower or Cuisinart.  This boat is built to sail, and any extra features are installed to help a skipper take true command of the boat’s multiple sailing options. The RM12 is a cruiser intended for sailors. 🙂

below

Even sailors need to drop anchor occasionally, so Rene Underby has also included a set of animations for couples to use during those off-hours. 🙂

RM12 sleep cubbies

RM12 Sails.  The RM12 is fitted out with a fractional sloop rig with a Genoa and mainsail, but there’s no spinnaker.

If you’re worried about overhead clearance, please note that the fore and aft stays are physical, and so is the keel. This adds considerably to the boat’s realism, but watch out for shallow water and low bridges!  🙂

RM12 sailsThe RM12 comes with a headstay furler for the Genny, and an in-mast furler for the Main. Both have nice animations that deploy the sails when you say “Raise.”

A skipper can raise, lower, trim or reef each sail independently. That’s a truly useful feature that is also present on Trudeau Classic boats, although it’s missing on most others.

Having said that, let me add that I’m not aware of any SL boat that optimizes differences between the jib and main trim depending on sailing conditions. My guess is that’s on the laundry list for the “next step” in improvements to sailing algorithms.

While we wait, let me add that the RM12 sails are quite nicely constructed and scripted. When they fall out of tune they let you know with a realistic visible and audible “flap.” 

To adjust the sheets and bring them back into optimal position, a skipper uses the up/down arrow keys. That changes the sail angle in small  (three degree) increments until the settings are correct. I’m not aware of any chat-command control for the sheet settings on this boat.  It’s also notable that only the skipper can adjust the sails. There is option to share sail control with the crew, and crew location on board (hiking) has no impact on boat heel or boat speed.

RM12 boom angleIn my last cruising article, I commented that there was an apparent mismatch in some boats between the sheet angle setting and the visible angle of the boom and mainsail. That’s not a problem with the RM 12, however. The image to the right shows a vertex view of my RM 12 sailing a dead run with the sails full out. The maximum angle you can set for the boom on RM12 is 70° (it’s probably limited by the stays). That angle agrees quite nicely with what you can directly measure from your screen, as shown above.

One more thing about sails on the RM 12: Since the boat has dual furlers, Reefing the sails is a snap. You can let out any percentage of either the main or the Genoa with a simple chat command, and the power of the reefed sail adjusts accordingly.

RM12 reefing

The boat even has an adjustable traveler for the mainsheet, located aft of the helm station; I’ll talk more about that in the next section.

SteveLL RM12

Sailing the RM12

RM scripts. The RM12 is powered by Rene Underby’s wind engine. If I recall correctly, René originally adapted her algorithm from Kanker Greenacre’s Tako 2.x. However, over time Rene’s scripts have evolved to meet the needs and expectations of a whole generation of new sail designs and skippers in SL. At the present time, my guess is that sailors would be hard-pressed to find any Tako genes still actively expressed in the René Marine family of boats. 🙂

Wind for Two. If you like to use the wind that’s broadcast by raceline WWC windsetters in Second Life, that’s easy for RM12. All you need to do is “ID” your boat so it’s recognized by the raceline (the chat command is “ID 0000” , where “0000” is any number combination). Once you do that, the boat will search for the WWC’s broadcast.

The boat uses the WWC Cruise Wind settings (not Race Wind), and it makes use of the Wave and Current WWC features as well.

However, if you prefer to sail on your own the boat also has built-in boat wind. Just type “wind spd xx” to set the wind speed in knots, and type “wind dir xxx” to pick a wind angle. You’re not restricted to the small number of values that come with BWind boats.

RM12 HUD. The RM12 comes with a vertical stack of five multi-purpose data screens that give you all the sailing information you could ever hope for.

rm12 hud

The panel on the right below shows this info-display stack coupled with a quick guide that explains their function.

The first two instruments are analog indicators.The top one shows Real Wind Angle, but you can switch it to Apparent Wind Angle with the push of a button; and if you want numerical values, that’s shown as an inset on the gauge.

RM12_HUDThis top display is comparable to the great  info HUD that comes with   WildWind‘s  Wildcat 45 and Open 60.

The second instrument in the RM 12 stack is unique; it shows rudder angle. As you can imagine, the rudder angle determines how acutely the boat will carve a turn. I’ll talk more about this below.

The third instrument has a screen with four different command functions that can each be activated by clicking buttons next to the display. Two are pretty straightforward: “Raise” raises both sails, and “Motor” powers up the diesel.

Two other button commands are less common. One turns on ‘Autotrim,’ a utility that optimally adjusts the sails to match the AWA. The other is an ‘Autopilot‘ that locks the boat to a particular heading. If you are new sailor, these options can make sailing the RM 12 extremely easy; you just point-and-shoot. 🙂 If you’re an Old Salt in SL, you’ll also find these tools pretty great. They let you put the boat through test trials with heading and sails fixed, while you tinker with all the other options that enhance performance. 🙂

The last three HUD instruments are digital displays; a skipper can flip the info shown on the HUD screen to display any of 10 different panels. I know many sailors may feel differently, but I like the option to see a lot of numbers while underway, and the RM HUD fills that bill nicely. 🙂

Rudder Reality. The RM12 has a distinctive steering system. In nearly every other sailboat in Second Life, a skipper steers by pressing an Arrow key, and the boat actively turns until the key is released. The effect is a bit more like a ‘bow-thruster’ than a rudder. 

The RM12 is more realistic. Pressing an arrow key will cause a rudder deflection that you can monitor on the HUD gauge. The boat will turn toward the side of the rudder until the skipper centers the wheel again. However, if there’s no breeze or the boat is nose to windward and not moving (“in Irons”),  the RM12 will do what any self-respecting sailboat does in real life. It just sits there, waiting for the breeze to shift. 🙂

Polar Explorer

Once you get the hang of the steering, you’ll find that the RM12 also has rather realistic polar performance under sail.

RM12 15kt single sail polarsThe chart to the right shows a plot in blue of Boat Speed vs Real Wind Angle for the RM12 using a RWS of 15 kts. The boat is fastest on a beam reach, and it maxes out with a top speed that’s roughly 70% of RWS.

That corresponds to a Hotlaps Handicap of 0.69, a number that’s in line with the majority of midsized cruisers in Second Life.

Since each sail is independent on the RM 12, I’ve also plotted the boat speed for the Genoa (green) and the main (purple) alone. As you can see from the above chart, the boat gets most of its thrust from the main at all points of sail.

The RM12 doesn’t have a Spin and you can’t wing the main; it makes sense that the performance declines downwind with RWA>120.

RM12 8-15-25 polarThe next chart on the right shows RM12 performance with both sails flying under three different wind speeds: 8 kn, 15 kn, and 25 kn.

On a beam reach in light air (8 kn), the boat can do 75% RWS. That performance efficiency decreases a bit to 72% RWS with the wind of 15 kn, and it falls much more to 62% RWS in a strong blow of 25 kn. As shown below, at those high wind speeds the boat heels far to lee and it is hard to hold it on course, even with the Autopilot engaged.

RM12 25kn

I’d recommend a windspeed around 15 kn for routine sailing. If you’re hit by a sudden squall with big gusts, you might think about reefing or dropping the Genoa. 🙂

Mainsheet Traveler.

This boat has one other trick in its sail adjustment toolkit: it comes with a Traveler for the mainsheet. A traveler has an adjustable car that determines where the sheet connects to the boat; it helps set the sail shape by holding the boom down.

The pictures below show the traveler in action (pink arrows) on RM12. In the left frame, the traveler is located far windward. That makes the sheet angle with the boom suboptimal, since the sheet can’t pull down to hold the sail flat. However, in the right frame the traveler is all the way lee. In that location the sheet is much better able to control sail shape. If you look at the speed gauge (blue arrows), you can see there’s a modest increase in boat speed as the traveler goes into action.

Traveler

A Good Turn

RM12 takes a turn

Five months ago I wrote about sailboat turns in SL. As I said back then, I think a boat’s ability to make a realistic turn is an important part of any authentic sailing emulation. The RM12 was the first boat in SL where I could take a serious look at this issue, since it couples realistic helm control with a flood of numerical data any skipper can monitor while making a turn.
turn radius - manyI won’t repeat all the discussion about turn-testing here; you can go read it someday when your boat’s in drydock. 🙂

I just wanted to emphasize that the RM12 is the boat I used to help set the standard for all the other sailboat turn-tests. It’s a tribute to René Marine that most boats I’ve looked at have independent turning parameters that fall within the same test range defined by RM12.

Summary

The  Rene Marine 12 is René Underby’s virtual re-creation of the French Tofinou 12 daysailor; it’s a very nicely done emulation that should appeal to many SL cruisers that want a midsized boat with realistic sailing features.

The RM12 mesh build is clean and accurate, with an economical Land Impact of 37. Once aboard, a solo skipper controls all the sailing functions when underway, but the owner can also delegate the skipper role to one other sailor through chat commands. 🙂

In addition to the skipper, RM12 can carry three crew, and there’s a wealth of animations topside and below to keep everyone entertained.

The RM12 has a Mainsail and a Genoa that are powered by the Rene Marine sail engine; the sails can be independently controlled by key click or chat command. To help guide the skipper, the RM12 comes equipped with a highly detailed info HUD. It has five vertically-stacked gauges that continuously report a huge amount of sailing information. 🙂

The performance polar for this boat is realistic, and falls in the range of several other cruisers in Second Life. Consistent with the polar results, RM 12 rates a respectable (and credible) Hotlaps Handicap of 0.69.

The boat comes with a few very interesting sail adjustment tools that enhance performance. They include an active roller reefing system for the main and Genoa, and a main sheet traveler to adjust sail shape.

The combination of realistic performance, detailed numerical sail data, and multiple sail adjustment options make this boat a good choice for skippers looking for an SL daysailer that authentically reflects RL.

If you’re in the market for a cruiser, you should also know the RM12 is missing a few features that are standard equipment on several other boats. Most notably:

— RM12 has neither a Crew-HUD nor hiking scripts. The RM12 skipper is in charge, and the crew is just along for the ride. (The same thing is true for most other contemporary cruiser emulations.)
— The boat lacks a spinnaker and there is no ‘wing’ effect, so the boat may seem slow on downwind points of sail. (Nonetheless, the Hotlaps Handicap is a respectable 0.69.)
— RM12 does not have wind shadow, limiting its potential as a racer. (However this boat is primarily a cruiser. The lack of wind shadow could actually be a lag-reducing advantage.)

I’ve been sailing the RM12 off-and-on for five months, and I now understand SteveLL‘s enthusiasm over this boat. I particularly like the boat’s ease of sail with autopilot and autotrim functions, and the detailed information provided by the info-HUD screens.

Go stop by at Rene Marine, and take the RM12 for your own test drive!

Rene Marineharpoon

Hotlaps Update, September 2013

Hotlaps Handicaps September 17 2013

Hotlaps 2013 is a sailing format that helps skippers practice skills while doing fun, solo laps that are posted online. The Hotlaps database allows skippers to compare their lap time results with others; they can also contrast the relative performance of different boats that sail under the same ‘trial lap’ conditions.

There are six different Hotlaps raceline locations, and each has its own Hotlaps course: PLUMGUTBREADNUTKNAPTRACKICONLINKOUSSULU, and HEPURN. Sailing a Hotlap takes only ten minutes, and you can do it any time you want, in any boat.

hotlapsposters Just go to one of the racelines and click on the ‘Hotlaps 2013′ poster above the green buoy; it will give you all the info you need.

When you finish sailing the lap you can post it online by clicking a poster that’s labeled “Enter your lap time here.” It’s just as easy as that. 🙂

Sailors have been doing Hotlaps and posting their results since early in 2007, but this year we started a new 2013 cycle in deference to the large number of great, boats that have recently hit the water in SL. Since we began it in January, Hotlaps sailors have logged 442 lap scores sailing 45 different boat classes! Let me give a shout-out to that great group of 68 skippers who did all those laps:

2525, ak Topsail, Andi Merryman, Armano Xaris, B112, B117, B12, BM12, Brett Kjeller, Bunnie, Chaos Mandelbrot, CharliePakk, charliepakk, Dekka, Destiny Wescott, don Berthios, Emelia Azemus, Fearless Freenote, Glorfindel Arrow, gnupf gufler, Hannelore Ballinger, HansMarx, Hay Ah, IDBSDF61, JFos, Joy Acker, Justin Blade, Kain Xenobuilder, Kentrock Mesmer, Kris Hollysharp, Lance Corrimal, laured Cabassoun, Lesbo Charisma, Little Vixen, LucyInTheSky Afarensis, Maiko Taurog, michiya Yoshikawa, Nikif, notohama, nozomimi karu, Ome Audeburgh, pascal kira, Patrice Cournoyer, Pazzo Pestana, Peacy Cortes, Pensive Mission, poko Zepp, Popow Horbaczewski, Porter Tracy, Qyv Inshan, Rebbie Resident, Rim Telling, Ronin Zane, S11D, sailman, Samlara Vintner, SkyBlue Earthboy, Slanty, SteveLL resident, Takabou Destiny, Trapez Breen, VictorCR, Wolfhard Resident, Wrye Diabolito, Xi Larnia, xpaulx pain, yala74, Yuukie Onmura. ~~ WOOTS! ~~

2013 Hotlaps

All that hotlaps data goes into a public spreadsheet that contains multiple, linked pages that sort the results by race line and boat class, color-coded by skipper. Here’s an example, showing the submitted lap data for Plum Gut from January through September 16:

Sept 18 2013 Plum Gut Laps

click to enlarge

You can click the above image to get a larger view, but you can also just go to the live spreadsheet page any time to see the list of entered lap times.

2013 Handicaps

The pool of standardized lap data makes it possible to compare performance of different sailboats and calculate a “Handicap Factor” for each popular boat class.  Hotlaps 2013 uses the Melges-24 as it’s arbitrary reference standard. The M-24 is the Hotlaps index boat, and by definition it has a Handicap of 1.00. (You can see that shown in red in the first data row below).  All other boats have handicap values expressed relative to that standard.  

Here’s the current summary list of Handicaps for all the tested boats at each of the race courses:

summary HH

Each row in the above matrix represents a different boat class and the columns contain the handicap values for those boats for the six race lines.  Slower boats (i.e., those with longer lap times than M-24) have Handicap Factors that are less than 1.00,  and faster boats have handicap factors greater than 1.00. 

handicapsFor example, several sailors tested the Mesh Shop Laser One on each of the six Hotlaps courses. The average handicap values were 0.75, 0.73, 0.74, 0.62, 0.69, and 0.79. That’s a pretty tight clustering of results, considering the varied sailors involved and the differences of each course.

The average handicap for all courses was 0.72, suggesting that the Mesh Shop Laser One is 28% slower than  the Melges-24 on any typical racecourse (The M-24’s handicap= 1.00).

 The figure to the right shows a current list of handicaps for tested boats, averaged over all six lines. The slowest boats in the bunch include the Shelly, the Fizz,  and the Galiko NY32 (which has a Fizz engine). All these boats produced handicaps of 0.50-0.60, evidence they are roughly half as fast as the Melges-24.

Of course, a slow boat is not a bad thing; it just reflects the builder’s design and vision. Several other boats had handicaps as slow as the ones named above in the 0.50-0.60 range, including the Leetle Cat II, the Patchogue II, the RM Pilot, and the ACA Tiny.

Cruiser handicaps.

tri

powered by Rotaru

However, that’s the slow end of the spectum; most cruise boats are faster than that. The cruisers in SL tended to generate handicaps that range from 0.60- 0.90. That means they are 10-40% slower than the Melges-24, at least when sailed with a 15 knot wind. Nearly all Trudeau boats fit in this 0.60-0.90 “cruiser”-group. It’s a realistic speed-spot for them, since most Trudeaus are classic designs of earlier, multipurpose vessels; they are not hotrods.

Many other popular boats also fit in that Cruiser 0.60-0.90 speed-niche. For example, Craig Kbata’s Teleri 20 scores 0.70, Manul Rotaru‘s Beach Trimaran rates a 0.82, and Rene Marine‘s RM-12 comes in at 0.69. Quest Marine has two boats in this speed range as well; the 2M (0.74) and the Scow  (0.85).

bandit 50Analyse Dean’s recent Bandit 50 is one of the quickest of this whole cruising group. It scored a 0.89, placing it just 10% behind the Melges 24 racer. Kain Xenobuilder also has a new cruiser, the Cafe del Mar 75, that uses the same BWind 2.5 engine as the Bandit 50. You might think Cafe’s sailing performance would be similar to Bandit’s, but you’d be wrong. 🙂 CDM75The Hotlaps data shows that the Café 75 is a much faster boat, earning a handicap of 1.12; that beats Bandit 50 by over 20% !!

The Cafe Del Mar is designed to emulate a beamy mid-size cruising boat, but it sails more like an ocean racer. It’s even  12% faster than the lean-and-mean, carbon and glass Melges 24! Wowzers!

I’ll tell you much more about Bandit 50, Cafe 75, and the RM 12 in a separate post soon. 🙂

Racer Handicaps

The third large group of handicaps primarily includes the large, ocean race boats in SL. They all tended to score in the 0.90-1.20 range. 

Q M-24 launchSince Hotlaps 2013 uses the Melges 24 as it’s benchmark standard to set the other handicaps, it’s no surprise that boats that score around 1.00 are also racers. For example, Kanker Greenacre’s Tako 3.3 scored a handicap of 1.03 in this series, almost identical to the M-24. 🙂 

The Quest IACC scored a 0.94, a bit behind the ACA33 Racer with 1.03. The Mesh Shop’s two ocean racers are right in that mix as well; The OD65 ranked 1.10, and the VO70 earned a 1.03.OD-65

It’s interesting to comment that the Mesh Shop VO70 has a handicap that’s identical to  the old  Wildwind VO70 (1.03). That makes a lot of sense since both builders were modeling the same boat, but it’s great to see the consistency. 🙂

Speaking of Wildwind boats, the present lap results clearly show that WildWind is continuing its reputation for building the fastest ocean racers in SL sailing. The Wildcat-45 catamaran scored a 1.12, the WW Open-60 rated 1.07, and the (still beta) WW AC-72 came in with a rather incredible 1.54. If WildWind decides to release it, the AC-72 could be the fastest sailboat ever launched in Second Life. More important, it would be a truly remarkable emulation of this year’s RL Americas Cup racer. 🙂

ac72 crew

Handicaps for History

There are still many boats to test and extra data laps to run to get accurate numbers across the whole fleet. By December 2013, we should easily exceed 500 new database laps, and that data will be added to a pool of many thousand laps on numerous courses dating back a full seven years.

That’s prolly a good time to sit back with a stiff drink and try to make some conclusions about what Hotlaps can tell us about the diversity of boats we all share and sail in Second Life. 🙂

harpoon

Turn Style

racers

It’s not the meat, it’s the motion…

When a sailboat makes a turn in Second Life (and real-life), three major things happen that a skipper needs to think about:

  1. the boat changes heading in response to the hydrodynamic forces generated by the rudder deflection;
  2. the boat travels along an arc until it establishes the new heading; and
  3. the boat speed usually drops due to a loss of momentum generated by the turn.

How well a boat accomplishes these points often has a big effect on the user’s sense of fun and realism. 

For a while now I’ve been trying to come up with a few simple ways to measure the turning properties of SL boats. That information might be useful when comparing different boat classes, and it may also help assess whether a given boat is a reasonable emulation of it’s real-life counterpart. Anyway, I admit I don’t have any big conclusions at this point, but I wanted to show a few charts here to see if any sailors have better ideas how to approach this issue.

cruisers

Half-turns

For large US merchant transport vessels, there are detailed performance standards published by the American Bureau of Shipping. The ABS is a good resource for maneuverability test requirements and discussions about the principles involved.

Probably the most common performance test is a Circle Test that monitors a boat’s ability to move through a full 360° turn. That works well for a powerboat, where the engine can maintain a constant thrust during the exercise. However, it doesn’t work very well for a sailboat, since the wind is constantly changing during the turn. A full 360° turn is pretty much never a “circle.” 🙂

It makes a lot more sense to test a sailboat using a 180° half-turn, as the boat flips into the wind from one beam reach to the other.

To do that in SL, I’ve been using FRAPS to generate screenshots each second while a boat does a standard 180° turn. I then plot the boat position data sequence on an X-Y matrix. Each data point also includes the instantaneous boat speed and heading.

Rene Marine 12

Let me give a quick shout out for the Rene Marine 12 (Tofinu). It’s a great boat for this kind of test. It’s built by Rene Underby, who has a long track record as an accomplished boatbuilder in Second Life. Her Rene Marine  boat yard is  filled with a full line of sail craft that emphasize both authentic styling and realistic performance.

racer RM12

The RM 12 is her newest creation. Apropos of this discussion, it’s designed to give a realistic response to rudder deflections, it has an option to hold the rudder at a constant angle, and it has a full info-HUD that displays the boat’s status.

Here’s a chart of boat position for the RM-12 as it does a half- turn.

RM12 turn rev

click to enlarge

It shows a plot of the X-Y map location at each second for an RM 12 with RWS= 15kn. The boat begins on a starboard tack with RWA 90°; it then turns through 180° to a new heading of RWA 270°.

The boat initially sails in a straight line with a constant boat speed of 8.6 (green arrow). The skipper then swings the wheel hard over to initiate the turn (indicated by “TILLER” above) and locks the rudder at maximum deflection until the turn is complete.

If you then follow the dots, you’ll see that within a few seconds the boat responds to the rudder deflection by turning into the wind and losing speed. At the point indicated by a red star (*),  the sails suddenly flip over, changing the boat to a port tack. That actually happens quite early, when the boat is only beginning the actual turn. It then takes approximately 15 more seconds to complete the 180° course change. By that time the boat speed has dropped  to 4.2, half the original. In addition, the arc of the turn moves the new heading approximately 30 m further windward (Red Arrow).

A boat’s initial speed and consequent momentum has a big impact on how wide a turn the boat will carve in the water. This is nicely shown in the figure below.

turn radius - RM12 two RWS

The green curve to the right shows the sequence of positions each second for a RM-12 as it goes through the half turn powered by a 15 kn wind. The dark red curve shows the same boat, but this time powered by an 8.0 kn breeze. Under the lessened wind, the boat travels more slowly (the dots are closer together), and the boat cuts a much sharper turn.

Windless

The fact that the slower boat has the sharpest turn deserves an extra comment or two.

First of all, if a boat is not moving through the water, the rudder is useless and the boat can’t turn. The force that causes the boat to change direction is generated by the deflection of the water flow passing the angled rudder. This point is sort of obvious, but it’s worth mentioning since most SL builders add a small ‘kick’ to their boats so skippers can still maneuver them even without sail power or headway. The RM-12 and a few other SL boats are more realistic, and you’ll find the RM-12 won’t turn unless it’s moving. 🙂

Second point: Once a boat is underway, the turning force produced goes up with the square of the water velocity over the rudder. In other words, the turning force at 4kn is four times the force at 2kn; the faster boat turns more quickly. However, if you look at the figure above, it shows that the faster boat actually cuts a wider turn. That’s due in large part to the greater residual forward momentum at faster speeds. The turning force may be stronger, but it has more work to do to reverse the boat direction.

A Few Comparisons

Why is any of this worth worrying about? Well actually it’s not worth worrying about, but it is interesting when you start to compare the turning ability of different boats powered by the same wind speed.

turn radius - multi-boat test

Here’s the same chart I posted above, showing the RM-12 at 15 kn (green) and 8.0 kn (purple). I’ve now superimposed two more curves. The orange curve is for the popular Melges-24 racer.

Although it’s quite a speedy boat, the M-24 can cut one of the sharpest turns of the entire sailboat fleet in SL as shown above in orange.

So if you love the maneuverability of the  Melges-24, the chart explains why! The Melges is a spry, high tech, and compact raceboat. It’s designed to slice a turn as sharply as possible and the SL data backs it up!

racers m24

Now look at the other boat I’ve added to the chart above in red. It’s the Wildwind Open 60, a new, very fast ocean racer that’s slated to replace the JMO-60 very soon. The shape of the turn in the Open 60 falls right on top of the RM-12. However, don’t let that fool you. If you look at the distance between each of the dots in the curve, you’ll see that the Open 60 is moving easily twice as fast as the more traditional and reserved RM-12. At those speeds, the Open 60 gets around race marks pretty well, but you do need to leave a lot of room!

turn plots of OP60-OD65-VO70

OK, here’s another comparison to the right. This time it’s for three pretty similar ocean racers: the Wildwind Open 60, the Mesh Shop VO 70, and the Mesh Shop OD 65.

The three boats end up with very similar turning properties. In fact, although they are totally different designs coming from boat yards in  Japan and Netherlands, the Open 60 has a turning curve that nearly exactly overlaps the VO-70. I think that indicates both builders came up with designs that reflected real life performance, and it looks like they both hit the mark. 🙂

loons

And More…

The last chart for today is shown below, and I apologize it’s really ugly; it looks like clumps of seaweed, or Lindsay Lohan’s hair after a particularly rough night.

turn radius - many

The chart overlaps turn plots from a variety of different boats, to give you a flavor of the diversity in the fleet.

There are some interesting findings. For example, the Mesh Shop OD-65 has the same turning radius as the Trudeau New York 30. However, once again the OD-65 has a much faster boat speed that likely explains the apparent similarity.

Two boats have a surprising overlap on the chart that I can’t easily explain. Motor Loon’s Loonetta 31 is an absolutely delightful, fully appointed cruiser. It’s not intended for competitive sailing, and in fact Loon went out of his way to make it clear the boat was not a racer. Well kids, here’s another reason to love your Loonetta: it turns out to have the same turning radius as the Mesh Shop Laser One, and it does it at the same boat speed!

Anyone up for a Loonetta Regatta? 🙂

racers laser

 Quo Vadis

I admit I’m still not sure what to make of these curves, if anything. For the moment, I think they just provide another way to display some performance characteristics of virtual boats we all sail. There are certainly no “good curves,” or bad ones. The results are just interesting, and maybe some are fun.

A few might even have something to do with sailing in SL. 🙂

virtual turns