Sheets to the Wind

sheets to the wind

by Ed Kegel and Moontears Vought

Greetings all! I’m fresh from Blake Sea, sunburned, wind burned, fed up with crashes (stopped counting after the first dozen) and worn out, but satisfied. I now understand her. No, not my girl friend, my J-Class.  Having just completed something I’ve wanted to do from the day I got her………. Sea Trials. And if you think this is a long note, well… it was a long day!

Sugar Reef

Sugar Reef

Have you ever wondered how she behaves under different sheet conditions? How close do I need to trim, for best performance? To reef or not reef, that is the question. And does she take after her distant cousin the Tako in regards to the Spinnaker angles, or does she have her own special needs? Just like a woman, she is complex, finicky at times, can be a real bitch,  but in the end – A JOY TO RIDE.

Many thanks to Moontears Vought, who helped me with this endeaver both with sailing back and forth on the Blake Sea add nauseum, and for being a great sounding board. Her thoughts are always sound and worth investigating. I would also like to thank the numerous other people who’s articles contributed to my understand of sailing in SL. Last but not least thank you Jane Fossett and JoyofRLC Acker, for helping to spread the wealth of information available in various forums and sources about this boat and sailing in general in SL.

OK, enough accolades; lets get to the results. I don’t purport to be a nautical expert, nor a marine engineer. But I do know how to conduct an experiment, limit changes to one variable as much as possible here in SL, and read the data. The conclusions I draw, while they may be up for debate by some, like the physicians debated a person’s illness in Moliere’s time. I am satisfied from the emperical, experimental evidence that I am on sound ground with my  conclusions and will sail her based on that understanding.

QUESTION:
1. Moon and I wanted to find out if under a steady wind the boat exhibited any “sweet spots” or preferences in sail angles using the Jib and main sheets.

CONDITIONS:
Venue was the open expanse of Blake Sea. Setting up our own wind at 12m/sec with no variations in speed or angle, we began trying various sail trims. To start we left the main in “Reef 0” condition. Moon was skippering, and I was aboard on the hatchway, centered and did not correct for heel. We took readings of AWA, sheet angles, and boat speed from the INFO HUD. Boat helm was adjusted via the left/right keyboard arrow keys, and sheet trim was made via chat commands imbedded in gestures linked to F-Keys.

CONCLUSIONS:
A. The Jib and main sheets appear to like the same angle setting at least as far as the sea conditons allowed us to tell. Any mismatch beyond a degree cause a fall off in speed at all angles of wind, sail, and speed we tried.

B. For best speed at whatever heading, the boat wants constant correction of both helm and sail angle. Even with steady wind, to squeeze the last tenths of speed out of her you need to be sailing her every second. And given the variability of race winds, changing direction slightly all the time, its essential to keep adjusting the helm and trimming sails in and out by a degree or two. The AWA is constantly changing.

C. Sail angle adjustment by single degrees is critical for best speed. Yes you can set and cruise for a leasurly sail but again we were looking for every last tenth of a meter per second.

D. Color of sails doesn’t matter, LOL.

E. After repeated trials the optimum sail angle is 50% of the AWA (Apparent Wind Angle) below or above 50%  cause a speed drop off. The following data was typical for various angles.

DATA:
AWA,  sheet angle jib & main,  m/sec boat achieved

050,  027,   7.1
050,  026,   7.2
050,  025,   7.4
050,  024,   7.3
050,  023,   6.8

As soon as you get two or more degrees away from 50% speed really starts falling off. So need to trim constantly via helm and sail.

F. Three (3) sweet spots stood out to us.
AWA 34 degrees both sails set to 17 degrees, speed 4.0m/sec.
AWA 46 degrees both sails set to 23 degrees, speed 6.9m/sec.
AWA 66 degrees both sails set to 33 degrees, speed 10.0m/sec.
Either due to a stepped perforemance level indicated by a change in slope of the graphed points or the highest speed achieved overall with a speed fall off either side of that angle combination. Data is as follows:

DATA:
round one EK 01AWA,  sheet angle jib & main,  m/sec boat achieved

030,  015,  2.0
032,  017,  2.6
034,  017,  4.0    Close haul sweet spot
040,  020,  4.4
042,  021,   5.3
044,  022,   6.1
045,  023,   6.3
046,  023,   6.9    Next slight Plateau
048,  024,   7.2
050,  025,   7.4
060,  030,   9.4
064,  032,   9.9
066,  033,   10.0   Best performance
068,  034,   9.9
070,   035,   9.7
080,  040,   8.9
090,  045,   8.1
100,  050,   7.5
110,  055,   6.9
120,  060,   6.3
130,  065,   5.8
140,  070,   5.3
150,  075,   4.9
160,  080.   4.4
170,  085,   3.7
170,  090,   3.6
170,  090,   2.5   wing on wing
179,  090,   1.7   wing on wing

Ok that should be enough on question one.

J-Classic Round One 04

QUESTION:
2. How does heel affect speed and what is the relationship between reefing to correct heel and crew movement to rail to correct heel? (We observed that in the first race with two crew, reefing the main slowed us down. Yet, when sailing with just skipper reefing mainsail on close hauls it really improved speed.)

A. Tryin it out with various crew showed that the benefits of reducing heel occur with either reefing or crew movement.  It also depends on wind speed. In the first race two crew with a 10 m/sec wind was enough to reduce heel. Adding the reef as well caused a decrease in speed because of reduced sail area. The crew was sufficient to bring heel below the level it reduced speed. With only one crew and a 12m/sec wind speed there was still too much heel, and therefore reefing leveled out the boat more and increased the speed.  Bottom line: try reefing; if speed increases, use it. If not, don’t.

DATA:
ed kegel 03For one (1) crew member in addition to skipper riding rails properly with 12m/sec wind.
AWA,  sheet angle jib & main,  reef state,  m/sec boat achieved

066,  033,   reef 0,     9.7
066,  033,   reef 1,  10.6

046,  023,   reef 0,     5.1
046,  023,   reef 1,   13.7

034,  017,   reef 0,     5.0
034,  017,   reef 1,     7.3

QUESTION:
3. Trimming the Spinnaker seems more dificult, what are the best trim angles? The Tako Spin has best results trimming to AWA – 90. IS this the same in the J-Class? Example would be AWA is 150 so in Tako trim main to 75 and spinnaker to 60 for best speed.
 Does wing on wing work for the spinnaker and main? Is using the spinnaker alone a good idea?

CONCLUSIONS:
A. Under no conditions were we able to show the Spinnaker alone worked well. Always use the main as well.

B. The J-Class gets best speed when Spinnaker and Main sail are both trimmed the same, to half the AWA. In the above example AWA of 150 requires both sails trimmed to 75 for best speed. Just like with the Jib and main combination being within one (1) degree of 50% of AWA gets you the fastest result. The luffing of the spinnaker stops when you are within ten (10) degrees of the 50% mark. But stopping the luffing does not get you to the best speed. for that you need to trim to 50% of AWA.

C. Wing on wing does not work well with the Spinnaker.  with 12m/sec steady wind dead astern, wing on wing only gave 1.7m/sec boat speed. In fact the best speeds are obtained when the wind is not at 179 degrees (directly aft). Having a few degrees off center gives the best speed. You will need to tack the Spinnker and main to the correct side. The confusing part is the Spinnaker boom goes on opposite side of the main boom. This looks strange after seeing the jib boom on the same side as the main boom.

Jaspar and Ed

WRONG RACE WINDS
A note of warning about race wind and not finishing a race. The boat will retain the last race wind and not reset to the new wind if you crashed and did not cross the finish line on a previous race. You can prevent this situation by discarding the boat, (delete it) instead of taking back to inventory. You have the Master boat in inventory , always rez that one, and never a previous boat uses before.

Another simple solution would be, before a race, all boats should do a practice run. The boats cross the start line, sail for at least one minute, then return and get a FINISH time. That would ensure all racing boats are listening to the windsetter and using the right wind.

HOW DOES THE WIND WORK?
Found this link in one of Jane’s posts. Its especially helpful in understanding the variability of direction and speed that the race winds we are using have. Basically it means that at one point when you practice you might make a close haul by an island or bouy, yet the next practice or on race day, not make that same path successfully. It’s due to the variability of direction and intensity of the winds.

http://slsailing.com/archives/220

Hope all this helps you sail better and faster,
Moon & Ed

Ed Kegel dueling Jaspar Recreant in Round One

Ed Kegel dueling Jaspar Recreant in Round One

 
                                                                                (¯`v´¯)      
                                                           *:-.,_,.-:*’´ `*.¸.*´`’*:-.,_,.-:*

5 responses to “Sheets to the Wind

  1. Thanks, Ed and Moontears. This was really helpful!

    As an add-on to your #2, some of us were wondering the other day if avatar characteristics factored into the effect of heeling.

    More specifically, I have a petite avatar. Is my effect on heeling less than that of someone with an avatar that looks like the Stay Puft Marshmallow Man? Or, is it simply enough that an avatar is present (and trimming properly)?

  2. That was a nice and very complete article, but those speeds in your data while you were looking for sweet spots look really really low for a 12 m/s wind unless your not reefing in your test.

  3. Naeve,
    I have no idea about apparent avatar weight. But I doubt if it makes a difference, as that’s getting a bit complex and I don’t think the boat looks at more than the fact you are there and which of the five positions windward to lee you are at.

    Alain,
    Yes we just ran the tests with reef 0 and I did not move windward to reduce hiking, ergo the low speeds. From the other charts and data posted in the follow up articles, I can see that reefing, is a critical component. As is crew movement to windward.

    In studying the other graphs I further realize that the sweet spots I was seeking vary based on wind speed and reef state. It appears that as the wind speed increases the best possible speed moves to larger AWA, which makes sense. So I have a range, a sweet area, rather than a spot.

    Still this was a good exercise in fundamentally understanding the dynamics involved in sailing wind powered boats.

  4. ” Just like a woman, she is complex, finicky at times, can be a real bitch, but in the end – A JOY TO RIDE.”
    Shame on you for saying such a thing! Were not all finicky or bitches! And were not here to be ridden! shame shame shame.

  5. Delinda,

    You are right of course, i hang my head in shame. i appologise to You and anyone else i may have offended with the crass and crude statement.

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