There's a lot of expertise out there that can help me win our weekly twilight!! I've only had Mustang Sally a month and been in three twilights on Friday evenings. She sailed better than I expected. Last week we were tacking - pointing quite high and right behind another yacht but not catching her. I then fell away a few degrees (5-10?) and immediately overtook her quite quickly!! Even though this was a slightly longer route to the mark we got there before the other yacht. A very good example of "high pointing" not necessarily being the fastest way to sail. But then downwind we couldn't agree on how to sail her ( and lost a lot of ground!!). The wind was dead behind - and not very strong (guess 6-7knts - instruments not working) - the yacht club/finishing line dead ahead. I thought we should tack downwind, taking an angle where we were not gull-winging, with both sails on lee side and just enough wind in the jib. Even though this would be a longer course, we should not lose much speed on the downwind tacks and maybe would get there quicker. The alternative view was to go in as straight a line as possible. What would you do??
Downwind Sailing
- Thread starter Malcolm7410
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Downwind
Assuming no spinnaker or cruising chute is carried, EVERY boat sails faster downwind when there is a proper airflow over the main and foresail. Proper flow cannot exist when dead running. This situation persists until the boat is moving at max hull speed, ie. in strong breezes, then the shortest route is quickest. I suggest you sail to keep the jib full and I have tell tales at mid chord on the main as well as on the leach. In light to moderate breezes the additional distance sailed by tacking downwind is more than compensated by the considerable extra speed. Watch for the shifts and use them just as when beating. This is more difficult to do than when beating so watch the windex, note the wind direction and your course and be ready to gybe. Gybing takes less time than tacking and there is very little loss of boatspeed. Having said that there are tactical situations which may make you not want to do tack downwind, ie. when trying to blanket the boat ahead - watch that others don't sail round you though. Good luck with the evening races.
Assuming no spinnaker or cruising chute is carried, EVERY boat sails faster downwind when there is a proper airflow over the main and foresail. Proper flow cannot exist when dead running. This situation persists until the boat is moving at max hull speed, ie. in strong breezes, then the shortest route is quickest. I suggest you sail to keep the jib full and I have tell tales at mid chord on the main as well as on the leach. In light to moderate breezes the additional distance sailed by tacking downwind is more than compensated by the considerable extra speed. Watch for the shifts and use them just as when beating. This is more difficult to do than when beating so watch the windex, note the wind direction and your course and be ready to gybe. Gybing takes less time than tacking and there is very little loss of boatspeed. Having said that there are tactical situations which may make you not want to do tack downwind, ie. when trying to blanket the boat ahead - watch that others don't sail round you though. Good luck with the evening races.
If you have a GPS
and waypoints to the mark, use the velocity made good measurement to find our optimum angle and speed to the mark. Mark
and waypoints to the mark, use the velocity made good measurement to find our optimum angle and speed to the mark. Mark
DDW = Dead Last
Malcolm, I have been told that sailing dead down wind is tantamount to dead last. It is generally the slowest point of sail. Instead, it is a good idea to use the suggestion from Mark. VMG is the fastest way to sail to a downwind mark. Most GPS's will have this feature. You will need to experiment to find the best angle to achieve the fastest speed to the waypoint (finish line). It might be that you will need to sail as much as 30 to 35 degrees off your rhumb line (shortest distance) to gain the fastest speed. You will see your VMG begin to go down as you head off more from the direct course. Your gybe point will be when the waypoint is equal to twice the angle you are sailing off the direct line to fetch the finish. This sounds confusing, but it works. And, keep this as your secret and the rest of the fleet will be in awe of your sailing ability. Best, John Richard s/v Jack's Place
Malcolm, I have been told that sailing dead down wind is tantamount to dead last. It is generally the slowest point of sail. Instead, it is a good idea to use the suggestion from Mark. VMG is the fastest way to sail to a downwind mark. Most GPS's will have this feature. You will need to experiment to find the best angle to achieve the fastest speed to the waypoint (finish line). It might be that you will need to sail as much as 30 to 35 degrees off your rhumb line (shortest distance) to gain the fastest speed. You will see your VMG begin to go down as you head off more from the direct course. Your gybe point will be when the waypoint is equal to twice the angle you are sailing off the direct line to fetch the finish. This sounds confusing, but it works. And, keep this as your secret and the rest of the fleet will be in awe of your sailing ability. Best, John Richard s/v Jack's Place
If you want to do it right
you can construct some polars for your boat. Donalex and Mark are exactly correct in their responses. Create a chart documenting your VMG towards a mark directly downwind at various angles from DDW to say, maybe 135 degrees. Do this for a variety of windspeeds. This mapping of your particular boats best performance with these chosen angles and windspeeds are it's polars. You'll find (as Donalex points out) that gybing typically is a better VMG downwind in lighter air. In heavier air when you can get hull speed, or something close to it, a straight line will be faster. Knowing exactly where to make that transition for your particular boat is why polars are important. How detailed you make it will depend on how serious you want to be. By doing this you can choose with confidence the best course in the heat of the race. Grand prix level racers spend a good deal of time and energy doing exactly this. Your discovery of bearing off a little, 'heating it up' as they say, is another example of your inadvertently locating a better 'polar' for your boat, only this time going to weather. Good luck and above all, have fun!
you can construct some polars for your boat. Donalex and Mark are exactly correct in their responses. Create a chart documenting your VMG towards a mark directly downwind at various angles from DDW to say, maybe 135 degrees. Do this for a variety of windspeeds. This mapping of your particular boats best performance with these chosen angles and windspeeds are it's polars. You'll find (as Donalex points out) that gybing typically is a better VMG downwind in lighter air. In heavier air when you can get hull speed, or something close to it, a straight line will be faster. Knowing exactly where to make that transition for your particular boat is why polars are important. How detailed you make it will depend on how serious you want to be. By doing this you can choose with confidence the best course in the heat of the race. Grand prix level racers spend a good deal of time and energy doing exactly this. Your discovery of bearing off a little, 'heating it up' as they say, is another example of your inadvertently locating a better 'polar' for your boat, only this time going to weather. Good luck and above all, have fun!
software
Max Sea has a racing module for racing. shows real time lay lines, and a host of other racing info. if you have polars for your boat (or you can create them using the Max Sea software) and your instruments are interfaced the software will calc real time fastest approach to the mark etc. neat software. Bryce S/V Spellbinder H 410
Max Sea has a racing module for racing. shows real time lay lines, and a host of other racing info. if you have polars for your boat (or you can create them using the Max Sea software) and your instruments are interfaced the software will calc real time fastest approach to the mark etc. neat software. Bryce S/V Spellbinder H 410
Tonights the night!!
Friday twilight tonight to test out my new knowledge! Weather forecast for Sydney harbour is 8/13 knots E/SE. The worst!! Very light and SE is DDW on way back to yacht club from last mark. At lest now, armed with a print-out of this thread, I'll win the debate about how to sail her. If you want to see how we go you can view the results on www.rsys.com.au go to "Results" then "Friday Twilight" then "Division A" and then today's date. Then look for "Mustang Sally". It is handicap start so order of yachts in list/over line is the result. It might be embarrasing!! Anyone know where I can find an existing polar diagram for a 44 hull with fully battenned main?? I'll in meantime try to track down the MaxSea software. Thanks again p.s. week before last we were "smoking" on last leg when on broad reach with wind in the teens. Overtaking everyone!! She loves reaching!
Friday twilight tonight to test out my new knowledge! Weather forecast for Sydney harbour is 8/13 knots E/SE. The worst!! Very light and SE is DDW on way back to yacht club from last mark. At lest now, armed with a print-out of this thread, I'll win the debate about how to sail her. If you want to see how we go you can view the results on www.rsys.com.au go to "Results" then "Friday Twilight" then "Division A" and then today's date. Then look for "Mustang Sally". It is handicap start so order of yachts in list/over line is the result. It might be embarrasing!! Anyone know where I can find an existing polar diagram for a 44 hull with fully battenned main?? I'll in meantime try to track down the MaxSea software. Thanks again p.s. week before last we were "smoking" on last leg when on broad reach with wind in the teens. Overtaking everyone!! She loves reaching!
VMG, Top Speed, Target Boat Speed
In reading some of these posts, I realize that some terminology is getting mixed up. The best boat speed sailed is not usually the fastest way to the finish line. Malcolm has found out that pointing higher is also not usually the fast way to the finish line. Highest VMG is the answer. This is a combination of sailing the appropriate boat speed at the best wind angle, otherwise known as Target Boat Speed. If boat speed is lower than target boat speed, foot off slightly. If boat speed is too high, point higher. When target boat speed is achieved, you will be sailing at max VMG. John, You stated that “You will see your VMG begin to go down as you head off more from the direct course.” This is not true most of the time. Most of the time you will achieve the highest VMG by sailing other than the direct course. The major exception to this is in very high wind conditions. PS, Best of luck with your Friday Twilight Malcom.
In reading some of these posts, I realize that some terminology is getting mixed up. The best boat speed sailed is not usually the fastest way to the finish line. Malcolm has found out that pointing higher is also not usually the fast way to the finish line. Highest VMG is the answer. This is a combination of sailing the appropriate boat speed at the best wind angle, otherwise known as Target Boat Speed. If boat speed is lower than target boat speed, foot off slightly. If boat speed is too high, point higher. When target boat speed is achieved, you will be sailing at max VMG. John, You stated that “You will see your VMG begin to go down as you head off more from the direct course.” This is not true most of the time. Most of the time you will achieve the highest VMG by sailing other than the direct course. The major exception to this is in very high wind conditions. PS, Best of luck with your Friday Twilight Malcom.
maxsea
Malcom, link to MaxSea. they have an Autralian distributer. Bryce S/V Spellbinder H410 http://maxsea.com/
Malcom, link to MaxSea. they have an Autralian distributer. Bryce S/V Spellbinder H410 http://maxsea.com/
Thanks Bryce
I'ved followed up your intro to maxsea and emailed AUstralian distributor - unfortunately the're west coast and I'm east - but hopefully they have some east-coast agent. By the way we performed 'reasonably' well for a cruising yacht last Friday - almost exactly the same wind conditions (8/13 knts S/SE - which means dead down wind for last run up to yacht club) We tacked downwind and 'played around' with angle - seemed to perform at about 40deg off the wind - however have not set up GPA yet to enter waypoints and get VMG to waypoint calculation. Hopefully this Friday!!
I'ved followed up your intro to maxsea and emailed AUstralian distributor - unfortunately the're west coast and I'm east - but hopefully they have some east-coast agent. By the way we performed 'reasonably' well for a cruising yacht last Friday - almost exactly the same wind conditions (8/13 knts S/SE - which means dead down wind for last run up to yacht club) We tacked downwind and 'played around' with angle - seemed to perform at about 40deg off the wind - however have not set up GPA yet to enter waypoints and get VMG to waypoint calculation. Hopefully this Friday!!
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