Normally “hauling ass” means faster than the other boatTried to ask this before but people don’t seem to like giving simple answers. I know its not a simple topic bit please humor me…..
How fast is fast upwind? Lets say in a racing boat like a j80 or take your pick. In decent 10-15 kt wind with reasonable 1 ft waves. You can even express it as a percentage of hull speed. What is a decent VMG directly upwind?
Just a ballpark estimate is fine. Some speed that would make you say “that boat goes to windward like a freight train!”
Thanks Zonker, that was exactly how I thought the run angle an VMG were determined. And now I still don't understand why they say the optimum run angle for the Ohlson is 109deg. in 8kts. of wind. Is it just an error in the polars?The Olson 25 Table and Polar diagram both show much of the same data except the table misses the actual boat speed to windward. The numbers come from a VPP which is a physics model of the boat.
Here's a Farr 40 polar chart. It is in true wind direction. Look at red markings first (beating to windward). Start at blue curve with circle "1". This is the 5 knot WIND speed curve.
Follow the curve along until you see a little square marked with a "2". This is optimum VMG point in 5 knots of wind.
If you follow along the line toward the center to "3" you'll see the true wind angle of the boat is between 40 and 50 or about 45 degrees. Finally from square "2" follow the radial curves and you'll see the boat speed is ~5 knots. (not to be be confused with wind speed of 5 knots).
The VMG can be found by drawing a horizontal line to the vertical axis (in black). That shows VMG is about 3.5 knots in 5 knots of boat speed.
Now let's look at downwind speed in 10 knots. Start at green circle "1" where the 10 curve is circled. Follow the curve until you get to circled "3" square. That is downwind optimum VMG point. If you follow the green line outward you'll see angle is about 150 degrees. Follow the radial curves and you'll see boat speed is about 7+ knots. Finally black horizontal line is VMG downwind at about 6.2 knots.
View attachment 555476 .
Now below is the same data in a table. The table is much more readable and generally you look at the numbers not the pretty picture. Well at least NA's do.
The chart also gives predicted boat speed at various true wind angles. This is in case your course to the next mark is a reach, you want to know "in 8 knots of true wind speed and reaching at 55 degrees what is my target boat speed"? (7.44 knots)
Top row of chart is wind speed, left hand column is wind angle.
Upwind in 5 knots (column 1 in red)
VMG optimum Upwind boat speed = 4.95 knots
VMG optimum angle = 45.4 deg
VMG = 3.48 knots
Downwind in 10 knots (column 1 in green)
VMG optimum downwind boat speed = 7.47
VMG optimum angle = 152.3 deg
VMG downwind = 6.61
View attachment 555477
The -y axis is a litte complicated in that it has tick marks for boat speed but labels for the apparent wind speed curves. Still works the same. No error.Thanks Zonker, that was exactly how I thought the run angle an VMG were determined. And now I still don't understand why they say the optimum run angle for the Ohlson is 109deg. in 8kts. of wind. Is it just an error in the polars?
Doesn't that just mean the highest boat speed is at 109? Best VMG downwind varies on wind speed.Thanks Zonker, that was exactly how I thought the run angle an VMG were determined. And now I still don't understand why they say the optimum run angle for the Ohlson is 109deg. in 8kts. of wind. Is it just an error in the polars?
Polars and accurate instruments are handy downwind…..jibe angles , target speedWell, if you're looking for a basic guide when you're sailing upwind, sans instruments except for boat speed and a compass, if you are sailing at about 45 true wind angle, which you can visualize by looking at the tiniest wavelets and realizing true wind is perpendicular, and where most boats seem to live naturally, if you pinch up 5 degrees and let the boat settle, and you lose less than 10% of your boatspeed, you have a faster vmg. Otherwise, it wasn't worth pinching. If you crack off 5 degrees and your boatspeed increases by more than 10%, cracking off was worth it. It's about 15% from 55 to 60, so diminishing returns. It's about 6% going from 40 to 35 true, but let's not get silly. This helps in chop, you dont need polars.
your question is kinda vague... sailing version of how high is up.Thanks. But that is the kind of vague answer I was talking about. Care to express it as a number or percentage of the hull speed as calculated from the waterline length (and how powered up the boat is)?