Saturday, September23, 2017 L-36.com

True Wind Direction Chart Help



For this discussion I have created a reduced chart so we can focus on one example.

twd_chart

We read the apparent wind as 17 knots. Our example boat has the following boat speed vs apparent wind angle:
example

Our goal using this chart is to sail at 45 degrees to the true wind. To start, we are going to sail at 6.5 knots. Looking at our example boat we see that the boat is sailing at an apparent wind angle of 34 degrees which we read off the masthead fly.

We look at our chart and see that at 6.5 knots in 17 knots of apparent wind we should be pointing 29 degrees apparent and we are way off that so we need to head up. We head up and the boat slows down to 5.5 knots. After letting things settle down we read the apparent wind angle and see that it is 28 degrees. Out chart says that at 5.5 knots we should be at 32 degrees to the apparent wind so we are pinching. Now we try 6 knots. At that boat speed, the apparent wind angle is about 31 degrees and we see from the chart that the entry for 6 knots boat speed at 17 knots apparent wind is 31 degrees so we know we are now heading at 45 degrees to the true wind.


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