QLD
1197 posts
When some one tells me their boat can point 25-30deg to the wind, the first question I ask is that 'Apparent Wind'. As most of you would know, the definition of apparent wind is the result of true wind and the speed of the boat through the water. So with a steady 15knt breeze, a boat moving at
7knts boat speed - App Wind 30deg - True Wind is 43.5 Deg
6knts boat speed - App Wind 30deg - True Wind is 41.5 Deg
5knts boat speed - App Wind 30deg - True Wind is 39.6 Deg
4knts boat speed - App Wind 30deg - True Wind is 37.7 Deg
7knts boat speed - True Wind 45deg - App Wind is 31.1 Deg
6knts boat speed - True Wind 45deg - App Wind is 32.6 Deg
5knts boat speed - True Wind 45deg - App Wind is 34.2 Deg
4knts boat speed - True Wind 45deg - App Wind is 36.0 Deg
So if you like to quote your boats pointing ability with regard to 'Apparent Wind' then you should also add the boat speed and wind conditions so we can do the vector calculation. Or maybe you could just give to us for True Wind and save the brain strain.
With the massive mains on cats theses days (and their inability to heel/spill) maybe you could make this tip No 11
11 - The skipper who only looks at Apparent Wind will one day have to take his main to the sail loft after changing course from a down wind run to a reach.
Definition of apparent wind - The Apparent wind is the wind experienced by an observer in motion and is the relative velocity of the wind in relation to the observer. Apparent wind velocity is the vector sum of the true wind and the headwind an object would experience in still air.
QLD
12365 posts
I have sailed to a wind instrument in the past but as it was not interfaced with a speed instrument it would only read apparent wind.
I really enjoyed using it and found it very good for helming to gain the greatest speed.
The yacht was an IOR 2 tonner tiller steered and wind conditions were 12 to 18 knots. I was sailing with head sail only and the desired course was pointing but not hard on the wind. Boat speed was 7 knots plus.
I had a whale of a time with the other two crew sleeping down below.
These days my 30 footer only has a wind bird atop the mast and by observing that, the tell tales on the sail and SOG by GPS and I still have a whale of a time sailing her.
A wind instrument would be nice but not vital.
NSW
86 posts
hey cisco I agree they are a nice thing to have but the bloody corellas
keep chewing ours off the top of the mast ,and it costs $85 to replace
the indicator and speed cups, so we have forgotten about it
and joshua slocum never had one anyway cheers Ray
