Another fun day at the Marina. Had the morning wind phenomena again. Nice wind on the initial heating during the morning. Once the air temperature goes over 90 F the wind gets soft and patchy. I sailed my 6.9. Sylvain was already there with his wife and kids. He was teaching them in the beginner cove. It's nice that you can stand up in most of it. And just enough wind spills into the cove. I was able to head up to the the main pool. I tacked with each wind shift and got up there in no time. Later Rick followed me up there on his 6.5. And Susan followed too on her Laser. Water was cooler up there. Rick and I made long reaches in the patchy wind. I came back after a few hours. Got some shots of Rich on his 8.5 and Sylvain on his 6.8. A nice freeride day with friends.
Bloomington
Champaign
Decatur
6 of the day's 16 photos.
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Rich (8.5 sail) and Sylvain (6.8 sail)
Rich (8.5 sail) and Sylvain (6.8 sail)
Sylvain (6.8 sail) rippin'
Rich (8.5 sail) was tearing into jibes.
Rich (8.5 sail)
'till next time
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More on wind density if you want to nerd out...
Weight of the Wind
weather.mailasail.com/Franks-Weather/Weight-Of-Wind
"In dry air"
"The starting point is that the force on a sail or windmill blade varies directly with air density and as the square of the wind speed. Fairly obviously, cold air is denser than warm air and cold air will create a greater force than warm air at the same speed."
"The effect of water vapour" ( humidity )
"The effect will be compounded by the fact that moist air is less dense than dry air. This is because water vapour is a relatively light gas compared to oxygen and nitrogen - the main constituents of the air. The chemical formula for water is H2O ie two molecules of hydrogen to one of oxygen. When water vapour content increases, the amount of oxygen and nitrogen in a given volume of air decreases."
"The density of the air as a whole decreases because the mass decreases."
"For a fairly extreme example, in the tropics with a temperature of 32°C (89.6 F) and 90% humidity, the air density is 1.14 kg/m3. In a northerly airstream around the UK, we might have temperatures of 10°C (50 F) and 10% humidity giving an air density of 1.25 kg/m3. So with cold dry air, the force of the wind on a sail would be about 10% higher than with warm humid air at the same wind speed."