If you're referring to the angle of the windsock when "calibrated" for a given windspeed, there's no such thing. Manufacturers claim that their windsocks are calibrated, but this is misleading. Windsocks are not calibrated, and do not sit at any given angle for a particular value, nor are they "calibrated" to stick straight out at any given value.
As a general rule, straight out is about fifteen knots or greater, and half up is about eight.
Large windsocks will erect at much higher wind values than small socks. The location makes a difference, as does the mounting system. The type of fabric, the age of the sock, the permeability of the fabric with type and age, etc.
Quote "If you're referring to the angle of the windsock when "calibrated" for a given windspeed, there's no such thing. Manufacturers claim that their windsocks are calibrated, but this is misleading. Windsocks are not calibrated, and do not sit at any given angle for a particular value, nor are they "calibrated" to stick straight out at any given value. "
Thanks avbug, that's all I needed.
If anyone can produce a "certified" standard let me know and I will pay up.
I should qualify my response by stating that a windsock can be calibrated; NASA Ames spent a great deal of time calibrating a series of windsocks for use on the Mars Pathfinder experiment to measure martian winds. This was done on a sock-by-sock basis in a wind tunnel, and the sock was indeed calibrated in accordance with a a computer model.
Calibration implies specific identifiable increments of measurement which are repeatable and consistant. A typical field windsock at most airports or industrial locations doesn't meet that standard, and no standard exists for routine calibration to ensure that any particular standard is met. Further, one sock may require eighteen knots to stand straight out, while another only needs 12. The same sock that responded to 18 knots when new, might need 20 when old and more permeable. When either sock is wet, this "calibration" changes. The windsock is nothing more than a basic visual indicator to approximate wind direction and strength, but nothing more.
A sock may be individually calibrated, but it's so darn hard to find a good sock calibration service these days...and when was the last time you got a NOTAM that the wind sock is down for maintenance?
In Wyoming, we just used a logging chain, and it stuck pretty much straight out most of the time. Cows grew up with two legs six inches shorter on one side, because they leaned so much. We assumed that when a cow fell over, wind velocity had dropped below about 18 knots, and it was safe to go outside and oil the chain.
At higher velocities, we often stationed a chicken in a calibrated wire mesh cage on the front lawn. If the chicken laid an egg and the egg was blown back inside the chicken, we wind speed was said to be appoximately 69 knots. At approximately 82 knots, the feathers left the chicken, and at 90 knots, the cage was gone, along with the denuded chicken.
On high-chicken-loss days, when carrying passengers in cubs and other such high tech equipment, we found that it was usually cheaper to fly the passengers from the upwind destination, but to bus them from the downwind destination...along with the aircraft on a truck trailer. Aside from the dismal groundspeed, there was far too much danger of birdstrikes headed into the wind. It wasn't the chicken that did the damage, rather than **CENSORED****CENSORED****CENSORED****CENSORED**ed calibrated cage.