As most of you are aware, intructional information regarding boat performance, sail trimming and sheeting is usually specific to the various wind velocities. Whether it be in a Catamaran book, manual or video, the description usually reads something like...in heavy wind... or in light air...you do such and such...!
The problem is, I have not read any good figures regarding what constitutes light, medium and heavy wind/air. To some extent, some of this is obvious - ie. if the shingles are blowing off my house I can safely assume this is "heavy" air.
Are there any generally accepted figures on this?
Dave
"Light / Medium / Heavy" air depends on the skill of the sailor and the conditions they are used to. What most of us in North America call "heavy air" is medium to an Australian.
For a Hobie 16 in North America, this is the generally accepted ranges:
Light air is 0 to 7 knts (no trapezing)
Medium is 7 to 15 (transitional trapezing to solid double trap)
Heavy is 15+ (depower mode)
It also varies by boat. A Hobie 17 is just coming alive in stuff that a 16 would consider "heavy".
I believe Phil Berman defined medium air as eight to 16 mph.
Another factor would be water surface conditions.
Thanks guys,
That helps a lot
Dave 
If you come out to my lake in TX then "light" is still light but "medium" is more like 10-20 and then "heavy" is 21-to-"I'm scared to go out but what the hell it took me 25 minutes to drive up here and I'm going to enjoy myself..."
Hey Matt: Congratulations on the big win! How's it feel to be a National Champion? The 14 felt just right at about 20 knots. I got killed when it went below 15. The experience of the skipper and the weight of the skipper or team has a lot to do with it. Single handing the 16 in 15K is a real handful. The other thing is that most sailors way over estimate what it is really blowing. I've often heard guys say they were sailing in 30K when the real readings were more like 15-18K. Dave, the sheets are always going to be a pain. I try to put my front foot on the main to keep it from washing over.
pbisesi,
I know what you mean re: over-estimating wind speed. Without a wind meter I personally found it very difficult/almost useless to estimate.
Regarding the sheets and various lines, I am getting the idea that there is not much one can do other that just manage it as efficiently as possible.
...it rarely hurts to ask though.
Matt - I was unaware you had recently won an important sailing event - congratulations and thanks for still helping the rest of us out with the little things!
Dave 
Dave: You can follow much of what is going on with Hobies at the HCA website: HCA-NA.org. Under major championships there are stories and links to the event websites. Matt is the New Hobie 17 North American Champion. Matt was in front by a large margin on the last day and I was going to post a message and then remembered "The pitcher is throwing a no-hitter" curse and just waited. Sure enough the blog reports he was in a collision and flipped. Breaking the boat was the only way to lose. He recoverd and went on to win by a wide margin. Matt, I would like to hear what happened. P.S Matt also got second in the 14's
I pretty much agree with Jamie, but if I had to give my own numbers:
Light: 0 to 8mph
Medium: 8 to 18mph
Heavy: 18mph and above
When I'm by myself I don't like wind over 22mph. But if you have a experienced crew, then "terror" sailing can be quite entertaining. In the "old days" my sailing partner and I would pray for the local weatherman to say "inland lake wind warnings". But he got married, and his wife frowns on men behaving badly.
One thing I really hate is a "punchy" wind. This is where sudden gusts exceed the base wind by a lot.-It is as if the jolly green giant put his fist in your sail from out of nowhere. Once, I and my sailing partner were moving along in a moderate breeze and a gust instantly knocked the boat over, -and we were sitting in the middle of the main above the numbers wondering HOW we got there.
Hey
I had/have the same problem with some of the literature out there for Hobies. Never knew which condition was which. But Matt made a good point. It depends much on the experience of the sailor. When my girl friend and I started sailing, anything over 15kn was ‘heavy’. The problem is that we have strong continual trade winds which often blow 25kn (constant- never mind the gusts), the stronger days going over 30knots. Thus, our term for ‘heavy wind’ moved up very quickly as we gained experience. Medium down here is probably 12-20knots (we haven’t quite mastered the 25+ range and I start stressing when the weather man predicts in this region). It not nice when you’re the one standing on the beach because you think the wind is too strong while the others go out. But it just takes time, even my girl friend can sail happily at about 22knots now 
The guys in Cape Town will probably be like the Ozies..
My two cents…
Clint
It seems to me that the wind always feels stronger while on the beach than it does while sailing but the waves look smaller on the beach than when you get into them (especially if you are trying to punch out through an onshore breeze 
).