On Monday, December 3, 2012 3:00:07 PM UTC-6, Bill D wrote:
On Monday, December 3, 2012 12:22:50 PM UTC-7, aerodyne wrote: Vw is normally set at 70 - 80% of the maneuvering speed which makes a great deal of structural/aerodynamic sense. *With this as a guide, the 2-33's Vw should be 44 - 50mph which would be impossibly slow for a safe launch. *The bottom line is if you thinking of winch launching a Schweizer, you're a test pilot.- Hide quoted text - - Show quoted text - I disagree with the last portion. Va can be approiximated by the SQRT(N) * stall speed. N or load factor, might be as determined by utlity category (4.4) limit load, or gust load factor, typically north of 5gs as specified by the BGCDH of 1962 or much later by JAR22. "sorta" CG hooks are/were made for the 2-33 and 1-26, so they have been test flown. Winching with a nose hook is not likely to enable significant loads before stalling the tail, so I can see why Vg might be higher than Va in some cases. Les at K&L would be best to answer this question. aerodyne OK, I hear you. But, these gliders sometimes require full back stick in a winch launch which is prohibited at airspeeds above Va even without the large winch launch loads. With up to 1000 pounds-force applied to the hook in a downward direction, flying them faster than Va seems insanely dangerous.. I still think a reasonable 2-33 Vw would be less than 50 knots which makes them impractical for winch launch. Yes, they were flight tested but I think it went this way. "Gee, we need up to 65 mph to get a decent launch while staying safely above the loaded stall speed so lets set the winch red line at 69." Thus ignoring maneuvering speed which is 65mph. Ref: http://www.harrishillsoaring.org/doc/sgs2-33manual.pdf I love winch launch but I'm putting my marker down on this one because I expect a 2-33 wing failure probably sooner than later.

that manual says:

Speed to begin manuevering with Caution - 65 MPH

If you look at the following V-n diagram, what we would traditionally consider Va actually occurs at a bit over 70 mph. It isn't immediately clear to me but i'm guessing that chart is based on max gross weight.

the manual also says "Winch or Auto towing can produce high loads, but if the auto-winch placard speed is observed, this will be within safe limits. The best ground launch climb is achieved at speeds well below placard limits"

there are many 2-XX's out there with LOTS of ground launches. I think that if they really had mis calculated it there already would've been a wing failure.