I originally sent this at 2:44 am. The total size was just over 4000 bytes so maybe it was eaten by the list serve. I cut the included FAR and Larry's response that said: my plane is not flying, but I've heard others have done it.
Before you start spinning, think about how much of a safety factor you want. Apparently back in 1995 there was concern that the wing attach fittings were not strong enough for the 2S because of the longer wing and should be reinforced if "maneuvering extensively at gross weights exceeding 980 pounds." It was then found that the analysis was "based on outdated strength properties for AIAI 4130 steel." After revising the strength properties the fittings were found to have a safety margin of 16.4 percent based on a gross weight of 1050 of pounds and an ultimate load factor of 6.0, which corresponds to a limit load factor of 4.0. Which puts the plane into the normal category (see FAR 23.337). Spins are prohibited for normal category aircraft. Granted that 4.4 (the utility load factor) is only a 10 percent increase over 4.0 and you had a 16 percent margin so you might be able to conclude that you have a plane that would qualify as utility. Of course, there is another 10 percent increase with that extra gross weight at 1150 which puts you out of the safety zone. Okay, play like the spam cans and put a weight limit for utility operations. The analysis assumed a stock KR2S. So those of you who have widened the fuselage and removed an inch or two of 48 inch chord flying surface, how has that affected the load distribution? How much of that load was transferred to the outboard wings? How much safety margin is left? And then there is the question "how much faith do you have in those fittings?" How many times have the wings been removed and reinstalled? Are the bolts uniformly tightened? Have the holes been reshaped? Did you drill the holes correctly? Did someone else drill the holes correctly? Does the batch of steel your parts are made from have at least the strength used in the fitting analysis, i.e. does it meet Condition N, specification MIL-S-18729? Checking the archives there was some problem with "Bendable wing fittings" posted on Feb 12 and 13 of 1998. Apparently, quality control was inadequate and somebody ended up with a set of fittings that was substandard. Did you? And even if the wing will handle it, will everything else? What about baggage boxes? See Mark Langford's pictures of the 2003 gathering where Marty had a sudden loss of elevator control. http://home.hiwaay.net/~langford/redoak2003/ How high would the "pucker factor" be if you lost elevator control while trying to recover from a spin? In conclusion, the plane isn't designed for spins, so don't spin it. -- wesley scott k...@spottedowl.biz
