Nice work Oscar. One thing most people miss in the analysis, however, is the variability of the materials. Wood can be 50 percent (or more) stronger than the published low limit. So, we need to test the actual parts to be used, or allow a reasonable safety factor for the material variability. That's why we use certified Sitka spruce and DESIGN using the published lower limit of strength.
You're certainly right about the enhancement of support by the ribs/wing structure. It's the offset of the load that is causing the failure mode in your test. Maybe some guidance would be appropriate. To be sure, either test the finished product or allow some margin of safety. The more I learn, the more uncomfortable I feel in some areas. The experience to date of the KR designs is comforting, but I wonder how many of the aircraft have been flown to the published limits. I'll bet nearly none. Ron Freiberger mail to rfreiberger at swfla.rr.com <- substitute an @ sign ;o) -----Original Message----- From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net] On Behalf Of Oscar Zuniga check out http://www.flysquirrel.net/wing/spartest.html and see if you can duplicate the high-tech test setup detailed there
