Structural design criteria for all metal aircraft require a safety margin of 1.5, or 1.5 times the max g rating, as the metal will stretch and distort at the load limit. For wood, the safety margin is 2, as wood will go to the limit and return without damage. For an aircraft designed to withstand repeated g loads od 7 g's, the ultimate load it should withstand is 14 g's. With an increase of MTOW, as many KR's have been built, the design g rating would have to be reduced to cater for this, but by how much would be the question. The original design has the fuel in the fuselage, above the pilot's feet, but moving the fuel to the outer wings, where the lift is, would modify the spread of load in the structure, probably to the owner's advantage. Personally, I am placing all fuel in my wings, where the only negative I can see would be on a heavy landing with full fuel.
My references are from "Design For Flying" (Thurston) As always, fly safe Vern Taylor Darwin Australia -----Original Message----- From: KRnet <krnet-boun...@list.krnet.org> On Behalf Of Flesner via KRnet Sent: Sunday, 5 April 2020 6:25 AM To: Mark Langford via KRnet <krnet@list.krnet.org> Cc: Flesner <fles...@frontier.com> Subject: Re: KR> spar failure On 4/4/2020 8:16 AM, Mark Langford via KRnet wrote: > > As for spar tests, please take a look at the 2008 KR Gathering website > at http://www.krnet.org/mvn2008/ , about a third of the way down, for > a spar test conducted at the 2008 Gathering. ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ It's been awhile since I've looked at the plans but I recall the wings have a "design" rating of 7G's at 800 pounds (=5600lbs). Marty Roberts had a KR that weighted 760+ as I recall so his flying weight would have been 1000+ lbs and he claims to have pulled 6 G's (registered on a G meter) without wing failure. At the Red Oak, Iowa Gathering he pulled enough G's that the baggage area structure behind the seat broke loose and interfered with the elevator cables making for an exciting landing. His first words after landing and exiting the KR were "I'm done flying for today. Where is the beer"? I sure do miss Ol' Marty. I've seen several crashed KR's over the years and the wing attach fittings remain intact after the spar caps and structure disintegrate. Built correctly the attach fittings are one of the stronger structures in the wing. They will bend on impact but I have yet to see them or the attach point fail. As always, your results may differ. Don't crash one to test it. Larry Flesner _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org _______________________________________________ Search the KRnet Archives at https://www.mail-archive.com/krnet@list.krnet.org/. Please see LIST RULES and KRnet info at http://www.krnet.org/info.html. see http://list.krnet.org/mailman/listinfo/krnet_list.krnet.org to change options. To UNsubscribe from KRnet, send a message to krnet-le...@list.krnet.org
