Folks, R. Human write his below down. For 5.7 g ultimate (FAR 23 for normal catagory) the gross weight allowable is 1035 lbs (plus the weight of the wings) for My KR with 100 lbs of wing the gross weight should not exceed 1135 lbs. (ultimate is the driving factor here...limit load works out to 4.2 g)
It is maybey an stupid question but we made leadingedge fuel tanks. Can I have a bigger gross weight now?? This because the airframe should not have to carry the fuel tanks? Stef Stef and Ted are building the KR-2S see http://www.masttotaalconcept.nl/kr2 ________________________________ Van: krnet-boun...@mylist.net namens R. Human Verzonden: do 18-11-2010 23:59 Aan: 'KRnet' Onderwerp: RE: KR> 1300# gross weight question Craig wrote: >No doubt about it I am going to be right near 1300# full fuel and the wife with 30# baggage if I can get the empty weight at 764# like Marks plane. The question is can the RAF48 stock wingspan handle that. < You guys are really scaring me by ignoring the part gross weight plays on the design of an aircraft, it's not just a matter of wing loading but the ultimate strength of the aircraft. A number of years ago this was posted (look in the archives). Peter Hudson <phud...@iwvisp.com> Tuesday, October 07, 1997 11:10 PM hi gang, I've just had some luck on the gross weight issue. While talking about it with some work mates at lunch I found someone with an OLD edition of Bruhn (for the non engineer types Bruhn is the bible of aircraft structural analysis). In fact its a 1949 edition so it still had the section on wood spar design/analysis. The good news bit is that the forest products lab had done extensive testing on exactly our type of box spar for spruce. There are different allowables for the spruce in spars based on some shape factors of the spar caps and webs. The values are stronger than test specimens in pure compression (due to the nonlinearity of wood at failure depending somewhat on the shape) FOR THE KR-2 SPAR the allowables for ultimate compressive rupture are 6670 PSI and for the elastic limit is 4900 PSI. Not counting any contribution from the rear spar that gives the following limits. For 5.7 g ultimate (FAR 23 for normal catagory) the gross weight allowable is 1035 lbs (plus the weight of the wings) for My KR with 100 lbs of wing the gross weight should not exceed 1135 lbs. (ultimate is the driving factor here...limit load works out to 4.2 g) So I plan to use 1100 lbs as my gross weight, leave my spar stock and I'll feel good about it. (I trust Bruhn implicity!) I'll write again with an appropriate set of V-N diagram data soon based on that gross weight and strength. -Peter Hudson- My suggestion is that you do some serious soul searching about what you are attempting to build or at the least get some professional help from a structural engineer! _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html _______________________________________ Search the KRnet Archives at http://www.maddyhome.com/krsrch/index.jsp to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net please see other KRnet info at http://www.krnet.org/info.html
