With respect to the strength of the KR2 and KR2S, we had a stress analyst carry out in depth calculations on the whole airframe many years ago.
The stress analyst's report is intellectual property, but I'm sure by now the gent who paid for the calculations shouldn't mind if I release the information. The analysis was carried out to allow the KR2S to be accepted by the UK LAA as an approved design. The KR2 was built under what we call "Grand Father Conditions", meaning 'no one ever carried out any calculations and It was only allowed to be built and flown, because none of them had broken yet!' When the KR2S came along, it was deemed as having sufficient modifications to classify it as a brand new airframe design and therefore required its own individual approval. >From memory, stressing to EASA VLA requirements, which is +6 -4 G and VNA of >175 MPH +10% the airframe was actually quite close in places to not be strong >enough. But it wasn't the spars or longerons or wing attachment brackets, the >weakest part of the aircraft or the part with the lowest safety margin was the >top skin section between the front and rear spar on the stub wings. The one >layer of glass leaves that area susceptible to failure in torsional loading. >Who would have thought it? Hence we have a UK requirement to double up the >skin thickness in that area to two layers of 92/125 bi-directional glass cloth. This skin having the lowest safety margin of the whole airframe is a fact and isn't open to comment or conjecture. We've done the maths. I'll see if I can publish the calculations which prove this fact. So don't worry about any of the structural strengths of the KR2 design at all. It is all perfectly acceptable. Some of it by over 200% The doubling of the top stub skin thickness is recommended and not compulsory. We do it though as that means you can kneel on it or put your foot on it when getting in and out. The calculations are complex and considerable. I'll ask the intellectual owner if I can publish all or just highlight some of the data. All good news. CH. _______________________________________________ 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
