Hi John, Comments interspersed.
Regards, WRB -- On Mar 6, 2010, at 21:13, John Cooper wrote: > 10% is a commonly used guideline to determine whether a procedure has > compromised the strength of a structure. For example, if you are > removing corrosion from a skin, a 10% or less reduction in thickness is > generally considered acceptable. > > The statement "the cross-sectional AREA of the top spar cap was reduced > by 10%" means that if you took a section through the top spar cap at > the > center of the hole, the diameter of the hole was 10% of the total > section, e.g. a 1/8" hole in a 1.25" section. Makes sense. Thanks for sharing. > By making that statement > they seem to imply that the hole was not large enough to significantly > affect the strength of the structure relative to the design > specifications. > We are singing out of the same song book here. There are four 1/4" holes in the upper spar cap on each side of the cabin where the fuselage bolts to the spar. It should then surprise no one that a single smaller hole should not significantly affect spar design strength. > I find it interesting that they did not say "less than > 10%" as I find it difficult to believe it was exactly 10%, and if it > was > more they certainly would have said so. > > -- > John > Skyport East > www.skyportservices.net
