Hi Robin. I think we can just as easily write these comments leaving out all the << tone colour >> as it were. Tends to provoke unecessary flaming... wouldnt you agree ? That said. Perhaps you have hit upon the exact stump my own thinking has bumped into the last couple days. I am slowly finding time to read through Hoadlys book, and find so far that you are correct in your assertion that it deals mostly (if not completely) in uniaxial stresses, and as such I see your point that the books tables can not with out further ado be used to justify some of the claims being made with regard to the more complex stresses going on in our soundboard. In fact... so far I have not found any specific example which remotely resembles our construction. So its going to be fun extrapolating conclusions as I read more. But... to my own specific querry... about ribs supporting crown in a CC board. What I think is bothering me is what appears to be the assertion that the ribs will bend, but not stretch in response to the panel seeking expansion. Reading through Hoadly last nite, I am reminded that the tensil strength of wood along the grain is very great. He gives an example where any attempt to stretch a member along its grain will just see its end parts torn and broken. But that has to do with how it is stressed... which is your uniaxial stress below. What happens in the CC board is a different thing, and I dont find any stress tables or mathamatics that deal with this. Its more like horizontal tension is applied along the entire top surface of the rib. I see no where in Hoadlys book (yet) where this kind of thing is delt with. But ok... if someone can show that the rib resist absolutely any tensioning comming from the panel, and simply bends as I could bend a rib holding it in my two hands.... then I think I would have an easier time seeing the <<no support>> claim. Cheers RicB Robin Hufford wrote: > Hello Richard, > I have not had the time to study all of the RC vs CC posts to > follow the line of thought there but the question of compressive stress > in soundboards and the deleterious, ubiquitous effects so direly > lamented and commented upon in articles by Fandrich in the Journal and > defended vociferously here on the list by Nossman are predicated on > very questionable assumptions, number one and, number two don't appear > to be as generalized a fault as is frequently claimed. Some of the > reasons for these discrepancies, I would suggest, lie in certain > erroneous assumptions made in their analyses which I have intimated > before. > ............. snip -- Richard Brekne RPT, N.P.T.F. UiB, Bergen, Norway mailto:rbrekne@broadpark.no http://home.broadpark.no/~rbrekne/ricmain.html http://www.hf.uib.no/grieg/personer/cv_RB.html
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