>Ron Nossaman wrote: >> >snip.... Given a panel crowned assembly with a severely dried >> >panel, and one rib crowned with a non dried panel, both to identical >> crowns >> >at room EMC, the one with the higher panel compression level will have the >> >steeper spring rate gradient, and will be stiffer. >> > >> > >> >Now correct me if I am wrong.. but I understand this to mean that a CC >> >board will be stiffer, both unstrung... and increasingly so when >> >downbearing is applied. >> >>Wrong. As we've discussed specifically and often, the RC board can be made >>much stiffer, both unstrung and strung, though the CC board will often have >>a steeper spring rate progression under deflection, at least while the >>crown lasts. >> >Well.. you'll excuse me if I find this directly above in direct conflict >with >"the one with the higher panel compression level will have the steeper >spring rate gradient, and will be stiffer." What do you find that's conflicting, and how can you possibly interpret this to mean that I said compression crowned boards are categorically stiffer than rib crowned? How about the real stuff instead of the game? >and please remember the qualifiers for this example so as to keep it in >context.... it was equal crown at same RH, and further we were to leave >all other compression damage issues aside for a moment. Yes, do remember the qualifiers. Or better yet, go back up and read it again and you will see that the rib crowned board I proposed was assembled without drying the panel at all. While you're at it, re-acquaint yourself with the fact that this is one specific example, put forth to John Hartman indicating that there is more to what determines assembly stiffness than merely cross section and mass of the components, and that identical looking assemblies aren't necessarily equally stiff. That's what I meant to say, that's what I said as far as I'm concerned, and if you think there's anything there (in context) indicating that I said compression crowned boards are categorically stiffer than rib crowned, make your case. Again, the real stuff please. >Real science Ron... means also answering a question in the context it was >given with qualifiers intact... and do me a favour... dispence with the >scolding routine. And FWIW the term "so-called" isnt a derogatory. We're still putting the qualifiers back in my original statement before we go anywhere with yours. Derogatory or not, compression set still exists, and is still real science. >>Yes, if you design the ribs to support the crown without needing panel >>compression to do so, and don't dry the panel to extremes, panel >>compression is no longer a problem. This should start sounding familiar >>about any time now. >Again.. thats not the question I asked.... Or perhaps you are saying that >under no circumstances can the constraint placed by the ribs on the panel >cause problems regardless of climatic conditions ? Of course not. Nothing can survive any conceivable climate condition. If you need that kind of absolute, I'll leave you to it. I sure don't know how to build anything that's utterly indestructible. >I asked if there was a way of contriving a rib such that it was a bit less >constraining to the panel ... as in either compression or tension. And that's the question I answered. Ron N
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