This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment ----- Original Message -----=20 From: Erwinspiano@aol.com=20 To: pianotech@ptg.org=20 Sent: November 23, 2002 10:14 PM Subject: Re: Belly rail crown - Why??? In a message dated 11/23/2002 10:00:34 AM Pacific Standard Time, = pianobuilders@olynet.com writes: Del ....Recognizing that by in large most on the list are building rib = crowned boards that retain more of there crown when under load than the = former compression stlye boards. Rib crowned boards being much stiffer = by design, thanks to higher rib radii and stiffer spruce rib material = (formerly sugar pine) and deeper ribs....=20 They don't necessarily start out that way. While the rib-crowned = soundboard certainly has the potential of greater stiffness -- there is = always the option of more and taller ribs -- in practice I'm not sure = they start out all that much different. A well done compression-crowned = soundboard can be quite stiff indeed. But it may not keep that stiffness = very long. It's in holding the long term stiffness that the rib-crowned = soundboard comes out ahead.=20 I see nothing wrong with the beveled rim personally, if my boards = are retaining a good amount crown even when strung I see no reason to = induce another unnecessary possible strain at the edge of the board by = changing all the beveled rastens that come through the shop to a flat = edge. No, I'm not saying you were advocating that either. Well, I don't know that there is all that much wrong with the practice. = I'm mostly just not convinced it does much good.=20 Simply clamping a piece of spruce to a bench and bending it isn't = exactly like the continuos rim of board being glued to a curving rim. = Gluing the board to the rim gives the whole structure a cohesive = stiffness it doesn't have before that.=20 Come on, Dale, you know better than that. Sure, gluing the board to the = rim makes it act like a clamped-edge diaphragm, but wood is still = awfully thin wood and it still bends under load. Especially so when the = load is essentially across-grain and most of it is along the bent side = or at roughly a 45=BA angle as most of it is along the bellyrail and the = straight side. And along the bass curve, well, who cares? Also the board is often thinned down to as little as .250 at the = edges so undue stress once again not desired. The 1 and 1/2 degerees = typically found in the rim joint could as practicallity or compromise be = reduced to half that and this angle would more likely conform to the = residual crown angle after stringing. And, that's pretty much my point. =20 Perhaps petty, lame and faulty thinking but it's mine all mine. Yup. Lame it is. And you can have it. Unless it's already there in which = case I'll have some too. Del ---------------------- multipart/alternative attachment An HTML attachment was scrubbed... URL: https://www.moypiano.com/ptg/pianotech.php/attachments/eb/c0/d0/0b/attachment.htm ---------------------- multipart/alternative attachment--
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