I’m pretty sure that the Boesendorfer soundboard is at least 10 mm if not 11 thick-I’ll have to look more carefully at my next appointment with one. Interestingly, the grain angle on those boards is something like 35 degrees. The potential negative effect on the bass from the increased thickness, which undoubtedly helps in the treble section, seems to be offset by a grain angle which more parallels the bass bridge. I’ve not taken one apart to see how they treat panel thinning behind the bass bridge. David Love www.davidlovepianos.com From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Dale Erwin Sent: Thursday, August 05, 2010 8:02 AM To: pianotech at ptg.org Subject: Re: [pianotech] rcs design considerations That is a really thick panel. 11 mm is well over 400. The only panels I've witnessed this thick have been in older Masons BB with .400 eastern spruce boards. I agree with Davids choice of thickness for Sitka boards in Steinways. Even in a D... 9 ish mm in the middle regions is plenty. By the way if you see enough Steinway soundboards come out you will soon learn that they had no hard and fast spec. on thickness Ie. A model B boards thickness can vary.... as much as .375 and as little as .320. Some Ds are as much as .390 and as little as .340. Pretty big range. I think it just depended on what came out of the panel sander and if smitty was keeping his eye on the ball that day. By the way Gene if you are rib crowning with a cut crown method allow the ribs to be a bit higher in the middle as they will be thinner towards the end and if you don't allow for some extra rib height that number will naturally reduce overall. Dale S. Erwin www.Erwinspiano.com Ronsen Piano hammers Sales,custom prep and tech support 209-577-8397 209-985-0990 -----Original Message----- From: David Love <davidlovepianos at comcast.net> To: pianotech at ptg.org Sent: Thu, Aug 5, 2010 7:38 am Subject: Re: [pianotech] rcs design considerations Actually on the Boes 9’ piano the panel thickness might even be more like 11 mm, I don’t recall exactly. David Love <http://www.davidlovepianos.com> www.davidlovepianos.com From: David Love [ <mailto:davidlovepianos at comcast.net?> mailto:davidlovepianos at comcast.net] Sent: Thursday, August 05, 2010 7:28 AM To: ' <mailto:pianotech at ptg.org> pianotech at ptg.org' Subject: RE: [pianotech] rcs design considerations Boesendorfer, for example, employs a panel thickness of about 10 mm instead of 9 for Steinway for that sized piano (though they also use a less acute grain angle). I typically use 8 mm for smaller Steinways and 9 mm for larger ones. So the question was if you were doing a full RC&S design but the only difference was a soft rim what would you do differently. I’d probably just increase the panel thickness some. I don’t think I’d change the rib dimensions or the other design elements. Ron mentioned beefing up the rim which in effect then changes the rim mass in order to be able to use what would be the same basic design. That’s another approach. I think the question though is given a soft wood rim without altering the mass what changes must be made to accommodate the difference. So what happens then in a soft wood rim that’s different from a hardwood rim and what do you need to do to compensate. Rate of energy loss is one difference. But unless you are going to modify the rim there really are only a couple of choices: change the panel thickness and/or grain angle, change the rib dimensions (RC&S design so you can’t change the EMC at glue up). Bridge height might also be a consideration. I’d probably increase the panel thickness and reconsider the grain angle. David Love <http://www.davidlovepianos.com> www.davidlovepianos.com From: Dale Erwin [ <mailto:erwinspiano at aol.com?> mailto:erwinspiano at aol.com] Sent: Wednesday, August 04, 2010 10:00 PM To: <mailto:davidlovepianos at comcast.net> davidlovepianos at comcast.net; <mailto:pianotech at ptg.org> pianotech at ptg.org Subject: Re: [pianotech] rcs design considerations Thicker than what and how thick is always the question. Thickness is somewhat wood species dependent and any mans best guess. But iahve my opinions about this Gene are you confused yet? Dale S. Erwin <http://www.Erwinspiano.com> www.Erwinspiano.com Ronsen Piano hammers Sales,custom prep and tech support 209-577-8397 209-985-0990 -----Original Message----- From: David Love < <mailto:davidlovepianos at comcast.net> davidlovepianos at comcast.net> To: <mailto:pianotech at ptg.org> pianotech at ptg.org Sent: Wed, Aug 4, 2010 9:28 pm Subject: Re: [pianotech] rcs design considerations Assuming same scale tensions I would probably use a slightly thicker panel. I don't think I'd alter the rib dimensions. David Love <http://www.davidlovepianos.com> www.davidlovepianos.com _____ From: "Gene Nelson" < <mailto:nelsong at intune88.com> nelsong at intune88.com> Sender: <mailto:pianotech-bounces at ptg.org> pianotech-bounces at ptg.org Date: Wed, 4 Aug 2010 21:15:19 -0700 To: < <mailto:pianotech at ptg.org> pianotech at ptg.org> ReplyTo: <mailto:pianotech at ptg.org> pianotech at ptg.org Subject: [pianotech] rcs design considerations Hello list, Just curious: For a typical radius crowned design for a 9ft grand that would go into a Steinway - how would you alter the design if the piano had softwood rim? Would you alter the design? Gene -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://ptg.org/pipermail/pianotech.php/attachments/20100805/03dfcdaf/attachment.htm>
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