I'm not sure if he's monitoring this list, I'll forward the request to him, maybe he will send some pictures. Dave Davis, RPT -----Original Message----- From: "David Love" <davidlovepianos at comcast.net> Sender: pianotech-bounces at ptg.org Date: Tue, 20 Jul 2010 06:54:48 To: <pianotech at ptg.org> Reply-To: pianotech at ptg.org Subject: Re: [pianotech] soundboard grain angle vs "faux"stiffness I'd be curious what the set up for that particular procedure looks like. David Love www.davidlovepianos.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of Dave Davis Sent: Tuesday, July 20, 2010 6:52 AM To: pianotech at ptg.org Subject: Re: [pianotech] soundboard grain angle vs "faux"stiffness David, Del has a power chisel that works well for removing material in odd places. It would work well to bevel the inner rim in a controlled manner, with minimal effort. Dave Davis, RPT -----Original Message----- From: "David Love" <davidlovepianos at comcast.net> Sender: pianotech-bounces at ptg.org Date: Tue, 20 Jul 2010 06:44:18 To: <pianotech at ptg.org> Reply-To: pianotech at ptg.org Subject: Re: [pianotech] soundboard grain angle vs "faux"stiffness John: Re your #2. Many of the older Steinway pianos have a much wider inner rim shelf. In the later models it is cut away some to leave a much narrower platform which moves the bridge a bit farther away from the inner rim and must, it seems to me, have some benefits not only in the high treble but in the lower end of the piano as well. I have considered taking material off these areas (for example, I have an older Steinway O in the shop that has the wider shelf) but have not figured out a clean way to do it. It would be easy with a router were the outer rim not yet attached but with the bracing configuration and the outer rim in place a router won't quite do the job. Have you (or others) a method for doing that? David Love www.davidlovepianos.com -----Original Message----- From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf Of John Delacour Sent: Thursday, July 15, 2010 12:00 PM To: pianotech at ptg.org Subject: Re: [pianotech] soundboard grain angle vs "faux"stiffness At 01:23 -0400 15/7/10, Dale Erwin wrote: >... Did the attached pictures help answer any questions. Hello Dale, Looking at your pictures of the board, I'm curious to know what decided you to design the high treble like that and what engineering or acoustic principles led you to the splayed rib pattern. The way I understand things a spruce board is adequately stiff along the grain and the main purpose of the ribs is to bring the stiffness of the board across the grain to a similar degree of stiffness in order to achieve something like an orthotropic plate. 1. Your longer ribs perform this function but the further you get towards the treble the more the ribs are reinforcing the stiffness of the board along the grain, where it is not needed while supplying less and less stiffness across the grain, where it is needed. In order to increase the stiffness to a determined degree at the treble end of the board you are bound therefore to use a heavier rib than would be needed if the ribs were at a right angle to the grain, you are needlessly stiffening the board in the direction of the grain and you are adding more mass than yould otherwise be needed. 2. Your masking of the edge of the board for the glue suggests that a full inch or more of the right hand end of the board is glued down to the inner rim, which brings the right-hand boundary of the sounding board say 20 mm closer to the end of the bridge than it would be if the inner rim were cut away to give a glue line 6 mm wide instead of the full width used for the rest of the perimeter. In other words a significant proportion of the board's area in this region is disabled when it could be used to advantage for the vibrations received from the highest strings. A second effect of this arrangement is that the board is stiffened, which brings me to... 3. To my eye, not only is your highest rib doing work in an unnecessary direction but it is supplying stiffness, together with the rim support, to the unsupported area of board above it, which in my design would have another rib. In other words, where you have one rib at 55 degrees to the grain, I would have two lesser ribs at a right angle to the grain. These ideas of mine are not some new-fangled approach I've dreamt up but can be seen applied in numerous pianos that have an excellent treble without even the aid of tuned partials or even capo bars -- how they might sound with these additions is quite a thrilling thought. You might answer the splaying question by saying you want the bars roughly at a right angle to the long bridge, in which case I would ask "Why?". As ever, the Devil's advocate! -- JD
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