<!doctype html public "-//W3C//DTD W3 HTML//EN"> <html><head><style type="text/css"></style><title>Re: Overs laminated soundboard</title></head><body> <blockquote type="cite" cite> <blockquote type="cite" cite>There was some list discussion about sound board presses recently. I</blockquote> <blockquote type="cite" cite>got the first image of my vacuum sound board laminating press</blockquote> <blockquote type="cite" cite>prepared for the web site yesterday. The image below shows the press,</blockquote> <blockquote type="cite" cite>with a test strip of sound board panel and one rib being pressed.</blockquote> <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite>http://overspianos.com.au/vacpress.jpg</blockquote> <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite>The press is 6' x 8'</blockquote> <blockquote type="cite" cite>(1800mm x 2400 mm). The vacuum pump is a Becker 3ph 2 hp unit.</blockquote> <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite>A cutaway of the pump can be seen at;</blockquote> <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite>http://www.becker-international.com/en_z010.html</blockquote> <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite>It can pump 28 cfm when unrestricted and the vacuum can be adjusted</blockquote> <blockquote type="cite" cite>from 1.5 psi to 12 psi. (12 psi will yield a hold-down pressure of</blockquote> <blockquote type="cite" cite>around 0.75 tons/square foot - or 0.8 atmospheres). We use the</blockquote> <blockquote type="cite" cite>minimum 1.5 psi vacuum for gluing the panel to the ribs. The vacuum</blockquote> <blockquote type="cite" cite>diaphragm is a fibreglass reinforced vinyl, fitted to a lightweight</blockquote> <blockquote type="cite" cite>RHS frame which can be lifted on and off the table with ease. The</blockquote> <blockquote type="cite" cite>vacuum is delivered from the pump to the the table using the RHS</blockquote> <blockquote type="cite" cite>frame as a vacuum plenum. A series of holes on the inner edge of the</blockquote> <blockquote type="cite" cite>RHS allow the air to be evacuated from around the perimeter of the</blockquote> <blockquote type="cite" cite>table. Apart from its use as a sound board assembly table, the press</blockquote> <blockquote type="cite" cite>is also very useful for gluing veneer to panels. We will also use it</blockquote> <blockquote type="cite" cite>for the manufacture of the laminated sound board panels which we are</blockquote> <blockquote type="cite" cite>using for our own piano. By the way, the poser in the image is my</blockquote> <blockquote type="cite" cite>Rottweiler 'Harry'. He likes to fossick around the workshop chewing</blockquote> <blockquote type="cite" cite>the odd sound board off-cut.</blockquote> <blockquote type="cite" cite><br></blockquote> <blockquote type="cite" cite>Best,</blockquote> <blockquote type="cite" cite>Ron O.</blockquote> </blockquote> <blockquote type="cite" cite>--<br> <br> Ron,<br> <br> I also meant to comment on this and got this out of the archives as well.  At some point you mentioned, either on this list or to me personally, that you were still undecided about whether to use solid boards or laminated boards in your pianos and that you were going to do some further experimentation.</blockquote> <div><br></div> <div><br></div> <div>Phil,</div> <div>Yes, we discussed this at Reno.</div> <div><br></div> <blockquote type="cite" cite>  Since you mention the vacuum press for making laminated soundboards can I assume you've decided that laminated soundboards are superior to solid boards for giving the results that you want?<br> </blockquote> <blockquote type="cite" cite>Phil Ford</blockquote> <div><br></div> <div>Yes, I now believe the laminated panel is vastly superior in performance to the solid panel. The vacuum press is for gluing up laminated sound board panels, and other panels which we might wish to veneer, and for gluing the rib set to the sound board panel. Since our ribs are flat on the bottom and machined on the top surface to the radius at which we wish to crown the board, the ribs can be set out on the flat surface of the vacuum press with the panel pulled down onto them by the vacuum diaphragm. Using this system, we don't need individual gluing cauls for different pianos, since the rib profile determines the crown and the ribs sit directly on the flat board<font color="#0000FF"> (there is a plywood panel between the ribs and the press, to which the ribs are screwed at the ends - the screwed down section is machined away afterwards when ribs are feathered)</font>. We are using an ordinary short-knap paint roller for applying the glue (Titebond) to the ribs before placing the panel on top. After a little experience you get used to applying just the right amount of glue so that there is no squeeze out. One other matter, which is most important, is that the panel must be lowered directly onto the ribs without slewing the panel sideways during the process. Otherwise the panel will get an unsightly glue smear, and glue will be lost from between the adjacent gluing surfaces. To facilitate lowering the panel vertically onto the ribs, I made up two telescopic guide pins which are fitted into the rib-mounting plywood panel. The two guides are positioned such that the panel practically balances on them. The telescopic guide pins extend upwards 25 mm clear of the rib set<font color="#0000FF"> (with internal piano wire springs of course)</font> when there is no panel weighing them down. After applying glue to the ribs and quickly removing the panel from the conditioning box, it is placed onto the telescopic guide pins, then the weight of the panel compresses the guide pins down until it rests on the rib set. That's it, just placing the diaphragm over the whole 'shabang' and turning the pump on is all that's left to do.</div> <div><br></div> <div>After much consideration, I am now of the view that I probably won't ever use a solid sound board panel. I am not referring here to the 'el-cheapo' laminated panels which are common in the bottom end instruments, which have given laminated panels a bad reputation<font color="#0000FF"> (although one low ender recently gave up laminated panels - which seemed to have some redeeming qualities - in favour of traditional solid panels, which like so many other traditional solid panels, just go flat even before the piano makes it to the showroom)</font>. I am referring to carefully built laminated panels, where each laminate is constructed as if it were to be a first quality solid sound board panel, but 1/3 the nominal thickness, ie. properly quartered boards shot and joined properly with no air gaps. Three of these 2.5 mm thick panels make up one laminated panel<font color="#0000FF"> (we sand the middle laminate to 2.5 and the outers to 2.8 - this allows for some final sanding after they are glued together)</font>.</div> <div><br></div> <div>There are several compelling reasons why I believe the laminated panel is superior to the solid version. Firstly, the solid panel is more prone to self destruct with the hygroscopic changes which encourage compression/tension set. Have you ever wondered why some sound boards check in certain boards of the panel, while other boards in the same panel remain without cracks? Well this problem is probably due to the variation in strength and density of the various boards which make up a panel. When the panel is subjected to humidity variations it tries to expand or contract. When it tries to expand the weaker boards in the panel will tend to crush or compression set more quickly so that when the panel dehydrates under drier conditions, it will be the weaker and lighter boards which tend to be the first to to be pulled apart. If the panel is cross laminated, the cross laminated long grain will force the panel to share the expansion and contraction more evenly. This is one reason why you just don't see compression ridges in a properly laminated panel, and it is also the reason why cracks in a laminated panel are almost unheard of.</div> <div><br></div> <div>So the laminated panel, with cross grain which is much less prone to change dimension with hygroscopic variations, will result in a panel which is more stable regarding tuning stability. After having some experience with laminated panels, and after finding that there is almost no shrinkage of the panel when dried down to 6% moisture content, I would doubt if CC boards could be made using laminated panels, since to achieve any noticeable crown, one would almost certainly have to crown the ribs.</div> <div><br></div> <div>We are running the top and bottom laminates in the same direction as for a traditional solid panel, ie. along the line of the long bridge, with the middle laminate at 90 degrees and parallel to the sound board ribs. While some might see this as a disadvantage, since 1/3 of the panel thickness is oriented with the ribs, I don't see any problems associated with it. Certainly the laminated panel is somewhat more flexible along the line of the long bridge, and stiffer parallel to the ribs, but the long bridge if adequately dimensioned will be more than capable of ensuring the whole assembly maintains its togetherness. With a rib crowned board, the most important job the panel has do is to ensure that air doesn't leak past the ribs when they go up and down. The laminated panel will do this without encouraging variations in crown as moisture levels change.</div> <div><br></div> <div>Ron O.</div> <x-sigsep><pre>-- </pre></x-sigsep> <div><font size="-2" color="#000000"><br> </font><font face="Times New Roman" size="+1" color="#0000FF"><b>OVERS PIANOS - SYDNEY</b></font></div> <div><font color="#000000"><i>    </i></font><font color="#0000FF"><i> Grand Piano Manufacturers</i></font><font color="#000000"><br>      _______________________</font></div> <div><font size="-2" color="#000000"><br> </font><font color="#000000">Web http://overspianos.com.au<br> mailto:ron@overspianos.com.au<br>      _______________________</font></div> </body> </html>