IMHO, the only way to get large dimension wood stable is to let it dry in a climate controlled shop for a year or so. I've got about 50 bd-ft of nice hard maple in my shop that was kiln dried, and then has sat in my 45% RH shop for about a year. I just went out last week and picked up over 100 bd-ft of kiln-dried hard maple that I will let sit for a year or more in my shop before I use it. That's one nice thing about laminating. It is stable like a rock. One thing about cutting a solid piece from large solid stock - even if the wood is very dry, there can still be alot of internal stresses - when you cut out a long piece to a pattern, you often find that after it is cut it will spring or twist a bit one way or another. Laminating eliminates all that fuss. Terry Farrell ----- Original Message ----- From: "David Love" <davidlovepianos@earthlink.net> To: "Pianotech" <pianotech@ptg.org> Sent: Friday, March 19, 2004 12:33 AM Subject: Re: Making long bridges > Ron: > > As I ponder the laminated versus solid root choice, can you comment on the > type of wood/grain angle/method of drying and preparing a solid root to get > it stable? > > Thanks. > > David Love > davidlovepianos@earthlink.net > > > > [Original Message] > > From: Ron Nossaman <RNossaman@cox.net> > > To: pianotech <pianotech@ptg.org> > > Date: 3/17/2004 9:36:01 PM > > Subject: Re: Making long bridges > > > > > > >I need a crash course on bridge building (long bridges, bent laminated > > >type). Could use some suggestions on how I might go about getting > > >information, how to make a template, what tools I might need, materials, > > >etc.. Whatever can be offered would be appreciated. > > > > > >David Love > > > > Hi David, > > It's coming up on pumpkin time, and I'm about to collapse for the night, > > but I'll try to do a quick outline for you. > > > > I use a rubbing (paper template) from the original configuration (before > I > > take the strings off) as a point of departure. After re-scaling, I use > that > > template to establish the new speaking lengths, which I use to lay out > the > > new bridge. Once you have the template for the new bridge, you need to > > decide how you are going to build the bridge. You can cut it out from > solid > > stock, joined at the scale breaks to keep the grain running roughly > > parallel to the bridge, or you can laminate it. You can laminate it > > horizontally, putting the joints in each lamination in random places so > the > > strength of the assembly won't be compromised, which works fine. Or you > can > > laminate vertically, which means building a jig of some sort for clamping > > the laminations to the required curve. I've done bridges with continuous > > vertical laminations, but it's a lot more work than should be necessary > for > > a one-off bridge. You need laminations at 2mm or under to make the dogleg > > bends at the struts to maintain a semi-log speaking length progression, > and > > a tremendous amount of clamp pressure. > > > > An easier way to do a vertically laminated bridge root is to use the > > lamination thicknesses to supply the dogleg offset and not have all the > > laminations continuous for the length of the bridge. Terry Ferrell asked > > about this a while back, and it looked like a good idea to me, so I tried > > it. It works very well. Thanks Terry. You just have to build half a jig > to > > accommodate it, clamping the lamination stack against it without needing > a > > caul on the far side. Actually, I used backing strips to spread out clamp > > pressure, but still didn't have to cut out a full caul. Since the core > > laminations don't have to be forced into an extreme bend, it's > considerably > > easier to manage and takes much less clamp pressure. It just takes a > little > > more pondering and planning before the fact. > > > > Cutting out a solid root and putting a cap on top is still easiest, but I > > like laminations. Just not all that bright, I suspect. > > > > That short stack of maple just above the bridge in the photo is the > > laminated cap (1.5mm laminations), waiting to be cut and fitted to the > > root. The bridge root is still rough cut here (hacked, actually), and > will > > be smoothed and contoured before the cap is installed. > > > > bridge laminations.jpg > > > > The laminations in this bridge vary from 2mm to maybe 5 or 6mm. I used > what > > I had lying around from previous projects that added up to the offsets I > > needed for the doglegs. It's a tad over 30mm wide overall. > > > > To do this, you need a way to produce the required laminations - be it a > > table saw or band saw, and (ideally) thickness planer. You need lots of > > clamps (naturally), and scrap(able) lumber for building the jig. You also > > need a glue that is reasonably hard and creep resistant. I use Titebond. > > Realistically the glue used for laminating doesn't need to be able to > hold > > continents together without shifting under billions of PSI. Gluing the > cap > > on top, and the panel on the bottom of the root laminates will > effectively > > insure that nothing is going to slide apart with a reasonably decent glue. > > > > The rest is just the usual bridge work - or you can send me the original > > rubbing and the offset revisions (or?) and we can work something out. > > > > Did I miss anything? > > > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives >
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