<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"> <HTML><HEAD> <META http-equiv=Content-Type content="text/html; = charset=iso-8859-1"> <META content="MSHTML 6.00.2800.1106" name=GENERATOR> <STYLE></STYLE> </HEAD> <BODY> <DIV>I used West System's "High-Density Filler" and NOT their = colloidal silica - although I'm not sure that it would have made that much = difference. Have you ever cured a big chunk of this stuff? I can put a dent in a = hunk of maple with a hammer, but I would have no such luck with a hunk of = #404-thickened epoxy. It is hard, stiff - man, the stuff is like steel!</DIV> <DIV> </DIV> <DIV>BTW, took weights off my "fitted" one-off one-piece laminated = bridge cap this morning - no movement (whew!). Came out excellent - flat as a = pancake, all joints remained in place, etc. Took a few pictures of bridge root and = cap building, if anyone is interested.</DIV> <DIV> </DIV> <DIV>Terry Farrell</DIV> <DIV> </DIV> <DIV>404 High-Density Filler 404 High-Density filler = is a thickening additive developed for maximum physical properties in = hardware bonding where high-cyclic loads are anticipated. It can also be used for = filleting and gap filling where maximum strength is necessary. Color: off-white.</DIV> <DIV> </DIV> <DIV>406 Colloidal Silica 406 Colloidal Silica is a thickening additive used to control the viscosity of the epoxy and = prevent epoxy runoff in vertical and overhead joints. 406 is a very strong filler that = creates a smooth mixture, ideal for general bonding and filleting. It is also = our most versatile filler. Often used in combination with other fillers, it can = be used to improve the improve strength, abrasion resistance, and consistency of = fairing compounds, resulting in a tougher, smoother surface. Color: off-white. </DIV> <DIV>  </DIV> <DIV>----- Original Message ----- <DIV>From: "gordon stelter" <<A href="mailto:lclgcnp@yahoo.com">lclgcnp@yahoo.com</A>></DIV> <DIV>To: "Pianotech" <<A href="mailto:pianotech@ptg.org">pianotech@ptg.org</A>></DIV> <DIV>Sent: Saturday, March 15, 2003 8:49 AM</DIV> <DIV>Subject: Re: Bridge Cap Thickness</DIV></DIV> <DIV> </DIV>> Terry, >      I don't know = anything about bridge building, but > it seems to me that if you = fill the saw kerfs with > West's mixed with their colloidal silica, you run = the > risk of creating a somewhat vibration absorbing, > = rather than transmitting, bridge root. And, at the dog > leg: a place where transmission might be needed most. >     I would = recommemnd the steam  pre-bending method, > or just dry heat (heat = gun?). Wood bends very nicely > with dry heat, sometimes. > =     But if you do the saw kerf thing, I'd try using > West's straight, = with no silica, for higher density. >      Just a thought. >      BTW---My hat is certainly off = to you as, perhaps, > the most recent victim of the piano = rebuilding > affliction to ever attempt such extensive repairs! >      Best Wishes, >      Thump > > --- Farrell <<A href="mailto:mfarrel2@tampabay.rr.com">mfarrel2@tampabay.rr.com</A>>= wrote: > > Ron O. asked: > > > > "What did = you end up doing at the bridge dog legs? I > > read the posts you = received. Did you steam and press > > the vertical laminates before the final = glue-up? > > Wolfenden suggested this technique with regard = to > > bending the rims also." > > > > My first attempt = was with Tightbond. I found that I > > applied so much clamping = pressure that I distorted > > the bridge (distort is really a very mild = term to > > describe the result of this excercise). I have = been > > using small pieces of wood along the bridge at each > > clamp = to spread out the clamping pressure. I did not > > use the one big caul = method that Ron N. provided a > > picture of. I don't understand how = you can be > > assured of getting proper clamping pressure at = all > > locations. And it seemed like a lot of work to make > > a caul = for each bridge. > > > > So, try number two. Well, first of = all I think that > > I simply was trying to put too much bend into a 32 > > mm thick pile of maple. Never the less, I tried > = > Del's recommendation of notching part way through > > each = lamination at the hard bends with a saw. After > > seeing how much wood I = removed with the saw, I > > immediately thought of the wondrous gap filling > > properties of epoxy. So I wet all the pieces = down > > with unthickened West System epoxy, and filled the > > saw = cuts with a thick mixture of their High Density > > Filler, = assembled and gently clamped to cauls. Just > > enough clamp pressure to get = things into position at > > most locations, and a lot of clamp = pressure at the > > dogleg. Several laminations still cracked - but = no > > big deal with all the epoxy in there (fortunately > > the panel = covers the bottom of the bridge root and > > the cap covers the top - = this bend area is rather > > unsightly). With the light clamp pressure > > (everywhere but the dogleg), I ended up = with > > perfectly smooth big bends in the bridge - ! > > as desired. My = dogleg ended up only 1 or 2 mm short > > of the bend I was shooting = for - it just got > > smoothed out a little. There should be more = than > > ample room to just have the section-end bridge pins > > = ride a little high and low there - should work fine. > > > > = I bought a big roll of 6 mil plastic from Home Depot > > (fairly = thick stuff). Cut a piece a foot longer than > > the bridge and maybe = six or eight inches wide. > > Arranged epoxied laminates on this long = narrow piece > > of plastic. Pull up edges of plastic over sides = of > > bridge and let flop over top. At this stage I could > > = take off my gloves and handle my > > maple-laminate-filled burrito with = extra slow > > setting epoxy sauce with bare hands. The = plastic > > keeps the epoxy off everything - clamps, cauls, you, > > etc., = and keeps in on the bridge laminates - kinda > > makes a neat = little trough that is filled with > > epoxy. The bridge literally sits in a = bath of epoxy > > while the epoxy cures. > > > > I = may try steaming next time. Maybe not. The thing > > with steaming = would be the wait for the maple to > > dry. Now how long is it going to take = to dry with > > clamps and cauls and everything covering the = sides. > > I suppose you could have the top and bottom exposed > > to = the air. I guess I'd have to take some and figure > > its moisture = content, steam it, and then monitor its > > weight to determine the = moisture content to see how > > long it takes to dry. Or maybe you need = to steam > > that thing, clamp it into the desired shape, = and > > have a little heat source below and just toast it > > for a = while. Still though, how long? > > > > Terry Farrell > = >   > > ----- Original Message ----- > = > From: "Ron Overs" <<A href="mailto:sec@overspianos.com.au">sec@overspianos.com.au</A>> = > > To: "Pianotech" <<A href="mailto:pianotech@ptg.org">pianotech@ptg.org</A>> > > = Sent: Friday, March 14, 2003 6:48 PM > > Subject: Re: Bridge Cap Thickness > > > > > > > >At 6:20 PM = -0500 14/3/03, Farrell wrote: > > > >What are the guidelines on = how thick a bridge cap > > should be? And > > > = >why. I've got a new vertically laminated long > > bridge that can be = > > > >trimmed down to any height, and I'm trying to > > = figure out how thick > > > >to make the cap. The cap will be horizontally > > laminated with about > > > = >1.6 mm laminations. Laminations will be epoxied > > together. The = > > > >installation should allow the cap to remain at > = > near full thickness. > > > >It's a bit of a pain making the = laminated cap, > > and that process is > > > >only = complicated by increasing the number of > > laminations. I have > > = > >five laminations now and it adds up to about 8 mm > > = thick. I would > > > >like to not make it any thicker than = optimal, or > > to the point of > > > >diminishing returns. > > > > > > > >Terry = Farrell > > > > > > Terry, > > > > > > 8 mm = of cap thickness will be more than adequate. > > The greatest stress = > > > on the bridge cap wood will be at very top surface > = > of the cap, > > > diminishing further down into the cap. We = are > > currently building our > > > caps 6 mm thick using 6 x = 1mm thick laminations. > > > > > > Good on you for = getting stuck in at the deep end - > > all the best. What > > = > did you end up doing at the bridge dog legs? I > > read the = posts you > > > received. Did you steam and press the = vertical > > laminates before the > > > final glue-up? Wolfenden = suggested this technique > > with regard to > > > bending the = rims also. > > > > > > Ron O. > > > -- = > > > _______________________ > > > > > > = OVERS PIANOS - SYDNEY > > > Grand Piano Manufacturers > > = > > > > Web: <A href="http://overspianos.com.au">http://overspianos.com.au</A> > = > > <A href="mailto:info@overspianos.com.au">mailto:info@overspianos.com.au</A= > > > > _______________________ > > > _______________________________________________ > > > = pianotech list info: > > <A href="https://www.moypiano.com/resources/#archives">http://www.ptg.org= /mailman/listinfo/pianotech</A> > > _______________________________________________ > > = pianotech list info: > <A href="https://www.moypiano.com/resources/#archives">http://www.ptg.org= /mailman/listinfo/pianotech</A> > > > = __________________________________________________ > Do you Yahoo!? > Yahoo! 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