This is a multi-part message in MIME format. ---------------------- multipart/alternative attachment 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! 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. Terry Farrell 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. 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.=20 =20 ----- Original Message -----=20 From: "gordon stelter" <lclgcnp@yahoo.com> To: "Pianotech" <pianotech@ptg.org> Sent: Saturday, March 15, 2003 8:49 AM Subject: Re: Bridge Cap Thickness > 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.=20 > 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 >=20 > --- Farrell <mfarrel2@tampabay.rr.com> wrote: > > Ron O. asked: > >=20 > > "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." > >=20 > > 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. > >=20 > > 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. > >=20 > > 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. > >=20 > > 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? > >=20 > > Terry Farrell > > =20 > > ----- Original Message -----=20 > > From: "Ron Overs" <sec@overspianos.com.au> > > To: "Pianotech" <pianotech@ptg.org> > > Sent: Friday, March 14, 2003 6:48 PM > > Subject: Re: Bridge Cap Thickness > >=20 > >=20 > > > >At 6:20 PM -0500 14/3/03, Farrell wrote: > > > >What are the guidelines on how thick a bridge cap > > should be? And=20 > > > >why. I've got a new vertically laminated long > > bridge that can be=20 > > > >trimmed down to any height, and I'm trying to > > figure out how thick=20 > > > >to make the cap. The cap will be horizontally > > laminated with about=20 > > > >1.6 mm laminations. Laminations will be epoxied > > together. The=20 > > > >installation should allow the cap to remain at > > near full thickness.=20 > > > >It's a bit of a pain making the laminated cap, > > and that process is=20 > > > >only complicated by increasing the number of > > laminations. I have=20 > > > >five laminations now and it adds up to about 8 mm > > thick. I would=20 > > > >like to not make it any thicker than optimal, or > > to the point of=20 > > > >diminishing returns. > > > > > > > >Terry Farrell > > >=20 > > > Terry, > > >=20 > > > 8 mm of cap thickness will be more than adequate. > > The greatest stress=20 > > > on the bridge cap wood will be at very top surface > > of the cap,=20 > > > diminishing further down into the cap. We are > > currently building our=20 > > > caps 6 mm thick using 6 x 1mm thick laminations. > > >=20 > > > Good on you for getting stuck in at the deep end - > > all the best. What=20 > > > did you end up doing at the bridge dog legs? I > > read the posts you=20 > > > received. Did you steam and press the vertical > > laminates before the=20 > > > final glue-up? Wolfenden suggested this technique > > with regard to=20 > > > bending the rims also. > > >=20 > > > Ron O. > > > --=20 > > > _______________________ > > >=20 > > > OVERS PIANOS - SYDNEY > > > Grand Piano Manufacturers > > >=20 > > > Web: http://overspianos.com.au > > > mailto:info@overspianos.com.au > > > _______________________ > > > _______________________________________________ > > > pianotech list info: > > https://www.moypiano.com/resources/#archives > > _______________________________________________ > > pianotech list info: > https://www.moypiano.com/resources/#archives >=20 >=20 > __________________________________________________ > Do you Yahoo!? > Yahoo! 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