Epoxy Bass Bridge Repair

[Gregor _]

Sorry, but I still don´t understand that statement. A thin layer of Epoxy to remain in the joint? Of which joint you are talking about: the joint of Epoxy and wood?

What does it mean for practice? Should I first apply a little bit of Epoxy to the wood, let it become hard, and then apply the Epoxy with the filler?

Gregor

From: mfarrel2 at tampabay.rr.com
To: pianotech at ptg.org
Subject: Re: Epoxy Bass Bridge Repair
Date: Fri, 9 May 2008 15:57:38 -0400










Some adhesives like Titebond are not very good at 
filling gaps. They perform best with a tight-fitting joint and minimal glue left 
in the joint. Epoxy and many other adhesives is gap filling and you want at 
least a thin layer of epoxy to remain in the joint - doesn't have to be much, 
but you don't want a perfect fitting joint and then apply high clamping 
pressure. With epoxy you want a loose fitting joint (or roughened up surfaces) 
and minimal clamping pressure - clamp pressure is not to "clamp" as such, but 
rather simply to hold pieces in place.
 
Terry Farrell

  ----- Original Message ----- 
  From: 
  Gregor 
  _ 
  To: Pianotech List 
  Sent: Friday, May 09, 2008 11:49 AM
  Subject: RE: Epoxy Bass Bridge 
  Repair
  
Terry,

what do you 
  mean by "you need to leave 
  some epoxy in the gap. You don’t want to epoxy-starve 
  the joint."?

I found a source for Western System Epoxy handy repair set 
  including that filler here in Germany. Good to know, I will try it perhaps one 
  day, but not with that Kawai. I told the customer to ask a collegue who has 7 
  pianotechs working for his shop: 4 on master level, 2 with certificate of 
  apprenticeship and one apprentice, and they have a huge workshop. I don´t do 
  repairs with woodwork anymore, just tuning, small repairs and selling pianos. 
  But in this case it probably would have been easier to order a new brigde from 
  Kawai which fits perfectly without any adjusting: just installing and it 
  fits.

Gregor


  
    
    From: mfarrel2 at tampabay.rr.com
To: pianotech at ptg.org
Subject: Re: 
    Epoxy Bass Bridge Repair
Date: Fri, 9 May 2008 08:57:04 -0400


    
    

    Epoxy repairs for a situation as 
    you describe can yield very good results. Sometimes the crack opens up a fair bit – you’ll want to clamp it 
    back into position – not to clamp in the 
    traditional sense, but rather to simply position the parts in their original orientation – you need to leave some 
    epoxy in the gap. You don’t want to 
    epoxy-starve the joint.
 
I use West System epoxy 
    resin, hardeners and fillers:
www.westsystem.com My 
    favorite for a cracked bridge is #404 High-Density Filler and using the West System two-step bonding 
    procedure described on the West System web site. The following is from the 
    West System web site:
 
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.
 
You can either push the 
    bridge pins into the uncured epoxy, tidy up and be done with it, or, 
    for a neater, more exacting job, you can epoxy the gap and then drill bridge 
    pin holes after the epoxy hardens. I have found that if cosmetic 
    considerations are not paramount, I apply the epoxy, clamp together until 
    the wood is close to original dimension, clean off epoxy squeeze out 
    (acetone) - at that point you will be able to see the outline of the 
    original pin holes - push pins in place - the wood will have been drawn 
    together enough to hold the pin in its original position - and then level 
    off and clean up the little bit of epoxy that squeezes out of the holes as 
    you push the pin in place. Wait a day or two for the epoxy to completely 
    cure, go back and install bass strings.
 
I've done this repair 
    numerous times with great success.
 
And of course, on a nicer 
    piano where the budget allows, new bridge and/or new cap is 
    preferred.
 
Terry Farrell

    
      ----- 
      Original Message ----- 
      From: 
      Gregor _ 
      To: 
      pianotech at ptg.org 
      Sent: 
      Friday, May 09, 2008 5:13 AM
      Subject: 
      Epoxy Bass Bridge Repair
      
I crawled the archieves but I did not really find what I 
      was looking for: does Epoxy work even for bigger gaps?

I wanted to 
      tune a Kawai CE-11 upright yesterday but the bass bridge looked horrible: 
      a long gap which affected 9 notes. The gap started at the upper pin row 
      and the pins were vertical. Some strings rattled at the pins. The gap 
      expanded up to 4 mm above the upper pin row. I did not try but I could 
      imagine that I could have pulled out some pins without using 
      pliers.

First at all: I never worked with Epoxy. My first thought 
      was to pull out the pins, fill the gap with epoxy and drill new holes for 
      new pins. Could that work or is such a gap too much for Epoxy? The bridge 
      is made of one piece of wood, no cap.

I was shocked about such a 
      gap in a Kawai from 1992 (no grey market import): no floor heating, no air 
      con and no heater near by the piano. And I don´t live in an area with huge 
      differences in the climate. Very strange. That damage is a pitty because 
      everything else in this piano was in a pretty good condition. But making a 
      new bridge would be definitely too expensive including transports from the 
      second floor into a workshop and back to the 
      customer.

Gregor


      
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