Laminated panels (Farrell)

[Fenton Murray]

So I have often wondered about how drying the panel (and ribs????) down to 3.5% MC prior to rib gluing might affect the integrity of that rib-to-panel glue joint when using a water-based glue (hot hide, Titebond, Bolduc, etc.). That's another reason I find more comfort in gluing ribs on at 6 or 6.5% MC (and not drying ribs).

>Why would this be a factor? Because of concern over a dimensional change in wood after glue up, why would water based be a factor. When the wood takes on ambient moisture it attacks the glue?  Can't be. I don't get it. I never heard that. Wood can be damaged by over drying, but if it is controlled and slowly brought down, that's different. Of course the opposite is true, it can't be good to take out a 3.5 panel where I live (66% average ) and let it freak out in a piano glue up.

 With the panel laminations nearly parallel, it was pretty much like incorporating a rib directly into the panel.

>Wouldn't having the bottom lam 90 to the above lam hold a radius better. Like a rib. Why have them close to parallel? I see what's happening at the tail. At first I thought is was an added panel.

Come on down! We'll mix up a pitcher of margaritas and talk piano belly.......

>I've got a good piano belly.

  ----- Original Message ----- 
  From: Farrell 
  To: Pianotech List 
  Sent: Wednesday, January 30, 2008 3:45 AM
  Subject: Re: Laminated panels (Farrell)


  I've been de-flowered. Looks like a Bosey. 

  Old Bluthner. Straight strung.

  I can't quite get all the details from the pictures. 

  Job security.

  The photo showing the 3 lams makes it look like there all going the same way. I'm assuming they're 90. 

  No. Look at the photo of the tapered tail - the one that you sew the glue line on. Look carefully at the two grain angles. The two outer skins are parallel and the middle lamination is skewed 15 degrees (I think that is about right) clockwise.

  Do you glue them up flat, I mean, you could glue up a crown with no ribs, like the bottom panel would act as ribs. No, that's not right, the grain would have to be opposite the top panel. But, I would think less rib support would be needed if the panel were glued up in a dish. What do I know? 

  Well, sounds like you know what I did. Yes, in the high treble we purposely laminated in a fairly tight radius. We did that because the original rib array - which was dictated that we keep - offered little to zero support for string bearing. With the panel laminations nearly parallel, it was pretty much like incorporating a rib directly into the panel.

  I said something stupid in another post to Jude earlier I have to go correct, about not worrying about shear failure. Then I remembered all those ribs that come loose, now isn't that a shear failure?

  I don't know. Is it? Maybe just a bad glue joint? If you look up on the Franklin glue web site about wood MC and gluing, you will find that they recommend that wood be no lower than 6 or 7 percent MC (just going on recollection - I think it was somewhere around there - no lower for sure). So I have often wondered about how drying the panel (and ribs????) down to 3.5% MC prior to rib gluing might affect the integrity of that rib-to-panel glue joint when using a water-based glue (hot hide, Titebond, Bolduc, etc.). That's another reason I find more comfort in gluing ribs on at 6 or 6.5% MC (and not drying ribs).

  Have fun in the sun, Terry. 

  Hey, I do what I can. Headed out for a 37 mile bike ride this morning. Going to have to brave the frigid 62 degrees outside though. Man, when is it going to warm up????   ;-)

  It looks like you sanded thought to a glue line in one photo, 

  Yes. Tapering in the tail. The otherwise 8mm thick panel was tapered to 5mm at the tail - the center lamination was completely sanded (planed) away in the very tail.

  I can't tell, maybe I'll invite myself over something

  Come on down! We'll mix up a pitcher of margaritas and talk piano belly.......

  Terry Farrell
    ----- Original Message ----- 

    I've been de-flowered. Looks like a Bosey. I can't quite get all the details from the pictures. The photo showing the 3 lams makes it look like there all going the same way. I'm assuming they're 90. Do you glue them up flat, I mean, you could glue up a crown with no ribs, like the bottom panel would act as ribs. No, that's not right, the grain would have to be opposite the top panel. But, I would think less rib support would be needed if the panel were glued up in a dish. What do I know? I said something stupid in another post to Jude earlier I have to go correct, about not worrying about shear failure. Then I remembered all those ribs that come loose, now isn't that a shear failure?
    Have fun in the sun, Terry. It looks like you sanded thought to a glue line in one photo, I can't tell, maybe I'll invite myself over something, I'm good at that. Ask Dale E. or Richard Wheeler.
    Fenton
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