Darryl Keil Last Activity 2025-02-12 2:48 PM
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mike mcnerney

Posts: 87

Joined: 2003-07-17
Location: ottawa ontario

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Subject : plywood guitar sides & backs
Posted : 2008-08-22 7:47 PM
Post #34865
I am going to build a few guitars this winter & am quite keen on attempting to make plywoods sides & backs. thickness seem to be some where around .090. I have only found a few builders on the luthiers forum who have tried it. Maybe someone has perfected it but I haven't found them yet. I am curious how folks on this forum would approach it.
I am going to try a 3 ply with 1/16 in the center perpendicular to the face veneers and one going parallel. I have QS fir, cherry, walnut with EI rosewood face veneers, probably with uni bond. I might experiment with pva for the backs because they eventually get pushed to a gentle dome shape, not flat. I'm wondering if I need to allow for springback.
So many possibilites & questions, all coments appreciated.
Mike McNerney ottawa


 
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Don Stephan

Posts: 825

Joined: 2003-07-18
Location: Cincinnati, Ohio

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Subject : RE: plywood guitar sides & backs
Posted : 2008-08-24 11:40 AM
Post #34869 - In reply to #34865
Probably quite a bit of experimentation will be needed to answer your questions, which might be why few have tried. How are the sides and back traditionally formed? If steam bending is required to make the final shape, you likely would not be able to use that technique after pressing up a 3-ply. If the plywood adhesive is used to hold the assembly to what would seem to be rather severe bends, the inherent stresses in the plywood sides might affect the overall sound of the resulting guitar.

Do the top and bottom traditionally hold the sides to final shape, or are the sides at final shape before assembly? Atypical stresses on the otp and bottom might change the overall sound of the finished guitar.

Finally, how is the domed shape of the bottom traditionally achieved? Seems like there has to be some stretching/compressing of the wood.


 
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mike mcnerney

Posts: 87

Joined: 2003-07-17
Location: ottawa ontario

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Subject : RE: plywood guitar sides & backs
Posted : 2008-08-25 9:41 AM
Post #34874 - In reply to #34869
thanks Don & Darryl,
I will be pre bending all veneers the traditional way, "hot pipe bending"
then pressing in the bag. There is a video on you tube showing this,solid wood, if you're interested. The sound issue is open to endless debate by luthiers & all, hence I'm not dealing with it at this time. they are bent to their final shape & the top & back are domed by curved bracing.
My gut tells me a five ply will work better, but I am still going to try the 3 ply. I am aware there will be numerous trials, which I will be starting this fall.
Darryl, there was the beginnings of a similar thread in nov, 2000 by someone named Brian & one response from Tim Taylor who said he could be emailed. I would like to email Tim but don't see how to do it, can you help?
Mike McNerney, ottawa


 
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Darryl Keil

Posts: 1454

Joined: 2003-05-22
Location: Maine

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Subject : RE: plywood guitar sides & backs
Posted : 2008-08-25 5:03 PM
Post #34875 - In reply to #34874
Mike,

Below everyones name on a post is a user profile. Click on it, if they have put in their email address, it will be listed there. Other than that I dont know how you would get in touch with him.

Darryl Keil


 
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Darryl Keil

Posts: 1454

Joined: 2003-05-22
Location: Maine

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Subject : RE: plywood guitar sides & backs
Posted : 2008-08-24 8:20 PM
Post #34873 - In reply to #34865
Mike,

Knowing the amount of spring back is often hard to determine until you try. I will say this, a three ply lamination is only two glue lines which often means some spring back. If after your test you do get a fair amount of spring back consider wetting and pre-bending the individual laminations so that they take the shape as much as possible before you glue them together. This should keep your spring back to a very small amount.

Darryl Keil
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