Official Luthiers Forum!

[QUOTE=Alain Desforges] Ohhhh!!!! Now I get it... the holes don't go all the way through the spruce... So the holes are facing the redwood... Hence the 'double top' designation... I was wondering why it wasn't called a 'triple top'?!

'I see' says the blind man, as he falls down the stairs... [/QUOTE]

You got it!! CORRECTO!!

_________________
Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

This is similar to the approach that Frederich Holtier uses on his classicals, in addition to his use of "standard" nomex double top construction techniques. see http://www.holtierluthier.com/models.htm
I played one of his wood double top instruments and was extremely impressed with its power, dynamic range, and focus.

[QUOTE=Hesh1956] How do they laminate the two tops when Nomex is used in between them?[/QUOTE]

Hesh, I've been using a vacuum press for it.

_________________
Jim Watts
http://jameswattsguitars.com

Peter,

The theory in double top construction is to get the mass reduced while maintaining the same 'stiffness' or compliance. The energy of the strings driving the top doesn't change. If the top becomes 'stiffer'/less compliant then it takes more energy to drive it and make it deflect.

A good reverse analogy is a building truss. It can be made very light (mass) but the depth of the truss determines just how much weight it can carry and still maintain a minimal deflection. The deeper it is (height or thickness if you will) the less it will deflect and the 'stiffer' / less compliant it will be.

You should measure the deflection of a 'normal' top (takes some time and empirical data to establish) and then you will have a baseline by which to model your ideal double-top stiffness characteristics. At a minimum you can compare one of your 'normal' guitar tops to the double-top you've built.

Take a look at David Hurd's excellent web pages dealing with some of the physical issues in lutherie.

   http://www.ukuleles.com/Technology/statmea s1.html

   http://www.ukuleles.com/Technology/complia nce.html

He has written an excellent book which will help develelop an understanding of how these principles affect what you build.

PetePeter J39033.44375

_________________
Peter

[QUOTE=Peter J] Peter,

A good reverse analogy is a building truss. It can be made very light (mass) but the depth of the truss determines just how much weight it can carry and still maintain a minimal deflection. The deeper it is (height or thickness if you will) the less it will deflect and the 'stiffer' / less compliant it will be.

Pete[/QUOTE]

This is the idea behind Cannondale bicycle frames. The aluminum tubes are 3 times the diameter of a standard steel frame, yet the Cannondale is much lighter and much stiffer.

_________________
"Building guitars looks hard, but it's actually much harder than it looks." Tom Buck

Peter
I applaud your effort to try something new.
I hope it proves to be a success.
I am curious if you recorded weight of this
double top. It would be nice to know how
much lighter it is. You know, than a solid top.

Tom

_________________
http://www.moriciguitar.com

[QUOTE=Tom Morici] Peter
I applaud your effort to try something new.
I hope it proves to be a success.
I am curious if you recorded weight of this
double top. It would be nice to know how
much lighter it is. You know, than a solid top.

Tom[/QUOTE]

Thanks Tom, unfortunately I forgot to weight it... it is a great idea. I guess there is always next time...

_________________
Peter M.
Cornerstone Guitars
http://www.cornerstoneukes.com

Peter
Thanks for the response, I have forgot to weigh parts
a few times myself. I should of mentioned how nice
that box looks, great choice on the materials.
Keep up the good work and May God Bless!

Tom

_________________
http://www.moriciguitar.com