Bandsaw Accident with Archtop!

[CyborgCNC]

Well..not really...

More like a solidworks accident chopping the body in half! LOL!!

How is that for accurate Top and Bottom surfaces?

[CarveOne]

Looks really good. I assume that you can repair the damage with a little pixel adhesive.

CarveOne

[CyborgCNC]

I think I will model some "virtual Glue" and use that!

LOL!

[packrat]

@CyborgCNC - what do you think of the idea of using a thick piece of sitka and machining the top and all of the braces as one piece, for a acoustic?

[CyborgCNC]

I think that would be a VERY INTERESTING experiment...it is really very easy to do as well...just some simple geometry on the top inside surface, and you are done...(then you extrude from the inside surface)

I would however, leave the braces a little larger than what I would think the final thickness would be....so you machine them in one part, but then, you use a small plane to bring them down to a point where the tap voice (by tap tuning) of the instrument would sound good to you....this way you do the final tuning and voicing in a traditional method, but you have a perfectly fitted brace(s), no glue, and perfect contact with the surface....

I LIKE IT!!!

AWESOME suggestion and idea!

[packrat]

Thanks, just one of the ideas I've been playing with. Like you said, trim after the top surface was finished. With all the wood being one piece and no glue joint between the top and braces it "should" transfer vibrations to the whole top.
cary

[CarveOne]

The pieces that you would normally pre-cut, glue in place, then trim would normally be straight grain wood that is placed at angles to the grain of the top itself. This provides a certain amount of stiffness to the top. I think if Packrat tries this integral braces idea, it would not be as stiff because the grain now runs at diagonal angles to the length of the braces, almost certainly changing the shape of the braces required to achieve the same tonal quality. There's also the increased likelihood that that the top will change shape over the years more so than with the traditional braces designs.

For sure, it would be interesting to see what happens.

CarveOne
(Who knows nothing significant about making or playing these things but is interested)

[CyborgCNC]

So you believe that the grain itself, will have an effect on the stiffness, which I am sure it will, and you bring yet another interesting point.....

For the same reason, it will also have an effect on sound, since the way the the grain is structured, and integrated into the top, it will allow it to vibrate more free I would think....and the contact is basically perfect, so from a stress prespective quite different than gluing a formed brace....

Now this is getting VERY interesting!

Here is the model, with the braces, a bit over sized for final tuning....did some test tool paths in Mastercam, and they machine very well!

[packrat]

With a thick enough piece of wood to begin with, you could even incorporate the kerfed linings into the top. With out the kerfs, that is. Just glue the sides to a totally one piece top.

[CarveOne]

I think packrat's ideas have merit as something that can be done only with CNC equipment and would speed up production by eliminating much of the hand work. It would be worth building a couple of different style guitars this way and trying to quantify whether there is an improvement in the design and/or long term stability to be gained. I have no doubt that the instruments will be playable, but will they be heard as notably good sounding instruments?

I agree that the integral braces should transfer sound vibrations better since it is done through longer grain fibers that are all part of the top.

Maybe FEA evaluations can give a picture of what happens with the stresses and how they get distributed around the top for both the old method and packrat's CNC method of construction.

CarveOne

[CyborgCNC]

I Agree....The CNC process allows us to do these things quite easily...

I also wonder that is Solidworks simulation can be used to determine some of those stress points etc to the top....I have not played much with simulation in the software, but maybe it is about time to start...

I think the next top I machine, will have the integral braces....

Has anyone used say a "spectrum analyzer" to get some sort of digital data to tap tuning? In other words, I am looking to get a graph of sorts, to what the tune sounds like with integral braces vs glued braces..just for laughs and giggles....

We shall see...

[keebler303]

Cyborg

With a bit of software, you can use the microphone input on your computer as a pseudo spectrum analyzer. I have seen demos with MATLAB software, there may be some freeware available.

Matt