Build Your Own

MichaelHorowitz · November 2005

Sorry...when I modded the board it messed up some of the permissions settings. You now can delete and edit your posts.

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bill raymond · November 2005

Bob Holo wrote:

I've been meaning to do some calculations to find out what kind of error this would amount to... (.01 or .001 or .0001) and even then, the error could be reduced by figuring out what the average error is over the relevant distances at the relevant pliage heights and putting some small amount of arc in the sanding stick to mitigate the error from non-arched sanded surface and force the average angle error (hypotenuse vs tangent) to zero. Once you get to the point where the error from wood expansion is greater than the error from the sanding system - you're good to go.

Bob, you're making this way too complicated. The error is de minimis. The wood will accommodate to a non-radiused angle--believe me, I've done it. Occam's razor applies; Mario wouldn't have spent a lot of time calculating miniscule fractions of an inch--he just went ahead and built the guitars!!

bill raymond · November 2005

Jack wrote:

Any chance you guys can post some photos of what you've worked up? ... Even if you're not interested in making stuff for others, I, at least, would be interested to see what you've done.

Best,
Jack.

Here's some old photos of the first Macc. I built.

Bob Holo · November 2005

Sure - you're right - the wood will take it. (it won't de-lam)

The reason I've been giving this so much thought dates back to some transducer design research I've done. Loudspeaker/transducer design works with a lot of the same concepts that guitar building does. Ironically, most of the things you try to do away with in transducer design (resonance / harmonics) are the things you try to encourage and shape in guitar construction. It turns out that in transducers, the transition between the transducer and its suspension / frame is really critical. Unevenness (hot spots) along the circumference of the diaphragm tend to produce pressure differentials that produce different levels of damping on the diaphraghm. In very limited and highly controlled cases, that's good - but mostly it's bad. The reason is that every time an energy wave encounters a pressure differential (such as a wall or a corner or a pinched area in a vibrating surface) it produces a secondary wave-front whose output is partially antiphase to the primary wavefront... basically it just converts some energy that would have been used for sound - into heat. As guitars are only about 6% efficient to begin with - I've been doing a lot of reading and thinking on sources of inefficiency. Builders like Olson & Traugott go through a lot of trouble to make sure the pressure is evenly distributed across structural members (vacuum presses, CC routers, radius dishes etc...) presumably for this reason. When people talk about breaking in a guitar by playing it so that "it learns how to vibrate" this is partially what they're talking about. IE, over time, the wood eases in areas where it's slightly pinched.

So, would a flat sanding board give a glue joint that pinches the top unevenly? Who knows. I'm going to have a lot of fun doing Chladni mode patterns on soundboards to figure out what makes a difference and what doesn't. If there's any meat to it, I'll publish it in the Guild journal.

Hey, so let me step down off my "nerd soapbox" and ask:

Did you find any pictures of your guitar? ***edited*** I just saw that you posted pictures... BEAUTIFUL! Nice work, Bill.

Oh, and also -

San Diego Bill Raymond - are you a retired stuntman, or is that a different Bill Raymond?

bill raymond · November 2005

Bob,

Thanks for the nice word about my guitar. The next ones will be closer to the real thing. No, I'm not a retired stuntman! I'm a not-yet-retired enrolled agent (I represent people before the IRS).

a · November 2005

did anyone try this?

http://www.acousticguitar.com/Gear/advi ... tion.shtml

Peter Davies · November 2005

It's great to find this site about Selmer Maccaferri guitars.
Bill Raymond put me on to it. We've been corresponding for a long time, exchanging any information we found in order to build our own.
I see that Bill's put a link to a site I put up to record my progress so far. I did it to share my limited experience on these guitars as there's not a lot on the web on their construction details.
For example, has anyone seen (or better still, got a photo of) the inside of an original Mac, to explain / describe the crease just behind the bridge area? The Selmer Book (by R.F.Charle) only touches on this point.
Any construction details would be a wonderful resource.
All the best with the site,
Pete

Peter Davies · December 2005

Sorry to have killed this topic stone dead.
I just assumed everybody had an original Mac in the attic to get construction details

Cheers,
Pete

Digger · December 2005

Collinsguitar wrote:

Hello everyone,
I just thought I would chime in with a little update on the book.

Mr. Collins, have you got a publication date yet?
Regards,
Digger.

While I'm here, and completely off topic, may I say how useful I find this forum to be. I would post more but, being very new to the genre, have nothing of relevance or interest to say. Any queries I might have I can easily find the answers to with all the information already posted.
Thanks.