Another McKnight Build

[Mary]

Originally Posted by Steve Kinnaird

Tim, no one smiles that much gluing bindings together.
Those green things are suspect....
BTW, it's looking great. Beautiful set of Ziricote! Steve

Did you notice the green stuff hanging in the shop? Our son and future daughter-in-law grew peppermint. I now have a winter's supply of tea drying.

[bk314159]

I got some new photos from Tim and Mary so let's take a look.

Here's the first top braced being placed:



Tim cuts the lining slots so the top fits properly:



Is this really an accurate to place the bridge Tim? (I left out the photos of Tim measuring precisely.) :



A necessary evil process I'm sure:



I asked Tim if he could use a different piece of wood for the backstrap and he was kind enough to oblige. Thanks Tim! Here he's planing it down:



I like this so much better:



That's all for this time. Thanks for taking a look.

BK

[Mary]

I like this one much better, too!

[fulfillingsoul]

One more clarification on the method is whether your fingerboard is elevated from the soundboard, that is to further reduce the torque on the soundboard upper bout?

Originally Posted by Tim McKnight

Its hard to say. Its a lot more work (read labor hours) plus it adds material cost so it may not be for every one. Its likely it will never make it into mass production for those two reasons alone. I only make changes in my build process if there is a benefit to tone, play-ability or structure and pretty much absorb the costs, thus far... I can see the benefit of not needing a neck reset though none of my guitars have required a neck reset yet in my 20 years of building.

[Tim McKnight]

Originally Posted by fulfillingsoul

One more clarification on the method is whether your fingerboard is elevated from the soundboard, that is to further reduce the torque on the soundboard upper bout?

No, I have never built an elevated FB extension ... yet... but it could have some tonal advantages... if one considers the bracing scheme to take advantage of the design.

[bk314159]

I just received some more photos from Mary so let's take a look.

First, the binding is ready to shave:



Tim is planing the binding:



Tea leaf powder testing gives Tim a clue where to shave more from the bracing:













Tim sprays the inside back and sides:



The Ziricote sure does pop when it's sprayed.



Tim - what are you looking for with each of the tea leaf patterns? What do you do to produce each of the different patterns?

I love the look of the back and sides after being sprayed. What a tease!

Thanks for looking,
BK

[cotten]

Having had Tim build my AGF Award guitar, I'm confident that I can answer the question about what Tim's looking for with the tea leaf powder. One has to understand the process first.

You see, first Tim plays some music very loudly on some sort of magic playback system. Then he sprinkles the tea leaf powder on the soundboard. If it likes the song, it arranges the powder into a smile pattern. If not, then a frown. You can see that in the first powder shot above - it was a "song" by 2 Live Crew, and the guitar top clearly demonstrated its musical sensibilities. If it likes the song a LOT, it forms the shape of a wide open "O0ooo," like the third picture. There, the music was by Doyle Dykes, and again, the guitar top responded appropriately. That's a sign that this guitar will know the difference between good music and noise!

I'm not entirely sure what the other shapes that the powder forms signifies, but then I'm not the builder. Some things are trade secrets you know...

cotten

[Mary]

Cotten should do all our commentaries. I think I like his answers best. The first picture does look like a cyclops now that you mention it!

McJammers were invited to sit through a class of this process during the 2011 McJam. I wonder what they remember.

[Tim McKnight]

Actually I used black sand in these pictures but I have used tea leaves, saw dust, corn meal and glitter in the past. The sand just gives me the most color contrast and is easiest to see. I put the sand in an empty, high tech, Parmigiana cheese shaker and then sprinkle sand all over the top, not cheese. The top is supported on 3 or sometimes 4 foam blocks while I hand hold a 4" round speaker about 1/2" above the top. The speaker is connected to an adjustable audio frequency generator. I set the frequency to about 50 Hz and gradually raise the frequency until the (un-voiced) top begins to vibrate. Once the sand begins to dance on the surface of the top, at a given frequency, it will settle at nodes, which are the non vibrating parts of the top [or back], at that specific frequency. This is no more than a visual representation of how the guitar top (or back) is moving or flexing at that particular frequency. I am watching as the long dipole, cross dipole, mono-pole and other standard modes develop and noting at what frequencies they form at. This gives me an idea of how the top is going to move at these frequencies.

I chart all of these frequencies and draw the node lines on a graph paper that is saved for every guitar that I build. This is my own personal library of my work. It gives me data that I can refer back to after the guitar is strung up. I can go back and make notes of what I liked and disliked about the final guitar. It has been a huge help to me to shape the tone for each customer and gives me data that I can review and use for future guitars.

After I have generated a pattern at the first mode, I shake the sand off, re-coat the top with more sand and begin raising the frequency gradually until the next mode magically appears, chart that one and keep going until all frequencies have been identified. I am most concerned with a specific frequency that appears around 250 Hz. This should be, but not always is, called the "ring and a half mode". Once this appears (2nd picture) the ring will not be fully developed or closed as it is in your 3rd photo of the Chladni pattern. The ring is often open at the top and bottom (see 2nd picture). My goal is to systematically remove wood from the braces beneath the top until this ring closes (3rd picture). That is where the challenge presents itself.

I flip the top over and use a small finger plane and begin removing wood from one brace at a time. You take only a few thousandths of wood off at a time, then flip the top over, sprinkle with sand, vibrate it and watch to see which way the nodes moved. Often times the brace that you think you should remove wood from makes no difference so you move to another brace and the pattern changes and you just scratch your head and wonder???

For most of my career I have voiced my tops and backs by the old world method of "Tap Tuning". I learned this technique by trial and error and later it was much refined while I studied with Ervin Somogyi and it has worked very well for me. Its very much the same means to an end but you rely more on your ears and tactile touch throughout the voicing process to achieve the tone and response that you are targeting. Chladni testing is a similar method of arriving at the end goal but more so relying on visual feedback of the patterns to guide your chisel and plane during the wood removal phase.

I still voice my tops and backs primarily by Tap Tuning but I also chart each step using Chladni patterns to see the changes that I am making. Often times Chaladni patterns will guide and support tap tuning so I continue to use both methods simultaneously. Most times they overlap and support each other but sometimes they don't and that leaves me with even more questions. I should note that credit should be directed towards Alan Carruth and Mark Blancard as they are both experts in Chladni patterns and I have learned a significant amount from both of them. Its the method that they have chosen as their primary means of voicing their tops and backs.

[bk314159]

Hi John - thanks for answering my question. Your explanation certainly is easier to understand. So now I understand the difference between a OO and a OOO guitar!

Hi Mary - I would have loved to sit through that class. Thanks for the new photos.

Thanks Tim for the tad more scientific explanation. Do different tops (spruce, cedar, redwood) produce different Chaladni patterns at the same frequency?

BK

[Tim McKnight]

Originally Posted by bk314159

Do different tops (spruce, cedar, redwood) produce different Chaladni patterns at the same frequency?

BK

There are some vague similarities at specific frequency [ranges] but each top exhibits its own unique patterns. The top will display one set of patterns before its braced, a different set after its braced, a different set after its voiced and yet a different set after the top or back is glued to the rim. Different bracing patterns will also have vastly different Chladni patterns as well.

[Rainbow]

Oh man, I am really tempted to be part of McKnight family after reading so much. Tim, do u still happen to have highly figured quilted Maple left?

[Tim McKnight]

Originally Posted by Rainbow

Oh man, I am really tempted to be part of McKnight family after reading so much. Tim, do u still happen to have highly figured quilted Maple left?

Hi Rainbow,

We just happen to have a couple of gorgeous sets of Quilted / Birds Eye Maple left as well as some exceptional curly fiddle back sets and one unique "caramelized baked maple" set. Perhaps we should talk?

[cotten]

Originally Posted by bk314159

Hi John - thanks for answering my question. Your explanation certainly is easier to understand. So now I understand the difference between a OO and a OOO guitar!...

Why thank you! Of course, now you know why I just enjoy guitars, not build them. And yes, I DO enjoy McKnights! (Both the guitars and their builders.)

cotten

[Mary]

Originally Posted by Rainbow

Oh man, I am really tempted to be part of McKnight family after reading so much. Tim, do u still happen to have highly figured quilted Maple left?

No child left behind.

Maybe you should plan to c'mon over sometime.