What actually goes into designing and building a new model?

[Tim McKnight]

The first new tool that we can put to the test is the top and back half template. Why a half template instead of a full template? Well there are several reasons ... it takes less material to make, it takes up less room to store it and finally it insures that both halves of the guitar are an identical match.





Next we lay out the sound hole location and size based on:
1) the scale length
2) the total number of frets
3) and the sound hole diameter is based on if there is a sound port or not. In this case there will be.

[j. Kinnaird]

Do you make your soundholes smaller if there is a sound port? If so are you shooting for total area or some other target. I have read a doctoral dissertation about research done on the resonance of a guitar and how that changes with changes in sound hole area. The conclusion was opening edge length was more important. F holes are examples of openings with lots of edge compared to area.

Sorry, I seem to have drifted off topic

[j. Kinnaird]

Originally Posted by Tim McKnight

Good morning John,
I thought I would share with you the amount of time involved from a phone conversation with a client to ready to use forms. We probably spent ~30 minutes on the phone discussing their ideas and then I spent another 1 hour of CAD time and had emailed pictures to him. He requested a few more changes which took 15 minutes and then final drawings were approved. Total CAD, email and client time was 1 hour 45 minutes.

Next I ripped the particle board into blanks ~10 minutes. Uploaded the files into the CNC and began cutting. Cut time averaged 2 minutes for for each blank and we cut a total of 21 blanks = 52 minutes.

As the cut blanks were coming out of the CNC I was gluing up the layers which took ~45 minutes.

Total clamp time was roughly 1 hour.

So from a phone call to ready to use forms we will round it up to: 4-1/2 hours. Not bad for a morning's work before lunch.

As I prefaced in the beginning of this thread, there are lots of ways to arrive at the goal line and one can use whichever method they see fits their needs best considering their budget and personal criteria. Its certainly not necessary to use CAD and CNC to jump start your projects. 28 Years ago I accomplished similar results using poster paper, pencil, T-square, drafting table, scissors and human powered hand tools. In today's age I find it easier and more time efficient sharing an electronic drawing with a client within a few hours inception instead of mailing them a paper template I cut with scissors. I think its also a comfort for them to see something they had input in designing and a facsimile of the guitar they will receive in a few months down the road.

I can certainly see the appeal of this. I imagine customers like it and it surely does streamline the process from conception to execution. I really appreciate your sharing the details of your build.

[Tim McKnight]

Originally Posted by j. Kinnaird

Do you make your soundholes smaller if there is a sound port? If so are you shooting for total area or some other target. I have read a doctoral dissertation about research done on the resonance of a guitar and how that changes with changes in sound hole area. The conclusion was opening edge length was more important. F holes are examples of openings with lots of edge compared to area.

Sorry, I seem to have drifted off topic

If I am planning a side sound port I do reduce the front sound hole by the approximate area of the sound port. As you enlarge the sound hole and / or add additional holes to the body you raise the Helmholtz frequency of the sound box. If you enlarge the sound hole or add additional holes the timbre of the sound box rises and quickly becomes thin and tinny sounding as it loses bass response and warmth. By reducing the main sound hole by only 1/8" you lower its main air frequency.

Here is an experiment you can try to help you hear the sound changes. Lay the guitar flat on its back and tap on the bridge wood with your finger and listen to the sound of the box. Take a 5" wide x 8" long piece of heavy paper or card stock and lay it on the top close to the sound hole. As you continuously tap on the bridge slowly move the card stock gradually across the sound hole and let me know what you hear, OK?

There was a device called the O-Port that you would insert into the sound hole. The company was eventually bought by Planet Waves and I am not even sure if they are still making the product. It was kind of a funnel or megaphone for the sound hole. It did change and lower the sound of the box but I always thought it had more to do with the added mass of the O-Port onto the top. After reading what you said above about the sound hole's opening edge length has me wondering if that is how the O-Port worked? The largest part of the funnel was inside the guitar but it would increase the sound hole's leading edge circumference. Hmmm, where is Alan Carruth? I bet he could set us straight with a more scientific answer.

Originally Posted by j. Kinnaird

I can certainly see the appeal of this. I imagine customers like it and it surely does streamline the process from conception to execution. I really appreciate your sharing the details of your build.

It does streamline the process John and we have found it to be very beneficial. Sometimes we "blue sky" about ideas on paper but its hard to imagine how they would look in real life. Sharing CAD drawings with clients is one way to help us go from blue sky concept to a dialog that shares accurate visual representations.

Some people think that using CAD, CNC and computers are taking the old world art out of the process. Its not as simple and finite as clamping down a billet of wood, clicking a mouse and eight minutes later it spits out a shiny finished guitar. That couldn't be further from the truth. This is still a VERY hands on process that will always utilize hand chisels, planes, hide glue, human tactile responses and sweat equity to build, voice and deliver a 21st century guitar to a client. In the end its our hands, eyes, ears, skill, wisdom and heart that does the building. These modern tools are just another arrow in the quiver that saves repetitive fatigue on our bodies and frees our minds to build the best guitars humanly possible.

Thanks for your questions and for following along. Happy Independence Day to you and yours.

[Treenewt]

Tim, I confess I’m one of those guys that shies away from modern tech in some areas, but not others. I think my upbringing and own biases towards old-school construction and techniques (which, admittedly, used the most advanced tools of their day at the time). Maybe it just makes me long for simpler times? I dunno!

However, I totally appreciate the skill involved with integrating CNC and other tech, as you have done over the years. It certainly requires its own skill set and wisdom, for sure! As you said there are many ways to approach that goal line! I’m enjoying seeing your “offensive playbook” as you walk us through it!

Happy 4th to you and Mary!

[vpolineni]

Originally Posted by Tim McKnight

There was a device called the O-Port that you would insert into the sound hole. The company was eventually bought by Planet Waves and I am not even sure if they are still making the product. It was kind of a funnel or megaphone for the sound hole. It did change and lower the sound of the box but I always thought it had more to do with the added mass of the O-Port onto the top. After reading what you said above about the sound hole's opening edge length has me wondering if that is how the O-Port worked? The largest part of the funnel was inside the guitar but it would increase the sound hole's leading edge circumference. Hmmm, where is Alan Carruth? I bet he could set us straight with a more scientific answer.

Not to go off-topic from your thread Tim but isn't the O-Port acting like a tornavoz? There was a discussion of it years ago here:
https://www.acousticguitarforum.com/...d.php?t=311303

Mike Kennedy of Indian Hill guitars has used the tornavoz on some of his builds. Hopefully he'll chime in here with his thoughts!

[Neil K Walk]

I've been doing a lot of house cleaning and my wife found the O Port I "won" at a McJam. Initially I though it was one of those reusable toilet flanges. For the life of me I couldn't figure out how to install it.

PS: I don't recommend trying to flush with it. Those golf balls are still rattling around inside my guitars.

[j. Kinnaird]

That o port reminds me of the device Macaferri (however its spelled) put inside those guitars with the enormous D shaped soundholes. It was like a scoop to channel the sound waves coming from the lower bout out the front of the guitar.

Early violins, made in the 14 hundreds more often than not had round openings similar to some of today's mandolins. Evidently that opening did not have enough edge and could not compete with the F hole. I'm just paraphrasing the research article I read. No doubt there are other structural variations necessitated when transitioning from round to F holes that make cause and effect difficult to pin down

[Tim McKnight]

Originally Posted by Treenewt

Tim, I confess I’m one of those guys that shies away from modern tech in some areas, but not others. I think my upbringing and own biases towards old-school construction and techniques (which, admittedly, used the most advanced tools of their day at the time). Maybe it just makes me long for simpler times? I dunno!

However, I totally appreciate the skill involved with integrating CNC and other tech, as you have done over the years. It certainly requires its own skill set and wisdom, for sure! As you said there are many ways to approach that goal line! I’m enjoying seeing your “offensive playbook” as you walk us through it!

Happy 4th to you and Mary!

Hi Newt,

My dad was a master cabinet maker and he always tried to put me to work sanding and he was a stickler for “progressive sanding” through the grits which I HATED to do. I tried to take short cuts but he always caught me and made me do it over which was twice the work in the long run. Back in the day he never owned a power sander and he made me sand using a block of wood to back up the paper. He would never EVER use a nail or screw even if his life depended on it. Everything that came out of his shop was joined precisely with glue and clamps, period. He was old school to the hilt. He taught me a lot and wish I could go back and learn more from him.

Originally Posted by vpolineni

Not to go off-topic from your thread Tim but isn't the O-Port acting like a tornavoz? There was a discussion of it years ago here:
https://www.acousticguitarforum.com/...d.php?t=311303

Mike Kennedy of Indian Hill guitars has used the tornavoz on some of his builds. Hopefully he'll chime in here with his thoughts!

You may be right Vpolineni but I don’t recall them referring to it as a Tornavoz. It functioned similarly but it was easily removable Where as a true Tornavoz is glued in place.

Originally Posted by Neil K Walk

I've been doing a lot of house cleaning and my wife found the O Port I "won" at a McJam. Initially I though it was one of those reusable toilet flanges. For the life of me I couldn't figure out how to install it.

PS: I don't recommend trying to flush with it. Those golf balls are still rattling around inside my guitars.

I bet Joey had some fun with it when you weren’t paying attention

Originally Posted by j. Kinnaird

That o port reminds me of the device Macaferri (however its spelled) put inside those guitars with the enormous D shaped soundholes. It was like a scoop to channel the sound waves coming from the lower bout out the front of the guitar.

Early violins, made in the 14 hundreds more often than not had round openings similar to some of today's mandolins. Evidently that opening did not have enough edge and could not compete with the F hole. I'm just paraphrasing the research article I read. No doubt there are other structural variations necessitated when transitioning from round to F holes that make cause and effect difficult to pin down

If you ever find that article on soundhole edge design John please share it with me. Sounds like some interesting reading and research.

[Treenewt]

Tim, your dad sounds like mine! No shortcuts!! I’m sure he taught you plenty, and pretty sure he’d be proud of the work you’re doing now!

[Tim McKnight]

Originally Posted by Treenewt

Tim, your dad sounds like mine! No shortcuts!! I’m sure he taught you plenty, and pretty sure he’d be proud of the work you’re doing now!

Thanks Newt, I’m humbled...

[Tim McKnight]

OK, getting back on track with the actual build. Pictured below we seal the soft Cedar top, in the area of the rosette. After the sealer dries it binds the wood fibers together and helps to make a cleaner cut or channel pockets to build the rosette into.







As that dries we layout the back using the new body template.

[j. Kinnaird]

What kind of sealer are you using on the top?

[Tim McKnight]

Originally Posted by j. Kinnaird

What kind of sealer are you using on the top?

Why, Bertolli Tomato and Basil Sauce silly

Actually its a 1# cut of flake super blonde shellac.

[Neil K Walk]

Cedar? Oh my, now I am intrigued! I don’t recognize the wood for the back and sides though?