Search found 447 matches

by johnparchem
Mon Apr 06, 2020 8:04 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: having a go at spectrums
Replies: 5
Views: 81

Re: having a go at spectrums

They look sort of noisy to me, like maybe your mic is clipping. You might turn down the gain. Because of the extra peaks I can not tell what the back might be.
by johnparchem
Fri Apr 03, 2020 7:48 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Closed box T(1,1)2 less than 200 Hz - Edge thinning
Replies: 3
Views: 108

Re: Closed box T(1,1)2 less than 200 Hz - Edge thinning

I think both of your guitars that came in around 195 Hz had a good chance of hitting 180 Hz once finished. It would have depended on the mass of the bridge and how much the bridge lowers the top's resonance. On the steel strings I have been seeing <-10 Hz adding the bridge and another <-5 adding the...
by johnparchem
Thu Apr 02, 2020 6:28 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Closed box T(1,1)2 less than 200 Hz - Edge thinning
Replies: 3
Views: 108

Re: Closed box T(1,1)2 less than 200 Hz - Edge thinning

Thinning the edges is a good way to Lower T(1,1)2 Lowering the braces is a real good way to Lower T(1,1)2 Having A thinner top is a good way to Lower T(1,1)2 The tops resonance is based on both stiffness and mass. In all the above three cases you are lowering the stiffness more than you are lowering...
by johnparchem
Wed Apr 01, 2020 2:57 am
Forum: Instrument Builders Forum
Topic: Bellied up top
Replies: 25
Views: 689

Re: Bellied up top

I do not think changing the tone bars will do anything for you. The belly is from the nut side of the bridge rotating in. One fix I might try if I did not want to remove the top would be to sister taller braces on the over carved x-braces from the X to the finger braces on each side. Having said tha...
by johnparchem
Sat Mar 28, 2020 9:55 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: 1. falcate braced classical
Replies: 4
Views: 534

Re: 1. falcate braced classical

Ok, old top off, new top on. Actually easier than I thought. Thanks the advice Jim. New values after binding and sanding: T(1,1)1= 90Hz T(1,1)2=195Hz T(1,1)3= 244Hz I had been wondering why the T(1,1)1 is so low until I checked the diameter of the soundhole... Great! Instead of 85mm I have just 79m...
by johnparchem
Fri Mar 27, 2020 2:04 am
Forum: Instrument Builders Forum
Topic: Bellied up top
Replies: 25
Views: 689

Re: Bellied up top

I was taught not to start the scallop before the bridge plate for structural reasons. When I shift the braces toward the sound hole I am thinking about just the X not the entire scallop pattern. The low part of the braces are right where you need structural support.
by johnparchem
Wed Mar 18, 2020 8:24 am
Forum: Instrument Builders Forum
Topic: Carbon Graphite neck bracing, too much?
Replies: 6
Views: 2086

Re: Carbon Graphite neck bracing, too much?

Richard thanks for your reply, I had not thought about the creep factor over time. On many of my guitars I use a 2 way truss rod so I can dial it out. But for many of my classical guitars without a truss rod it is worth a thought.
by johnparchem
Wed Mar 18, 2020 7:47 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: 1. falcate braced classical
Replies: 4
Views: 534

Re: 1. falcate braced classical

I have built all my falcate classical guitars without a lower transverse brace. Without a lower transverse brace, I am between 10 to 10.5 mm on the primary falcates and 8-9 on the secondary falcate braces to get the top strung up to resonate at 190 Hz and 200 Hz respectively. My first guitar had num...
by johnparchem
Wed Feb 26, 2020 11:23 am
Forum: Instrument Builders Forum
Topic: Why a neck volute?
Replies: 7
Views: 2229

Re: Why a neck volute?

The look good? I know that some of them were part of the headstock to neck joint. I believe a lot of them are decorative.
by johnparchem
Mon Feb 24, 2020 1:36 am
Forum: Instrument Builders Forum
Topic: Carbon Graphite neck bracing, too much?
Replies: 6
Views: 2086

Re: Carbon Graphite neck bracing, too much?

I have used carbon fiber rods in necks with truss rods, and have had no issues providing relief using the truss rod. Part of the reason for this may be that when the fretboard is glued on the rod is close to the neutral axis so it may not really be stiffening the neck all that much. After I was show...
by johnparchem
Mon Feb 03, 2020 3:15 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: cosed box Frequency response falcate OOO
Replies: 10
Views: 3184

Re: cosed box Frequency response falcate OOO

Very nice, my favorite steel string's spectrum graph is very close to your falcate 000. It compares well to any guitar I have heard, at least for my use as a fingerstyle guitar. The x braced guitar spectrum looks good to me. I built a few falcates with 180 Hz top and was very happy with them. I bet ...
by johnparchem
Sun Feb 02, 2020 1:54 am
Forum: Instrument Builders Forum
Topic: Stain on soundboard
Replies: 11
Views: 2701

Re: Stain on soundboard

It is hard to tell but an interaction with something in the gig bag. I wonder as the somewhat localized stains.
by johnparchem
Tue Jan 07, 2020 3:17 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: VA plots for tap test on plates
Replies: 13
Views: 3242

Re: VA plots for tap test on plates

Thanks John. Having identified the better tops i have now started on the sides as i want to be in a position to use the top or back as soon as its built. Auckland has permanently high humidity so i don't like leaving the plates hanging around for too long. If you don't mind me asking, for the brace...
by johnparchem
Sun Jan 05, 2020 10:52 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: VA plots for tap test on plates
Replies: 13
Views: 3242

Re: VA plots for tap test on plates

I would do what you did and put an average value or 1 for the 6.9 for the G for plate ls002. Your results will be a lot close to correct and make for a better comparison. With that low cross grain stiffness the fdiag might be really low.
by johnparchem
Sun Dec 29, 2019 1:01 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Unusual Panal Size
Replies: 6
Views: 1949

Re: Unusual Panal Size

I just had to do this, and I posted the steps I took earlier this month. I at least tried to use the information from the Book. Link: viewtopic.php?f=33&t=8707
by johnparchem
Mon Dec 09, 2019 4:34 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Spectrum change with age
Replies: 5
Views: 2099

Re: Spectrum change with age

I noticed that the resonance frequency shift with changes in the string height off the top in the saddle position. So if you ever needed to adjust the action, you might see a change.
by johnparchem
Sat Dec 07, 2019 10:57 am
Forum: Instrument Builders Forum
Topic: First Flamenco Guitar.
Replies: 6
Views: 3214

Re: First Flamenco Guitar.

I did a bit more analysis of the guitar after having it for 4 months. All of the flamenco players that have tried it have been shock at its sound. I watched them go from skeptical to slightly interested when they felt how light the guitar was, to very engaged when they started playing and spending a...
by johnparchem
Sat Dec 07, 2019 10:51 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Plate target thickness of non rectangular plates using deflection testing
Replies: 2
Views: 1539

Re: Plate target thickness of non rectangular plates using deflection testing

I am trying to match my results from my first Flamenco. It is an amazing sounding instrument. All of the flamenco players that have tried it have been shock at its sound. I watched them go from skeptical to slightly interested when they felt how light the guitar was, to very engaged when they starte...
by johnparchem
Fri Dec 06, 2019 5:41 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Plate target thickness of non rectangular plates using deflection testing
Replies: 2
Views: 1539

Plate target thickness of non rectangular plates using deflection testing

I am starting a new flamenco blanca guitar with spanish cypress back and sides. The Gore plate thicknessing method using tap tones as described The Book requires evenly thicknessed rectangular plates. Often times with nice back and side sets the plates are non rectangular taking advantage of the fac...
by johnparchem
Sat Nov 23, 2019 4:40 am
Forum: Instrument Builders Forum
Topic: Bending Sides issue
Replies: 17
Views: 3117

Re: Bending Sides issue

I bend both on a fox style and a bending iron. I never soak the wood, rather I lightly spritz it with the goal of initially quickening the heat transfer into the wood. On a pipe I like to bend very hot with only a light spritz, I always thought that wet wood would try to limit the temperature in the...
by johnparchem
Fri Nov 15, 2019 2:38 am
Forum: Instrument Builders Forum
Topic: Amateur mess up, do I start over or make raised fretboard...
Replies: 6
Views: 1594

Re: Amateur mess up, do I start over or make raised fretboard...

First off, when sanding it is really easy to take more off the edges than the center. One has to fight it and check constantly. This issue exists for sanding straight or sanding with a radius board. I think that the friction of sanding tends to place a downward force on the leading edge of the sandi...
by johnparchem
Wed Oct 16, 2019 9:51 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Classical Bridges using CF
Replies: 16
Views: 3655

Re: Classical Bridges using CF

I machine the bridge blanks on a small micromill. The CF presented no problems. I wear a dust mask. I use 3K 5.7 oz plain weave fabric. (Sorry about the imperial measurement.)
by johnparchem
Wed Oct 16, 2019 2:19 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Classical Bridges using CF
Replies: 16
Views: 3655

Re: Classical Bridges using CF

I take some from the top and some from the bottom (including the radius) until I get the thickness that I want. I am considering simplifying my classical bridges. Like the steel string I will include a 1mm bridge patch and a layer of CF fabric under the the braces. When I make the bridge I will sand...
by johnparchem
Sun Oct 13, 2019 8:55 am
Forum: Instrument Builders Forum
Topic: First Flamenco Guitar.
Replies: 6
Views: 3214

Re: First Flamenco Guitar.

Thanks guy! The guitar was French Polished. I have been spending a bunch of time learning how to sort of play Flamenco guitar. I might find a real teacher.
by johnparchem
Wed Aug 28, 2019 9:36 am
Forum: Instrument Builders Forum
Topic: First Flamenco Guitar.
Replies: 6
Views: 3214

First Flamenco Guitar.

This is my first Flamenco Guitar built following the Paco Chorobo video class offered by Robbie O'Brien. It was a fun course to follow as it include a lot of slide visits and interviews in the Spanish flamenco community. Paco Chorobo is an outstanding flamenco guitar builder and a wonderful flamenco...