Search found 72 matches
- Sat Aug 10, 2024 7:28 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: bending Falcate Braces
- Replies: 2
- Views: 4203
Re: bending Falcate Braces
I suppose you could get them wet, wrap them up in foil, and put them in the oven at 150 °C too.
- Tue Jul 23, 2024 7:27 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: "Mass producing" falcate braces
- Replies: 4
- Views: 4558
Re: "Mass producing" falcate braces
Jani, what temperature did you use to bend the spruce?
- Fri Jun 14, 2024 2:32 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Top Deflection rig
- Replies: 47
- Views: 96787
Re: Top Deflection rig
I reckon that Ibanez would be built like a brick shit house.... It sure is. Despite being fully hollow, it's not really an acoustic instrument. Although it's louder than a solid body guitar. I put 4.7 kg on the rig and only got 0.11 mm of deflection. So K is somewhere around 420,000 N/m and the top...
- Thu Jun 13, 2024 11:13 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Top Deflection rig
- Replies: 47
- Views: 96787
Re: Version 2
OK, the last one I showed was a bit crude. But I learned a lot, and have tried to improve it. https://lh3.googleusercontent.com/pw/AP1GczPgKTmesWJYfT_IeOUUHSWjK0mOsNxOQfopCSvOUlIDckBtnpkhRvoXVTyJLl6NPya30NeIOchCqEfptYJqKKrzD-mgrabQ9_CWsXH66Wdds8B9_qMlmOcxr2xFnU_YRdE01UgtMM7lx-KBTXVvAlxG6g=w1234-h929...
- Fri Apr 26, 2024 1:30 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Fun with CAD
- Replies: 0
- Views: 7242
Fun with CAD
So here's a fun experiment. I modeled a Gore Medium steel-string in CAD. Well, just the body so far. Here's how I did it. First, I used R.M. Mottola's very useful "G" Thang tool to draw the outline. I used the printed Drawing No. 4 from the book, and visually tried to find the radii and centers of t...
- Wed Apr 24, 2024 4:40 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Spreadsheets
- Replies: 6
- Views: 12165
Re: Spreadsheets
That's great, Jani. It makes me happy that someone finds it useful. I'm curious which method you used. Measure the action of every fret, every string Fit polynomials to the measured data Model the neck as a line + ellipse + circle Model the neck as a line + parabola The spreadsheet is set up to do t...
- Wed Apr 10, 2024 4:05 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: compensation spreadsheet question
- Replies: 9
- Views: 18262
Re: compensation spreadsheet question
Unfortunately, I have no further explanations, just further information. A little googling, and I found that steel strings on guitars are made of the same material as piano wire . Which is spring steel . Specifically, SAE grade 1080 ( ASTM A228 ), which has an elastic modulus of 190 GPa. Or maybe 21...
- Fri Mar 29, 2024 12:59 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: compensation spreadsheet question
- Replies: 9
- Views: 18262
Re: compensation spreadsheet question
Jurgen-- I know it's been four years since you posted this, but did you ever figure this out? I got the same results you did. I got a value for E that was nearly twice the usual value (411 vs. 210 GPa). Using your numbers for the E string: T = 8.07 * 9.80665 = 79.14 N ΔT = 79.14 * ((((135.7*325.25) ...
- Tue Mar 12, 2024 10:42 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Spreadsheets
- Replies: 6
- Views: 12165
Spreadsheets
I have posted several spreadsheets here before. Panel thickness, fret positions, fretboard radius/width, neck shape, intonation compensation, 4DOF model, brace stress/sizing. I decided to combine these into one big spreadsheet file with 20 worksheets, and create connections between them, so when you...
- Tue Mar 12, 2024 8:27 am
- Forum: The Gallery
- Topic: Edvin Guitars first falcate braced OM Size
- Replies: 9
- Views: 10635
Re: Edvin Guitars first falcate braced OM Size
I think that's right on target. 95/180/227. In any case, it sounds great!edvinguitars.fi wrote: ↑Tue Mar 05, 2024 6:04 amWithout weights ( except my weighty double laminated sides using purple heart in inner) I hit 96/178/226, by shawing off the back brace briefly, maybe 2-3mm
Thanks for sharing.
Greg
- Sat Mar 09, 2024 5:07 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Gore plate thickness maths help
- Replies: 8
- Views: 17720
Re: Gore plate thickness maths help
Well, with the caveat that I've never built a 12-string, I have these observations, based on my calculations: The panel is 60 to 70 % of the mass of the active area of the sound board. Mass is the #1 priority in a good sound board (other than not breaking, of course). Braces are 75% of the rigidity ...
- Mon Mar 04, 2024 4:46 am
- Forum: The Gallery
- Topic: Edvin Guitars first falcate braced OM Size
- Replies: 9
- Views: 10635
Re: Edvin Guitars first falcate braced OM Size
Wow. Gorgeous. Amazing work. Did you have any trouble obtaining North American woods (Walnut, Sitka) in Finland? And Spanish Cedar comes from Central and South America, I think? Usually used on nylon-string guitars, its flexural modulus is a little on the low side, at 9.12 GPa. Have you found much d...
- Wed Feb 28, 2024 11:18 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Where has everyone gone?
- Replies: 8
- Views: 18206
Where has everyone gone?
This forum (on "the book") used to be a lively place. Now it can be weeks between posts. I've posted some things that should be of interest to those who have the book, and, save for Trevor (thanks, Trevor!), I haven't gotten a single comment. So where have the "left-brained" people gone? Where can o...
- Tue Feb 20, 2024 12:02 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: 4 DOF Model
- Replies: 109
- Views: 226431
Re: 4 DOF Model in Google Sheets
Google Sheets is a bit slow on the 4DOF model (it's plenty fast for everything else). In the spreadsheet linked above, I only calculated every 1 Hz, 60 to 500, so 440 rows. This takes 9 seconds to recalc, so about 50 rows/sec, if for example, you change Kt. In a copy of this sheet I tried every 0.1 ...
- Sun Feb 18, 2024 2:26 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: 4.6.7 Neck cross sectional shape
- Replies: 0
- Views: 9672
4.6.7 Neck cross sectional shape
I couldn't find any threads about this section--I guess no one has implemented these formulas? Here's a Google Sheet for neck cross sectional shape , as in section 4.6.7. Look at the sheet labeled "back". You may make a copy and modify it for your purposes. I wasn't sure how to smooth over the trans...
- Sun Feb 18, 2024 1:46 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: 4 DOF Model
- Replies: 109
- Views: 226431
Re: 4 DOF Model in Google Sheets
Can Google Sheets implement the 4DOF model? Yes, it can. It works pretty well, too. The graph appears to exactly match the output from Jim's Octave script (graph I posted earlier in this thread), and is pretty close to the book, Fig. 2.4-4. The differences appear to be in the dB values, but the freq...
- Sat Feb 10, 2024 8:29 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: uery for Trevor re Compensation Calculations
- Replies: 46
- Views: 71915
Re: uery for Trevor re Compensation Calculations
OK, I made an improvement to the parabolic model. New formula is: y = M/2EI x(xlast - x) This gives just the relief of the parabola compared to a straight line from the nut to the last fret. So, similar to the circular formula, it's 0 at the nut and at the 18th fret. To get the right action at the 1...
- Fri Feb 09, 2024 4:13 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: uery for Trevor re Compensation Calculations
- Replies: 46
- Views: 71915
Re: uery for Trevor re Compensation Calculations
OK this thread's pretty old, but I thought I'd add my implementation to the pile. Here's a compensation spreadsheet using Google sheets. Yes, you can see the formulas. You can make a copy (File -> Make a copy). I used the sample data for measured action from Woodsy23 (eight years ago!), and I got pr...
- Tue Jan 30, 2024 12:11 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Natural resonant frequency of uncoupled top
- Replies: 6
- Views: 7408
Re: Natural resonant frequency of uncoupled top
Thanks, Trevor. I get it. I will have to fit the model to the prototype if I want any accuracy. My hope is that when coming up with a completely new design, where I know what frequencies I want for the first three resonances, a model will at least give me a target top stiffness (brace dimensions/mas...
- Mon Jan 29, 2024 2:26 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Natural resonant frequency of uncoupled top
- Replies: 6
- Views: 7408
Re: Natural resonant frequency of uncoupled top
Thanks, Trevor. That makes sense. So, if I designed with a target stiffness K, and I could estimate the mass m of the top within the piston area (I guess, within the Chladni line of the monopole mode) including the bridge and bridge plate, I should not expect an uncoupled frequency f = SQRT(K/m)/2π,...
- Sun Jan 28, 2024 1:39 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Natural resonant frequency of uncoupled top
- Replies: 6
- Views: 7408
Re: Natural resonant frequencies of uncoupled top
Or, asked another way, what is K-bar on page AII-7?
He says the equations have the form:
In which case, for the top,
But what which should be used to calculate MM or frequency, K or K-bar?
Greg
He says the equations have the form:
Code: Select all
ω^2 = K-bar / m
Code: Select all
K-bar = K + κA^2
Greg
- Sat Jan 27, 2024 12:42 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: Natural resonant frequency of uncoupled top
- Replies: 6
- Views: 7408
Natural resonant frequency of uncoupled top
In the 4DOF model, on page AII-7. Equ. AII 2-21, we see the natural resonant frequency of uncoupled top with small damping: ω^2 = (K + κA^2) / m This is quite different than the relationship used for frequency, stiffness, and mass used when calculating the monopole mobility: ω^2 = K / m I'm a little...
- Thu Jan 11, 2024 12:16 pm
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: brace sizing
- Replies: 0
- Views: 28721
brace sizing
There's not a lot of information in the book about sizing braces. There are some standard sizes given, such as a J-45 using 1/4 x 3/8" and 1/4 x 1/2" gabled. Or a CF+KBF falcate using 5x4 mm and 5x7 or 5x9 mm rectangles. The example stress calculation uses 6x8 mm and 8x15 mm gabled. And there's a di...
- Mon Dec 04, 2023 12:03 pm
- Forum: Instrument Builders Forum
- Topic: Qualities of Spruce
- Replies: 18
- Views: 33172
Re: Qualities of Spruce
I don't have data on the spread within a species, or even within Spruces, but I used the averages from wood-database.com to chart about 200 species, both softwood and hardwood. And there is a pretty good fit to a trendline relating density and stiffness. And an even better fit relating density and t...
- Tue Nov 14, 2023 10:39 am
- Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
- Topic: brace stress
- Replies: 5
- Views: 13311
Re: brace stress
By the way, for people in North America, it appears that a good substitute for King William Pine when making falcate braces, is Black Willow . Native to the Eastern US, and is not expensive. I haven't tried it myself, but the stress calculations look good, and the US Forest Products Lab says that 73...