Search found 1351 matches

by Trevor Gore
Mon Oct 15, 2018 10:22 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: 3 piece pernambuco back
Replies: 6
Views: 213

Re: 3 piece pernambuco back

John, I am assuming you're going for a live back because you're computing a target panel thickness. Check what the back panel mass will turn out to be and then compare that with other live back guitars you have made. I'm suspecting that the pernambuco might be too dense and therefore have too low a ...
by Trevor Gore
Wed Oct 10, 2018 10:10 pm
Forum: Instrument Builders Forum
Topic: Louro Faia for binding .. a complete failure
Replies: 24
Views: 545

Re: Louro Faia for binding .. a complete failure

kiwigeo wrote:
Wed Oct 10, 2018 10:53 am
Ok Trevor what's going on?? Time to come clean. :evil:
Well, I thought all luthiers could grow (and resorb) a third hand at will.

Are you saying you can't?

You'd better get down to the vet and see what he can do for you, or you might be permanently stuck with those four feet. :shock:
by Trevor Gore
Tue Oct 09, 2018 10:16 pm
Forum: Instrument Builders Forum
Topic: Louro Faia for binding .. a complete failure
Replies: 24
Views: 545

Re: Louro Faia for binding .. a complete failure

Trevor, you look pretty close to burning your fingers... Well, that shot was posed for the book. I was operating the camera at the same time as posing for the shot. But I don't wear gloves when bending wood anyway. I haven't burnt my fingers yet, but that's perhaps not a recommendation for others! ...
by Trevor Gore
Tue Oct 09, 2018 9:17 am
Forum: Instrument Builders Forum
Topic: Louro Faia for binding .. a complete failure
Replies: 24
Views: 545

Re: Louro Faia for binding .. a complete failure

Yes Trevor has caused a fair bit of grief pretty much round the world with that cutaway! :D I must have done dozens of those cutaways and never really had a problem. In terms of binding, the figured blackwood and figured sycamore/maple are the easy ones, because the wood is pretty floppy. The tough...
by Trevor Gore
Mon Oct 08, 2018 10:14 pm
Forum: Instrument Builders Forum
Topic: Louro Faia for binding .. a complete failure
Replies: 24
Views: 545

Re: Louro Faia for binding .. a complete failure

kiwigeo wrote:
Mon Oct 08, 2018 9:31 pm
It was you who designed that bldi cutaway OM with that cutaway horn with a radius so tight that the blackwood bindings started trembling in fear whenever I got them close to the mold!!
Yep, and they just submit to their fate as soon as I point a bending iron at them!

Show 'em who's boss! :D
by Trevor Gore
Mon Oct 08, 2018 9:07 pm
Forum: Instrument Builders Forum
Topic: Louro Faia for binding .. a complete failure
Replies: 24
Views: 545

Re: Louro Faia for binding .. a complete failure

I recently spent a week trying to bend some blackwood bindings for a Gore style OM cutaway. I gave up in the end and used some Brazilian Rosewood bindings I found hidden on one of my shelves.....that stuff just bent like butter!! A week???!!! Probably works better if you do it quicker! :wink: :mrgr...
by Trevor Gore
Fri Oct 05, 2018 9:44 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: interpretation of data
Replies: 9
Views: 341

Re: interpretation of data

The new piece has typical density for its Young's modulus, whereas the original piece had rather high density for its Young's modulus, so at least you're now starting on a more level playing field. The best wood (in terms of making the lowest mass tops) is usually the lowest density wood, because ad...
by Trevor Gore
Thu Oct 04, 2018 1:39 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: First Falcate underway! Plate Thickness question?
Replies: 10
Views: 563

Re: First Falcate underway! Plate Thickness question?

The small peak at 221Hz may not be the T(1,1)3. You have identified the B(1,1) at 230Hz. Usually the T(1,1)3 is a little higher in frequency than the B(1,1), so I would expect the T(1,1)3 to be around 233Hz. The peak at 221Hz may be either the result of a whole body mode (bending like the fundamenta...
by Trevor Gore
Thu Oct 04, 2018 8:54 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: First Falcate underway! Plate Thickness question?
Replies: 10
Views: 563

Re: First Falcate underway! Plate Thickness question?

The T(1,1)1 and the T(1,1)2 seem a little high, but the T(1,1)1 is likely a consequence of the T(1,1)2. The T(1,1)3 is in about the right place for a live back with a T(1,1)2 at 180Hz. What size top braces did you use and what Young's modulus were they? Also worth checking the T(1,1)2 frequency agai...
by Trevor Gore
Wed Oct 03, 2018 11:14 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Three Random Questions
Replies: 3
Views: 135

Re: Three Random Questions

#1: Do these density, frequency and Gpascal values fall in line with others that use sitka? There's a saying that some of us are wont to use "Spruce is spruce", meaning that across all the various spruce species Young's modulus is proportional to density, irrespective of species. Your piece of Sitk...
by Trevor Gore
Fri Sep 28, 2018 9:15 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: interpretation of data
Replies: 9
Views: 341

Re: interpretation of data

Keeping count of the zeros is often a source of error. Everything should be in SI units (meters, kilograms, seconds). Stress/pressure is in Pascals, but we work in GPa (10^9 * Pascals). Your answer should come out in meters, which then need multiplying by 1000 to get millimetres. Applied loads (when...
by Trevor Gore
Thu Sep 27, 2018 10:51 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: interpretation of data
Replies: 9
Views: 341

Re: interpretation of data

Would be great if you can check the calculations. I checked using the data in your first post. I get the same El, Ec, G and density as you, but for f=60 I get a target thickness of 2.52mm rather than the 2.83mm you got. You need to check your coding for equation 4.5-7. Check your results using the ...
by Trevor Gore
Thu Sep 27, 2018 9:20 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: interpretation of data
Replies: 9
Views: 341

Re: interpretation of data

I continue this build with this plate and for the next guitar I search for a lower density plate. You report a density of 428.1 kg/m^3 with a El of 8.42 GPa. Again, I haven't checked your calculations but I'll assume you're correct. Certainly, this is not a great piece of wood and you have recognis...
by Trevor Gore
Wed Sep 26, 2018 10:33 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: interpretation of data
Replies: 9
Views: 341

Re: interpretation of data

For the calculation of the predicted panel mass I used the formula for the volume of a cylinder (I measured the topcontour with a tape measure). I then used the formula mass = density*volume. ... ... predicted top mass top contour (mm) 1480 top height (mm) 2,830450887 2pi 6,283185307 r= contour/2pi...
by Trevor Gore
Mon Sep 17, 2018 9:53 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Waterfall Spectrogram Program
Replies: 2
Views: 182

Re: Waterfall Spectrogram Program

I can't help you with phone apps, John, but the plots I did were made using Spectrum Lab on a PC. I think later versions of Visual Analyser also do waterfall plots, but not as flash looking as those in Spectrum Lab.

Any one else?
by Trevor Gore
Mon Sep 17, 2018 9:45 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Measuring beyond the decimal place for distances >600mm
Replies: 5
Views: 291

Re: Measuring beyond the decimal place for distances >600mm

I use a piece of 1/8" by 1/2" brass rod (Bunnings) that I machined to length on a milling machine with a good digital readout. It turned out to be 0.2mm short, but I just zero my calipers at +.2 to take care of that. If I was doing it without heavy machinery, I would likely just make a number of scr...
by Trevor Gore
Fri Sep 14, 2018 9:02 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Determining Panel Mass on Target Plat Thickness Chart
Replies: 1
Views: 171

Re: Determining Panel Mass on Target Plat Thickness Chart

The panel mass is the wood density multiplied by the panel volume. The panel volume is its thickness (which you have just calculated) multiplied by its area. The panel area is the bit that is hard to calculate. If the guitar shape was drawn on a CAD type program, the program will give you the area. ...
by Trevor Gore
Thu Sep 13, 2018 12:49 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: determination of soundboard flexural rigidity
Replies: 2
Views: 179

Re: determination of soundboard flexural rigidity

I don’t see how to calculate the neutral axis of the soundboard cross section in fig. 4.4-19. Take the moments of all the component areas about the base, setting up a large equation similar to the penultimate one on p 4-37. For calculating the x for the soundboard cross section do I have to take th...
by Trevor Gore
Thu Aug 23, 2018 2:24 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Rosette Router Jig
Replies: 5
Views: 541

Re: Rosette Router Jig

The hole in that bar is a through hole. The nuts and Belleville washers lock the threaded rod to that bar which screws in and out of the nuts on the wide bar, causing it to move. The piece of angle (NOT the bracket that had the gauge on) captures the sprung nut at the wide bar so that it does not ro...
by Trevor Gore
Sat Aug 18, 2018 1:08 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Rosette Router Jig
Replies: 5
Views: 541

Rosette Router Jig

Below, as per a request , a few photos of my precision router jig as used for rosettes. A few things go together to make this thing accurate. First, the large diameter pivot (10mm), the stiff structure of the thing, low runout after-market router collets on the DeWalt trimmer and the anti-backlash a...
by Trevor Gore
Sat Aug 18, 2018 12:25 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: NEW BUILD tap testing Englemann
Replies: 5
Views: 481

Re: NEW BUILD tap testing Englemann

The trip was very good, thanks. Was over with Robbie O'Brien doing the Modal Tuning Course a couple of times. Nice burst on that Gilet guitar! Just looking at the frequency responses can you tell if a particular piece is stiff across the grain, ie high Fc equals stiff piece of timber across the grai...
by Trevor Gore
Thu Aug 16, 2018 11:44 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: NEW BUILD tap testing Englemann
Replies: 5
Views: 481

Re: NEW BUILD tap testing Englemann

Any comment would be appreciated, some time since I did the course and had used the formula. Lower bout at 380mm is large for a 00 sized guitar. They are usually around classical size at 360-370mm. I recently measured one of Gerard's 00's at 370mm. I think CF Martin make them a little smaller than ...