Search found 1300 matches

by Trevor Gore
Sun May 20, 2018 10:39 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Tapping panels for thickness?
Replies: 6
Views: 211

Re: Tapping panels for thickness?

That's very low density and low stiffness redwood. Normally I'd expect Elong to be in the 10 GPa region. So if it feels stiff, as you say, it suggests something is wrong somewhere. If not, figure out the mass that the top panel would be and see if the low density compensates for the lack of stiffnes...
by Trevor Gore
Sat May 19, 2018 1:18 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Tapping panels for thickness?
Replies: 6
Views: 211

Re: Tapping panels for thickness?

Chris, the density seems very low for walnut at 395.9kg/m^3. ~570 kg/m^3 is fairly typical. Having said that, 2.3mm for a back panel thickness is fairly reasonable for a live back. Just a point of clarification... When using the Youngs Mod Dynamic Method formula, the actual measurements of the panel...
by Trevor Gore
Fri May 18, 2018 9:41 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Tapping panels for thickness?
Replies: 6
Views: 211

Re: Tapping panels for thickness?

Chris,

The "p" is ρ (Greek "rho") and is the symbol for density. See Fig 4.5-4.

There's more stuff on coding up Equ. 4.5-7 here and here. The typos have been fixed in the 2nd edition.
by Trevor Gore
Thu May 03, 2018 8:09 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Measuring top and back frequencies while voicing
Replies: 21
Views: 6055

Re: Measuring top and back frequencies while voicing

I was hoping someone else would chine in... Jim, do you mean adding Q in on a panel tap or a guitar box tap? You seem to be inferring a panel tap. If that's the case, the first thing to do is to determine what a Q measurement is: at a single frequency - a resonance governed by the panel dimensions, ...
by Trevor Gore
Thu May 03, 2018 8:51 am
Forum: Instrument Builders Forum
Topic: alternative fingerboard woods
Replies: 7
Views: 423

Re: alternative fingerboard woods

The stuff I have has worked quite easily. The grain does interlock, but nothing like as much as EIR, for example. Planed with the grain with a high angle plane will give a mirror-type finish. I've glued it with Titebond, fresh surfaces, no problem at all. Again, I've probably met more silica in EIR ...
by Trevor Gore
Wed May 02, 2018 9:13 am
Forum: Instrument Builders Forum
Topic: alternative fingerboard woods
Replies: 7
Views: 423

Re: alternative fingerboard woods

Brushbox is another that works really well for fretboards.
by Trevor Gore
Sun Apr 22, 2018 5:10 pm
Forum: Instrument Builders Forum
Topic: RIP Jim Williams
Replies: 4
Views: 419

Re: RIP Jim Williams

A sad loss indeed. He influenced many. One of the pioneers...
by Trevor Gore
Thu Apr 19, 2018 10:15 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Measuring top and back frequencies while voicing
Replies: 21
Views: 6055

Re: Measuring top and back frequencies while voicing

Yes, Brian tapes the back on and tests his guitars like that. But he has a few different steps to what's in "the book". You can see a pic of a taped on back here: http://brianburnsguitars.com/my-process (bottom of page). If my memory serves, he glues the bridge on before completing the finishing so ...
by Trevor Gore
Sun Apr 15, 2018 9:24 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Starting out on J45
Replies: 10
Views: 773

Re: Starting out on J45

I do all assembly at 45% RH. The sides can be problematic because they tend to be heat and damp tortured and then ignored. They are often assembled at unknown RH and, mostly, people seem to get away with it. I tend to bend the sides early in the process and give them a week to normalise at 45% befor...
by Trevor Gore
Wed Apr 11, 2018 10:29 am
Forum: Instrument Builders Forum
Topic: Fingerboard Finish
Replies: 7
Views: 566

Re: Fingerboard Finish

There's a brief mention, penultimate paragraph, Build p 23-2. For rosewood or ebony, oil, preferably a drying one, used very sparingly. Some of the the non-drying ones just penetrate for ever and there is no telling where they will migrate to.
by Trevor Gore
Tue Apr 10, 2018 9:35 pm
Forum: Instrument Builders Forum
Topic: Trevor Gore interview by Matthew Ottley
Replies: 1
Views: 314

Trevor Gore interview by Matthew Ottley

It can be somewhat disconcerting when an acoustics professional gets in touch asking for an interview. But Matthew Ottley , as well as being an acoustics professional, is also one of us; he builds guitars. So I thought, "Why not?" Matthew visited me at The Shed and we talked for over an hour about a...
by Trevor Gore
Tue Apr 10, 2018 11:57 am
Forum: Instrument Builders Forum
Topic: Cutting 1mm slots / rings for rosettes
Replies: 15
Views: 940

Re: Cutting 1mm slots / rings for rosettes

Trevor you mention third party high quality collets for the dewalt routers you use. A quick search doesn’t give an obvious supplier. Without getting too commercial where should we be looking - the cnc tooling people perhaps...? I was surprised to see the specs of such devices, the best are seriousl...
by Trevor Gore
Sun Apr 08, 2018 1:01 pm
Forum: Instrument Builders Forum
Topic: Stewmac Rosette soundhole cutter jig
Replies: 16
Views: 962

Re: Stewmac Rosette soundhole cutter jig

blackalex1952 wrote:
Sun Apr 08, 2018 10:32 am
Trevor Gore...Where do you get the precision aftermarket collets and bits? Ross
Precise Bits
by Trevor Gore
Sun Apr 08, 2018 12:50 pm
Forum: Instrument Builders Forum
Topic: tone
Replies: 5
Views: 469

Re: tone

Hello all i picked up an old guitar Electric and the E low is a quarter tone lower than the fretted notes. or if you like... all the frets are a quarter tone higher than the open low E. all other strings are good. I figure i need a new bridge. Any help or suggestions would be greatly appreciated. :...
by Trevor Gore
Sat Apr 07, 2018 10:49 am
Forum: Instrument Builders Forum
Topic: Cutting 1mm slots / rings for rosettes
Replies: 15
Views: 940

Re: Cutting 1mm slots / rings for rosettes

For precision results, it helps a lot to have precision tooling. Over the years, as I been asked to do more interesting rosettes, I've had to develop the tooling accordingly. I use De Walt routers with precision aftermarket collets and bits. I use a much larger diameter pivot than is typical. Mine i...
by Trevor Gore
Fri Mar 23, 2018 9:17 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Plastic Hinges a warning
Replies: 2
Views: 445

Re: Plastic Hinges a warning

Thanks for the warning, Dave. It's definitely worth taking a close look at the specs of anything that's critical. For the hinges I used it was something like 50kg load bearing (per hinge) and a very high number of cycles. They were meant as substitute domestic door hinges and intended to last a few ...
by Trevor Gore
Wed Mar 21, 2018 9:17 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Prototype Gore Guitar Freq Request
Replies: 12
Views: 806

Re: Prototype Gore Guitar Freq Request

I've used King Billy Pine with an Elong of ~5GPa for all braces, using the dimensions given on the plans, and got strung guitars with a T(1,1)2 of 170Hz. Boxed not bound they come out ~190Hz. So whilst the redwood secondaries may contribute to the low T(1,1)2 you measured, I doubt that is the whole ...
by Trevor Gore
Tue Mar 20, 2018 2:52 pm
Forum: Instrument Builders Forum
Topic: Counter sinking bolts BO/BO fretboard extension
Replies: 13
Views: 1465

Re: Counter sinking bolts BO/BO fretboard extension

If you use this type of fastener, be sure to get the hardened ones. Most of the furniture grade ones aren't and the hex socket will round out if used a few times with a ball end hex wrench. This was the reason we moved to the M6 socket head cap screws, which have a larger socket and are normally har...
by Trevor Gore
Tue Mar 20, 2018 8:47 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Prototype Gore Guitar Freq Request
Replies: 12
Views: 806

Re: Prototype Gore Guitar Freq Request

Nothing jumps out from the picture. All I can think of that's left is the quality of the epoxy mix (were the proportions correct, was it mixed thoroughly, was it warm enough to cure properly, etc.?) And finally, how is the fit between the underside of the primaries and the bridge plate? Are they glu...
by Trevor Gore
Mon Mar 19, 2018 4:17 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Prototype Gore Guitar Freq Request
Replies: 12
Views: 806

Re: Prototype Gore Guitar Freq Request

OK, thanks Ron. The plot still looks a little raggedy, but much the same frequencies as last time. Why the T(1,1)2 is that low is hard to say. The plate properties and thickness prediction are exactly what I get in my spreadsheets. The braces are larger section than I use, but that should result in ...
by Trevor Gore
Sun Mar 18, 2018 11:01 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Prototype Gore Guitar Freq Request
Replies: 12
Views: 806

Re: Prototype Gore Guitar Freq Request

I am balancing the box on my desk in front of the microphone, and I am tapping around the bridge area (with the soundhole open and the bridge pin holes taped over). Does there appear to be an issue with my technique possibly? Possibly. Try holding the guitar as you would when playing it (or as clos...
by Trevor Gore
Sat Mar 17, 2018 1:07 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Prototype Gore Guitar Freq Request
Replies: 12
Views: 806

Re: Prototype Gore Guitar Freq Request

According to your chart, the T(1,1)2 is at ~175Hz, which I would consider too low at this stage of the game for a "normal" guitar. First thing is to check your measurement set-up for VA and associated hardware so that you are confident you are measuring correctly. If you are, you are likely to end u...
by Trevor Gore
Wed Mar 14, 2018 1:10 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Adjusting resonances fleta braced nylon
Replies: 2
Views: 290

Re: Adjusting resonances fleta braced nylon

Given a lot of assumptions about bridge mass etc., finishing and gluing a bridge on will bring you closer to a T(1,1)2 of 200Hz than 190Hz. Coming down to 190Hz will push the T(1,1) lower and you don't want to end up on 98 Hz (G), but you may be able to bring that back up again by altering the sound...
by Trevor Gore
Mon Mar 12, 2018 11:52 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Measuring Plate Frequencies
Replies: 5
Views: 452

Re: Measuring Plate Frequencies

The meter said 26 Hz. VA showed peaks at 26, 54, and 81 Hz. So is is safe to say Fl is actually 81Hz? Kevin, the VA screen shows those three frequencies and they are all close to integer multiples of 26Hz. It seems that your speaker is generating harmonics of the fundamental, which is not unusual, ...
by Trevor Gore
Sat Mar 10, 2018 10:36 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: falcate Failure with an unexpected result
Replies: 22
Views: 6015

Re: falcate Failure with an unexpected result

I'm not sure about the bond between new and cured epoxy but my guess would be that it is strong enough. I'm pretty sure there is a time window for applying epoxy over epoxy according to the WEST instructions, and I think it is pretty short (like not long after it's gelled). You might want to check ...