Australian/New Zealand Luthiers Forum

I occasionally see guitars with Koa tops though I have never played one. They look interesting enough visually, but as Koa's stiffness to weight ratio is close to half of spruce or cedar, I can't imagine it would be as responsive. If it is, I have a whole lot of thinking to do. I ask because I recen...

Thanks for this. Looks very simple, just what I (we) need..... except I'm on windows. I can wait for the Windows version of the Sinegenx, but what sweepable tone generators for Windows might be available now. I have NCH Tone Generator, but it was a trial version and expired. Before I buy it ($30 for...

Interesting thread! I build Selmer style guitars and one of the main characteristics is the arched top and "pliage" (fold) at the bridge area. The purpose is for the same reason other guitars use arched, domes, cylinders, etc., to provide more stiffness with less weight. Selmer style guitars have ab...

Okay, I got it figured out. Software: NCH Tone Generator, free download, ordered a cheap power amp and speaker. I'll be reading the tea leaves within the week and hope to figure out what those pesky peaks really are.

Trevor, I was writing my previous post when you posted, so mine went up after yours and without reading yours. Thanks to both you and Jim for your explanations, they are very helpful. I'll have to mull over that bit about back & top coupling some, but I get the general idea, thanks. Yes, Chladni pat...

I've been thinking about this overnight and figured if the stiffness is about where I want it, then mass is the next major thing I have to play with. This morning, I added 71 grams to the bridge area with magnets. This dropped the un-coupled top from 258 to 180Hz. The weight was chosen at random, an...

I'm Ba-ack! :twisted: Sorry to be a pest, but I've got a couple questions about MM and target monopole peak resonance frequency. If I may..... What is the basis for target monopole peak resonance frequencies? Good examples? From what I understand, which, granted, isn't much, the higher the frequency...

I've had good luck with a coat or two of oil based varnish like Z-Spar's Captains or Epiphanes to seal and provide a base, and then finish with FP. Holds up well, plays great. Straight varnish works good too. Without the varnish base, the FP has worn through on at least one well played guitar, but i...

A picture or two might help.

Very interesting Craig A couple of questions Were they all small mouth long scale? The Grand Busato has a wider body? any others non standard width? Were you able to observe any variations to the top and back bracing? cheers Jeff Sound holes: The Joseph DiMauro (the elder) guitar has what is referr...

Okay, here is most of what I collected on twelve Selmer style guitars at the recent Django in June festival in Northampton, Mass. Five of these were guitars I had built (CB) and brought to the festival. Mobility, et.al spreadsheet.jpg Some notes: My subjective rating, first column, is indeed very su...

Maybe a better DI would help. I see they make them in .001 mm calibrations, albeit more expensive. I'm going to check next week to see if what I interpret as internal variance in DI is so or still a function of play in the mounting of all the parts.

Yes, that about how I do it too. I notice when I load the first couple times, recovery of the DI is .01 to .02mm short of zero. I reset zero and keep doing it in fairly quick succession, and take the average. Usually the end, I'm getting minimum differences and the measurements seem consistent. I us...

I hope I can get my testing rig calibrated so we can compare apples to apples. It seems we need a "standard" for our deflection rigs. Maybe a known material of specific size and thickness supported in an exact way would produce a constant result and we could all do this to set up our rigs. Maybe I c...

Jeff, I knew nothing about specific mobility when I started building Selmac or even a good way to measure just stiffness on a completed top. Like most builders, I overbuilt. In order to get a handle on simple stiffness, I started deflection testing good examples. This showed right away that mine wer...

I ran the same deflection and Frequency Response Curves I've been using on the Selmacs on my Japanese made 1970 Cortley, a copy of the popular Gibson Hummingbird dreadnaught. Solid spruce top, solid mahogany b/s. Here is what I get: Deflection under 1.0Kg: 0.13mm (a little less than most better Selm...

Thanks for your thoughts on this. Sorry, but what is MM (Main Monopole resonance?) Otherwise, I think I'm following what you are saying. I suppose I would need Chilani patterns to determine the size of the monopole, something I have not done, but a logical next step any way as I have no idea what th...

Hmmm. What thickness are you using, Craig? I thought that you'd have to be using thinner than normally used on a flat top to get the mobility figures you get, which would mean a reduction in the parameter f . I've been using cedar for the last 18 months and the five guitars built in this period had...

Jeff, Right, I figure I will have to come with my own parameter as a steel string flat top is quite different than a Selmac with the domed top, ladder bracing, floating bridge and tailpiece. To get thicknesses like I am used to using, I actually had to increase the parameter to around 85. Maybe I'm ...

Okay, thanks, that all seems reasonable. I said I understood 4.5.2, but I do wonder how you arrive at the Predicted Panel Mass, last column in Table 4.5-3. If this simply the finished dimension on the rectangular panel that will make up the guitar, then I must be doing something wrong. Is there a ca...

I understand section 4.5.2 and it seems great to have a way to quantify top wood, but how is this used by a limited production luthier in the real world? More specifically, how does one use it to obtain top wood capable of "world class guitars". I can't quite picture asking my supplier to run top se...

I must admit I spend what I think is an inordinate amount of time finishing. Typically 16 hours from pore filling to final buffing. I pore fill the b/s and neck twice with troweled epoxy, varnish seal the cedar top, no stains, spray 5 coats of KTM9 one day, sand out and 5 more coats the next, a week...

Okay, here's my Mark II version based on a lot of the ideas presented here. Weight on the indicator shaft, support for the indicator is on the guitar edges. I can't even get close to being stable enough to get accurate reading without clamping it, but clamping is easy and eases my mind. Wider bases ...

Thanks Tom. I guess what I am picturing is the platform teetering on the shaft if the load is not carefully centered. The upper shaft on my indicator is only 5.6mm long and and 5.5mm in diameter, doesn't seem like much purchase.

Some times my old brain takes a while to engage. Have been a machinist years ago and one had to be sure your dial was on a ridged support. I looked at your picture and seen the weight but said to myself" the weight is going to bend the arm the dial is mounted on". DAH :oops: One does have to keep o...