Australian/New Zealand Luthiers Forum

If you look at the response of any structural system it will respond elastically until its plastic deformation limits are exceeded. My background was in residential architecture, engineering and construction for way too long... so I'm influenced by that. An underbuilt floor system of plywood and jo...

I also agree that stiffness changes, that is one of the reasons Trevor suggests a 3 meter dome for an active back. Able to get extra stiffness while keeping the back thin enough to have low mass. [/quote] I just glued up the back of my myrtle 0 rebuild last night, thinned down and radius decreased (...

Stiffness does not change with load. Stiffness is a constant. Deflection changes with load. Are we sure on that? Yes, load first causes deflection, which changes the location of the neutral axis in a beam (towards the fibers under compression), which I think we can presume happens with the soundboa...

I have a build going right now that I temporarily glued the bridge on using hide glue and masking tape. I put tape down on the top and glued the bridge to that. I'm not sure it really mimic's the stiffness due to the tape but the weights right and certainly has some stiffness and it was easy to do....

Recreating conditions for a fully strung up instrument without gluing the bridge on is difficult...that's the beauty of the allowance for trimming ...as already noted on a Gore build the bridge has significant stiffness. Ive found with most of the builds the shift in main top frequency with bridge ...

... I do check the resonances before I finish and glue on the bridge. This lets me know that I am in the range. At that point the only remediation I would do is thin the edges of the top if I think the resonances are too high. Hi John Thanks for your thoughts. Do you find the initial untensioned to...

My bodies and necks are built and finished entirely separate from each other than fitting the neck to match the fixed bridge location (length and sideways) before finishing. It would far more expeditious to also check the targeted values for an 0 guitar of 95 Air/180 Top/226 Back hz, coupled and unc...

I found it curious that a "reduction", per the Book where you noted we're "free" to use a lower stiffness value and hence thinner top, didn't result in a reduced thickness, Obviously that statement is incorrect... I don't know why it didn't come out correctly the first time, but at least it did upo...

I measured 9 top plates today and calculated targeted thicknesses for 343 mm wide 0 guitars. Adirondack, Engelmann, Lutz and Sitka. I look a random (I should have said INITIAL) 10% stiffness reduction considering the top width. If you're using the formulae in the books for the elastic constants, me...

I've just strung up a falcate braced parlour guitar Ive been working on for 2 years now. From memory the bracing dimensions were pretty much as per The Books. The guitar sounds loud and has more balls than any of my larger bodied builds. IMG_0648.jpg IMG_0904.jpg IMG_0921.jpg I imagine you're prett...

HI Trevor I suspected as much. I found it curious that a "reduction", per the Book where you noted we're "free" to use a lower stiffness value and hence thinner top, didn't result in a reduced thickness, which do seem to be thinner than I expected - which I though might be about 10% thinner than for...

Hi all I measured 9 top plates today and calculated targeted thicknesses for 343 mm wide 0 guitars. Adirondack, Engelmann, Lutz and Sitka. I look a random 10% stiffness reduction considering the top width. The consistency was remarkable considering the variety: Natural Tops targeted 1.76 to 1.89 mm ...

I've found the VA frequency meter a bit catankerous.....sometimes it works.....other times it doesn't seem to pick up a harmonic. I tried the frequency meter and it doesn't give a reading? Which is probably why I haven' got into using it...re my resonant figures from the board I sampled, the long s...

A big shout-out to seeaxe for helping me out. All good now!

Somewhat in defense of Roger, he did advocate tuning the top braces in a jig in order to replicate being glued to the sides... but this isn't horseshoes... A mandolin is much closer to a plucked violin than a guitar top, and focuses on a completely different sound spectrum, so different factors are ...

So I'm going to answer my own question, based on today's very interesting experiment, so nobody else has to spend the time to educate me. Since I've got VA all set, and before taking the backs off, I thought I could learn something by creating FRCs off my two unhappy guitars. Both air chambers T1,1,...

Yep, I did figure that out after some trial and error, but I've got an odd factor in there that's still throwing it off. I look forward to seeing Richard's which will clue me in.

Thanks!

Hi All I'm digesting The Book in pretty good detail and beginning the process of creating FRCs for some unhappy guitars in preparation to zip off the backs and rebrace to falcate with live backs (I use a removable tilt neck which has a huge advantage for radical re-dos), in order to learn what I can...

HI Richard thanks so much! I'm sure Trevor's a busy guy, to say the least, so having a working Excel sheet would expedite the process and I should be able to spot my error. oi@kgillies.com I REALLY appreciate it as I'm doing FRCs on some guitars I'm not sweet on which I will convert to falcate/live ...

Hi Thanks for your reply. If it were a matter of decimal places (m to mm), it would be easy enough to spot, but it's off by a bizarre factor, so it seems like it would be a metric to "standard" (we're stuck up here with that nonsense so I don't think naturally in metric) or other conversion issue. O...

Hi Math Heads I'm building an Excel sheet to start measuring a bunch of tops I have and calculate the target thickness h. Computer and tapping are all ready to go. I'm using all of TG's values from Table 4.5-3, and won't repeat them here. I'm good all the way through the first 12 columns (although h...

Hey Dave Yes, I caught that general sense in The Book, and it's probably not significant enough for Trevor to spend more thought or time analyzing the issue.... Onward. Hi Richard Yep, the only way to know is to try it out. I'm getting real close to pulling the back off an 0 guitar I'm not totally p...

Not yet, as I decided that the series of guitars I've been building with a modified X / bridgeplate are "constricted" in both lows and highs and just not good enough. I didn't need a spectrum analyzer to hear it, but assumed (AKA "make an ass out of me") it was do to the small 0 body size. Funny thi...

HI Richard Thanks for your thoughts. Looking at it solely as a vector force, I agree with you - you could think of it as partway towards a tailpiece setup. The concern I have is in looking at it from the perspective of the string pulling directly from a point further towards the tail might cause tha...

HI Martin Surprisingly, banging the top around while changing strings is not an issue with the change in pin location! It's super quick and simple. Far more damage is done by picks or fingernails! Or for that manner in radical changes in humidity, which is kind of brutal here on the edge of the dese...