Australian/New Zealand Luthiers Forum

kiwigeo wrote: ↑

Thu Apr 17, 2025 7:39 am

Trevor...when is the glue proof edition of The Books coming out??

And what exactly were you doing to stick the pages together??

Maybe it's time to invest in Ed 3; but a warning, some of the pics are even more provocative!

Is there an appropriate way to use dynamic testing for such material? The good news is "Yes there is!" I once came across a formula on the web which gave the resonant frequency of trapezoidal section panels. The bad news is I have never been able to find that formula since! However, a regular trape...

...is elastic modulus the same as Flexural modulus in this use or is just closely related? Flexural modulus and elastic modulus tend to be the same in isotropic materials at small deflections. For larger deflections, as typical of bending tests, and non-isotropic materials (like wood) they tend to ...

To reduce a resonant frequency you can add mass or reduce stiffness To raise a resonant frequency you can add stiffness or reduce mass The mass of a brace is proportional to its height The stiffness of a beam (brace) is proportional to its height cubed (i.e double the height it is 8 times stiffer in...

It is possible to get comparative results, but you have to be very careful about how you do it. The problem with the static test is that the longer you leave the load on, the greater the deflection you get, due to the visco-elastic behaviour of wood, leaving you with a decision as to when to take th...

In fact here it is, the timber arrives tomorrow.... That looks remarkably like my bench! Having used mine for ~20 years, here's a few things to consider: Make both the bench vises double screw (the wide front vise will wrack too much on a single screw). One day, I'll make that change! Make at least...

Trevor will no doubt respond as he always does with his sagely advice and make it all look embarrassingly simple :? Ha! I just looked up one of my old engineering text books.... it took 119 pages of "background" before it could sensibly discuss shear stress in beams. That's why the detail is not in...

If you're following the book process (back on sides, then close the box with the top) you have the opportunity to tune the back B(1,1) resonance before gluing the top on. Make the main back brace a few millimeters taller than normal and don't scallop it. Glue the back on the sides and flush trim it....

You can make a jig up using drill bushings (and it looks like Nigel did exactly that). P1010087s.jpg The screw-in drill guide bushings came from Lee Valley Tools: https://www.leevalley.com/en-gb/search#q=Drill%20bushings&t=product-search-tab&sort=relevancy&layout=card&numberOfResults=25 One is made ...

I played around with the above kit to try and find a user friendly configuration for teaching purposes. I wasn’t altogether successful, but here’s what I did and some of you might figure out how to do things better (and let us all know about it!) First, I wasn’t totally convinced about the security ...

Because the Facmogu amp is so small, it will fit inside the speaker tube. P1010027cs.jpg It can be controlled via Bluetooth from VA on your PC, so access to the amp itself is not required. This installment shows you how to mount the amp in the speaker tube. The only external “hard” connection requir...

A minor clarification: Where I said... You should hear a 1kHz sine wave through your left computer speaker. If not, check that you have your speakers on in Windows and then check the “Dev” (for Device) tab on the initial VA screen. On the “Dev” tab select an appropriate output device. Hopefully that...

According to Google translate, Facmogu means "Send out mushrooms" :wink: This next part is about using the Sig Gen functions in Visual Analyser. There are many versions of Visual Analyser and most of the time I use one of the earliest versions (v 9.0.6) because it does what I want with least hassle....

OK, there weren't may suggestions there! But we'll move right along, anyway! Those of you who wanted to get into Chladni patterns but were daunted by the build complexity of the kit shown above, rejoice! There is a much simpler solution, versions of which many of you will have adopted already, namel...

I am re-visiting the DIY sig gen topic due to new hardware becoming available that looks very promising (having already tested it). What I am seeking now is a sig gen app (preferable for free, but not necessarily so) that will run on a PC where the frequency is continuously adjustable using a mouse ...

Yikes!!! I gave up using collet reducers many years ago, due to eccentricity issues. I never had an incident, but it always looked like one waiting to happen. I now only use routers where proper interchangeable collet sizes are available (primarily DeWalt (1/4", 6.00mm, 1/8") , Makita (1/4", 1/8"), ...

Thanks, Nigel and Allen.

Cheers, Trevor.

A question to both Nigel and Allen: Do you have any concerns regarding the longevity of CA as a finish? I ask because I finished an internal door knob with CA over a year ago, it gets handled multiple times a day and the finish is holding up fine. On the other hand, at the same time, I finished anot...

Double post, sorry.

Hi I'm chamfering 20x10 spruce using 'the book' method of screwing the brace to a rebated fixture and freehand routing on a table against the top bearing. It all seems a bit hazardous- the 1/2' router is a beast! Anyone got a better way apart from hand planing? thanks mac IMG_5081.jpeg The screw ho...

I've got one of those angle cube things. Mine's by iGaging. It doesn't have any "stickiness" like yours seems to have, though.

Three thoughts:
1) There's some damping going on that you may be able to adjust or switch off
2) You have a faulty gauge
3) That's just how it is with that brand

The reason for the 4mm thickness number is so that (across a variety of different species) you still have the ability to reduce it to your target. Looking through my EIR data, I have target thicknesses ranging from 3.1 mm (medium sized guitar, wood with high long-grain runout) down to 1.9mm (small b...

I am building a Gore/Gilet type SS (no cutaway but the more modern shoulder as in Drawing 4) I made the back braces as per the text 20mmx10mm gabled. And glued them in place. Now I notice on the drawings for a live back (Drawing 6), the back braces are 6.3x16. Drawing 6 is a composite drawing showi...

GregHolmberg wrote: ↑

Thu Jun 13, 2024 11:13 am

Is it telling me something about the guitar, or something about the rig?

Most likely the rig. The fewer moving parts (to minimise slop and backlash) and the lower the friction the better.

Good to hear, Wayne!