Search found 195 matches

by Craig Bumgarner
Wed Jan 14, 2015 12:02 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Tape on the back for testing
Replies: 5
Views: 7314

Re: Tape on the back for testing

Thanks for the uncrossing the wires! I'll let you know how it goes.
by Craig Bumgarner
Tue Jan 13, 2015 12:22 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Tape on the back for testing
Replies: 5
Views: 7314

Re: Tape on the back for testing

Compared to removing a glued on back for adjustments, I don't think the time issue will be significant for you! You must be better at it than I. My backs are laminated and the hot knife tends to wonder into the first laminate (mahogany) and splits the laminate in places. Makes more a mess of it tha...
by Craig Bumgarner
Sun Jan 11, 2015 10:04 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Tape on the back for testing
Replies: 5
Views: 7314

Tape on the back for testing

In a recent thread, Jeff (jeffhigh) mentioned: "I could do like Brian Burns and tape the back on, glue on the bridge, test and modify." Does that actually work? Is the connection to the sides solid enough with tape to get a reliable test of the closed box? I glue my tops to the sides first so I can ...
by Craig Bumgarner
Wed Dec 10, 2014 6:25 am
Forum: Instrument Builders Forum
Topic: New Luthier Tips du Jour video - Accelerating break in
Replies: 27
Views: 28997

Re: New Luthier Tips du Jour video - Accelerating break in

Speaking of breaking in guitars, opening up, etc. and numbers & FRC, has anyone done such a study for instruments that have been played in naturally? Since I've started keeping deflection and FRC plots I've looked at maybe three of my guitars and one of a another builder, a couple years after they w...
by Craig Bumgarner
Wed Nov 26, 2014 6:20 am
Forum: Instrument Builders Forum
Topic: Controlling humidity on a budget
Replies: 5
Views: 7270

Re: Controlling humidity on a budget

For what it's worth, I use a cheap dehumidifier in the summer and a misting humidfier in the winter. I have a gauge in the shop and control the humidity devices manually. I probably have $150 US invested in the humidifier, dehumidifier and gauge. My shop is ~ 300 sq. ft, heated by base board electri...
by Craig Bumgarner
Sat Nov 15, 2014 9:45 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Simulating stiffer back, closed box
Replies: 10
Views: 11766

Re: Simulating stiffer back, closed box

A number of the French vintage gypsy guitars had soft backs, molded (laminated) to a dish or violin back shape, some with only one or no braces at all. Soft being a back with B(1,1) lower than T(1,1)2. Deflection under a 1kg load can be over 0.30mm! The result is usually light weight, high volume, q...
by Craig Bumgarner
Sat Nov 15, 2014 11:50 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Simulating stiffer back, closed box
Replies: 10
Views: 11766

Re: Simulating stiffer back, closed box

Right, I had a 7x18mm ladder brace at the max width of the lower bout already. Molded archtop like backs with a single brace were used on some vintage French gypsy guitars. This was my first go at it and I misjudged the stiffness. I thought the shape would lend more stiffness, but it was less than I...
by Craig Bumgarner
Sat Nov 15, 2014 12:48 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Simulating stiffer back, closed box
Replies: 10
Views: 11766

Re: Simulating stiffer back, closed box

Here's what I ended up doing. Epoxy filled the back until the grain was fully filled and smooth. Then glued a couple pieces of scrape 4mm cedar top material to the back with five minute epoxy. The laminated back is the first I've made with an violin back shape. I thought with the shape and one brace...
by Craig Bumgarner
Thu Nov 13, 2014 7:13 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Simulating stiffer back, closed box
Replies: 10
Views: 11766

Re: Simulating stiffer back, closed box

Would holding the box down on a solid surface with some padding take the back out of the picture? I know not ideal but not hard to do. It might, holding the guitar tight to the body does deaden the back some, but I don't want to take the back out of the picture, I want it in the picture, only stiff...
by Craig Bumgarner
Thu Nov 13, 2014 12:49 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Simulating stiffer back, closed box
Replies: 10
Views: 11766

Re: Simulating stiffer back, closed box

For simulation purposes, with an unfinished guitar you can glue braces on the outside and shave and trim at will, then remove all traces and finish the guitar. That what I've been thinking too. My backs are laminated with 0.5mm veneers so I have to be a little careful, no room for glue staining, bu...
by Craig Bumgarner
Wed Nov 12, 2014 9:24 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Identifying a peak
Replies: 5
Views: 7736

Re: Identifying a peak

Just did the obvious test of setting the Bradley to 200.00 hz and using VA to read it, exactly the same, so it must be my technique. Thanks,
by Craig Bumgarner
Wed Nov 12, 2014 8:31 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Identifying a peak
Replies: 5
Views: 7736

Re: Identifying a peak

Thanks for the reply. Yes, I think a long dipole on the back in this range is a possibility. Before I wrote the OP, I ran a Chladni on the back around 245hz and got a rather weak long dipole. The back has three ladder braces, so a weak dipole is not so surprising I guess. This was before your reply ...
by Craig Bumgarner
Tue Nov 11, 2014 7:17 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Identifying a peak
Replies: 5
Views: 7736

Re: Identifying a peak

Another thought, if this peak at 244hz is a monopole of some sort, I guess I would have expected the frequency of this peak at 244hz to have risen with the removal of bridge mass (~ 11gr), but this did not happen like it does with T(1,1)2 This lack of change seems to reinforce the idea that 244hz is...
by Craig Bumgarner
Tue Nov 11, 2014 6:13 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Identifying a peak
Replies: 5
Views: 7736

Identifying a peak

I wonder if anyone can help me identify the peak at 244hz. Here is a screen shot of the FRC in VA for taps the coupled top, fully strung. It's a good sounding guitar, so worth figuring out. FRC.jpg At 203hz is the T(1,1)2 and at 226hz is what I'm pretty sure is the back. IMG_4062 (Copy).JPG IMG_4065...
by Craig Bumgarner
Tue Nov 11, 2014 12:53 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Simulating stiffer back, closed box
Replies: 10
Views: 11766

Simulating stiffer back, closed box

Any thoughts on simulating a stiffer back on a closed box? Adding mass simulates less stiffness, but what about stiffer? My case is complicated by a soundhole which is too small to get a hand through, so it is unlikely that I can make a permanent change to the guitar but I wonder if there are non-de...
by Craig Bumgarner
Tue Oct 28, 2014 1:16 am
Forum: Health and Safety
Topic: Hot glue from the Hot Glue gun
Replies: 7
Views: 27465

Re: Hot glue from the Hot Glue gun

I worked in a small furniture factory in my youth and one of my jobs was spraying lacquer. One day, the gun kept plugging up and the foreman said "let me take a look at it". He loaded the gun with lacquer thinner, looked right at the nozzle and pulled the trigger. On the way to the hospital, he told...
by Craig Bumgarner
Tue Oct 21, 2014 10:50 pm
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Trevor's course
Replies: 7
Views: 10191

Re: Trevor's course

Just wondering, does Trevor ever come to the US and give such a course? I think he (you) have in the past, wonder if anything is on the horizon for the future.
by Craig Bumgarner
Wed Oct 15, 2014 11:03 pm
Forum: Instrument Builders Forum
Topic: Bending Brazilian Lacewood sides
Replies: 11
Views: 12781

Re: Bending Brazilian Lacewood sides

I'll second the SuperSoft II idea. It is the only way I've been able to bend 2mm thick curly maple bindings in the tight cutaway radii without breaking them. The grain of the curly maple I was using ran from one side to the other in less than 10mm. I have since used SuperSoft II on rosewood veneers ...
by Craig Bumgarner
Wed Oct 08, 2014 2:26 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Clarity
Replies: 2
Views: 4680

Re: Clarity

Thanks Trevor. I reread the sections on tonal characteristics including Attack and Separation. Yeah, there is a lot there that applies. Your comments about the nature of the Selmac is right on. Lots to think about.
by Craig Bumgarner
Fri Oct 03, 2014 12:42 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Clarity
Replies: 2
Views: 4680

Clarity

Clarity is an attribute I value in an acoustic jazz guitar, especially when being driven hard & fast with a pic, especially in the chords. Anyone have thoughts on what the handles are on this, particularly in the lower register, say below 300-400hz.
by Craig Bumgarner
Wed Apr 30, 2014 11:50 pm
Forum: Instrument Builders Forum
Topic: Implications of socketing braces
Replies: 15
Views: 14563

Re: Implications of socketing braces

Thanks for you ideas guys. I too have seen brace ends coming through the sides on some vintage guitars. My take on this is when in a dry environment, the grain of the top and the brace are 90 degrees opposed. As wood shrinks more across the grain than with the grain, if dried out, the top plate shri...
by Craig Bumgarner
Wed Apr 30, 2014 1:22 am
Forum: Instrument Builders Forum
Topic: Implications of socketing braces
Replies: 15
Views: 14563

Implications of socketing braces

I'm wondering about the implications of socketing brace ends in the linings. In all the good examples of the kind of guitar I build, the bracing scheme is ladder bracing with any where from three to five braces. The ends are always socketed. In other guitar styles, many of the braces are not. What h...
by Craig Bumgarner
Tue Apr 15, 2014 4:18 am
Forum: Contemporary Acoustic Guitar Design and Build - Trevor Gore
Topic: Fretting about fretting
Replies: 5
Views: 7119

Re: Fretting about fretting

For better or worse, I do not glue the frets during installation for the same reasons you mention. I shoot some CA down the slot from both ends after I have dressed the fret ends. I press my frets because I feel it gives a much more accurate set, but I know my little bench drill less is not up to jo...
by Craig Bumgarner
Fri Apr 11, 2014 6:26 am
Forum: Instrument Builders Forum
Topic: What glue bonds best to Titebond?
Replies: 6
Views: 7238

Re: What glue bonds best to Titebond?

Ha, ha, that's funny as that is what I've done in the past, heat it up and reclamp it. I subsequently read how that "doesn't work" and believed it instead of trusting my own experience. Lesson learned.....again 8) Thanks for all the ideas.
by Craig Bumgarner
Wed Apr 09, 2014 10:23 pm
Forum: Instrument Builders Forum
Topic: What glue bonds best to Titebond?
Replies: 6
Views: 7238

Re: What glue bonds best to Titebond?

Thanks for the reply. Timber, but not removed, just a thin gap about an inch long, so cleaning the joint well was not possible. I ended up using a very thin knife blade to do what I could, warmed it up enough to be flexible, filled the gap with thin CA and clamped and let set for an hour. Seems to b...