Search found 1029 matches

by Alan Carruth
Sat Jan 16, 2021 5:40 pm
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Hemlock tops
Replies: 6
Views: 116

Re: Hemlock tops

I did test out one piece of Eastern hemlock once. It was dense, and not very stiff along the grain for it's density. I would not be surprised if it made a 'quiet' guitar.
by Alan Carruth
Fri Jan 15, 2021 1:31 pm
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Hemlock tops
Replies: 6
Views: 116

Re: Hemlock tops

I got two Western hemlock tops some time back, I don't even remember where. They were dense, and hard, but made up into good guitars. Those two, at least, were more or less 'on the line', iirc; that is, the Young's modulus along the grain was where you'd expect it to be given the density. If you tes...
by Alan Carruth
Tue Jan 12, 2021 7:07 pm
Forum: Glues and Finishes
Topic: Acoustic guitar Finishing advice
Replies: 34
Views: 1572

Re: Acoustic guitar Finishing advice

'How many coats' is a hard one to answer in general. It depends on three things mostly; the finish you're using, what result are your after, and how good your surface prep is. Tru-oil builds slowly so you will need more coats to get the same result. On the plus side, you don't have to wait too long ...
by Alan Carruth
Sun Jan 10, 2021 2:00 pm
Forum: Glues and Finishes
Topic: Titebond liquid hide glue
Replies: 8
Views: 150

Re: Titebond liquid hide glue

What they said. There are claims that it's fine when it's fresh, and so on. The problem I've had, and heard of from many others, is that it's unreliable in the long term. It seems particularly prone to softening with heat and humidity. The consensus is that it's not worth the risk in any structural ...
by Alan Carruth
Sun Jan 10, 2021 1:52 pm
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Sound hole placement...
Replies: 16
Views: 416

Re: Sound hole placement...

For a baritone you may well want to go with a smaller sound hole, to drop the 'air' pitch in line with the lower tuning. I've got a baritone that a customer gave back to me when he was no longer able to play it. He knew that it is one on my favorite guitars, so now I actually have one of my own to p...
by Alan Carruth
Sat Jan 09, 2021 1:04 pm
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Sound hole placement...
Replies: 16
Views: 416

Re: Sound hole placement...

A J200 Super Jumbo is a really large flat top in every respect. Is your guitar that big?
by Alan Carruth
Fri Jan 08, 2021 3:21 pm
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Sound hole placement...
Replies: 16
Views: 416

Re: Sound hole placement...

Traditional designs have been worked out so that everything ends up about where it should. Note that we're not always certain as to why those particular values are 'correct' but departing very far from them may end up producing something that doesn't sound the way it should. A lot of this is a matte...
by Alan Carruth
Thu Jan 07, 2021 12:25 pm
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Sound hole placement...
Replies: 16
Views: 416

Re: Sound hole placement...

"So a smaller hole gives more bass... " As usual, it's more complicated than that. Using a smaller hole lowers the pitch of the 'Helmholtz' air resonance, but also makes it weaker. Usually we notice the pitch change more, but, especially in extreme cases, the lack of power can catch up to you. A lot...
by Alan Carruth
Thu Jan 07, 2021 12:14 pm
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Almost consistently bad glue joints...
Replies: 16
Views: 283

Re: Almost consistently bad glue joints...

Wood changes dimension much less along the grain than across, so braces that are glued across the back are always under some stress from humidity changes, no matter what the wood. That's probably not your main issue. Research on glue lines in wood aircraft structures back in WW 2 showed that : 1) su...
by Alan Carruth
Tue Jan 05, 2021 7:05 pm
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Sound hole placement...
Replies: 16
Views: 416

Re: Sound hole placement...

There was a good article on 'The Basics of Air Resonance' by William Allen in American Lutherie #1; I'd strongly recommend it to anybody. My most recent archtop was intended as a reasonable 'tonal copy' of a Loar L-5 that the customer had tried out. I did get to check it out, obtaining an 'impulse s...
by Alan Carruth
Tue Jan 05, 2021 9:50 am
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Sound hole placement...
Replies: 16
Views: 416

Re: Sound hole placement...

This is one of those things that just 'falls out' as you satisfy other constraints, to some degree, and could well vary from one instrument to the next, depending on what you're after. You need to have 19 full frets. Twenty won't hurt, but you need nineteen. That establishes the location for the upp...
by Alan Carruth
Thu Dec 17, 2020 11:41 am
Forum: Glues and Finishes
Topic: Acoustic guitar Finishing advice
Replies: 34
Views: 1572

Re: Acoustic guitar Finishing advice

Sanding in an oil finish does work pretty well as a filler. Use something like #400 wet or dry paper. There will be a fair amount of shrinkage, and it will take some time: oils harden by oxidation and polymerization, and that goes a lot more slowly than solvent evaporation, particularly in thicker l...
by Alan Carruth
Thu Dec 17, 2020 11:37 am
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Triple O - Dovetail neck doesn't seat - Photos
Replies: 7
Views: 755

Re: Triple O - Dovetail neck doesn't seat - Photos

Good advice so far. Bob Gramman wrote: " It’s not hard. The major requirement is patience. " Another major requirement is a sharp chisel. This is one of the operations that embodies the 'kaon of lutherie': "The slower you work the quicker you get done". The idea behind chalk fitting is that the chal...
by Alan Carruth
Tue Dec 15, 2020 10:22 am
Forum: Glues and Finishes
Topic: Acoustic guitar Finishing advice
Replies: 34
Views: 1572

Re: Acoustic guitar Finishing advice

From what I've read going finer than 220 doesn't improve the wood surface; the sanding scratches are about the same size as the wood cells at that point. My experience bears that out. Finer paper has more of a tendency to clog on wood, which produces a worse surface. I like to dry sand between coats...
by Alan Carruth
Mon Dec 14, 2020 6:15 pm
Forum: Glues and Finishes
Topic: Acoustic guitar Finishing advice
Replies: 34
Views: 1572

Re: Acoustic guitar Finishing advice

Oils don't really 'clog' the wood, but they do have high damping, which tends to 'eat' the high frequencies. Straight 'boiled' linseed oil never really stops hardening, and shrinks as it does, which can cause problems, Nor does it form a water proof film. The low molecular weight components of most ...
by Alan Carruth
Tue Dec 08, 2020 8:06 pm
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Blank thickness for glue up
Replies: 9
Views: 934

Re: Blank thickness for glue up

One of my students once got a maple back that came in sanded to 2.6 mm thick. Since I like to make a back like that at 2.5 it didn't leave up much wiggle room. It took three tries to get it; fortunately it was wide enough. I do much of my thicknessing with a Wagner Safety Planer. Making them thinner...
by Alan Carruth
Mon Dec 07, 2020 3:04 pm
Forum: Tools and Jigs
Topic: Planning The Rosette Mosaic.
Replies: 3
Views: 3288

Re: Planning The Rosette Mosaic.

I just use 'Paintbrush' or some such raster program, and zoom in to single pixels. Once you have a tile that you think you might like you can copy and paste it, and zoom out to get the effect.
by Alan Carruth
Wed Nov 25, 2020 12:43 pm
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Very new guitar maker
Replies: 3
Views: 775

Re: Very new guitar maker

"Just roughing out violins can sometimes make the wood curl up like a potato chip." They'll do that to some extent if the humidity is changing fast: the surface has picked up or lost moisture but the inside hasn't had time to catch up. Most wood also has some level of built-in stress, which can be r...
by Alan Carruth
Tue Nov 24, 2020 9:52 am
Forum: Flat-Top Acoustic Guitars and Bass Guitars
Topic: Very new guitar maker
Replies: 3
Views: 775

Re: Very new guitar maker

The culprit was the humidity change. Wood changes dimension a lot across the grain with changes in humidity, but there's hardly any change in length along the grain. The braces running across the grain stayed the same length, while the top tried to get narrower in the lower humidity, so it went conc...
by Alan Carruth
Mon Nov 23, 2020 1:32 pm
Forum: Tools and Jigs
Topic: Materials for jig making.
Replies: 15
Views: 8865

Re: Materials for jig making.

One of the guitar tool suppliers uses transparent colored plexi for templates. The color and the 'glow' of the edges really helps locate them. He also color codes them: all the templates for one size are the same color, and others are different. The first time I saw that was a 'duh' moment. Plexi an...