Small project

[Arthur V.]

Small project based on an L-30 (L-00) model, where I want to create the arched top using the bracing. Like working with a (flattop) radius dish, but also with a recurve. What do you call such a thing? Tension-arched? Or brace-arched?



Already started making the mold



And bending some maple..

[citizenk74]

Small project based on an L-30 (L-00) model, where I want to create the arched top using the bracing. Like working with a (flattop) radius dish, but also with a recurve. What do you call such a thing? Tension-arched? Or brace-arched?



Already started making the mold



And bending some maple..

[Arthur V.]

Some progress on the sides



And back of the guitar



Braces and back strip are glued into a 15 foot radius dish

[Arthur V.]

Soon I will have to make a choice..




What do you think?

[nevershouldhavesoldit]

A. Less is more.

[sgosnell]

I like either A or B, but certainly not C.

[ruger9]

A.

[Arthur V.]

Thanks.



But still searching..

[thelostboss]

I will say that either of D or E look better to me than the previous versions. You need to think about which one you can replicate precisely on both upper and lower bouts. No point in having a beautiful f-hole that is asymmetrical across the body! [I know opinions vary about this but I am a traditionalist to that extent]

I should also say that to my eye D looks like something that could be punched out by a press in a metal-body resophonic while E looks like it might have needed some human intervention.

[Arthur V.]

Two old pieces of Sitka glued together. AA grade, fine grain but with some discoloration, which shouldn't be a problem as I intend to give this guitar an 'ebony finish'



In the meantime also made an 'arched dish', the layers of the plywood are a useful parameter for shaping the curvature.

[Scott Beckwith]

E for me, second to B. A is very nice and minimalist, but at least on the body shown, is too much straight angle to my eye. A very pleasing F hole for the right set of curves and finish, though.

[Arthur V.]

The choice has become E, Scott..



I thought long and hard about how I would shape the bracing.





After a few tests I try it like this:



Laminated beams





Planed flat



And a solid beam on top..



According to calculations there will be something like 20 kilos of downward pressure on the bridge. Hopefully this is strong enough..

[Arthur V.]

Top and sides glued together



Then I made a kind of primitive measurement setup



So that it can be determined how the top reacts under the downward string pressure



First try with a weight of 10 kilos..



That gives a difference of 0.5 millimeters



With another 10 kilos we are at the calculated downward pressure of 20 kilos



Add another half millimeter. At 20 kilos, the top goes down 1 millimeter..

I doubt if I want to make the braces much lighter..

[sgosnell]

I would be very surprised to find that the downward pressure from a set of strings is 20 kg.

[Arthur V.]

For the calculation I used a set of strings .013 - .056, such as this one:




648 mm scale length = just over 81 kg string tension, with a string break angle of 14 degrees.

With this information you can get started here: https://www.liutaiomottola.com/formulae/downforce.htm

As a result I get 19,74 kg downward pressure..

[citizenk74]

This is mesmerizing! More, please, at your convenience!

[Arthur V.]

Measure neck angle:



For certain reasons, I want a detachable neck with this one.
First off, I don't like truss rod covers, so the truss rod will be accessible through the heel of the neck.
Second, finishing a guitar is much easier when the neck and body are separate.
So, before the box closes, something has to be prepared..











And because of the f holes, the access to the bolt is visible in the heel

[sgosnell]

I don't understand how the truss rod adjustment is going to be accessed. Will you have to remove the neck to adjust it? If so, how will you know how much adjustment to make? Perhaps I'm confused. Bolt-on necks have been used on archtops before, but the truss rod adjustment is different on the ones I've seen. Just curious.

[Filmosound 621]

^^ Gibson did that in the late 30's, to guitars like the L-50, if I am not mistaken.

neck has to be removed from the guitar body for trussrod adjustments, the nut from the trussrod is "hidden"

in the heel of the neck.

[Arthur V.]

The neck must be removed to adjust the truss rod, indeed.
I've built already a few guitars -especially resonators (detachable neck with a neck stick) and almost all of them with a truss rod access through the heel - and in all honesty: until now I have rarely had to adjust a truss rod..

[sgosnell]

The necessity for truss rod adjustment depends on a lot of things, one of the more influential being the action you prefer. Higher action needs little or no adjustment, very low action can require it more frequently. Higher action seems more common on purely acoustic instruments. I do not mean to be critical at all, just curious about the construction techniques. I like to learn something every day.

[AllanAllen]

Plenty of fenders have truss rod adjustment at the heel. You have the take the stupid neck off to do it. So I just play them with a bow until I can't stand it. Usually takes my bass 3 years before it's unplayable.

[sgosnell]

I understood that the Fenders could be adjusted with the neck in place. I haven't really looked lately, though, and I'm thinking of solids. I know nothing of Fender hollow-bodies. Several other flat-top models have truss rods that can be adjusted from the end of the neck, inside the body. That's not easy, if even possible, with f holes though. Again, not trying to be argumentative, just curious. It's your guitar and you can certainly build it however you want.

[Arthur V.]

A truss rod mainly determines the relief of the neck, which also slightly influences the action, you're right, sgosnell.
I always adjust that relief to the minimum and when I want to determine the action I start working with the bridge. And that is very easy with a regular archtop bridge.

[sgosnell]

Yes, I know how to adjust an archtop. I just meant that the higher the action, the less the relief adjustment will be needed. I think that players who never need to adjust the truss rod tend to prefer higher action, and those who need more frequent adjustment prefer lower action. Neither is wrong, it's just personal preference and playing style.