Birds Beak Joint and a New Project

[Aaron Foster]

I am wrapping up a few things on ongoing projects (and trying to get my fingers back in some semblance of playing shape to demo the little size 0 I strung up a few weeks ago), but before I spray the latest guitar that I put on here before taking a little shop break I couldn't wait to get some design work in on the next.

For this guitar I am working through some design changes that I have been bouncing around in my head for a while. Somewhat motivated by aesthetics, somewhat by "professional development," but mostly these changes are motivated because I think they will make a better guitar. At least what better guitar means to me...

First up, I wanted to finally tackle a bridle joint headstock, or the maybe more accuratly described, the birds beak joint. I modified the joint from what I found online ever so slightly to maximize long grain in the volute while being able to accommodate a thicker headstock. I also prefer a headstock access truss rod and wanted to see how strong the joint would be with a truss rod slot. It also seemed like a good idea to try the joint once before diving into a guitar necessitating it.

Thankfully way back when I was in woodworking school I came out to the dumpster just after the abandoned projects of many students were disposed of, and amongst the things I too enthusiastically grabbed was a steel string neck, partially built, slotted for a headstock access truss rod, which I have not know what to do with since that day.


I cut off the scarfed headstock and a portion of the neck the router had made a mess of and made the new head stock from some sapele I had laying around from a previous build.





The joint is about 95 percent fit currently, just in need of a little tweaking. I'd like to carve it up as though it were an actual neck, put a little wood on as a fret board, veneer the headstock face and then I think I want to break it or at least test the strength.

I have been trying to think of what method of stressing the neck would most closely emulate how headstocks break in the real world. I would assume a sharp blow to the back of the headstock, but if I nail it with a hammer I have no way to measure the force that is not subjective. I am not totally sold on breaking the joint, but how often does one have a neck joint that is just asking to be tested to failure? any thoughts on methods or considerations are most welcome.

[Bruce Sexauer]

Since around 1945 it has been pointless to design guitar necks to withstand abuse, IMO, and instead I have focused on designing them to do their intended job For the length a human lifespan.

In case no one asks why 1945, I will tell the punchline now: Hiroshima/Nagasaki, there is always a bigger hammer.

[Aaron Foster]

Originally Posted by Bruce Sexauer

Since around 1945 it has been pointless to design guitar necks to withstand abuse, IMO, and instead I have focused on designing them to do their intended job For the length a human lifespan.

In case no one asks why 1945, I will tell the punchline now: Hiroshima/Nagasaki, there is always a bigger hammer.

While we may all be destined to fall under the hammer of nuclear holocaust someday, I'm not sure the everything turns to dust reality makes me want to limit the scope of potential neck design.

In practical terms the two piece neck lets me make do with less neck blank length on this current project, if you want to get out of longevity/durability/craftsmanship/aesthetics arguments.



since the stream doesn't seem to want to work, I will direct you to the thoughts of alvy singer...
https://youtu.be/24O7p6JZSh4

[Bruce Sexauer]

About 1/3 of my guitars in the last couple of years use a bridal joint, and I really enjoy making them. Not so sure they are stronger, but bet they are as strong as the one piece that is my standard.

Looks like a 9/1/2 on your bench, my go to plane.

[charles Tauber]

Originally Posted by Aaron Foster

I am not totally sold on breaking the joint, but how often does one have a neck joint that is just asking to be tested to failure? any thoughts on methods or considerations are most welcome.

Looks like a nicely executed joint.

Necks/heads usually break due to sudden impact rather than due to sustained static loading.

Failure due to a static load is pretty straight forward to test. You simply gradually add weight until the neck fails.

Impact loading is a little more difficult. Often guitars are dropped on their heads, breaking the head, or they are dropped while in a case causing a whiplash type loading that breaks the head. You could simulate those by fixing the position of the neck and then dropping a known weight a known distance, then incrementally increase the weight or distance until it fails. Without some baseline, however, the value(s) that you get won't tell you much - nothing to compare them to.

[Aaron Foster]

Originally Posted by Bruce Sexauer

About 1/3 of my guitars in the last couple of years use a bridal joint, and I really enjoy making them. Not so sure they are stronger, but bet they are as strong as the one piece that is my standard.

Looks like a 9/1/2 on your bench, my go to plane.

it's probably close, but that plane is a woodriver copy/interpretation. I like it except that it seems to lose an edge on the quicker side.

I am also not sure that the bridle is stronger than the scarf I normally do, I feel confident that it is strong enough however. I am curious how it will break, but most of the reason I am tackling this now is for reasons outside of strength.

My interest in testing the joint to failure is partially just having fun and partially to see where the joint fails. I looked around online and didn't see much about how they fail, searching mostly turns up stories about v joints failing at the glue line and being a cinch to repair...

[Aaron Foster]

Originally Posted by charles Tauber

Looks like a nicely executed joint.

Necks/heads usually break due to sudden impact rather than due to sustained static loading.

Failure due to a static load is pretty straight forward to test. You simply gradually add weight until the neck fails.

Impact loading is a little more difficult. Often guitars are dropped on their heads, breaking the head, or they are dropped while in a case causing a whiplash type loading that breaks the head. You could simulate those by fixing the position of the neck and then dropping a known weight a known distance, then incrementally increase the weight or distance until it fails. Without some baseline, however, the value(s) that you get won't tell you much - nothing to compare them to.

That was my thought as well about failure. I don't want to build a whole guitar to drop with this let along a second to stand as the control (or dozens of each for accuracy), and I wonder if the stubby quality of the mock neck would compromise a deeply scientific test anyway... still I feel like I should entertain more precise means than just whacking it with a hammer. Or maybe not.

[Bruce Sexauer]

If it is a replica 9 1/2, then there may be aftermarket blades available for it. I use a Hock blade in my favorite plane. It cost 4x what the Vintage plane cost, but it takes and holds a great edge.

[Aaron Foster]

I'll have to look into it. I have two irons for it right now and have been swapping them out, but eventually I am going to get around to toothing one of those.

[ruby50]

Wood River uses the vintage Stanley easy to use, low-angle blade depth adjustment strategy on all its block planes regardless of blade angle. They also use a copy of Stanley's 3 piece knuckle joint cap, which was an option on their block planes and turned a 9-1/2 into an 18. They never put that cap on their popular and much imitated 60-1/2 low angle block - it has a very narrow 1-3/8" blade - but only on some years of the wider 65. The one in the picture is Wood River's low angle version like the 60-1/2 and an excellent choice - try one out next time you are in a Woodcraft. I get excellent results from Stanley's standard blades.

S.O. Teric

[printer2]

Originally Posted by charles Tauber

Looks like a nicely executed joint.

Necks/heads usually break due to sudden impact rather than due to sustained static loading.

Failure due to a static load is pretty straight forward to test. You simply gradually add weight until the neck fails.

Impact loading is a little more difficult. Often guitars are dropped on their heads, breaking the head, or they are dropped while in a case causing a whiplash type loading that breaks the head. You could simulate those by fixing the position of the neck and then dropping a known weight a known distance, then incrementally increase the weight or distance until it fails. Without some baseline, however, the value(s) that you get won't tell you much - nothing to compare them to.

I used to work in a mechanical test lab. I used a hydraulic machine to increasingly load the sample in tension or compression until it broke. We had to test blades on occasion that were meant to cut through cables. We used a pendulum arrangement with a weight on the end. We raised it to a certain height and let it drop. With the weight and the height it was released you could figure out the force it hit with. Then there was the time we needed to load a hoist arm repeatedly for long term fatigue testing. I put together a hydraulic system to do it. Really cool when things actually work first time. The guys on the shop floor were not to impressed. "Ka-chunk, ka-chunk, ka-chunk...", about every 2-3 second. Seem to remember it going for about 750,000 cycles. We didn't break it, a good thing. A little understanding on the physical forces and how you can produce them can get you having fun breaking things.