Need a primer on designing a slot headstock.

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Need a primer on designing a slot headstock.

Postby Bryan Bear » Wed Jun 26, 2013 5:56 pm

I am in the process of making a neck for a tenor uke and just decided I might want a slot head, I have a few questions:
1) I’m using the Stew Mac geared uke tuners, they are meant for a regular peghead. Can I just turn them sideways? Ideally, I will design the head so that the strings use the existing hole (ends of the shaft are not buried in the other end of the slot), alternatively, I will drill a new string hole on the shaft.
2) I already did the scarf at 15ish degrees (before you ask, yes the peghead is currently still thick enough for side mounted tuners), is this too steep?
3) Most important of my questions: I have never done a slot head and since this is an uke, I don’t even have a set of plans to start from. Is there a good resource for order of operations when designing these things? I plan to just start drawing it out from all angles but sometimes things like this have pitfalls that aren’t immediately obvious to me. Tips on what to avoid are helpful. . .
PMoMC

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Re: Need a primer on designing a slot headstock.

Postby Michael Lewis » Thu Jun 27, 2013 1:28 am

Having made and dealt with slotted headstocks I can tell you that the string break angle can be severe, meaning lots of down pressure in the nut more friction, wear, tuning issues). Draw your neck on paper full size, especially from the side view and see where your strings want to go and how much headstock angle you really want. At this point I suggest you make it a solid headstock and make your next instrument with a well planned slotted headstock. Just my personal thoughts.
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Re: Need a primer on designing a slot headstock.

Postby Christ Kacoyannakis » Thu Jun 27, 2013 2:53 am

Greek bouzoukis (at least the four course ones) usually have slotted headstocks. I have seen everything from about 8 degrees to a full 15 degrees. A 15 degree headstock angle is what most seem to suggest. If you think about it, the solid headstock has the tuner posts sticking up, so the break angle is less than 15 degrees. With a slotted headstock, the tuners are in the middle of the headstock wood, so a 15 degree headstock angle would be a lot more than 15 degrees string break angle. I make my bouzouki headstocks between 11 and 12 degrees, and this seems to work out well.

Michael, is there a good way to cut and shape the ramp at the bottom of the slot? I use Chris Klumper's Luthiertools jig for cutting the slots, and they come out absolutely perfect every time, but I have a bear of a time on the ramps. The best method I have found so far is to use a Dremel tool with a cylindrical sanding attachment. Whenever I have tried round rasps the ramp never comes out well. Is there a better method?
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Re: Need a primer on designing a slot headstock.

Postby Arnt Rian » Thu Jun 27, 2013 3:36 am

As has been said, draw it all in top and side view, and all will become clear... :geek: I've seen some guitars (I realize this is a uke) with tuners meant for solid headstocks mounted as you suggest, where the shaft terminates inside the slot. To me, this seems like a poor design idea, as the only thing supporting the shaft will be the relatively thin wall outside the shaft. As I see it, the main practical benefit of a slot head, where the shaft spans the slot, is the very solid string anchor. If you use solid head tuners for this, even if the shafts are long enough, they may not be optimal if they have a concave profile. The angle of the strings will vary, as the angle of ones closest to the nut will be much steeper than the ones further away, but an average of about 15 degrees is good. That means the headstock angle must be flatter, how much you will see when you draw it.

Christ, I have the same routing jig as you. I use a rat tail rasp, file and sand paper wrapped around som round object to refine the ramps. I have some pictures here somewhere... Found them! OK, I posted this in a build thread over at another forum some years back, I make my necks a bit different now, but here's an edited version:


I start by putting some masking tape on the edges to avoid marring them, and then penciling in the lines for the ramps

Image




I cut most of the waste out with a chisel

Image





The rest is done with a rat tail (?) rasp

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So far so good

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Cleaning things up with a round file

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Voila!

Image
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Re: Need a primer on designing a slot headstock.

Postby Randy Cordle » Thu Jun 27, 2013 8:46 am

Bryan,
I'm currently slowly working toward putting a slot head tenor Uke together. I'm using the Grover Uke tuners, but I did an easy mod on the string posts to adapt them for slot head use. The modification details and photo are on my website on the "Uke" page, but you'll have to check my profile for the link as i don't think it's allowed to post it.
Lap steels, banjos, and mando family instruments for the world!
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Re: Need a primer on designing a slot headstock.

Postby Jon Whitney » Thu Jun 27, 2013 11:22 am

A couple of points to consider: Will the uke be strung with nylon or steel? Usually they are strung with nylon, and the peg heads are very thin by guitar standards. That means that mounting the uke pegs sideways in a slotted head, even when the tuner shaft cannot span to entire slot (meaning the shaft end won't be supported) will probably not be a problem, due largely to the low tension of nylon strings compared to steel. The higher break angle may be more of a problem but with a well crafted nut, it should be OK. There are plenty of historical and ethnic instuments with a much sharper break angle.

Bottom line: while you may not have the optimum tuners and break angle for a uke, I doubt you'll have any insurmountable problems with your idea. I've built several slot head banjos, including one that uses tuners that don't span the slot (and it has steel strings!), and haven't had any real problems.

In the interest of full disclosure, the steel-string banjo with tuners that don't span the slot is more of a peg box than a peg head - the back side is closed:
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Re: Need a primer on designing a slot headstock.

Postby Bryan Bear » Thu Jun 27, 2013 12:06 pm

Thanks for all the great input, keep it coming! I have a lot to consider. It sounds like there are a few things against me here but they MAY not be insurmountable. Jon, yes it will be nylon strings which is why I thought it might work out okay. Randy, that tuner conversion was really helpful. It may make this more feasible for me in that it would allow me to have the end of the shaft supported and the increase in post diameter will help to reduce the break angle.

I'm on the fence right now; I'll be following the suggestions closely.
PMoMC

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