Length Truss Rod for Parlor Guitar?

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Length Truss Rod for Parlor Guitar?

Postby Keith Walden » Fri Feb 01, 2019 11:29 pm

Ok, yea Im building without a plan, so please bare with me.

Need the length used for a truss rod in a Parlor guitar. I'm doing a copy of my Ibanez "cigar box" Parlor guitar. Same wood looks like a cigar box, some kind of Hog, ?? African? anyway...

Im getting a cheapi double action from China, its cheaper than making one and dealing with my time constraints. :) Tell me Im wrong not to do a single action.

Im getting a neck from (you know) that already has a truss channel cut, African Hog, (classical actually) so I can make the neck a bit wider but the neck on the parlor seems just perfect.
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Re: Length Truss Rod for Parlor Guitar?

Postby Brian Evans » Sat Feb 02, 2019 10:08 am

On a 14 fret guitar the truss rod can be around 1/2" - 3/4" longer than half scale length, and correspondingly shorter for a 12 fret guitar. You basically want the truss rod to stop at the heel, before the neck joint, and stick out the head far enough that you get a wrench in it. If the double action truss rod is made accurately and with good materials, I think they win every time over any single rod truss rod. It's good to have a "plan" - a basic idea of size and shape, and where stuff goes, but you don't need a blueprint detailed everything drawn out and dimensioned plan unless your process of building wants that. I have yet to draw a plan for a guitar - I draw the shape to let me make a mold, I draw a headstock so I can make a router template, but mostly I just build a guitar. Pile o'wood, make a lot of mess, shavings, dust, take away all the not-guitar bits and what you are left with is a guitar...
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Re: Length Truss Rod for Parlor Guitar?

Postby Clay Schaeffer » Sat Feb 02, 2019 10:58 am

It also doesn't hurt to draw a "profile" of the guitar as it helps show the lengths and off sets needed to make the guitar playable. Start with the string and nut and saddle location and draw everything in relation to those.
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Re: Length Truss Rod for Parlor Guitar?

Postby Steven Smith » Sat Feb 02, 2019 11:19 am

None of my guitars are "exactly" to plan. When I start a new one I tape freezer paper full length to the bench primarily to give me a clean surface to work on but also so I can lay out the basic geometry. By that I mean nut/saddle position, 12th fret, body joint, and neck width at nut/saddle/body join. I do a view below it to define exact headstock length/angle and length of dovetail or tenon. It usually takes me about an hour or less. It keeps me from guessing later and making critical errors (like one time I made the neck too short by forgetting to include the tenon length). Once I've done this it's a trivial task to determine the acceptable range of truss rod lengths that I can use. This is just how I do it.
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Re: Length Truss Rod for Parlor Guitar?

Postby Keith Walden » Sun Feb 03, 2019 3:58 pm

Ok, so I found a 16" with a Gibson style nut" Option. Which end is easiest to install to for adjustment?. Which end do you prefer? With a Chinese neck, Mahogany, Im thinking I would prefer soundhole adjustment. (?)
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Re: Length Truss Rod for Parlor Guitar?

Postby Brian Evans » Mon Feb 04, 2019 10:54 am

At the risk of sounding grumpy, a 16" truss rod will be about 4" longer than your neck (assuming a 25" or so scale length for a parlor guitar), and a Gibson style single action rod is about the oldest, and last, choice I would make. Double action rods like the Stewmac Hotrod are just so much more adjustable and far easier to install (you don't have to jig up to cut a curved bottom slot and make a matching curved insert to force the truss rod into a shallow curve down the neck). If you do a headstock install you just have to continue the channel cut into the headstock and clean it up a bit for clearance around the adjuster, if you do a soundhole install you have to cut a channel through the neck block for the adjusting wrench to stick in through, or get a truss rod with an extended adjusting end. You also have to stop the channel cut before you get to the end of the fretboard so the headstock is not cut.
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Re: Length Truss Rod for Parlor Guitar?

Postby Bryan Bear » Mon Feb 04, 2019 11:51 am

This is going to be difficult to piece together by mixing and matching parts. You really need to decide on one aspect first. Any neck you buy may or may not fit the trussrod you want to use. You may need to do some alterations to the trussrod slot to fit the width and depth of the rod. The length of the rod will depend on the length of the neck, which end you want to adjust on and what your neck joint will be. Every aspect will affect something else downstream.

Questions to consider:
12 fret neck or 14? I don't want to assume 12 just because it's a parlor.
scale length? This will need to match the neck length and what fret you want to meet the body on.
Neck joint type? You have to find a neck that is made for the joint you feel comfortable using or can be modified to do so.
peghead or soundhole adjust?
Truss rod slot? What size is the slot in the neck you want to use? Are you up to modifying it?
Which truss rod to use? get a handle on what the available rods are, which you like, what the dimensions are.

I would recommend keeping to the truss rods with a known track record. Nice truss rods are not too expensive so don't cheap out there. The Martin Guitar Maker's Connection offers their two way rods in 14 fret and 12 fret lengths (you may need to do some googling to locate them on the site). Stew mac lists dimensions of their rods on their site and you can look at the reviews.

Avoid the temptation to start buying parts without a plan. I don't mean a drawing/plan, I mean knowing what you want and how to accomplish the tasks involved. Otherwise, you will end up painting yourself into a corner and have to figure out how to make parts work.

Do you have experience making instruments? I would recommend reading in the library here, following online build tutorials, reading books and checking out the kit instructions on the StewMac website. All these things will help you form a notion of how everything goes together.
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Re: Length Truss Rod for Parlor Guitar?

Postby Keith Walden » Mon Feb 04, 2019 5:17 pm

Good info. Yes I did a build I need to finish, I need to put a back on, but will probably get opinions on it as I think the braces will be too thin...

I guess I will wait for my neck to arrive and go from there. :D

Im basing this off the little Ibanez Parlor guitar, so that is my ''plan'' more or less/

I may make it more ''dred'' by reducing the 'arches', curves, whatever they are called. but whatever the size I will make it as close as possible, neck will be wider and Its a classical neck, I will make it a bolt on, that will be fun. It has a truss channel, or it does in the picture so Im guessing it does, well see in a month or so. :)
I need to glue up a couple backs and a top, without going nuts. thats the biggest issue.
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Re: Length Truss Rod for Parlor Guitar?

Postby Peter Wilcox » Mon Feb 04, 2019 5:34 pm

Bryan Bear wrote:Avoid the temptation to start buying parts without a plan.


Good info from Bryan. I would add, don't start building without all the parts in hand (this is more for electrics than acoustics.) It's pretty aggravating when things don't fit together after you've spent months on a project.
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Re: Length Truss Rod for Parlor Guitar?

Postby Bryan Bear » Mon Feb 04, 2019 5:44 pm

Keith Walden wrote:Im basing this off the little Ibanez Parlor guitar, so that is my ''plan'' more or less/



That's part of the plan, knowing the size and shape you are after. The other part of the "plan" is what processes are you going to use to get there. There is a lot more to the geometry of an acoustic guitar than just bolting the neck on the body. There is neck angle, fretboard/fret height, bridge/saddle height, soundboard arch and any extra angle sanded into the upper bout of the rim. All these things combine to give you proper string height at the saddle with playable action while also having the fretboard extension down on the soundboard. You may have a handle on these parameters already, but I figured I'd point them out.
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Re: Length Truss Rod for Parlor Guitar?

Postby Keith Walden » Mon Feb 04, 2019 5:52 pm

Oh, yea, I will probably do a side view and top view with braces. Good idea thanks!!
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Re: Length Truss Rod for Parlor Guitar?

Postby Freeman Keller » Mon Feb 04, 2019 8:12 pm

I'm going to repeat several things that have already been said, maybe add a couple more. First, while the definition of "parlor guitar" is kind of hazy, I have built three that I consider true parlors (basically single ought Martin size). I've also built double and triple ought, which I don't consider "parlor" but some folks do.

I used the Scott Antes plans but modified them - most people consider them overbuilt or over braced. I don't have the plans in front of me but as I recall the specified scale length was 24.0 inches and 12 frets clear. I built mine with a 24.5 inch scale which pushes the bridge down into the body slightly. I move braces very slightly to accommodate.

The length of truss rod depends on the length of the neck, whether you want the adjuster in the head or the heel (many parlors are slot heads and there isn't room for a head stock adjuster). Gibson (or Fender) curved tension rods work perfectly fine to counter act string tension and remove relief. The are a bit more of a hassle to make because of the curved route, however you said you are buying a premade neck - that means the channel will be routed for you. Many people, including me, prefer double acting rods such as StewMac, LMII and Bitterroot sell - if your neck is routed for one of these then you don't have any choice. Double acting rods can be installed as either head or heel adjustment - again, it depends on how your neck was routed. Different rods have different channels - 1/2 by 3/8 is common but you should measure yours before ordering the rod (unless you buy it from the same folks who made your neck). If you have trouble finding the right length rod, Bitterroot does make them in 1 inch increments (and there are people who will make custom rods).

I just reread your first post and it says you are getting a "classical" neck with a truss rod channel already in it. That waves some flags - most classicals (nylon strings) do not have truss rods, most have very wide necks, slotted heads, are drilled for large plastic rollers. Most are built with a Spanish heel and common scale is 630 mm (I think). What I'm saying is it might not work for a bunch of reasons.

I'm going to add that IMHO you need some sort of plans and you need to follow them. The geometry of every guitar starts with scale length, location of the body/neck joint, width of the neck at a couple of critical places. The amount the top is domed will set the neck angle, the location of the bridge establishes the splay of the braces (unless you are building a ladder braced guitar, which can be a very interesting option for a parlor).


So, short story, I think you should stop right now and make sure you know what you want to build and are buying parts that will work. We can help
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Re: Length Truss Rod for Parlor Guitar?

Postby Chuck Tweedy » Tue Feb 05, 2019 1:18 am

yea. what freeman said
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Re: Length Truss Rod for Parlor Guitar?

Postby Keith Walden » Tue Feb 05, 2019 1:37 am

Image

This is the neck, its close to the ''standard'' parlor 21" neck Im guessing.
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Re: Length Truss Rod for Parlor Guitar?

Postby Bryan Bear » Tue Feb 05, 2019 11:46 am

340 mm for the neck length seems a bit strange to me. If it were used as a 12 fret that would make the scale length 26.8" (actually a little less because you need room for the nut so lets estimate 26.3ish". If it were a 14 fret neck that would make the scale somewhere under 24" (again depending on the nut width). It also looks like you have a little wood to work with at the heel so you could shorten it a bit there. You'll likely also lose some while fitting the neck to the body since there probably isn't a neck angle milled into the heel.

55mm is really wide for a nut on a steelstring guitar and 65mm at the heel give you a string spacing at the saddle in the neighborhood of 2.5+".

It is hard to tell from the pictures but the slot in the neck looks like it was made for a static reinforcement insert of some kind; it looks to curve up to the surface near the end. Again, it is hard to tell from the picture. I'm betting you are going to have to do some modification to that slot for an adjustable truss rod.

The peghead has been slotted but not drilled. This isn't a big deal but usually the holes are drilled before the slots are made. This keeps the inside of the hole from blowing out when you drill it. Just make sure to support the backside (inside) of the hole while you drill it.

It looks like the taper and heel are only partially carved. You will have to carve to final shape. This is probably good as it will make it easier to flush up to your fretboard.
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Re: Length Truss Rod for Parlor Guitar?

Postby Brian Evans » Tue Feb 05, 2019 12:12 pm

I would look at that as a blank, I use a tenon to locate the heel, so 340 mm is 13.4", less say 3/4" for machining the neck angle and a tenon, some space at the end of the flat for a nut, and you'd be in the 25" scale range. It's a classical neck so it's desgined to be joined at the 12th fret. You can obviously make the neck as narrow as you want, just carve it to what you want. My process is to glue the fretboard on the neck before I carve it, so the fretboard is at finished width, bound and slotted before it's glued, which may or may not work for a flat-top. I'd be really tempted to make it with a carbon fiber insert rather than a truss rod, and use light strings on a shorter scale length, maybe 24.5"

Some inspiration: https://jakewildwood.blogspot.com/2019/ ... attop.html
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Re: Length Truss Rod for Parlor Guitar?

Postby Bryan Bear » Tue Feb 05, 2019 12:59 pm

Good point Brian! I was not thinking about room for a tenon. That makes the shaft length make more sense. Also, that is a good way to look at it, as a blank rather than a neck since there is still a good amount of work involved.

In addition to addressing the truss rod slot and milling in the neck angle (with or without a tenon), once the nut width and fretboard taper is decided there will be a lot of carving of the shaft, heel and the nut and heel transition areas.
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Re: Length Truss Rod for Parlor Guitar?

Postby Keith Walden » Tue Feb 05, 2019 1:12 pm

Id rather use a truss rod just in case of any issues. I doubt that wood is selected and quartered, but it will be bolt-on, in case of future issues.
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Re: Length Truss Rod for Parlor Guitar?

Postby Freeman Keller » Tue Feb 05, 2019 9:44 pm

Keith, lets start with the neck in your picture. You have four choices of how you can build that out (actually more but four reasonable ones). The first decision is whether you will put the nut on the flat or the angled part of the head. Lets say the angled part. That means your nut measurements start at the break of the neck. OK, next, are you going to build a 12 fret or 14 fret guitar. Most parlors and almost all classicals are 12 fret guitars - that means your scale length is 680 mm or 26-3/4 inches (nut to body joint). That is a monsterously long neck - its actually about what would be used on a baritone, the complete antithesis of a parlor.

OK, so that forces you to make it 14 frets clear. 340 mm is 13.38 inches (I work better in inches). If I run the fret calculator backwards I find that a 24.0 inch scale gives me a 14th fret position of 13.309 inches from the nut. That is close enough and is actually a scale that might be found on a parlor. Its going to look weird, I'm not sure I've ever seen a 14 fret slot head.

Next thing about the neck in your picture - 55 mm at the nut is darn wide, even for a classical. Steel string guitars are typically 43 or so (1.75 inches), classicals are maybe 51 (2 inches). Same with the heel - you are going to have a heck of a lot of carving.

I can't see from your picture what kind of heel it actually is - a true classical will be something called a Spanish heel - its definitely not that. Steel strings will be a dovetail or bolted mortise and tenon joint - might be worth while knowing what you are getting into.

And just so you know what you are getting into, here is a little build thread that I did for another forum when I made my two parlors. My plans called for 24-1/2 inch scale but I modified it to use commercially available precarved necks.

https://www.lmii.com/precarved-steel-st ... -head.html

I had to move braces and the bridge slightly to compensate. Actually a 24.9 inch scale is still considered short but it does increase the string tension slightly from 24.5 - something I prefer. Anyway, here is the build thread

https://www.harmonycentral.com/forum/fo ... of-parlors

You'll notice that I used a 14-1/2 inch truss rod with adjuster at the heel. I also built in an outside mold (I don't think I showed bending the sides - I use a heat blanket and inside mold for that.

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Re: Length Truss Rod for Parlor Guitar?

Postby Keith Walden » Tue Feb 05, 2019 11:20 pm

I think its flat on the heel, I will probably have to add" a bolt on attachment. I did see they offer a spanish heel but I need to keep it as simple as possible but maybe I could have got the bolt on out of that style with some saw work, oh well. Epoxy, screws and some spare mahogany.
I like the width, so I can carve it down, thats fine. Im disabled so I need to keep the physical aspects as simple as possible.

Im a bit worried about doing the rosette channel with the ''popsicle stick method'' ala cumpliano? think I tried that and it was a nightmare. But I do think I have my dremel and base so hopefully worst case I can do it mechanically.

Im hoping to match the scale with my little parlor guitar, so well see when it gets here. sliming down that heel perfectly would be a real PITA.

Actually, if I do the Bolt-on first, I could sand the angle on both sides of the bolt on, not too bad, so maybe that issue is solved. Yes, that creates a right angle to sand against, so that is solved, easy.

I need easy.
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