effect of heel on truss rod

[PhoBucket]

Excuse me for being truss rod ignorant, but if the heel (heal?) was near the headstock instead of the body joint, would that have an impact on how the truss rod functioned? On bass setups, there is some relief up to the 12th fret, but the fingerboard is flat from there. Would moving the heel cause the relief to occur between frets 12 and 24?

ASCII pic representation

Normal setup
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Heel underneath neck near headstock
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[PhoBucket]

I couldn't get the spaces right on the ASCII images, but the brackets are meant to be empty space.

[BrendaEM]

Do you mean a volute?
A volute, will stiffens the head/neck area. It doesn't make much difference in the relief because it's not in the fretboard area.

Or just moving the heel toward the head?
On most instruments, most of the relief, most of the bowing seems too happen from the first to the 12th fret, probably because it's sort of in the structural middle of a tapered beam.

As the sting is fretted further up the neck, the need for relief goes down, because the angle from the bridge to the nut becomes steeper at each fret.

Bolt on neck guitars are like having a really big heal. If you make a heel far enough toward the nut, the truss rod may not be able to bend the neck as much, but it might not need to as much. Still, I wouldn't put it too far towards the nut or the truss rod will be forced to work in a non-linear way.

The heels on some Paul Reed Smiths, are pretty far toward the nut.

http://www.elderly.com/vintage/items/images/30U/30U-11098_heel.jpg

[My instrument has a heel between the 17th and or 19th fret of a 34" scaled instrument. I used one I wanted more strength where the neck meets the body, to raise the attack. Though, I like them too. If it's it's too big it will get in the way. If it's the right size, it will tell you where your thumb is when fretting the upper frets. With an unsymmetrical one, you can the best of both.]

[PhoBucket]

I hadn't thought of it that way, but yes, I guess I do mean an oversize volute. I'm looking for was to make a laptap instrument easier to balance on a stand/table, without effecting the adjustability of the neck.

With a thick enough neck, a truss rod might not be necessary, but changing the setup would become more difficult.

[mheintz]

For a laptap instrument, I think that you wouldn't need any truss rod. For adjustability, I suggest adjustable risers at the bridge and nut. Unlike an instrument that you have to wear, you need not worry that the nut-end would have too much hardware. You might even be able to use off-the-shelf hardware. For instance, if there is enough space, you could actually use individual bridge saddles instead of a nut. This would allow you to adjust height at the nut and bridge for perfect action.

[GaryOpenhill]

Originally posted by mheintz
For a laptap instrument, I think that you wouldn't need any truss rod. For adjustability, I suggest adjustable risers at the bridge and nut. Unlike an instrument that you have to wear, you need not worry that the nut-end would have too much hardware. You might even be able to use off-the-shelf hardware. For instance, if there is enough space, you could actually use individual bridge saddles instead of a nut. This would allow you to adjust height at the nut and bridge for perfect action.

Why is that mheintz? Is it because a laptapper would most likely be buildt with a thicker neck that won't be affected by the string tension?

[mheintz]

Originally posted by GaryOpenhill
Why is that mheintz? Is it because a laptapper would most likely be buildt with a thicker neck that won't be affected by the string tension?

Exactly. There is no neck, just a slab of wood. It can easily be twice as thick as a normal neck. Quite stiff. Moreover, there is no reason to introduce relief. On guitars, the truss rod is often used to add a bit of relief, but on tap instruments, I find the flatter the better. The strings just don't move enough to require relief. Since there is no need to introduce relief and the "neck" can be made to be much more rigid because there are fewer ergonomic restriction on its thickness, no truss rod should be necessary.

In fact, the more that I think about it, a laptapper is a really good candidate for a really cheap tapper.

[GaryOpenhill]

Originally posted by mheintz
Exactly. There is no neck, just a slab of wood. It can easily be twice as thick as a normal neck. Quite stiff. Moreover, there is no reason to introduce relief. On guitars, the truss rod is often used to add a bit of relief, but on tap instruments, I find the flatter the better. The strings just don't move enough to require relief. Since there is no need to introduce relief and the "neck" can be made to be much more rigid because there are fewer ergonomic restriction on its thickness, no truss rod should be necessary.

In fact, the more that I think about it, a laptapper is a really good candidate for a really cheap tapper.

Well i did build one tapper with a very thick neck, but it still had reinforcement. I'm now thinking i want to build another one of one single piece of oak, with an even thicker neck. I think the thick neck has some advantages for tapping in an uncrossed way, since the hands will get a better grip. At least i like the feel of it.
it's not a laminated piece, and it won't have trussrods or anything, but i think (well, hope) it will stay perfectly flat. We're talking about at least 4 cm thick in the middle of the neck. Do you think it will work?
The idea may seem to simple and stupid, and designwise its less than challenging, but i think it can sound very good, since the piece of wood is not glued anywhere, and stiffness of it will put all the vibration back into the strings working on the sustain. One of the inspirations for these thoughts came from Ned Steinbergs site and his thouhgts there about heavier string instruments, Also this should be perfect for experimenting for playing lapstyle, since it totally will look like a plank with some stuff on it. Im considereing shaping the neck in the end of the process, just to see what is like to play a plank first. Maybe i like it so much that i just keep it flat. :))
But, as you said, it certainly makes the building process a lot easier, faster and less expencive.

[mheintz]

Originally posted by GaryOpenhill
Well i did build one tapper with a very thick neck, but it still had reinforcement. I'm now thinking i want to build another one of one single piece of oak, with an even thicker neck. I think the thick neck has some advantages for tapping in an uncrossed way, since the hands will get a better grip. At least i like the feel of it.
it's not a laminated piece, and it won't have trussrods or anything, but i think (well, hope) it will stay perfectly flat. We're talking about at least 4 cm thick in the middle of the neck. Do you think it will work?
I have no idea. I believe that oak is typically not as hard or rigid as other woods typically used in necks, like maple. Instruments like double basses with maple necks and ebony boards do not have truss rods and last hundreds of years. Keep us posted.

[BigDaddyPoo]

Originally posted by mheintz
I believe that oak is typically not as hard or rigid as other woods typically used in necks, like maple.

Oak is a great wood stability and rigidity wise. The reason people don't typically use it in guitar building is its weight, which wouldn't be much of a factor in a laptop instrument. I also heard somewhere on this forum that it has a bad effect on metal hardware due to its high pH.

I think if you make the neck thick enough you won't need any reinforcement. At one time I had all of the equations for finding string tension and calculating wood's resistence to flexing at different thicknesses, but I can't find it. Wood's flexibility drops pretty rapidly with every cm of thickness added. You can also greatly decrease flex by using a shorter scale length. I used to have an upright bass with enormous strings that were 36" from nut to bridge. The neck was probably 2" thick for most of it's length and maybe 1.25" thick at it's thinnest. There was never a problem with needing adjustments, and the action was set really low.

I personally wouldnt worry about a heel or a volute...just make the neck a uniform thickness. In a lap tapper your thumbs aren't going to be on the back of the neck anyway, right? I also agree with mheintz that you don't really need relief in a tapper. The flatter the better.

[PhoBucket]

Thanks for the responses ehrybuddy. It sounds like it may be easier than I thought to make a real tap instrument test mule. (so say I before construction actually begins );)