Trapezoidal Neck Profile

EDITOR'S NOTE: This article is part of a series exploring aspects of the Trapezoidal Neck Profile including: construction details, design theory, and ergonomics. Technology developed by Rick Toone. Patent applied for. John Vereb, patent attorney. Full information access — with licensing included — is available to eLUTHERIE.org members via Design & Technology Exchange.

Trapezoidal Neck Profile is unique in the world of instrument design because of how it interacts with the human hand, two locations in particular:

• index finger-to-palm joint
• thumb

In both classical and pinch grip playing positions, these two anatomical features are primarily responsible for controlling and orienting the hand in relation to the neck, allowing the fingers to smoothly perform fretting tasks.

Orchid (bass) was the first instrument to employ this design. It is equally effective on guitar, and I have incorporated it into current builds including: Skele, Dove and Cupid.

Pinch Grip

This is likely the most common playing position, with the neck cradled between Metacarpophalangeal joint and thumb. Back of the neck often rests against the fleshy "web" connection between thumb and palm as the thumb floats upward or over the top of the fingerboard to fret bass strings.

In studying how the Metacarpophalangeal joint interacts with conventional neck designs, I realized convex surfaces actually prevent the fingers from penetrating deeper into the fingerboard, which is one motive for assuming this playing position. Players seem to constantly seek less index finger resistance and greater overall finger reach.

By removing material — making the lower surface of the neck a flat plane (or even concave) — the neck comfortably facilitiates finger reach. Perceptually, the neck feels like a super slim profile.

PHOTO: Pinch grip playing position. Note lower neck plane contact with index finger Proximal phalange bone as Metacarpophalangeal joint "floats" just behind junction of lower and back neck planes.

PHOTO: As the hand shifts closer to the fingerboard for single note runs, pull-offs, hammer-ons, bends or vibrato the Metacarpophalangeal joint acts as a pivot against the lower neck plane as the wrist rotates.

Classical Grip

Musicians who are formally trained or who utilize complex barre chords, will typically play with the thumb centered on the back of the neck. This allows the fingers to rapidly transition chord forms.

Although conventional curved neck profiles offer highly variable leverage options against the fingerboard, my experiments indicate that is actually less comfortable than leveraging against a planar surface. I believe the reason for this is curved surfaces seem to require more fine motor effort from thumb muscles to stabilize the hand: Abductor pollicis brevis, Flexor pollicis brevis and Opponens pollicis.

After adapting to leveraging against a planar surface, playing a conventional rounded neck by comparison feels awkwardly like attempting to "balance" — that is how I would describe the experience.

I notice my fretting hand fatigues more rapidly when playing a conventional curved neck. One possible explanation is I have been building TNP necks much thicker than I would normally, because the reduced material on the lower planar surface makes the neck "feel" smaller in regards to fingerboard access. A neck .625" or .75" thick (or greater) has both structural advantages as well as leverage advantages, possibly because our hands are engineered by evolution to grasp weight bearing branches with great strength.

It is easy to simulate this experience by "fretting" on your forearm. Place your thumb against your inside forearm bone (Radius) near the elbow and "fret" a barre chord on your outer forearm bone (Ulna). Then place your thumb against your palm and "fret" the back of your hand. Your experience may vary, but I find it requires considerably less hand strength to "fret" on my forearm.

PHOTO: Thumb leveraging against planar surface as fingers form chord.

PHOTO: Note relaxed wrist position.

PHOTO: "Thumb strip" planar surface extends into body. Continued relaxed wrist position.

Video

Video is an invaluable tool for evaluating ergonomic interactions. Having studied the information above, take a fresh look at Monster's performance:

Comments

[Joe Gaskill]

Hello! I like reading Building the Ergonomic Guitar, which is where I found your site. I must compliment you on your fantastic work. Yet I was wondering, since I am building a guitar, if I could incorporate the trapezoidal neck profile onto my guitar neck? All credit is due to you, and I want something radical and comfortable for this guitar. Thanks for showing your work and future works,
Joe
-North Carolina, USA

[Rick Toone]

Joe — thanks for your kind words.

Drop me an email directly, and let's talk. Implementation of the TNP is a bit more complicated than it appears as published.

Cheers,
Rick

[cameron llewellyn]

I'm transfixed... Scrutinizing the pictures and pouring over you descriptions.
I am in the design phase for a headless, balanced guitar w a floating bridge.....
Your postings have launched me back to the proverbial drawing board.
I have anything but hard feelings about that!
Love the trap neck, you responded to someone about it being complicated...
Please consider some correspondence with me.
It would be awesome to hear your thoughts.......

[Doug Nolen]

I would like to know how to build a TNP neck. Do you have detailed instructions that a person might purchase? I think the idea may just solve my tendonitis pain in my "fretting hand" wrist.

[Steffan Llwyd (Steve)]

Mmmm... my 'girder/ parallel-frame guitar' (described on Ola's site) was inspired by the wish to have a (non-stressed) glass neck with an asymetrical profile which would accomodate the thumb in a way that exactly matches the shape of the thumb.

How to imagine this? Stick your thumb into 'hitch-hiker' position (thumbing a lift)and see how it has some nice 'return' curves in it... like an 'S' but the wrong way round. That shape could be accommodated by the underside of the neck. This lengthwise' 'thumb groove' would help players to locate their thumb for the 'classical' playing stance.

An offset groove along the length of your trapezoidal neck... along the face that you would see while playing... would give you the received 'rock' playing position. Maybe!

Neck profiles are best thought about while imagining squishing wet clay and 'seeing' what imaginary shapes you get!

I think there is a case for having depressions in this groove to help locate different barre chord positions. For example 'Fifth Position' would have its own natural location depression. Given the incredible density of nerve endings in fingers and thumbs a depression of maybe just 3mm would be enough to 'tell the thumb' that it had arrived where it needed to be, to (say) play the Hendrix chord...
A sweet spot on an electric guitar neck if ever there was one!

Folk players would want their dimples in other places as they mostly pick in first position and favour playing in G maj a lot of the time....

Imaginary innovation is so easy.... but making these things for real takes soooo long...
: )

Steffan/ Steve