I sent Rick Toone an e-mail to ask him about his stunning Orchid design, which uses a fixed truss rod and a trapezoidal neck shape. The conversation appears here:

My question:

“Did you arrive at the alloy and dimensions through any science? I was thinking 7075 or 7021 T6 aluminum, which on paper is stiffer and stronger than 6063 (although, I have arrived at that fact only through reading catalogues – I am no expert.) With the twisted neck that I want, 6063 would probably be more suited than the 7*** series, so it would be good if it worked.

I am still a little concerned that the neck might flex. How have your experiences been?”

Rick’s swift response (published with permission):

“My experience with the square aluminum barstock has been excellent. Despite an almost inability to flex the barstock by hand (on the workbench), the pull of four bass strings in a 32″ scale length is enough to slightly flex the neck (less than the thickness of a business card) at the 12th fret. Astonishingly powerful. If you are building a six string guitar, the aluminum barstock would likely have unmeasurable flex. So my intuition tells me. One potential problem would be the neck thickens (as perceived by the hand) as it shifts around the axis of rotation.
I’ve been thinking of building a slightly twisted neck that rotates around a central hollow core of titanium tubing. Either a single diameter .75″ tube, or two side-by-side tubes (diameter to be determined). With such a construction I could retain the trapezoidal neck profile, yet keep a consistent neck thickness (as perceived by the hand), the length of the neck. Titanium would, however, likely have too much flex for a bass neck.”

Thanks to Rick and I will keep you posted on the progress. I got in touch with an aluminum shop today, but he didn’t have access to e-mail so will have to get there in person as soon as I can.