Steel-reinforced truss rod for Concert Ukulele

The Concert Ukulele model has a channel inside the neck for a brace to stiffen it, protecting against PLA creep under tension of the strings. I had intended to just print an insert in PETG-CF, but after modeling different internal geometries I found they all flexed a similar amount.

Without a winning option in pure printed plastic I went back to steel, like in a guitar. As the standard 150mm M3 rods aren't quite long enough for this job, the middle one is offset, but the result is still inflexible which was the goal. It adds a little weight, but not enough that I think you'll notice.

Setup and printing

You'll need to buy 3x 3mm rods, 150mm in length. They're commonly sold as spares for RC cars, described as 3mm Diameter 304 Stainless Steel Rod or M3x150mm smooth rods.

• Make a pause at 4.2mm in your slicer, just before the cavities are printed over, so you can insert the 3 rods

• Print without supports (the rods will make sure those internal channels are held up)

• I used 6 perimeters and 6 solid layers but 100% fill will have the same effect

Thanks to @Science_Envisi_45992 for the original Concert Ukulele model