While making carbon fiber parts is pretty messy and hard on the spirit, there is one little Ridgewing part that is a real pleasure to make – the bridge cover. Here you can see an original Chrysalis guitar bridge on the left next to the upgraded Ridgewing bridge. This Ridgewing bridge sports a green cover, but the other colored covers are just five little screws away from a new fashion statement.

The original Chrysalis bridge was equipped with just a bare under-saddle Fishman piezo pickup, with all electronics being left to the player to add off-board. To offer some help, we Velcro-modded a Fishman 9V stick pre-amp so it could be attached to the guitar’s strap, but that was it. In the years that followed, too many players to ignore said “Can you please give it some adjustment knobs?…”. 

It was decided that the redesigned Ridgewing bridge would have a full-featured self-contained pre-amp system built into it. This package would include the sensor, pre-amp, rechargeable battery, T/V control knobs, USB link, and as many LEDs as you could get away with. The idea was that by consolidating all of the electronics into a single component, the bridge, the guitar would have a clearly defined “brain”, and that brain would be as interchangeable and easy to switch out as any other Ridgewing component.

The final design of the electronics package was a single small feature-packed circuit board, designed by Q, that was mounted on the treble end of the bridge under a black plastic cover, black being our default color at the time. Knowing the importance of indicator LEDs in the system, a lot of discussion went into trying to decide where to put standard LED locations on the circuit board so that light pipes could be molded into the cover to carry the LED’s light to the surface where the player could see them. After going round and round on this, the solution ended up being to just make the cover transparent, so it didn’t matter where the LEDs went.

This is the mold box that was built to make the new bridge cover.  It was also our first mold box built to yield “net-finish” parts that included molded-in threaded inserts for the cover screws. By making the mold with highly polished surfaces on the “plug” (model used to make the mold), no polishing or other post-processing would be necessary. Just take the new cover out of the mold, give it a little rubba-dub-dub with a paper towel, and put it on your guitar.

Being unwilling to leave good enough alone, we found it pretty easy to add a few drops of the plastic equivalent of kitchen food coloring to each batch before it was squirted into the mold. Now for special occasions you could color-coordinate your guitar’s bridge with your outfit or other colored parts, and all the while the LEDs could peek through the cover, no matter what the tint.

As I have mentioned elsewhere, the great enemy of the small-shop molder is bubbles. For the larger guitar parts like the frames, grills and neck, the best we could do was to try to meticulously poke all the bubbles that appeared during the process of laying the epoxy-saturated carbon fiber into the mold. Of course this was impossible, so a sacrificial extra cup of epoxy was poured in just before the mold lid was closed and clamped tight. It was a pleasure then to see excess epoxy coming out of the vent tubes with bubbles in tow.

This little bridge cover mold was different.  Its small size allowed it to fit into the benchtop pressure vessel shown below. After the tinted plastic goo was injected using a big hydroponic syringe, the filled mold was put into pressure vessel, the lid screwed down, then subjected to ten atmospheres of pressure for the whole time the plastic cured. This pressure had the effect of squeezing any bubbles in the plastic down so small that they were no longer visible, and it worked wonderfully well. These small victories are precious.

Threaded brass inserts were mounted on screws in the mold cavity before filling, a procedure known as “insert molding”. The result was that these little hardware bits came out of the mold already in the part rather than having to be drilled and glued in later. The result was that, when the mold was opened, out popped a finished bridge cover that just needed a little rubbing with your shirtsleeve, then off to your gig with a new show-and-tell.