I needed a universal joint for the trolling motor tiller handle extension and was unable to find one on thingiverse in a hurry so I remodeled the u-joint design found in the awesome kayak rudder setup published by @LoboCNC.
I want to eventually remix the rudder assembly for use on my canoe and am even considering using a decent sized stepper and/or gear-reduction for an electronically controlled (steered) rudder.
The spider will connect to the two u-joint parts using 3mm screws (roughly 20mm length) and 3mm nuts. I recommend printing the spider at it's current orientation for best strength.
Pictures coming soon (heading out to the lake tomorrow and still need to print the "spider".