I experimented with a number of different strings for the double-bucket.

Quite a few people use weedwhacker line for the broomhandle type, but when pulled to enough tension for a full-length "fingered" double bass it's "creepy." You get it in tune, then it stretches, so you retune, then it stretches, and after a very few tunings of course it breaks. It's also deliberately made to be very "hard" compared to other kinds of polymer line, but isn't particularly uniform along the length. You can't get a "pure tone" from a lumpy string, so in my kind of bass it just didn't sound very good. It probably is more suited to instruments with a shorter string length (and lower tension) than I used.

Most "twisted" cordage has a tendency to fray in a use of this kind, and ones I tried also seemed to have lots of damping, probably due to internal friction in the cord.

I had the feeling that a braided fishline would work pretty well if one chose to adjust the string length to suit the line to be used, but I wasn't able to find a sufficient range in line weights to suit my particular design. The popularity of monofilament fishline has pretty much driven braided lines off the market, with the exception of small sizes for seine/net repair. Had really heavy braided fishline been available, I might have made it a four string instrument(?).

The cord I finally settled on is sold as "lawnmower starter cord." It comes in only two "weights" (that I found) and I tried both, but settled on the heavier one. It has a stranded straight-through core that gives it very high strength with little stretch or creep, a very tight woven/braided casing that adds good weight/length, and is impregnated with a polymer so that everything is "clamped up" and there's relatively little internal damping when the string flexes. It's also quite waterproof, and of course grease/oil resistant.

Based on experiments with other string types, I expected to need frequent replacements, so of course I bought a 300' reel. As the original string is going into it's 17th year of use with no sign of deteriorating, I guess I'm good for at least 850 years of playing ... unless I decide to fiddle with the design.

John