Hi Mark, The bow fender was strictly speaking a Turk's head. Quite how it was constructed I don't know, and Joe has long since left this mortal coil.
It is similar in appearance to a Monkey's fist, and may be common in terms of construction. I'm sure ethere will be some maritime books and web pages that show how to etc.
Joe told us that L & L boatmen would paint them with white gloss paint, that hardened them and extended their life.
This is a Monkey's fist he made us back in 1983:
It was made as a key fob, and as it's quite light, suspect the core may be a cork from a bottle. Never tested its ability to float! I'm sure it would.