[RichH]

Rudder bearing typically fail due to abrasion and not compressional loads. I wont venture a guess about what rudder load you can expect; but, do offer the following:
Nylon will hydrolyse (the breakup of the long chain molecules)) in water; should NOT be used in ''wetted'' applications. Delrin is subject to "face transfer" - meaning the delrin will abrade quickly and attempt to transfer/attach to the rudder stock. UHMWPE is too soft to bear loads unless you have comparitively large bearing surface areas. PTFE or allied fluropolymers if purchased in cylinder or barstock will be prohibitively expensive.

I assume that you have worn rudder shaft bearings. An adequate strength and frictional repair is possible by using your present bearings and filling the voids with carbon filled epoxy and Technora (PTFE thread) or "PTFE dental floss". Method: polish the present rudder shaft to a "mirror" polish using "Tripoli" buffing compound (available in most old-fashioned hardware stores). Coat the shaft with wax; rub on then heat lightly with a torch to apply and smooth-out a ''few mil'' thickness of wax. Wind the PTFE thread in an very open ''diamond pattern'' on the shaft but not so tight as to not deform the wax. Mix epoxy resin and fill with carbon powder to the consistency of thin mayonaise and apply to shaft/bearing surface. Assemble the bearing and mix, allow to cure. When fully cured, rotate the shaft to break the wax free. This ''fix'' is quite popular on many Pearsons that use delrin rudder shaft bearings. Do a websearch for ("Pearson + bearings + rudder") for other info.

BTW - If you''re machining base polymer from scratch, your bearing clearance should be approx. 0.002-0.003" per inch of shaft diameter (less any press fit/interference fit that you use to press the bearing into the GRP to mechanically hold it in place.