Not sure how well spray paint from a can will perform on the old lexan rudder blades... If you really need them to be painted, you could contact a local car pint shop... Those guys use additives in their paints when they paint plastic bumpers ... they might also have a primer that might facilitate better contact to the plastic. Some of the web sites (ICI) might give you some insight on additives and paint. Here is a more general question ... Why do you want to paint those old rudder blades - they suck - even when they are painted they will flex under load. In case you want to spend some $ on blades get some fiberglass blades. In case you want the looks get some carbon or kevlar fiber EPO's. Patrick