An idea I've considered is buying a large
exercise ball and inflating it till it was quite firm. I'd use that as
the male mould. Take the female off that one and use it every time I'd
need to rebuild the nosecone. Like when my obstacle avoidance
sonar failed.
Needless to say it wouldn't have any surface
patterns, ribs, seams, etc. At least I'd try to get a seamless
one. Less work later on to grind off funny lines and "made in China"
labels.
One consideration is that the ball would
probably not be to scale. Could possibly use only part of the arc of
the ball for the nosecone. That way the scantlings could be faired
into the cone.
Rick L.
Vancouver