Today (and yesterday) we worked on a reduced size blank, foreshortened to 25% of the length of the 'real thing'.
The blade came out pretty good, even though half way through the second side we burned up our brand new router. We hit a piece of dry rot in the wood, the router stalled, a puff of smoke and that was it... 14mm cut, that should not have happened.
Anyway, we got a new one under warranty, plugged it in this morning and finished the job.
Some small issues remain, the z axis registration is still a bit off (we think we have found the problem though, on 'flipping' the piece if the blank is only a tiny little bit higher than the computer thinks it is the surface will come 'up' that much more, and both sides will intersect at the wrong point).
The blank that Ron made was a lot better than the previous one, in that it had a minimum of wood used. (and we're not counting the one that he mirrored here, in fact that never happened 
We've changed the blade geometry a little bit for our next test (still wider tips, now 15 cm), on advice from Laurence, my friend the windmill guru
We're making a new blank now, tomorrow we'll run that and this time it should work !
(Yeah right).
Please excuse the quality of the wood we used, this is just to get the shape right (of both the blank and the blade), no point in wasting good wood on that, cheap stuff & scrap will do.
Pictures follow:
Cutting the blade:
The front of the blade:
The back of the blade:
