> I dont think I can get away with a dimmer type triac controller

I think you can. You may find starting, or even running, at low
speeds a problem though. An alternative to using partial-cycles
(as a dimmer does) would be to drop complete cycles or half-
cycles. The momentum of the blade will smooth the rotation
lumpiness to some extent. One thing to watch out for is power
through the windings at slow speeds, ie not enough to spin the
blades to create a cooling draft, but enough to heat the coils.
Overall I think it depends on the physical characteristics of
the fan, eg blade weight and inertia, motor size and torque

--
http://www.piclist.com hint: The list server can filter out subtopics
(like ads or off topics) for you. See http://www.piclist.com/#topics