Whistling fins.
Yes the Thor is renound for whistling - sounds good too.
Mine however don't.
I would speculate the reason that mine do not is as a result of some serious aerofoiling.
Take a look at my Thor fins next time you have chance Karl.
In contrast Richard Parkin's Thor does. But he hasn't aerofoiled them.
We think that the main reason for the whistling is the turbulence caused inbetween the un aerofoiled fins.
Funny thing is - I really like the whistling and was a little disspaointed when my Thor was silent!
A Hypertek motor system resolved the lack of noise on it's way up though!
Damian