There are many forces on a windmill and some of the heaviest hardwoods may be best avoided but some are perfectly acceptable.
There is the centrifugal force tending to stress the blade roots under tension and heavy blades will have a larger force. This is counteracted to some extent by the fact that the hardwoods may have more tensile strength.
The gyroscopic force is one where there is a force at right angles when the machine yaws or changes direction. If there is no yaw then there is no force. if you have servo yaw or a fantail that steers the thing slowly this is no issue. For a normal tail steered thing then rapid changes in direction cause significant forces trying to tip the machine back or forward. If the spindle and bearings are inadequate there may be some issue from this, but normally the only issue is that the bottom blade tip gets thrust back during violent yaw in one direction ( forward in the other). if the blade strikes the tower then you have a problem. I haven't met a case of blade snap from this issue unless it actually strikes something.The gyroscopic force will also stress the yaw pivot and the tower, but if they are adequately constructed then this is a non issue.
Decent strong straight grained hardwoods are perfectly ok, ash should be excellent. I used maple once and it was fine but such a pain to work with that I wouldn't use it again.. strength to weight is more important than weight alone ( but I wouldn't use very heavy timbers). There are many varieties of oak and I don't know enough to advise but some may be suitable.
Apart from the risk of tower strike I don't think gyroscopic forces have much effect on furling apart from a slight slowing from increased frictional loading on crude pipe on pipe bearings. Tail size and weight does very much affect furling but it will not matter much on the material used for the prop.
The main factors for furling are alternator offset , tsr and type of blade profile and the method of alternator loading. I think many machines don't furl at all and rely on stall limiting and if they ever get away from stall then the furl may be at far too high a wind speed to offer any protection. There is a seeking force holding the prop into the wind and if that dominates it will go head on into the wind and the tail will be helpless to stop it.
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