This propeller was fitted on a 2litre VW wind generating machine and spun to 3600RPM.
A front-end loader dumped 1000kg’s worth of river-sand, containing an average gravel size of 6mm, into the prop arc at a rate of 100kgs per minute.
Note the severe abrasion damage to the wood content of both blades, compared to zero damage to the urethane leading edge.
Similar damage may occur flying in rain or during take-off and landing on rough airfields.