prop size
 

what size prop die. can i use on a 8a?

Are you asking ...
 

Are you asking "What is the largest diameter prop I can use on an RV-8A?" That should be in your manual I would think but the 8A owners or Van's tech assistance should be able to give you that information. Other prop selections get tougher of course.

Bob Axsom

I believe that max recommended prop size is 74".

If you go the three-blade route, you can have a much smaller diameter which will give much more ground clearance. A three-blade can be as much as 70% shorter than a two-blade and still intercept the same volume of air, while having much less high Mach tip loss and be quieter.