Two to three blade prop equivalency?

[Scott Richlen]

I did a search but nothing came up, so I'll ask here.

For a 12-4 wood, what would the equivalent be for a 3 blade carbon fiber?  Or even simpler: what is the 3 blade equivalent for a 2 blade prop if the 2 blade is 12 inches in diameter?

I have a couple of Bolly's with split or chipped tips, so I'm thinking I should cut them down and try them on my LA-46.

Thanks,
Scott

[jfv]

The very "general" rule of thumb is: reduce diameter 1 inch for 3 blade for same pitch as 2 blade.