I just installed the Whirlwind ground adjustable propeller on my Lycoming 160 Hp RV-4. I really thought about ordering their 13" spinner kit also but I'm glad I didn't. It would have looked wrong and it would have made getting the cowl off very difficult as it would not allow my hinge pins to come out the front beside the spinner without taking the spinner, prop & bulkheads off. So, I made the Van's 12 inch spinner work. It does go over the edge of the outer bolts which requires an unusual cut-out for that. It also requires inovative thinking to make the front bulkhead work as the hub is about 1/2" thicker than the wood prop. I'll be glad to send pictures & an explination of what I did for the front bulkhead via email if you want. Just send your request & email to
mccutcheontm@gmail.com. I've sent this information to Rob at Whirlwind also.
For my application I ended up setting the pitch (airplane level) at 23 degrees using an electronic angle finder from Harbor freight. This only gives me 1900 RPM static but gives me about 2700 RPM in the air straight and level. I started at 20 degrees which gave me 2200 RPM static. When I added power on take-off it really sat me back in my seat. I was impressed untill I saw too much RPM in level flight. I've only flown it about an hour now I'm estimating that I'm getting about 3 to 5 MPH faster than the wood prop I took off. So far I'm impressed with the prop.
Tom McCutcheon