...Props 101...

[Bootlegger]

 Does a larger 12" versus 11" make a model "fly" nose heavy?  I know that it creats Gyro pression, but does it make it "slow" to turn as does nose heavy does?

 Thanks a lot...

[Dean Pappas]

Hello Gil,
Too much diameter will both slow the turn and sometimes it will cause an airplane to hunt in level flight.
I know these two sound contradictory, but it does happen.

Regards,
 Dean Pappas

[Steve Helmick]

I hope Dean will come back and answer the question I've had for some time.

It's pretty easy to tell if a prop is too much load for the engine. I am not at all sure how to tell if a prop is not enough load...so what do we look for?   

[Jim Thomerson]

What you do is buy a number of different props around the useful size and try them out.  You select the one which works the best and save the rest for the next engine/airplane, as one of them may be the best of the bunch. 

[Lauri Malila]

Hi.

My aproach is to choose a standard blade form (design of Y. Yatsenko) and zoom it bigger or smaller in 1/4" increments, and then have them cut with a CNC machine. Standard pitch is about 6" which I can easily manipulate +o/-1" by heating & tweaking, with 1/8" steps.
Some may think it's lots of work but at least I have a good control over variables.
Just remember, gyrorcopical effect increases exponentially as you increase diameter, and linearry with prop weight. So, usually less diameter and more blades is better.
But bigger diameter helps to make round maneuvres round. And less diameter helps to penetrate into wind. Allways aim to smallest diameter that the plane is happy with.

L