Prop balancing

[Gary Dowler]

 I saw the recent thread on balancing 3 blade props, but I want to expand the question a little further without hijacking that thread.
What is the proper method for balancing 2 blade props?  In my flying past I never used anything but Top Flite or Rev Up wood props.  All I ever understood was to remove material from the tip of the heavy blade until it was evenly balanced.   Back into flying and this is where I picked back up.  Wood props can have significant imbalance issues, and I have had several props that needed 1/4", or more, of material removed to balance. One that I think I ended up tossing didn't balance until I had sanded roughly 3/8" off one tip.  This seemed to me that it would introduce a-symetric thrust.
More recently Ive been using some Master Air Screw nylon props, and these seem more inherently even and balance quickly.  Most recently Ive been using some APC props at Brett's suggestion, and these seem pretty good as well.
In the other thread I saw references to sanding material off the front or back of the blade, as opposed to just at the tip.  I have never done this but it seems to make sense.  What is the current accepted best practice for balancing 2 blade props?

Gary

[Dan McEntee]

   I never cut a blade length down. I have Jim Lee's tool for marking props and use that to check blade length and even them up. Sand material off the front and back of the heavy blade evenly. If the heavy blade just doesn't want to cooperate, you can try adding a thin layer of epoxy to the light blade as evenly as you can and let it cure, then start over. Clear dope or polyurethane can be used also . You should refinish a balanced prop also, and recheck. If necessary a further dab of the clear on the light blade should bring things back even. A white or yellow tip is a good help in seeing the prop arc and an additional coat of that paint can help with balance. For serious work, I have one of those Great Planes magnetic balancing rigs that I modified. The arbor that comes with them can be quite off itself. I replaced it with a Prather hand held unit that is all machined metal and very true. I replaced the rods that come with the balancer with rods that are just long enough to fit the Prather finger balancer. It is very sensitive and can even help you find props with the hole off center that you probably couldn't see. Another good tool for you flight box is a set of prop reamers in both standard and metric. I have been impressed with recent plastic prop products coming from Master Airscrew but they are marked about an inch more pitch than they really are according to a Prather pitch gauge, and APC is pretty consistent also.
   Type at you later,
     Dan McEntee