I totally agree on always balancing. To me the argument that single cylinder engines are always going to vibrate doesn't hold water. I know that they are never in perfect dynamic balance, but how is running an out of balance prop going to help, unless the orientation of the prop is somehow magiaclly perfect to counteract a dynamic imbalance in that particular engine? It;s not going to help if the prop is out. IMHO balance the prop carefully and eliminate that variable from the equation! The day I became fanatical about balancing props is the day all my engines started running more smoothly and the aircraft certainly appreciated it too.

I always sand flash off the leading edge and tips of new props, using wet 600 grit paper. Most airfoils don't work better with flash on the LE apex.

I have to disagree a bit on the composite prop statement though - I have found pretty noticable imbalances in a large percentage of the props I've purchased, mind you I use APC almost exclusively. I recently sifted through about 30 pylon props plus an assortment of 9-6, 9-7, 8-8, 8-9, and maybe 4-5 were pretty good out of the package. Most needed one tip or the other tweaked, but some were very out of balance in the other axis, IOW one side of the hub was heavy so they would settle hard in one orientation, but with the blades at or near horizontal. Yes btw I was indexing off the molded holes - I would never even think about using the pre-drilled through hole as they come! I always ream oversize and bush the prop hub in the rear molded section. The "accuracy" of APC's drilled through holes is somewhat of a joke in my books these days and I've grumbled about it ad nauseum on RCU.

So when balancing, my advice is watch carefully how you are indexing the prop onto the balancer shaft - it must be the same method used to index the prop on the crankshaft. That way off-center through holes won't add a new factor to the balance situation.

MJD