I've got the Dubro Tru-Spin Prop Balancer http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXD712 $32 that helps an engine run smoother, with less vibration and ultimately could save your plane. So they tell us. When I was flying rubber powered Free Flight and making my own props, it was imperative to have a balanced prop in order to get as much efficiency out of the prop. What I notice about using the Dubro balancer is that it can almost drive you nuts because it will show the smallest out of balance condition. Heavy blade or heavy hub. Sometimes I wonder if just the house HVAC system with the slight movement of air is affecting the process. So I've come to the conclusion there is a point where with any prop, I get to a point that I have to accept. Some props are easier than others.

My method. First determine which blade is heavier and which side of the hub is heavier. Use a sharpie to mark them. Test to see if you've really identified them correctly. Then I like to take some 100 grit sandpaper and start going over the whole prop. They're too sharp right from the manufacturer. Check to see if the heavier blade still shows, if it does, I will just take the light end and dip into a jar of butyrate dope. Making sure it dries uniformly, by turning it so drips and runs don't happen. Sometimes this step can take up to 3 tries, but if you make that blade too heavy, then sanding should even it out. The next thing that usually shows is one side of the hub is heavier, this one seems to be harder to correct. I'll try sanding the heavier side, especially if there is any seam from the mold that I can remove, but sometimes it takes adding some weight to the lighter side. I use a nice glob of 5 min epoxy on the lighter side, again watching that it doesn't run. Later if too much has been added, I will then sand some off. A balanced prop should hold 10:00, 2:00, 4:00 and 8:00, without dropping a particular side. Whew! And to think I could break it on the first flight. Seems that the more props I do, the better I get at it. I know when to quit and go on to the next prop. Once balanced, I like to wrap in syran wrap or plastic so that in my extra Prop bag, I know which have been balanced.