Balancing the Blades
As explained above, balancing the blades is crucial to the proper operation of the unit. If the blades are out of balance, it will make the turbine vibrate badly, which causes the tower and everything that’s attached to it to vibrate badly as well. This will cause undue stress on everything.
There are several ways to balance the blades. First of all, if we have several pieces of wood to choose from, we will try to get three pieces that are very close in weight to begin with. Also, make sure that the wood is not warped. Choosing good pieces of wood to begin with, will save you a lot of frustration when you come to the balancing later. After removing most of the wood and getting the blades close to being finished, we weigh them to make sure that they are very close to being the same weight. Once they are finished and ready to be painted, we put them together with two round plywood plates, top and bottom and hang them from a perfectly centered hook to a level truss in the ceiling. If you know that what you are hanging them from is perfectly level and that your centre hook is perfectly centered, then you can tell by the way they hang whether or not they are balanced. If they are balanced, they will hang perfectly level. If not, they will be slightly off kilter and you can see which blade needs a little more weight added to balance it to the others.
At this point, the blades need to have a coat of epoxy applied to the leading edges to protect them from the elements once they are up and running. Once you have hung the blades and have identified which one or one’s need a little weight added to them, you can do this with the epoxy. On the blade or blades that are a little light, just put a little extra epoxy on them and that should even them out. While we are applying the epoxy and paint to the blades, we always hang them in this way from the roof truss while they dry and that way we can see how well balanced they are. This method has always worked very well for us and we usually recommend this method to everyone.
Another method that we have heard of is to drill tiny holes in the blade that is a little light and melt some lead and pour it into the holes and seal the holes up. Apparently, this works quite well also, but we have never given it a try.
Once the blades are balanced as close as you can get them to perfect, the next step is to make sure that they track properly. We have a small test tower right beside our house where we do all of the final checks. Once the blades have been attached to the unit, we stand to the side and spin the blades and watch where they track. If you notice that one of the points of the blades is a little farther in towards the tower or out farther from the tower than the others, then it is not tracking perfectly. You can usually fix this by putting a washer behind the blade that is out slightly to bring it out a bit.
We have not had much problem with the blades not tracking properly because we are very careful with checking the blades as we go along to make sure that everything is perfect. If you take your time, they should be fine.