Nov 17 2009
Working the Blades
Having written about beginning the blades in a previous post, I was able to get back to them today and continued roughing-in the front faces of the remaining two. You can think of the taper I’m making as the blade’s “angle of attack” to the wind, in much the same way that an airplane has to change its wings angle of attack to climb.
Although there are probably many different way to do this, you can see that cut slots in the board after laying out my leading and trailing edge lines. The slots connecting the two lines that will form the face.
Yes, my saw handle is duct taped together. It cracked when we were using the saw to completely renovate the Malaga NJ home – during the removal of a beam for a load-bearing wall and the resultant weight redistribution. I could just pick up another handle at a hardware mega mart, but it was my father’s before I got it and although it hangs on the wall, it gets put into service on occasion. Maybe someday I’ll glue the handle back together and paint a pretty picture on the blade and leave it to hang…. and maybe not 
After cutting the slots the arbitrary 1″ apart as marked, all that’s left to do was to knock out the kerfs between the slots with a sharp wood chisel, contemplate the universe, and reflect:
and then sand:
For the backs we can use some of the aerodynamic general rules of thumb that tell us, for efficiency’s sake, the thickest part of an airfoil should be 1/3 of the way back from the leading edge. This means that since the blade is 3″ wide at the tip, the thickest part of the airfoil will be 1″ from the leading edge. Making another mark @ the 30″ radius where the blade is 6″ wide, the airfoil will be 2″ back from the leading edge, and so on down the blade…
We also know that for strength’s sake, an airfoil should generally be at least 1/8 as thick as it is wide, but since this was already figured-in when we previously laid out & cut the root-to-tip taper on this side of the blade, we’re just about ready to shape the rear side and then ‘glass each blade.
Alas, I stopped working on these to get to the boys’ basketball practice a little early, giving me some time to watch them. The next game isn’t until 12/5. The blades will be right where I left them, but the boys keep growing and I’m going to cherish every minute of the gift that they are while I can.
Click Here to Leave a Response
