I started shaping the wind turbine blades yesterday, after having this project systematically knocked down the “things to be done” list. There are only so many hours in a day and we need to be intentional on how we spend those hours, the hours turning into days, weeks, years, a lifetime and a legacy.
Thanks to the medium of the Internet and blogging, you can tell at a glance when was the last time I did something on this, but I had to look back to find out I haven’t touched it much since June of this year. Those hours I just wrote of quickly turned into months.
Having some successful experience cutting large and small props for my hovercraft some years ago, I originally started cutting these blades to shape immediately after confirming the alternator did, indeed, generate useful alternating current. But then I set out to find a quicker, easier way than the last time to make them a reality. I wanted a more effortless way to remove everything that didn’t look like blades from the blocks of wood, “roughing them in” if you will, the correct shape being finalized with the rotary sander. The hunt was on for a wood-cutting bandsaw that could handle 8″ tall material.
I won’t say here that I was diligent in my search, enjoyably working through the outage projects at work, laying hardwood floor in the house, etc; but five months later, I look back through the realization that if I had started cutting these out by hand back then, I would’ve been done by now. Ever been there? Maybe with saving, investing or from some other seemingly unrelated position in life? It all ties together. So I started.
Thanks in no small part to the Wright Brothers, we can now take it as a simple fact that the back surface of our blades will need to have larger surface areas than the fronts to create low pressure areas behind, helping them to “pull” through the oncoming wind, increasing unit efficiency.
The fronts then, should be flat but tapered from “leading end” to “trailing edge” into the wind; the backs a functional airfoil tapering to a thin, but not fragile, tip. And since this machine will be safely anchored to my backyard, I’m going to use some simple design generalities and a few accepted aerodynamic structural “rules of thumb”. No need to worry about “accelation vs. cruise”, “climb rate”, or any of the multitudinous other considers otherwise taken into account when designing propellers as long as : the tips don’t go supersonic (mine ~60mph @ cut-in, calc here), they hold together in high winds, and are relatively efficient. Other efficiencies could be better made in the machine itself (and will be on the next), rather than spending more resources on a lesser gain here. “Think: ROI”.
Going by hand, you can see how far I got with the roughing-in last night:
- I’ve tapered the backs of the 3 blades (where the airfoil will be) from the “root” (part closest to hub) to “tip” (farthest from hub)
- Marked out “kerf marks” on all three fronts (the flat side) and cut one to check my “leading edge” to “trailing edge” taper.
I still have much more to do and will be happy to share the particulars of the design and “what’s coming & why” with anyone interested, but parts came in for the ‘58 and I’m going to run out and pick them up while the boys are in school.
