found this which should keep me busy for a while. its interesting that the way this profile works from the results chris is getting does seem to follow the CFD calculations. do your s809s have the same twist as dan or hugh type blades?
I got two different S809 blades - the PowerMax ones and the WindMax ones. The PowerMax blades have considerably more twist than the WindMax. My guess is 18-20 degrees of pitch at the root and maybe 1 - 1.5 degrees at the tip. The PowerMax airfoil is thinner and has more taper - on the 13 foot blades they're about 10.5" wide at the root and about 4" wide at the tip.
The WindMax 13's have less taper - they're not as wide at the root and they're wider at the tip. They're also fatter and have less twist. I'd guess about the same 1 - 1.5 degrees at the tip and maybe around 10 degrees at the root.
The PowerMax blades, in my experience, have a wider power band - but they are very weird compared to what most people are used to in flat face. They'll happily run at a 5 TSR under heavy load in low winds - in fact, they refuse to spin up beyond that in low winds. But once the wind picks up the TSR climbs and to get the optimum out of them your generator needs to let them spin at 6 TSR around 18-20 mph, and 6.5 TSR is even a bit better if you can live with the later cut-in. They are VERY noisy - they sound like somebody whipping three big cables thru the air at 200 mph in higher winds.
The WindMax S809's don't seem to put out the low end raw torque of the PowerMax ones. But once the wind gets blowing at 10-12+ they'll match the PowerMax blades in output, and maybe even exceed the PowerMax performance at 25-30 mph with a generator wound for a 6 TSR blade.
The PowerMax blades are high-quality, they come balanced, and with a gloss white finish. All you have to do is sand them a bit if you want to paint them a different color - and bolt them on. They are strong - you can lay a 13 foot blade across two sawhorses, climb up on the blade and jump on it - it'll bend 30 degrees with my 200 lbs jumping on it and it won't break or crack. Those blades will outlast the turbine they're bolted to.
The WindMax blades take a lot of work. They come with big ugly seam lines hanging out the leading edge that have to be sanded down. And when you sand them you'll find voids in the fiberglass that have to be repaired. On the 9.3 WindMax blades that I got I had to hang almost a pound of weight on one blade to balance them. They are cheaper than the PowerMax ones and my guess is that if you get two years out of a set you'll be doing pretty good and then they're going to start coming apart.
Attached is three photos - the first is of the 8 foot PowerMax blades that I bought, just as they came out of the box. The second photo is the PowerMax blades on my 10 foot turbine when I took it down and replaced it with a 13. The third photo is a set of 13 foot WindMax blades after I got them finished - you can see right away the difference in the design even though they use the same airfoil. The PowerMax blades need to run at higher TSR if you're looking for max performance - they're designed for it. While the WindMax blades resemble big paddles, the PowerMax blades have more curves than a hot babe, and they look as good too.
One thing to note about the size of these blades - they must use a Chinese tape measure of some sort to measure the 13 foot WindMax blades because they're actually about 12.5 feet on my hub. The PowerMax 13.1's measure exactly 13 feet on my hub.
Building a generator for the PowerMax blades is a bit of a mystery. I've found that winding for a 6.0 TSR is about the optimum. They'll cut in just a tiny bit later than you'd like, but there's no power in those low winds anyway. And they'll deliver awesome performance at about 18-20 mph. Above 20 they seem to peter right out and just don't put out any more power. However, and this is a BIG however - if you wind your generator to let those blades spin at 7-7.5 TSR in high winds you'd better be prepared to be winding new generators every time the wind blows. If you let those blades come to life at 24-30 mph wind they cannot be stopped. They'll lug down to about a 6 TSR and they will just PULL. The shorting switch should be labeled the Mass Destruction Switch, or maybe the Mass Meltdown Switch if you try to shut one down that's spinning at that speed. BTDT, and ever since I've learned to keep them stalled in higher winds or you'll have a runaway.
The WindMax blades don't appear to do that - they don't like to run at 7 TSR. 5-6 is all they'll do under load, and they may get to 8.5 TSR or so with no load. I think they're too fat, to wide of a tip and too much drag to run at high TSR. OTOH, if you remove the load from a PowerMax rotor that's running fully loaded at 18-20 mph it's like somebody threw the Turbo Boost Switch and plugged off the wastegate with a wad of silly-putty - those blades will hit scary rpm's within about 1/2 of a second. They light up like instantaneously - it's no gradual deal. if you don't have your magnets pinned to the genny rotors you'll be searching for your magnets in the next county. BTDT too.
Hope that explains what I've discovered about these blades. My conclusion after trying both of these commercially available blades is that for $285 for a set of 13 foot PowerMax blades, and the gain you get in performance vs flat-face, you can't mess around carving wood blades. I think the quality fiberglass blades are safer and stronger, they require less maintenance over the long run than wood, and they are not affected by moisture. If you have nothing else to do I suppose you could try to make them yourself. But getting this airfoil exact, according to what I've studied, is not an easy thing to do. It won't run at high angles of attack like flat face will, and continue to work. And the exact curvature of the wind-facing side is very important to how they work. I suppose you could buy one, measure it up and enter the coords to machine them with CNC. But again, for $285 for a set of 13's, why even bother?
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Chris
