There has been some discussion about the correct length of blades for an Ametek 30. The recommendation has been to use 18" to 24" blades to optimize blade speed. Is it possible to limit blade speed in high winds by their size yet still get good speed for power generation? I have been flying 34" blades which admittedly have not produce well on my Ametek 38. I do get good start up and can make 12v in 12 to 15 mph winds. When we had 20 to 30 mph winds they did fine. At gusts of 50 mph they did not overspin the motor. I have 40" blades on the Ametek 30 now and they are too big. It does spin in light winds but not with any speed. I will be cutting them down to a shorter length. I am thinking about going to 30" to get good speed and hopefully not overspin the motor. Any opinions?
You can limit blade speed by blade design in a number of ways. You could go for more than three blades (more torque but lover vmax), or you can have blades that create sufficient drag that they won't go above a certain rpm. PVC blades from soilpipe are very cheap and easy but do create a lot of drag too. My last set of PVC blades was from about 60 degrees of pipe section instead of 90 degrees. It made the start up a bit worse but allowed it to spin faster at the top end. The difference was not huge by any means.
Personally I don't think I'd rely on blade design to be the sole means of limiting your max rpm as it can still go pete tong and I wouldn't want to be anywhere near when it does.
For me it's got to be a furing tailed chassis. Tried, tested and basic.
No, if you just off set the motor it will not furl.
The furling system involves off setting the motor and mounting the tail on a pivot at certain angles in such a way that the tail always stays in the wind direction, but the motor yaws out of the wind direction. Also, the motor off set and tail angles are calculated to balance right above the yawing pipe. Check this movie to see how the turbine furls: http://youtube.com/watch?v=qt-RmErz8vE
Can blades be self furling
Posted - 12/12/2007 : 15:52:27
