View Full Version : The "Safest" Rotorblade?
11-18-2003, 02:09 AM
I am planning to built an ultralight Gyrobee. I've been reading as much as I can on these forums, and a big question just came to mind. It seems that, too often, novice pilots can "unload" a rotor causing it to slow down and "flap" leading to... ... an unhappy event. I've also read that some rotors are more "efficient" than others but more difficult to spin up and more susceptible to "flap". Asking the ones who have been flying a while and/or have had experience with several types: Which rotorblade would you recommend as the "safest" for the newbie and why? ???<br><br>Thanks in advance.
11-18-2003, 05:00 AM
Doug,<br><br>I think you have some misconceptions about rotor blades and flapping.<br><br>You stated: "It seems that, too often, novice pilots can "unload" a rotor causing it to slow down and flap".<br><br>This is not true. Are you sure you read this? The only way to unload your rotor blades is to land (putting the load on the wheels) or to flip the gyro so the air comes down through the blades rather than up through them. Everyone lands - that's no problem. Flipping the gyro takes a combination of (1) a poorly designed gyro, and (2) a strong gust of wind or a pilot zooming up high then pushing the stick full forward to cause the gyro to tumble forward. Don't do this.<br><br>So, if you have a properly designed gyro don't worry. If not, get a new gyro or redesign it to have the prop thrust aim at the gyro's CG and have a horizontal stabilizer.<br><br>You also stated: "more difficult to spin up and more susceptible to flap".<br><br>This is not a safety issue. It is concerning flapping while on the ground during rotor spin up - not while flying. Once the rotor is "loaded" (off the ground) they spin fine.
11-18-2003, 08:04 AM
Ken, you didn't mention Zero g's<br>Zero g's (or low. or negative g's) will unload the rotor. <br> It is not necessary to have air coming in from the top(as in a forward flip.)<br><br>If any maneuver is performed, such as a sudden levelling off after a climb, which reduces the normal 1 g load on the rotor, it can lead to slowing of the rotor.<br><br>But, it is NOT the slowing down of the rotor that is the problem, since a momentary reduction of rpm can be tolerated. It is the loss of g force load itself which is the problem. <br>The 1g weight of the gyro is normally trnsmitted thru the mast to the rotor. Without weight, i.e. "weightless", the mast transmits no force and therefore cannot control the gyro. <br>Remember, the only way to control (a teetering rotor system) gyro is to use the rotor to "pull" on the airframe in the direction you want to go. A weightless condition is very dangerous since the gyro can roll or pitch over and the pilot can do nothing to stop it unless he reloads the rotor by gentlly pulling back on the stick The same remedy is recommended to R22 helicopter pilots, since it also has a teetering rotor and the same precautions apply.
11-19-2003, 02:59 PM
Thank you for the information you have supplied, but my question remains: what rotorblade is the most... "forgiving" in momentary lapses and errors by novice gyropilots? I realize that it's critical to have training, and I will do that; but I have read from many long-time flyers of mistakes they made. I also have read about various brands of rotors that seem more difficult to spin up and more prone to "flap". So, in your experience, which blade would you susggest a new flyer start out with?
11-20-2003, 02:53 AM
The safest most forgiving rotor blade is the McCutchen Skywheels blade.<br><br>Lot of inertia (forgiving and allows a long touch down period of time) and durable in case of a blade hit to the ground - the very best best for a beginner.
11-25-2003, 11:39 PM
Remember that angle of attack on the rotor disc determines RPM change. *Lower the angle and rotor slows down, increase angle and rotor speeds up. * The higher the forward speed the lower the RPM, reduction in disc loading reduces RPM. Always keep rotor disc loaded with at least 1G.
11-26-2003, 01:23 AM
Are you sure about that Randy?<br><br>I thought it was the load factor that determined the RRPM? <br><br>Pull 2 G's through a turn and the RRPM increases by the square-root of the load factor, just like the stall speed in an airplane. Return to level unaccelerated flight after the turn, and the RRPM returns to it's previous state.
02-06-2004, 08:36 AM
Remember Mike you cannot have a higher load factor without increase in angle of attack
02-06-2004, 09:19 PM
Rotor RPM is dependent on the load factor.
Angle of attack is dependant on speed into the relative wind.
Reduce your cruising speed from 60 mph to 40 mph and your Disc AOA will increase, but rotor RPM will stay the same.
Increase your speed from 40 mph back to 60 mph, and the Disc AOA will decrease, and rotor RPM will remain the same.
02-07-2004, 02:52 AM
Nicely explained Mike.
02-07-2004, 05:38 AM
Sorry paul, i have not the time to read all your valuable posts...Can you sum up what is your last experience with two blades rotor? did you try with four blades?
02-07-2004, 06:02 AM
AOA verus RRPM. Maintain the same speed and increase rotor disc angle of attack. What happens too rotor RRPM? It will increase due too the increased AOA and increased load factor. As AOA increases it will result in an increase in the load factor. It becomes which comes first the egg or the chicken? ::)
02-07-2004, 07:18 AM
AOA verus RRPM. Maintain the same speed and increase angle of attack. What happens too rotor RRPM? It will increase due too the increased AOA and increased load factor. As AOA increases it will result in an increase in the load factor. It becomes which comes first the egg or the chicken? ::)
Only momentarily, Randy.
Maintain the same speed, increase the AOA, and RRPM will increase only slightly because you have started a climb. Once the climb has stabilized to a steady unaccelerated state, RRPM will return to it's normal speed, which is dependant on load factor.
Same as in a turn.
02-07-2004, 06:29 PM
:o WOW! I really started something here! All of this is interesting, informative AND important, but my original questions was re: 'safe' rotors for a novice. One answer seemed to make sense... heavier is better because the inertia can keep it spinning during a momentary lapse on the new pilot's part. Now, is that true? Is a heavier blade inherently safer than a light rotor blade?
02-07-2004, 08:23 PM
IMHO, YES. The only disadvantage when using heavier blades is that they are a little slower to accelerate when hand spinning. With a pre rotator that will give you 160 RRPM there is no real difference in take off distance.
The opportunity of a "second bite of the cherry" while landing is an advantage to a low hour pilot.
Oh!! Yes there is a second disadvantage. Lifting them up onto the machine when you are reaching a more mature age!!!! LOL.
02-09-2004, 03:29 PM
Heavier blades take a moment longer to spool up for a flare or recovery from a descent. This isn't a huge problem, but it does require a bit more timing and anticipation.
I don't believe there's a huge safety difference between "light" and "heavy" blades. One of the lighter blades around, Dragon Wings, has tip weights and actually is quite good at holding RPM in "flywheel effect."
I believe Dragon Wings are used in Dick Degraw's jump takeoff machine, where good flywheel qualities are critical.
03-19-2004, 06:17 PM
So you the dragon fly are best for novice?
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