3, 4, 5 blade head for my .50 size heli
07-14-2008, 10:40 AM
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3, 4, 5 blade head for my .50 size heli
I fly a .50 size heli with the .52 redline engine. I am wondering; if I want to go to a 3, 4, or 5 blade head what considerations do I have to take into effect. Will I have to use shorter or lighter mains? I assume my pitch curve and throttle curve that I am using now will have to be reset. Will I have to use a slower head speed? Will the heli fly differently than with a 2 blade system? Is there more gyroscopic effect due to more mass? Does this make the heli slow to respond to pitch and role? I have questions folks… Or perhaps there is there a link that I could go to so I can learn all there is to know about multi blade heads?
07-14-2008, 03:04 PM
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RE: 3, 4, 5 blade head for my .50 size heli
hey av8r,
there are many things to do when switching to a multi bladed head. if the machine has already been flying reliably with the flybarred head, you are halfway there. the best thing to do first is copy the heli's program to another blank memory in your radio and name that one for the five bladed head. this is the program you will change for that head. much of the change and adjustments willbe to the pitch and throttle curves. withthe head installed you wont need quite as much movent of the swashplate for collective. on that machine, you may find it hovers with about 3 degrees of pitch at half stick. at full stick, 5 maybe 6 degrees is about all yo may need. at low stick, about -2 degrees.
as for blade lengths, thats determined by the head. some heads have the blade grips further out from center than others and this is especially tru with 5 bladed heads. get the head first and see how far out to the tail gearbox the tip of the blade is when mounted in the grips. i like the tips to stop where the arc of the t/r blade begins.
multibladed heads fly, handle and respond differently than a flybarred head. not any more difficult mind you, just different. in the hover with little or no wind, usually they feel exactly the same. in fwd flight, things are a bit differently. cyclic response can be adjusted to feel comfortable just like a flybarred head. more end point makes it more responsibe ot touchy and less end point gives the reversed effect. when it comes to multibladed heads, the blades are what makes or breakes the way it flies. ideal blade design is a narrow chord, and lots of weight at the tips spanwise, and in the leading edge chordwise. the cg point being far forward in the chord is what makes them fly well.
headspeed tends to turn out a little lower because you are getting more lift for a given rpm and if your engine will let you get away with it, go for it. this is usually only possible with the bigger bore engines tho so dont count on it too much. if the machine is heavy with details and cowled up with no many holes to pull air from, then dont count on running a lower head speed at all. it seems to be scarier with a multibladed head turning say 1700 rpm than it is with a flybarred head, at least to me. so long as the engine is running at its tolerable rpm, the head speed should be okay and not scary. if the head has thrust bearings(which they should0 the worry is even less.
the trouble most people have with multibladed heads is PHASING or TIMING of the blades. this is a very important part of the setup. correct timing ensures that when you move the cyclic stick forward or backwards or anywhere in between, the head will respond in the same direction. for me, phasing/timing is the easiest thing to do and i can do it in less than ten seconds but it is the hardest thing to explain to folks on the phone or by email. at ircha this year if i am asked to do a scale workshop again, that is the subject i am planning. i have spent the better part of an hour explaining how to do what takes less than a minute to show ya
this isnt meant to scare you, but it lets you know whats involved. most realize whats involved only after making a multihundred dollar investment and it can be a turnoff. multibladed flying however is quite fun though it just keeps you a little more on your toes because we have been so spoiled by the flybar
there are many things to do when switching to a multi bladed head. if the machine has already been flying reliably with the flybarred head, you are halfway there. the best thing to do first is copy the heli's program to another blank memory in your radio and name that one for the five bladed head. this is the program you will change for that head. much of the change and adjustments willbe to the pitch and throttle curves. withthe head installed you wont need quite as much movent of the swashplate for collective. on that machine, you may find it hovers with about 3 degrees of pitch at half stick. at full stick, 5 maybe 6 degrees is about all yo may need. at low stick, about -2 degrees.
as for blade lengths, thats determined by the head. some heads have the blade grips further out from center than others and this is especially tru with 5 bladed heads. get the head first and see how far out to the tail gearbox the tip of the blade is when mounted in the grips. i like the tips to stop where the arc of the t/r blade begins.
multibladed heads fly, handle and respond differently than a flybarred head. not any more difficult mind you, just different. in the hover with little or no wind, usually they feel exactly the same. in fwd flight, things are a bit differently. cyclic response can be adjusted to feel comfortable just like a flybarred head. more end point makes it more responsibe ot touchy and less end point gives the reversed effect. when it comes to multibladed heads, the blades are what makes or breakes the way it flies. ideal blade design is a narrow chord, and lots of weight at the tips spanwise, and in the leading edge chordwise. the cg point being far forward in the chord is what makes them fly well.
headspeed tends to turn out a little lower because you are getting more lift for a given rpm and if your engine will let you get away with it, go for it. this is usually only possible with the bigger bore engines tho so dont count on it too much. if the machine is heavy with details and cowled up with no many holes to pull air from, then dont count on running a lower head speed at all. it seems to be scarier with a multibladed head turning say 1700 rpm than it is with a flybarred head, at least to me. so long as the engine is running at its tolerable rpm, the head speed should be okay and not scary. if the head has thrust bearings(which they should0 the worry is even less.
the trouble most people have with multibladed heads is PHASING or TIMING of the blades. this is a very important part of the setup. correct timing ensures that when you move the cyclic stick forward or backwards or anywhere in between, the head will respond in the same direction. for me, phasing/timing is the easiest thing to do and i can do it in less than ten seconds but it is the hardest thing to explain to folks on the phone or by email. at ircha this year if i am asked to do a scale workshop again, that is the subject i am planning. i have spent the better part of an hour explaining how to do what takes less than a minute to show ya
this isnt meant to scare you, but it lets you know whats involved. most realize whats involved only after making a multihundred dollar investment and it can be a turnoff. multibladed flying however is quite fun though it just keeps you a little more on your toes because we have been so spoiled by the flybar
