djcmeeks

My Feedback: (11)

Wanted to get opinions on multi-blade setups from those who have had experience with them. I have a Trex600CF electric that I am about to install in a Funkey Hughes 500E fuselage. I am tempted to replace the stock head with a 5-blade setup for looks, but I am not very clear yet on what the Pro-s and Con-s would be. How much would the flight characteristics change? (very drastic?). Is it easier or harder to get a good blade balance? (I know standard two blade setups can cause a lot of vibration which lead to fuselage havoc).

I have read that extra stabilization may not be necessary on a multi setup, but I see that many vendors that sell multi-blade heads also offer 3-axis gyros. How much do the gyros help?

These are just some of my questions. Any input would be appreciated!

BarracudaHockey

My Feedback: (11)

http://www.scaleflying.com has the 5 bladed head for 10mm shafts that would fit that heli.

Some argue on the need for stabilization systems. I bought one for my 4 bladed Koala R50 project with that same head.

djcmeeks

My Feedback: (11)

So it sounds like you think your 4-blade setup flies fine without gyro stabilization for the head? What would you say your skill level is? I can handle my 600 fine. I am used to sport and light 3d (rolls, etc.) with my 450.

ea01bg

A friend of mine runs a four bladed head on his Trex 450 without any stabilization. He put extra weight in the nose. He said that it offsets the tendency for the heli to try and balloon up in forward flight as he described it. He just test hopped his Trex 600 with a 3 bladed head and said it flew well without a stabilization package but would need the nose weight or a stabilization package. He went with the stabilizer and installed the GU-365 .
I should note that this guy has been flying helis for years and I’m sure that his advanced skill level must come in to play to some extent.

Ruizmilton

My Feedback: (29)

This is what I can tell you from my multiblade experience, in most respects I felt that response around the centering of the cyclic seems more sensitive compared to a flybarred head, yet that's where it ends, meaning that after you bank or pitch a few degrees from center the fast response ends, the machine had more of a "float" feeling compared to a flybar head, and dissimetry of lift (retreating blade stall) is more noticeable, not that it is something that does not happens to the flybar head, but the flybar will compensate for that making you feel like it does not happen. Same goes for the "ballooning", some flybar heads still exhibit this tendency, yet in most it is compensated properly by the flybar, so I guess it all goes back to really understanding how a heli flies and applying this understanding to the way you fly.

Aside from what a flybar stabilization mechanism will do, everything else is the same. A stabilization system provides the same correction ability of a flybar by reducing dissimetry of lift and balloning, but if you understand how the machine flies and learn how to adjust there is no need for them. A mixer allows you to change swash timming, below you'll see you can do that in your computer radio with no need for an external mixer. What a mixer does provide is the ability of mixing a gyro output to three controls, that is important ONLY if you want to have stabilization on a CCPM system where all comands are shared by all three head servos as opposed to a single servo collective where elevator is one servo and aileron is one as well.


Most issues related to multi blade set-ups are related to swashplate phasing, there are two reasons:

1)The more blades you have, the less space is available on the rotorhead and swashplate to accomodate the required 90 degress from swash control ball to blade holder control ball, this happens on rotorheads with 5 blades or more. This can be corrected by swash mixing to compensate for where your pushrod will be located in relation to the machine's centerline on fore/aft lor left/right orientation in order to compensate for the required amount of degrees to reach 90. In a 5 blade head you only have 72 degrees between each blade, so in order to have all pushrods perfectly vertical to avoid binding and non-linear response, you cannot achieve the 90 degrees required between the swash ball and the blade holder ball, but by properly mixing aileron to elevator and elevator to aileron you can "rotate" the swash timing so that a command happens 18 degrees later (or earlier) from the centerline of the fuselage. If it has to happen earlier or later depends on wether you have a leading edge or trailing edge controled blade holder and your rotor's rotation direction (CW or CC). Any computer radio can do this, there is no need for an external mixer.

2)Tendency to run head at a lower RPM than required to stabilize, every head/blade combination is different and the minimum specific RPM required to achieve stability on the system has to be reached before the head will respond to the inputs on the 90 degress due to gyroscopic precession . This RPM/phasing issue does not happen on flybar heads because your swashplate does not directly control the blades, the flybar does, the flybar is mechanicaly positioned at 180 degrees to the main blades(up/down travel of a paddle will always be at 90 degress from a main blade) and is controled aerodynamically, meaning that AIR FLOW controls it, so there is no gyroscopic precession de-phasing, PLUS, there is stability added by the flybar, meaning that control input will always affect it in the correct phasing, try to picture it and you'll see what I mean. If the rotor head would have responded to an input with a 45 degree lag due to low RPM(you give forward cyclic but head goes forward and left) the fly bar would give a "right" correction to the blades, but no correction to the "forward", left and right would cancel each other and you would only get a forward response.

Makes sense????

jaycab

Very good & elaborated . Thanks for shearing the info

djcmeeks

My Feedback: (11)

Thanks for the detailed explanation of the anatomy of the flybar head vs. a multi-blade head. This definately helps with my decision. I think I will stick witha flybar head on my 500e scale fuse so I don't crash my investment. I will probably experiment with a multi-blade on a standard bomm and pod heli til I am fully comfortable with flying it and setting it up properly.

toto_sal

What is the general rule of thumb when going from a 2 blade setup to a 4 blade setup with respect to blade lenghts? I am building a TT Augusta A109 with Raptor 90 mechanics Century Heli 4 blade head...

Would really appreciate the help!!!

Luis