proper tail rotor rpm

[brianapp]

I know a lot of other things need to be considered but in general what tail rotor rpm is need for proper tail operation in the 450 size? I keep having bounce back, holding, and mushy problems that I don't have on bigger sizes and it might be because I have the main rotor down to 2900 which is a bit slower than designed. I will of course need to look up the gear ratio to get the tail speed but if you know a good speed to shoot for I can adjust to get it.

[Highspeed1964]

I don't know exact speeds, but a tail to main rotor ratio of around 5.5:1 - 6:1 is good. At slower head speeds you may even need to go a bit higher (say around 6.5:1).

Hope that helps,

Highspeed

[brianapp]

It is not the ratio but the actual RPM I am looking for. I want to know if a slow tail rotor is the reason I keep getting tail blow outs when inverted with moderately aggressive collective or cyclic inputs. If I am inverted with just a slight wind if I am not gentle on the collective it will just spin like a top.

[FrankFuss]

Originally Posted by brianapp

I know a lot of other things need to be considered but in general what tail rotor rpm is need for proper tail operation in the 450 size? I keep having bounce back, holding, and mushy problems that I don't have on bigger sizes and it might be because I have the main rotor down to 2900 which is a bit slower than designed. I will of course need to look up the gear ratio to get the tail speed but if you know a good speed to shoot for I can adjust to get it.

I did not have any problem with the tail on my T-Rex 450Ls at headspeeds of 2600, 2800 and 3000, with FBL controllers Spektrum AR7200BX, Skookum SK-720BK, and Spirit. You must have some problem with your tail setup. The tail linkage and slider must be perfectly free and the ball on the tail servo arm is best move in to 7-8mm from center.

[Highspeed1964]

Copy that. I understand what you're looking for. Again, I'm not sure of the RPMs for the tail rotor. However, running lower RPMs in general will give you less control authority on the tail. So it is quite probable that this is why you're having trouble getting the tail to lock in and having blow-outs.

There are two ways to fix this:

1. A higher ratio which will produce higher tail rotor speed.

2. Larger tail rotor blades.

The first is not easily achieved as you'll need different gears. Most models are designed for a specific ratio and you most likely won't be able to find gear sets for anything but what the original design calls for. So the easiest way to improve tail authority/stability is the second option.

For example, if the tail rotor blades are 62mm change them out for something like 67mm. There are a few choices available in rotor blades sizes (certainly more than trying to change the rotor RPM. You may have to experiment with a couple of different sizes to find one that gives the right feel you're looking for.

Highspeed

[RC/DC_5000]

Do you have the Pro size tail blades on? If you put on the Dominator 68mm tail blades, it'll help with your anti torque thrust. Bigger tail disc will scoop more air.

I fly a governed 3000 rpm with my 6s Dominator... and smack it to death.. Rip inverted funnels... Tail holds great. I have the Gpro with the PID gains cranked up and an MKS DS8910A tail servo.

You might also try tuning up your FBL system. PID gains for the tail.