Article 5: Setting up the Hirobo Sceadu Evo FZ-IV head

With the assembly of the FZ-IV head completed, the next step will be setting up the linkage rod length.

My linkage rods length are as below:

1. Stabliser control rod = 17mm (measuring only the part of the rod not covered by plastic rod end)
2. Mixing arm rod = 40mm (measuring only the part of the rod not covered by plastic rod end)
3. Pitch rod = 31mm (from centre of ball to centre of ball at the other end)

With these rod length, I can get -10 to +10 degrees of pitch. Please note that the Evo manual suggest using the lower hole on the main mast. Sceadu manual recommends using the upper hole. Another note is that the pitch rod should consist of a piece short and fat rod end and a piece of long and thin rod end.

If the pitch rod uses 2 pieces of fat and short rod end, it will cause binding and drastically reduce the collective pitch range. Use a piece of fat and short rod end for the top part and a piece of thin and long rod end for the bottom part.

The programming settings in the transmitter required only 1 change. In my JR X3810, I just need to reduce the ailerion travel adjustment (ATV) to 115% left and right from the previous 130% left and right. Next, I rotate the FZ-IV rotorhead with extreme cyclic and collective pitch input to check for binding. I'm glad that there is no binding.

Left : The FZ-III rotor head before upgrading.

Right : The completed FZ-IV rotor head. Note the bigger stabiliser control arm.

The bottom view of the FZ-IV head. I have replaced the radius block with the metal one because I have broke the plastic one when I was assembling the rotor head.

I'm happy that the upgrade is finally completed. I encountered some problems with the linkage rod length but I managed to solve it. I have put the mixing arm position at the inner hole on the see saw because I wanted to see how "mobile" this new rotor head is.

The Sceadu with the upgraded Evo FZ-IV rotor head was brought to the field for it's maiden flight. I started off with normal mode and hovered the heli with the head speed at 1600rpm. I did some trimmings. As I am using the "high mobility" setting, I expected the heli to feel sensitive. So I put in 30% exponential to soften the feel when the stick is at centre. I am glad that with these settings, the FZ-IV feels stable. Then a sudden gust of cross wind came! Grinning cheek to cheek, the Sceadu just sits happily in a hover, and required only very minimial corrections. This is better than the older FZ-III rotor head. The feel is very close to the bigger Freya that my flying buddies have.

I proceed on to trim the heli in idle up 1 and idle up 2 settings. I'm running 1700 rpm for idle up 1 and 1750rpm for idle up 2 because I'm using the TT wooden blades and they are rated up to 1800rpm. I took a deep breath and put the Sceadu into forward flight. She goes up straight into the air and then turn around with a stall turn. Flying into fast forward flight, I put her into a loop. Ok, feels the same as the FZ-III head. Then another stall turn and I put her into a roll. I exclaimed to my flying buddyies "Look at how she rolls! Like an arrow!" This is where the FZ-IV beats the FZ-III, the cyclic response is much faster. I like this type of response because I prefer to fly freestyle patterns.

The Sceadu with the FZ-III rotor head has the infamous "flutter" when improper blades are used. I have a pair of Worlds Model FRP blades which flutter on the FZ-III. So I changed out the TT woodies and put in the Worlds Model FRP blades. Then I ask my flying buddies to check if there was any flutter while I put the Sceadu into a series of descents. I did some high speed and low speed descents and I'm happy that my flying buddies reported that there was no flutter and the blades made the overall response of the heli much "crisp". The TT woodies can flex when the heli undergoes hard flying. The FRP blades are much stiffer and do not flex much. Hence the feel is more "crisp"

My conclusion is that Hirobo has stuck another jackpot with this newer FZ-IV rotor head. This is a Sceadu with an upgraded rotor head and it already flies very well. The complete Evo kit contains more upgrades that make the heli flies even better. So, should you upgrade now? In my humble opinion, you can fly the FZ-III rotor head until you do a chicken dance. Then do a rotor head upgrade. However, if you are a freestyle wannabe and desire for better cyclic response, the S$50 upgrade for the rotor head is quite worthwhile.