When you have finished your scale beauty, often the finishing touch is fitting a flybarless head with either 2 or maybe lots more blades. Setting these up is essentially the same no matter how many blades there are. The first thing we need to think about is the linkage. Hopefully the manufacturer of the head/model will have given you measurements of the links from the swashplate to the blade. If not, have a guess and make up a link. In either case. Make up only one link for now and work on one blade. Then when one is correct you can make up the rest.

The swashplate driver is a device to lock the center of the swashplate in position relative to the mast. It allows the swashplate to rise and fall but not twist. When you first fit this, you can put it in an infinite number of positions and as you move it, the pitch on the blades will alter. Hence, the exact length of the link is best determined when the timing is done. The timing is a function of an effect called precession which means that any input given to the disk, will happen 90 degrees later. However this only happens when the disk is nearly up to speed and how it knows that, is something I have yet to work out.

This is the 5-blade head I fitted to Xcell mechanics for my Seaking. Note the pushrods are straight and hefty. Setup your multiblade head so that the pushrod is straight and temporarily tighten the driver set screw. Now move the blade so it is over the tailboom. Switch on the radio and move the AILERON. I suggest for setting up you put in lots of exponential on the aileron and elevator to ensure there is no inadvertent interaction. At least 75% should do it. Now, as you move the AILERON control. The blade pitch should alter. If you move the ELEVATOR control, the blade should remain still. Turn the driver until you obtain this and snug it down again. If the pushrod is not vertical and you have the ability to adjust the swashplate timing via your radio, now is the time to do this. I am familiar with the JR PCM10X and it has timing as one of the options under swashplate, but the range of timing is limited. Adjust the system mechanically and electronically so that there is no interaction between elevator and aileron and the pushrod is as near vertical as possible.

This is a 4-blade setup using a Vario Bendix head on a Vario Boxer. As you can see, the pushrods are not vertical, but they are quite within reason for use. Note also the driver center is about horizontal and that the blades have about zero degrees pitch. Set your driver at about the same setting. Check again that there is no interaction, and then put the blade out at right angles to the boom. If you move the ELEVATOR control the blade should move and if you move the AILERON it should not move. Optimize the electronics and mechanics for the best results and the timing is done. Make up a pushrod which will allow 0 degrees pitch on the blade with the driver center horizontal and then do the normal setting up of the pitch curve. Finally make up the other pushrods and check everything works as it should.

Multiblade tail rotor setups are much simpler as they require no setting up, but if you are going to more than 3 blades you may need to reduce the blade size in order to keep the control system in balance.

This brings us to the consideration of which blades to use. Vario insists that its Bendix heads be used with special blades that have the Center of Gravity well forward. In most fiberglass and carbon fiber blades, the weight is a strip of lead placed right along the leading edge of the blade so the C of G can't get any further forward than that. Wooden blades have slots milled them to accept the weights and they may be a little further back from the leading edge. I strongly recommend you use Fiberglass or carbon blades on any scale machine. Wooden ones simply aren't consistent enough.

A word on Vario’s blades is in order here, but I must firstly state that these are my findings and opinions only. Vario makes 2 basic types of blades, narrow chord and wide chord. I first tried narrow chord ones on my first EC135 and they were the elastomeric blades that had the bearing inside the blade. The helicopter flew, but was very nervous on the tail, and I believed it was due to the inefficiencies in the Fenestron tail rotor system. I disliked flying the model so much; it was hung up and became a hanger queen.

Some time later on, I built a Century Seaking with Xcell mechanics. This flew very nicely with the stock 2-blade flybar head. I really enjoyed cruising this machine around and it looked great in the air. I decided that it really needed a 5-blade scale head and tail so I ordered the head and blades from Vario and the tail from Century. The tail worked fine with five 30-size tail rotor blades. Then I fitted the head and Varios Bendix blades. I needed the thick root blades, as the thin ones were only available in left-hand rotation and the Xcell was right hand. We finally got the head set up and spooled it up. Even on full throttle on 30% nitro fuel, the helicopter would only just lift off the ground.

My friend and helicopter guru Ewald Heim was with me at the time and we struggled for a while to get this thing to do more than hover at full power before we gave up. The problem was in the efficiency of the blades. The narrow chord blades were simply too inefficient to lift the helicopter off the ground. I needed more power. I went to Tim Schoonard and asked what he had to help and the answer was to fit a 95 tooth main gear this reducing the gear ration from 9:1 to 9.5:1. This allowed the motor to spin up more freely and work higher up in its power band and this gave me the power I needed to get the helicopter off the ground with some margin for error. However, the machine was now very nervous on the tail and the head wasn’t stable at all. What was going on here? Well before I spent too much time on it someone forced money into my hands and left with the fuselage, heads and a warning from me to fly it with the 2-blade head.

Then I bought another EC135 that had been built by a professional for a local guy who simply couldn’t get it to fly properly. I solved the immediate problem and then started to fly it around. I found I was using more and more left rudder to keep the machine straight. At the end of the first circuit I couldn’t stop it from turning right over the pits without banking it and hauling lots of elevator so I got it down pretty fast at the other end of the field away from any spectators. Again, this machine was using narrow chord elastomeric blades. I fitted speed up gears in the tail rotor system and the latest tail rotor blades with still no improvement. Another hanger queen? Well again someone came along with more money than sense and it went elsewhere.

Finally this all clicked in my mind. The EC135 I had in England was very marginal on tail rotor control, and only just had enough control to hold it against the torque but barely enough for a left turn. The American one was even worse. This is because the narrow chord blades are very inefficient and need lots more power to lift the machine off the ground. The extra power has to be countered by the tail rotor and its characteristics matched by the electronics in the gyro. This gave me the reason why the Seaking was so nervous; the gyro was designed for a model that would react in a certain manner when the tail servo moved. The narrow chord blades and straining motor were so different in character from normal; the gyro was constantly under controlling and making up the difference which made it feel nervous.

I decided to try another head system on the EC135 in England. I fitted one from the Vario gasser with Vario wide chord FAI blades. Bingo! I had to reduce the sensitivity on the rudder dramatically, as the rudder was way over controlled now and I ended up with 80% exponential on the transmitter to keep things calm. I also tried the Skyfox aerobatic head, and it was exactly the same with those blades. The model flew beautifully and was as smooth as silk. Just as I expected it to fly in the first place. The other thing was, you can’t tell how many blades it has when its flying, but the 2 blade head is not as pretty as the 4 blade one when the machine is on the ground. It depends whether you want to fly it or look at it I suppose.

Vario are aware of this problem and other problems in the elastomeric blades and are in the process of redesigning them so hopefully they should have their new line in production when you read this. This is written in September 2000.

Now having knocked Varios narrow chord blades, I must comment on their wide chord blades. I have always used TG blades on my pod and boom machines. I think they strike a perfect balance between aerobatic performance and auto rotation performance. Their semi symmetrical blades have superb auto performance and are very difficult to beat in my opinion. When I built my giant 300C the only left-hand 820mm blades I could find were Vario. I used a set of these and was content with their performance, both flying and in the autos. I also ordered a set of TG’s as I knew they would be superior. They finally arrived and I fitted them. I found to my surprise that they had much less lift than the Vario blades! So I am happy with Vario wide chord blades every where I use them.

When it comes to flying a flybarless head, you need to be aware that as you spool the head up and move the cyclic, the disk will not move as you expect. It may move in another direction all together and then corkscrew around to the correct place. Don’t worry, this should happen until the head is at flying speed. Just before takeoff, everything should be stabilized and now, if you tip the disk forwards it should go forwards. When you have familiarized yourself with the hover and are into forward flight, don’t forget to control the height with the collective. My biggest error is trying to control the height with the elevator and of course when I do this the helicopter flies faster and climbs even more. Fly slowly at first until you get used to it, but fly it often or you will never become familiar with it and it will always be a bit intimidating.

Chapter 9