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GM1
05-23-2006, 07:39 AM
1. Decide which model you are going to build and if it has options, like multiple heads or gear ratios, decide which you want and need. In my case, I run the YS 91 so select a 7.91 gear ratio, and I use the MA Tempest FAI rotorhead because it is SO adjustable and has good characteristics in hover. I selected the MA Stratus FAI as it is light, durable, flies well, and I'm a sponsored MA pilot <G>.
2. Build the model. Make it straight and make it to fly, not crash. I Loctite all bearings to the shafts and blocks. It's a pain in the tail to take apart BUT I never have a bearing spinning in the blocks and making radio noise and the model lasts nearly forever with just routine maintenance. Take your time and align and balance EVERYTHING. If the fan is not on the motor with runout less than .001 inch , it will never be smooth in a hover. If the motor and clutch are not aligned with each other and the main gearing, the model will never be smooth. Take your time and get it RIGHT. A screw up here means the model will never be as good as it can be.
3. Install the radio and here's where the fun begins.
Set the radio for midstick everything. As you install linkages make sure all servo arms are at 90 degrees to the rods. Put all sliding things in the middle of their travel and adjust linkages until it is mechanically perfect, all bellcranks level, all mixers level, etc.
I'll add some more here as I get time.
Gordie

Gary O
05-23-2006, 09:21 AM
Great stuff Gordie, at least I know I'm on the right track from what you've just posted.

GM1
05-23-2006, 10:05 AM
Okay, we have the model built, everything is balanced and aligned, radio is installed and, at midstick, everything is in the center of the travel, mixers are all level and all linkages are at 90 degrees to the servo arms and bellcranks. Decide what the maximum pitch ranges you will ever need are. For the 2004 schedules I used -8 to +12 so I'll use that here. The process is the same no matter what pitch range you are using. -10 to +10 is the same, middle is zero. Calculate the center of the pitch range you are using: ie. -8 to +12 is 20 degrees so cut that in half, 10 degrees so add 10 to -8 and you get +2 so my center pitch should be +2 degrees so I have 10 above and 10 below. Adjust the pitch arms to give yourself +2 degrees at the blades, servos still at 90 degrees, mixers still level, still at midstick.
Maker sure your pitch ATVs (AFRs) are at least 100%. Go to full positive stick and see how much pitch you actually have. If you have 15 degrees, you need to use a smaller servo arm on an mCCPM model or cut the swash mix pitch in an eCCPM model, if it is only +9 use a longer arm or more swash mix, and again make sure everything is 90 degrees and level at mid stick. Check low end pitch and make sure you are getting -8 (or whatever) if there are very minor differences, you can add or subtract ATVs but it should be only a very small %, 3-5% at the most. When you are satisfied, go to your hover pitch curve in the radio and raise the curve so that midstick (if you hover at midstick) is 4- 4 1/2 degrees (you will change this to get the model to hover at the selected rpm at exactly midstick). I make a straight line from full pitch to hover to low stick, usually something like -3, 4.5, 12 at low, mid, high. I always make sure I have a little negative pitch so I can "glue" the model to the ground when hovering in the wind. I may slightly flatten the middle of the curve to make the model less touchy right around center. I don't worry if I have excessively high pitch, I may overdrive to +13-14 to get the "feel" I want in hover but I will NEVER go to full pitch/power in normal so I don't even worry about being overpitched.
I then set my idle up pitch curves -8 to +10 (or whatever the motor will pull) in a straight line. The centers of these two curves (normal and idle up) don't match since normal is at +4 degrees at midstick and idle up is +1-2 at midstick but the motor is only turning 1450 in hover and goes to 1950 in idle up so the change isn't as bad as it sounds and I usually only pull into idle up as I leave the box and am powering up and climbing. All that happens on my model when I pull the idle up switch is that the motor revs up and the model hauls butt. I set my throttle hold curve as a straight line from -8 to +12. Now I rarely ever go to -8, come down usually around -3 to -4, but use the -8 if I am going to overshoot the spot and can go to -2 or even 0 if I need to stretch to the spot.
More later.
Gordie

GM1
05-25-2006, 07:03 AM
Vol III

You have all the pitch curves set to match what you think the motor will pull, so let's think about cyclics. There are two very diverse points of view here. One camp runs a very low cyclic rate so no matter how far you move the stick, you cannot upset the model very much. The other runs a lot of cyclic and just flies the snot out of it.
Personally, I find I like to run fairly low cyclic rates as the model gets small smooth corrections, BUT you have to be VERY in tune with the model since , if you get behind in your control inputs, you have very little cyclic power to bring it back. I found that, initially, I needed a little more cyclic than say Wayne or Cliff as they were staying ahead of the model and anticipating what it was going to need whereas I was strictly reacting to what it did. As I spent hours practicing, I began to notice the model doing the same thing at the same place every time and I could anticipate a little better so I could turn the cyclic rates down and still have full control. remember, in order to overcontrol, you must first HAVE control.
Currently, in hover, I am running about 2 1/2 degrees of cyclic in both pitch and roll with about 30% expo. Something I do differently than some of the other guys, I DO run dual rates. Mine are ON low rate all the time EXCEPT when the wind is blowing hard. I turn it off then and get about a 10% increase in control. Wayne doesn't need that since he is so good at anticpating what the model is going to do but, even though I am better than I used to be, I can still get behind in the wind.
In idle ups, I run about +/- 5 degrees of cyclic. You can run +/- 6 as the model will do that without binding but I find that as I increase cyclic rates, the model starts to do stupid stuff like yaw when you give a hard roll or pitch command. If I keep the rates lower, I have much less of that to deal with.
NOTE: This is what I do and I do NOT recommend this for anyone else. I run 4 idle ups. In Idle 1 I do the two rolls and roll reversal. My roll rate is adjusted for two rolls in about 6 seconds, fairly slow, pitch rate is VERY soft since I don't want to wiggle the elevator in the middle of the maneuver and rudder is very low also. Rates are so low in this condition, it's hard to actually fly around as there is not a lot of control here.
Idle 2 is for two loops, I have very low roll and rudder rates and moderate elevator cyclic as that is where I am working the hardest, to make it smooth and round. Idle 3 is where I do all of my flying around and all the rest of my manuevers except for three. It has a moderately high roll rate, moderate elevator rate and enough rudder rate to do a clean 540 stall turn. I am in this condition about 75-80% of the time. I run Idle 4 to do the push over, cobra roll, and pullup with inverted pirouette. This condition has a LOT of elevator with a lot of expo, less rudder for a slow 4 second pirouette, and less negative pitch as I want to get near bottom stick so I do not climb like a bandit in the inverted pirouette, which is my normal tendency.
I also run a CRUISE condition, to set up for my autos. Model is trimmed for level flight with moderate cyclic but only 1700 rpm so when I go negative on the auto entry, the motor doesn't try to overrev so hard. It makes the entry a lot smoother. I think I'm about the only one that does that as I've never heard of anyone else doing it but it makes the autos easier for me so I use it.
In throttle hold I run moderate cyclics with a moderate rudder. I find, if I have too much rudder available, I tend to suck all the power out of the head with it and can run out of head speed. With a lower rudder rate, I can still do what I need and have a lot more rotor inertia left at the bottom to land the model.
NOTE: Everyone does this a little differently and this is what I do. I do not recommend this as the ultimate setup and post it only for information and discussion. I know Wayne and Cliff both do this considerably differently from me. Obviously their way WORKS, since they have both been on the world team multiple times and the best I could ever do was second alternate, but I now fly better using this than any way I have done before.
End III

Gary O
05-25-2006, 09:25 AM
Gordie,

Thanks for all the great information. Like anything else, we just have to do this by trial and error. Very valuable to me. Thanks again.

Alfred
06-07-2006, 04:31 AM
Excellent insight.
I am amazed how you can hover it with such low rates.
At the low level of Comp, I tried lower rate for my Expert and it caught me out big time.
On windgusts, it would blow me down wind by a metre before I could stop it.
I am talking about strong windgusts.