OK Guys

Just bought a used Temptation Pattern plane to start me off in Pattern flying. After going to my clubs Pattern contest I was hooked. Anyway, I will be doing Sportsman and am looking the best throws to start with. I was at central hobbies site looking at the instructional stuff and I don't remember seeing this. I've heard 12-15 deg..I've heard 20 etc etc etc. I know at 100 % I'm not getting that much on say the ailerons...About 15% deflection. Advice is very welcome. This bird is more plane than I'm used to as far as accuracy compared to all those arfs I have

I want to make sure I get it set up as accurately as I can. Not sure the deflection gauges I have (great planes) is up to the task. I was always told to center that servo arm before doing anything...The central hobbies reads are confusing me here with the 90 deg to the arm thing.


So much to learn. Hope to meet most of you next season

Joe

For me it's a feel thing, I tend to fly most of the schedule on low rates so I have enough deflection to get through all the maneuvres but no more than that. Elevators I put in enough to give me a decent corner radius on squares, ailerons are set to give be a good controlled roll rate and rudder is set for enough that I can knife edge and no more.

Then I have a snap condition, lots of aileron and enough elevator to get a good break, and just enough rudder to get a cone shape in the tail.

Finally I have a rolling-stall turn condition which is enough to get me through the rolling loop-circles, and a big flappy rudder to get over the top in a stall turn.

It what works for me, but it may not 'feel' right for you, it's a case of fly it, and see where you end up.

90 deg to the arm may work for 99.99% of the world but it's never worked properly for me.

Get it close by eyeball to start with, then adjust the servo center with the subtrims and pushrod length until you get the same deflection each way with the endpoints set at 100%. Then, there's a really good chance that if you then set your endpoints back to 25% you'll still get equal deflections each way.

The linkage geometry we use to reduce +- 45 degrees of servo movent down to +- 15 degrees of surface deflection actually adds exponential to the surface travel making it more responsive around neutral, the opposite of what we usually want. So adding 10% more endpoint to get the deflection equal (for example left aileron 100%up and 110% down = +- 15 degrees at 100% rates) will, when you use low rates eg 50%, yield something like +9deg, -10deg.

Sounds confusing, but it's all part of the fun of setting up a plane mechanically before you reach for the electronic fixes.

Joe,

Do not just set the plane up by the book and then walk away. Most pattern plane throws are setup for guys flying Masters and FAI. You wont need as much throw when just starting out. Always better to start a little soft and as you advance through the pattern add more as needed. For Sportsman you probably wont use more than 12 degrees or so for ailerons and not much more on the elevator.

Arch

Flying Sportsman -> Intermediate, I've got about 7 degrees on ailerons and elevator. I have full rudder throw but may be too much for everything but snaps.

It's all about feel. If you are not yet using rudder on rolls, then you need to roll fast enough to not lose too much altitude, but slow enough that you can control the plane, maintain constant roll rate, and stop it on point. The most elevator I need is for practicing square loops and the Shark's Tooth angles.

I personally have found the plane to be much more controllable with less throws, and think it looks more graceful with slower rates. Of course, this is all my opinion and you should try things out and do what works the best for you.

Joe,

I think Archie and others mentioned that most of the throw settings you'll read about are for the classes with more difficult maneuvers such as snaps and spins which is true. Most of those planes are set with various dual rate or flight conditions that give the extra throw needed for those maneuvers. However, those same airplanes have rate settings or flight conditions that are used 90% of the time and I'd suggest you start off there for Sportsman. For normal maneuvers such as stalls, rolls, Immelmans, and the other stuff that gets flown in all the classes, I'd recommend 8 degrees elevator with 10% expo, 12 degrees aileron with 10 or 15% expo, and all the rudder you can get which is hopefully around 45 degrees. The expo for rudder is going to depend on whether or not you can actually get 45 degrees of throw and would be somewhere between 60 and 70% expo for 45 degrees of throw. Naturally, if your mechanically limited to less throw than that, you'd reduce your expo accordingly. Some pilots fly with more throw and more expo on aileron and elevator. My experience is that it's hard to consistently hit the same roll rate or radius, in the case of elevator, with a lot of expo. I learned this from one of the top pilots in the country years ago and the lesson has served me well. As you've heard, all of this is a matter of preference, but I'd suggest you start with "normal" flying settings such as the ones I'm suggesting so you don't have to re-learn everything later as you progress into more difficult maneuvers that require more throw. When you get into those, you can use rate switches to increase the throw with increased expo to make it feel similar to your "normal" flying setup.

Verne

Outstanding.....Thanks a million

I personally think that getting the airplane to fly strait is just as important if not moreso then the throws. Make sure both elevator halves are in track with one another. Do the ailerons have equal throw? You would be suprised how many set up equal values on the TX between the Ail and flap channels (JR) and think they are getting the same throw both sides. Do the ailerons travel up just a tad more then they do down ( differential ) is the CG correct? With the CG correct does the airplane pitch to the belly when in knife edge? With propper CG the airplane should fly strait anywhere from 1/4-full throttle if it does but pulls to the belly or canopy on verticals then you need an engine thrust adjustment.


An airplane that is trimmed correctly will need less throw because you are needing less corrections. Take the time to learn to trim the airplane, make one adjustment at a time and do several flights with each adjustment before making more changes. It sounds like a big pain but your scores will reflect your efforts. Usually takes me around 50 flights before I am happy with a new airplane and my setups change with the sequence most cases.

I'm finding that out that the ailerons don't goe the same amount in each direction...One thing that is bothering me is when I think Ihave the control surface centered etc..My Aileron pushrods are not the same length. Could be the way the servos are mounted. I'd like to add a small ply top on the servo mount and remount the servos......Not sure that's a smart move??

Joe

I would think it would be easier to adjust that in the radio. (the travel distance, that is)  Remounting servos seems like a PITA.  recenter servo arms, adjust control rod linkage and length to center the control surfaces seem easier to me.  Perhaps a rod got bent.  Starting from "scratch" by remounting the servo and linkages would be a last resort in my opinion.  But as a disclaimer, this is my first season in this hobby, I could be completely wrong

As far as throws I went 1/2 inch each way on ailerons and elevators, 1 inch each way on rudder.  17% expo on elevator and ailerons and 25%on rudder.  During the sportsman sequence I did not "max out" the surfaces at any time.  Not even during the intermediate sequence either.

I did re-center the servo arm/wheel and adjusted the control rods...That's were they are not the same after adjusting..More threads show on one side than the other. Yes, I know, that is super anal but I want it puuurrrrfect I did notice one servo screw was just catching the edge of the wood block..Not sure I like that.

I'll try to post pics latter if I can find the darn camera

Back in the good old days before fancy radios you needed to adjust the linkage geometry to get equal throws or unequal throws, whatever you needed. The old ships that only used one servo to drive both ailerons via torque rods could very easily be set up to give exact throws and differential without resorting to dual servo's, endpoint settings and differential mixes, so it can be done mechanically correct first.

It's personal preference but I'd much rather spend 4 hours in the workshop getting the mechanical setup right, rather than spend 4 hours at the flying field trying to mix out the strange little things that are happening. With a correct mechanical setup you can get the deflections to match throughout the WHOLE range of travel and not just at the endpoint, very important if you want to mix in flapperons or when using dual elevator servo setups. Endpoints only get the endpoints the same, not everywhere else in between.

However, the final test is the actual measured surface deflection, and as much as I like the shed, there are times when one pushrod can be slightly longer or shorter than the other and I can't figure out why, but I've got happy numbers in the TX and the measured deflections are correct and matching so I just live with it.

The servo that is mounted (Questionable) also has the non 90 deg tangent like shown here on the right

I agree with what bjr_93tz said. Computer radios are fantastic, but if the mechanics are set up right it becomes a matter of fine tuning. Otherwise you are fighting a bad set up. The figure is a geometry study I did for an Ultimate I'm working on. For pattern, the throws would be more limited, probably by moving the link in on the servo arm.

The other figure shows the negative mechanical "exponential" of the servo output. (It's actually a sine function, not exponential, but the effect is "close enough for government work") The first 10-15% expo cancels out the mechanical "expo". I like to use about 30% to make those small corrections around center smoother.

Hope this isn't a stupid question but....

Is it more important to have 90 deg rod to the servo arm...Or is it more important to have the servo arm 90 deg to the servo? I think this is the part thats confusing me. If I set everyting on the TX to zero and set my servo arm 90 deg to the servo, one one servo I can not get the control rod 90 deg to the servo arm. Now If I remove the servo arm and re-place it on the spline where it's no longer 90 deg to the servo, I CAN get the control rod 90 deg to the servo arm.

I bet I'm screwing this up big time?

I can't thank you guys enough for the help

Joe

Joe, if you look at the drawing I put up of the control linkage analysis, and look at the middle section where I show the control surface at neutral, you will notice that I drew in a heavy line showing the control link vector at 90 degree angles to the servo output arm and the line from the control horn connection and hinge. If you do this, there will be almost no differential built into the linkage (due to the unequal lengths of the input link (servo arm) and output link (horn) there will still be a negligible amount).

The actual pushrod in this case has a little bend in it to help clear the slot in the wing, so I did this drawing to get the measurements right since it would be nearly impossible to eyeball it in this situation. CAD skills are not absolutely necessary. You can do it on paper with a pencil, straight edge and compass too.

Back in the day when I was flying slope gliders before computer radios, we used to use mechanical differential in the elevator to produce more down than up. Since the elevator also functions as "throttle" on a glider, at high speed (nose down) you need less sensitive elevator to slow down. Nose high, you will be flying slower and will need more authority in the elevator to put the nose down. I have yet to experiment with differential on my pattern plane. I am still learning trimming and may use aileron differential. I will have to get my scores to a point where I really notice any yaw coupling first. I am also wondering if there is any reason to put differential in the elevator in a pattern plane.

Ther servo arm being 90 degrees to the servo is arbitrary with respect to surface throws. You can treat the servo as if it were just a point that the servo horn pivots around. It is more important to have the linkage/rod 90 degrees to the servo horn, tangent to the circular path that it travels.
This is good.

Aghhhhhhhh I'm getting it now. I thought the servo arm had to be 90 deg to the servo...Not so! and if it's not you make up the difference in differential or throw percentages.

Not sure where my response went, so I'll try again...

The relation of the servo arm to the servo body is completely arbitrary with respect to the surface throws.

The only reason the servo gets mounted parallel to the control rod (and thus perpendicular/90 degrees to the servo arm) is for, well basically structural purposes. With the servo mounted 'longways' it distributes forces over larger area of the wing structure, and will be less prone to deflection. This has absolutely nothing to do with surface throws, but ultimately will result in the best strength and response.

If you are running dual servos (aileron or elevator, etc), you are primarily concerned with the positioning of the servo screw, which holds the servo arm onto the servo. That screw, the pivot point, should be equal distance from the aileron/elevator control horn, and from the centerline of the fuse, for equal travel, response, differential, etc.

So, don't worry too much about the servo body being parallel or perpendicular to anything at this point. Make sure the angle between the control rod and servo horn is the same on both servos, and as close to 90 degrees as you can to start. You may end up changing this angle, but you want to make changes equally on both sides.

You can PM me if you want. I got no sleep last night and this is much easier than designing fuel injectors and analyzing combuster case stresses, lol [:-]

Thanks Joe

I have a good handle on it now

Joe