Charlie P.

I prefer to think of them as "Learned Techniques, Mechanical Adjustments and Corrective Accelerometers". ;-)

I was flying my 85" Carbon Z Cub at a float fly and was hit by a gust as I cleared the tree-line on the opposite side of the lake. The sun was such that as I was watching the model I saw one aileron raise just as I was adding rudder to wing-over back towards me. I had a mild panic as I thought I had experienced my first glitch . . . and later remembered this model has AS3X and will try and self-correct. It just decided the correction was different than my intentions. Normally I forget it's even on.

jester_s1

I'm a fan of the purist approach too , Scale, but there is also something to be said for making things easy so the casual or beginner pilot can get into the air. As long as the result is FUN, I'm all for it.

scale only 4 me

My Feedback: (158)

If you're not ready to fly Plane X, you're not ready to fly Plane X. I wouldn't be as good a pilot as I am if I took short cuts. I never want a plane that flies like a video game. To each their own.

Gray Beard

My Feedback: (-1)

No, but mods often help a plane behave better. I had a friend that built a very nice Fleet and I flew it at shows for him. He installed a gyro on the rudder to help him keep it straight. It worked and was on a switch but if you forgot to flip the switch after take off it fought you during flight.
I once had a take off mode set up in a Bipe I had built, it was just some right rudder added for take off but like the gyro, if I forgot to flip the switch it was out of trim in flight. I soon removed the feature after I got used to the way the plane handled on the ground. It just takes some time. The fellow I gave that plane to had a heck of a time with it on take off but we were on a lake bed so he just let it go where it wanted to. He ended up crashing it a few weeks later so it didn't mater.

Charlie P.

What are considered "cheats?" Exponential? Mixing elevator to flaps? Electronic trims instead of manual linkage adjustment? Model memories?

otrcman

What are considered "cheats?" Exponential? Mixing elevator to flaps? Electronic trims instead of manual linkage adjustment? Model memories?[/QUOTE]



Well said, Charlie.

How about centering springs on your transmitter sticks ? Real Cubs, T-crafts, etc. don't have any centering springs on the controls.

How about aileron and rudder trim ? Few light planes have anything other than elevator trim, and some don't even have that.

Do you have a bobweight in the longitudinal control system of your scale Spitfire or P-51 ? The real ones have it.

How about rigid control surfaces ? On a model, the rudder, elevators & ailerons are held rigidly in place by servos. On a Cub or similar airplane you can grab the surfaces in your hand and move them freely. Does that make a difference on a model ? You better believe it. Making the control surfaces rigid produces an enormous increase in stability. That's why flight test engineers always check stick-fixed and stick-free stability. If you're a purist, you should allow the control surfaces to flop freely, perhaps moving only servo tabs with the radio.

On the other end of the spectrum, how about flying a model of a modern military or commercial jet without gyros ? I think you'd be hard pressed to find a modern jet airplane (full sized) that doesn't have at least a yaw damper. So, if you are flying your super-scale SR-71 without 3-axis rate damping, are you really a purist or are you flying a less than authentic scale model ?

Let's face it. What we call scale models may look like big airplanes in outward shape and color, but they have very little resemblance to their full sized counterpart when it comes to flying characteristics. It can't be helped; when an airplane is scaled down to model size the inescapable changes in mass and inertia cause the model's motions to be far different than the motions of the real airplane. Now, if you really do want your Piper Cub to move more realistically in the sky and feel more realistic to the pilot, a 3-axis rate gyro goes a long way to adding "apparent mass" in the rotational axes.

From a full scale pilot perspective, I get about as much enjoyment out of watching a model warbird fly as I do watching a buffalo chip throwing contest.

Dick

scale only 4 me

My Feedback: (158)

What a bunch of nonsense.

sensei

Bob

acdii

Well For those calling me a troll, go fly a fish, I'm an Ogre and don't you forget it!

I tried adjusting the landing gear, it has some play on the Fuse, and thats not it. It pulled right, but as soon as the tail came up, it did its left-right-left dance. The gear tracking right made it even worse, so I set it back to where it was, which was tracking straight to begin with. If I try to take off by keeping the tail down with elevator it will leave the ground before its ready, then will cartwheel. I had a couple others at the field try it, and they fly 3D planes with gusto, and they could not keep it straight either.

This one is way too easy to chase its tail, so the only time I can take off nice and straight is with a cross wind from the left! LOL Once in the air though, great flying plane, easy to control in all aspects, even upside down, and landings are always smooth and non eventful, though my last two were dead sticks. I have to pull the engine and check the carb for dirt. It doesnt seem to be running right, feels a bit fuel starved.

BTW I maidened my 1/5th Cub last Friday, and had an amazing experience, too small a prop, combined with too big an engine on an untrimmed plane resulted in a vertical takeoff after a 10 foot roll. Had it trimmed after a couple minutes to get it level, then landed. Got it back home, made some adjustments to the links, and flew it again on Wednesday. It flies BEAUTIFULLY! No tail chasing, straight down the runway, little up elevator to keep the nose from pitching over due to the down trim needed, and it lifted off like the real thing.

And for those who think I dont know how to fly, póg mo thóin. I'm a good pilot, fly about a dozen different planes including warbirds, none of which have expo or rates, all have full throws, and this is the only plane I have that is quirky on takeoff. It will track straight, then as soon as the tail lifts, goes left, and even the smallest right rudder, it veers right, ease off and its back to the left. Even with a lot of expo dialed in, it still does it, so going to put a 3axis in it once I figure out where to put it.

Charlie P.

Expo and AS3X won't help for the transition from wheels to wings. If the model veers when the tail-wheel lifts it is likely because the tail wheel and the rudder are not "running" in the same direction. The roll test along the ground with a centered rudder will show this.

Many models need right rudder to run straight on take-off. Just a part of life and flying.

Adding a few degrees or toe in to both main wheels makes a model tend to self-correct for straight rolling.

Jennifer Curtis

When you adjusted it, did you bend it to point straight down, instead of angled back?

Jenny

jester_s1

I'm still betting your main gear is crooked, which means your tail wheel is also crooked to compensate. It doesn't take much on a Cub to cause the waggle dance you are describing. Some precise measurements will usually tell how good it is, or you can look at the relationship of the tailwheel to the rudder. If the tailwheel is at a different angle than the rudder in order to make the plane track straight, you will never get a good takeoff.

flycatch

My Feedback: (26)

Did some more research on your problem and found nothing. From what you said in this post it tracks straight with a cross wind coming from the left. This may be the clue to the problem. Check your wing and tail incidence angles for misalignment. QUOTE=acdii;12046993]Well For those calling me a troll, go fly a fish, I'm an Ogre and don't you forget it!

I tried adjusting the landing gear, it has some play on the Fuse, and thats not it. It pulled right, but as soon as the tail came up, it did its left-right-left dance. The gear tracking right made it even worse, so I set it back to where it was, which was tracking straight to begin with. If I try to take off by keeping the tail down with elevator it will leave the ground before its ready, then will cartwheel. I had a couple others at the field try it, and they fly 3D planes with gusto, and they could not keep it straight either.

This one is way too easy to chase its tail, so the only time I can take off nice and straight is with a cross wind from the left! LOL Once in the air though, great flying plane, easy to control in all aspects, even upside down, and landings are always smooth and non eventful, though my last two were dead sticks. I have to pull the engine and check the carb for dirt. It doesnt seem to be running right, feels a bit fuel starved.

BTW I maidened my 1/5th Cub last Friday, and had an amazing experience, too small a prop, combined with too big an engine on an untrimmed plane resulted in a vertical takeoff after a 10 foot roll. Had it trimmed after a couple minutes to get it level, then landed. Got it back home, made some adjustments to the links, and flew it again on Wednesday. It flies BEAUTIFULLY! No tail chasing, straight down the runway, little up elevator to keep the nose from pitching over due to the down trim needed, and it lifted off like the real thing.

And for those who think I dont know how to fly, póg mo thóin. I'm a good pilot, fly about a dozen different planes including warbirds, none of which have expo or rates, all have full throws, and this is the only plane I have that is quirky on takeoff. It will track straight, then as soon as the tail lifts, goes left, and even the smallest right rudder, it veers right, ease off and its back to the left. Even with a lot of expo dialed in, it still does it, so going to put a 3axis in it once I figure out where to put it.[/QUOTE]

speedracerntrixie

My Feedback: (29)

The issue as I see it is that the airplane needs more right thrust, has a very effective rudder with too much throw and a pilot that could use more left hand practice. Get about 3 degrees right thrust into it, reduce the rudder throw to about 15 degrees and ease on the power, taking off at about half throttle and life with this airplane will be much easier.

mike31

My Feedback: (67)

Got toe in?

acdii

Just did a complete PM on it, added some right thrust, and while I had it on the floor happened to look at it from directly behind and think I found the problem. It had a very slight left rudder at neutral. Considering how rudder sensitive this plane is, I can roll the plane with just rudder, that might be all it is. I also found the reason it rolls left on take off, the left aileron is just a hair higher than the right one. At anything above takeoff speed it tracks straight, so not going to touch it just yet, first want to see if a touch right trim on the rudder and added right thrust is enough to get it tracking straight now. The rudder was off by 1 mm, and considering how much I had to drop the elevator on my cub to trim it, 5mm, this might just be the key.

Now hoping the engine stays running more than a few minutes, I replaced the clunk line in the tank, it looks like it stiffened up too much and did not move at all when I move the plane around, Last year it ran really good, but this year it hasn't run for more than a few minutes once airborne.

I picked up a 2D/3D inertial stabilizer last week and mounted it, will give it a whirl to see what it can do. If it helps keep the plane stable, and the rudder tweak fixed my taking off, then I will put it in my P-51, and hope it corrects its nasty snapping tendency. Pretty sure I found the cause, and wont need it in this plane, once it is off the ground it handles like a dream and is a blast to fly. Also a lot of fun to watch it come in sideways in a cross wind for landing.

acerc

Just a note, all aircraft want to roll left on take off, some more than others and speed plays a role as well. As soon as the airframe leaves the ground a smidgeon of right rudder will stop the rotation until the speed catches up enough air for the wings.

speedracerntrixie

My Feedback: (29)

Acdii, your P-51example is pretty much what I am talking about. You state that it is " snappy " and rather then trim that behavior out of it you want to try a gyro/stabalization unit. The fact that you say you dont use dual rates or expo adds to the mix. I fly a warbird race series. My racer is a Macchi 202 that has thin wings, relatively high wing loading and no washout, yet lands as easily as a Super Sportster. The reasons for this is first it was built straight. It has the CG placed as close to nuetral as possible without loosing directional stability and most importantly it does not have too much control throw. The old standby is that nose heavy is more stable. That gets knocked into our heads by our instructors. At least it was with me. The problem is that extra nose weight requires more elevator to compensate and that leads to more angle of attack coupled with with a dynamic increase in wing loading. That downforce the elevator applies incerses the loading. Now I'm not saying that CG will fix tip stalls on every airplane. An example of that is a Spitfire I have. Even after adjusting the CG it would still snap if pulled hard in a turn. Raising both ailerons two clevis turns and pulling a tad more elevator travel out fixed it. You should be able to fly at cruise speed and pull a full elevator loop without any snap. If not its a good indication you are running too much elevator throw. If you dont think you can reduce throw and have enough to land then most likely your CG is too far forward. I have nl doubt you are a good pilot, with some trimming skills you can be even better.

Jennifer Curtis

Be wary of a three axis gyro in a plane that wants to snap.

If one wing stalls and starts to drop, the gyro
will try to lift that wing by lowering the aileron.
This could cause the stall on that wing to deepen,
making recovery difficult.

A stall at low throttle is also more likely, when
the elevator tries to keep the nose up to level
as the plane slows. The elevator goes up, up
up, and then STALL.

If it is only hooked up to the rudder not so much
badness will occur.

Jenny

acdii

The P-51 is most likely a build issue with the elevator. Its a TF ARF, and there is a twist to the elevators. There is very little throw on them as well, and these were high speed stalls that did it. I practiced low speed stalls with it and was able to recover easily, its when going WOT from level flight and pulling up that it snaps over. Not a lot of pull either, say half a stick movement is all it took. Right now the plane is hanging in the rack, maybe someday when I feel like it I will make a new set of elevators and remove that twist. They are dead even at the rudder, but the balance tabs clearly show the twist. Just so happens the twist is in the direction it snaps too.

If the weather holds tomorrow, I will find out if my adjustments corrected the left turn issue. I have a gut feeling that 1 mm is all it takes. The light hit the tail just right for me to see it, otherwise I would not have noticed it. With how sensitive this one is to rudder, hopes are high its resolved.

speedracerntrixie

My Feedback: (29)

Beleive it or not I don't think the twist in elevators would cause a snap. Reason being that we have a a local that races with us who has been experimenting with minimal control surfaces. The has a p-40 that only uses a single aileron and a single elevator half. Watching him fly you would never know. This is an airplane that is perfectly comfortable pulling 30 G turns at 150 mph. When you say very little throw do you have a dimention? For example on my warbird I fly around with 1/4" travel and land on 3/8" travel. That would be my definition of very little. I have seen other guys refer to not much throw as 3/4". My Spitfire did the same thing as your Mustang until I backed off the throw and raised both ailerons a smidgen. Just a couple things to consider along with adding some expo.

acdii

RESOLVED! That little bit of right thrust and tiny bit of right rudder trim was all it took to get it to run straight once the tail lifted, and just a tad bit of right, I mean a hair movement is all it takes to keep it straight. It lifts off level now too, so that 1mm of left rudder was causing the wing to drop at slow speed. Three take offs, one dead stick and missed the runway by 6" and ripped the gear off. GRRRR. All fixed though, just have to recover the belly. I also need to get some more flexible fuel line and heavier clunk, found that it isn't moving in the tank, and going inverted, or a steep bank causes it to suck air, and thats why the engine dies.