buzzard bait

My VK Nieuport is so difficult to take off that I abort several take-offs for every successful one. I've seen the toe-in/toe out debate many times, and anyway I don't want to do that, so I'm thinking about adding a gyro for the rudder for take-off.

I looked at the Balsa Products website and found the GWS gyros, which are not expensive. I would want to be able to turn it off after takeoff. The Piezo PG-03 shows the way it is set up, which looks to me like the only choice would be to leave the gyro on for the whole flight. It seems to me I would need the Piezo PG-02, because it looks like it can be switched during flight using another channel.

Has anyone tried either of these GWS gyros? Am I understanding them correctly? Is there an alternative gyro I should be considering instead?

Thanks in advance.

Jim

TFF

I have heard of people using rudder gyros and liking them.

otrcman

Jim,

In a nutshell, yes, you can do exactly what you describe. And I think you will be very pleased with the improvement in your Nieuport takeoffs and landings.

Some of the inexpensive gyros have quality and reliability issues. I am not knowledgeable about every type, so I can't comment on the PG-02 or PG-03. I have used the Hobby King 401b with good success. It is inexpensive and needs some inspection before putting in service. It also picks up airframe vibrations and causes the servo to "twitter" some. The better gyros today seem to be the "mems" sensor type rather than "piezo". I have one Futaba 401 gyro which seems to work very, very well. It is of the "mems" type.

My preference is to use the inexpensive gyros only on expendable models. On my "real" models (like your Nieuport) I feel safer with something like the Futaba 401 and consider the extra money to be good insurance. Some folks are less conservative than I.

There are a couple of extensive discussion threads that cover your exact question, one here on RCU, and another on RCG. One fellow has put together an excellent tutorial for beginners that covers nearly everything that you will need to know. Check this out: http://www.mycoolrc.com/gyro/indexnew.html

Dick

abufletcher

Maybe a gyro would have saved my Flair Legionnaire which was an absolute terror on take off. As you say, multiple attempts on every take-off to get it running anywhere like straight. In a purist sense, I'm opposed to all technological means of making "hard to fly" models easier, for example, channel mixing...as I think it forces me to be a better pilot. But frankly, the Legionnaire was just a rotten flying model (at least mine was) and could have used all the help possible.

So I say GO FOR IT! [8D]

buzzard bait

Thanks very much Dick.

Jim

Oh, another post while I was typing. Yes, in some cases the problem is just ridiculous and there's no sense in being a purist about it. As you've pointed out before, you can't be in the cockpit like a real pilot, and that makes it impossible to make the corrections soon enough. If I stand directly behind the airplane while it's taking off, I have a chance of succeeding.

abufletcher

With may serious scale WWI models I ALWAYS stand behind them for take-off. No sense adding to the burden if you don't have to. If I had to guess, I'd say that what's really needed is both VERY careful rudder use AND skillfully mixed in elevator...and even some aileron. In other words, you need to be flying the model with all channels from the very beginning.

Looking at the video framegrabs below, I think I had already lost it by the second photo. Notice that there's no right rudder. And combined with perhaps too much elevator, I'd say that I essentially stalled it while still on the ground.

abufletcher

Something to think about here. We normally think of rudder as being used to "turn" the model...as in "the model is heading to the left, I'd better give it some right rudder." But the fact is that many WWI models (just like the originals) are better thought of a 3-channel models...with an occasional "assist" from the 4th aileron channel. In other words you use a combination for rudder and elevator to bank and level the wings. So on take-offs what I really needed to do with my Legionnare (and probably need to do with my SE5a) is use the rudder to keep the wings level so I don't stall out in a ground loop (while isn't really a "loop" at all but a tip stall).

Bozarth

My Feedback: (15)

Why not?

Kurt

Bundubasher

Abu,
Looking at those picture sequence, will it help to line up the model on the runway and very slowly open the throttle a bit, get rolling, open a touch more, let the tail pic up and take off on low power but keep it on the runway longer?

I had a couple of models that were pigs totake off on >75% power.

Just wondering

Cheers

Bundu

abufletcher

Bundu, I tried that but just couldn't keep it going straight most of the time. Once the model was in the air, it was ok, but the less time it spent on the ground the better. And, Jim, I did think about installing a gyro, but honestly I was just too cheap.

Bundubasher

Abu,
Interesting, that plane of your on the pics should track well with the wheels that far forward... but yes..on some of those pics one can see the ailerons is to the right to recover from the left bank - but it seems the plane have stalled already.

I had 2 bipes that had a similar problem - almost a type of wingtip stall as you leave the runway, on one I solved the problem by giving the lower wing1.5 deg wingtip washout, and it made it behave well. If it needs washout, then applying rudder on take off may just makes things worse.

On the other Ibeefed upthe undercarriage and lower it a little as itwas bounching on a grass runway, and then suddenly you have a larger bounch, nose goes up a bit,increasing the wing's angle of attack while still close at stall speed, a wingtip drops, correct with the rudder(just causing drag then)and it is a humble tumble...ailment? - the stand off angle was too high - main gear too high.

On a lighter note, I alsohad a Flair Puppeteer which should beeasy to fly- which it did, then one day I got to the field and this thing just would not track, keep running in circles, closer inspection revealed that the fixed wire tailskid was bent a little sideways.....

I've found that normally (not always), a bad behaving plane usually suffers from a very simple,basicailment, whether itneed that 2 % washout, or a main gear that is a tad too high, fitting a gyro may just add the Band Aid.

Having said that, Nieuports, Sopwith Camels etc in real life were not easy planes to fly......and models of them mostly also.

What is the wing loading of theplane on the pic? just curious.

Cheers

Bundu

buzzard bait

My problem is not tip stalls, it's ground loops. My VK Nieuport weighs 5 lbs 6 oz ready to fly...it's not very heavy. If I can keep it pointed in the right direction long enough it takes off beautifully. The trick is to keep it going straight because if it gets off course corrections are almost impossible. A gyro should make the corrections quicker and prevent things from getting out of hand. Once in the air, it is a delight to fly.

I my first efforts the skid was more of a stump, and it was just impossible. I added on a kind of extended skid that gave it a little more resistance to side forces on the ground. That made it possible to take off, but I still had to abort frequently.

The way a scale model sits on the ground is important to me. The idea of trying to bend in a subtle amount of toe-in (or tow-out, depending on who's arguing which side) that will correct the problem without being apparent in the look of the plane is something I don't want to mess with. There is a guy on RCScalebuilder who did it with his Fokker Dr.I and it was successful. Good for him.

Incidentally, having gear far forward, is NOT good for ground handling. It's better to have it further back, closer to the CG, but then of course, nose overs become a problem.

On my Fokker Dr.I I intend to attach the wheels to the axle so they have to move together. I read somewhere that German pilots sometimes had the wheels welded to the axle to help prevent ground looping. Some modelers have done this successfully. My Nieuport was built by someone else about 40 years ago and it's not worth trying to re-do the landing gear.

I'm also interested in trying this because Sopwith, Thomas Morse, and probably some others used a split axle, so attaching wheels to axle is not an option.

Jim

buzzard bait

One more thing...yes, I was balking at the cost too. Dick, above, likes his Futaba well enough to spend the money, and I don't doubt it's worth it. But I'm thinking I might try a cheap one since I'm just using it during the take-off roll. If anything goes wrong, well, aborting take-offs is what I do anyway! His link suggests another alternative that is even cheaper than the GWS, and apparently better.

Jim

abufletcher

I'm with you on the money, but not on the logic! It's sort of like saying you don't mind buying cheap life-vests, after all you'll only use them if the ship sinks! The question is really whether you think it's worth it for this model.

On the topic of "ground loops" I'm convinced that this isn't just a simple matter of wheels turning on the ground. I believe it is an aerodynamic issue and that because the lift on the wings has become unequal, the pressure on the wheels is unequal.

KFX450

My Feedback: (30)

Several people at my club use the GWS gyro on their jets for take off on the nose wheel..It works great from the feed back I get from them. No need to spend crazy on it..The GWS works fine..IMO

CanDo

I found adding some right thrust to my 1/4 Pup really tamed the "torque effect" at take off; now I just have to deal with the wind! Because I'm flying off of a runway, crosswinds are my nemesis; however my Pup is easy to control without a crosswind. Some planes just don't have a very effective rudder at slow speed (like my GB). Sometimes increasing the rudder throw and adding exponential helps. A friend added a gyro to his 1/4 Cub and it really tamed the ground loop problem. Good luck!

pimmnz

Abu, before spending money on gyros there is a couple of things you can try, first, mount the wheels on a common axle, and ensure that the wheels are locked to the axle, then mount the axle in bushes so that the bungees won't stop the axle turning. This makes it difficult for the model to turn, but as I guess that taxiing isn't part of your repertior so that won't be a problem. The other thing is rudder aileron mix, mix lots of aileron with your rudder, that way if you forget to use rudder, as in your example, the aileron will operate it too, and the model does need co-ordinated R/A anyway. Practise always helps, and a good dab of DOWN elevator just after it starts to move will raise the tail enough to allow the rudder to actually work, full UP of course from stationary...although I think that practise will yeild the best results, throttle should be just a steady increase, it might prove that perhaps no more the 3/4 throttle will also assist to tame the wayward characteristics, which all the WW1 models exhibit to greater or lesser degree.
Evan, WB #12.

abufletcher

This is really Jim (Buzzard Bait's) problem now. My model has long since bit the dust (figuratively and literally). But I'll bear this advice in mind for future models.

foodstick

It would be an interesting test to see of the gyro helps... Does this kit have a scale sized fin rudder? or is it increased for better handling? There is nothing worse than the rudder not working until its in the air.
I had a GP Super Stearman that was a NIGHTMARE on takeoff ... At takeoff it always felt like I was flying on throttle and elevator alone. I had a converted 25 cc engine in it,and while it flew scaleish, it was not that fun .. I had a 46cc poulan chainsaw engine sitting around, so I squeezed it into the Stearman. After that, the bigger prop and motor ...I had so much air across the fin/rudder on takeoff it was like it was on rails. It wasn't even a trick to do nice takeoffs after that...

abufletcher

Funny you should mention the GP Stearman. The editor who came to photograph my SE5a a couple of weeks ago, bought one of these with him and after the shoot he flew it for us. For power he had a Saito 120R radial and take-offs looked like a breeze.

DustBen

My Feedback: (3)

edit

abufletcher

But your thumbs aren't really any smarter.

otrcman

Abu,

Please forgive me for selectively editing your post above, but I wanted to specifically address one of your comments.

My view on using technological means in a model where it would not be necessary in the real airplane may be a bit different than yours, or perhaps it's only more nuanced. I think we agree on the use of a radio receiver and servos in our RC models, simply because we aren't small enough to fit in the planes ourselves. And since our arms aren't there to move the controls with human muscle power, we substitute electrical actuators. I view the gyro in much the same way.

In order to keep a tailwheel model (especially a top-heavy one) going straight on takeoff or landing, we need to sense the motions before they become unrecoverable. The pilot of a full sized tailwheel plane feels side forces associated with what engineers call "angular acceleration". This is the earliest clue to a divergence and enables the pilot to make corrective actions so early that the airplane is well controlled. Even when rudder authority is quite low at the beginning of takeoff there is enough control if you catch the divergence early.

An RC pilot can't "feel" the airplane motions. The best he can do is to "see" the motions as they become larger and larger. That's why you get better results standing behind the model it gives you earlier visual cues. But by the time the divergences are large enough to "see", it's often too late to do anything about them.

So my rationale for using a gyro is the same as for using a servo. It takes the place of something I can't do because I'm not in the airplane.

On a separate subject, I'd like to commend your photographic series of the the unsuccessful takeoff. You caught all the significant events along the way except for the initial divergence. I would suggest that the die was cast by the time the first picture was taken. A ground loop starts so early and so subtly that only an on-board observer (or a gyro) can sense it. In the final stages, it appears that the model did the classic biplane ground loop. As the speed builds up and the turn to the right begins, the top-heavy plane leans left due to centrifugal force. When the left wing tip drags on the ground, a large yawing force in the opposite direction occurs and the airplane reverses turn direction and begins to turn left. At some point the deceleration due to skidding tires and dragging alternate wing tips is so great that the plane goes up on it's nose.

My response to those who think I'm a wimp for using a gyro goes like this: Let's compromise. You can think I'm a wimp. I won't care what you think. Now, we're both happy.

Dick

DustBen

My Feedback: (3)

Nope... thumbs aren't any smarter, but the pilot is for making a good decision installing the gyro.

buzzard bait

Yes, Dick explained the control problems of models vs. full scale very well (but I think Don agrees with that).

Also, I agree that the photo series of the takeoff was terrific. But I think it shows a problem that was different from mine. Mine is all on the ground. If the curve sharpens before lift off, abort it. If it doesn't and you can live with the direction it's going in, lift off is fine. I've never gotten it to go straight. Standing behind the plane helps a lot, but by the time the plane is gaining enough speed for lift off it is too far away for me to see well enough to make quick enough corrections. Then the curve tightens FAST and I just shut down and try again.

Also, on the right thrust, I agree that should help. VK shows right thrust on the plans. But the geometry of my engine installation doesn't allow it.

As to a cheap gyro, my Nieuport has trained me very thoroughly to abort take-offs that aren't going well! Maybe I'm kidding myself here, but I don't see the problem. If the take-off roll isn't going well I'm going to abort whether I have a gyro or not. If it is going well, I'm going to shut the gyro off as soon as the plane is in the air. What could go wrong?

Unfortunately I live in the cold north, so I won't get to test any of these theories till next year. But I might get the gyro and play with it a little.

Thanks for all the interest and ideas, everyone.

Jim