Super Clown Landing Bounce

Hi Gang,

Well, I finally got the Super Clown finished for Mikey. Stole the 25LA and tank from the ARF Flite Streak. He wasn't happy flying it, said it looked like a toothpaste tube with my tastefully applied green stripe between the red and black. It was getting worn out; last flight he felt vibration through the lines. I'm going to rebuild the front end with the wood dowel brass tubing gear mount fix and through standoffs where the motor mount bolts go. Then dip the whole front end in a vat of epoxy glue.

We were out at the field Sunday and nobody there; all at VSC in Tucson. Tony N. from the hobby shop arrived as we were fueling up and from a hundred feet away he spotted the warps in the wing. He told Mikey not to try any inverted flying. Course if he knew how to fly inverted we would still have the Ringmaster! It's Monokote so I should be able to fix it. Tony liked the polka dots, Mikey didn't, it's a Clown so shouldn't it have an appropriate color scheme?

Plane nose heavy but I thought that would be safer. Forgot about how much more nose heavy it would be with a full tank. Mikey nosed over on takeoff then berated me for balance problem. I told him nose heavy planes fly poorly; tail heavy planes fly only once. He said cut the humor and fix the plane. Ah, the joys of having a teenager.

After adding tail weight, the Super Clown flew OK except for a bounce on landing. Mikey came in nice and steady I don't know what the problem is. Gear too stiff or not stiff enough? Wrong wheels? I'm thinking of trying some of those Dave Brown "Lite Flite" or whatever they are called types.

Any ideas from the gang?

John and Mikey in the PRC

This is also a problem with my Zilch X, and I am convinced the primary culprit is not just way-forward position of gear but sproingy landing gear, in this case 1/8" wire, erroneously referred to as "piano wire."

I continue to get advice which says soft wheels are a partial answer, but I'm currently thinking harder wheels are better.

As model lands, raise your arm. This should result in right wheel touching first, left to follow. Old trick from Quickee 500 racing, even though raising one's arm is not part of that particular technique. Usually works to a certain degree.

In your case, add to the "clown" theme by using mis-matched wheels, big 'un on the right.

Dan is correct: that is usually a sign that the gear (whatever it's nature) is way too springy. A stiff gear usually doesn't cause this although it transmits more shock to the airframe on a rough set down. Them big soft sponge wheels will help tho!

Jake

>Dan is correct: that is usually a sign that the gear
>(whatever it's nature) is way too springy. A stiff gear
>usually doesn't cause this although it transmits more shock
>to the airframe on a rough set down. Them big soft sponge
>wheels will help tho!
>
>Jake

Searching desperately for a source of disagreement with Jake (I most definitely do not like the trend of late), I'm not so sure about the soft tires being a help. Don't they just get squished and then push back?

We are currently using Arlington, Washington, flying site. All grass and small clumps of weeds, although underlying dirt is *very* flat, both weeds and grass real short this time of year.

Both of my ARF Flite Streaks have a single and rigid landing gear strut whittled from hard 1/16" sheet aluminum. Stock location of wheel in relation to leading edge of wing, which means it is a little rearward for a sport model flown from grass. Relatively small wheels (narrowed 1/12 scale electric RC car front wheels) with sponge tires, not firm but certainly not very soft, especially as the tire is only 1/4" or so thick. Nothing like the Dave Brown wheels for example where there is more tire than wheel.

Both of these models can easily be greased in, even with some speed on, and they rarely bounce. It's weird, because just looking at the model, landing gear and tire/wheel combination it looks nearly unworkable on anything other than asphalt.

LAST EDITED ON Mar-24-04 AT 05:14 PM (CDT)
 
"I'm not so sure about the soft tires being a help. Don't they just get squished and then push back?"

Yes, you are correct. I just meant that as a placebo to someone who might be concerned about landing shock going through the structure.
The gear is 95% of it I think. I used a real stiff gear (monowheel) on my Flight Streaks- Veco 1-7/8" streamline wheel and those are about as soft as a brick. No bouncie or shimmy- it just went right on and off the ground real smooth and I am no hot rock C/L jockie.
I remember the USN specifically demanded large diameter wheels with high pressure tires on the production Curtiss F-11C1 "Goshawks" (later BF2C-1s) after testing the prototype with the smaller wheels and low pressure tires used later on the export "Hawk IIs" sent to China and Turkey.

Jake

John and Mikey,

Now wait a minute. Were you at the Basin or the Narrows? Smoothie Bill and I were BOTH flying Sunday morning at the basin. Had the place to ourselves. In fact, I was practicing inverted LANDINGS with my SuperClown. And it was the first "no bounce" landing to date. (Set the needle too rich and ran way short on fuel when doing inverted laps. Would you believe 2 minutes less than the previous tank? Bummer!) I assume that if you're flying the S-Clown, it means the screamin' RingMaster is a doner?

I changed wheels on my stock, flapped, Brodak SuperClown with no effect on the bounce. Soft and spongy doesn't make any significant difference. (They are lighter. They moved the CG the right way. And they wear out fast.) We probably even heard the same expert suggest it! I'm sittin' here asking, "Where's this guy's S-Clown?" No real harm since I can reuse the wheels on something else....

One thing to check is whether your gear has tow-out. If the wheels are towed out, when they hit, it will tend to deflect the gear more, and cause it to bounce even higher. Take the collars and wheels off and lay a machinist's rule against the axles to check. Mine have no tow at all and it still bounces. I haven't tried any tow-in, because I'm guessing it wouldn't help enough to be worth the trouble. Think about this effect and then re-read the comment about raising the handle at touchdown to try to hit the outside wheel first. I do need to reduce the camber in the wheels so they wear more evenly. More tweaking....

I added a 3/4" tailwheel on an adjustable strut. (This doesn't mean I lied when I said my plane was stock, I just neglected to stick to the truth!) It allows the plane to sit with a much smaller angle of attack. That helped reduce the amplitude of the bounces but definitely didn't make 'em go away. I haven't adjusted it out yet to see how much more improvement is available.

I agree with the other comments that a portion of the problem is the energy return from the gear. Attempting a slow, full stall landing always results in a "threefer." I get three landings fer the price of one. The plane plops down at the last second, deflecting the gear, and it bounces back up. At this speed the elevator is no longer effective and the pilot is just along for the ride. I think the fundamental problem is that the stabilizer becomes ineffective before the wing quits flying. An interesting test would be to mount a single aluminum gear leg with the wheel in exactly the same fore/aft position and see if you can do a full stall landing. If it doesn't go away, it isn't the springy gear but may well be the mismatched aerodynamics. Any volunteers?

I think a way to mitigate the problem without corrupting the old-timey feel would be to add stiffness or damping to the existing wire gear. If I ever get around to it, I'm going to add leg fairings to do this.

My gear is in the stock location, and my CG is pretty far forward due to an O.S. .25BB engine. But I think if I stiffen the tail strut, it may reduce the angle it is bouncing at following a three point landing. The harder you hit, the smaller the angle of attack? I've tried the wheel landing approach (touch down level while you still have plenty of speed and elevator authority) with almost equally limited success. Depending on how fast you touch down, it will contact smoothly and roll quite a ways and then the tail starts to drop and it's off to pogo-land. I don't have the hang of adding down elevator at just the right point. Maybe the pro's can do it. Anyone who can land a stock S-Clown with no bouncing deserves double the landing points of any classic or modern ship!

Dave
LA_Flyer
"Pukey Profile Pilot"
from somewhere near Manhattan Beach

>
>One thing to check is whether your gear has tow-out. If the
>wheels are towed out, when they hit, it will tend to deflect
>the gear more, and cause it to bounce even higher. Take the
>collars and wheels off and lay a machinist's rule against
>the axles to check. Mine have no tow at all and it still
>bounces. I haven't tried any tow-in, because I'm guessing it
>wouldn't help enough to be worth the trouble. Think about
>this effect and then re-read the comment about raising the
>handle at touchdown to try to hit the outside wheel first. I
>do need to reduce the camber in the wheels so they wear more
>evenly. More tweaking....
>
>I added a 3/4" tailwheel on an adjustable strut. (This
>doesn't mean I lied when I said my plane was stock, I just
>neglected to stick to the truth!) It allows the plane to sit
>with a much smaller angle of attack. That helped reduce the
>amplitude of the bounces but definitely didn't make 'em go
>away. I haven't adjusted it out yet to see how much more
>improvement is available.
>
>I agree with the other comments that a portion of the
>problem is the energy return from the gear. Attempting a
>slow, full stall landing always results in a "threefer." I
>get three landings fer the price of one. The plane plops
>down at the last second, deflecting the gear, and it bounces
>back up. At this speed the elevator is no longer effective
>and the pilot is just along for the ride. I think the
>fundamental problem is that the stabilizer becomes
>ineffective before the wing quits flying. An interesting
>test would be to mount a single aluminum gear leg with the
>wheel in exactly the same fore/aft position and see if you
>can do a full stall landing. If it doesn't go away, it isn't
>the springy gear but may well be the mismatched
>aerodynamics. Any volunteers?
>
>I think a way to mitigate the problem without corrupting the
>old-timey feel would be to add stiffness or damping to the
>existing wire gear. If I ever get around to it, I'm going to
>add leg fairings to do this.
>
>My gear is in the stock location, and my CG is pretty far
>forward due to an O.S. .25BB engine. But I think if I
>stiffen the tail strut, it may reduce the angle it is
>bouncing at following a three point landing. The harder you
>hit, the smaller the angle of attack? I've tried the wheel
>landing approach (touch down level while you still have
>plenty of speed and elevator authority) with almost equally
>limited success. Depending on how fast you touch down, it
>will contact smoothly and roll quite a ways and then the
>tail starts to drop and it's off to pogo-land. I don't have
>the hang of adding down elevator at just the right point.
>Maybe the pro's can do it. Anyone who can land a stock
>S-Clown with no bouncing deserves double the landing points
>of any classic or modern ship!
>
>Dave
>LA_Flyer
>"Pukey Profile Pilot"
>from somewhere near Manhattan Beach

Ron B.
F4Fguy

The problem is attempting full stall landings.Wheel landings will work you just have to learn to hold the tail off after touchdown.This will automatically crank in full down as the plane slows after touchdown.The basic problem IS gear location.As the wheels touch down,the inertia,acting on the CG, cranks in a whole bunch of incidence,and the wing starts flying again.A longer tailwheel strut will help,but the real answer is to move the mains back.I find that anything greater than a 15-20 degree angle from the CG through the wheel centerline will produce the phenomenon.This problem is common in OT sport planes,as preserving the prop was considered more important than pretty landings.Of course if you plan to fly it in OT competition,you'll lose fidelity points if you do this.

Incidentally,positive camber has the same effect as adding toe-in.Both camber and toe-in will produce a similar effect to the"one wheel"approach.They make the plane want to go in a straight line.Note the extreme amounts of both in old timey full scale taildraggers.Toe-in or camber also produce a lot of mechanical drag due to their "braking" effect.Since this takes place at the wheel,it's applied well below the CG,inducing a nose-down tendency,and reducing the tendency to bounce.
Ron B.

>This is also a problem with my Zilch X, and I am convinced the primary culprit is not
>just way-forward position of gear but sproingy landing gear, in this case 1/8" wire,
>erroneously referred to as "piano wire."
>
An easy fix is a cross-strut (1/16" wire is adequate) connecting the two legs, about 1/3 to 1/2 of the leg's length from the fuselage. The farther down, the stiffer it will be. If the Super Clown is comparatively light in weight, which would be 25 Oz or less, the 1/3 distance would be about right. The average profile this size tends to run about 28-30 Oz; for those, the cross-strut belongs at the halfway mark.

The S-1 Ringmaster's gear was bent from a lighter wire than 1/8" and needed the soldered ends of the stuts to reinforce a longer length of the skinny wire, if you didn't discard the original in favor of using a spare wire gear from a Goldberg profile, after those became available.

I've never noticed any particular benefit from "soft" tires with regard to bounced landings.

.

Kiwi

Kiwi,

Agreed as to a fix for this problem. In fact, I have come up with one which will give similar results, but is a whole lot sneakier. To the point where I am hesitant to add it, have not even tested it yet. But will soon...

If I wimp out on being sneaky, is there a precedent for adding tensioning wire between gear legs? As in, OTS-legal precedent.

I have a vague recollection of seeing a sort of offset "X" of light wire in the style of a J-3's bungee cord gear "springs", from high on one leg to midway down the other leg. But more common (I think, and it's so long ago and I was still pretty young and unobservant when the bigger old birds showed up), I recall an inverted V-brace more often than any other reinforcement.

Where my brace would go straight across between the gear legs of my own profiles from the late 50's onward, the old birds with a similar need to stiffen the gear got a bent medium-deep V shape in the middle and used a stiffer wire than my own 1/16" strut.

.

Kiwi

I don't think there is anything in OTS "rules" that say anything about you can't "beef-up" or wire brace the gear- I suspect a lot of guys probably did this "back then".
I have "sneeky stuff" I use too, but a lot of it is a major PITB and most normal people wouldn't want to bother with the hassle.

Jake

On Dan's Zilch, the particular rule that does apply is that the forward position of the wheels can't be changed. When it comes to landings, the OTS birds with dural gear lead the pack (Barnstormer for one). Not a lot of bounce in that kind of gear.

.

Kiwi

Yeah, but the Barnstormer DIDN'T have dural gear. They gave you neat soft aluminum "fairings" to fold and cement around the piano wire gear legs that went with the spirt of the "stitched" acetate sheet canopy.

Jake

The original kit plans for the Barnstormer show the main wire gear wrapped at the fuselage with coppeer wire. I did this to mine back in 1953, for all the good it did. A wing over into the ground really doesn't prove the gear won't cause a bounce. Ha.

Jake, Dan, I flew these planes back when they were new. A lot of us in OK, TX, KS put cross braces between the gears back then. I think this would be legal today as long as you don't change the angle of the gear or its location. My Clown has single wire cross brace about 1/3 down from the fuselage. Takes a smooth touch to not bounce but is a lot easier with this set up. BTW: The Clown is a great flying little plane. Mine has a (what else) Fox .35

Hi

The clown has a very low AR wing which requires more flare to wash off airspeed before touchdown. You need to get the speed too low to sustain flight otherwise any bounce increases wing angle of attack and you take off again. You probably know that I suspect. However look at the mechanics of the bounce causing a nose up attitude.

Tricarts do the reverse, nose down at touchdown. Not likely to bounce with a tricart or is that not allowed?

If you are trying to land a spot from too much height, it is a mistake to loose altitude because the airspeed increases and ground effects reduce induced dragg. This leads to overshoot or forced high speed landing. It is better to ease a little up while you have altitude (no ground effect). Once the plane slows and wants to drop the nose, a little further up will ballance it's pitch. At this higher angle of attack, the induced drag goes through the roof and you get a steeper glide path at low speed. This shortens your landing. It take some fine control to master without stall.

To extend landing, loose height to gain airspeed that you convert to greater distance in the low drag ground effect.

But the main thing is to wash off all speed before touchdown.

OK, I know some are going to strongly disagree, all I am saying is try it.

I never do that. I just head for the deck and plant it just as soon as I can after the motor quits. Old habit from Rat Racer flying I guess.
The speed bleeds off on the ground with the wheels rolling a lot faster than it does in the air.

Jake

Hi Jake,
I know what you mean. Before reading this thread I don't think I had even thought about *how* to land the plane. Now I believe that my landing scores will plummet this year because I will be so concerned about *how* to land! Kinda like asking a golfer if he inhales or exhales when putting just before he is about to stroke the ball.
Bill <><

Granted, flying technique is a big factor, and my Zilch X does indeed have gear exiting fuselage directly below firewall (to which gear is attached) and wheels are in proper location, which means they are way too far forward.

At either the Stuntaton or Roundup last year I pulled off a very low speed landing which actually looked like it was going to work. However, I was an inch or two high when the model simply quit flying, and it didn't land so much as it just arrived. We were pretty much able to replicate that landing in the pits by just dropping it on the ground from six inches high.

Sounded horrible as well, incidentally.

Both Don McClave and I have tried the smoke-it-in technique and this holds some promise, although it is far from a sure thing.

What about wire (or cable) bracing running from juncture of left gear leg and fuselage over to right gear leg, maybe to a wheel collar? And opposite for the other side. Or is this what someone has already proposed with "X" bracing?

This is actually quite funny, because at one level I honestly don't care, fly OTS for grins. But the angst of level flight, waiting for the landing is getting annoying. And then to (twice last year) look at the scoreboard and see where my second place was just a merely decent one-bounce landing away from first place...well, that too is annoying.

Dan, hey grins are what it is all about. Yeah, I think that is what was referred to in the "X-brace" bit. You could also try just a thin tensioner wire straight across and low down near the axles, but I don't know how much of a problem that might give you if you are operating off a grass field some of the time.

Jake

Ballance your Super Clown exactly where the plans say. I had to cut an inch off the nose, set the engine back and still had to fill the rear full of lead shot. with the stock LA 25 it was still nose heavy and bounced on landing. I then installed an Art Adimisin tongue muffler, an FP needle valve and replaced the 3oz. Acme tanke with a 3 oz. GRW uniflow open to atmosphere. This took some more weight off the nose as well as the whole plane and I get clean runs to the last drop of fuel. WOW does it fly good now. When the engine dies, it glides absolutely straight and lands great every time. Hope this helps.

Steve Hulse

Hi again,

After distilling the info offered here and looking at profile views of profiles in recent issues of "Flying Models”, I came up with the following fixes:
1) Moved gear to vertical instead of angling forward.
2) Reinforced wire gear hole in fuselage with 1/8 I.D. brass tubing.
3) Shortened legs by 1 1/2 inches.
4) Removed warps from wing with heat gun (nothing to do with landing problems but you never know.)

Results: no bounce on landing! Dave had another Super Clown at the Basin today, Sunday. It had flaps but no spots. Flew about the same as Mikey's to my untrained eyes but bounced on landing. Gear was angled forward. Dave said we needed more spots on the plane, a bunch of little ones near leading edge specifically. Mikey hates the spots so of course more will be installed. He's lucky I didn't use that funky clown decal from the kit.

Specs: 29.4 ounces. Monokote Yellow wing and tail with spots, light purple fuse some kind of other than Monokote. OS LA25 blue motor with front needle valve, metal backplate, stock muffler with exhaust opened up. 9-6 Taipan prop. CG approx. 1 1/2 inches from L.E. Homemade 3-ounce metal uniflow tank like on RSM Ringmaster plans. Muffler pressure or not doesn't matter. RPM approx. 10.4K on Performance Plus 10 percent nitro with added Sig Castor to bring oil to 25 percent. Unloads in air to slightly rich 2 cycle.

Dave's Super Clown looked good doing the pattern. We haven’t tried inverted yet. I think we are enjoying the novelty of not having to do repairs or build a new airplane after flying sessions. Think I'll put a beater motor in the Flite Streak for inverted practice and save the new plane. Got a few other planes people gave Mikey but they are either dogs or too nice to use till he gets more practice.

Thanks guys for the help.

Bouncing on landing is usually due to the wheels being too far forward. Unfortunately, with a lot of OTS designs, the gear is mounted on the firewall and you are just SOL to get rid of the problem. The reason is the when the plane touches down, the farther the CG is behind the wheels, the more the plane wants to drop the tail. As the tail goes down, the Angle of Attack (AoA) increases which increases lift and the plane actually flies back into the air. You perceive it as a bounce, but it really isn't. The second or third trip back up may be.
Fixes to the landing gear by stiffening will only make the matter worse. Moving the wheels back, where legal, is the only solution to your landing gear and bouncing woes, as it decreases the moment arm between the wheels and CG, offering less leverage to cause the tail to drop. With the gear mounted back at the wing, adjust the angle to keep the wheels just in front of the leading edge and landings will improve markedly.
Or improve your landing technique. With a forward mounted gear, in particular, you should try to to perfect wheel landings. Just as the model is ready to touch down in a near level position (so not flare), a touch of down elevator will hold the tail up in the level position and keep the plane on the ground. Or to do the classic three pointer, make sure that when you flare, the tailwheel hits first. This is why extended tailwheels have become so prevalent, but not always legal in the OTS world.
There is a reason that a lot of guys have gone to tricycle gear. When the mains hit the ground, the nose comes down because the CG is ahead of the wheels, decreasing the AoA and planting the plane on the ground. Taildraggers are tricky in the model and full scale versions.

Bare

Barry Baxter

Hi Bary

I absolutely agree with the principles you mention. You must have good fields or hard surfaces for rearward wheel positions though. Many fields I fly on are a case of, you take what you can get so I always use very forward wheels to prevent noseing over in the rough.
Certainly any down elev on touchdown is usually out of the question where I fly, all I can do is wash off all flying speed.

John and Mikey,

Good to see you guys at the Basin on Sunday. Too bad Smoothie Bill thought it was going to be too windy and left his machine at home. (I don't get it. Why drive to the field without an airplane...?) And how about the dust devil that nearly went thru the circle when Mustang Bill was only halfway thru a tank! Havin' fun now!!!

Your mods definitely changed the landing characteristics of the S-Clown. While I was still "bouncing it in" (thanks for pointing out my lack of skills to all of modeldom! I forgot about the down elevator again), Mikey was working on his grease jobs. Kind of ironic that the original placement (according to our historians and experts here at SSW) was to protect the prop on landing. I'm guessing that your Taipan 9-6 now measures 8.9-6 from the takeoff buzz job! Mebbe a little too aggressive when ya shortened the gear?

I liked the color scheme on your Clown just fine. I suggested adding the little bubbles on the leading edge only to lighten up the nose a little (offset the heavy muffler) and maybe provide a "champagne atmosphere." Remember, the pattern p'fessionals say presentation really counts! Besides, the bubbles might provide visible evidence of a detached boundary layer....the real cause of the alleged bouncing, all objective evidence to the contrary!

Did you check out the Fourmost ads for a glue-on fillet, yet? I think they have two or three sizes. I'm curious how it works. Might want to try it on the long awaited igNoblarf.

Either you are gracious beyond all reckoning, or weren't really watching, as you described my flying as "doing the pattern." I think I am up to the overhead eights now. (That's where the engine and the line tension have forsaken me in the past....) Either way, your enthusiam is forgiven. Anyone who builds happy looking airplanes is all right by me!

More Clowning Around is scheduled for Sunday. Now if I can scrounge up an O.S. standard needle valve, I should be able to work on maneuvers rather than engine runs and (unplanned) landings. See you guys soon!

Dave
LA_Flyer
"Pukey Profile Dude"
from somewhere near Manhattan Beach