Most 'technical' stunt design going?

A whole bunch of technical design information has been compiled about CL stunters. We have large amounts of scientific knowledge, but ignoring that we have examples of superb flying stunters.

So, I want to ask - what do you feel is the most technical stunt design going nowadays (and why)? Or, what features do you think it would have? Or, what do you think is the best stunter design, and why?

After over 50 years of building CL stunters, surely some standard features stick out, plus we see the DIRECTIONS that things seem to be headed. (Powerplants, etc.)

(My personal feeling, based on limited input, is that Walker's Impact is a fabulous modern design.)

Just curious, we have some fantastic technical discussions here, I'm mostly a lurker on them, I'd like to see more. Thanks in advance for your inputs.

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"Nature does nothing uselessly." -Aristotle

Larry...I think that, in spite of the fact that it was flown illegally at our Nationals, Mike Palko's electric stunter demonstrated a quantum leap in utilization of that power source. Our glow stuff is pretty much a permutation, be it 4 stroke or tuna pipe.

See Ya

(My personal feeling, based on limited input, is that Walker's Impact is a fabulous modern design.)

I agree. But Randy Smiths SV11 sorta broke the ice for modern day designs even before the Impact and is still competitive. You think???

LAST EDITED ON Oct-25-04 AT 09:51 PM (CDT)
 
Big Jim's Patternmaster was the first glimpse into modern large stunters with powerful engines. (1971)

Specific changes would be:
1. Bulletproof controls. 1/8" wire horns.
2. Bulletproof nose.
3. fat airfoil (most copied in stunt).
4. "modern" large stunter numbers (tail ratio, moment, etc).

Walker's Impact:
More "slick" design (lower drag).
1. Slow controls (this is very important).
2. Aft CG (goes with the slow controls or vice versa).
3. Larger stab (goes with above-more flying tail).
4. OS 40 VF. (linear engine response using entire range of HP curve).

Fancher's Trivial Pursuit
1. Same as Walker on many pointS.
2. High angle of attack wing (allows minimum over rotation in corner).
3. Low drag (requires minimum output from the engine).

Rabe Semi scales:
1. Invented high lift wing (taught Big Jim).
2. Small wing (minimum required---good in turbulence).
3. High drag-large flaps, high deflection---allows high output engine to be used with control.
4. Rabe rudder.
5. aAdjustable leadouts.

Berringer Sportster:
1. Designed for a 4 stroke.
2. Extreme forward CG.
3. Long tail moment.
4. Counterbalanced elevators.
5. High angle of attack airfoil.

As Brett would say, the rest is "in the noise".

I'd add the Yatsenko designs, especially for the advanced structural concepts - moulded composite shell construction, the engineering excellence of the take-apart fittings and the overall package of airframe and engine.

Must be one of the few designs where the basic engine design is driven by what is required by the airframe, rather than vice-versa.

For whatever reason, it works in a wide range of conditions.

I wasn't think broad enough, to start with!

Definitely, electric stunt! Prove skeptical old bastards like me dead wrong!

And innovative molded composite construction techniques.

I mentioned Walker's Impact, but I haven't seen the Mustang with the big 4-stroke. (I can't imagine Paul ever moving backwards, but the B17, wonderous as it was, simply did not fly as well as the Impact.)

Nowadays I seem to find myself attracted to beautiful styling and paint jobs (who isn't?) but I know these are not the correct parameters to be rating stunt ships on..

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"Love is the triumph of imagination over intelligence." -H.L. Mencken

>I'd add the Yatsenko designs, especially for the advanced
>structural concepts - moulded composite shell construction,
>the engineering excellence of the take-apart fittings and
>the overall package of airframe and engine.

Absolutely.

>>I'd add the Yatsenko designs, especially for the advanced
>>structural concepts - moulded composite shell construction,
>>the engineering excellence of the take-apart fittings and
>>the overall package of airframe and engine.
>
>Absolutely.

And it was all so perfectly done - probably couldn't slip a piece of paper in any of those joints. Additionally, while I am probably not going to copy the engine/prop setup, I definitely learned something from watching these types of models fly in a wind. They were *excellent* at penetrating into the breeze - and they seemed to fly just about the same in the calm.

>I'd add the Yatsenko designs, especially for the advanced
>structural concepts - moulded composite shell construction,
>the engineering excellence of the take-apart fittings and
>the overall package of airframe and engine.
>
>Must be one of the few designs where the basic engine design
>is driven by what is required by the airframe, rather than
>vice-versa.
>
>For whatever reason, it works in a wide range of conditions.

Beautifully stated, Dave. Accurate as heck, also.

although I develop sort of a tic when the subject of takeapartabililty is made a design criteria for a stunt airplane, one can't deny the state of the world politically has made that aspect an important one. Too bad! The Yatsenkos have done a magnificent job of adapting to today's world.

I also give the Yatsenkos high marks for having the foresight and drive to develop a uniquely stunt oriented engine. I've often used the phrase "wealth of mediocrity" to describe the current plethora of engines available in the western world. Excellent engines adapted to our use by innovative craftsman based on high performance high performance RC planforms. These are excellent powerplants as has been proven repeatedly in national and international competition.

The beauty of the Yatsenko (and Belko engines as well) is the fact that the economics of the countries in which they were developed made such uniquely "niche" market place engines viable. Because they have a worldwide market for such unique powerplants and because the economies of the countries in which they are produced are currently depressed, the production and sale of such special made engines is worth doing. A classic case of capitalism at work to benefit the entrepreneur.

The west, on the other hand, with a plethora of major manufacturers making literally thousands of engines which have proven adaptable to our needs, simply couldn't support the "ground up" development of such engines. The cost of producing them for our tiny market simply couldn't be recovered in sales.

If I was 40 instead of 60 and, if I was still trying to earn my chops rather than coasting into retirement, you can bet there would be a couple of Yatsenko engines in my shop right now.

Don't read too much into this comment. I haven't flown one of these and my comments are based on observation only. I'm not pretending to know that these are superior to the very good engines I've used successfully for many years since the advent of the tuned pipe era. I'm just saying that these very quiet, obviously powerful, economical engines obviously provide performance the equal of any in the right hands. You've gotta think they're worth investigating.

However, as much as I like the Yatsenko Classic (I believe that's the name of the best known of their ships) you wouldn't likely see one in my shop. Not because it isn't a cool design that flies with the best...but because it's a buy and fly operation. Not my cup of tea.

If we take up a collection and buy you one of these motors, will you build another airplane?

Thanks for the kind words, Ted. I was fascinated by the "clean sheet" approach that these models represent - though to be honest, the general layout has evolved over at least 10 years - you can see the ancestry in the KA-10.

If you travel and fly, the take-apart feature is an absolute godsend, transporting a box/case 29"X14"X8" beats a one piece anyday, weight penalty notwithstanding.

As for the engines, all those out of work engineers from the eastern european aerospace industry had to do something for a living! Seriously though, some very good engines have come from that part of the world, look at all the TR, Combat & speed hardware - they have a common feature, beautiful piston/sleeve fits and very good metallurgy.
And, quite correct- costs are low(er) and that makes smaller batch manufacture viable. We get the benefit.

The airframe/engine package is certainly one approach, obviously effective in the right hands, there are other approaches that work as well or better - again, in the right hands - I guess that it is the hands that count, not the hardware.

I only have a few flights on the model/engine that Yuri flew at the w/champs & nats, but I can vouch for its uncanny ability to fly at a remarkably constant speed, despite what speed the engine seems to be running. Pity that you don't come to Oz these days - it would be interesting for you to fly it.

Now, it just so happens that I have a spare engine, and they do fit ST60 bolt pattern y'know....

>Fancher's Trivial Pursuit
>1. Same as Walker on many pointS.

I'd emphasize the longer tail moment, a defining point of this design and new direction at the time of Ted's earlier articles (Imitation) - I think.

>2. High angle of attack wing (allows minimum over rotation in corner).

I'm presuming you mean its large leading edge radius (and resultant easier and quicker transition to airfoil 'high point') allowing higher a.o.a. before stalling. Igor might say that useful lift comes lower in the linear part of lift curve. I'm thinking that the movement of c.p. (change in moment coefficient) with change in a.o.a. is less - an advantage in trimming, perhaps allowing more aft c.g. I can see this and corresponding larger flap deflection then limiting the required fuselage a.o.a. 'seems though that the non-flapped part of the wing itself then would be at a lower a.o.a.

>3. Low drag (requires minimum output from the engine).

The wing must be draggier though.

>Berringer Sportster:
>1. Designed for a 4 stroke.
>2. Extreme forward CG.
>3. Long tail moment.
>4. Counterbalanced elevators.
>5. High angle of attack airfoil.

I'd add the distinctive higher aspect ratio wing with higher than usual taper ratio and very small, inboard, tapered flaps, limiting the negative pitching moment and thus the damping of elevator-induced pitch changes. This is a distinctively different philosophy, perhaps trading tail arm length for lost flap-originated pitch damping. Perhaps too, the long arm, small flaps, and lower Reynolds Numbers of the outboard wings limit what would otherwise be a steeper lift curve from high aspect ratio to smooth things out. The long moment must give real pitching authority, since there is no flap induced negative moment to overcome. We noticed some roll in inside-outside transitions and slight over rotation of the fuselage for this plane at the world's. This is a technically distinctive design.

One thing I'd say to Larry's original post is that the mechanical complexity of a stunt ship is not the whole measure of how "technical" it is. The simpler a *high-performance* design is, the more subtle and clever must be the complex interactions of its parts - moveable or not. This is akin to why "simple" controlliners flying in a hemisphere require much more sophisticated mathematics to describe their dynamics than would be imagined by the typical 3-axis control modeler/designer. I have a flapless design (dormant these Summer months) that has a lot of mathematically modeled design compromises to determine areas, moments, and tail "volume", and to place lateral M.A.C.'s advantageously for a higher than usual aspect ratio. It looks simple, but it is really subtly complex in order to attempt designed-in solutions to problems that are more usually trimmed out by additional moving surfaces. If it works, great. If not, it means that the complexities of this "simple" format defeated me. It's characteristically the engineer's ideal to do the most with the least. We'll see sometime how well I did this (well, I actually did work on the thing today!).

Of course, a design's achieving great flying qualities through evolution or trial and error does not mean that it is not pretty sophisticated on an abstract plane. So does "technical" mean complexity, originality, or something subtler - or all of these?

SK

>>3. Low drag (requires minimum output from the engine).
>
>The wing must be draggier though.

Low cornering drag. (induced?) This is what we are mostly concerned with in stunt (not wholely but mostly). This is where the real powerful engines show their stuff, in their ability to overcome drag and gravity when less powerful engines will allow the airspeed to drop.

Flying level does not require much power. (parasitic?) The thick blunt airfoil is somewhat offset by higher aspect ratio.

As far as tail moment, I am not sure that I can say that the difference of less than one inch would have very much effect in the long run. The Impact is 17 5/8", the Patternmaster is 18", and the TP is 17 3/8". I have moved the wing more than these differences and cannot say that the moment made near as much effect as the CG location/CL correlation. Al always told me that anything less than an inch was probably insignificant.

All of my designs use an 18" tail moment. It seemed like a good middle number and Brett uses it! It also establishes the length of the airplane which is very important for the "fit" in the hemisphere.

LAST EDITED ON Oct-26-04 AT 01:28 PM (CDT)
 
>Low cornering drag. (induced?) This is what we are mostly
>concerned with in stunt (not wholely but mostly). This is where the real powerful engines
>show their stuff, in their ability to overcome drag and gravity when less powerful engines
>will allow the airspeed to drop.

Good point for corners. Understood.

SK

I thought Ted and Paul's planes had a low AoA in the corner. I think this because the aft CG 25% helps minimize the amount of control imput. Therefore creating less AoA. Line from the TE to the LE is the AoA right? Well if you have a forward AoA, more input needed=more flap deflection then you have a higher AoA during the corner, as opposed to Ted and Paul with their lower input needed=less flap deflection creating less AoA.

Also having the CG aft would be a reason for going with the slower controls as well. To minimize the jumpies and create real smooth feel at the handle.

I know this has worked for me. The controls in my Geo Bear,28% cg, are slower than that of the 97,24% cg.

Am I worng?

Leave it to an Engineer to come up with a really good question! The problem with the question is that I am not sure by what you mean "technical." One of the most technically complex planes in terms of structure would be Ski Dombrowski's, Nats concourse winning stick structure "Lacemaker." A valid argument could be made that Bob Baron's original Humbug is a very complex plane in an aerodynamic sense. Al Rabe's planes certainly rank right up there in terms of aerodynamic and structural complexity. Jose Modesto and I used to go over to Big Jim's house when we were kids. From a strictly biased standpoint, I think Big Jim's Patternmaster is one of the greatest landmark achievements in stunt and I was there right from the beginning to see it!!
Paul Walker's B17 is generally regarded as THEE preeminent technical achievement in CLPA. From a purely technical standpoint, I would have to rank this plane as the all time NUMERO UNO.

"I don't know about this tuned pipe business. I practiced on that thing until my lips turned blue, and I still can't play a stinkin note."
"Homer J. Simpson"

When you look at Paul Walkers B-17 or Al Rabe's scale looking airplanes, It is almost impossible to see that they are just very highly modified Noblers. I say that in jest, but my point is that they are so unconventional that a great many unusual technical problems had to be solved to make them fly well.

> Or, what do you think is the best
>stunter design, and why?

Definitely a flame-bait question! But I think that you'd have to have missed or ignored the past 15 years to not think the Impact/40VF belongs on the short list. Nothing radical in the numbers (which is *why* it's the best, probably) but the airplane is so fundamentally sound that you just can't do a lot better. And it's perfectly matched to the powerplant. Even after 16+ years, you still can't oo a lot better than a 40VF, either. Maybe *slightly* better, but not a lot.

As far as impressive technical acheivements go, the B-17 is hands down the winner - nothing else I have seen even comes close. Most people (perhaps myself included) can't even understand what all the little parts are intended to do - much less be able to make them work to the level required for competition.

The BI SLOB???

The Skywriter of Zhang Xiangdong
Chinese world champion 1988 1990
Advanced construction, great design and engineering, including moulding
Take apart feature.