Its about aerodynamics, not fashion, it really doesnt matter what clothes you put on the manequin if the proportions are right.
that said, semi scale can be a more challanging build, but I dont see a reason neccesarily that semi scale needs to compromise a planes stuntablilty

Balls . .


Seeing a Yatsenko looks pretty much like a modified Nobler ,
one wonders what wouldve happened had George built a few Magnums instead of a few Noblers.

I consider a decent engine run as important as loading, in the old days people though about 15 Oz a Sq Ft was
a better figure for wind. Certainly 10 / 11 Sq Ft will suffer bluster .

Still air that Macchi is the easiest thing ive flown an accurate pattern with, and it doesnt meet on standard criteria.
But then its an ' artists impression ' scale not dimensional .

Std propotions fly with std proportions aerodynamics .

The MB3 was dead scale , bar airfoil & 75 % cross sections , to the drawings I had . That in the wind
was a ' throttle stuck on a wet track ' type aeroplane. And Heavy . but would carve a smooth path through the
sky and goe where required, though it didnt feel responsive ( inertia). over 18 knots I generally down prop .

A 10 x 4 3 blade spun up hauls 70 + Oz planes , no problem.

for any experianced chap , its like being in 2nd gear on a twist gravel road in a rally car.
Try it in top and youre wasteing your time , or in the scenary .

To get a design to work across a broad range of conditions is ' the law of averages ' or a compromise.

Though having a high altitude , a low altitude and maybe a medium Alt,
with variations of ea for wind strengths might get more design variations,
it would hardly be practial.Unless you had a rich sponser, with no brains ?

What returns would he achieve ?

From what ive seen of ' current design trends ' They APPEAR to fly smoothly in rough air.
They dont bounce and pitch much, but get pushed ' off track ' very smoothly . I might add.

A more responsive plane can be held on a more accurate course, but can kick , buck , rock and bounce .
Might be flying CLOSER to the prescribed manouvre , but looks ' unprofessional ' to some.

Only real valuation would be via . electronic plotting of ACCURACY , if its a accurracy event ??

The Spit you flew had the Big Jim airfoil , though maybe a notch sharper le .Still to blunt in my books ,
IF it were a lightly loaded plane that was well back from approaching stall anywhere, the stall characteristics would be irrelevant.

A lot of considerations are more structural or C.G. related than ' shape ' , the only sane way to do a real light one
would be composites. BUT , it would still require ' stressed members ' for load paths , as the originals were not ' frameless shells ' .

Observeing the State Champs , id say anything semi elliptic will fly smoother in a bit of wind .
Over 18 Knots , Control Authority , Ridgidity , and HORSE POWER hanging in are the primary requisettes
And strong lines with no stretch .

Constant thrust over the Control Surfaces gives you Control Authority.
Had a ride in a Cessna 150 with a 40 hr pilot in a 20+ knot cross wind.
He had enough brains to keep the power well up till the wheels touched,
also my sugestion of surfing the wave lift on the mountain range was quickly discounted,
for some reason.
Fighting a huge tube / rotar in a 150 might not have worked !

Horses for courses.


Basically you need to start with a clean sheet , and unless youve spent years doing structural and dynamics anaylisis
youre intuitive instincts would need to be at a highly elevated state to achive a homogonous entity as a result .

 Berringers thing won the World and Euro Champs , its a scale akro based contrivance ! Doesnt Work ?

Id still consider a Bristol Fighter with a symetrical airfoil @ about 64 in span would be a fine stunt ship below 5 Knot winds.With a big engine swinging a big four blade prop .The scale airfoil , not a c/l stunt  monoplane one .

 God moves in mysterious ways. Its a Bristol F2B .

Bristol wernt clowns , the put Chrysler 383s and
the like in their automobiles .

MB3 would stand comparison to that. , big words like Accomplished , and Aplomb .

Try seeing who does a clean intersection in the centre of the vertical eights if its blowing a bit ,
if you think that ' standard layouts ' stand comparison .

Hurricane

Supermarine S6

deHavilland 88 Comet .

Wynn, hasn't he seen the Yatsenko Shark? What about the Osetrov Extra (Rainbow Models)?

Brian Eather has an Extra and Osetrov used to build the Yatsenko Classic for the Yatsenkos. They all use Rainbow props.

As stated earlier, Semi Scale does not always equal Semi Stunt. Dressing the manequin may change the appearance, but it's still a manequin.

Building a semi-scale stunter often requires several basic compromises, or Lot's of research (Al Rabe), and a fair understanding of the aero dynamics needed for our type of flying.

I was at the drafting board with Gordan when his Tony was put to the plan. Some of the compromises were the aspect ratio of the wing, size and ratios of the stab and elevator, size, and shape of the fuselage, location of the wing relative to the vertical CG, and legnth of moments to "fit" the requirements.

We went into the designing with a concept. Gordan knew the size and type of power he wanted. He knew the wing loading, and what type and percentage of airfoil to carry the weight he expected it to be, best. He knew the "Numbers" and ratios he wanted, before any thing was put to plan.

Having all the above, and an idea that he wanted it to look very scale when completed, made it much easier to layout the drawing, but, there were additional "adjustments" that needed to be made as the work proceeded. Using his conceptual ideas, and numbers as guides, we were able to resolve those adjustments to flow well together.

A good 3 view is the basic starting point to Scale, and, in our case, Semi-Scale. The Tony was picked for several reasons, first, it was a favorate of Gordy's since he built his first Warburton Tony. He might have built another, but he wanted a larger plane that looked more scale.

My first order of business, was to digitally "trace" the 3 view drawing into the CAD program, so we would have the dead on scale shapes to begin from.

It was noted right from the beginning, as we looked at the relationships, that the wing aspect ratio was much higher than we were comfortable with. It might have worked, but experience had shown that high AR ships, though usually very efficient, suffered in the wind and turbulence when flown as we do, for stunt. So the dilemma becomes how to reduce the AR, while maintaining the distinctive looks of the wing shape? This can be tricky business. The entire idea is to fool the eye.

Because Gordan had already decided on the type, and amount of power he was going to mount in the nose, and had a design goal for wing loading, he had several of the needed parameters to design the wing. He also knew what percentage of thickness he wanted for the airfoil, and the airfoil itself that he wanted, so the basic size, span, and chord could be computed. It took several attempts, but eventually the right compromised shape was put down that did the job.

With the information previously decided, and the new information gained so far, we were able to figure, and set, the size of the stab and elevator. Gordy knew the percentage of the total wing area he wanted for the flaps, and the elevator, as well as the percentage of elevator, in relationship to the stab. These force arrangements determine how responsive, and the quality of the turns can be.

Having determined, and set, the above, he still needed the fuselage to hold and tie all this together. Another compromise may possibly be required to accomplish the job.

In the case of a stunt plane, the fuselage must have a long enough nose to mount the engine, and a tank large enough to feed that engine long enough to fly the pattern, with a little reserve.

This forms the basis for the next set of compromises.

A nose legnth is selected, and the tail moment is computed to balance the engine , prop, and spinner. This is all based on estimating the weights of the components either side of your derived CG. If you're fortunate, the tail moment will be in a range you can tolerate, if not, then "Adjustments must be made", until it does balance out. It not only affects the nose and tail moments, but also the relationships between the flaps and elevators, as a minimum.

Once Gordy was happy with all this, we had to try and determine the vertical CG, so the wing could be placed correctly so the plane flew with the wings levelled out. Several ways and methods of determining the vertical CG are available, and since we were drawing all this out in a CAD program, we wound up using the side view of the fuselage, with the gear down, and had the computer determine center of mass. It gave us a good approximation for the location of the vertical CG.

It was obvious that the side view was not going to match the computed top view has we had drawn it to the numbers used. Compromising a bit, we first scaled the fuse to a usable size. Simply, it was decided what size spinner we wanted, and then scaled to that size. I first set the fuselage image , lined up to the thrust line, and the back of the spinner, to our computed force layout. The nose was a bit too long, and the tail was close to the exact spot we needed. A little CAD magic, and the fuselage relationships came into clarity, except for one major appearance problem. The modified, scale fuse was wide, and very tall. Gordy could live with the width, it actually made the design look more scale than a narrow fuselage normally seen in semi=scale stunters. Al Rabe also seemed to use wider fuses on his, or at least it looked that way.

The height of the fuse was adjusted by having the CAD system scale in the "Y" coordinates only. We adjusted it to 4% less, and the shape seemed right.

So now, we had most of the parameters set, the thrust line, and the wing chord centerline established, it was now time to set the stab and elevators location relative to those two locations. It wound up a bit lower than the scale location, but not too noticeable when some of the shapes were modified to fool the eye once again.

There are several different things that could have been done, at any of the design stages, that might have affected the overall "looks" of the plane. Choosing from these options and determining the "look" is part of the designers prerogatives. I believe Gordan choose well. His Tony flew very well right off the board, and is a potent stunter, while looking very scale. It looks scale because of the choices made in those cases where the "Eye is fooled". It's as much of a design consideration, in the case of "Semi-Scale Stunters', as the other considerations used to make a good PA Stunter.

 

First and foremost, you need to select a plane that is close to the proportions of a modern stunter. Now if you can figure a way to make the engine nacelles very light and low drag, the A-10 would make a killer semi stunt plane.

The A-10 is so recognizable, you can make liberal changes to the geometry and it still would undeniably be an A-10. The generous stab, the SV-11 shaped wing. The nose moment is too long but not by that much. The landing gear are at just the right place. The only real sticking spot are the nacells and the drag they present. Either traditional IC engine setup, Or better two electric ducted fans with the battery in the nose to balance things out. Don't know how efficient electric ducted fans are though.

It also depends on how you go about it. Al Rabe took 3 views of a Mustang (for instance) and changed what he had to, as little as he could, to make it a stunt plane. Windy Urtnowski took a good flying stunt plane and changed the appearance to give the impression of a full sized plane. It sort of depends on your goals and expectations.

How about focusing on how it CAN be done and not why we should not even try.
The airplane actually exists and flys really well. The problems the designers of the actual aircraft solved are not all that different than the ones we would need to solve. They made it work, so it is clear it can be done. Personally I would rather have and fly one of these even if not at the Nats Open Expert level, than a dozen plank sided On Stroid Nobler clones that modern CLPA planes have become.

As I think about it, with the electric motors mounted in the nacelles you essentially have almost a identical configuration of say a P-47 or other Radial engine nosed model. Other the being weight concious a faux turbine assembly could be built to disguise the electric motor. For judging just remove the props.

Gosh, Peter, I thought my first two suggestions (particularly the second) were quite serious attempts to suggest solutions to the problem.

I guess they can't be if you say so, though.

Thinking even further, I see few advantages to building as a profile first. A built up body won't weigh any more, and possibly may weigh less, and be a lot stiffer.

The wing on the full size, is very high AR, so that would need some attention. most definately, electronics would demand retracts, as long as the weight doesn't get out of hand.

As mentioned, the long nose would allow the battery to have plenty of movement and moment to balance the design.

I'm beginning to like the idea.

I hope Dean Pappas sees this, and offers comments.

Or this: http://www.flugzeuginfo.net/acdata_php/acdata_fantrainer_en.php.

Having given more thought to the subject, Since the greatest benefit from electric appears to be well regulated single speed, at all points and attitudes, for models converted or purpose built for electrons, then I fail to see the drawback to having a pair of electric ducted fans. Yes,thrust from each ducted fan would be less for a given amount of watts consumed, but there are two of them to make up the difference, and, the air blast is still ahead of the elevators. Yes, I know the stab is lower than the airblast, but there may still be some affect at the elevator.

I personally feel, at this point, that would be workable for stunt.

As for gang building, Hmmm, maybe, maybe not. I could see some components being gang built, but I would suspect that each of the builders would want to wind up with a model.

Thats why I suggested that in the end it should be donated to the AMA museum. After that there would be finialized plans and the like and perhaps Builtitright or someone else may kit it. While I'd love to be able to fly it and have it in my hands for a bit, I am more than willing to forgo that, just to see it come to fruition. I am pondering modeling the real aircraft in 3D which allow us to move, modify  and replace things in virtual space, to see how it impacts the overall look of the aircraft. As I have free time I'll research any Orthographic views of the actual aircraft so I can start modeling with some accuracy.

I happen to agree totally with Al Rabe.  My stomach just churns when I see a Spitfire with a straight leading edge, a mid-wing Mustang with no dihedral, or an anorexic spindly fuselage on anything. A semi-scale stunter should, above all, look scale.  Most of the later model WW-II planes have very good proportions for stunt- aspect ratios around 5-6, large tail volume coefficients around .5, it's just that the fuselage and wing have to be at different scales, with some tweaking to get good appearance.  All we are really lacking is a light weight retract mechanism.  Not too many fighters did much aerobatics with the gear down.  I've only seen a few films of Bob Hoover doing some fairly mild aer0batics with the wheels hanging out.

The two main problems, as Al has detailed in his many posts, are getting enough wing area and making the fuselage look right.  Dihedral and wing position are critical too.  The full scale aircraft were mostly in the range of 35-40 ft. span and 250-300 sq.ft. of wing area.  A scale P-51 at 54 in. wingspan would have only about 342 sq.in. of wing area.  So the wing and tail need to be scaled up to about 1.3in/ft.  At 1in/ft the scale fuselage would be about 10 in. high and 4 in. wide.  It can be slimmed down and made not quite so tall by careful balancing of the shapes and location of the canopy and rudder etc.  You just have to grin and bear it with the construction.  About the only way to get a scale-like fuselage at a reasonable weight is to mold most or all of it over forms and use very minimal internal structure.

 First, almost any full size aircraft design can be made into a capable semi-scale C/L stunt model.

 Second, almost any full size aircraft design can be made into a capable semi-scale C/L stunt model.

 In a nutshell, on a "clean sheet" just draw out your desired airfoil, moments, and other desired stunt proportions. Then work the desired subjects scale outlines into those dimensions. I'll usually start that process using scale three-views to get accurate outlines, and then play with the sizing of them to get them to fall into the desired dimensions and proportions of the model. Granted, there are many other things to look at and consider, more on some designs than others, but it's all do-able. One of the most important things other than lightness and wing area is determining proper and workable CG locations, both wing CG and vertical CG.

 Yep, sorta what I meant by my comments too Bill.

 As long as the airfoils, dimensions, power and weight are all good for stunting, the airplane doesn't know what shape it is.

 Yes, it's that simple folks.

I must call this one a "scale plane that will stunt".  With retract gear and RO-Jett 76, the final weight keeps it out of the "contest Performance" category.  But you can't beat the "wow" factor!

I hadn't even noticed that thing has retracts!!!

If you could do the smoke out the wingtip thing on purpose, instead of by malfunction like you did at the Spring Tuneup, it would be impressive as hell.  Route the pipe through the outboard wing, maybe?

One day I'll get this model completed. Soon I hope. Actually scale.

Charles

Of course, semi-scale airplanes can be competitive at the highest level as long as there is enough concern for good aerodynamics, power and weight.  I have a set of 6 hours of design DVDs for the Critical Mass which answers nearly any question about design considerations anyone could ask.  But there is a lot of minutes of little action which lowers the entertainment element to a moderately low level regardless of the sophistication of the exercise.  I put them on SS at what I thought was a relative low price with very little apparent interest.

The Sea Fury in the second photo is sitting by the Walker Trophy.  Semi-Stunt?

Al