Optimum size/weight for CLPA model

[Jim Oliver]

Guys,

I have checked the tech info provided in S.N. for the last several Nationals and it seems that most of the time the upper classes are won by models/engines in the low/medium 60 ounce range with engines of .60 or larger.
 
I would like to pose some questions:

If there are two models with the same aerobatic qualities, same wing loading/power loading, but one is larger/heavier than the other, which will be easier to fly well under all weather conditions?

How would various weather conditions change the answer?

What is the best size/weight model for CLPA competition and WHY?

I know these questions overlap to some degree but please humor me........

If you think of something relevant that I didn't ask about, please include it.

Thanks for your time.

Jim

[john e. holliday]

Have you read the article in "Stunt News" that was revised version of Wild Bill Netzband's articles.  The gentleman took time to take the math equations and put them in a format that even I can almost understand.  DOC Holliday

[Jim Oliver]

Ty,

Agreed on the wing loading/power loading point......

Doc,

Yup, but I am interested in the views of the guys flying the various set ups.......

Thanks,
Jim

[Howard Rush]

"If there are two models with the same aerobatic qualities, same wing loading/power loading, but one is larger/heavier than the other, which will be easier to fly well under all weather conditions?"

I'll assume you mean "and" by "/".  This is an interesting question, particularly with the condition you imposed.  I don't have the answer, but I'll speculate.  First, I'd think you'd want to use 70-foot lines to maximize the ratio of airplane speed to wind (and turbulence) speed for a given lap time.   Then, given the constraints of your question, pick the engine that regulates speed best and size the airplane for it.  Internal-combustion-engine-powered planes seem have settled at 650-700 square inches.   I don't think electric-powered planes have settled on a size yet.  Bob Hunt's works well, and is rather wee.  The Doherty-Walker setup is a monster with a conservatively designed powerplant.  I would guess that it will get smaller as the best batteries get lighter and experience allows the batteries to be used closer to their limit. 

Bob Emmett complains that airplanes are getting too big relative to maneuver size.  If other judges have this perception, it will cause airplanes to tend to be smaller. 

I don't think the best American airplanes are designed to fly well in all conditions.  They are designed for Muncie, which can vary from calm to windy, but without much turbulence. 

The easiest-to-fly control line airplane that I have ever flown is the OS .40VF-powered Impact that won the 1991 and 2005 Nats.  It would make a great trainer.  My current RO-Jett .65-powered  Impact is easy to fly accurately in most any Muncie condition.  For turbulence, the easily defended choices are David Fitzgerald's Thunder Gazer with the big PA engine and Igor Burger's electric Max II. Between the two airplanes you postulate, pick the size closer to one of the above.

[RC Storick]

Everyone knows where I stand.

My thoughts on the up coming years aircraft. I have flown the BIG airplanes for the last 4 years after attending the worlds and seeing Billy fly his T-Bolt in 04 I thought that I could make it work for me. I was wrong to a point. I can fly these fairly well at the local level. So after 6 airplanes (3 tbolts,1 S6B Super marine,1 jet,1 Continental) I have found it does not work for me. (Of coarse more practice is in order)So I would say I gave it a good try.

My next endeavor is a 660 Square V8, PA .40 UL on a pipe. Trying to keep it under 50 oz.. 40 would be better but not doable. In the 90tys I did fairly well with this type combo. I was using a FP.40 on a pipe and a OS.32F in another.

The problem for me is the concentrated weight (which set up the base line characteristics) The feel in the nose is as if the plane will not turn. So my consistency goes down. The weight of the smaller engine makes the plane more responsive to me.

So as the Pit-bull I am (I don't care what others are doing with airplanes size) for the fifth season coming back with what I think will work for me. Its hard to be a leader when your following someone else ideas.

  Flame away but I will not waver!

[Larry Cunningham]

Definitely the weight. Not only weight, but perhaps more distribution of the weight,
moment of inertia is more significant than CG, since the model is not just an effective
mass rotating about the CG point. It is being rotated in pitch, and being constrained to
something approaching a tangent to the flight hemisphere. And variables! Good God,
there are so many, everything from the airfoil, stab, flap, elevator, rudder and fuselage
side areas, wing area and volume, wing/flap/stab/elevator ratios, wing contour and
sweep, wing tip design, wiggling rudders, line diameter, gyro effects, drag, thrust,
lift, control displacements, engine torque/RPM power characteristics, engine cooling
and heating effects, fuel oil content and viscosity, prop efficiency, line drag,
density altitude, temperature, control system non-linearities, turbulation,
airflow lamination/separation, humidity, airspeed, groundspeed..

Oh yeah, and *COLOR SCHEME of the model! (What did I leave out?)

L.

*e.g. if you use a top dark/bottom light paint scheme on the fuselage with a
separation line which is not very close to horizontal in level flight, the
optical illusion can make the model appear askew in pitch..

"The rule is perfect: in all matters of opinion are adversaries are insane." -Mark Twain

[Jim Oliver]

Based on my very casual research, I agree that the size seems to have settled in the 650 to 700 sq. in. range, with engines in the .60 to .75 range.  Those two facts probably drive the weight to whatever yields an 11 to 13 ounce per sq. foot wing loading.

Sparky, and many others have stated that they fly better (for whatever reason) with a smaller, lighter model.  Not sure if they mean lighter overall weight or lighter wing loading or both.  

My limited experience in CLPA has demonstrated to me that the .40 size models require less physical strength to fly than the .60 size models; I believe this to be a function of overall weight rather than actual size.  

I would like to see some data that relates performance of CLPA models at different weights to the physical size/weight/strength of the person on the handle. I suspect that there is a maximum weight model for each of us, and that the max weight may not be as high as we might think.

Comments?

Jim  

[SteveMoon]

Speaking from just my own personal experience I prefer to fly a plane
that has about 650 sq in of wing area and weighs about 58 - 64 oz. This
just seems to work for me. I have flown Bears, Impacts, SVs, Saturns, and
many others and I really do prefer planes on the 'smaller' side. I would
even say that if I was to 'fudge' one way or the other on the size of
the wing, I would go a little smaller; say 630 sq. in.

As for weight, not too light and not too heavy. Sounds pretty simplistic,
but it's true. For me, a plane that is too light feels a little jumpy and just
doesn't penetrate well. An overweight plane will stall in tight corners and
generally be difficult to handle.

I think planes that are in the size range listed above look good in the
circle as well. Really big planes look 'cramped' to me. They seem to
overpower the space that we are requred to fly in, thus taking away from
the flying impression they leave.

Later, Steve

[phil c]

The elephant in the room here is that the plane has to be heavy enough to pull the lines straight enough that they do not greatly affect maneuvering.  Given that "same aerobatic qualities, same wing loading/power loading" both plane will fly just fine.  The heavier plane will fly better under all conditions because it will pull harder and reduce the effects of the lines.  Just look where trouble occurs-  in a heavier wind the lines bow noticeably as the plane heads into the wind because the ground speed slows, reducing line pull.  At some point, as the wind increases, every plane gets to the point where you just know you won't be able to get it through a RWO or overhead eight.  Another trouble point is the square eights.  16 sharp maneuvers in quick sucession can bleed off enough speed that you can see the line sagging and swinging around on the last few corners.

The other end of the elephant is air speed.  Virtually everyone flys in the range of 52-55 mph airspeed(calculated from line length and lap time).  Going faster requires fabulous reflexes and a completely redesigned airframe.  The required airspeed pretty much dictates the plane weight and line length to keep the lines tight enough for precise flying.

[Bob Reeves]

One issue that hasn't been talked about unless I missed it... I believe... If two pilots are competing in the same class, one flying a 35 size airplane and the other flying a 650 sq inch something, the larger airplane will score better unless the pilot really screws up.

650 and 60 ounces is about my limit and even then I had better have my feet planted if it's windy. 35 size airplanes are less work to fly but they don't win contests..

[Busby]

Generally ,I agree with most folks that the smaller plane is easier to handle in the wind. I know that I cant handle the larger planes in the wind, they just physically beat me up; so regardless of scores I  will be sticking with the 650 ,40/51 size planes.
Busby

[Brett Buck]

Generally ,I agree with most folks that the smaller plane is easier to handle in the wind. I know that I cant handle the larger planes in the wind, they just physically beat me up; so regardless of scores I  will be sticking with the 650 ,40/51 size planes.

   I pretty much agree with the crowd on this one - I would say that in the range of 650-700 is about the max, with whatever the weight winds up. All of the larger models I have seen seemed too large for the circle, Windy's second (1200 square inch) Sweeper being a hallmark example.  Airplanes in this size range need to weigh somewhere between 55-70 oz.

   I am no small guy, but I too have about all I can handle above 20 mph with this size model. And, 20 mph is A LOT of wind to fly model airplane in regardless of size.

    Brett

[Brett Buck]

One issue that hasn't been talked about unless I missed it... I believe... If two pilots are competing in the same class, one flying a 35 size airplane and the other flying a 650 sq inch something, the larger airplane will score better unless the pilot really screws up.

    I haven't seen much evidence of that with good judging. Whitely used to beat the holy crap out of us on a regular basis with his Shark 35.

    What holds back most 35-sized models is that they are also classic models, with all the limitations that implies  - typically, small tails, excessively large flaps with thin wings, and frequently short tail moments. And frequently classic-style control systems and engines. Some of them, with modern engines, fly pretty darn good, but don't have that extra level of sophistication that other more modern airplanes have. It's not the size, I suggest, as much as it is the flying qualities.

    One of the hardest but most useful things I ever had to learn about stunt is that *more accurate flying gets better scores almost all the time*. It's so simple compared to the various complex "impression points" theories that a lot of people enjoy that almost no one believes me.  If you don't score well, it's not your name, it's not the size of your motor, it's not how much static thrust you have, it's not the motor noise, it's not the color of your "stunt pants" - it's that you made more mistakes than the other guy! 

    If flying a smaller airplane means you fly with fewer or less obvious mistakes, then flying a smaller airplane will get you a better score.

      Brett