In a prior thread, Abufletcher made a comment that set me to thinking. Here's what he said:


"I, for one, don't want a model that flies BETTER than the original. I don't want a RE-ENGINEERED version. I'll never fly a full-scale replica...the closest I'll ever get is a scale-flying miniature. And if the original had adverse yaw, then I want to experience what it was like to fly with adverse yaw (and "a boot full of rudder")."


I'm sure many of us share Don's sentiment. But, does ANY scale model really fly like its full sized counterpart ? I think the answer is a resounding NO !

Just because a scale model is shaped exactly as the full size plane was shaped, right down to the original airfoil, there are several reasons why the model doesn't really fly the same as the full scale. Unfortunately, most modelers have never seen the full scale version fly. Or at least seen enough flying to study the behavior of the full scale.

Why aren't they the same ? Well, there are several reasons. The first that comes to mind is the vastly reduced mass (inertia, if you will). When a 1500 lb. airplane hits a gust, it reacts much more slowly and with less motion than does a 6 lb. model. The result is quick little motions with far greater amplitude than the full size version. That's why scale models look so much more "real" on a calm, smooth day.

Then there's the takeoff and landing problem. The full scale WWI planes were directionally unstable on takeoff and landing roll. We know that. But the pilots were usually able to overcome the instability because the swerves happened so much more slowly. On models, the swerve and flip over onto the top wing can happen so quickly that we sometimes only let out a gasp when it's all over. Again, lack of inertia.

Then there's the problem of how rapidly the model reacts to control inputs. With such low inertia, a model reacts very rapidly. Rolling and pitching motions look far slower and smoother on the full scale machines.

As models are made larger and larger, they approach the behavior of the full scale plane. With their greater mass and inertia, they respond more slowly and gracefully to pilot inputs and gusts. That's one of the reasons why giant scale planes are so popular. But most of us want to have smaller scale models with their correspondingly smaller costs, storage, and transportation problems.

So, my question for this thread is: What can we do to make our scale models give us "the closest experience in a scale-flying miniature" ? (Loose quote from Abufletcher)

Dick

I think there's a lot of promise for interesting discussion here. Thanks for starting us off!

I'll add one simple observation: Different models do indeed fly differently. We can "feel" the difference when we fly them. Some models seem "heavy" in the air, others "responsive." My Puppeteer is a real "dog" but nevertheless (or perhaps precisely because of this) fun to fly. Some models almost fly themselves...and where's the fun in that? Other models take every bit of our concentration to keep them in the air...or to get them back onto the ground in one piece. So it seems clear to me that the basic shape and configuration of a model (at whatever scale) does indeed strongly affect its flying qualities.

So I think we can all agree that a model of, say, a Fokker DrI flies differently than a model of a Sopwith Pup. And if I had to describe HOW the two models were different, I'd say that the model DrI flies more like the full-scale DrI and the model Pup flies more like the full-scale Pup. Nevertheless it might still be true that the ways the two models fly ultimately have more in common with each other than they have with either the full-scale DrI or the full-scale Pup. It may be true that models fly like models and full-scales fly like full-scales.

I think what I was basically objecting to is the attempts to make scale models easier to fly than the original. I don't want a model DrI that flies like a trainer...or a Pup.

I agree... I flew a fokker e-3 and only rolled ittwiceto check throws...I never did it again..I think a plane made to fly like a sport/trainer is to easy.. I want a warbird to challenge me..trying to fly somewhat scale-like is difficult to say the least..a 2000 lb plane rolls slower in full scale, so a 20lb plane must be controlled more precisely to appear slower to emulate full scale..I try very hard to fly my Dad's P-40 scale -like clear down to square landing patternapproach..so much to do , to make it look real..full scale is full scale...flying scale like seems the only way to do it...even if take-offs and landings are as difficult as the real bird.....


SLOPE FAST - SOAR DEEP

guamflyer


P-40 Bro #5 and 6

Our imitation planes can only imitate the real thing. How well will depend on the pilot and the model. Nearly all of our planes are over powered and underweight compared to the real ones. It is up to the pilot to make it look like the big lumbering full sized plane.

You are flying it at the timeslow down a bit and fly smoothly

This sport scale full house control with articulated pilot Curtiss 'Headless Pusher' flew with an OS 26 four stroke. It had a main plane span of 48". That's 96" of span, folks! You absolutely had to build ground speed and fly in ground effect to build airspeed. If the grass was too tall it wouldn't get off the field. You had to gently climb or stall would ensue. While flying gentle control inputs were required or altitude would be lost. Is this kind of flying for everyone? Probably not. Did it replicate what the full scale item did? Who knows but by my feeble research it performed as I envisioned the full scale item did... draggy and slow with all of those struts and wires. Was it enjoyable to fly? For me... ABSOLUTELY! I need to build another one!

This is my excuse for building most of my scale models overweight and underpowered!

I'm not so concerned with having the model LOOK like it's flying in a scale manner. I want it to FEEL to me like it's flying scale. (By the way, in another thread that I started long ago, we discussed how it is that we somehow do "feel" how our models are flying. For example, we can "feel" when the model is "heavy" and we can "feel" when it's "wallowing.")

Fantastic model ARUP!!! The world needs more funky flyers!!!

My Point exactly boys...it's up to the pilot ultimately to make the scale bird look somewhat real....this type of flying is'nt for everyone...Flying smoothly is difficult when up against wind or weather in general...it makes me nuts when I see a guy snap roll a plane not able to do so in full scale, but I am FULLY IMPRESSED with the guy that flies smooth, scale-like and in control...don'nt get me wrong.. if its a cap or extra type of bird then yes by all means... but to be really impressive I prefer to fly as scale-like as possible


SLOPE FAST - SOAR DEEP

guamflyer<br type="_moz" />

Here's that other thread on the "sensation of RC flying."

http://www.rcuniverse.com/forum/m_10...m.htm#10843685

It really comes down to the Reynolds numbers, that is why giant scale platforms work so well compared to the little stuff, the wing loading can be equally heavy on both small scale and giant scale but the small scale will fly like a brick with nasty unforgiving habits and the giant will fly like a home sick angel that is inspiring to fly. Again this is because of the effects of the Reynolds numbers and cubed loading. The larger the platform, the more efficiently it will carry weight and because of the larger platform, there is now better damping in flight giving much better scale effect. Even the very best of warbird pilots will struggle with making a small scale platform look realistic and smooth in the air, and as always, proper setup is always going to be essential on large or small aircraft.

Bob

That's part of it. But scale features like the (correct) scale size of the rudder and elevator will make a model fly more like the original. If the original had a teeny rudder and thus lacked lateral stability, then a model with a teeny rudder will probably act the same. This isn't related to either the Reynolds number or scale loading.

I saw a full scale replica of the Curtis pusher fly at an air show last summer and believe me it flew very scale likecompared to the mustangs flying that day, I could of run below it and kept up; almost. It is amazing to see how far we have come in 100 yrs. Here's a thought wouldn't a 10-15 mile an hour wind for a model be like flying the full scale in a hurricane or something close to it? I've been bounced pretty goodon some commercial flights.

It seems entirely reasonable that if we can talk about scale flying speeds, then we can talk about scale wind speeds. I was once able to "hover" my model nearly vertically to the ground in a medium wind and it would have taken a powerful wind indeed (and a very skilled pilot) to have the same thing happen in full-scale.

Build big, very light airplanes , only fly in dead calm weather and only let expert thumbs on the sticks.

Most of us cannot manage all these, but we can work towards them.
(Unfortunately, small airplanes are easier to handle, heavy planes are easier to build, the wind is always blowing here, and I could certainly practice more!)

Martin

Sure I agree, by all means scale all flight components properly, but after that those Reynolds numbers, loading, and damping issues are in fact a huge part of the problem to flying scale like with the smaller stuff...

Bob

"I want it to FEEL to me like it's flying scale. "

The only way you can have that, is by sitting in the pilots seat, with you at the controls.:-)))))))))))

Les

Last year I took my Nosen Giant Scale P-51 Mustang to a Giant Scale fly-in. During this event I flew it like I fly it all the time. Most of my rolls were done in a barrel roll not axle. My loops were large, 400 to 500 foot. My take offs were long with the tail level with the ground. Landings were done in a rectangle patternn not in a large circle. I never flew it inverted more than 2 to 3 seconds. I was in the company of CARF F4U Corsairs using 5 cylinder raidals doing 110 MPH. My Mustang was clocked at 88 MPH full throttle. The sound of the engine, I was told was more real sounding than most of the planes there. I run a Q-75 with a Master Airscrew 24X12 wood prop turning 5,200 RPM on the ground. This plane weights 34 lbs dry. At the awards dinner on Saturday night, I received the Best Military plaque. I asked some of the guys doing the judging why and this is what they told me: "Your plane was flown more realsitc than any other Giant Scale or War Bird here". So you can see, it's how you fly it that makes a difference.......


Larry

I noticed a big difference in realism, both on the ground and in the air, with WW1 planes, when going from 1/4 to 1/3 scale. I guess it's the inertia or reynolds number, or whatever, but now I am gradually replacing my 1/4 scale WW1 birds with 1/3 scale ones. Of course you have to have room for the bigger ones and they are more expensive because of the engines and heavier servos needed.
I still have a 1/4 scale Fokker D-7 and I try to keep it slow but it still seems too fast to me compared to my 1/3 scale ones. They are all in the 34-35 lb. range.

Jim

You sir, said it all for the uninformed.

Wow ! Some really good comments right off the bat. Evidently I'm not the only one who wants his planes to MOVE realistically as well as look realistic while sitting on the ground.

Realistic motion seems to me to come in many different flavors. All contribute to the image. Here are a few to consider:

SPEED By speed I don't mean how many mph the model is going, but how fast does it appear to be going relative to how fast the full scale version appears to be going. To the eye, speed is perceived primarily by seeing how many times the plane travels it's own length in a unit of time. So if a real DVII goes 5 times it's own length in one second, then the model will look most realistic if it too travels 5 times its own length in one second. That has to do with relating the weight of the model to the size. That's an entire thread on its own, and involves model weight, power, and to some degree piloting technique.

ANGULAR RATES These are the rates at which the model banks, yaws and pitches. Sensei referred to "loading and damping", and I think he has a point. Heavy objects resist motion from external inputs, such as gusts. Think "inertia". And highly damped objects (things like biplanes) lose their angular rates rapidly due to the resistance of the air surrounding them. A kite is a good example of an object that has very little inertia ("loading", if you will) and so it responds rapidly to any wind gust. But the kite also has lots of surface area, so the motions "damp out" rapidly. What we perceive when watching a kite is rapid, almost jerky motions, that die out quickly. Unfortunately, we can't get the light weight required for realistic speed and at the same have the high inertia that is necessary for resistance to gusts. Only in full size does this relationship exist exactly.

DIAMETERS OF CIRCLES A funny expression, but what I'm trying to express is the size of a maneuver compared to the size of the plane. When you do a loop, is the diameter of the loop equal to 2 wing spans or 20 wingspans ? When you do a 30 degree banked turn, is the diameter of your full circle equal to 10 wingspans or 100 wingspans ? To look truly realistic, the relationship between the size of your model and the size of your maneuvers needs to be similar to that of the full scale plane.

Dick

Dick,

You make some very good points and I agree that Speed, angular rates and the diameter of circles really make up the bulk of what it takes to fly in a scale manner.

As an example, the first thing I notice is on take off. If you watch most warbirds for instance, large or small, they will rotate very quickly and will almost immediately initiate an extremely steep downwind turn. This type of flying is not scale at all but fortunately, is easy to fix.

When I take off, I try to use whatever runway I need, then slowly rotate the airplane and then let it fly, then I go upwind quite a way before I ever think about making a gentle downwind turn. I think it helps if you also have some time built up flying full scale airplanes.

I also think flying SPA pattern type competitions really help with this as take-offs and landings are judged maneuvers.

Just my two cents worth.

Brian

It is how large your airplane is as well, presentation, damping, and so on, 102" span is not a small airplane, try and fly same way with a .60-.90 size airplane and the game will change. watch this video, an airplane with a 48" to 60" span will never give the same feel of scale as something this size.

http://www.youtube.com/watch?v=tnB7L-O2VJo

Bob

I think one tool we can use that is in most of our radios is Exponential. I was resistant to it for years, but a pylon racing buddy talked me into using it to smooth out my laps around the course. It works great to smooth out your flying. The twitchyness is what I notice that makes our models not look scale.

Also, I think my comments in the other thread may have spurned on this discussion as well. The objective of the airplane I plan to build will not be for it to fly in a "scale" manner necessarily. The reason I thought of changing the tip airfoil to a more cambered section was so it would look more scale on the ground. Then use a clark Y for the rest of the wing to make it fly better or more easily. I say it at work all the time, "there is nothing wrong with making your job easier". I feel the same way about my airplanes. Nothing wrong with making them fly better.
Keep in mind, this aircraft will not be for scale competition, more of a throw around warbird. There is an important distinction between the two types of planes.

Agreed, that is why I stated in my first post that proper setup is essential, that includes exponential as well...

Bob