Line drag, wing loading, basic model drag, and Reynolds numbers all contribute to the difference. 

I fear that there is no number like the ballistic coefficient to relate the model sizes. You should be able to come up with a weight/frontal are, line size and length for similar designs in nearly the same size to give you guidance.

Wing loading is the total weight a given wing can lift assuming it has enough horsepower to run down the runway at a fast enough speed to generate the lift to fly, same to land. Speed is lift. No speed,  no wind over the wing, no lift or pressure differential.

The standard definition of wing loading is the airplane weight or mass divided by the wing area. 

Seems my short fingers missed the P
so the planes only glide soo far till they run out of SPEED...

Tell that to a gnat.

  1/2A's act like they are flying in honey. Gnats act like are flying in tar.

    Brett

Gno......

Why do they give aluminum foil numbers to bugs

An issue with lift and wing loading that is over looked is that wings have volume to consider as well as area. 

Joe

I agree with 55CHEVR. That is old thinking that goes back to the 1950's FF area. More volume more curve to get around it. Which is giving more lift the curve or the volume. Back in the 1940's and early 50's  FF airfoils were thin 5%. Then much more powerful motors came along and the could pull the thicker 10% airfoil models into the air, time went up and they carried the weight better also. The Ramrod was one of the early thick wings that dominated FF for a few years. I see people put down the volume idea but it was used a lot in FF design many many moons ago. I guess it is just another was of saying use a 18-20% airfoil.
 A 22 ounce Ringmaster will fly a very nice pattern but the 38 ounce Ringmaster is a dog. A ringmaster with a 20% airfoil would be a pretty nice flying plane but they would call it a Flight Streak.
Howard will now set us all straight 
 Lets see how much volume do I need in my new plane?
Ed NOTE      This is all in fun and no one should take it as a attack on there space

Huh?

  "Cubic Wing Loading" again.

     Brett

So,e of the old ideas of aerodynamics ,miss the mark when trying to explane how flight works or is achieved.

Aerodynamics is understood well enough to make flying machines of all sizes that work just fine.  The basics were established in the 19th century.  

Yes and NO...
I was schooled in aviation. And while some of the basics remain the same.
The understanding of fluid dynamics seems to have replaced some of what was once thought as the best explanation of the time.
   I am not saying they don't work...just that some of then have been changed from what it was in the 50's and 60's and 70's even.

No, it hasn't changed.  I don't doubt that you learned it wrong.  Most popularized explanations of how wings work are incorrect.  You can't use them to calculate anything, which should give you a clue.  Phonies who use technical terms they don't understand aren't contributing anything either.  

then i'll stop asking i must be mistaken..

more wing area ant longer wings must not glide any better...

If a honey bee or humming bird can fly even though the math says they cannot. Then the math is incorrect.
Regardless of how accepted the math is by those whom  have done the math.
--------------------------------------------------------------------------------------------
Simply ut all I'm trying to ask irregardless of rn's and other stuff is simply .Any stunt model that can glide 1 lap before landing must have a decent glide.
So what is the approxmate wing area and weight of 10 models that glide well  and are the number close
Maybe  better quest might be  to ask if anyoby knows the
wing area and weight of several models and ask if they glide well ??
No i am not gonna ask about a shoestring and a ringmaster. Though I did when I was younger see a kid fly a very capable sterling f-51 that I know was built very light. Though again I have no measureent of the weight to get any numbers....
 

No i'm not looking for wrong answerd....But I do not know what the wing area of a 1/2 a pathfinder is but it would seem they weight around 10-11 ounces and I would think thay have a decent glide compared to my 1/2a ringmaster covered in nylon and dope. I had that quite a few years ago and would maybe get 1/4 lap before you had to land it.

Do they wear the  al. foil on their  heads?  protect the bug brain from  evil waves?   

   These messages may be helpful in understanding the ins and outs of mind control:

http://stunthanger.com/smf/index.php?topic=11627.msg101613#msg101613

http://stunthanger.com/smf/index.php?topic=19325.msg179129#msg179129

   Brett

In my experience, even the best 1/2A models don't glide very far, perhaps half a lap at most. 

Just as an aside, for scaling models down, I like this formula for weight:

Weight= k x span x area

You establish your "k" for the source model and use it to find the correct weight for the scaled version. Not perfect, but it gets you pretty close! Aluminum foil strikes again.

If I understand what is being written here, the higher the wing loading, the poorer an airplane will glide.  And Renolds numbers have something to do with it also.

Keith

If I understand what is being written here, the higher the wing loading, the poorer an airplane will glide. 

My hazy recollection is that an airframe's best glide ratio is actually the same is its max L/D ratio, and therefore independent of weight and wing loading.  If you make that same airframe heavier, it has to fly faster (and descend faster) for min drag speed, but its max L/D and glide ratio will still be the same. 

I only remember this because I had an irascible old aerodynamics lecturer who would get into animated discussions about movies where John Wayne, having lost both engines in his C-47 over the Himalayas, would try to glide further by throwing all the cargo and equipment out the back door.  This would make Mr Cameron quite cross, and he would say rude things about John Wayne's inadequate understanding of aerodynamics.  Probably not very fair on John Wayne, and to be honest ,I don't know if there was ever even any such movie. 

My hazy recollection is that an airframe's best glide ratio is actually the same is its max L/D ratio, and therefore independent of weight and wing loading.  If you make that same airframe heavier, it has to fly faster (and descend faster) for min drag speed, but its max L/D and glide ratio will still be the same.

Yep, pretty much.

My hazy recollection is that an airframe's best glide ratio is actually the same is its max L/D ratio, and therefore independent of weight and wing loading.  If you make that same airframe heavier, it has to fly faster (and descend faster) for min drag speed, but its max L/D and glide ratio will still be the same. 

I only remember this because I had an irascible old aerodynamics lecturer who would get into animated discussions about movies where John Wayne, having lost both engines in his C-47 over the Himalayas, would try to glide further by throwing all the cargo and equipment out the back door.  This would make Mr Cameron quite cross, and he would say rude things about John Wayne's inadequate understanding of aerodynamics.  Probably not very fair on John Wayne, and to be honest ,I don't know if there was ever even any such movie. 

I can tell you that real airplane  glide much better when light down over a runway.

Randy

i've seenpiper cubs have trouble gliding over the runway..just too light.

Re lower wing loadings glide better than higher.

Once the engine quits the only source of energy to make the airplane continue to move forward is inertia which comes from mass in motion and the interplay of gravity and lift allowing the forward motion to remain constant until you run out of altitude; i.e., the forward motion must be adequate to develop the lift necessary to keep it from turning into a rock...no matter how big the wing.

When the engine quits the drag for a high or low wing loading stunter in level flight is essentially the same (yeah, induced drag is a bit higher for the heavy one but the frontal area and "shape" of the critter is the primary source of drag in level flight for any stunter).  Under power thrust is equal to drag in level flight whatever the wingloading.  
?

There are those among us who search valiantly for the zero oz stunter because it will turn quicker.  OK, to make the following point as obvious as possible, let's assume we've built a zero oz Impact and the other guy's got a more or less normal mid 60 oz one.  What happens to our two Impacts  when the prop stops spinning

When the engine quits on the "normal" one you've got ~60 oz going 50MPH.  There's a lot of inertia/stored energy available (mass times velocity squared seems about right) and the drag will, therefore, slow it gradually but you can establish your best glide speed, then drop the nose and retain a speed well above stall and easily glide a lap or more before landing.  Pretty simple.  Makes for great landings and lots of points.

The zero oz stunter on the other hand will be going more or less the same speed until the engine/motor quits...but then things get a lot different.  You've got the same motion but zero mass.  There is no inertia/stored energy.  The drag on the airframe, however, will be the same as the drag on the "normal" one.  As a result the forward motion will essentially stop, the wing will quickly stall and lose the ability to produce lift no matter how high the nose and the airplane will fall to the ground not much further around the circle than where the prop stopped producing thrust.

Now, I fully recognize it is unlikely anyone will, in the near future, build that zero oz stunter but the forces in play are the same...only the degree of difference changes.  If you want a good example of the beauty of inertia go watch some FAI speed models turning close to 300 KPH and count the number of laps before touchdown after the engine quits.  Now go to the combat circle and watch what happens when the engine quits at 115 or so MPH on a 500 square inch aerobatic machine that weighs--what, Howard--less than 20 oz???  Which has the higher wing loading?  Which glides the furthest?

I know, I've probably got some nomenclature wrong and the math might not add up to what I've "wagged" but I believe the principles and the bottom line pragmatic effects are pretty sound.  If you want that 1/2A to glide for a decent landing aim for a (wagged) wing loading of 8 to  9 oz per square foot of wing area (144 sq. in); less than the 12 to 13 of the average competitive "big" stunter to recognize the scaling effects but still light enough to do tricks with a high zoot 1/2A in the nose.  

I'm not an expert on 1/2As but I'd guess something like a 288 square inch(two square foot), 5 to 1 aspect ratio wing (~38" span and an average chord of 7.5") weighing between 16 and 20 oz would be a pretty good start.

Ted

p.s.  Find that thread on the Stuntfire that was simmering for a while and note the comments about the glide of this ultra light behemoth.  Scott's amazing ships were probably as close to the zero oz stunter as anyone has come.  Flew great, glide...not so great.

This is a bit of an aside but it is one way of getting around the "engine quits, plane falls from the sky" experience that is common in 1/2A models.  Stevens Aeromodel makes a 250 square inch trainer, the Ring Rat 250 - low aspect ratio, fairly thick wing guaranteed to be draggy.  This is an electric powered model and the timer/esc package they sell for it does a really neat thing - it gives the usual momentary speed up to indicate that the flight is about to end then it GRADUALLY THROTTLES BACK SO YOU LAND UNDER POWER.  You always have adequate airspeed and control as you lose altitude.  What a wonderful setup for learning to fly control line!  They also have a smaller 100 square inch machine and I suspect that they do the same thing on the power package for it.

My guess is that there is some optimum point between too light and too heavy. Too light and line drag becomes a huge factor. Too heavy and induced drag is the culprit.

And, although engine off glide is interesting, I would prefer to optimize for maneuverability.