News:



  • March 28, 2024, 06:10:05 PM

Login with username, password and session length

Author Topic: Why Are Big Planes Better?  (Read 11447 times)

Offline Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3243
Why Are Big Planes Better?
« on: August 09, 2015, 10:06:07 AM »
Is it because the bigger total weight at the same speed keeps the lines tighter? So the goal would be to build the max weight for the line size rule with as much wing area as you can?


Thanks,
MM

Offline Dan McEntee

  • 23 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6824
Re: Why Are Big Planes Better?
« Reply #1 on: August 09, 2015, 12:11:01 PM »
   Bigger plane doesn't necessarily have to mean heavier airplane. Larger airplanes have larger wings, meaning more wing area, which contributes to help keeping total wing loading lower, which is what we are interested in. If you have looked into the history of the event, the size of models have been up and down as trends develop, culminating in perhaps the largest competitive stunter in Windy's Sweeper. Do a search here on the forums and you can read all about the model, I don't think there has been a competitive stunt model bigger than the Sweeper. This was at a time when the trend was going larger in the thought that they presented better to the judges among other things at the time. Size trends have swung back the other way a bit. Smaller models can do a good job, depending on the guy at the handle, with Todd Lee and his eighth place at the NATS this year with his "flying test be concourse winner" powered by an LA.46. The size and weight of a model have really no basis in line tension, although a heavier model will pull more, but if the model isn't trimmed properly, it can get slack on the lines at the wrong place very easily. A successful model is the total sum of all it's parts, model design, properly tuned power plant, and a pilot who understands what he sees and feels when flying it. You can take the model Paul Walker won the NATS with, and give it to a intermediate or advanced class flyer, and it won't make a NATS champion out of them. Model size, for a lot of people, is dictated by how much room they have to build, store, and transport the airplane!
  Type at you later,
  Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)

Offline Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3243
Re: Why Are Big Planes Better?
« Reply #2 on: August 09, 2015, 12:57:26 PM »
I just figured to get great line tension at 90 oz max for .015" wire at the normal wing loading would put you at about 825 sq. in. I would also guess a heavier plane would make the control input springy on .015. Allot of conflicting parameters in this stunt thing.

MM

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: Why Are Big Planes Better?
« Reply #3 on: August 09, 2015, 02:08:41 PM »
Allot of conflicting parameters in this stunt thing.

Yup.  If it was easy, I could do it.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Matt Colan

  • N-756355
  • AMA Member
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3439
Re: Why Are Big Planes Better?
« Reply #4 on: August 09, 2015, 02:55:40 PM »
I just figured to get great line tension at 90 oz max for .015" wire at the normal wing loading would put you at about 825 sq. in. I would also guess a heavier plane would make the control input springy on .015. Allot of conflicting parameters in this stunt thing.

MM

At 90oz, it would require .021" lines.

Bigger airplanes fly smoother, they are easier to fly, and don't get tossed around in the wind as much as a smaller airplane. They pull more than smaller airplanes, but that's to be expected when you get bigger. I personally like the pull, I like knowing the airplane is there at the end of the lines. That's my own personal preference though.
Matt Colan

Offline Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3243
Re: Why Are Big Planes Better?
« Reply #5 on: August 09, 2015, 04:09:31 PM »
I must have got some bad info. What is the max weight for .015" flying lines?

Offline Trostle

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 3338
Re: Why Are Big Planes Better?
« Reply #6 on: August 09, 2015, 05:23:37 PM »
I must have got some bad info. What is the max weight for .015" flying lines?

Two points here.

First, to answer your question,  the maximum weight allowed for a CLPA model in competition for a 2-line system using .015" diameter multi-strand cables is 64 oz.  It is all in the rulebook.

Second,  somewhere or somehow, you seem to be thinking that a heavy CLPA model is necessary or desired.  I can think of no reason to deliberately build a stunt model to have unnecessary weight.  (This statement holds unless you subscribe to the school of thought that a stunt ship can be too light where some pilots have been known to add weight to increase the wing loading for an improved performance, but we are talking super light weight construction here like a 40 oz airplane with more that 600 sq in.)

A properly trimmed model with adequate power and a "reasonable" wing loading will provide adequate line tension throughout the pattern and most "reasonable" wind conditions.  The model does not have to be heavy to provide adequate line tension.  Now, if you want to talk about how a Rabe rudder can contribute to line tension during certain maneuvers, we are talking about a whole new subject.

Keith

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: Why Are Big Planes Better?
« Reply #7 on: August 09, 2015, 06:33:24 PM »
It is all in the rulebook.

And the rule book is easy to obtain.  No need to sacrifice your first born son, or even pay postage -- just download it off the AMA site.  There's a chart in there on plane weight vs. line diameter.  Note that the weight vs. diameter is per event -- what holds for a 55 mph stunt plane does not hold for a 200 mph speed plane.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3243
Re: Why Are Big Planes Better?
« Reply #8 on: August 09, 2015, 08:04:03 PM »
I think you misunderstand me. The constant is wing loading and airspeed. If you have a small plane vs big plane with the same airspeed and wing loading, the big plane will pull more because it's heavier right. So greater line tension is one advantage of a bigger plane.

But here's the dilemma, will the big heavy plane on the same lines feel springy on the controls? So, is plane size a compromise between line tension and a solid feel on the elevator?

MM

Offline Target

  • C/L Addict
  • 2019 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1692
Re: Why Are Big Planes Better?
« Reply #9 on: August 09, 2015, 11:42:35 PM »
There is a thing called scale effect in play also.
A 10oz/sq ft loading is light on a big model, but heavy on a 1/2a model.
So the wing loading also must take into account the total size of the model somewhat. Larger models tend to be more efficient than smaller ones.
R
Chris
Regards,
Chris
AMA 5956

Offline Chris Wilson

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 1710
Re: Why Are Big Planes Better?
« Reply #10 on: August 10, 2015, 12:25:58 AM »
I have always thought that a larger model flies 'better" than a smaller one because -

Reynolds numbers are higher (efficiencies as previously pointed out.)

They fly more in a straight line or flat plane, that is to say the arc of travel is not as tight and thus the maneuvers present truer to the pattern.

And any outside influences such as wind gusts or pilot input are less of a percentage disruption, so control inputs should be higher.
MAAA AUS 73427

You have enemies? Good. That means you've stood up for something, sometime in your life.
 Nothing in life is so exhilarating as to be shot at without result.  It's not enough that we do our best; sometimes we have to do what's required

Online Dave_Trible

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6134
Re: Why Are Big Planes Better?
« Reply #11 on: August 10, 2015, 09:08:18 AM »
I think you misunderstand me. The constant is wing loading and airspeed. If you have a small plane vs big plane with the same airspeed and wing loading, the big plane will pull more because it's heavier right. So greater line tension is one advantage of a bigger plane.

But here's the dilemma, will the big heavy plane on the same lines feel springy on the controls? So, is plane size a compromise between line tension and a solid feel on the elevator?

MM
To answer what I think the question is the lines aren't usually much if any concern if they are of the proper weight for the airplane.  There is quite a safety factor built in.  Brand new lines might stretch a bit on the first outing pulling the braids tight.  The real issue might be rubber band controls on larger, heavier ships.  My best airplanes use a .76 and are all over 72 ounces.  I have to use heavy 1/8" wire horns front AND rear and well supported pushrods with pretty stiff control surfaces to stand up in maneuvers and especially in heavy wind.  A springy feel is a killer.  To a certain point ( and there sure is a limit) a bit heavier airplane will penetrate heavy wind better.  May be more about more power than the weight.  I'm no sumo wrestler but I have little trouble anchoring the airplane.  In trim,  it really doesn't pull that hard- but it does pull about the same overhead as it does in level flight.

Dave
AMA 20934
FAA Certificate FA3ATY4T94

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: Why Are Big Planes Better?
« Reply #12 on: August 10, 2015, 09:57:02 AM »
I think you misunderstand me. The constant is wing loading and airspeed. If you have a small plane vs big plane with the same airspeed and wing loading, the big plane will pull more because it's heavier right. So greater line tension is one advantage of a bigger plane.

But here's the dilemma, will the big heavy plane on the same lines feel springy on the controls? So, is plane size a compromise between line tension and a solid feel on the elevator?

At some point your big airplane will outgrow the circle you have to fly it in.  I'm pretty sure that will happen before you exceed the engine displacement or weight limits.

Dave Trible answered the "springy controls" issue pretty well.  I've heard from more than one guy who flies way better than me say that if you're flying a plane at the top end of the weight limit for a given line size that you're not going to be happy with the springy feel of the lines.  If you're chasing after some heavyweight rainbow then you may want to stock cables one size up from what's required in the rule book, and give them a try.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Brian Hampton

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 577
Re: Why Are Big Planes Better?
« Reply #13 on: August 10, 2015, 09:55:39 PM »
By far the best model I've ever flown had 810 sq" and weighed 59 ounces with an ST G51. That's a wing loading of a tad over 10 ounce/sq foot. It was very light on the lines and almost felt like a combat plane but simply went wherever it was pointed. Wind was no problem because I'd designed it to weather vane so it yawed out a little upwind and vice versa down wind. It was the only model that I knew was beyond my capability to get the most out of it. Currently I'm flying an SV-11 and, in comparison, it's a dog.

Offline Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3243
Re: Why Are Big Planes Better?
« Reply #14 on: August 12, 2015, 06:08:06 AM »
810 sq. in. at 59 oz. how did you do that?

MM

Offline Target

  • C/L Addict
  • 2019 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 1692
Re: Why Are Big Planes Better?
« Reply #15 on: August 12, 2015, 10:15:26 AM »
And, which design is it?
Inquiring minds want to know, you know?
Regards,
Chris
AMA 5956

Offline Brad Smith

  • Trade Count: (0)
  • Commander
  • ****
  • Posts: 287
  • Welcome to the Stunt Hanger.
Re: Why Are Big Planes Better?
« Reply #16 on: August 12, 2015, 10:56:39 AM »
yea what he said
Brad smith AMA780054

Offline Randy Powell

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10484
  • TreeTop Flyer
Re: Why Are Big Planes Better?
« Reply #17 on: August 12, 2015, 11:27:04 AM »
Paul Walker flew his 4 engine B-17 and while it about pulled his arm off, the wing loading was pretty reasonable. Very big plane (900+ square inches) and the primary problem was it really needed to fly on longer than 70' lines. It's all a matter of perspective. I've flown 525 square inch planes that flew awesome in the wind because they were well trimmed and had adequate power.
Member in good standing of P.I.S.T
(Politically Incorrect Stunt Team)
AMA 67711
 Randy Powell

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 13717
Re: Why Are Big Planes Better?
« Reply #18 on: August 12, 2015, 05:59:14 PM »
810 sq. in. at 59 oz. how did you do that?

  Back when that was very important, those sorts of wing loadings were not uncommon. 10 is getting pretty far down there, but I have seen (and flown) 720 square inch airplanes in the low 40's. Larry Robertson's "Golden Bantam" with  an ST46 was 42 oz, which is 8.4 ounces per square foot ad many airplanes that size were in the low 50s. Most of my ST46 airplanes were around 630-640 at about 45-48 ounces, which is in the range of Brian's example. If it wasn't pretty light it wouldn't get to the top of the circle with any authority, and if the wing loading wasn't under 12 oz/sq foot, it wouldn't turn.

  Both of those problems are solved with piped engines, high rev/low pitch muffler engines, electric, and even 4-strokes, so you don't really have any motivation to do it. In addition to being light, they also tended to be very fragile. The flight loads were low enough, but they were plagued with stress cracks from the (substantial) vibration, and were easily damaged in handling. I don't know about Brian's airplane, but many times the engines didn't run all that well because of the flimsiness of the structure. Big Jim was one of the first to figure that out and start beefing up the fuselage.

   Brett

Offline Brett Buck

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 13717
Re: Why Are Big Planes Better?
« Reply #19 on: August 12, 2015, 06:06:52 PM »
At some point your big airplane will outgrow the circle you have to fly it in.  I'm pretty sure that will happen before you exceed the engine displacement or weight limits.


   That point was reached long ago. Windy's airplanes from the late 70's/early 80s were as large as 1200 and many around 900. And the only real problem they had was the 70' limit. On 85 foot lines they would have been fully competitive. As it was, he did pretty well even on 70' although it was clearly sub-optimal.

  We are currently flying airplanes that I think are near the reasonable limit - somewhere in the 600-700 square inch range. Once we could decouple the engine displacement and the airframe size, there's no reason to make them any bigger, and the trend has been to shrink them.

    Brett

Online Brian Hampton

  • Trade Count: (0)
  • Captain
  • *****
  • Posts: 577
Re: Why Are Big Planes Better?
« Reply #20 on: August 12, 2015, 09:38:33 PM »
810 sq. in. at 59 oz. how did you do that?
It wasn't easy :). I started by choosing the lightest wood available, they even let me raid their stockpile. Virtually the entire model was built with 1/16" balsa with the hardest part being the fuselage which was curved on all surfaces nose to tail and had an egg shaped cross section based on how strong an egg is if you try to crush one in your hand. The nose had a layer of fibreglass cloth as a "just in case". The wings were fully sheeted with 1/16" while the tailplane and fin were sheeted with 1/32" then the entire model was covered with doped on tissue before painting. Probably the biggest weight saving though was that, because we fly to FAI rules, we don't have appearance points so only enough paint is used for a reasonable look and to fuel proof.

Just to add a bit more detail on the design, tail moment hing to hinge was 21.5", flaps were an integral part of the wing section, tailplane was 1" thick at the root and controls were fully adjustable giving a final range of +-17 degrees for the elevator and +-5 degrees of flap.

Offline Motorman

  • Trade Count: (0)
  • Admiral
  • ******
  • Posts: 3243
Re: Why Are Big Planes Better?
« Reply #21 on: August 13, 2015, 01:59:34 PM »
Somebody told me that big planes score better on big open fields where smaller planes look tiny and a tight field with buildings and trees around, a big plane scores worse because it looks like a lumbering giant but small planes look normal.

MM

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: Why Are Big Planes Better?
« Reply #22 on: August 13, 2015, 02:32:53 PM »
I'm leery of believing that any optical tricks have a big impact on how judges score.  Small impact -- sure, but if one plane flies better because of it's size than the other, I think that'll dominate the score it receives.

Now, if big planes score better on big open fields because they handle big steady winds and big thermals better, and small planes score better on crowded fields because they handle choppy, turbulent wind better -- that I could believe.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Online Dave_Trible

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 6134
Re: Why Are Big Planes Better?
« Reply #23 on: August 13, 2015, 03:31:12 PM »
One might also think that the best, most reliable power systems are in the larger sizes so you build airplanes to best accommodate those larger engines, pipes, props , (batteries?) etc.  A larger ship also just feels more solid on the lines under all conditions and admittedly catches the eye more.  MMM- More Manly Model.

Dave
AMA 20934
FAA Certificate FA3ATY4T94

Offline Tim Wescott

  • 2016 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 12804
Re: Why Are Big Planes Better?
« Reply #24 on: August 13, 2015, 04:14:01 PM »
An overweight Twister just plain flies better than an overweight Flight Streak, which flies about as good as an overweight Skyray, which flies better than an overweight Ringmaster.

I haven't gotten bigger than an overweight Twister yet, but I think that the trend will continue, even if I hope that my Legacy won't be overweight.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Steve Fitton

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 2272
Re: Why Are Big Planes Better?
« Reply #25 on: August 15, 2015, 05:09:51 PM »
Don't build overweight.
Steve

Offline Howard Rush

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7805
Re: Why Are Big Planes Better?
« Reply #26 on: August 15, 2015, 07:27:26 PM »
Somebody told me that big planes score better on big open fields where smaller planes look tiny and a tight field with buildings and trees around, a big plane scores worse because it looks like a lumbering giant but small planes look normal.

You'd think the judges would be about the same distance from the circle in either case.
The Jive Combat Team
Making combat and stunt great again

Offline Howard Rush

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7805
Re: Why Are Big Planes Better?
« Reply #27 on: August 15, 2015, 07:29:15 PM »
Don't build overweight.

Good advice, Steve.  My tummy gets in the way if I need to reach far across the bench.
The Jive Combat Team
Making combat and stunt great again

Offline Randy Powell

  • 21 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 10484
  • TreeTop Flyer
Re: Why Are Big Planes Better?
« Reply #28 on: August 16, 2015, 05:00:14 PM »
It seems planes come to resemble their builders.
Member in good standing of P.I.S.T
(Politically Incorrect Stunt Team)
AMA 67711
 Randy Powell

Offline Dennis Toth

  • 2020 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4209
Re: Why Are Big Planes Better?
« Reply #29 on: September 17, 2015, 05:19:25 PM »
What you need to think of is the presentation. This is a subjectively judged event. Judges try to look at what the ship is scribing through the hemisphere, looking for heights, size, shape and intersections. The way a ship looks as it goes through the maneuvers gives visual information back to the judges eyes (thank you captain obvious). This however is not consistent. The lines, angles, curves of the ship and trim/paint influence  how it "appears" to be flying through maneuvers. The overhanging rudder accentuates the corner as does straight lines in the fuse and paint trim. Large ships fill the frame at slightly longer lines that allow the ship to fly faster for better wind penetration while appearing to complete the maneuvers at the same relative speed as a small ship and shorter lines. The trick is to not over fill the frame (i.e. Windy's Sweeper).

The interesting approach is to have a small ship that flies fast on longer lines but has trim/paint and lines that create the "illusion" that it is a big ship filling the frame. For me a ship that does this is the OTS El Diablo. The El D is roughly the size of a Ringmaster, the sweeping wing shape with the right paint makes it appear the size of a Humongous. Not sure what PA ship does this but it is something to think about.

Best,     DennisT
« Last Edit: September 17, 2015, 06:02:59 PM by Dennis Toth »

Offline Avaiojet

  • 22 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 7468
  • Just here for the fun of it also.
Re: Why Are Big Planes Better?
« Reply #30 on: September 17, 2015, 05:55:11 PM »
Quote
The interesting approach is to have a small ship that flies fast on longer lines but has trim/paint and lines that create the "illusion" that it is a big ship filling the frame. For me a ship that does this is the OTS El Diablo. The El D is roughly the size of a Ringmaster, the sweeping wing shape with the right paint makes it appear the size of a Humongous.

Dennis,

Is this what you're talking about!!

Trump Derangement Syndrome. TDS. 
Avaiojet Derangement Syndrome. ADS.
Amazing how ignorance can get in the way of the learning process.
If you're Trolled, you know you're doing something right.  Alpha Mike Foxtrot. "No one has ever made a difference by being like everyone else."  Marcus Cordeiro, The "Mark of Excellence," you will not be forgotten. "No amount of evidence will ever persuade an idiot."- Mark Twain. I look at the Forum as a place to contribute and make friends, some view it as a Realm where they could be King.   Proverb 11.9  "With his mouth the Godless destroys his neighbor..."  "Perhaps the greatest challenge in modeling is to build a competitive control line stunter that looks like a real airplane." David McCellan, 1980.

Offline FLOYD CARTER

  • 24 supporter
  • Trade Count: (0)
  • Admiral
  • *
  • Posts: 4458
    • owner
Re: Why Are Big Planes Better?
« Reply #31 on: September 17, 2015, 06:07:42 PM »
Several have commented that "presentation" is important, regardless of airplane size.  What seems to be popular with judges is slow, and quiet.  5 sec. or more lap times make it easier to follow for both pilot and judge.  Quiet almost demands electric power, or else a 4-stroker.

Floyd
89 years, but still going (sort of)
AMA #796  SAM #188  LSF #020


Advertise Here
Tags:
 


Advertise Here