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Wing Loading
Last month I started a thread entittled "Landing" and from the replies but not mentioned, was wing loading. It all comes down to, the higher the wing loading, the higher the landing speed most be. What would change if an ARF manufacture produced a scale P-51 with a wng span of, let's say 83" and it weighted 15lbs dry or less. Take a look at BH models and you will notice they already have moved in this direction. I have there GS 83" WS AT-6 and it weighs about 16lbs WET. I powered this plane with a Saito 180 FS and the power to weight is prototypical. I do realize these ARFs are considered sport scale but it would not take much effort to kit bash them.
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RE: Wing Loading
Am I missing something here? Is there a question, or just making an observation?
Yes, wing loading is a major key to your landing procedure. But, and this has been covered thoroughly in the other thread, a plane with higher wing loading CAN still be landed very slow and gentile. How you get there is the difference. You can not do a shallow long glide to a prolonged flair, as with a lightly loaded airplane like an Edge 540. Your entire landing procedure changes. You make a steeper final approach, little or no throttle, and a well timed short flair to a main wheel first touchdown. Your speed is via gravity not the prop, so when you flair, the plane slows immediately. The speed can still be very slow at touch down. You have full flaps, the gear, and you prop all doing breaking form you. With aerobatic planes, I can put the tail on the ground and let aerodynamic breaking stall the wing to the ground. Try this with a heavy war bird and your making major repairs. I never had problems landing the giant scale AT-6, using the above procedure, but the smaller ones seem to be more prone to tip stalls, if you prolong the flair. The closer you move toward the sport scale version of these planes (heavy on the sport), the lighter the wing loading, the larger the tail, and more forgiving you will find them to land. |
RE: Wing Loading
well, a full size P-40 has a wing load of 35lbs/sq.ft. and weighs around 8000lbs empty.
it can land at 90mph with full flap. scale it to 1:7 andthe weight is approx 23lbs with a landing approach of 12mph. 1:7 is about 65" span. now becouse you can't scale gravity, figure an extra 2% increase in speed. so if its a true scale.. there should be no problem landing at those speeds. just my 2cents.. and no I'm not gonna argue this point with whoever. math is math. |
RE: Wing Loading
90mph X 1/5 scale = 18 mph. Pretty slow in my book.
Glad your not going to argue.:D |
RE: Wing Loading
Question: This ARF company. Does it know the meaning of the word washout or does it build a perfactly straight wing? Makes a big difference in my openion. With higher wing loading, tip stalling will be more of an issue without washout.
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RE: Wing Loading
Yes, you did miss the point of my post. "Wing Loading" is the key to performance of any scale aircraft. weather WWII or aerobatic models. Just take a look at monster 3D models. What I'm trying to convey is simple. Keep the weight down and all those nasty traits of a heavy loaded warbird will go away. Going back to the times I flew aerial targets we han a request to increase our air speed by 25% for a high speed variant of our basic target using the same engine and propellor. The first thing we did was get rid of weight. We meet the new requirement with a few additional airfoil changes but the key ingredient was the weight factor. This applies to our models as well. Decrease weight equates to increase performance.
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RE: Wing Loading
ORIGINAL: flycatch Yes, you did miss the point of my post. ''Wing Loading'' is the key to performance of any scale aircraft. weather WWII or aerobatic models. Just take a look at monster 3D models. What I'm trying to convey is simple. Keep the weight down and all those nasty traits of a heavy loaded warbird will go away. Going back to the times I flew aerial targets we han a request to increase our air speed by 25% for a high speed variant of our basic target using the same engine and propellor. The first thing we did was get rid of weight. We meet the new requirement with a few additional airfoil changes but the key ingredient was the weight factor. This applies to our models as well. Decrease weight equates to increase performance. In the case of the aerobatic plane, absolutely!!! Get the weight off, and go fly 3D all day. |
RE: Wing Loading
yah I'll have to agree with Gary on this one.. more weight is better for WarBirds.
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RE: Wing Loading
ORIGINAL: Experten109/40 yah I'll have to agree with Gary on this one.. more weight is better for WarBirds. |
RE: Wing Loading
I went to the Meister web site and found out the wing loading for the 102" WS P-47 version is between 46.5-55 oz/sq ft. They do not list the specifications for the smaller version however IMO I would bet it is in the low forties. This being the case the smaller version would not fly as well as the larger version due to its high wing loading. The larger aircraft is flown faster due to its high wing loading and appears to be flying in a more scale like profile. This is an illusion due to its shear size. Watch a full scale C-5A land. It looks like a glider making its approach but in reality its real landing speed is hidden by its shear mass. When RC pilots make the statement that they are landing with additional airspeed or hot is to say they are keeping the wing from stalling. If the overall weight of the aircraft was decreased this would not be a problem. Structual damage especially to the landing gear is normally the result of an overweght airframe. I see the time coming when the pilots are saying why did I build/purchase such a heavy airframe. Battery technology is a case in point. We went from Nicads to poloy cells all to save weight.
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RE: Wing Loading
ORIGINAL: flycatch I went to the Meister web site and found out the wing loading for the 102'' WS P-47 version is between 46.5-55 oz/sq ft. They do not list the specifications for the smaller version however IMO I would bet it is in the low forties. This being the case the smaller version would not fly as well as the larger version due to its high wing loading. The larger aircraft is flown faster due to its high wing loading and appears to be flying in a more scale like profile. This is an illusion due to its shear size. Watch a full scale C-5A land. It looks like a glider making its approach but in reality its real landing speed is hidden by its shear mass. When RC pilots make the statement that they are landing with additional airspeed or hot is to say they are keeping the wing from stalling. If the overall weight of the aircraft was decreased this would not be a problem. Structual damage especially to the landing gear is normally the result of an overweght airframe. I see the time coming when the pilots are saying why did I build/purchase such a heavy airframe. Battery technology is a case in point. We went from Nicads to poloy cells all to save weight. Also, we have everything we need right now to build light. No need to wait to some future 'time'. And I use it all when building aerobatic planes. War birds are not flown for that purpose, unless you are into thrashing around the sky all the time, and sometimes just want the plane to look military. I see it, and I have no problem with it. But that is not my thing in scale war bird flying. You made this statement as well. "When RC pilots make the statement that they are landing with additional airspeed or hot is to say they are keeping the wing from stalling. If the overall weight of the aircraft was decreased this would not be a problem." Well. I had an Extra 300, with aerobatic-type wing loading, that I needed to equip with an 8" prop and spoilerons just so I could get it slowed down, And almost every landing was a tail first stall landing. Now consider the full scale war bird being landed by a new pilot who misjudges the flair and slams it in from 6'. The abrupt arrival will likely cause some damage, would it not? Does the pilot say to his commander, "but Sir, the plane was too heavy"? Not a chance!!!!! It matters not how heavy it is, you fly and land accordingly. |
RE: Wing Loading
One thing you can't change or scale is Physics. Air molecules behave according to certain laws of physics.. Ever heard of Reynolds Number? I'm not an aeronautical engineer, but I do know it has to do with the ablility of a larger wing (actually the chord line) to carry more per square inch/foot. It's a factor of the ability of molecules to follow the surface of the wing and it's effect on the pressure or lack of pressure , due to the flow. It's actually used in fluid dynamics, and air behaves like a fluid.
Basically, it's why "Bigger is Better". Dash |
RE: Wing Loading
Wing loading is a function of volume of the wing and not just the surface area. Just something to keep in mind when talking about landing qualties etc.
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RE: Wing Loading
What formula are you using for Wing loading that has volume in it? squared not cubed!
However, I do agree volume or as I would suggest "airfoil thickness" does affect your max speed and landing speeds... sometimes significantly. Dash7ATP : correct "math is math" is not always as it seams. Reynolds numbers in practical use, allow the aero engineers to convert readings captured in a wind tunnel on a scale model to be applied to a full size aircraft. They is it in various formulas as a conversion if you will. It is not Linear either. But in the end it allows them to accurately predict the t-off speeds, climb rates, cruise speeds, landing speeds, stall speeds....flying characteristics of the new design. As he said, root issue is because the molecules can not be scaled down. Everything in aviation design is a trade-off of one performance factor over another. Kent Walters (1/8th AF, SBD Dauntless fame) has published many articles over the years trying to explain the need for "Scale Speed" in judging. Good ref material. |
RE: Wing Loading
Good stuff guys. Very interesting.
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RE: Wing Loading
ORIGINAL: flycatch I went to the Meister web site and found out the wing loading for the 102'' WS P-47 version is between 46.5-55 oz/sq ft. They do not list the specifications for the smaller version however IMO I would bet it is in the low forties. This being the case the smaller version would not fly as well as the larger version due to its high wing loading. |
RE: Wing Loading
I would disagree that the higher the wing loading the faster you have to land, especially in large warbirds. This is more true when flying small .40 - .60 size planes then larger 80+ inch warbirds. I don't have the physics to back it up, but if I remember correctly the larger the plane, the wing loading thing kinda cancels out it some way. To put it in terms I can explain, on small .40 size planes wing loading means a lot, a 20 oz will land much slower without stalling vs a 40 oz. But a 100 inch, 85 cc airplane with a 40 to 50 oz loading can fly relative slowly without stalling out on landing. For example on rcscalebuilder there is a 76 pound composite 1/4 scale spitfire that can land at what is considered a decent and relatively slow speed considering the weight. With the weight aiding in a scale like flight. Now if the wing loading theory was correct with a higher wing loading meaning faster landing pattern to prevent stall this spitfire would have to land at turbine jet landing speeds considering the wing loading is way above 50-60 oz. But it doesnt, why? Like I said I dont have the physics to explain it in perfect detail, it just is.
To edit my post, Airfoil shape plays a large part in things as well with a flat bottom wing able to create more lift than say a symmetrical one. The spitfire if I remember correctly was using a scale airfoil though. |
RE: Wing Loading
I'll make this real simple. If you were given the choice between flying a 1/4 scale warbird that weighed 55 lbs or an identical model that weighed 25 lbs which would you choose and why the choice? I started in this hobby flying a three channel glider called a "Gentle Lady" once I had glider under my control I moved on to a more advance design called the "Agila". I was fortunate to have an instructor who taught me more than just flying. He happened to be a full scale pilot. This individual new more than just flying he understood the dynamics of flight. We both were members of the "League of Silent Flight" and I still think about the times we were going for max flight durations to obtain our level three proficiency. He always maxed out my time by several minutes. We were flying identical models or so it seemed. I asked him about this and his answer was to the point. Yours weights more than mine. Takes me back to wing loading.
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RE: Wing Loading
First why are you comparing warbirds to gliders. Unpowered flight vs powered flight and wing loading are two completely different fields. Of coarse you would want light wing loading with a glider for longer flight/ soaring times. With a large warbird it is in a way irrelevant to me, as a higher loaded wing actually flys better, it is more stable in the air, is less affected by turbulent air pockets, and also handles crosswinds better. Back to landing speeds, irrelevant as well. I have had 2 Top Flite ARF 84" Mustangs for comparison, one just to get the feel for warbirds years ago, very light, no heavy retracts or extra gear, the more recent, fully fiberglassed, heavy retracts, extra gear, scale acceseries, ect, ect, difference in weight 6 lbs. As far as landing I really did not notice much of a difference, however flight characteristics and ease of flight was far better with the heavier plane.
If you want to lean the bird down to each their own. to me, fact of the matter is that this is a warbird discussion forum and when it comes to warbirds lighter does not necessarily mean better. Im not about to start throwing lead bars in my planes but I dont really worry about cutting corners or altering plans to cut the weight down either. I have never had any plane to date that I really thought to myself I wish I could land slower in fact the opposite. I like realistic flight, and it actually bothers me when flying my sport planes that some of them the plane has to be almost crawling before it will stall out and get on the ground. I dont like it when I am idling a plane 10 ft from the ground, make my final turn, and fly some 500 ft. to the runway and still need to slow more before the plane will be flying slow enough to flare to land. |
RE: Wing Loading
well look at windtunnel tests, mostly every plane, car, truch, train, boat, building, etc that they put in
there is a much scaled down version of whatever there testing. even today with computer sims they still use the windtunnel. there not to concerned about air molicule sizes, and it produces accurate results. so if one is trying to fly something like a P-47 in a 1:72 scale, I wouldn't worry aboit it lol. this is where weight is your friend to try and cut through air resistance, and not to get tossed around in a 5mph wind. hope this makes sense. I'm no areonuatical engineer though.. I just play one on the internet :D |
RE: Wing Loading
Interesting discussion, but if this "theory" would hold true, everybody would be adding weight to their warplanes. So, how many pouds of lead did you add to make your model fly better 10 pounds, 20? A 82" model with 55 poulds will fly really nice? The Space Shuttle looks pretty solid on the landing pattern...
Again, very interesting discussion... Gerry |
RE: Wing Loading
ORIGINAL: dvs1 First why are you comparing warbirds to gliders. Unpowered flight vs powered flight and wing loading are two completely different fields. Of coarse you would want light wing loading with a glider for longer flight/ soaring times. With a large warbird it is in a way irrelevant to me, as a higher loaded wing actually flys better, it is more stable in the air, is less affected by turbulent air pockets, and also handles crosswinds better. Back to landing speeds, irrelevant as well. I have had 2 Top Flite ARF 84'' Mustangs for comparison, one just to get the feel for warbirds years ago, very light, no heavy retracts or extra gear, the more recent, fully fiberglassed, heavy retracts, extra gear, scale acceseries, ect, ect, difference in weight 6 lbs. As far as landing I really did not notice much of a difference, however flight characteristics and ease of flight was far better with the heavier plane. If you want to lean the bird down to each their own. to me, fact of the matter is that this is a warbird discussion forum and when it comes to warbirds lighter does not necessarily mean better. Im not about to start throwing lead bars in my planes but I don't really worry about cutting corners or altering plans to cut the weight down either. I have never had any plane to date that I really thought to myself I wish I could land slower in fact the opposite. I like realistic flight, and it actually bothers me when flying my sport planes that some of them the plane has to be almost crawling before it will stall out and get on the ground. I don't like it when I am idling a plane 10 ft from the ground, make my final turn, and fly some 500 ft. to the runway and still need to slow more before the plane will be flying slow enough to flare to land. I will add this additional point, and it about building. It is so nice to be able to build, and not agonies over ounces, then pounds, so you can hold a vertical line at will. Weight is just not my primary concern when building a scale war bird. Let me qualify that. I do think about it in the tail, for 1 once back there will cost you 4 in the nose, but overall, scale detail, strength, and life of service are way more important things to build into my war birds, and this makes building much more fun for me. That is just me. Not everyone's cup of tea, but those who haven't tried a scaled out war bird, might just find that this type of building does have a lot to offer. We don't really 'set out to add weight', it just works out that way, and you don't worry about it. Till you build in strength, add scale detail (including the gear and supporting structures), install all the metal gear servos to work all the options (I even use JR 8611 servos on the tail wheels), and redundancy in batteries to power everything, it is what it is. |
RE: Wing Loading
ORIGINAL: GerKonig Interesting discussion, but if this "theory" would hold true, everybody would be adding weight to their warplanes. Gerry many levels. weight, for me anyways = stability, smoother transitions, & scale like manuvers. just how much weight? well whatever it ends up being.. thats what it is. I don't go out of my way to lighten anything. the only notable exception would be the pilots. don't need him breaking loose and flopping around all over the cockpit lol. |
RE: Wing Loading
What formula? L X H X W.. pretty simple. Now that's easy to calculate but not so easy to measure.
http://en.wikipedia.org/wiki/Lift_(force) Lots of good info here :) |
RE: Wing Loading
ORIGINAL: BobH What formula? L X H X W.. pretty simple. Now that's easy to calculate but not so easy to measure. http://en.wikipedia.org/wiki/Lift_(force) Lots of good info here :) |
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