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#11
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questions on multi-wing planforms
I don't want to be too negative but could I suggest that if you are
struggling with these relatively fundamental issues that such a project might be a little beyond you. These are not issues for someone without aerodynamic knowledge and what you describe is certainly not a design that is likely to be successful for a first time amateur designer. However let me give you a little insight into how to tackle the problem. Yes you could develop your own theory based on biplane type theory (i.e. a bound vortex respresenting each wing) and use this to predict the flow field. Any number of aerodynamics texts will give you the basic theory but you will need to extend that for your application. However I wouldn't bother with this with the computational tools available. Just get a Vortex lattice code such as the NASA VLM code or Drela's AVL (or better still a panel code such as PMARC or Peter Garrisons CMARC) and use this. Such an approach is far more accurate and someone who knows what they were doing would have a good feel for the issues and probably fix most of the major problems in less than a days work. However please be careful there are a lot of traps for new players even with these sorts of tools. Don't treat programs like this as a balck box .. try to understand what is going on inside them and what the limitations are. Once you have done your computer analysis build a large scale model and go and fly it before you waste time building the full size airplane. "pTooner" wrote in message ... Firstly, I am new here although I've been reading for a few days. For anyone with more knowledge than I, I keep considering building a small 4 wing aircraft. Not stacked, but two up front and two in the rear. I have read frequently of problems supposedly resulting from interference of the airflow between wings, but I can't seem to find anything very specific. I'm fairly confident that interference between the front wings (or rear) can be minimized by reasonable spacing and differing dihedral. I'm not sure what the effect of the airflow coming off the front wings will have on the rear set. I don't know whether I could remove most of the problem by having one set considerably higher (how much?) than the other set or if it is reasonable to have them on more or less the same height. The reason for the concept is trying to get a wingspan small enough to fit into a normal garage and conceivably take off and land from streets and highways. I visualise something in a two place plane that would fall into something of the appeal category of a motorcycle or small sports car. Any thoughts would be appreciated. Gerry |
#12
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questions on multi-wing planforms
pTooner wrote: Firstly, I am new here although I've been reading for a few days. For anyone with more knowledge than I, I keep considering building a small 4 wing aircraft. Not stacked, but two up front and two in the rear. I have read frequently of problems supposedly resulting from interference of the airflow between wings, but I can't seem to find anything very specific. I'm fairly confident that interference between the front wings (or rear) can be minimized by reasonable spacing and differing dihedral. I'm not sure what the effect of the airflow coming off the front wings will have on the rear set. I don't know whether I could remove most of the problem by having one set considerably higher (how much?) than the other set or if it is reasonable to have them on more or less the same height. The reason for the concept is trying to get a wingspan small enough to fit into a normal garage and conceivably take off and land from streets and highways. I visualise something in a two place plane that would fall into something of the appeal category of a motorcycle or small sports car. Any thoughts would be appreciated. Gerry John Roncz called a 3 surface airplane he participated in the design of "the aerodynamicists full employment act"! You will, with optimization of all the variables. be lucky to get 40% of the lift/drag ratio of an equivalent conventional planform. But the bigger problem will be control. Pitch stability, in and out of ground effect, will be a formidable problem, as will stall characteristics. Compromises needed to make the handling acceptable may make the efficiency even worse. I agree with Ernst - a low aspect ratio delta/lifting body makes more sense. Perhaps a 2 seat Facetmobile with the outer portions folding inward like a Dyke Delta. But have you looked at all the wires around most roads? Not an area I would want to use for landing and takeoff. |
#13
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questions on multi-wing planforms
"flybynightkarmarepair" wrote in message oups.com... pTooner wrote: Firstly, I am new here although I've been reading for a few days. For anyone with more knowledge than I, I keep considering building a small 4 wing aircraft. Not stacked, but two up front and two in the rear. I have read frequently of problems supposedly resulting from interference of the airflow between wings, but I can't seem to find anything very specific. I'm fairly confident that interference between the front wings (or rear) can be minimized by reasonable spacing and differing dihedral. I'm not sure what the effect of the airflow coming off the front wings will have on the rear set. I don't know whether I could remove most of the problem by having one set considerably higher (how much?) than the other set or if it is reasonable to have them on more or less the same height. The reason for the concept is trying to get a wingspan small enough to fit into a normal garage and conceivably take off and land from streets and highways. I visualise something in a two place plane that would fall into something of the appeal category of a motorcycle or small sports car. Any thoughts would be appreciated. Gerry John Roncz called a 3 surface airplane he participated in the design of "the aerodynamicists full employment act"! You will, with optimization of all the variables. be lucky to get 40% of the lift/drag ratio of an equivalent conventional planform. Can you elaborate? I don't see why this should be true. But the bigger problem will be control. Pitch stability, in and out of ground effect, will be a formidable problem, as will stall characteristics. Compromises needed to make the handling acceptable may make the efficiency even worse. Well, most tandem wing aircraft are designed to make normal stall impossible. (the rutan designs for instance) Pitch stability is a problem that I thought had been pretty well handled by airfoil design in canard aircraft years ago. My thoughts (I wouldn't call it a design) are simply two sets of biplane wings mounted fore and aft. Biplane wings don't normally present much of an efficiency problem except for the bracing which isn't stricly necessary (The hyperbipe was a pretty efficent design) I certainly agree that handling especially in the pitch axis is the major challenge, but I don't see why it should present a much bigger problem than the flying flea family of aircraft where it was eventually solved satisfactorily. I agree with Ernst - a low aspect ratio delta/lifting body makes more sense. Perhaps a 2 seat Facetmobile with the outer portions folding inward like a Dyke Delta. Perhaps, but it's been tried many times and with very limited success. I know of NO attempt to build the 4 wing system that I envision. That seems strange when you consider that about every imaginable combination has been tried at one time or another. Didn't someone finally build an operable ornithopter? But have you looked at all the wires around most roads? Not an area I would want to use for landing and takeoff. Good point, but they aren't everywhere. ;-) Gerry |
#14
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questions on multi-wing planforms
You might look up all the varieties of "Flying Fleas" and the Q-200 kits for
small, multiwing aircraft. "pTooner" wrote in message ... Firstly, I am new here although I've been reading for a few days. For anyone with more knowledge than I, I keep considering building a small 4 wing aircraft. Not stacked, but two up front and two in the rear. I have read frequently of problems supposedly resulting from interference of the airflow between wings, but I can't seem to find anything very specific. I'm fairly confident that interference between the front wings (or rear) can be minimized by reasonable spacing and differing dihedral. I'm not sure what the effect of the airflow coming off the front wings will have on the rear set. I don't know whether I could remove most of the problem by having one set considerably higher (how much?) than the other set or if it is reasonable to have them on more or less the same height. The reason for the concept is trying to get a wingspan small enough to fit into a normal garage and conceivably take off and land from streets and highways. I visualise something in a two place plane that would fall into something of the appeal category of a motorcycle or small sports car. Any thoughts would be appreciated. Gerry |
#15
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questions on multi-wing planforms
pTooner wrote: ... Well, most tandem wing aircraft are designed to make normal stall impossible. (the rutan designs for instance) Pitch stability is a problem that I thought had been pretty well handled by airfoil design in canard aircraft years ago. My thoughts (I wouldn't call it a design) are simply two sets of biplane wings mounted fore and aft. Biplane wings don't normally present much of an efficiency problem except for the bracing which isn't stricly necessary (The hyperbipe was a pretty efficent design) I certainly agree that handling especially in the pitch axis is the major challenge, but I don't see why it should present a much bigger problem than the flying flea family of aircraft where it was eventually solved satisfactorily. This sounds like sort of a biplane version of the dragonfly. ... Perhaps, but it's been tried many times and with very limited success. I know of NO attempt to build the 4 wing system that I envision. That seems strange when you consider that about every imaginable combination has been tried at one time or another. Everytime I've had an idea for some way to build an airplane that I had never seen before it took only a few minutes on the web to find examples of the concpet that had already been built and flown. So I daresay if you have a novel idea that has never been flown there is probably a very good reason why it hasn't. If you are merely interested in being able to get the plane easiliy into a garage, there are many folding wing designs to choose from or adapt. In addition to the Flying Flea, the kitfox is another. Regardless, good luck. Didn't someone finally build an operable ornithopter? There have been many small (e.g. bird-sized) ones flown. You can buy a plastic toy ornithopter for under $50.00 and there are plans available on the web to build a rubber-bad powered version. But have you looked at all the wires around most roads? Not an area I would want to use for landing and takeoff. Good point, but they aren't everywhere. ;-) You have legal restrictions to be concerned with on public roads, but there are private roads. |
#16
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questions on multi-wing planforms
"Robert Little" wrote in message ... You might look up all the varieties of "Flying Fleas" and the Q-200 kits for small, multiwing aircraft. I have done so, thanks. Gerry "pTooner" wrote in message ... Firstly, I am new here although I've been reading for a few days. For anyone with more knowledge than I, I keep considering building a small 4 wing aircraft. Not stacked, but two up front and two in the rear. I have read frequently of problems supposedly resulting from interference of the airflow between wings, but I can't seem to find anything very specific. I'm fairly confident that interference between the front wings (or rear) can be minimized by reasonable spacing and differing dihedral. I'm not sure what the effect of the airflow coming off the front wings will have on the rear set. I don't know whether I could remove most of the problem by having one set considerably higher (how much?) than the other set or if it is reasonable to have them on more or less the same height. The reason for the concept is trying to get a wingspan small enough to fit into a normal garage and conceivably take off and land from streets and highways. I visualise something in a two place plane that would fall into something of the appeal category of a motorcycle or small sports car. Any thoughts would be appreciated. Gerry |
#17
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questions on multi-wing planforms
Even if everything works just the way you dream it will how will you
see where you're going? "pTooner" wrote in message .. . Firstly, I am new here although I've been reading for a few days. For anyone with more knowledge than I, I keep considering building a small 4 wing aircraft. Not stacked, but two up front and two in the rear. I have read frequently of problems supposedly resulting from interference of the airflow between wings, but I can't seem to find anything very specific. I'm fairly confident that interference between the front wings (or rear) can be minimized by reasonable spacing and differing dihedral. I'm not sure what the effect of the airflow coming off the front wings will have on the rear set. I don't know whether I could remove most of the problem by having one set considerably higher (how much?) than the other set or if it is reasonable to have them on more or less the same height. The reason for the concept is trying to get a wingspan small enough to fit into a normal garage and conceivably take off and land from streets and highways. I visualise something in a two place plane that would fall into something of the appeal category of a motorcycle or small sports car. Any thoughts would be appreciated. Gerry |
#18
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questions on multi-wing planforms
"Drew Dalgleish" wrote in message ... Even if everything works just the way you dream it will how will you see where you're going? You are assuming a far more complete design than actually exists, but I don't see why that should be a problem. Gerry "pTooner" wrote in message . .. Firstly, I am new here although I've been reading for a few days. For anyone with more knowledge than I, I keep considering building a small 4 wing aircraft. Not stacked, but two up front and two in the rear. I have read frequently of problems supposedly resulting from interference of the airflow between wings, but I can't seem to find anything very specific. I'm fairly confident that interference between the front wings (or rear) can be minimized by reasonable spacing and differing dihedral. I'm not sure what the effect of the airflow coming off the front wings will have on the rear set. I don't know whether I could remove most of the problem by having one set considerably higher (how much?) than the other set or if it is reasonable to have them on more or less the same height. The reason for the concept is trying to get a wingspan small enough to fit into a normal garage and conceivably take off and land from streets and highways. I visualise something in a two place plane that would fall into something of the appeal category of a motorcycle or small sports car. Any thoughts would be appreciated. Gerry |
#19
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questions on multi-wing planforms
pTooner wrote: "ELIPPSE" wrote in message oups.com... pTooner wrote: Firstly, I am new here although I've been reading for a few days. For anyone with more knowledge than I, I keep considering building a small 4 wing aircraft. Not stacked, but two up front and two in the rear. I have read frequently of problems supposedly resulting from interference of the airflow between wings, but I can't seem to find anything very specific. I'm fairly confident that interference between the front wings (or rear) can be minimized by reasonable spacing and differing dihedral. I'm not sure what the effect of the airflow coming off the front wings will have on the rear set. I don't know whether I could remove most of the problem by having one set considerably higher (how much?) than the other set or if it is reasonable to have them on more or less the same height. The reason for the concept is trying to get a wingspan small enough to fit into a normal garage and conceivably take off and land from streets and highways. I visualise something in a two place plane that would fall into something of the appeal category of a motorcycle or small sports car. Any thoughts would be appreciated. Gerry Look up "Monk Factor"! In quotes that term doesn't bring any reponse in google. Without quotes it brings an unmanageable amount but doesn't appear to have anything to do with aerodynamics. Can you elaborate a bit? Gerry Hi, Gerry! Munk factor has to do with the effect multiple wing placement has on the induced drag of tandem wings and biplane wings. Darrol Stinton in his book "The Design Of The Aeroplane" has an excellent, easy to understand section on it, with lots of graphs! |
#20
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questions on multi-wing planforms
"pTooner" wrote:
My basic concept/question is like this. Assuming optimum airfoil in each case which may well be different; I could build a 20ft span 4 ft chord wing for 80sqft or two 20span 2 ft chord or 4 10ft span 2 foot chord and they all equal the same area. What would be their relative lift and drag numbers? (probably pretty close) BUT would they have strange characteristics at odd angles of attack? (That is a semi-rhetorical question) Since a higher aspect ratio wing generally has a better lift/drag ratio, increasing the effective wingspan would normally be a good thing - assuming all other variables remain constant. But clearly wing gap interference inserts an additional variable. Another thing you might want to look into is the "multiplane" (I couldn't remember the proper name for the concept in my first reply, otherwise I'd have mentioned it earlier). The concept dates as far back as 1893! Horatio Phillips designed (and did some short test flights) of what can only be described as "Venetian blinds" wings. Here are some web sites, with some background info and photos (some of the photos can be clicked on to get larger images): http://www.centennialofflight.gov/es...lips/Tech4.htm http://www.ctie.monash.edu.au/hargrave/phillips.html Another nice photo of Phillips multiplane: http://invention.psychology.msstate....ultiplane.jpeg Lastly, you should consider getting a copy of "Simplified Aircraft Design for Homebuilders" by Dan Raymer. (He has his own website: http://www.aircraftdesign.com/) |
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