If this is your first visit, be sure to check out the FAQ by clicking the link above. You may have to register before you can post: click the register link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. |
|
|
Thread Tools | Display Modes |
#21
|
|||
|
|||
questions on multi-wing planforms
"pTooner" wrote in message
... "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 I am fairly certain that tandem biplane designs existed in the early days--in addition to the obvious case of the Wright Flyer. However, I will second the suggestion to stay with one of the various folding wing designs. Also, unless you are *very* masochistic, you probably won't fly very ofter if you also have to tow the aircraft to and from the airport, so the ability to be towed at highway speeds (or even street speeds) may not be as usefull as the ease of folding and unfolding the wings. I would suggest asking around your local airport(s) regarding the storage cost for a folding wing aircraft--you may be able to share part of a hangar or even get a reasonable deal from a maintenance facility if they have permission to move the plane out of the way when they need the workspace. Also, the way Tee-hangars are constructed at some airports, there may be a half hangar on the end of each row--and a folding wing airplane would only need about half of a half hangar! BTW, depending on the size of the Tee hangars on the row, you might be able to nose a VariEze or even a LongEze into a half hangar and still share the back part of the hangar for storage or office space--depending on the rules at your airport. Also the Nesmith Cougar has a folding wing, and if you are of very small stature there is the Stits Playmate. I hope this helps Peter "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 |
#22
|
|||
|
|||
questions on multi-wing planforms
"Peter Dohm" wrote in message . .. "pTooner" wrote in message ... "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 I am fairly certain that tandem biplane designs existed in the early days--in addition to the obvious case of the Wright Flyer. Well, I tend to think that it's only a tandem wing if both portions contribute substantially to the list. I don't know of any of those, although I'd like to find them for informational purposes. However, I will second the suggestion to stay with one of the various folding wing designs. Also, unless you are *very* masochistic, you probably won't fly very ofter if you also have to tow the aircraft to and from the airport, so the ability to be towed at highway speeds (or even street speeds) may not be as usefull as the ease of folding and unfolding the wings. I would suggest asking around your local airport(s) regarding the storage cost for a folding wing aircraft--you may be able to share part of a hangar or even get a reasonable deal from a maintenance facility if they have permission to move the plane out of the way when they need the workspace. Also, the way Tee-hangars are constructed at some airports, there may be a half hangar on the end of each row--and a folding wing airplane would only need about half of a half hangar! Those are good ideas, but I never consider towing. Picture instead, someone who happened to own a few acres on the dead end of a very rural florida road that is straight as an arrow. ;-) Gerry |
#23
|
|||
|
|||
questions on multi-wing planforms
Awright.
There's more to aerodynamics than that covered by your philosophy. Area and airfoil are not really the right starting place for a new and novel configuration. the dimensions of your wings... First - learn about Reynolds number. Very few of the published airfoils work well below about 3 meg RN. What does that mean in regard to your choices? Well, the two-foot chord wing is going to have to move pretty fast to make 3 meg RN. The four-foot chord wing will have twice the RN from the start. Richard |
#24
|
|||
|
|||
questions on multi-wing planforms
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. Well, let's see. The back wing(s) operate in the downwash of the forward wings, there's a hit there. The upper wings operate in a flow field affected by the lower wings, there's a hit there. Twice as many wingtip vortices, take a hit there, and at some angles of attack, the aft wing(s) will be operating in the vortice of the front wing(s). 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) There is a price paid in efficiency, and in landing speed in making this NECESSARY trait possible. It's necessary because a canard or tandem wing design is very vulnerable to an un-recoverable deep stall. The consequence is that you cannot optimize the angle of attack for both wings simultaneously, and that the C ell Max of the combined system is degraded, making the landing speed higher, or the wings bigger (which will hurt efficiency AGAIN). 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) Pretty efficient for a biplane, but nowhere near as efficient as a conventional 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. Again, by limitations that hurt efficiency. And a good half-dozen people died before the pitch stability issue was solved. That was actually a problem at cruise/top speed. The transition between operating in ground effect and out of it is pretty tricky for a equal area tandem wing airplane. This was seen in some of the first experimental Wing In Ground effect surface skimmers. They had tremendous pitch stability (a problem if you're trying to rotate) until they suddenly didn't, and they would pitch up quite violently. That's one reason the Quickies have ANHEDRAL on the forward wing, and Dihedral on the aft wing, as well as mounting the forward wing lower than the aft wing. In this way, with a pitch up to rotate, both wings come out of ground effect at much closer to the same instant, without a sharp pitch divergence. 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. Various low aspect ratio designs have been flow since the twenties, it's true. The Burnellis, the Spratt, the Fike designs. The Dyke Delta is a low aspect double delta, with the main cabin airfoil shaped. But true lifting bodies were basically unknown until the 1960's. John McPhee wrote about one of them in "The Deltoid Pumpkin Seed". The the Facetmobile is, IMHO, the most successful general aviaition true lifting body design. |
#25
|
|||
|
|||
questions on multi-wing planforms
"cavelamb" wrote in message k.net... Awright. There's more to aerodynamics than that covered by your philosophy. Huh??? Area and airfoil are not really the right starting place for a new and novel configuration. Then where WOULD be the right starting place? the dimensions of your wings... First - learn about Reynolds number. Okay Very few of the published airfoils work well below about 3 meg RN. What does that mean in regard to your choices? Well, the two-foot chord wing is going to have to move pretty fast to make 3 meg RN. How fast? None of these were really choices, just random numbers for explanation. In other words, 4 10x1 wings = 40 sq ft. or 1 20x2 wing = 40 sq ft. The most important single factor in wing design appears to be square feet. ?? The four-foot chord wing will have twice the RN from the start. That's built into the RN equation. What's the relevance?? I have no argument here, I'm looking for info. So far, I've gotten some pretty good references. Gerry |
#26
|
|||
|
|||
questions on multi-wing planforms
"flybynightkarmarepair" wrote in message oups.com... 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. Well, let's see. The back wing(s) operate in the downwash of the forward wings, there's a hit there. That's not necessarily true, it depends on many additional factors. The same could be said for the main sail on a sloop operating in the downwash of the jib, but it works damned well. The upper wings operate in a flow field affected by the lower wings, there's a hit there. Seems I read somewhere that as long as the gap is about 1.5 times the chord that isn''t a factor? Twice as many wingtip vortices, take a hit there, Maybe - I'm not sure about that one. There are certainly other considerations. and at some angles of attack, the aft wing(s) will be operating in the vortice of the front wing(s). That strikes me as the single most important problem with this consideration. But the bigger problem will be control. Pitch stability, in and out of ground effect, will be a formidable problem, as will stall characteristics. See above. Compromises needed to make the handling acceptable may make the efficiency even worse. Please elaborate. Well, most tandem wing aircraft are designed to make normal stall impossible. (the rutan designs for instance) There is a price paid in efficiency, and in landing speed in making this NECESSARY trait possible. It's necessary because a canard or tandem wing design is very vulnerable to an un-recoverable deep stall. The consequence is that you cannot optimize the angle of attack for both wings simultaneously, and that the C ell Max of the combined system is degraded, making the landing speed higher, or the wings bigger (which will hurt efficiency AGAIN). Generally, I agree. OTOH, all designs are compromises of some kind. 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) Pretty efficient for a biplane, but nowhere near as efficient as a conventional design. The published specs don't seem to agree with you there. 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. Again, by limitations that hurt efficiency. And a good half-dozen people died before the pitch stability issue was solved. That was actually a problem at cruise/top speed. Sad, but many people died to learn what we now know about aeronautics. The transition between operating in ground effect and out of it is pretty tricky for a equal area tandem wing airplane. This was seen in some of the first experimental Wing In Ground effect surface skimmers. They had tremendous pitch stability (a problem if you're trying to rotate) until they suddenly didn't, and they would pitch up quite violently. That's one reason the Quickies have ANHEDRAL on the forward wing, and Dihedral on the aft wing, as well as mounting the forward wing lower than the aft wing. In this way, with a pitch up to rotate, both wings come out of ground effect at much closer to the same instant, without a sharp pitch divergence. Interesting observation that I haven't come across previously. 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. Various low aspect ratio designs have been flow since the twenties, it's true. The Burnellis, the Spratt, the Fike designs. The Dyke Delta is a low aspect double delta, with the main cabin airfoil shaped. But true lifting bodies were basically unknown until the 1960's. John McPhee wrote about one of them in "The Deltoid Pumpkin Seed". The the Facetmobile is, IMHO, the most successful general aviaition true lifting body design. I agree. \ |
#27
|
|||
|
|||
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 Gerry! Look up the Stinton reference I gave you, read it over a bunch of times 'til you start getting an idea of how spacing and stagger would affect the wing placement. Then keep in mind, this is Experimental aviation! Try your idea in a large model; see how that works. But don't let the nay-sayers keep you from experimenting. There's no progress in building the same thing over and over. Your creation doesn't have to be the most efficient thing out there. All designs call for some compromises! Good experimenting! |
#28
|
|||
|
|||
questions on multi-wing planforms
"ELIPPSE" wrote in message ups.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 Gerry! Look up the Stinton reference I gave you, read it over a bunch of times 'til you start getting an idea of how spacing and stagger would affect the wing placement. Then keep in mind, this is Experimental aviation! Try your idea in a large model; see how that works. But don't let the nay-sayers keep you from experimenting. There's no progress in building the same thing over and over. Your creation doesn't have to be the most efficient thing out there. All designs call for some compromises! Good experimenting! Thanks, I haven't located that book yet, but I will. And I will on the experimenting too. Gerry |
#29
|
|||
|
|||
questions on multi-wing planforms
pTooner wrote:
"Ernest Christley" wrote in message ... 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 Go from 4 to 1. The Dyke Delta JD-2 will fold up to fit in a one car garage. And it is designed to be towed behind a car on it's own wheels; though, some have had issues with getting trailer tags to do it legally. I'm familiar with the plane, and it is reputed to be very difficult and lengthy to build. Gerry Aren't they all? 4 years and running here. Almost ready to close up the skins. -- This is by far the hardest lesson about freedom. It goes against instinct, and morality, to just sit back and watch people make mistakes. We want to help them, which means control them and their decisions, but in doing so we actually hurt them (and ourselves)." |
#30
|
|||
|
|||
questions on multi-wing planforms
flybynightkarmarepair wrote:
Various low aspect ratio designs have been flow since the twenties, it's true. The Burnellis, the Spratt, the Fike designs. The Dyke Delta is a low aspect double delta, with the main cabin airfoil shaped. But true lifting bodies were basically unknown until the 1960's. John McPhee wrote about one of them in "The Deltoid Pumpkin Seed". The the Facetmobile is, IMHO, the most successful general aviaition true lifting body design. I've heard this stated several times, and always found it a bit strange. What is it that makes the Facetmobile so successful? A single prototype that crashed, vs the Dyke Delta that has had dozens flying and about half a dozen currently airworthy. Why is the Dyke Delta not considered a lifting body design? The fuselage provides the majority of the lift at cruise, according to John Dyke and verified in XPlane (if that can be considered any sort of verification). -- This is by far the hardest lesson about freedom. It goes against instinct, and morality, to just sit back and watch people make mistakes. We want to help them, which means control them and their decisions, but in doing so we actually hurt them (and ourselves)." |
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Thrusting or Sucking (where's Howard Stern when we need him.) | Ken Kochanski (KK) | Soaring | 37 | January 14th 06 09:51 AM |
ANG Woman Wing Commander Doesn't See Herself as Pioneer, By Master Sgt. Bob Haskell | Otis Willie | Military Aviation | 0 | March 18th 04 08:40 PM |
Wing tip stalls | mat Redsell | Soaring | 5 | March 13th 04 05:07 PM |
Can someone explain wing loading? | Frederick Wilson | Home Built | 4 | September 10th 03 02:33 AM |
Wing Extensions | Jay | Home Built | 22 | July 27th 03 12:23 PM |