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#1
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Wing Extensions
Seems like it might be useful to have removable wing extensions for an
experimental. There are times when you want a fast airplane for cross country and you can stand a long runway for the high TO/landing speeds and then there are other times you want the low speed handling for short field, etc. Flaps do this to some degree depending on how exotic you want to get and have the advantage of being adjustable in flight but the wing extensions would appear to extend the flight envelope (on separate flights) beyond what can be done with typical flap configurations. A solid composite structure, perhaps 2 feet on each side that plugs into the main spar(s) would do nicely to allow you to have both a high speed clipped wing plane (when removed) and a long wing high lift plane, of course not at the same time. The further out you go on the wing the less the loads are so these wouldn't have to be built up as strong as other parts. They could be made with no control surfaces or other moving parts. You could even select a different airfoil for that section if you wanted. No problem plugging composite extensions into an aluminum main wing. Of course the main short wing would have to be built to allow access to the main spar(s). A hollow rectangular cross section spar could accept an insert to mate with removable extensions. I guess you'd need some sort of plastic overlay for the airspeed indicator to remind you of the new critial speeds. Anyone seen anything like this? |
#2
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Anyone seen anything like this?
A kitplane under design has a cruise and loiter wing. Go to www.vulcanaero.com/index.html to see it. Best Regards |
#3
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"Jay" wrote in message m... Seems like it might be useful to have removable wing extensions for an experimental. There are times when you want a fast airplane for cross country and you can stand a long runway for the high TO/landing speeds and then there are other times you want the low speed handling for short field, etc. Flaps do this to some degree depending on how exotic you want to get and have the advantage of being adjustable in flight but the wing extensions would appear to extend the flight envelope (on separate flights) beyond what can be done with typical flap configurations. A solid composite structure, perhaps 2 feet on each side that plugs into the main spar(s) would do nicely to allow you to have both a high speed clipped wing plane (when removed) and a long wing high lift plane, of course not at the same time. The further out you go on the wing the less the loads are so these wouldn't have to be built up as strong as other parts. They could be made with no control surfaces or other moving parts. You could even select a different airfoil for that section if you wanted. No problem plugging composite extensions into an aluminum main wing. Of course the main short wing would have to be built to allow access to the main spar(s). A hollow rectangular cross section spar could accept an insert to mate with removable extensions. I guess you'd need some sort of plastic overlay for the airspeed indicator to remind you of the new critial speeds. Anyone seen anything like this? Glasairs have optional wingtip extensions. They add about 5 ft to the wingspan of the airplane. http://www.newglasair.com/glasairSIIspecs.html Rick Pellicciotti |
#4
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Rick Pellicciotti wrote:
Glasairs have optional wingtip extensions. They add about 5 ft to the wingspan of the airplane. http://www.newglasair.com/glasairSIIspecs.html Rick Pellicciotti Granted that this would have been taken into account by the designer, but wouldn't this play hell with the center of lift and by extension throw off the CG? That is, it wouldn't modify the CG, just change where it SHOULD be. I'm thinking that it isn't a good idea in just any old plane. -- ----Because I can---- http://www.ernest.isa-geek.org/ ------------------------ |
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#6
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Chopping the wing will effect the center of lift for swept wing
aircraft, but most homebuilts (e.g RV) have a wing that just goes straight out, chopping wing just chops lift (and drag). And I'd have to agree, it ain't a good idea on just any old plane. First of all, you make the basic wing on the short side for your highest speed operation, then you have to expose the load bearing elements of the wing structure for your extensions to be able to couple. The structure must be able to handle the extra load from whatever longer wing extension you attach. But in the end, you have a plane with a wide operating envelope. The idea dawned on me after looking at the regular structure of an RV-8A wing I was watching being built up and comparing an aquintances shaved wing EZ that he says he needs to come over the fence at 100kts minimum but it goes real fast on a small HP motor. Ernest Christley wrote in message Granted that this would have been taken into account by the designer, but wouldn't this play hell with the center of lift and by extension throw off the CG? That is, it wouldn't modify the CG, just change where it SHOULD be. I'm thinking that it isn't a good idea in just any old plane. |
#8
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I think the poster meant that for that particular case the numbers
didn't change much. But in general, there aren't many parts of the plane that effect performance more than the wing does. Produces effectively all the lift and most of the drag. Dave Hyde wrote in message ... Roger Halstead wrote: I guess you'd need some sort of plastic overlay for the airspeed indicator to remind you of the new critial speeds. They don't change all that much. You leave them set for the shorter wing. ... I think someone else said this too, and I find it confusing. If they don't change that much, why have the extensions? Just for more fuel? The airpseed indicator could certainly be marked that way and inspectors may approve it, but it seems like the long-wing version would be more critical for safety numbers. Vne would likely be lower for the long wing(*), and maneuvering speed will be lower as well, assuming the extensions add any lift at all. Stall speed for *both* wings is important. (*) Assuming it's flutter that sets Vne, which is a big assumption. Dave 'corner speed' Hyde |
#9
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Jay wrote:
I think the poster meant that for that particular case the numbers didn't change much. But in general, there aren't many parts of the plane that effect performance more than the wing does. Produces effectively all the lift and most of the drag. I really had planned to stay out of this; but ... The wing certainly produces most of the lift on a typical (not Rutan) airplane, although the fuselage, in many common designs, contributes significant lift as well; especially at low speed and high angle of attack. However, the wing does not contribute most of the drag. Typical wings have L/D of around 100/1 for laminar and ... aarrrgh! ... I can't find my Dover Edition of "Theory of Wing Sections", but even the "rough" condition gives more than 30/1 for cruise and is still good enough to contribute less than half of the total drag at climb speed. The fuselage and engine cooling are usually the biggest contributors; with enpenage, undercarriage, antennas, and other "stuff" that sticks out of the airplane contributing lesser amounts of drag. Therefore, the probable contribution of wing extensions on most powered aircraft should be reduced climb and approach speeds and the opportunity to reduce fuel consumption in a reduced speed cruise. Assuming that the aircraft was correctly rigged for its cruising speed; then it should be than the shorter winged slower at its cruising speed version due to the nose down attitude of the fuselage as well as the related increased trim drag of the empenage. The increased drag of the larger wing should make a lesser contribution to the greater drag. Peter Dave Hyde wrote in message ... Roger Halstead wrote: I guess you'd need some sort of plastic overlay for the airspeed indicator to remind you of the new critial speeds. They don't change all that much. You leave them set for the shorter wing. ... I think someone else said this too, and I find it confusing. If they don't change that much, why have the extensions? Just for more fuel? The airpseed indicator could certainly be marked that way and inspectors may approve it, but it seems like the long-wing version would be more critical for safety numbers. Vne would likely be lower for the long wing(*), and maneuvering speed will be lower as well, assuming the extensions add any lift at all. Stall speed for *both* wings is important. (*) Assuming it's flutter that sets Vne, which is a big assumption. Dave 'corner speed' Hyde |
#10
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So if the aircraft is built with particularly short permanent wings
with facilities toi accept extensions from the start, you have the choice of an aircraft with higher cruise speed but accelerated takeoff/landing speeds, or as you mentioned in your posting, an aircraft with reduced speed on takeoff/landing, and a higher efficiency, albeit slower cruise. And of course with intermediate size extensions, you could have something in the middle, like most GA aircraft have these days- not too fast, not too slow. At a specific speed those L/D numbers may be right, but I doubt they hold for the entire range that aircraft operate in. Drag- One of the reasons I say the wing is one of the largest contributers is because similararly powered side-by-side and tandem 2 seaters have top speeds in the same range, but the frontal area of the fuselage is quite different. Gear fairing adds a couple kts. |
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