thjakits Posted March 12, 2007 Share Posted March 12, 2007 Hello all, I am new to this forum - my present "plan" is a Modified BD-4 with a Rotary Engine. However lately I keep thinking of a Long-Ez "kind of plane": I have a few questions I could not find answered in the archive: # AFAIU the Vari-Eze has a laminar mainwing section and the Long a turbulent one - consensus the Long is easier to fly (?) Did anyone ever try a Long with a scaled up Vari-section? Laminar should be better erformance/speed (?) # AFAIU one speed limit is the excessive lift on the canard at max speed - Did anyone ever try to build a trim-able canard? If one can reduce the incidence, max CL should be lower on the canard and max speed should go up (?) Please correct me anywhere I am wrong or at least point me to the right place to find the "truth" Thanx, thjakits ) Quote Link to comment Share on other sites More sharing options...
Kent Ashton Posted March 12, 2007 Share Posted March 12, 2007 Hello all, # AFAIU the Vari-Eze has a laminar mainwing section and the Long a turbulent one - consensus the Long is easier to fly (?) Did anyone ever try a Long with a scaled up Vari-section? Laminar should be better erformance/speed (?) No, AFAIK, no one has done that. # AFAIU one speed limit is the excessive lift on the canard at max speed - Did anyone ever try to build a trim-able canard? If one can reduce the incidence, max CL should be lower on the canard and max speed should go up (?) Again, no. The view is that a trimmable canard would be unstable and much more complicated to implement. Please correct me anywhere I am wrong or at least point me to the right place to find the "truth" There was a good discussion of laminar, non-turbulent, and turbulent flow in the Central States Newsletter a few years ago. The bottom line is that even the best wing will have very little laminar flow. Never more than 1/4 chord and probably a lot less. If you're lucky, you'll have mostly non-laminar, less-turbulent flow, that is, higher drag but flow mostly attached to the wing. Quote -KentCozy IV N13AM-750 hrs, Long-EZ-85 hrs and sold Link to comment Share on other sites More sharing options...
thjakits Posted March 12, 2007 Author Share Posted March 12, 2007 Thanks for the reply! My idea to build a Vari or Long is not to get a cheap and fast airplane fast, but to enjoy the building "the best/slickest/fastest" I can. I make a living flying, so this is not the concern for me.... So if laminar would bring a few kts I would try it, however the goal is not loosing any low speed properties... To the canard: Why should a trimable canard be unstable?? The canard itself is stable, isn't it?? So my rational (..which may not be rational after all ) is - If high CL at max speed is not trimmable by elevator only, why not change the incidence angle (?). IU the max CL causes a high AOA that is not trimmable by elevator any more and needs excessive stick-forces.... This would probably be a rather small amount (3-8º ??), It also can be a slow electric-motor or a long (manual) handle with little effective movement on the canard. If the canard is stable it should not become unstable by changing the incidence. To protect against "un-intended" stalls on the mainwing one could limit the aft-stick movement with application of lower incidence. So pulling aft will only generate a faster minimum speed. Increase incidence (Return Canard to original setting) and one gets the full range back.... I do understand that things get more complex here, but I wonder what the benefits regarding speed would be. Ever anyone tried a full flying canard? Best Regards, thjakits Quote Link to comment Share on other sites More sharing options...
CP Tomes Posted March 13, 2007 Share Posted March 13, 2007 Thanks for the reply! ... Ever anyone tried a full flying canard? ... Orville and Wilbur Wright? Sorry, couldn't resist. Quote Link to comment Share on other sites More sharing options...
brinesharks Posted March 17, 2007 Share Posted March 17, 2007 Thanks for the reply! My idea to build a Vari or Long is not to get a cheap and fast airplane fast, but to enjoy the building "the best/slickest/fastest" I can. I make a living flying, so this is not the concern for me.... So if laminar would bring a few kts I would try it, however the goal is not loosing any low speed properties... To the canard: Why should a trimable canard be unstable?? The canard itself is stable, isn't it?? So my rational (..which may not be rational after all ) is - If high CL at max speed is not trimmable by elevator only, why not change the incidence angle (?). IU the max CL causes a high AOA that is not trimmable by elevator any more and needs excessive stick-forces.... This would probably be a rather small amount (3-8º ??), It also can be a slow electric-motor or a long (manual) handle with little effective movement on the canard. If the canard is stable it should not become unstable by changing the incidence. To protect against "un-intended" stalls on the mainwing one could limit the aft-stick movement with application of lower incidence. So pulling aft will only generate a faster minimum speed. Increase incidence (Return Canard to original setting) and one gets the full range back.... I do understand that things get more complex here, but I wonder what the benefits regarding speed would be. Ever anyone tried a full flying canard? Best Regards, thjakits One thing that should be kept in mind is that with all-flying canards, particularly on high performance jets (Eurofighter, etc) it is theoretically possible to stall both the canard and wing. This leads to a 'deep' stall where none of the horizontal control surfaces function and therefore you cannot recover. This is avoided by stability enhancement systems which prevent the hazardous control inputs. It's a fairly unique area of aerodynamics that you are delving into... Quote Man is not as good as a black box for certain specific things however he is more flexible and reliable. He is easily maintained and can be manufactured by relatively unskilled labour. — Wing Commander H. P. Ruffell Smith, RAF, 1949. Link to comment Share on other sites More sharing options...
thjakits Posted March 17, 2007 Author Share Posted March 17, 2007 brinesharks! (How the hell did you make up this name? )) Okay, I would say to "compare" the Long with a Eurofighter is a long shot, but definitely worth bragging rights! Seriously how a definitely un-stable, supersonic, fly-by-wire fighter works is not comprehensible for a human brain (mine at least...) you look at video-clips of fly-by-wire planes you see control surfaces go any and all ways but what you would expect. E.G. Pulling back on the stick, doesn't necessarily mean the elevator goes up. What it means the "pilot would like the plane to behave as if the elevator goes up in a direct-analog /mechanical/hydraulic/electric controlled plane" Actually I saw clips of a F-18 where one elevator goes up and the other down, so there might be "aileron" mixed in there too.. Of course the idea of a movable (full flying or only incidence trim) canard is to push the top speed/reduce canard-lift induced drag. YOU CANNOT "forget" about increasing it (incidence angle) again when slowing down! I imagine there would be various ways to ensure this. Any of these ways restrict the rear travel of the joy-stick. This way you cannot pull enough "elevator" to get the wing to stall. When you increase incidence to the established angle, the stick is free again to go all the way. If you insist to fly with low incidence, all you do is go faster - well you'll find out eventually that you cannot slow down to where you are used to. In any way, this is NOT for the basic, lowtime sunday afternoon flier, but for the "experimenter" looking for the last pit of performance. If you are that kind of guy you probably use a checklist anyway... My question is more about finding numbers and devices (mechanical) to do this safely... thjakits Quote Link to comment Share on other sites More sharing options...
brinesharks Posted March 18, 2007 Share Posted March 18, 2007 brinesharks! (How the hell did you make up this name? )) Okay, I would say to "compare" the Long with a Eurofighter is a long shot, but definitely worth bragging rights! Hey - this is the "Canard" forum isn't it? I just like canards - big fan of Rutan but also like the canard in all it's forms! Also, love flying wings..... Actually I saw clips of a F-18 where one elevator goes up and the other down, so there might be "aileron" mixed in there too.. The Tornado doesn't have ailerons (has spoilers though) and uses 'tailerons' like the F-18 for roll control. Must be an awfully strong pivot... There was one story of an F18 pilot in the gulf that had one entire side of the horizontal stabiliser shot away and didn't notice until his wingman told him! The stability system is that good In any way, this is NOT for the basic, lowtime sunday afternoon flier, but for the "experimenter" looking for the last pit of performance. If you are that kind of guy you probably use a check list anyway... My question is more about finding numbers and devices (mechanical) to do this safely... thjakits Sounds great - starting with a Long Eze is probably smart. I think if you started with the initial mission profile - deciding on what you want to achieve (ie. faster cruise, lower SFC, shorter landing t/o or landing run). Then calculate L/D for various configurations and you would soon know if it's worth it. You would have to factor in the additional weight of the variable incidence mechanism(s). Be careful though, if you keep going down this logic path you might be tempted to build a flying wing! I have briefly tried to find some theoretical stuff on a variable incidence canards. I'll keep searching but you might find it becomes focused on pitch-control canard rather than lifting canards (like the Eze's). Quote Man is not as good as a black box for certain specific things however he is more flexible and reliable. He is easily maintained and can be manufactured by relatively unskilled labour. — Wing Commander H. P. Ruffell Smith, RAF, 1949. Link to comment Share on other sites More sharing options...
thjakits Posted March 18, 2007 Author Share Posted March 18, 2007 Hey Brinesharks, You are right about blackboxes and the unskilled labour thing....) Still would like to know what's a brineshark ) Actually a shark?? Flying wings eh? Which ones to you prefer? Straight wing like Fauvel, Maerske, etc. or Horten type - Horten IX is the most beautiful Flying Wing I ever saw!! Most likely you also know about Wingco and their Atlantica BWB... If you have any info of forums about Flying Wings and/or BWB let me know. What I googled up so far is not worth the time... Also 3-surface planes like the Piaggio Avanti are on my favorit list. I may be wrong, but I think the Avanti has all lifting surfaces, non pulling down like a conventional elevator. I wonder if that kind of configuration has any merrit in a 1- or 2-seater size... Long-Ez: You are right about doing the math thing first. Here is the plan: a) Find the time - sometime down the road b) Play with X-plane and aircraft-PDQ (DaVinci) c) Maybe try a RC-model (if my kids like RC....) d) See whether the BD-4 is still #1 one in a reality check e) Build the real thing Best Regards, thjakits Quote Link to comment Share on other sites More sharing options...
Jon Matcho Posted March 18, 2007 Share Posted March 18, 2007 Most likely you also know about Wingco and their Atlantica BWB...Personally, I don't know what's so exciting about a model that has proven (so far) that it doesn't fly. I wouldn't want to chase that design at this point. I may be wrong, but I think the Avanti has all lifting surfaces, non pulling down like a conventional elevator.The Avanti has a traditional elevator. The canard and the main wing provide the lift. Quote Jon Matcho Builder & Canard Zone Admin Now: Rebuilding Quickie Tri-Q200 N479E Next: Resume building a Cozy Mark IV Link to comment Share on other sites More sharing options...
thjakits Posted March 18, 2007 Author Share Posted March 18, 2007 Jon, the Atlantica "flew" a lot in X-plane. I know its in the PC, but on the other hand it is a really good tool for prototyping. Atlantica had a test-accident, because the owner/designer/testpilot gave in to pressure from the money-side and did highspeed taxi tests in too much wind. At some point the plane got airborne in a gust and because of overcontrol it came down pretty hard. Analysis actually showed that it flew better than expected - that's where the intended control inputs where too much, as they did not match with the flying qualities at this time. However that was to be tested. There is nothing wrong with the plane at this time, just has to get together again and fly - time and money. The theory - x-plane and CFD check out well.... Question is the price at the end.... Avanti: So you say the elevator always produces some downforce on the Avanti? thjakits Quote Link to comment Share on other sites More sharing options...
brinesharks Posted March 19, 2007 Share Posted March 19, 2007 The Atlantica looks great - not surprised they reduced the sweep - would have been quite inefficient at the high angle of sweep they originally had. The fins will make it a bit more predictable than a wing-only design. I wish them every success - it would be great to see flying wings gain some popularity - remember that canards were frowned upon 40 years ago! No one in their right mind would build one.... You're right about the price - outside my budget before I even start! My concern with building a pure flying wing is that no one really has a good explanation of the spin characteristics. Even though I don't intend to go about spinning my homebuilt, I would like to know that I can recover if it accidentally happens. Hey - here's a canard, three surface (or more?) prototype built back in the 1960s in Australia. It never flew but the design work was used to build the Transavia Airtruk (weird looking thing itself). It's called the Airjeep by Pallerini: http://i132.photobucket.com/albums/q37/brinesharks/DSCN0023.jpg http://i132.photobucket.com/albums/q37/brinesharks/DSCN0031.jpg http://i132.photobucket.com/albums/q37/brinesharks/DSCN0026.jpg http://i132.photobucket.com/albums/q37/brinesharks/DSCN0028.jpg Quote Man is not as good as a black box for certain specific things however he is more flexible and reliable. He is easily maintained and can be manufactured by relatively unskilled labour. — Wing Commander H. P. Ruffell Smith, RAF, 1949. Link to comment Share on other sites More sharing options...
brinesharks Posted March 19, 2007 Share Posted March 19, 2007 The Avanti has a traditional elevator. The canard and the main wing provide the lift. All three surfaces could be lifting surface depending on the CoG. Modern (conventional layout) fighters like the BAe Hawk have a rearward CoG for manoeuvrability so the horizontal stabiliser actually produces and up-force during level cruising flight. Technically the Long Eze could have a much smaller canard (and hence more 'efficient' - the wing actually picks up the slack) if the CoG were moved way back. The trouble is the aircraft would become more and more unstable as the CoG moved rearward. The main reason on the Long Eze that the CoG is so far forward (and everyone struggles with balancing it) is to produce safe 'unstallable' handling characteristics. It does mean the wing isn't flying at full efficiency though...but don't go changing a good design on my say-so! Quote Man is not as good as a black box for certain specific things however he is more flexible and reliable. He is easily maintained and can be manufactured by relatively unskilled labour. — Wing Commander H. P. Ruffell Smith, RAF, 1949. Link to comment Share on other sites More sharing options...
Jon Matcho Posted March 19, 2007 Share Posted March 19, 2007 There is nothing wrong with the plane at this time, just has to get together again and fly - time and money.Tell that to anyone who put down a deposit based on Wingco telling them they would have a kit by 2004. All three surfaces could be lifting surface depending on the CoG.Yes, true. I just don't think that's how the Avanti is setup. Quote Jon Matcho Builder & Canard Zone Admin Now: Rebuilding Quickie Tri-Q200 N479E Next: Resume building a Cozy Mark IV Link to comment Share on other sites More sharing options...
thjakits Posted March 19, 2007 Author Share Posted March 19, 2007 Jon, AFAIK there was no one who has a deposit that is not refundable.... Might be wrong though.... Brine, the Airjeep is REALLY ugly.... thjakits Quote Link to comment Share on other sites More sharing options...
mfryer Posted March 20, 2007 Share Posted March 20, 2007 I want one (airjeep). Then of course I would like any airplane at this point. Still I think it's pretty cool. Quote Link to comment Share on other sites More sharing options...
windscout Posted March 20, 2007 Share Posted March 20, 2007 Thanks for the reply! My idea to build a Vari or Long is not to get a cheap and fast airplane fast, but to enjoy the building "the best/slickest/fastest" I can. I make a living flying, so this is not the concern for me.... So if laminar would bring a few kts I would try it, however the goal is not loosing any low speed properties... To the canard: Why should a trimable canard be unstable?? The canard itself is stable, isn't it?? So my rational (..which may not be rational after all ) is - If high CL at max speed is not trimmable by elevator only, why not change the incidence angle (?). IU the max CL causes a high AOA that is not trimmable by elevator any more and needs excessive stick-forces.... This would probably be a rather small amount (3-8º ??), It also can be a slow electric-motor or a long (manual) handle with little effective movement on the canard. If the canard is stable it should not become unstable by changing the incidence. To protect against "un-intended" stalls on the mainwing one could limit the aft-stick movement with application of lower incidence. So pulling aft will only generate a faster minimum speed. Increase incidence (Return Canard to original setting) and one gets the full range back.... I do understand that things get more complex here, but I wonder what the benefits regarding speed would be. Ever anyone tried a full flying canard? Best Regards, thjakits Hi, very interesting, i am thinking about this for some time, and did not find a reason yet on why a canard or flaps on the main wing should not be possible, given that the canard could be equiped with a trim. I understand that this would require a compensation, which I would expect can be adressed by a controller or auto-pilot. Thinking back to the time I was still flying gliders, it is not unusual that some pitch is required when using the airbrakes or flaps in the final, and it is not of any concern. What would be so different with a canard-plane? I am very well missing something, any thoughts? Regards Quote Link to comment Share on other sites More sharing options...
Drew Swenson Posted March 20, 2007 Share Posted March 20, 2007 There is a balancing act between the canard and main wing. The idea is for the canard to always stall first (whether this is a normal stall, accelerated stall, or even a dynamic overshoot). Adding flaps to the main wing upsets this balance and can (will) cause the main wing to stall first (which is virtually unrecoverable) unless something is also changed on the canard. The Starship compensated with a sweeping canard. Before chasing some of these cool ideas, make sure you define what it is that you are actually trying to accomplish. If you want to go faster, many have made great strides in cooling drag reduction over overal drag reduction to really get the speed up. Others have done real well at keeping the weight down. Adding all the toys and gizmos will keep you from going real fast. Designing your own plane is a worthy goal if you know what you are doing. Just keep in mind that just making a few changes here and there can add years to your construction time. When I blew my O235 in my Longez, it would have taken me a weekend to hang a new O235 back on. Since I decided to hang an O320 instead, it took me about 8 months (modified engine mount, new extrusions, brake cyls up front, new brakelines, all new plumbing and connections on the engine, all new baffles for downdraft cooling, new cowls, special cooling to the oil cooler...etc). In the whole scheme of things, this was fairly simple---but took a long time. I can say that most of the time was spent looking at each individual problem and trying to figure out the next step. However, everytime I was following the plans, thing went real fast----just mindlessly follow the directions. I think that a normal person can build a canard aircraft in around 2000 to 2500 hours. Significantly deviating from the plans can easily double or triple this. Ask people on the board on what it takes to "easily" widen the Cozy fuselage... :>) Quote Link to comment Share on other sites More sharing options...
windscout Posted March 21, 2007 Share Posted March 21, 2007 Hi Drew, Just thinking about the difference of a standart 15m glider and a 15m glider with flaps, in particular at higher speeds, made me wunder if I did not realize something fundamental. Those flaps make a big difference in performance at higher speeds. It is my understanding, that the big advantage of the canard design aerodynamically is the low wetted area, which is reducing drag. Not having the possibility to change the airfoil shape during flight is giving up some of this advantage. But I see your point, that there may be many other ways to which are simpler to get higher speeds. However flaps could eventially at the same time increase lift during takeoff and so get the plane airborne sooner. unfortunately, I am not yet a canard builder and can not start the process in the near future, but I did built extencively model planse in the past and did work some time in a glider repair shop. I hope to get on a project some day. At this point in time, I am in the stage of trying to better understand why certain things are not being done or not, knowing that if I do not see a reason for something does not mean that it is necessarily a wise thing to do... Thanks for your thoughts Quote Link to comment Share on other sites More sharing options...
Drew Swenson Posted March 21, 2007 Share Posted March 21, 2007 Much of what you see on the Longez is elegant by being simple. It is a very clean aircraft---and many are making cleaner by doing all kinds of aero mods. Flaps on an EZ really complicate matters for a variety of reasons. At least you have a speedbrake and opposing rudders that can be used to increase your rate of descent for an approach. When Rutan started on the Varieze prototype, it had no movable surfaces on the wings at all (except for the rudders). This was in an attempt to reduce the complexity of building the wings with ailerons and putting all the control mechanisms in place to make them work. In the end, he did not get the control harmony he was looking for----and ailerons went on. The original Longez had a rudder up front---did not need a complex mechanism to go all the way out to the wing tips----and made them easier to build. In the end, it was not what he wanted---and actually made it work in the Defiant. Rutan always wanted people to build light. Day, VFR only---make it as simple as possible. And I can tell you that a light longez flies much better than a heavier one. Mine was heavier though---bigger engine, night, IFR, etc---but I traded off flying qualities to get those extra things. One last thing---if you want to get a plane built and up in the air fast----follow the plans. If you are more interested in building than flying, then it does not really matter. Also be very aware of why you want to take a simple design and make it more complicated. For example, if your desire is to get into short, unprepared fields, a Canard is not really for you. All the EZ aircraft really fall in the high speed, cross country category----operating from prepared fields of around 3000 ft (2000 ft in a Longez if you are experienced). It is not a good acro airplane----there are many other designs that do this much better. Quote Link to comment Share on other sites More sharing options...
brinesharks Posted March 23, 2007 Share Posted March 23, 2007 Brine, the Airjeep is REALLY ugly.... thjakits Yup - a case of function over form! It was apparently designed for agricultural work (don't know if that means spraying) - would have had an exceptionally short take off run with all those lifting surfaces. The undercarriage is the trailing link type so it would have coped well with outback airstrips. Unfortunately I think people would still tease you about how ugly your plane is... Quote Man is not as good as a black box for certain specific things however he is more flexible and reliable. He is easily maintained and can be manufactured by relatively unskilled labour. — Wing Commander H. P. Ruffell Smith, RAF, 1949. Link to comment Share on other sites More sharing options...
brinesharks Posted March 23, 2007 Share Posted March 23, 2007 Hi, very interesting, i am thinking about this for some time, and did not find a reason yet on why a canard or flaps on the main wing should not be possible, given that the canard could be equipped with a trim. I understand that this would require a compensation, which I would expect can be addressed by a controller or auto-pilot. Thinking back to the time I was still flying gliders, it is not unusual that some pitch is required when using the air brakes or flaps in the final, and it is not of any concern. What would be so different with a canard-plane? I am very well missing something, any thoughts? Regards From my understanding, the main concern with adding flaps to a canard with such a forward CoG is that the flaps will produce an unacceptable pitch change (nose down?). This occurs because the moment is so long between the CoG and the Wing TE. A belly board style air brake might work if you just want to increase drag on finals/landing.... As for speed - the weight of the aircraft determines maximum potential speed. The drag affects how close you get to this potential speed. So, build light and make it 'smooth'. That's why just adding a bigger engine doesn't necessarily work - the added weight can negate any real benefit of more thrust. Think 'light is right' Quote Man is not as good as a black box for certain specific things however he is more flexible and reliable. He is easily maintained and can be manufactured by relatively unskilled labour. — Wing Commander H. P. Ruffell Smith, RAF, 1949. Link to comment Share on other sites More sharing options...
Jon Matcho Posted March 23, 2007 Share Posted March 23, 2007 A belly board style air brake might work if you just want to increase drag on finals/landing....I hope so, because that's what's in the plans (although I think the 'landing/speed brake' was not in the original Long-EZ plans, but I could be mistaken). Quote Jon Matcho Builder & Canard Zone Admin Now: Rebuilding Quickie Tri-Q200 N479E Next: Resume building a Cozy Mark IV Link to comment Share on other sites More sharing options...
Drew Swenson Posted March 24, 2007 Share Posted March 24, 2007 I found that I really needed a speedbrake in the Longez to make a good landing at a reasonable approach angle. I rarely use the speedbrake in the Cozy. Without going into the equations, you need a lot of extra horsepower to get a relatively small change in extra airspeed. In short, if you double the airspeed, you quadrouple the drag, and you need to up the power by 8. The harder you push, the harder the air pushes back. Cleaning up the plane can have drastic effects. And of course adding lots of power and cleaning up the plane does wonders too. No matter what, extra power will get you off the runway sooner, let you climb a lot faster, and let you cruise at a higher altitude. The weight of the plane also changes the way the plane feels. With 2 people and lots of gas, the Longez felt like a truck. But thats ok. Usually when I had 2 people and lots of gas, I was usually going somewhere. By myself and with a light load of gas, the aircraft totally handled differently---like a little fighter. Quote Link to comment Share on other sites More sharing options...
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