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#11
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I've got to disagree with your assertion that canards are good for
range. I worked on the Voyager, Starship, Triumph, Catbird, ATTT, Ares and JetCruzer, plus I've analyzed the VariViggen, VariEze, Long EZ, Solitaire, Defiant, Predator, Quickie, Q2 and Dragonfly post-facto. To get long range, you want to fly at a speed slower than maximum, near or at the best L/D point. This involves flying at a higher lift coefficient and the induced drag becomes more important here. To get low induced drag, you need the sum of all lifting surfaces to have an elliptical lift distribution. The canard will by itself be nearly elliptically loaded. The aft wing, of greater span, will then need a hole in its lift distribution inboard to accomodate the canard's loading. This means that the inboard aft wing will be carrying little, if any, loading. However, it will physically be there, causing profile drag - a horse that is eating, but not pulling. Even worse, on a canard, you want the fuel on the CG, so as it is used, the CG won't shift. This means real big strakes on the aft wing usually. Thus, the part of the wing contributing profile drag, but no lift, gets even bigger. For a given L, the D has now been forced to get much bigger, clobbering L/D. The induced drag efficiency ("e") of the Voyager was around .5, as opposed to .75-.8 on conventional configurations. Simply put, the Voyager could have gone around the world with less fuel if it had been conventionally configured. The reason that the Voyager is in the Smithsonian is that Dick, Jeana, Burt and the rest of the crew created an airplane and performed a mission that no one had ever performed, plus many had dreamed of. Yes, the Long EZ has good range. However, a conventionally configured aircraft of the same GW, with the same engine and fuel quantity would have longer range. For the same L, the D would be lower. |
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