|  | Join Date: Mar 2003 | Location: Western Washington | Posts: 3,964 |  |
April 8th, 2007, 12:50 PM
Re: Rutan Defiant canard question.
Not much historical or technical data exists in connection with the Defiant. The answer to your question could be as simple as that which you guessed at (nose engine) or it could be more complex.
Given the size of the airplane and the capacity it was to have, the variable payload was a bit further ahead of the main wing than what you see in airplanes like the Cozy or the Ezes. To maintain balance and reasonable performance, the configuration would therefore need a larger canard in order to maintain stall speeds and control authority. (BTW canards don't rally have a "deep stall" region)
Simply said though, the sizing and proportion of the surfaces is most likely the result of a combination of factors that are similar to those used in sizing the wing and tail of a conventional aircraft.
In designing your own, using proportion as found on another, similar aircraft is OK only as long as you understand that that "guess" has to be just that, a guess. This is especially the case in an airplane where you're considering going to two engines. The sizing based on load distribution is only the first order consideration based on a static assumption. You must then also account for the second order issues, which may be a function more of the dynamic factors like maneuvering and momentum.
In short, in designing a new airplane it is a good idea to approach it as from scratch, even if it is based on an existing design.
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