Re: Hi! I'm a new member and want to build a Q-200... probably from scratch

David J. Gall

Regarding the Weishaar-Doyle LS-1 canard I can only say that they were successful. They designed it as a taildragger canard and only converted to tri-gear when they had directional control difficulties as a taildragger, not because of any structural deficiency. The documents in the Files section are all that were published. I would not build from the template file "Weishaar-Doyle LS-1 Canard Plans Templates.jpg" (in the Files section) because it has known, measured distortion from the scan process that renders it unacceptable. However, there is enough information in that image and elsewhere that someone could redraw those templates using available NASA data for the airfoil section and the dimensions available on that scanned image. Note that the Weishaar-Doyle LS-1 canard elevators were designed using the then-popular idea (thanks to NASA) that the control surfaces should be thicker than the wing immediately ahead of them; the Weishaar-Doyle elevators are drawn 10% thicker than the wing. The QAC LS-1 canard did not have that feature and seems none the worse off for it. I would suggest that anyone building a Weishaar-Doyle LS-1 canard eliminate that silliness and just make the elevators the same thickness as the wing ahead, just like QAC did. Either way, the Weishaar-Doyle LS-1 canard elevator will absolutely require the use of "sparrow strainer" trim tabs just like the QAC LS-1 canard elevator does. The details of mounting the Weishaar-Doyle LS-1 canard should be similar to those of mounting the QAC GU canard, including a horizontally "flat" center section like the GU canard. Some details missing from the Weishaar-Doyle LS-1 canard plans are the BL-19 and BL-91 elevator jigging templates. If one were to build the "fat" 10%-thickened elevators one would need to develop their own versions of these elevator jigging templates; otherwise, the QAC versions would suffice.

I have never seen the alleged "Waddelow canard plans" despite making numerous requests. I have seen the Q-Talk back issues and read Mark Waddelow's contributions there -- I do not recall seeing any mention of a separate "Waddelow canard" or plans that he might have published, although he did offer to send out some additional "details" regarding one of his articles to those interested who might request them of him. I have not seen those "details." I will not wade into the Waddelow canard discussion or the "build it without the spar" discussion except to say that anyone who builds any canard "without a spar" because it's "for a Tri-Q" under the assumption that the spar can be "left out" due to "flight loads being less than landing loads (as a taildragger)" is a FOOL. Any engineer anywhere can pull out a copy of Roark's "Formulas for Stress and Strain" (a standard engineering desk reference book) and easily show that the bending moment at the canard root under 4-g loading in flight is approximately equal to the bending moment at the canard root of the wingtip-mounted landing gear under normal landing conditions. In other words: the spar is just as much needed for flight loads on a Tri-Q as it is for landing loads (and flight loads) on a taildragger Q-200. This persistent, incorrect argument that the spar is "not needed" for a Tri-Q is why I will NEVER* accept an offer of a ride in a Tri-Q.

Were I building a Q-200 from scratch, I think that I would use the Roncz "new canard airfoil" that the Long-EZ uses instead of the LS-1 airfoil....

*[Edit] Now that I have seen the Waddelow canard plans and layup schedule, I retract my "NEVER" declaration. The Waddelow canard appears to be well-designed and the engineering appears to be adequate and conservative.

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