Re: New Carbon Spar Manufacturing ???

One Sky Dog


I am not sure if they did any analysis of the total structure of the carbon spar and the glass shell of the canard. I think they did some calculations on the spar but not the combination.

My concern is mismatched modulus of elasticity“I” and moment of inertia geometry. That combination ; spar = high modulus * small “I” (coupled with) shell= low modulus * big “I”, is not ideal in my opinion. I suspect it has a lot to do with upper surface mid span dimples and skin separation.

By the way when I worked for the Air Force one of the exercises we had the students build was a 3” X 3” I-beam 30” long using AS4 fiber and 250 F cure epoxy. Final part of exercise was to break them in a 4 point bend fixture. Breaking loads of 5,000 to 12,000 lbs depending on layup.


Charlie Johnson

On Sep 3, 2019, at 4:18 PM, 'Jay Scheevel SGT' jay@... [Q-LIST] <Q-LIST@...> wrote:

Not sure if it was just a sales ploy on the part of QAC, but they claimed that the airfoil was too thin to support the landing loads using any of the typical spar construction methods of the time. Not sure they ever really validated that by modeling or testing, or if they just went ahead a built the tubular spar and tested that only.


In any case, the GU airfoil causes the wing to be quite a bit thicker. The thicker the profile, the lower the loads on the traditional I beam shear web and spar caps.


The thin LS-1 airfoil would probably double the loads on the spar caps under the same loading conditions as the GU, so the I-beam construction would have to be beefed up substantially .  


I would not suggest building that way without first doing the mechanical modeling. That said, there are people who monitor this list who are perfectly capable of doing those models.





From: Q-LIST@... <Q-LIST@...>
Sent: Tuesday, September 03, 2019 3:33 PM
To: Q-LIST@...
Subject: Re: [Q-LIST] Re: New Carbon Spar Manufacturing ???



 Regarding canard building. The Dragonfly  has a built in place spar
with glass and carbon fiber.  Not complicated and easy to built. I think
there are a set of plans on the internet somewhere.  That's how Kimbal
from Calgary built his inboard gear canard for his Q2.

One more thing. I put up another video of the Dragonfly "stall" with
power of and full power on. The shackyness is the camera and not the
airframe.    "dragonfly stall 2019"---------  Take care-----------  Chris

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