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Mar 22, 2021, 04:40 AM
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I think a lot of the written things are right on, but I also think that you should stiffen the wing spanwise by adding a carbon strip on top and on the bottom and make dihedral 0. Flex spanwise means also twist on a swept back wing, which can cancel out the aileron respons also it could promote torsional flex that cancels out the lift force the ailerons should produce. To concour that you can make the spar with less sweep than the wing, so from 45% at the root almost to the tip of the wing. Another thing is are the servos strong enough? Flaps of this size need quite a lot of power to move the flaps.
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Mar 22, 2021, 05:20 AM
Living the dream
KiwiKid's Avatar
Bit late to the party on this one and the issues have been very well assessed. Stiffness, tight linkages and good elevon authority are the key - carbon is your friend.
Best bet with the aileron/flap set up you have is to do a mix so you can have them work full span controlled by a switch. I have this set up on my "tiddler" 3.2m EPP wing, but it should work well on your larger wing. Mine was a noodle until I fitted carbon for Africa and it performs very well as a sloper and (with motor tacked on the snoz) as a parkflyer.
Here's a parkflyer vid.

(2 min 16 sec)
Mar 22, 2021, 12:45 PM
Flagstaff, AZ
dawsonh's Avatar

It is always great to hear your analysis. I have “fond” memories of how “well” my Halfpipe flew after its tail got knocked over or worse knocked off... and of course I mean that it could not fly at all. The same issue with the Moth and M-60 planks. They surly did not know which end was “front.”

On the other hand a chevron wing will fly (albeit poorly) with small or no winglets. The wing sweep does induce directional stability. However as we learned in the combat world, bigger winglets improved maneuverability and helped regain control more quickly after a stall inducing hit.

I wonder how a big center fin would work in this big boy?

Mar 23, 2021, 02:16 AM
Registered User
mike_o's Avatar
Originally Posted by dawsonh
...I wonder how a big center fin would work in this big boy?..
While the main problem seems to be lack of torsional rigidity, a better vertical stabilizer is good for most wings. This one has a very moderate sweep, so the winglets don't have the normal benefit (over a central, rear fin/stabilizer) of a much longer moment arm. The effect of a vertical stabilizer is a product of the moment arm and the size - doubling the size has the "same" effect as doubling the distance from the aerodynamical center.

So a large and long central vertical stabilizer/fin would most likely improve yaw stability, but it won't fix the real problem.

I have used the extended, central stabilizer on a few designs, and it works well. With the added benefit of no winglets catching something in the car's rear seat when loading and unloading

Modded, FPV Scout Bee

Video here
Last edited by mike_o; Mar 24, 2021 at 03:19 PM.

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