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How to design a low drag low lift airfoil section for struts and wheel fairings.

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MadRocketScientist

Well-Known Member
Joined
May 16, 2009
Messages
1,778
Location
Canterbury, New Zealand, Earth, Milky Way Galaxy.
Not sure what section this needs to go into, I think its in the correct one, maybe we need an aerodynamics section of the forums (or not:ponder:;)).

There might be someone on here that can help me out (Orion comes to mind, hint hint:gig::gig:)
What I need is info on how to go about designing low drag/low lift airfoil sections. I have two basic requirements. I am reworking the wheel fairings and strut fairings on the CriCri I am currently building. I don't have molds for any of these parts yet but intend to make them using my CNC router. The plans show a fairly crude foil section for these parts and little or no consideration of intersection drag. I COULD just use the foils shown in the plans but I would really like to get a decrease of drag for a 'little' extra effort. Even the wing foil section with no camber would improve the fairings. I am also going to align the fairings with the localized flow as much as possible.

I have been searching the internet for quite a while looking for a low lift AND low drag airfoil but no success. The section is not required to generate lift at any aircraft AOA, low drag is the goal. There is a huge amount of info on high lift/low drag airfoils but next to nothing on low lift/ low drag. I guess aerodynamic efficiency has only been a priority on GA aircraft recently if at all;);):gig:. I have been looking at laminar flow sections similar to the picture below. The main problem that I have is that the lower drag sections tend to stall at lower angles of attack. I think a larger nose radius but with the laminar flow ramping on the front half of the foil would be a better option.

The wheel fairings will be slightly different in that the fairing is more bullet shaped and there is a 3D flow over the surface so may require a different technique. I have noticed that the reno racers tend to have a flat vertical trailing edge on the fairings. I presume this is to allow for operation at differing angles of attack in the air but still maintain laminar flow over much of the fairing. I emailed Mike Arnold about the airfoil section for his wheel fairings on the AR-5 and he just eyeballed them. I can possibly do the same but seems to be a rough solution with all these computers and CNC machinery around.

Maybe building a wind tunnel is in order:gig::gig::gig:

Thanks in advance,

Shannon.
 

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