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-   -   Experiment with a new shape of Airfoil for my glider (https://www.wattflyer.com/forums/showthread.php?t=79531)

aaindthu 09-16-2018 07:16 AM

Experiment with a new shape of Airfoil for my glider
 
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I am building an RC glider. It's under construction. I came up with an idea of a sharp leading edge airfoil for that glider.
Attachment 186951
This type of airfoils are typically used at supersonic speeds. But to achieve a higher lift to drag ratio, I thought of this symmetric airfoil with sharp leading edge for gliders.

I conducted a small experiment with two chuck gliders. Both identical in dimensions. But one glider having a rounded leading edge and the other having a sharp leading edge. Both being symmetrical.

The sharp leading edge airfoil, due to its less drag kept flying straight, like an arrow everytime I launched it. Here is the video of my experiment.



Now I am going to built a wing with this type of airfoil for my RC glider.

quorneng 10-01-2018 10:23 PM

aaindthu
It good to experiment but I am not sure the test was really rigorous enough to confirm that the sharp edged aerofoil was actually better.
For instance are you sure the fact that one flew straight and the other didn't was not due to small differences in the wings?
A sharp edged wing is indeed likely to create less drag than a conventional one when it is generating no lift but the drag will rise more rapidly than the conventional one when it is set at an angle to the airflow necessary to generate lift.
Just keep experimenting!

CHELLIE 10-02-2018 07:12 AM

it will work, but its not for a slow flying glider, if your plane was going to fly at Mach 2 then it would be ok :) LOL

solentlife 10-02-2018 07:21 AM

There is one inherent problem with sharp LE ... critical angle to airflow.

As Q mentions - there is a sharp change in its ability to sustain lift.

It is actually not correct to say a fast aircraft has a sharp LE ........ what is true is that such aircraft have a THIN wing .... the old EE Lightning is a prime example of this. BUT they still had ROUNDED LE for very good reason.

As the wing angle of attack changes - the LE presents a different attitude to the oncoming airflow. If its rounded - the airflow will remain good for a reasonable change of angle, but make that LE sharp - a small change in angle of attack and now you have a turbulent disrupted airflow.

The sharp entry would only benefit 'maybe' in perfectly straight level flight with no requirement to pitch up / down.

Its actually a phenomenon we see with flat plate wings when you don't sand a rounded LE.

Nigel


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