Earthstar Forums

Older references say NACA 0033 is the best airfoil for fairings, and that airfoil can produce less than 1/2 the coefficient of drag versus other fairing airfoils. (low wetted area, and relatively insensitive to angle of attack)

Couldn't find coordinates for the airfoil, but finally found a site that would draw any 4 digit NACA airfoil:

http://www.desktop.aero/appliedaero/air ... metry.html

I did a screen cut and paste, but have no idea whether that is accurate or not.

I found a formula on Wikipedia, but it looked ugly.
http://en.wikipedia.org/wiki/NACA_airfoil

I also found the Cri Cri designer looking for laminar flow fairings but found no answers.

Anybody?

>From the UIUC Airfoil Database - try this one, the Eppler E862:

http://www.ae.illinois.edu/m-selig/ads/afplots/e862.gif

http://www.ae.illinois.edu/m-selig/ads/ ... abase.html

Chris

Question for the group.
I wanted to design the most drag free strut fairings possible.
In all my research on the web I kept coming up with the teardrop shape as being the most areodynamic shape with the least amount of drag.
The wind tunnel tests (from the articles I read) said that the leading edge is a circle and the tail of the tear drop shape is a ratio of diameter x 3 for total length of the tear drop fairing.
Most fairings I see produced are more pointed at the leading edge (which the articles said ) increases drag by increasing the wetting area to the air stream. Yes they look more sexy and are easier to manufacture but do they produce more drag than the true teardrop shape?
Any one up on this?
Thanks
Fred
I assume that for suppersonic jets the teardrop shape at those speeds are a different set of rules.

Fred,

The gear strut fairing on the Gull 2000 looks pretty good to me, and all I have to do is install wheel pants with a home made fairing over the brake area. My friend did that on his wheel pants, and it looks really good. I'll post a picture on my Gull folder. Look at the last picture and see what he has done.

kb

Hi Kess
They look awesome. It really changes the whole look of your Gull.
It looks like a "serious business aircraft", if you know what I mean.
Be sure to get that monster spinner mounted also.
You should take it to Oshkosh some day (when you are really finished) for judging.
Fred

In a message dated 2/23/2011 6:18:15 AM Pacific Standard Time,
gayford@golden.net writes:

Question for the group.
I wanted to design the most drag free strut fairings possible.
In all my research on the web I kept coming up with the teardrop shape as
being the most areodynamic shape with the least amount of drag.
The wind tunnel tests (from the articles I read) said that the leading
edge is a circle and the tail of the tear drop shape is a ratio of diameter x
3 for total length of the tear drop fairing.
Most fairings I see produced are more pointed at the leading edge (which
the articles said ) increases drag by increasing the wetting area to the air
stream. Yes they look more sexy and are easier to manufacture but do they
produce more drag than the true teardrop shape?
Any one up on this?
Thanks
Fred
I assume that for suppersonic jets the teardrop shape at those speeds are
a different set of rules.




Hi
The tear drop is the result of the Mass of water that is held in an
electrostatic field while falling through the air, the air molds the water in to
the shape of least resistance divided by the water masses tendency to form
in front, the tail forms because of the rolling of the turbulence caused by
the bluff body presenting itself to the wind witch causes the pinched
shape. it is one of those wives tails that sticks with the people that haven't
looked at wind tunnel data. On the other hand the strut farings that you see
on the certified airplanes have ben tested in wind tunnels and tuft
tested. There is always room for improvement since an airplane design is the
result of the compromises and knowledge at the time the lane was designed. The
solution to any problem only comes to the one that is open minded enough to
allow him or her self to see it. and not to rely on data that was based on
over simplifications.
Happy Flying
Mark

Hi Mark
Thanks for the explanation. Could you dummy it down a bit for me.
So are you saying that the tear drop shape isn't the most aerodynamic shape, and it is an assumed wives tail sort of thing?
If so, what would the best shape look like?
Thanks
Fred

There is a bunch of good/free info available in the AR-5 articles about how he makes them go fast and I found how he disigned the gear fairings interesting.
Here is a link to one of many.

http://ar-5.com/condrag94.html

Loren

In a message dated 2/24/2011 5:45:00 AM Pacific Standard Time,
gayford@golden.net writes:

Hi Mark
Thanks for the explanation. Could you dummy it down a bit for me.
So are you saying that the tear drop shape isn't the most aerodynamic
shape, and it is an assumed wives tail sort of thing?
If so, what would the best shape look like?
Thanks
Fred




Hi Fred
The best shape for a faring is related to the mass flow in the area and the
interactions of that mass flow with the surrounding surfaces and the wakes
that are produced there by.
I would look at other aircraft that are fast and see how they do it and
than analyze there method till you figure out what they are thinking. Than you
can apply that thinking to your needs. than tape tufts to your faring and
tape a camera to the airplane and fly wile taking video and study the video
to see were the problem areas are and fix them. It is also important to
document your true air speed first and than you can se what gains if any you
are getting from your experiment. just remember that one measurement is not
enough, fly at least 5 test flights under the same conditions, or as close
to the same conditions as you can get. Than average the results.
The tear drop is not the most aerodynamic shape, that is why you don't see
it on modern airplanes. The wing airfoil is proven to be many times better.
Happy Flying
Mark

Fred,
The monster spinner is mounted, and I posted pictures of it called spinner trial. It needs paint and some filling but otherwise fits fine, and it does make the plane look bigger that it is when I'm out in the run-up area with the other experimentals and GA's.

kb