AboutPaul Soderman Expertise Aeronautics, Fluid Mechanics, Aeroacoustics, Noise Control, Muffler Design, Wind Tunnel Research.... I know nothing about India - do not ask about schools, jobs, application requirements, career choices, etc. for India. Please, no text message verbiage; I prefer full words in full sentences. Thanks.
Experience 38 years as research engineer at NASA
Publications AIAA, NASA
Education/Credentials B.S. and M.S. Aeronautical Engineering - U. of Washington
Graduate work Standford U.
Awards and Honors AIAA Associate Fellow (American Institute of Aeronautics and Astronautics)
Question QUESTION: Hi Paul!
Iam a student (product design, not engineering). I have a school project for
which I am designing a second pair of wings for a Cessna Aircraft. The
concept is that the wings can be deployed and retracted, when needed. When
retracted they are on a roll similar to a carpenters tape measure, but when
extended , regain their curvature and strength.
The added wings will not be large (4feet long x 1.5 feet wide). I still have to
decide on the best thickness and also the radius around which they should
rotate.Any advice?
The initial obvious material to think about was spring temper steel. However
the weight penalty will be large, so I shifted to Composites or light metal
alloys. Any suggestions on this one?
I am aware that many calculations and testings are required if any such
product would be produced for real, however this is just a school project and
it would be great if you as an expert can tell me whether such a concept has
a potential to be made workable. Thanx a lot :)
ANSWER: Sofia
I have heard of detachable wings and folding wings, but never rolled-up wings. I wonder how you can get the necessary strength when deployed. After all, the weight of the aircraft is almost entirely held by the wings. Usually, a wing has a spar or strongback to carry the load. How to roll that up is the challenge.
As to thickness, first you need to find the necessary wing area which can be found from: L = W = cl rho V^2 S, where
L = lift
W = weight (steady flight)
cl = lift coefficient
rho = air density
V = airspeed
S = wing area
Then you can compute span and chord. Once you know chord you can choose any reasonable airfoil and get thickness. Check the following website for details: http://sites.google.com/site/aerodynamics4students/table-of-contents
Paul
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QUESTION: Paul thanx for the info you gave me - I will check it all out !!!
I know the concept is new - thats why I need help with it - smiling :)
Regarding having the strength when deployed, the wings should be
manufactured with a curvature similar to the carpenters tape measure, so
when rolled up they are flat but when deployed they immediately regain their
curvature, which is what makes them strong. This was my idea of how to
keep them strong without support structure. What is your opinion on this? Of
course what material I choose or length, with and thickness of wing will play
a big role. Plz let me know what your opinion is on this and if you have any
suggestions for a material with good spring properties like spring temper
steel but light in weight. Thanx a lot :)
Answer Sofia
You are correct, a tape measure gets extra strength from the curvature of its cross section. But there are limits, a tape measure will break when loaded too much. So you also need thickness and width. Once you do that it becomes difficult to roll. When you study structural analysis in your future life, you will find that strength of a beam can be predicted based on its composition and shape. But without the fundamental knowledge of beam analysis, you are kind of whistling in the dark. There is no magic material that can make up for inadequate beam cross section. Beam cross section depends on load, which I haven't heard you mention yet, beam length, factor of safety, and a few other things that go into engineering analysis.
Spring steel is actually very good material. So is aluminum. I can't recommend anything better without knowing more about the design.
Paul
