Thomas Cunningham said:
>This is directed mostly to Joe, but, feel free to jump in!
>
>I am looking to do another physics class and I am looking through what you
>did of course. My lift coefficient function needs an angle of attack in
>degrees to work on. I just looked at the routine you used and more
>specifically, the data it produces. Your angle of attack doubles are between
>zero and one. Can you give me some help to get more meaningful figures, like
>zero to 18 degrees or so?
Could you share your lift coefficient function? I've been looking for
one that doesn't require a wind tunnel to figure out and haven't had a
whole lot of luck. There are a couple others, but they seem needlessly
complex, or depend on hard- to- figure values.
>The formula's I would like to use, rely on other data for the Hellcat,
>aspect ratio, wing area, taper, etc. I would like to create a more general
>class that encompasses these other properties. Basically, I'm looking to
>place the items you have listed in Hellcat stats in to a more formal class
>structure. I would also like this to be able to read in the stats from other
>planes later. Can you give me some idea of how this would best be done,
>assuming you think this is a good idea?
>
>When it comes to projects like this, my nonprofessional/hobbyist programmer
>status really bites me in the butt when it comes to these types of design
>issues. Appreciate your input.
>
>Thomas C.
I'm also working on a physics model, but some of the math is kicking my
butt. That, plus my time is more limited than I would like right now...
However, I'd like to point a few things out and maybe someone (Joe?)
could apply them to the model.
A Hellcat has a wing area of 102 m^2, not the 10 m^2 the model currently
uses. This is really going to improve the lift characteristics of the
plane, but I have a feeling the thrust factor (10,000 newtons) is a
little too generous -- it may all work out in the end, though.
The plane's mass is guesstimated at 5000 kg, but the F6F has an empty
weight of 4190 kg -- leaving us with only 810 kg for fuel and weaponry.
It would be better to boost it to 6990 kg; the Hellcat's maximum take off
weight.
In the drag force equation:
drag force = .5 * (air density) * (true airspeed)^2 * (Coefficient of
drag) * area
Area is most commonly expressed as the wing's area, not the frontal area
of the aircraft. You can use a plane's frontal area to determine drag
force, but since we're using the airfoil's (wing's) area to determine
Coefficient of Lift (Cl), we should use the same area to determine drag.
Both lift and drag are aerodynamic forces, and since drag is a direct
result of lift I think it makes sense to tie both of these together. At
least, that's what LisauskasPhysics will do. :-)
Also, the Coefficient of Drag (Cd) is not a constant. It, like the Cl,
varies depending on the Angle of Attack of the airfoil. If a proper
chart can be found we can build up an array for Cd like Joe did for the
Cl method, but it'll take a bit of digging. It should certainly be
easier than having to compute Cd every cycle...
I'm very excited about this project and hope to contribute more than just
snipes at Joe's hard work. I think I'll even have to come off digest
mode. :-)
Tim
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