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Old 11-30-2002 | 12:00 AM
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BMatthews
 
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From: Chilliwack, BC, CANADA
Default fuselage aerodynamics

Originally posted by ptxman


Here is a link
http://www.dreesecode.com/

....
So now if I input the coordinates for 2 'airfoils' which just so happen to look like a fuse side view & again assume the span (fuse width) is the same in both cases, isnt there some information to be learned?

I seriously doubt it. The fuselage is basically acting as two very short wingtips with no actual wing between them. In other words there is just no two dimensional flow here to analyse. Sure, you'll get numbers but they won't mean anything that you can actually use.

From reports I've read in the past about sailplanes there IS some benifit to using airfoil profiles for the nose back to the mid point or so of the wing. After that it just becomes too turbulent to really matter. You want to pick an airfoil that offers a high point at the leading edge of the wing and then flow the rear curves into the boom. If you can determine the upwash and down wash angles AT THE SPEED OF MAXIMUM IMPORTANCE and align the nose and tail boom with these then you'll gain a slight benifit at that one speed. This is why F3B models don't really have swoopy fuselage designs, the speed runs are all important so they set them up for that region of flight. The same report also said that there would only be laminar flow drag reduction benifits for plug on nose cone style arrangements. As soon as the laminar flow hits the end joint of the cone it's back turbulent again. And any nose hatch types are turbulent as of the leading edge of the hatch. And needless to say if there's an electric motor propellor on the nose then all bets are off.

The documentation for my old David Fraser sailplane analysis program models fuselage drag using a simple cross section model that assumes a regular streamlined shape and calculates the profile drag from basic calculations of cross section area and skin area.