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Leadout position for overhead fuselage tangency?

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Igor Burger:
:-))))))

Nice to see my old pictures here, thanks Dick for posting, I even forgot that I wrote it :-)

But to the point - yes, the line XXX program gives "some" LO offset good for tangent flight in level. The angle gives equilibrium between momentum of centrifugal force on an arm and line drag on arm.

It works well for speed (team) models but not for stunt. Stun models fly also overhead, where the centrifugal force is lowered by gravity. As I wrote that time, it will point the nose toward the pilot and it is the last thing we want overhead.

Additionally we have also rudder and side area of fuselage going to the game.

That is one point. Another point is, that perfect tangent position is necessary for speed models, not for Stunt models, I know many well flying model with relatively lot of yaw. Large models typically does not need any yaw for good line tension, because they have long lines and centrifugal force is enough, but since I started to play with indoors, I know that small model on short lines need to make line tension aerodynamically on large side area, yaw and prop offset :-).

Dean Pappas:
You are so right, Igor! Trading off a little line tension under 45 degrees for an improvement above is most sensible: a balance of opposing torques ( line tension inward and rudder/thrust outward) that shifts outward as the lines become parallel with gravity is desirable. It's funny that both the centrifics and the aerodynamics are speed-squared terms and  they do not change much relative to each other, but the gravity changes everything. (or as the 4-year old next door calls it: grabbity)   LL~
Dean Pappas

Alan Hahn:

--- Quote from: Igor Burger on October 06, 2009, 03:52:22 PM ---:-))))))

<snip>....
That is one point. Another point is, that perfect tangent position is necessary for speed models, not for Stunt models, I know many well flying model with relatively lot of yaw. Large models typically does not need any yaw for good line tension, because they have long lines and centrifugal force is enough, but since I started to play with indoors, I know that small model on short lines need to make line tension aerodynamically on large side area, yaw and prop offset :-).


--- End quote ---

Well all you need to do is fly a BiSlob through a wingover to see what offset can do for you!

Igor Burger:
:- )))))

Alan, if you use all that math calculating with centrifugal force, it will show you numbers indicating that this model:



just cannot fly :- )))))))))))))))))))))))))))))))))))))))

because:
- centrifugal force is too low to keep lines tight
- line offset is at angles not usefull for flying and it must fall down from top of hemisphere
- fuselage is 20deg off and by all theoretical rules meaning "only tangent is proper" the model must do lot os induced and unwanted crazy movements, yaws, rolls etc in every corner, but those corners are in reality clean (read "clean enoughh" for 150g light model from foam plate withou too much mass inertia at such a slow flight)

that model is built and trimmed under all rules from that long post ... I would say ... proofed  VD~

phil c:

--- Quote from: Dick Fowler on June 24, 2009, 08:39:16 PM ---Posted on SSW By Igor Berger. A rather interesting approach and runs contrary to some people's opinion.
 
--- End quote ---

I had a model with a serious line tension problem overhead.  All the usual tricks did nothing.  I finally got fed up, sliced the fin and cranked in an unscientific rudder offset of about 15 deg.  It made a tremendous difference in overhead line tension and did not cause any other problems that I could seee.

An adjustable rudder, or a Rabe rudder should be included in every stunter for those times when "going by the numbers" doesn't quite work out.

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