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Re: flight stroke (pretty short)




Waylon Rowley wrote:

> OK. I'm pretty sure that a tail will alway have an influence in
> flight, though. It's effect will not be
> neutral. Maybe I misunderstand you.

I think perhaps you do.  As an aside, though a tail will usually have an
effect;  its effect can be pretty much neutral if the 'pilot' so
desires.

> I should be more specific. Placing a short broad tailclose to the
> body, rather than extended on a long tail
> will allow you to move up or down faster.

Let me make sure that I understand you.  Are you saying that reducing
the available couple (moment) in the pitch axis will increase the rate
of motion about the pitch axis?  If so, why?  And yes, I understand
about the moment of inertia of the long tail.  But it's a two sided
coin.  As an aside, isn't wing sweep often primary for pitch control in
many flying animals anyway?  Or, when you refer to 'moving up or down
faster', are you referring to ROC and ROD?

> It takes more time for the long tail to move in a distal arch, right?

Does it?  Does the entire tail move, or just the distal end?  How
powerful are the muscles that move the tail?  How does the moment of
inertia change along the length of the tail?   How far does the tail
actually have to move to establish a paired counter-rotating vortex
along its length to create a pressure differential that will help move
it?  What about the 'added mass' effect?  Note that I don't really care
about any of these things specifically, I'm just raising questions that
would need to be adressed to truly define the parameters and avoid
jumping to conclusions.  As an aside, I've seen it said in a couple of
papers on bird tails (the short, broad type) that no part of the tail
aft of the widest point of the tail affects the pitching motion.
However, in three of my four planes, the entire movable portion of the
tail is located aft of the widest point, so I tend to question that
conclusion.  Do you?

> Rolling is another matter entirely.

Ain't it though.  But you mentioned maneuverability, and what people
usually refer to as maneuverability tends to be related more to the roll
axis, not so much pitch or yaw.