Wing Ballast Distribution

"tstock" wrote

Could you explain this statement for us newbies... this is opposite of
what I would have expected so I would like to understand why it is so.

Go back to the ice skater analogy. Weight out at tips (like arms
outstretched while spinning) provides for a slower spin, and make it a
little easier to stop a spin.
--
Jim in NC

Dave Nadler wrote:
On Dec 10, 1:02 pm, SoaringXCellence wrote:
The weight toward the tips provides an interial resistance to roll.
That means the ride is a little smoother as the wing has greater
resistance to differential vertical gusting across the wingspan. It
is the same principle that tightrope walkers use by carrying a long
heavy pole.

Also helps stabilize the glider in a spin.

Hmmm... I don't think so. Twin jets are noted for more severe spin
characteristics.

Brian W

On Thu, 10 Dec 2009 10:02:55 -0800 (PST), SoaringXCellence
wrote:


The weight toward the tips provides an interial resistance to roll.
That means the ride is a little smoother as the wing has greater
resistance to differential vertical gusting across the wingspan. It
is the same principle that tightrope walkers use by carrying a long
heavy pole.

I beg to differ - at least for certain gliders it's vice-versa.

In the AS 22-2 (the mother of all ASH-25s) it is strictly required to
fill the outer wing tanks first (and empty them last) - the limiting
factor is the bending momentum of the wing of course.

The interesting part:
Even with completely filled outer wing bags (about 120 lbs per wing)
the roll rate doesn't suffer at all.
But filling the inner wing tanks (about 100 lbs per wing) instead of
having a co-pilot on board reduces the roll rate significantly.

Don't ask me why.

Wow - thanks to all who answered, especially Craig and Andy. I
understand now why weighted wing tips are good.

I’m puzzled about Andreas’ comments on the ASW-22, though:

Even with completely filled outer wing bags (about 120 lbs per wing)
the roll rate doesn't suffer at all.
But filling the inner wing tanks (about 100 lbs per wing) instead of
having a co-pilot on board reduces the roll rate significantly.

This behavior seems to defy physics!

-John

On Fri, 11 Dec 2009 06:00:23 -0800 (PST), jcarlyle
wrote:


This behavior seems to defy physics!

You got it.

I have the feeling that the cause might be some minor dihedral change
due to the water ballast, but I can't nail it down.



Bye
Andreas

Andreas Maurer wrote:

Even with completely filled outer wing bags (about 120 lbs per wing)
the roll rate doesn't suffer at all.
But filling the inner wing tanks (about 100 lbs per wing) instead of
having a co-pilot on board reduces the roll rate significantly.

Don't ask me why.


Adverse aeroelastic wing twist due to aileron action anti-servoing the
wing??

Brian W