Wing Ballast Distribution

When you water ballast the four wing tanks of an LS8a you fill the
inner tanks first, and when you dump the water there’s provision for
the inner tanks to drain last. With a RS LS8-18 (and the newer DG LS8-
s) this procedure is reversed - the outer tanks are filled first and
there’s provision for the outer tanks to drain last. This was a
deliberate decision, because mechanical changes were made to the two-
handled dump system levers.

Why would aircraft designers want to keep weight towards the wing
tips? Does it have something to do with going from a 15m to an 18m
span? Wouldn’t the increased moment of inertia and wing spar bending
negatively affect performance?

-John

On Dec 10, 8:31*am, jcarlyle wrote:
Weight in the wing is load relieving. Try it with a paper airplane.
Tape coins around.


When you water ballast the four wing tanks of an LS8a you fill the
inner tanks first, and when you dump the water there’s provision for
the inner tanks to drain last. With a RS LS8-18 (and the newer DG LS8-
s) this procedure is reversed - the outer tanks are filled first and
there’s provision for the outer tanks to drain last. This was a
deliberate decision, because mechanical changes were made to the two-
handled dump system levers.

Why would aircraft designers want to keep weight towards the wing
tips? Does it have something to do with going from a 15m to an 18m
span? Wouldn’t the increased moment of inertia and wing spar bending
negatively affect performance?

-John

On Dec 10, 9:23*am, n7ly wrote:
On Dec 10, 8:31*am, jcarlyle wrote:
Weight in the wing is load relieving. Try it with a paper airplane.
Tape coins around.



When you water ballast the four wing tanks of an LS8a you fill the
inner tanks first, and when you dump the water there’s provision for
the inner tanks to drain last. With a RS LS8-18 (and the newer DG LS8-
s) this procedure is reversed - the outer tanks are filled first and
there’s provision for the outer tanks to drain last. This was a
deliberate decision, because mechanical changes were made to the two-
handled dump system levers.

Why would aircraft desgigners want to keep weight towards the wing
tips? Does it have something to do with going from a 15m to an 18m
span? Wouldn’t the increased moment of inertia and wing spar bending
negatively affect performance?

-John- Hide quoted text -

- Show quoted text -

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.

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.

I believe it was the Constellation that was bpopping rivets in
turbulence, the fix was 300# of lead in each wing tip.
JJ

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.

On Dec 10, 3:25*pm, JJ Sinclair wrote:
I believe it was the Constellation that was bpopping rivets in
turbulence, the fix was 300# of lead in each wing tip.
JJ

LAK-12 has 20lbs in the leading edge of each tip.

Frank Whiteley

Spin loading and sharp edge gust loading are different wing cases.

Brian W

JJ Sinclair wrote:
I believe it was the Constellation that was bpopping rivets in
turbulence, the fix was 300# of lead in each wing tip.
JJ

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.

Also helps stabilize the glider in a spin.

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.

Thanks!
-tom

tstock wrote:
Also helps stabilize the glider in a spin.

Could you explain this statement for us newbies...

Just don't worry. All moderately current regulations ask that a glider
is recoverable from a fully developed spin with any possible ballast
distribution.

On Dec 10, 4:37*pm, tstock wrote:
Also helps stabilize the glider in a spin.

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.

Thanks!
-tom

Dave's right, but I think he was just poking fun. The higher
rotational inertia tends to flatten the spin and make it harder to
recover from. Most of the long wing ships aren't certified for
spinning even without ballast.

Craig