Glider Handling Question

Has this change in handling actually been quantified, or is it just a perception?

Boggs

At 18:26 23 September 2016, Waveguru wrote:
Has this change in handling actually been quantified, or is it just a
perception?

Boggs

That's fairly easy ,it's well documented that the spin characteristics is
effected
by the tail weight.
So
You can easily test that with a ship that has a fin tank ,full tank ,high
tow and
time 45degree left to right ,then test the ease of entering a spin.
Then drop the tail ballast and repeat.
With careful planning you could probably do it from 1 high tow.
It sounds like a good winter protect.

I like the "crotch theory" best. We should develop special soaring pants with a "U" shaped stiffener to insure full aileron deflection is possible with the stick all the way back. This would also give us that cowboy swagger after landing...

I agree with Steven L,
The differential forces required to roll a wing must be easily of the order of 5-20 kg, making a increased tail load of "5kg" influential.
after all total aerodynamic drag of most gliders in level flight at slow speeds is somewhere around 20 lbs isn't it?

Max weight divided by numerical L/D at best L/D speed?

I.E. std Cirrus 728 lbs divided by 36 = 20.2 lbs drag (no water)

interesting topic!!

https://sourceforge.net/projects/xflr5/

Who wants to download XFLR5 to test some hypotheses?

Random thoughts:

We tend to envision Center of Gravity as moving exactly along the design longitudinal axis and ignore any vertical component to the actual balance point of an aircraft. Just like larger helicopters have to calculate lateral CG position as well as longitudinal, perhaps we need to think about the actual CG in relation in three dimensions to explore whether CG affects roll rate (roll moment).

True CG location not only moves fore and aft, but up and down depending on where weight is added or moved. We've been taught that it isn't important. Imagine adding weight well above or below the longitudinal axis; let's say you installed an O2 tank or added nose weights. The CG's relation to the center of rotation would change and could affect the roll moment. How much, I can't say, but I'm trying to figure it out.

Paul A.
Jupiter, FL

From what I've seen on multiple gliders, nose weight is very close to the 3 dimensional CG, fixed tail weight is similar.
Water weight in the tail has a small part (maybe 35%?) below the total CG, thus changes the total CG a tiny bit although 2 dimensional CG is still valid.

Is it really worth it?, I don't know.

No, I'm not an engineer, but I have some reasonable background.

Hello, I'm the author of the article and I also don't know. I just referred the engineer's comment about the roll-rate I (roughly) measured during the test flight.

Nice to know someone's actually reading my articles ;-)

all the best,

Aldo Cernezzi




Il giorno mercoledì 14 settembre 2016 14:04:30 UTC+2, Roy B. ha scritto:
In this month's Gliding International article on the Ventus 3, Aldo Cernezzi writes, "According to Berd Weber, I flew with a relatively forward CoG, which may have an impact on roll speed". This got me to thinking of my own anecdotal experiences with very forward CGs having a negative impact on roll rate, and I think that a forward CG does degrade the roll rate. But I can't figure out why that happens. Can anybody explain it in simple terms?
ROY

On Tuesday, September 27, 2016 at 8:14:18 AM UTC-6, wrote:
Hello, I'm the author of the article and I also don't know. I just referred the engineer's comment about the roll-rate I (roughly) measured during the test flight.

Nice to know someone's actually reading my articles ;-)

all the best,

Aldo Cernezzi




Il giorno mercoledì 14 settembre 2016 14:04:30 UTC+2, Roy B. ha scritto:
In this month's Gliding International article on the Ventus 3, Aldo Cernezzi writes, "According to Berd Weber, I flew with a relatively forward CoG, which may have an impact on roll speed". This got me to thinking of my own anecdotal experiences with very forward CGs having a negative impact on roll rate, and I think that a forward CG does degrade the roll rate. But I can't figure out why that happens. Can anybody explain it in simple terms?
ROY

Aldo,
Keep the faith! I always read your articles. They are excellent and quite comprehensive, so please continue writing them. I am very sure that they are also read by glider pilots all over the world. We can all benefit by the knowledge and insight you provide.

Thanks again - Renny

Renny Rozzoni
Abuquerque, NM

On Saturday, September 24, 2016 at 6:31:36 PM UTC-4, Charlie M. (UH & 002 owner/pilot) wrote:
From what I've seen on multiple gliders, nose weight is very close to the 3 dimensional CG, fixed tail weight is similar.
Water weight in the tail has a small part (maybe 35%?) below the total CG, thus changes the total CG a tiny bit although 2 dimensional CG is still valid.

Is it really worth it?, I don't know.

No, I'm not an engineer, but I have some reasonable background.

Hello Aldo! Your articles are always the first things I read! Your aircraft reviews are fair and informative. ROY