Measurement of CofG

Hi all,
I’m trying to understand how to determine CofG of my DG-100. In the
maintenance manual there is such sentence which I do not understand:
“The fuselage must be leveled so that the top of the aft fuselage boom
has a tail-down slope of l00 : 3.67.“
I understood that I need to lift up the sailplane tail, but what does
100:3.67 means? To what height? Can you help me with that?

BR,
Artiom.

At 11:48 11 January 2012, Artiom M wrote:
Hi all,
I=92m trying to understand how to determine CofG of my DG-100. In the
maintenance manual there is such sentence which I do not understand:
=93The fuselage must be leveled so that the top of the aft fuselage boom
has a tail-down slope of l00 : 3.67.=93
I understood that I need to lift up the sailplane tail, but what does
100:3.67 means? To what height? Can you help me with that?

BR,
Artiom.
what it means is if you take a distance of 100mm along the boom the front
of the distance line has to be 3.67mm higher than the rear of the distance
line or put another way a down angle of 2.1 degrees

There is a very good diagram in the maintenance manual that shows how the
aircraft is positioned when the measurements are taken. If you do not have
a manual, email me and I will send you one (no charge either!)
Croft


At 11:48 11 January 2012, Artiom M wrote:
Hi all,
I=92m trying to understand how to determine CofG of my DG-100. In the
maintenance manual there is such sentence which I do not understand:
=93The fuselage must be leveled so that the top of the aft fuselage boom
has a tail-down slope of l00 : 3.67.=93
I understood that I need to lift up the sailplane tail, but what does
100:3.67 means? To what height? Can you help me with that?

BR,
Artiom.

Hi Artiom,

Good question. It is a ratio. For every 100 units (inches, mm, whatever)
of horizontal travel, it should go down 3.67 (of the same units).

I recommend cutting a board that is 100 cm on one side and 3.67 cm on the
other side. It should be a triangle shape. Then lay it on the tail in the
correct location and use a bubble level on top of it to level the fuselage.
The pointy end should be pointed toward the front of the glider.

Another option (which is not as precise) use a long yardstick with a bubble
level built-in. Measure how long it is (let's assume it is 36" long) and
use the ratio to calculate how high the back end should be lifted up off the
tail. 36" x 3.67/100 = 1.3212". You could tape something to the end of it
to get it to sit on the tail at the correct height.

Does that make sense?

Good Soaring,

Paul Remde

"Artiom M" wrote in message
...
Hi all,
I’m trying to understand how to determine CofG of my DG-100. In the
maintenance manual there is such sentence which I do not understand:
“The fuselage must be leveled so that the top of the aft fuselage boom
has a tail-down slope of l00 : 3.67.“
I understood that I need to lift up the sailplane tail, but what does
100:3.67 means? To what height? Can you help me with that?

BR,
Artiom.

Many thanks for answers guys!
Finally I understand how to do that.
It seem to me the best idea is to cut a board and use a bubble level.
Sounds great and easy to do! Thanks Paul!

BR.
Artiom.

p.s. One more question... As English is not my native language can you
describe in other words what “boom” means? As I understand this is a
Pipe (part of fuselage from end of the wings to tail)? Am I right?

On 11 Sau, 15:09, "Paul Remde" wrote:
Hi Artiom,

Good question. *It is a ratio. *For every 100 units (inches, mm, whatever)
of horizontal travel, it should go down 3.67 (of the same units).

I recommend cutting a board that is 100 cm on one side and 3.67 cm on the
other side. *It should be a triangle shape. *Then lay it on the tail in the
correct location and use a bubble level on top of it to level the fuselage.
The pointy end should be pointed toward the front of the glider.

Another option (which is not as precise) use a long yardstick with a bubble
level built-in. *Measure how long it is (let's assume it is 36" long) and
use the ratio to calculate how high the back end should be lifted up off the
tail. *36" x 3.67/100 = 1.3212". *You could tape something to the end of it
to get it to sit on the tail at the correct height.

Does that make sense?

Good Soaring,

Paul Remde

"Artiom M" wrote in message

...
Hi all,
I’m trying to understand how to determine CofG of my DG-100. In the
maintenance manual there is such sentence which I do not understand:
“The fuselage must be leveled so that the top of the aft fuselage boom
has a tail-down slope of l00 : 3.67.“
I understood that I need to lift up the sailplane tail, but what does
100:3.67 means? To what height? Can you help me with that?

BR,
Artiom.

On Jan 11, 9:10*am, Artiom M wrote:
Many thanks for answers guys!
Finally I understand how to do that.
It seem to me the best idea is to cut a board and use a bubble level.
Sounds great and easy to do! Thanks Paul!

BR.
Artiom.

p.s. One more question... As English is not my native language can you
describe in other words what “boom” means? As I understand this is a
Pipe (part of fuselage from end of the wings to tail)? Am I right?

On 11 Sau, 15:09, "Paul Remde" wrote:

Hi Artiom,

Good question. *It is a ratio. *For every 100 units (inches, mm, whatever)
of horizontal travel, it should go down 3.67 (of the same units).

I recommend cutting a board that is 100 cm on one side and 3.67 cm on the
other side. *It should be a triangle shape. *Then lay it on the tail in the
correct location and use a bubble level on top of it to level the fuselage.
The pointy end should be pointed toward the front of the glider.

Another option (which is not as precise) use a long yardstick with a bubble
level built-in. *Measure how long it is (let's assume it is 36" long) and
use the ratio to calculate how high the back end should be lifted up off the
tail. *36" x 3.67/100 = 1.3212". *You could tape something to the end of it
to get it to sit on the tail at the correct height.

Does that make sense?

Good Soaring,

Paul Remde

"Artiom M" wrote in message

....
Hi all,
I’m trying to understand how to determine CofG of my DG-100. In the
maintenance manual there is such sentence which I do not understand:
“The fuselage must be leveled so that the top of the aft fuselage boom
has a tail-down slope of l00 : 3.67.“
I understood that I need to lift up the sailplane tail, but what does
100:3.67 means? To what height? Can you help me with that?

BR,
Artiom.

yes you are correct

On Jan 11, 8:06*am, Tony wrote:
On Jan 11, 9:10*am, Artiom M wrote:









Many thanks for answers guys!
Finally I understand how to do that.
It seem to me the best idea is to cut a board and use a bubble level.
Sounds great and easy to do! Thanks Paul!

BR.
Artiom.

p.s. One more question... As English is not my native language can you
describe in other words what “boom” means? As I understand this is a
Pipe (part of fuselage from end of the wings to tail)? Am I right?

On 11 Sau, 15:09, "Paul Remde" wrote:

Hi Artiom,

Good question. *It is a ratio. *For every 100 units (inches, mm, whatever)
of horizontal travel, it should go down 3.67 (of the same units).

I recommend cutting a board that is 100 cm on one side and 3.67 cm on the
other side. *It should be a triangle shape. *Then lay it on the tail in the
correct location and use a bubble level on top of it to level the fuselage.
The pointy end should be pointed toward the front of the glider.

Another option (which is not as precise) use a long yardstick with a bubble
level built-in. *Measure how long it is (let's assume it is 36" long) and
use the ratio to calculate how high the back end should be lifted up off the
tail. *36" x 3.67/100 = 1.3212". *You could tape something to the end of it
to get it to sit on the tail at the correct height.

Does that make sense?

Good Soaring,

Paul Remde

"Artiom M" wrote in message

....
Hi all,
I’m trying to understand how to determine CofG of my DG-100. In the
maintenance manual there is such sentence which I do not understand:
“The fuselage must be leveled so that the top of the aft fuselage boom
has a tail-down slope of l00 : 3.67.“
I understood that I need to lift up the sailplane tail, but what does
100:3.67 means? To what height? Can you help me with that?

BR,
Artiom.

yes you are correct

Don't forget to consider using the Program SeeG to help you with
Weight and balance calculations (shameless plug). You can find out
more at www.glideplan.com

Cheers,

Matt

I've got a Glideplan file for the DG-100G that we have. I think I've
already got all the moments for ballast location and pilot established
in that.

Morgan


On Jan 11, 10:24*am, "Matt Herron Jr." wrote:
On Jan 11, 8:06*am, Tony wrote:









On Jan 11, 9:10*am, Artiom M wrote:

Many thanks for answers guys!
Finally I understand how to do that.
It seem to me the best idea is to cut a board and use a bubble level.
Sounds great and easy to do! Thanks Paul!

BR.
Artiom.

p.s. One more question... As English is not my native language can you
describe in other words what “boom” means? As I understand this is a
Pipe (part of fuselage from end of the wings to tail)? Am I right?

On 11 Sau, 15:09, "Paul Remde" wrote:

Hi Artiom,

Good question. *It is a ratio. *For every 100 units (inches, mm, whatever)
of horizontal travel, it should go down 3.67 (of the same units).

I recommend cutting a board that is 100 cm on one side and 3.67 cm on the
other side. *It should be a triangle shape. *Then lay it on the tail in the
correct location and use a bubble level on top of it to level the fuselage.
The pointy end should be pointed toward the front of the glider.

Another option (which is not as precise) use a long yardstick with a bubble
level built-in. *Measure how long it is (let's assume it is 36" long) and
use the ratio to calculate how high the back end should be lifted up off the
tail. *36" x 3.67/100 = 1.3212". *You could tape something to the end of it
to get it to sit on the tail at the correct height.

Does that make sense?

Good Soaring,

Paul Remde

"Artiom M" wrote in message

...
Hi all,
I’m trying to understand how to determine CofG of my DG-100. In the
maintenance manual there is such sentence which I do not understand:
“The fuselage must be leveled so that the top of the aft fuselage boom
has a tail-down slope of l00 : 3.67.“
I understood that I need to lift up the sailplane tail, but what does
100:3.67 means? To what height? Can you help me with that?

BR,
Artiom.

yes you are correct

Don't forget to consider using the Program SeeG to help you with
Weight and balance calculations (shameless plug). * *You can find out
more atwww.glideplan.com

Cheers,

Matt

If the shop has a digital protractor you could also convert the rise/
run to degrees, put the protractor on the specified part of the tail
boom and raise the tail until it reads the correct angle.

Arctan(rise/run) = angle in degrees

About 2.1 degrees, sloping down towards the tail in this case.

Same question, hopefully same answer...could use a little more info.

I'm trying to put together a W&B event at our club, we're bringing in outside help from another club with a set of scales and the experience of knowing what to do.

WRT positioning the glider at the correct angle, my ship is an ASW-19b. Although my owners manual has a page dedicated to CG info, there's nothing in there about what procedure to use to actually weigh the thing. It's just a page with a CG envelope on it.

Now I did find on page 30 of the manual (a page that has general dimensions as well as specs for control deflections) a side view drawing with info presented as the thread starter discussed, mine says 1000 by 45.

SO, to do the procedure correctly, construct a small triangle with those dimensions, inflate the main wheel to proper pressure, put a level on the triangle, then raise the tail till I get a level bubble? It would seem to make sense that this is done with wings level laterally as well, correct? Lightly (fingertips) or is a wingstand under a tip ok? THEN, take the weights?

Finally, this will be the 4th W&B for this glider. All the ones done previously have had a "form" with a glider drawing on it and appropriate spots to fill in main wheel/tail wheel weights, etc. Where can we obtain "blanks" to fill in our ships for our event? We will have an A&P IA overseeing the process and signing off logbooks. As I said, I'm coordinating, so I'm trying to get all the info/materials each owner will need to have on hand at weigh-in so the event goes smoothly.

Thanks much,

Rob
ASW-19b
ZAP