Measurement of CofG

[Artiom M]

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.

[Don Johnstone[_4_]]

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

[Croft Brown]

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.
>

[Paul Remde]

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.

[Artiom M]

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.

[Tony[_5_]]

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

[Matt Herron Jr.]

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

[Morgan[_2_]]

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

[Hagbard Celine]

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.

[RAS56]

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

[Dan Marotta]

Why don't the manufactures publish the height to raise the tail as a
difference between the axle center lines above ground? Then you don't need
to cut or calculate.

Oh, gee... That'd be too simple.


"Hagbard Celine" > wrote in message
...
> 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.

[RAS56]

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

Ps-sorry if this double posts...

[Croft Brown]

I am sure I am not on my own when I say I have an Excel spreadsheet with
the calculations for C of G to be done. It may not be pretty but it does
the job. If you want a copy email me.
Croft




At 04:51 12 January 2012, RAS56 wrote:
>
>Hagbard Celine;807559 Wrote:
>> 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
>
>Ps-sorry if this double posts...
>
>
>
>
>--
>RAS56
>

[Croft Brown]

I am sure I am not on my own when I say I have an Excel spreadsheet with
the calculations for C of G to be done. It may not be pretty but it does
the job. If you want a copy email me.
Croft




At 04:51 12 January 2012, RAS56 wrote:
>
>Hagbard Celine;807559 Wrote:
>> 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
>
>Ps-sorry if this double posts...
>
>
>
>
>--
>RAS56
>

[RAS56]

Croft,

If you could email it to me at:

aggies78 at gmail.com

That would be much appreciated!

Thanks.

Rob S.

[James Thomson[_2_]]

At 04:51 12 January 2012, RAS56 wrote:
>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

Try www.gliding.co.uk/bgainfo/technical/ampmanual/4-1.pdf which is a good
guide to the process

[Dan Marotta]

Hey, Rob!

ZAP was my second glider. I flew her between April '88 and Nov '91.

Blast from the past!


"RAS56" > wrote in message
...
>
> 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
>
>
>
>
> --
> RAS56

[Mike[_37_]]

Some do. The Mini Nimbus has the correct height to raise the tail skid
from the floor.

Makes things easier for sure.


On Jan 11, 4:29*pm, "Dan Marotta" > wrote:
> Why don't the manufactures publish the height to raise the tail as a
> difference between the axle center lines above ground? *Then you don't need
> to cut or calculate.
>
> Oh, gee... *That'd be too simple.
>
> "Hagbard Celine" > wrote in message
>
>
>
>
>
>
>
>
> > 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.

[Cliff Hilty[_2_]]

When I did my Ventus (not a club plane) I did it with flying weight. IE I
started with me, flying gear, water ballast, drinking water, batteries ect.
in the plane. Being of sound ballast myself I needed to dump ballast to get
to gross weight. I did this with a stop watch and 5 gallon buckets under
the dump valves and had the "Weigher" tell me when I got to gross, stop and
record both time and gallons dumped, then continued to 9 lbs per sq ft,
stop and record, then dumped the rest. This gave me a very accurate amounts
in both gallons and time (seconds to dump for any wing loading I may want
to fly with.

Now I just time the fill time to half ballast and fly :) After all its a
Ventus and won't thermal worth a crap with full load :)

CH Ventus B
CH Ventus B

"If we are all "just dust in the wind", then I want to be at the top of a Huge Dust Devil!"

[Andy[_1_]]

On Jan 11, 4:29*pm, "Dan Marotta" > wrote:
> Why don't the manufactures publish the height to raise the tail as a
> difference between the axle center lines above ground? *Then you don't need
> to cut or calculate.
>
> Oh, gee... *That'd be too simple.

One possible reason is that the height is not a constant for any
glider that has a compressible pneumatic tyre or a sprung landing
gear. Both have deflection that depends on the glider mass. That
same deflection would need to be applied to the tail height. It may
not be neglible at max gross wt.

Speaking of sprung landing gear - in some cases the deflection changes
not only the height but also the distance between the tyre/ground
contact point and the datum. That applies to modern Schleicher single
seaters and probably other gliders. The best plan is to do the weight
and ballance as defined by the manufacturer.

I also calculated my own pilot arm as I considered the generalities in
the manual to be unacceptable. That can be done with a reasonably
accurate bathroom scale under the tail as the calculation is
independent of weight on the main gear.

Andy (GY)

[Dave Nadler]

On Thursday, January 12, 2012 12:48:09 PM UTC-5, Cliff Hilty wrote:
> I did this with a stop watch and 5 gallon buckets under
> the dump valves and had the "Weigher" tell me when I got to gross, stop and
> record both time and gallons dumped, then continued to 9 lbs per sq ft,
> stop and record, then dumped the rest. This gave me a very accurate amounts
> in both gallons and time (seconds to dump for any wing loading I may want
> to fly with.

Um, no, dump speed is limited by vent (in flight and on ground).
Lower pressure on vent in flight >>> slower dump time in flight...
Also, for that glider, enlarging vent holes makes it safer
if you fall off a ridge and need to dump fast...

[RAS56]

Hey, Rob!

ZAP was my second glider. I flew her between April '88 and Nov '91.

Blast from the past!

Dan,

Great to hear a little history on her!

I'm trying to treat her well and keep her flying down here in the Texas Hill Country outside of Austin.

She went through a rough patch from '94 to '04...didn't fly and trailer leaks caused water damage on the fuse under the dolly which Gehrlein repaired...now only ~1040 TT. Would love to put 50-60 hours on it this season...put about 25 hours on in '11.

Pass along any history to me at aggies78 at gmail dot com.

Rob

[Dan Marotta]

...."sprung landing gear." That's why I specified axle centers rather than
simply raising the tail. I didn't consider sprung gear and your information
is good on that account.

As to following the manufacturer's recommendations, I'm all for that. My
question should have been "why do they specify such a complicated method for
gliders with unsprung gear" though I didn't mention the suspension part.
BTW, my LAK-17a specifies an angle of 100:2.9.


"Andy" > wrote in message
...
On Jan 11, 4:29 pm, "Dan Marotta" > wrote:
> Why don't the manufactures publish the height to raise the tail as a
> difference between the axle center lines above ground? Then you don't need
> to cut or calculate.
>
> Oh, gee... That'd be too simple.

One possible reason is that the height is not a constant for any
glider that has a compressible pneumatic tyre or a sprung landing
gear. Both have deflection that depends on the glider mass. That
same deflection would need to be applied to the tail height. It may
not be neglible at max gross wt.

Speaking of sprung landing gear - in some cases the deflection changes
not only the height but also the distance between the tyre/ground
contact point and the datum. That applies to modern Schleicher single
seaters and probably other gliders. The best plan is to do the weight
and ballance as defined by the manufacturer.

I also calculated my own pilot arm as I considered the generalities in
the manual to be unacceptable. That can be done with a reasonably
accurate bathroom scale under the tail as the calculation is
independent of weight on the main gear.

Andy (GY)

[Hagbard Celine]

When we did my ASW-15 we took the weights just balancing the wings
level, no stand. Fore and aft level was done as you describe (my
manual has about the same information as yours) with the exception I
noted about using a digital protractor instead of making the triangle.
As my ship was exported from Germany in 1998 we had copies of the
W&B's they did there for my maintenance engineer to use as a guideline
for making the new W&B and equipment list. The records that
accompanied my ship when it was exported show that the W&B was done
every second year when it was in Germany! I could get you scans of the
forms though being of German origin they would be useful as a
guideline at best.

Sometimes you can get a surprise when doing a W&B. My club has a Grob
102 Standard III. When the A.D. requiring the installation of lead
mass balance in the control system was done we naturally had to
reweigh the glider. The last time it had been weighed was by a
previous owner many years before we bought it. The new weight was
about 80 pounds LESS than the last one. Aircraft generally don't LOSE
weight over the years, especially when you've just bonded a bunch of
lead to them. The maintenance shop double and triple checked their
procedures, recalibrated their scales and reweighed the glider several
times. The new weight was accurate. We're still trying to figure out
what the hell was going on with the previous weighing. Water ballast
left in the tanks maybe?

On Jan 11, 8:51*pm, RAS56 > wrote:
> Hagbard Celine;807559 Wrote:
>
> > 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
>
> Ps-sorry if this double posts...
>
> --
> RAS56

[Cliff Hilty[_2_]]

At 22:00 12 January 2012, Dave Nadler wrote:
>On Thursday, January 12, 2012 12:48:09 PM UTC-5, Cliff Hilty wrote:
>> I did this with a stop watch and 5 gallon buckets under
>> the dump valves and had the "Weigher" tell me when I got to gross,
stop
>and
>> record both time and gallons dumped, then continued to 9 lbs per sq
ft,
>> stop and record, then dumped the rest. This gave me a very accurate
>amounts
>> in both gallons and time (seconds to dump for any wing loading I may
want
>> to fly with.
>
>Um, no, dump speed is limited by vent (in flight and on ground).
>Lower pressure on vent in flight >>> slower dump time in flight...
>Also, for that glider, enlarging vent holes makes it safer
>if you fall off a ridge and need to dump fast...
>

Dave you missed my point any glider that you fly it will work for on the

ground to get to your desired take off weight. No water meters ect for
calcs also I use a 3 gallon bucket and time the fill rate to decide how
much to put in each wing to get to what I want. 9 gallons per wing works
for me and its easy and quick to do once you have the initial weight snd
balance.

[Bob Kuykendall]

On Jan 11, 3:29*pm, "Dan Marotta" > wrote:

> Why don't the manufactures publish the height to raise the tail as a
> difference between the axle center lines above ground? *Then you don't need
> to cut or calculate.
>
> Oh, gee... *That'd be too simple.

I specify W&B leveling with a level and wedge on the aft fuselage
because it is the simplest and easiest way of getting the glider
level. You make the wedge and keep it in the glider's toolbox, or you
use a digital level as somebody else suggest. I don't see what's so
hard or complicated about that.

I have actually designed in a couple of internal surfaces that are
parallel with the glider's x axis, but they are in under the wing spar
and you can't see them while actually doing the leveling. With the
level on the aft fuselage, you can actually see it while you are
raising and lowering the tail to find the level.

To specify the level in terms of height of the axles, you have to know
the distances of the axles from the x axis, which is not simple
because the gear might have an oleo strut (as does mine), and you
don't know if the tailwheel location has been changed or modified.

Also, when leveling to the axles, you have to know what you're
leveling to. If you have a hangar or shop floor known to be level,
you're golden. But if you're doing a W&B in the field or on grass or
another uneven surface, then you need to construct a water level or
other surveying tool. By then, the bubble level on the aft fuselage
starts to look pretty good.

Thanks, Bob K.

[Dan Marotta]

Thanks for a good technical reply.

Now I just have to check and see if any of my measuring devices have decimal
inch/cm graduations. Seems most are graduated in 1/16th, etc... Let/s
see... That would be 200 inches long and 2 and 14.4/16 inches high. Oh,
crap! There's that pesky decimal again. I know - I'll make my triangle
2,000 inches long and 29 inches high! Now, if I could just find a surface
on the glider where I can make that fit.

Really, how accurately can you measure 2.9 inches, mark it, and cut it? I
don't have a machine shop. This all reminds me of the old Air Force adage:
"Measure with a micrometer, mark with a grease pencil, cut with an axe".

I've been out of school for a long time, so my calculation is probably
wrong, but it looks like 100:2.9 is an angle of 1.6618 degrees. Will a
digital level get that accuracy? Is that accuracy really necessary?

What's the good of a parallel surface if it's not accessible? Why not make,
say, the arm rest parallel to the longitudinal axis? Then you could simply
place a carpenter's level on the arm rest and, voila!

And, BTW, you shouldn't really be doing a weight and balance in a grassy
field, no matter how level it is. The slightest breeze will generate some
measureable amount of lift and throw your weight measurement off. And if
that weight change is not enough to be concerned with, then I challenge the
need to measure the angle of the fuselage to the thousandth of a degree
(measure with a micrometer).

Bottom line - that's what the manufacturer says to do and I'll try my best
to do it that way, but I'm not going to lose any sleep over it.

"Bob Kuykendall" > wrote in message
...
On Jan 11, 3:29 pm, "Dan Marotta" > wrote:

> Why don't the manufactures publish the height to raise the tail as a
> difference between the axle center lines above ground? Then you don't need
> to cut or calculate.
>
> Oh, gee... That'd be too simple.

I specify W&B leveling with a level and wedge on the aft fuselage
because it is the simplest and easiest way of getting the glider
level. You make the wedge and keep it in the glider's toolbox, or you
use a digital level as somebody else suggest. I don't see what's so
hard or complicated about that.

I have actually designed in a couple of internal surfaces that are
parallel with the glider's x axis, but they are in under the wing spar
and you can't see them while actually doing the leveling. With the
level on the aft fuselage, you can actually see it while you are
raising and lowering the tail to find the level.

To specify the level in terms of height of the axles, you have to know
the distances of the axles from the x axis, which is not simple
because the gear might have an oleo strut (as does mine), and you
don't know if the tailwheel location has been changed or modified.

Also, when leveling to the axles, you have to know what you're
leveling to. If you have a hangar or shop floor known to be level,
you're golden. But if you're doing a W&B in the field or on grass or
another uneven surface, then you need to construct a water level or
other surveying tool. By then, the bubble level on the aft fuselage
starts to look pretty good.

Thanks, Bob K.

[Wayne Paul]

As Bob mentioned, building a wedge for your gilder is a good solution the
will provide accurate results time after time. Here is the wedge that I use
for my HP-14. I'm sure the dimensions required to build a similar device
are available for production aircraft.
http://www.soaridaho.com/Schreder/Construction/Fuselage_Level/

Wayne
HP-14 "6F"
http://www.soaridaho.com/Schreder



"Bob Kuykendall" wrote in message
...

On Jan 11, 3:29 pm, "Dan Marotta" > wrote:

> Why don't the manufactures publish the height to raise the tail as a
> difference between the axle center lines above ground? Then you don't
> need
> to cut or calculate.
>
> Oh, gee... That'd be too simple.

I specify W&B leveling with a level and wedge on the aft fuselage
because it is the simplest and easiest way of getting the glider
level. You make the wedge and keep it in the glider's toolbox, or you
use a digital level as somebody else suggest. I don't see what's so
hard or complicated about that.

I have actually designed in a couple of internal surfaces that are
parallel with the glider's x axis, but they are in under the wing spar
and you can't see them while actually doing the leveling. With the
level on the aft fuselage, you can actually see it while you are
raising and lowering the tail to find the level.

To specify the level in terms of height of the axles, you have to know
the distances of the axles from the x axis, which is not simple
because the gear might have an oleo strut (as does mine), and you
don't know if the tailwheel location has been changed or modified.

Also, when leveling to the axles, you have to know what you're
leveling to. If you have a hangar or shop floor known to be level,
you're golden. But if you're doing a W&B in the field or on grass or
another uneven surface, then you need to construct a water level or
other surveying tool. By then, the bubble level on the aft fuselage
starts to look pretty good.

Thanks, Bob K.

[Bob Kuykendall]

On Jan 15, 8:57*am, "Dan Marotta" > wrote:

> Really, how accurately can you measure 2.9 inches, mark it, and cut it?

I think that just on the far side of 2-7/8" would do just fine.

> ...it looks like 100:2.9 is an angle of 1.6618 degrees. *Will a
> digital level get that accuracy? Is that accuracy really necessary?

Most digital levels will offer repeatable measurements to 0.1 degrees,
and I think that that is close enough. In this case I'd feel fine
about a reading of 1.7 degrees. For my fuselage, the exact tailboom
slope is 1.213 degrees, but 1.2 or even 1-1/4 degrees would be fine.

> What's the good of a parallel surface if it's not accessible? *Why not make,
> say, the arm rest parallel to the longitudinal axis? *Then you could simply
> place a carpenter's level on the arm rest and, voila!

Thanks, the armrest trick is a good idea, I might adopt that; it would
be useful for people who have digital levels that beep when they're
actually level.

Thanks again, Bob K.

[Dan Marotta]

I like the idea of a "beeping" level which would allow a single person to
complete the operation. And I *really* like the design of Wayne's "wedge".

Bob, thanks for stating what I've always felt, i.e., the TLAR method is good
enough (2-7/8"). I was (wrongly) getting the impression that people were
stuck on precision which I couldn't attain. It would seem pointless to
measure the angle to a gnat's ass and then fly with boots and a heavy jacket
one day and shorts and sneakers the next.

One more time - Wayne, I LIKE the design of your wedge. I think I'll build
one. And ask the manufacturer why they don't include at least a drawing for
a device to level the fuselage.


"Bob Kuykendall" > wrote in message
...
On Jan 15, 8:57 am, "Dan Marotta" > wrote:

> Really, how accurately can you measure 2.9 inches, mark it, and cut it?

I think that just on the far side of 2-7/8" would do just fine.

> ...it looks like 100:2.9 is an angle of 1.6618 degrees. Will a
> digital level get that accuracy? Is that accuracy really necessary?

Most digital levels will offer repeatable measurements to 0.1 degrees,
and I think that that is close enough. In this case I'd feel fine
about a reading of 1.7 degrees. For my fuselage, the exact tailboom
slope is 1.213 degrees, but 1.2 or even 1-1/4 degrees would be fine.

> What's the good of a parallel surface if it's not accessible? Why not
> make,
> say, the arm rest parallel to the longitudinal axis? Then you could simply
> place a carpenter's level on the arm rest and, voila!

Thanks, the armrest trick is a good idea, I might adopt that; it would
be useful for people who have digital levels that beep when they're
actually level.

Thanks again, Bob K.

[Don Johnstone[_4_]]

At 16:57 15 January 2012, Dan Marotta wrote:
>Thanks for a good technical reply.
>
>Now I just have to check and see if any of my measuring devices have
>decimal
>inch/cm graduations. Seems most are graduated in 1/16th, etc... Let/s
>see... That would be 200 inches long and 2 and 14.4/16 inches high. Oh,

>crap! There's that pesky decimal again. I know - I'll make my triangle
>2,000 inches long and 29 inches high! Now, if I could just find a surface

>on the glider where I can make that fit.
>
>Really, how accurately can you measure 2.9 inches, mark it, and cut it? I

>don't have a machine shop. This all reminds me of the old Air Force
adage:

Why would you want to use inches specifically? the ratio 2000:29 could be
inches, millimeters, bananas or ay other unit you might wish to use, that
is why it is expressed that way, works whatever system of measurement you
care to use. A distance of 10000mm with a drop of 145mm would seem to me
pretty easy to set up.

[Dan Marotta]

Actually, I mistyped. It's 100:2.9 and, yes, I understand that it's a ratio
and unitless. Still, I don't have any tools which measure nine tenths of
anything, be they banannas, apples, inches, or millimeters. The point I was
trying to make is that such precision as 1/1000th of a degree really isn't
necessary. When I attended engineering school, I used a slide rule, not a
computer, and I learned that close enough is good enough.


"Don Johnstone" > wrote in message
.com...
> At 16:57 15 January 2012, Dan Marotta wrote:
>>Thanks for a good technical reply.
>>
>>Now I just have to check and see if any of my measuring devices have
>>decimal
>>inch/cm graduations. Seems most are graduated in 1/16th, etc... Let/s
>>see... That would be 200 inches long and 2 and 14.4/16 inches high. Oh,
>
>>crap! There's that pesky decimal again. I know - I'll make my triangle
>>2,000 inches long and 29 inches high! Now, if I could just find a surface
>
>>on the glider where I can make that fit.
>>
>>Really, how accurately can you measure 2.9 inches, mark it, and cut it? I
>
>>don't have a machine shop. This all reminds me of the old Air Force
> adage:
>
> Why would you want to use inches specifically? the ratio 2000:29 could be
> inches, millimeters, bananas or ay other unit you might wish to use, that
> is why it is expressed that way, works whatever system of measurement you
> care to use. A distance of 10000mm with a drop of 145mm would seem to me
> pretty easy to set up.
>

[Brad[_2_]]

On Jan 16, 8:13*am, "Dan Marotta" > wrote:
> I like the idea of a "beeping" level which would allow a single person to
> complete the operation. *And I *really* like the design of Wayne's "wedge".
>
> Bob, thanks for stating what I've always felt, i.e., the TLAR method is good
> enough (2-7/8"). *I was (wrongly) getting the impression that people were
> stuck on precision which I couldn't attain. *It would seem pointless to
> measure the angle to a gnat's ass and then fly with boots and a heavy jacket
> one day and shorts and sneakers the next.
>
> One more time - Wayne, I LIKE the design of your wedge. *I think I'll build
> one. *And ask the manufacturer why they don't include at least a drawing for
> a device to level the fuselage.
>
> "Bob Kuykendall" > wrote in message
>
> ...
> On Jan 15, 8:57 am, "Dan Marotta" > wrote:
>
> > Really, how accurately can you measure 2.9 inches, mark it, and cut it?
>
> I think that just on the far side of 2-7/8" would do just fine.
>
> > ...it looks like 100:2.9 is an angle of 1.6618 degrees. Will a
> > digital level get that accuracy? *Is that accuracy really necessary?
>
> Most digital levels will offer repeatable measurements to 0.1 degrees,
> and I think that that is close enough. In this case I'd feel fine
> about a reading of 1.7 degrees. For my fuselage, the exact tailboom
> slope is 1.213 degrees, but 1.2 or even 1-1/4 degrees would be fine.
>
> > What's the good of a parallel surface if it's not accessible? Why not
> > make,
> > say, the arm rest parallel to the longitudinal axis? Then you could simply
> > place a carpenter's level on the arm rest and, voila!
>
> Thanks, the armrest trick is a good idea, I might adopt that; it would
> be useful for people who have digital levels that beep when they're
> actually level.
>
> Thanks again, Bob K.

when we did the W & B for my Tetra we used a 24" level and a 1/2" tall
socket, with the level located as required by Bob it was easy to set
everything up on scales. I had my engineer friend do the
math............empty weight came out at 479 pounds!

Brad