Measurement of CofG

Originally Posted by 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.

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...

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

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,

If you could email it to me at:

aggies78 at gmail.com

That would be much appreciated!

Thanks.

Rob S.

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 http://www.gliding.co.uk/bgainfo/tec...manual/4-1.pdf which is a good
guide to the process

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

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.

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.

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!"

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...