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Discus 2 Optimal CG location



 
 
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  #1  
Old June 24th 18, 08:05 PM posted to rec.aviation.soaring
Dave Springford
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Default Discus 2 Optimal CG location

Can anyone advise the optimal CG location for a D2?

If the 2a and 2b have different optimal locations, I would like to know both.

TIA,

Dave
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  #2  
Old June 24th 18, 09:09 PM posted to rec.aviation.soaring
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Default Discus 2 Optimal CG location

On Sunday, June 24, 2018 at 9:05:51 PM UTC+2, Dave Springford wrote:
Can anyone advise the optimal CG location for a D2?

If the 2a and 2b have different optimal locations, I would like to know both.

TIA,

Dave


Optimum is where ever you like it best.

I fly mine full aft for the better handling, but it glides better a bit further forward.
  #3  
Old June 25th 18, 05:17 PM posted to rec.aviation.soaring
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Default Discus 2 Optimal CG location

Hi Dave,

In normal conditions, I fly mine at station -383 which is what Knauff said was optimal when I bought it in 2002. In strong conditions, where I plan on a lot of high speed cruising, I run at stations -355– -365 to minimize the amount of nosedown trim.

Regards,

Bif “”H7”
  #4  
Old June 25th 18, 08:42 PM posted to rec.aviation.soaring
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Default Discus 2 Optimal CG location

Il giorno domenica 24 giugno 2018 21:05:51 UTC+2, Dave Springford ha scritto:
Can anyone advise the optimal CG location for a D2?

If the 2a and 2b have different optimal locations, I would like to know both.

TIA,

Dave


Not a long experience. I fly my Discus 2b from about 70 hours.
Not so much but in my opinion it fly better with not much backward load.
I fly mine about half the CG exursion (320-330mm).
One time I try it with more tail load but the glider became unstable and I
need to fly it faster in thermal. I really don't like it.
With a neutral CG in very weak condition I fly it at 42 kg/mq and I thermal it
at about 90-95 km/h without problem.
With avarage/good condition I fly it at about 45 kg/mq and I thermal at 105-110 km/h or more depending on how tight I need to turn.
No experience with more load (short runway).
  #5  
Old June 25th 18, 09:18 PM posted to rec.aviation.soaring
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Default Discus 2 Optimal CG location

I fly my 2B about 90% aft empty, but often don't add much tail water when ballasted. Often no tail water, especially in wave. Lead and a brass tail wheel helps with that.

I've found the WB a little unusual though as you need to measure the arms. They are a little different to the manual. I wondered if the wheel is supposed to be jacked somehow during weighing. Does anyone have any ideas about that?


  #6  
Old June 25th 18, 10:29 PM posted to rec.aviation.soaring
Bruce Hoult
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Default Discus 2 Optimal CG location

On Monday, June 25, 2018 at 1:19:00 PM UTC-7, wrote:
I fly my 2B about 90% aft empty, but often don't add much tail water when ballasted. Often no tail water, especially in wave. Lead and a brass tail wheel helps with that.

I've found the WB a little unusual though as you need to measure the arms.. They are a little different to the manual. I wondered if the wheel is supposed to be jacked somehow during weighing. Does anyone have any ideas about that?


Are you measuring with the tail on the ground? The glider should definitely be in something resembling flying attitude, though how that is defined for any particular glider is outside the scope of general W&B instructions. The instructions for any particular glider will be in its maintenance manual.
  #7  
Old June 25th 18, 11:10 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
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Default Discus 2 Optimal CG location

Agreed.

Some ships may be measured with main and tail wheels on the ground, but need a level on the tail boom (with spacers) and THEN measure weights.

Not sure?
Contact those that know, discuss with your local A&P.

Many ways to set up the fuselage, some may measure off structure (spar, wing leading edge, etc.) for data points, some measure "out in space"...,,,,
Read and understand, otherwise, ask a LOT of questions.
  #8  
Old June 25th 18, 11:14 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
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Default Discus 2 Optimal CG location

Oh, and optimal for whom?

Some like mid range, some can deal with/like aft CG.......what is good for you may suck for another......

What is your goal?
Straight high speed cruising, tight gusty thermaling, away from stall/spin, wet, dry, etc.....

I have no clue on a Discus, but others will want to know your "idea" of optimal......
  #9  
Old June 25th 18, 11:20 PM posted to rec.aviation.soaring
Charlie M. (UH & 002 owner/pilot)
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Default Discus 2 Optimal CG location

Sooooo.....your aft heavy bits drag the CG aft.....thus may be no need for aft water ballast normally.

I am a bit below "pilot weight" in my normal glass single seaters.
The owner ballasts to his weight, up to me to keep within CG limits.
Most of this is in ASW/ASG ships.
  #10  
Old June 25th 18, 11:35 PM posted to rec.aviation.soaring
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Default Discus 2 Optimal CG location

On Tuesday, 26 June 2018 09:29:27 UTC+12, Bruce Hoult wrote:
On Monday, June 25, 2018 at 1:19:00 PM UTC-7, wrote:
I fly my 2B about 90% aft empty, but often don't add much tail water when ballasted. Often no tail water, especially in wave. Lead and a brass tail wheel helps with that.

I've found the WB a little unusual though as you need to measure the arms. They are a little different to the manual. I wondered if the wheel is supposed to be jacked somehow during weighing. Does anyone have any ideas about that?


Are you measuring with the tail on the ground? The glider should definitely be in something resembling flying attitude, though how that is defined for any particular glider is outside the scope of general W&B instructions. The instructions for any particular glider will be in its maintenance manual.


Of course it is weighed in the correct SH specified attitude.
 




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