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Bohli compass operation



 
 
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  #1  
Old August 30th 15, 05:06 PM posted to rec.aviation.soaring
Jonathan St. Cloud
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Default Bohli compass operation

Was wondering if anyone can describe their personal experiences with a Bohli compass. Did you like it was it easy to use? I read the manual which proclaims one can actually use the compass to center thermals and to cloud fly. From my reading it seems as if you would have to be VERY experienced practiced and current to cloud fly or to use the compass to assist in centering a thermal.
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  #2  
Old August 30th 15, 05:44 PM posted to rec.aviation.soaring
HGXC[_4_]
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Default Bohli compass operation

On Sunday, August 30, 2015 at 12:06:10 PM UTC-4, Jonathan St. Cloud wrote:
Was wondering if anyone can describe their personal experiences with a Bohli compass. Did you like it was it easy to use? I read the manual which proclaims one can actually use the compass to center thermals and to cloud fly. From my reading it seems as if you would have to be VERY experienced practiced and current to cloud fly or to use the compass to assist in centering a thermal.


I have a Bohli and confess that I don't use nearly as much as i should. I fly with an Oudie and use that for my thermaling guide. I can see how it helps keep you right size up in a cloud and believe that was what is was used for by the previous owner.

Dennis
  #3  
Old August 30th 15, 06:01 PM posted to rec.aviation.soaring
Dan Daly[_2_]
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Default Bohli compass operation

On Sunday, August 30, 2015 at 12:06:10 PM UTC-4, Jonathan St. Cloud wrote:
Was wondering if anyone can describe their personal experiences with a Bohli compass. Did you like it was it easy to use? I read the manual which proclaims one can actually use the compass to center thermals and to cloud fly. From my reading it seems as if you would have to be VERY experienced practiced and current to cloud fly or to use the compass to assist in centering a thermal.


Don't know if you're thinking of competition, but from the 13.5 m WGC local procedures:

4.1.2.b Instruments that must be removed from the sailplane
The following instruments shall not be carried on board:
* Bohli, Schanz, KT1 or other gimballed compass
* Turn indicator
* Artificial Horizon
Software artificial horizons integrated with FR (fly compiuters) must indicate in their IGC files that AH function is disabled.

If you are a competitor, perhaps not the best choice (or if you were to rent to a competitor, or sell to one).

  #4  
Old August 30th 15, 06:43 PM posted to rec.aviation.soaring
Jonathan St. Cloud
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Posts: 704
Default Bohli compass operation

Seems a bit outdated rule. First in the US it would be be a violation of the FARs to cloud fly, it would be very unwise and dangerious, every iPhone, iPad, android device has an app with a horizon, do not see those barred from the cockpit nor a way to enforce. As for me getting to a world gliding championship, not on a goal list of mine. My focus is on xc flying. Just thinking one of my favorite flights was also one of my shortest, flew 150 mile triangle using thermal lift while never getting more than 1,500 AGL. Winter flight in Southern Cal.

Most flights are not sancationed competitions, maybe more emphasis should be on having fun XC camps than competitions. Our sport needs more participants.

4.1.2.b Instruments that must be removed from the sailplane
The following instruments shall not be carried on board:
* Bohli, Schanz, KT1 or other gimballed compass
* Turn indicator
* Artificial Horizon
Software artificial horizons integrated with FR (fly compiuters) must indicate in their IGC files that AH function is disabled.

If you are a competitor, perhaps not the best choice (or if you were to rent to a competitor, or sell to one).

  #5  
Old August 30th 15, 06:46 PM posted to rec.aviation.soaring
Dave Nadler
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Posts: 1,184
Default Bohli compass operation

On Sunday, August 30, 2015 at 12:06:10 PM UTC-4, Jonathan St. Cloud wrote:
Was wondering if anyone can describe their personal experiences with
a Bohli compass. Did you like it was it easy to use?


Eons ago I borrowed a glider that had a Bohli. I asked the owner
why the compass acted so oddly, and he said "oh yeah, it needs to be
sprayed with anti-static"!
Seems areas of the top plastic view-plate (with the markings) would
build up charge, and the little indicator ball would be attracted/repulsed
from the charged areas!

Made a really weird jumpy motion while thermalling - quite annoying.

Likely only a problem in dry climates, but it was really not usable...

No idea if they all have this issue or if the materials were improved.

See ya, Dave
  #6  
Old August 31st 15, 01:27 AM posted to rec.aviation.soaring
[email protected]
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Default Bohli compass operation

I have about 500 hours flying a Nimbus 3 in South Africa with a Bohli. They are very nice devices and very accurate - they give virtually none of the turning or acceleration errors that other mechanical compasses have. To use it correctly you have to be fairly prompt to adjust the banking knob based on what you are doing. I found that after about the first 25 hours it got relegated to being a secondary or tertiary instrument as there is much more to be busy with (both in the panel and outside) on an XC flight than the compass. And while I understood the concept of cloud climbing & flying with one I never had the guts to do it with the usually ballasted Nimbus. The one I used was already installed and the installation (which requires a lot of cutting and shaping on the top of the panel) appears to take a lot of work and talent to do neatly. Bottom line: probably not worth the time, effort & expense to install one - but if you had one in place you would not take it out.

Roy
  #7  
Old August 31st 15, 05:16 AM posted to rec.aviation.soaring
[email protected]
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Posts: 91
Default Bohli compass operation

On Sunday, August 30, 2015 at 9:06:10 AM UTC-7, Jonathan St. Cloud wrote:
Was wondering if anyone can describe their personal experiences with a Bohli compass. Did you like it was it easy to use? I read the manual which proclaims one can actually use the compass to center thermals and to cloud fly. From my reading it seems as if you would have to be VERY experienced practiced and current to cloud fly or to use the compass to assist in centering a thermal.


I had one and never found it useful for centering a thermal. Nice compass though and I would agree that using it for staying upright would require significant practice and training.
 




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