Fair point :-) Assuming, I guess, that the same errors are reflected in whatever device is used for creating the glide calculations.

It really must be Winter...

P3

On Wednesday, January 22, 2014 2:47:08 PM UTC-5, Luke Szczepaniak wrote:
In this instance calculating the polar for one self would actually be

favourable. The polar will be calculated with exactly the same errors

as were present while the sample data was gathered, therefore precise if

not exactly accurate.



Cheers,

Luke



On 01/22/2014 1:25 PM, Papa3 wrote:

I think if you read one of Johnson's articles carefully, you should be able to identify several other key variables/controls that affect results. An obvious one (in addition to weights and CGs mentioned above) is pitot/static system calibration. Just in that area alone, there are probably a half-dozen related areas to consider if you are talking about accuracy to within a percent or two...



P3



On Wednesday, January 22, 2014 12:25:18 PM UTC-5, son_of_flubber wrote:

On Wednesday, January 22, 2014 11:36:38 AM UTC-5, Dave Nadler wrote:



On Tuesday, January 21, 2014 7:14:33 PM UTC-5, son_of_flubber wrote:







Get a high tow into still air...







The likelihood of measuring meaningful data yourself is ZERO.







If I cannot empirically measure an accurate polar by for my body in my glider (wearing my shoes), then how is it possible to use a published polar to accurately predict the performance of my glider (with me in it)?







I can see that measuring my own polar and then using it to calculate my ideal glide slope doubles the source of error.







Factoring out weather, I'm thinking that the biggest source of real world deviation from the idealized polar would be the total weight and the CG, and measuring my glider's polar with me in it factors out that error.







Do glider manufacturers have special inventories of still air for empirically derive polars?