On Thursday, December 1, 2016 at 2:32:51 PM UTC+3, Casey wrote:
Just wondering if anyone has insight to computer set up as far as these questions:

1) Glider polars come from new gliders with experienced factory pilot, right. If a glider weighs more now (20-30yrs) since the polar was created does one create a new polar or use the polar in the computer and add ballast in the settings? The added weight could be from more electronics, AD's, or repairs. Would adding more weight to the pilot be correct, however that may take the weight over recommended and don't know how that may effect computer.

2) Does crazing effect wing efficiency like bugs do? Does one guess in air how much bugs percentage is on the wings and set that in the computer?

3) What about a pilot that flys a little sloppy and yaws a little? Would it be beneficial to add a little bug percentage? Or the addition of wing skids?

I know that some of these percentages are minuscule and only the top pilots would know a difference in any bugs, but I would think an average pilot could tell a difference in a significant amount of weight, but not sure how much the computer information would change for glide.

I don't think it matters.

The polar used by the computer is a perfect mathematical parabola. The real glider's polar isn't. It's similar, over some limited speed range, but not exactly the same no matter how new and clean your glider is.

The information you want in most of the flight is "how fast should I fly?". Being too fast or too slow by five knots compared to optimum makes almost no difference. It's close enough.

For final glides ... if you're making a skinny final glide from 8000 ft in a 40:1 glider at MC=0 (60 miles!) then your actual glider being 39:1 or 41:1 makes a difference of arrival height of 200 ft. Headwinds, tailwinds, lift, and sink make a lot more difference than that. Your safety margin should be a lot bigger than that. At realistic MC settings the difference will be smaller.