On Friday, August 12, 2011 10:58:58 AM UTC-4, Mike the Strike wrote:

Errors in your ASI could account for a good chunk of your problems.

The ASI in the Standard Cirrus uses static air from underneath the wings. That will produce some error. (Dick Johnson mentions this in one of the test reports, I think.)

Your data points are all below expectation, though, so the more likely explanation would be error from other factors. I don't know about yours, but the gelcoat on my Std Cirrus looks pretty rough in some places. Also, if you look at other people's measurements, you'll notice quite an error, so multiple takes are necessary to get more reliable results.

PS.: Have you tried to put tape on the underside of your wing? I hear that'll give you 5 L/D points! ;-)