Re: tape affect on LS-1

[j...@oxaero.com]

Thomas,

It's good to hear from you again and to learn that you are interested in getting a better idea of what the tape is doing to your glider.

Yes, your general feeling about what is happening is consistent with the measurements to date, as shown below:

This is the latest and best of the Kiley/Shipp measurements (http://deturbulator.org/kileyshipp.asp).

I have one measurement from 40 to 80 kts and another from 60 to 80 kts.  These are plotted below.

It is important to realize that this technology appears to depend on Molecular/nanoscale events behind the tape that generates a bed of tiny rolling vortices.  So, very small changes make the improvement come or go or change; e.g., wing surface treatment affecting skin friction (more needed behind the tape and less on the tape).  There appears to be a dependence on relative humidity.  Above 80% and the advantage plummets.  The good news is that when it doesn't work, it doesn't hurt.  

I suggest you go to www.deturbulator.org and click on the summary PDF for an overview of the project.

The easiest way to get an idea of what is happening with your glider is to fly parallel with another glider.  The two log files can be analyzed to find the difference.  You only need smooth air, convection is not an issue.  If you have a buddy who will cooperate, you can work out a routine that you can perform anytime the air is smooth and you have altitude to burn.  I have written a manual for this kind of testing.  Click the Files menu link on the website.  I will be glad to do the spreadsheet work for you.

If you haven't already done so, sign up for the email groups.  I post most of my emails to the Participants group.

Best regards,

Jim Hendrix

On Sep 18, 2012, at 5:25 PM, Thomas Hopper <tpho...@gmail.com> wrote:

Hi Jim,

I have not been flying very much for a year but am getting back now. I haven't forgotten about the tape and possible benefits.

On a recent 2.4 hour flight here in NH I found that if I cruised at around 45 knots in no lift that my sink rate would show a familiar reliable rate, like before I put the tape on. But when I  sped up to 50 knots or more that it would show a reliably lesser sink rate. The point that this change occurs seems rather abrupt at this speed change, as I sped up approaching the 50 knot rate, the sink rate would start to respond showing a lessening sink rate, and as I continue to 50 or more knots the sink rate would lessen more enough to even feel a slight change in pitch attitude. I could repeat it again and again. Now there was some thermal lift around and even some ridge lift but I tried heading away from the ridge to eliminate at least that part.

This experience makes me want to do a better job and look for this many more times and try to become more observant of the exact indicated speeds and specific changes in sink rates in particular.

More later, but do you and others experience anything like this Jim?

I find the insects clean off the tape very easily and it is staying in place well with good adhesion.

regards,

-Tom Hopper