On Sat, 08 Jun 2013 16:03:44 -0700, Bill D wrote:

On Saturday, June 8, 2013 4:37:52 PM UTC-6, Ralph Jones wrote:
On Sat, 8 Jun 2013 19:59:19 +0000 (UTC), Martin Gregorie

wrote:



On Fri, 07 Jun 2013 09:04:55 -0700, Charlie Papa wrote:



He was surprised at the challenge the aero tow posed, but learned
the

attitude/speed control, then gentle turns, to steeper ones, and he

positively shone at Dutch Rolls.



Curiosity: what do you mean by "Dutch Rolls"?



I understand a Dutch Roll as meaning the coupled wing rocking and
yawing

instability shown by an aircraft with a vertical tail volume that's a

little too small for stable flight, i.e. the fin moment is too short
and/

or the fin area is too small.



In the context of glider training, it's a shameful misnomer for an

exercise in which you roll alternately left and right while keeping

the nose on a point -- thereby learning to cope with the strong

adverse yaw of long wings.

Thanks. I understand "Rolling on a heading". As you say - a standard ab-
initio glider handling exercise.

http://en.wikipedia.org/wiki/Dutch_roll

The majority of that article covers what I understand by the term.

FWIW its desirable for a competition free flight towline glider to be
just on the right side of borderline Dutch Roll stability because that
maximises its ability to self-centre in lift. The traditional way to set
up a new design is to get it trimmed to a nice glide before you start
cutting pieces off the fin. Once it shows the beginning of a dutch roll
you stick the last piece back on. Then you go home, measure the remaining
fin and make it a nice new one of exactly that size and with a similar
aspect ratio.


--
martin@ | Martin Gregorie
gregorie. | Essex, UK
org |