What follows is taken from an email message sent out today by
Vicki Cain, the Worlds' meet organizer, regarding sprogs and is my best
interpretation of that email message (passages in blue are lightly edited to
improve understanding).

Dennis Pagen on December 15th sent Vicki an email that contained a chart of the
sprog setting values that he received from the glider manufacturers and that he
was going to use for helping team leaders measure their team's gliders. You can
find Dennis' chart
here. Vicki's email message continues:

Unfortunately many of the sprog settings found in Dennis' document
do not match up with what the reference data originally provided in 2009 by
Christof Kratzner (see
here). These were the basis of the sprog measurements in Laragne 2009, Ager
2010 and Monte Cucco 2011.

My understanding at this point is, that Dennis did not confirm the values that
he received with the DHV/HGMA data base (here
is the link to the English version of DHV database search) and that Dennis has
used the values provided by the manufacturers instead.

Since most competing gliders are in fact truck-tested with the DHV, I then
contacted Hannes Weiniger, head of the DHV technical department, and he was able
to provide us with current sprog data of most all the glider models we might see
competing in Forbes. I got his answer only two days ago.

We have now put all this data into a
Forbes 2013 Sprog Chart. There, in the GREEN COLUMN you will find the sprog
data for every model that has so far been successfully truck (pitch) tested. I
added also the data of models that have been confirmed HGMA truck tested (as far
as known).

Hannes Weiniger also provided a link to the DHV pdf-datasheets where under point
16 you can see the sprog angles for yourself (bigger pair of number for loose VG
inboard/outboard, smaller pair of numbers for tight VG inboard/outboard).

To see the DHV sprog setting values click
here. Type in the manufacturer's name in the appropriate field, click
Search, then click on the certified model, and upon picking a model, click on
top of the window a Datasheet button, which opens the Datasheet pdf link, and
scrolling down to line number 16, you'll find the sprog figures.

What follows is a discussion of what tolerances to use:

What is left to do now – and it is something that I could not
decide on my own – is deciding the sprog measuring tolerance. The DHV argues -
and Moyes would support their point - that a tolerance of 2 degrees per sprog
proved to be too big a safety compromise, and renders the whole sporg measuring
efforts practically worthless.

The DHV then trialed a 1 degree tolerance per sprog against truck tested figures
at their Nationals. This approach seems more reasonable, and experience shows
that gliders still fly satisfyingly well this way. However, manufacturers would
likely want to use this overall 2 degree tolerance margin in a more
sophisticated way.

I consulted with Steve Moyes and Gerolf Heinrichs about this, and Moyes Gliders
for instance does not want the inboard sprogs on our models lowered to as much
as a degree below certification. Their findings from inflight video footage is “
that the inboard sprog rarely engages in flight, but being the much stronger and
stiffer member in the sprog configuration would we the main reason to prevent a
pilot from tumbling in severe conditions.“

For that reason we suggest that manufacturers should have the liberty to lower
the sprogs within a 2 degree overall limit, where no single sprog can be lowered
more than 1.5 degrees below the truck-tested figures. (e.g. : the RS3.5,
certified to 4.65/7.35 could then compete as low as 4.15/6.0 degs, consuming
less than 1.35 degrees on the outboard, and but only 0.5 degrees on the inboard,
and thus staying within the 2 degree overall limitation).

The so-called manufacturer settings, would then turn into what could be called
manufacturer tolerance settings. The truck-tested figures would become the sole
reference base to the glider settings, and unsubstantiated guessed-up prototype
sprog figures would be a thing of the past. As a default - if manufacturers are
not suggesting otherwise that is - we then should go by the 1 degree-per-sprog
rule.

Flip Koetsier <<f.koetsier>>
writes:

The
Forbes 2013 Sprog Chart looks like the document that we have always needed.
Without going into detail about where (and when) the figures in the chart have
been collected, I was rather surprised about differences in sprog angles in the
manufacturers information that Dennis received in the past months and the
figures on the chart. I hope that the organiser and CIVL Hang Gliding
subcommittee (Dennis and Oyvind?) will come to an agreement about this.

Vicki, although your motivations for the 2 degree overall tolerance limit sound
valid (to me), I think that you should know that the CIVL Hang Gliding
subcommittee has agreed (seconded by Jamie Shelden) that all gliders should
comply with a 1 degree per sprog tolerance. Your suggested 2 degree over all
(shared between both sprogs) tolerance puts some "outside sprog angles" below
the 1 degree limits.