In article u, Swiftel
writes
"Ian Strachan" wrote in message
...
In article , Bob Johnson
writes
.........
It refers to the "easiest way to increase performance" (max L/D I
suppose), contrasting the relative simplicity of adding span compared to
the complexities of adding flaps, new airfoil sections, new
configurations, etc.
.......

ahhh - I like this remark Ian,
wouldn't it have been very wise if the IGC would have had this insight
before they created the 15m class.
Isn't it true that already then, several manufacturers proposed 18m wingspan
instaed of the PIKs 15m?

No, but some of the German manufacturers proposed 16 m, which was so
close to the 15m flapped ships already being built (like the Pik 15)
that IGC decided to stick with 15m.

From memory the date was 1974 or so, when I was the UK delegate to IGC.
It was actually a BGA proposal to IGC that the old standard class rules
(under which the K6 was designed) be left alone, and the new class
should only be span-limited.

It is interesting that when Gerhard Weibal lectured at the BGA weekend
about 5 years ago, he naturally concentrated on huge-span sailplanes. I
therefore asked him in the question period what he considered the most
"cost-effective span". I expected him to say about 20 or 22 metres but
his reply was 17. Pretty close to the 16m I mentioned above, and
fortunately also to 18m which is now a separate IGC class and is
particularly suited to bearing the extra weight of a motor (whereas 15m
is a tad small for a self-launcher in a weak-thermal country).

Or can you tell us why the racing class really got 15 instead of 18m
wingspan?

I have written up my perspective on this for Sailplane and Gliding and
it may be published shortly. But basically as above. 18m was never
discussed by IGC in 1974 although this span was used in older wooden
designs such as the Skylark 3 and 4, etc.

--
Ian Strachan

Bentworth Hall West
Tel: +44 1420 564 195 Bentworth, Alton
Fax: +44 1420 563 140 Hampshire GU34 5LA, ENGLAND