in some cases the aerodynamic reasons for forward sweep are
to simultaneously reduce tip stall and achieve a lift
distribution closer to elliptical. Try it on Liftroll.xls.
The practical problem with forward sweep is that, under load,
wing bending makes the tip's angle of attack increase so this
reduces the advantage in tip stall and elliptical lift distribution
gained by the forward sweep. Special tailoring of wing stiffness
has been used to reduce this problem in some aircraft such as the x-29.
For the small sweep seen in gliders there is some potential
in tailoring the pitching moment behavior near stall. However
slightly rearward sweep is what is needed to maintain steady
pitching moment during near-stall flight. Take note of the
comments about "schuman" planform compared to unswept ships'
handling and also NACA report 1339.
So for the small forward sweep seen on gliders you are probaly
left with rear seat visibility as mentioned.
> "Ciurpita, Greg" wrote:
> > I had read that some two seater full-size gliders
> > have slighty forward forward swept wings so that
> > the wings are mounted further back onthe fuselage
> > to improve the visibility in the back seat.
While you're getting a copy of Liftroll you might want to try out
RCHL.xls to find the best launch in various wind shears and speeds.
Liftroll is at: http://homepage.av.com/johnhazel/downloads.html
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