REFLECTOR: Re: winglet bottoms

[Alan Shaw <wingco@iu.net>]

Al Gietzen wrote:

>  You made a design modification on the version of the wings you provide
> because you believed it didn't make any difference aerodynamically and looked
> better.

Not totally true.  I try to provide what the factory and customers want.  The
173 is "OK" without winglet bottoms for most pilots and situations.  But yes,
low speed control is enhanced with winglet bottoms with the penalty of a few
knots at the top end.  Aerodynamic choices are always a compromise.  I think the
choice is yours in this case.

In the case of the XL there is no choice.  The factory has made it clear that
the bigger plane needs more tail feathers.  That is why they make molded winglet
bottoms for that kit.   I resist adding to the top of the winglet because that
increases the load on the winglet structure exponentially.  That is why I am
building a bottom mold so I can include that in my XL wing sub-assemblies.  The
only reason I don't use Velocities molded part is because I use different
molding and assembly techniques than Velocity.

> I know you didn't mention anything about the standard wing version, but it
> would be quite surprising if the effect would completely go away because the
> wing is a foot or so shorter.

The differences in cord, thickness, camber and weight also come into play.  The
standard wing without winglet bottoms was first built by the Swings and proved
to have good low speed stability and control response.

> Just wondered.

That' fine.

Alan Shaw