Do winglets produce thrust?

In article ,
Paul Repacholi wrote:

Bruce Hoult writes:

Winglets reduce induced drag by effectively making the wingspan
longer.

I've never seen anyone argue convincingly that a half a meter of
vertical wingspan does anything that couldn't be done equally well
with an extra half meter of normal wingspan. On the other hand
winglets are worse than span in that they don't produce lift in a
useful direction, and they are harder to make strong and rigid than
ordinary span is.

But the spar does not have to deal with the extra lift on a *long*
moment arm. Well not all of it anyway.

Hmm ... well a deliberately non-lifting horizontal section at the tip
would reduce induced drag as well.


If it wasn't for class rules limiting winspan I don't think anyone
would have winglets.

I wonder what class rules the 744 design has in mind

Terminal gates.

I don't know what excuse bizjets or small turboprops such as the Beech
1900 have. Possibly fashion.

-- Bruce