Why has Boeing used mini winglets on the 737-200? I found mini winglets just in B 737-200. What's the differences between mini winglets and the blended ones which Boeing uses in more recent versions?
(picture source)
When originally Richard Whitcomb of NASA developed the winglets, he developed the split winglets with one above and one below as shows in image below:

The one above starts at 0.4x chord from the leading edge. For a test program on KC-135 tanker, which I suppose was first application of the winglets, they used the type of winglets shown in the question:

Conceptually there is no difference in the &quot;mini-winglets&quot; and the &quot;Blended winglets&quot; While I think almost all the wingtip shapes are more or less of same efficacy, I can think of couple of reasons for variations seen among various aircrafts - One is patents taken for some shapes would force other OEMs to come up with different shapes. Second is weight of the wingtip vis-à-vis the reduction in fuel burn. Typically winglets reduce fuel burn by ~3-8% but in some cases, the increased weight can off-set majority of the fuel burn or even prove to be more than compensating for it, especially on shorter hauls. One may be able to make a lighter blended winglet using co-bonded, co-cured composite structure as compared to the short winglet mentioned in the picture which with say bolted joints might end up heavier. I think it would be difficult to say make any generalised comment on this.