I've always wanted to explore the properties of this unique, bird-like wing configuration.
The wing is usually sweptback with dihedral over most of the span, but the wing is bent (or cranked) downward near the tips with substantial anhedral.. this bent down portion is usually equipped with control surface, and can serve as both rudder and elevon.
This is essentially splitting an inverted-V tail and putting each half of the inverted V at the wingtips.
This arrangement is not commonly seen... but it's at least a century-old idea.. some examples through history:
1. J.W. Dunne's D.6 tailless monoplane in 1911
2. Fritz Wenk's "Weltensegler" tailless sailplane in 1921.
3. A. Lippisch's Delta IVB and DFS40
4. Blohm & Voss P212 & P215
5. Jack Northrup's N1M
This arrangement is sometimes touted as having many advantages in performance, stability and control.
Some examples in recent ultralight soaring craft with this arrangement were inspired by Richard Miller, a diffuser tip proponent, leading to Bob Trampenau's Sunseed and an experimental prototype of the Fledgling hang glider sporting diffuser tips.
The more modern Exulans hang glider also has a similar arrangement..
And the Stromburg Wing model aircraft group in Germany seems active, with many varieties of Weltensegler-cranked wings being flown.
However, I am puzzled as to why this arrangement remains such a rarity.. What am I missing?
The vulnerability to wing tip damage is sometimes mentioned as a criticism .. but is that it?
Are there inherent disadvantages compared to other tailless aircraft arrangements?