Small boat anchors have developed a bit separately from the first half of the 20th century, with the advent of the "CQR", developed by Geoffrey Ingram Taylor of Scotland in the early 1930s. This design was not symmetrical, and required the use of a bow-roller design to effectively stow it. This is practical for small boats and yachts, but does not scale in a practical manner for large shipping. The CQR is now manufactured by Lewmar. American Richard Danforth invented and developed the "Danforth" pattern in the 1940s, a return to the symmetrical concept but with very large flat plate flukes. This anchor offers very good holding power for its weight (high efficiency) but does not perform well in other respects, meaning that it is not a good general purpose anchor. The original Danforth is still manufactured and sold by Tie Down Engineering in the USA. Peter Bruce of the Isle of Man in the UK developed the claw-type "Bruce" anchor in the 1970s. Bruce Anchor Co has its primary role in the very large anchor business, producing mooring anchors and permanent installation types for heavy industry, such as oilrigs. On the back of this reputation, the Bruce small boat anchor type was initially very successful, and represented some significant improvements over the CQR. It is no longer produced. New generation anchors have come into force since the latter part of the 20th century. The German "Buegelanker" features a simple single flat triangular fluke, with a roll-bar to ensure correct setting. A surprisingly simple design, this has proven more effective than its ancestors. Frenchman Alain Poiraud developed the "Spade" anchor in the 1990s, a huge leap in performance over any types which proceeded it. The Spade was the first anchor to successfully make use of a concave fluke, which provides the greatest efficiency (as opposed to the convex "plow" type of the CQR, or the flat "plate" type of the Danforth). The "Bulwagga" is essentially a modified fluke style anchor which made itself known at the very beginning of the 2000s. Rather than two flukes in a symmetrical configuration, it adds a third for an equilateral triangular arrangement. This concept is an improvement over the Danforth in terms of general purpose usage, but is slightly comparatively inefficient (on account of the fact that one fluke is always unused), and is difficult to stow. New Zealander Peter Smith in the early 2000s took elements of the Spade and other types, and developed unique solutions of his own, in order to design the "Rocna" anchor, a general purpose type which uses a concave fluke, a self-righting roll-bar, and setting skids.