vessel is moving while dropping the anchor, it may "kite" or "skate" over the bottom due to the large fluke area acting as a sail or wing. The FOB HP anchor designed in Brittany in the 1970s is a Danforth variant designed to give increased holding through its use of rounded flukes setting at a 30° angle. The Fortress is an American aluminum alloy Danforth variant which can be disassembled for storage and it features an adjustable 32° and 45° shank/fluke angle to improve holding capability in common sea bottoms such as hard sand and soft mud. This anchor performed well in a 1989 US Naval Sea Systems Command (NAVSEA) test and in an August 2014 holding power test that was conducted in the soft mud bottoms of the Chesapeake Bay. Bruce or claw anchor This claw-shaped anchor was designed by Peter Bruce from Scotland in the 1970s. Bruce gained his early reputation from the production of large-scale commercial anchors for ships and fixed installations such as oil rigs. It was later scaled down for small boats, and copies of this very popular design abound. The Bruce and its copies, known generically as "claw type anchors", have been adopted on smaller boats (partly because they stow easily on a bow roller) but they are most effective in larger sizes. Claw anchors are quite popular on charter fleets as their percentage set on the first try in many bottom types is very high. They have the reputation of not breaking out with tide or wind changes, instead slowly turning in the bottom to align with the force. Bruce anchors can have difficulty penetrating weedy bottoms and grass. They offer a fairly low holding-power-to-weight ratio and generally have to be oversized to compete with newer types. Scoop type anchors Three time circumnavigator German Rolf Kaczirek invented the Bügel Anker in the 1980s. Kaczirek wanted an anchor that was self-righting without necessitating a ballasted tip. Instead, he added a roll bar and switched out the plough share for a flat blade design. As none of the innovations of this anchor were patented, copies of it abound. Alain Poiraud of France introduced the scoop type anchor in 1996. Similar in design to the Bügel anchor, Poiraud's design features a concave fluke shaped like the blade of a shovel, with a shank attached parallel to the fluke, and the load applied toward the digging end.