Lightweight Type Anchors (LWT)
The most common anchor of this class, for smaller vessels, is the "lightweight anchor" (LWT). This anchor is easily recognizable due to the large pivoting fluke areas and the stock being mounted at the crown of the anchor. The most famous of the LWT anchor designs is of course the "Danforth." The "Danforth" name has become synonymous with all lightweight style anchors. So much so, that this entire class of anchors is often referred to as Danforth's regardless of the manufacturer.
The idea behind the Lightweight design was to provide an anchor with good holding characteristics in a small and relatively light weight package that was easy to store aboard a vessel. Richard S. Danforth met this challenge and first tested his original design in 1940.
The design intent was to provide a large fluke surface area relative to the anchor’s weight when compared to other types of anchors. This characteristic of the LWT style anchor provided, when properly set, extremely high holding forces; often to the point where components of the ground tackle system may fail before the anchor drags or breaks out.
The lightweight’s performance, like most modern day anchors, is solely dependent on its ability to dig into the bottom and remain there. During the manufacturing process the fluke angle is critical to provide the best chance for bottom penetration. For your typical sand bottom, that has been found to be ≈32°.
As a testament to this design, since the original patent expired, it has been copied and manufactured by hundreds of companies worldwide in varying degrees of quality.
The Major Players
"Danforth Anchors" The original, now manufactured by Tie Down Engineering, are well regarded in their ability to provide high holding power in your typical sand or mud bottom. In other bottoms such as grass or kelp, rocks, very hard sand, and clay bottoms they are generally regarded as poor performers due to their inability to set quickly, if at all. The use of Hi-Tensile steel in some models, has also provided additional strength in the critical fluke and shank areas.
"Fortress Anchors" have taken the LWT anchor design to the next level. While the Fortress Anchor is almost indistinguishable from the original Danforth to the untrained eye, Fortress Marine has made a number of significant improvements. The Fortress’ fluke angle can be adjusted to match varying bottom conditions, the tripping palms can be modified to assist in setting, and its construction from aluminum-magnesium alloy offers even greater weight savings without sacrificing strength. The Fortress can also be easily disassembled for easy storage if being carried as a second or storm anchor.
The Pro’s and Con’s
- The "LWT Style" anchor is excellent in normal sand or mud bottoms.
- It is light in weight.
- Inexpensive in relation to other designs.
- Very limited ability to set and hold in rock, grass, hard sand, gravel, or clay bottoms.
- Does not reset quickly and easily in wind or current shifts.
While all anchors will break out given the right conditions, such as during large wind veers or during tidal current changes, the Lightweight is no exception.
Another issue of the LWT anchor is when the vessel overrides a partially buried anchor,the anchor line or chain may foul on the exposed stock preventing the anchor from resetting until cleared.
The Danforth Anchor is available in galvanized steel or galvanized high tensile steel. It is available in sizes from 3.5 pounds (1.6 kg) to 190 pounds (86 kg).
The Fortress Anchor is produced in aluminum alloy only. It is available in sizes from 4 pounds (1.8 kg) to 69 pounds (31.3 kg).