The Navy Lighterage pontoon (NLP) was a type of pontoon developed in World War II by Capt. John N. Laycock

Civil Engineer Corps The Civil Engineer Corps (CEC) is a staff corps of the United States Navy. CEC officers are professional engineers and architects, acquisitions specialists, and Seabee Combat Warfare Officers who qualify within Seabee units. They are responsib ...

(CEC) and used by

United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

Construction Battalions (

Seabee United States Naval Construction Battalions, better known as the Navy Seabees, form the U.S. Naval Construction Forces (NCF). The Seabee nickname is a heterograph of the initial letters "CB" from the words "Construction Battalion". Dependi ...

s) on invasion beaches and shallow harbors or harbors where the facilities had been destroyed or did not exist. It was referred to as the Seabee's "magic box". It used a

Lego Lego (, ; ; stylised as LEGO) is a line of plastic construction toys manufactured by the Lego Group, a privately held company based in Billund, Denmark. Lego consists of variously coloured interlocking plastic bricks made of acrylonitri ...

-like system of pre-cut pre-drilled

angle iron Structural steel is steel used for making construction materials in a variety of shapes. Many structural steel shapes take the form of an elongated beam having a profile of a specific cross section. Structural steel shapes, sizes, chemical comp ...

and

steel plate Steel is an alloy of iron and carbon that demonstrates improved mechanical properties compared to the pure form of iron. Due to steel's high elastic modulus, yield strength, fracture strength and low raw material cost, steel is one of the m ...

and was first assembled into individual boxes that were joined in multiples to construct

docks The word dock () in American English refers to one or a group of human-made structures that are involved in the handling of boats or ships (usually on or near a shore). In British English, the term is not used the same way as in American Engli ...

, causeways,

barges A barge is typically a flat-bottomed vessel which does not have its own means of mechanical propulsion. Original use was on inland waterways, while modern use is on both inland and marine water environments. The first modern barges were pull ...

dry docks Dry or dryness most often refers to: * Rain#Deserts, Lack of rainfall, which may refer to **Arid regions **Drought * Dry or dry area, relating to legal prohibition of selling, serving, or imbibing alcoholic beverages * Dry humor, deadpan * Drynes ...

floating cranes Floating may refer to: * a type of dental work performed on horse teeth * use of an isolation tank * the guitar-playing technique where chords are sustained rather than scratched * ''Floating'' (play), by Hugh Hughes * Floating (psychological phe ...

marine railway A patent slip or marine railway is an inclined plane extending from shoreline into water, featuring a "cradle" onto which a ship is first floated, and a mechanism to haul the ship, attached to the cradle, out of the water onto a slip. The mar ...

s or whatever was needed. Capt. Carl A. Carlson CEC of the War Plans Office came up with the concept of NLPs in 1935,Captain John N. Laycock , NHHC, U.S.Navy Seabee Museum website, Feb. 2020, Port Hueneme, C

/ref> but it was in 1940 that the US Navy looked at the idea more seriously. Development, with testing, began just before the US entered World War II. The

Dieppe Raid Operation Jubilee or the Dieppe Raid (19 August 1942) was a disastrous Allied amphibious attack on the German-occupied port of Dieppe in northern France, during the Second World War. Over 6,050 infantry, predominantly Canadian, supported by a ...

in early 1942 showed that the idea of seizing a port in the face of modern coastal defences was either costly or impossible. The US Navy saw the vital importance of being able to build their own port facilities and to deploy naval construction units trained and dedicated for just that role. Creating the Seabees addressed that issue. Four battalions were tasked as pontoon battalions and five Pontoon Assembly Detachments (PADs) were formed. The US Army soon followed with their own units. The Navy Pontoon opened new avenues of attack. The 2'x 175' sections could be carried on sides of LST's and could land on shallow water beaches. They also were used to form an easy to assemble "in theater" dry dock. The sections LSTs transported hanging on their sides could be used to form the bottom and sides of a dry dock. They were modified to be filled or pumped dry to sink or float as needed. Pontoons were used to make support barges for waterfront cranes. Other barges were motorized, in whatever length and width needed and called Rhinos. The assemblies were nearly unsinkable with the multiple compartments interlocked together. Because they were assembled from standardized pieces they were simple to repair. Seabees could not do their job until they had equipment ashore. Pontoons were run in front of a LCT or LST or they could ferry from offshore.

Construction

The NLPs were constructed of welded steel flotation units that were assembled like Legos, connected by special angle-iron pieces, called stringers. The flotation boxes and stringers were held together by special iron wedge pins. The flotation boxes came in two types: a rectangular basic unit measuring . The majority of NLPs were constructed using these. The second type had one side that was curved or angled to make a bow on the front of NLP barges or a ramp as needed.

References

{{Reflist
"Navy's pin-up Boxes", February 1946, Popular Science
illustrations of NPL units

World War II military equipment of the United States Military bridging equipment Pontoon bridges in the United States Coastal construction Amphibious warfare Logistics Seabees

Construction

See also

References