View source for Elco 80' PT Boat

'''History'''

The Elco Naval Division boats were the largest in size of the three types of PT boats built for the US Navy used during World War II. The 80-foot (24.4 m) wooden-hulled craft were classified as boats in comparison with much larger steel-hulled destroyers, but were comparable in size to many wooden sailing ships in history. They had a 20 ft 8 in (6.3 m) beam. Though often said to be made of plywood, they were actually made of two diagonal layered 1-inch thick mahogany planks, with a glue-impregnated layer of canvas in between. Holding all this together were thousands of bronze screws and copper rivets. As an example of the strength of this type of construction, the hull of the PT-109 was strong enough that airtight compartments kept the forward hull afloat for hours even after being cut in half by a destroyer. Additionally, damage to the wooden hulls of these boats could be easily repaired at the front lines by base force personnel.
Hull shape was similar to the planing hull found in pleasure boats of the time (and still in use today): a sharp V at the bow softening to a flat bottom at the stern. PT Boats were intended to plane at higher speeds, just like pleasure boats, but with the huge engines and the fuel they required, this rarely happened, even on smooth water. If high-speed operations were attempted on rough water, some hulls simply broke up.[citation needed] In 1943, an inquiry was held by the Navy to discuss planing, hull design, and fuel consumption issues, but no major modifications were made before the end of the war. (Wooden Boat Forum)
With accommodation for three officers and 14 men, the crew varied from 12 to 17, depending upon the number and type of weapons installed. Full-load displacement late in the war was 56 tons.
Early Elco boats had one 20 mm Oerlikon cannon mounted at the stern, and two twin M2 .50 cal (12.7 mm) machineguns mounted in open rotating turrets. These turrets were designed by the same company that would make the Tucker automobile. On the forward deck, some of the early Elco boats had twin-mounted .30 cal (7.62 mm) Lewis machine guns. The primary anti-ship armament was two or four 21-inch (53 cm) torpedo tubes launching Mark 8 torpedoes, which weighed about one ton each. Some carried two to four U.S. Navy Mark 6 depth charges in roll-off stern racks, or mine racks. Later boats mounted one 40 mm Bofors gun aft and four launching racks, two on each beam, for 22.5-inch (57 cm) Mark 13 torpedos. Some PTs later received two eight-cell 5-inch (127 mm) spin-stabilized flat trajectory rocket launchers, giving them 16 rockets and as much firepower for a short time as a destroyer mounting five-inch guns. By war's end, the PT boat had more "firepower-per-ton" than any other vessel in the U.S. Navy. One other addition US Navy PTs had was Raytheon SO type radar, with about a 25 nm range. Since PTs operated mainly at night, having radar gave them an advantage over the enemy in being able to locate and engage them even in zero visibility. Although radar is not specifically a weapon, its use by the PT boats made the other weapons much more effective.
In addition, many boats received ad hoc outfits at advanced bases, mounting such weapons as 37 mm aircraft cannons. One example was Kennedy's PT-109 which was equipped with an Army M3 37 mm anti-tank gun her crew had commandeered, removed the wheels, and bolted to the fore deck. Another similar type of weapon that gained widespread use as the war progressed was the 37 mm Oldsmobile M4 and M9 aircraft automatic cannon. Originally cannibalized from crashed P-39 Airacobra fighter planes on Guadalcanal, and then later obtained by and installed at the boat's Elco and Higgins factories, the M4/M9 cannon had a relatively high rate of fire (125 rounds per minute) and large magazine (30 rounds), making it highly desirable due to the PT boat's ever-increasing need for a larger "punch" to deal effectively with the Japanese daihatsu barges, which were immune to torpedoes due to their shallow draft. By the war's end, most PTs had these weapons.

'''Packard Engines'''

All US PT boats were powered by three 12-cylinder gasoline-fueled engines. These engines were built by the Packard Motor Car Corporation, and were a modified design of the 3A-2500 V-12 liquid-cooled aircraft engine. The 3A-2500 was an improved version of the 2A engine used on the Huff-Daland XB-1 Liberty bomber of World War I vintage. Packard modified them for marine use in PTs, hence the "M" designation instead of "A". (i.e., 3A-2500 then 3M-2500). The three successive versions of these engines were designated as 3M-2500, 4M-2500, and 5M-2500, each of which had slight improvements over the previous version. Their aircraft roots gave them many features of aircraft engines, such as superchargers, intercoolers, dual magnetos, two spark plugs per cylinder, and so on. Packard built the Rolls Royce Merlin aero engine under license alongside the 4M-2500, but with the exception of the PT-9 prototype boat brought from England for Elco to examine and copy, the Merlin was never used in PTs. The 4M-2500s initially generated 1200 hp (895 kW) each, together roughly the same power as a Boeing B-17 bomber. They were subsequently upgraded in stages to 1500-hp (1,150 kW) each, for a designed speed of 41 knots (76 km/h). The final engine version, the Packard 5M-2500, (late 1945) had a larger supercharger, aftercooler, and power output of 1850 Hp. This much power could push the fully-loaded boats at 45 to 50 knots. However, using the older 4M-2500 engines, increases in the weight of the boats due to more weaponry offset the potential increase in top speed. Fuel consumption of these engines was phenomenal; a PT boat carried 3,000 gallons (11,360 liters) of 100 octane avgas. A normal patrol for these boats would last a maximum of 12 hours. The consumption rate for each engine at a cruising speed of 23 knots was about 66 gallons (250 l) per hour (200 gallons (760 l) per hour for all 3 engines). However, at top speed, consumption increased to 166 gallons (628 l) per hour per engine (or 500 gallons [1,890 l] per hour for all 3 engines). At the top design speed of 41+ knots (rarely possible in service, in the absence of hulls and engines in perfect condition), the 3,000 gallons of fuel would be used in only about 6 hours.

'''PTs in Service'''

PTs would usually attack under the cover of night. The deck houses of PT boats were protected against small arms fire and splinters. Direct hits from Japanese guns could and did result in catastrophic explosions with near-total crew loss. They feared attack by Japanese seaplanes, which were hard to detect even with radar, but which could easily spot the phosphorescent wake left by PT propellers. Bombing attacks killed and wounded crews even with near misses. There are several recorded instances of PT boats trading fire with friendly aircraft, a situation also familiar to U.S. submariners. Several PT boats were lost due to "friendly fire" from both Allied aircraft and destroyers.
Initially, only a few boats were issued primitive radar sets. In the Battle of Blackett Strait (where PT109 was lost), only three PTs (the section leaders) had radar, and they were ordered to return to base after firing their torpedoes on radar bearings. When they left, the remaining boats in the section were virtually blind and without verbal orders, thus leading to more confusion. This may have contributed to the events that resulted in PT-109's loss. Later in the war, as more PTs were fitted with dependable radar, they developed superior night-fighting tactics and used them to locate and destroy many enemy targets. The boats would lie in wait to ambush a target from torpedo range (generally about 1000 yards {914 m}), but once their position was given away by the torpedo launch, they would have to lay down a smokescreen from stern-mounted generators, to help conceal their escape from ship-mounted searchlights or seaplane-dropped flares, illuminating them for heavy-caliber guns, which PTs lacked. Depth charges were sometimes used as a last-ditch confusion weapon to scare off pursuing destroyers. Gunboat versions mounted extra armor, though tests showed this was not very effective. A small liferaft was normally mounted on the forward deck, though it was occasionally displaced by guns.
PT boats lacked the refrigerators for meat, milk, butter and eggs of larger ships, so crews depended on the ingenuity of their cook, who might also be quartermaster and signalman, and what he could do with Spam, Vienna sausage, and beans. Crews would trade with other ships for supplies, or sometimes even fish by aiming rifles or tossing grenades into schools of fish.
Originally conceived as anti-ship weapons, PT boats were publicly credited with sinking several Japanese warships during the period between December 1941 and the fall of the Philippines in March 1942. Attacking at night, PT crews may have sometimes failed to note a possible torpedo failure. Although the American Mark 8 torpedo was troublesome and did have problems with porpoising and circular runs, it could and did have success against common classes of targets. The Mark 4 exploder was not subject to the same problems as U.S. submariners were having with their Mark 6s.
After the war, American military interviews with captured veterans of the Imperial Japanese Navy, supplemented by the available partial Japanese war records were unable to verify all the PT boat sinking claims were valid. In some cases this was due in part to the incomplete nature of the Japanese records.
The effectiveness of PT boats in the Solomon Islands campaign, where there were numerous engagements between PTs and capital ships as well as against Japanese shipborne resupply efforts dubbed "The Tokyo Express" in "the Slot", was substantially undermined by defective torpedoes. The Japanese were initially cautious when operating their capital ships in areas known to have PT boats, since they knew how dangerous their own Type 93s were, and assumed the Americans had equally lethal weapons. The PT boats at Guadalcanal were given credit for several sinkings and successes against the vaunted Tokyo Express. In several engagements, the mere presence of PTs was sufficient to disrupt heavily-escorted Japanese resupply activities at Guadalcanal, but this tactical advantage did not last long. Nevertheless, the PT mission in the Solomon Islands was deemed a success.
Throughout World War II, PTs operated in the southern, western, and northern Pacific, as well as in the Mediterranean Sea and the English Channel. Some served during the Battle of Normandy. During the D-Day invasion, PTs patrolled the "Mason Line", forming a barrier against the German S-boats attacking the Allied landing forces. They also performed lifesaving and anti-shipping mine destruction missions during the invasion.


PT gunner mans his twin fifties off New Guinea
Perhaps the most effective use of PTs was as "barge busters". Since both the Japanese in the New Guinea area and the Germans in the Mediterranean had lost numerous resupply vessels to Allied airpower during daylight hours, each attempted to resupply their troop concentrations by using shallow draft barges at night in very shallow waters. The shallow depth meant Allied destroyers were unable to follow them due to the risk of running aground and the barges could be protected by an umbrella of shore batteries. PTs had sufficiently shallow draft to follow them inshore and sink them. Using torpedoes was ineffective against these sometimes heavily-armed barges, since the minimum depth setting of the torpedo was about ten feet (3 m) and the barges only drew five (1.5 m).[1] To accomplish the task, PTs in the Mediterranean and the Pacific (and RN and RCN MTBs in the Med) installed more and heavier guns which were able to sink the barges. One captured Japanese soldier's diary described their fear of PT boats by describing them as, "the monster that roars, flaps it wings, and shoots torpedoes in all directions".[citation needed]
Though their primary mission continued to be attack on surface ships and craft, PT boats were also used effectively to lay mines and smoke screens, rescue downed aviators, rescue shipwreck survivors, destroy Japanese suicide boats, destroy floating mines, and to carry out intelligence or raider operations.
In 1943 in the Solomon Islands, three 77-foot (23 m) PT boats, PT-59, PT-60, and PT-61, were converted into "PT gunboats" by stripping the boat of all original armament except for the two twin .50 cal (12.7 mm) gun mounts, and then adding two 40 mms and four twin .50 cal (12.7 mm) mounts. Lieutenant John F. Kennedy was the first commanding officer of PT-59. After conversion, PT59 participated in evacuating 40 to 50 Marines from Choiseul Island from a foundering landing craft (LCVP) which was under fire from Japanese soldiers on the beach. Later on, in 1944, several 78-foot Higgins PT boats (PT-283, PT-284, PT-285, and PT-282) were converted into this type of gunboat, so PT-59, PT-60, and PT-61 could be transferred back to the training school in Melville, Rhode Island.



*All info simply carried over from Wikipedia*