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PT Boats of WWII
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PT Boats - General
Post a reply to: Hickman Sea Sled
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[StartQuote]
Below is the corresponding legend for the numbers. Sorry for the dark paint job which blots out the details. I really like the earlier dark paint job used by the steam torpedo boats, so I used it instead of the more likely dark gray. 1-Four surface piercing props (another Hickman patent), two left, two right. These props are usually about 20% larger than regular props, so the whole transom is a vicious meat grinder. 2-Side rudder. Only the rudder in the turn is activated (sort of like a canoe paddle or steering board). The other just trails against the vessel. The combination of the side rudders and the transom mounted surface piercing props meant the draft on this 54 footer was just under 3 feet max and usually less since it nicely went up on plane. A comparable regular hard chine boat of this sized usually about 5.5 feet in comparison. 3-The four lift eyes that were an integral part of the internal light commercial steel truss framing. The boats sides with trusses in between were the main supports. All main weights from weapons to engines were directly supported by this steel frame. The skin of the boat was oak under framing with mahogany planking. You could lift a fully loaded (fuel, weapons and people) from a mother vessel directly into the water. I concept very similar to what is now used with RIBs and Naval vessels. 4-Bow launched single torpedo. Original proposal was an 18” Mark VII torpedo. Hickman specifically designed the 1918 C378 for the larger 21” Mark VIII torpedo. This would have moved the tubes breech to about where the gun mount is located (item 5). 5-Base of the Hotchkiss 47mm 3 Pounder. This is the same gun mounted on larger ships to defend against torpedo boat threat. The Navy proposal called for just a 1 pounder (37mm). 6-The helm with 4 throttles. The steering was similar to an automobile with the helmsman seated. 7-Engine compartment for four 350 HP engines that had to be built by Hickman. Navy required these to be bronze instead of the spec’d aluminum engines. This added a great deal of unnecessary weight aft. 8-This is a best guess. Some information on the original proposal suggests just an access hatch, but information on C378 suggest this area was an open, and more typical seated crew station. Despite being overloaded by the bronze engines, the fully loaded C378 had a top speed of 37 knots. During one run in an winter storm with 12-14 foot seas, C378 averaged 34.5 knots which is a speed faster than a destroyer through the same seas. The weight per horsepower at full speed is 40 pounds. The Sea Sled hull design with a somewhat flat trim to about 1 maybe 2 degrees, surface piercing props (always an even number so either 2 or 4) and side rudders were all part of the total package. Unlike normal hard chine boats, spray and bow wake was pretty much non-existent. The shape of the sled made the hull a natural dampening force. One Army observer during WW1 (Army bought these as crash boats) noted that when the sled hit a huge wave and launched the boat up about 30 degrees, he was expecting the boat to come slamming down hard, but instead the boat gradually returned to its previous stable trim. The boats made before and during WW1 did not have the beveled chine, so in high speed hard turns, the Sea Sled had a tendency to “trip”. It was during the design of the follow on aircraft carrying 55 foot sea sled that Hickman came up with the beveled and stepped chine which he submitted for patent in 1922. This really helped with turns.[EndQuote]
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