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The following specifications were derived from Elco plans, the Navy build manual, reference books, and the net. I've tried to be accurate but you know how that goes. Please let me know if you find an error or can supply more detailed information, thanks.
For simplicity I use keel for both the keel and stempost. Technically the stempost ends at frame 9 and the keel begins. Depth measurements are to the plans baseline which is a horizontal plane located 5.5" below the lowest part of the planked hull. Measurements along the keel are given in both frame locations and stations. More about frames and stations can be found on the Hull component page.
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Specifications, 1942 ELCO 80' Patrol Torpedo (PT) Boat
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Per the Navy build manual:
Length overall, extreme: 80' 3" (963")
Per Elco plans:
80' (960") to outside of planking from bow point to end of deck at sheer line (with the transom angle, deck centerline would be an additional .5"). Rear guard at the transom extended out an additional 6". See note 1 below this spec table for an explanation of the seeming length of 966" that would not match the manual spec.
942" to the end of the keel.
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20' - 7" (247") beam over planking.
20' - 10 3/4" (250.75") extreme beam at outside of guard.
Max beam located about 365" back from bow.
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73' 4" (880").
This is measured at the designed waterline, or where the water will be with the designed load on the boat.
It is located between station 0 (68") to station 10 (948"). Stations are 88" length divisions along the LWL and are used on the lines plan for cross-sectional lines. See the framing page for details.
The LWL is used to determine amidships on the PT boat.
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508" back from the bow point, or halfway along the LWL.
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8' 9 1/2" (105.5") measured amidships.
This measurement can be confusing since it is measured from the bottom of the keel (minus the planking) to the deck sheer line.
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Max keel depth is located from about station 3 (332") to station 4 (420") at 5.5" above the baseline. There is very little curve between these two stations. The absolute low point is at 368.75", or 2.25" before frame 26. See the image for a visual.
The point where the keel meets the bow is 129" above the baseline.
The point where the keel meets the stern is 12.75" above the baseline, 942" back from the bow.
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4.5" in 20'.
This is the camber (curvature) of the deck.
For example, when the beam of the hull is 20' the deck centerline will be 4.5" higher than the sheer line.
This results in differing heights between the deck centerline and the deck sheer line as the beam changes. The sheer varied slightly to match the designed sheer line.
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Measured from the draft clearance line at frame 69. If you set the boat on a flat surface with a blade on the center prop pointing straight down, this angled line runs along where the prop blade touches the surface, to where the forward part of the hull touches, and ends up being about 20" below the baseline at frame 69.
Per the Navy build manual:
Draft, normal, under 28" propellers: 5' 3/4"
Per other references, plans and books:
5' - 3", 5' - 6" 1945
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51 tons, 61 tons 1945 version
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43 kts, 41kts 1945 version
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3 engines, supercharged Packard V12 model 4M 2500. Based on the Packard 3A-2500 aircraft engine.
1200bhp early WWII, 1350bhp shortly after, 1500 at end of war.
Outboard engines were reversed with V drives, some later boats may have had outboard engines spaced farther apart facing the same way as the center engine.
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Federal Mogul Equipoise.
Center: 28" diameter x 28.5 pitch, right hand.
Outboard: 30" diameter x 30" pitch, right hand.
Pitch = inches traveled per revolution (with no slip), relates to the blades angle to hub.
See also note 2 below this spec table.
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1500 gallons of aviation gasoline in 3 tanks mounted side by side under the chart house. The chart house had a removable roof for tank access.
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259 miles at 35 knots.
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Maximum cruising at 2,000 rpm.
Slow cruising at 1,200 rpm.
Minimum cruising at 800 rpm.
Idle at 600 rpm.
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Max 3,000rpm, 40+ knots
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11, 2 officers and 9 enlisted men, 1945: 17, 3 officers and 14 enlisted men.
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About 200 gallons.
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Note 1:
The four Elco profile framing plans I have show a length of 960" plus 6" for the stern guard projection. But they do not show the bowlight/fairlead. The bowlight/fairlead capped the bow and was squared off on the forward end as seen here on the deck arrangement plan. This would necessitate trimming the point off of the bow or it would stick out past the fairlead. It is the difference between the hull measured up to the point of being planked and still pointy nosed, and the extreme hull length of a finished boat. There are quite a few different length measuring methods and terminology describing the exact points to measure for each. It is almost as confusing as figuring out a specific boat configuration and I wouldn't be surprised if my above logic is wrong.
The shaded Outboard Profile plan shows the bowlight/fairlead but lacks construction detail. It does show frame locations along with the base line, and lines drawn along the deck and keel intersect about where frame 0 would be. The front of the bowlight/fairlead is about 3" behind this point. This accounts for the difference when looking at the plans. Extreme measured length would actually start 3" behind the deck and keel conjuncture at frame 0, and end at 966" when looking at the plans. This, and where exactly midships was, stumpted me for a while so I wanted to mention it for the benefit of any also wondering about the seeming discrepancy.
Note 2:
About the information I've found regarding the government supplied propellers used on PT boats. Many information sources have them with 3 props 30" in diameter. I've also run across information stating that the center propeller was 28". They probably varied as horsepower increased, weight changed, and as each boat was tested. The center prop could of had a smaller diameter because it ran deeper and cavitated less. The propeller blueprint that I bought from www.ptboats.org uses 28" as a diameter. It is dated Febuary 2nd 1943 and marked "PT-103 CLASS".
Per www.speedboatclassics.com:
Center: 28" diameter x 28.5 pitch, right hand
Outboard: 30" diameter x 30" pitch, right hand
Per the Navy build manual, note that this is a later version of the 103 class manual and that there could be typos from the character recognition program used for converting the manual to the web. The draft doesn't match other sources but 5'3" looks right according to the plans:
There shall be 3 aluminum-manganese-bronze right hand turning propellers per vessel. The diameter of the propellers shall not exceed 30 inches. Hub length will not exceed 8 1/2 inches.
and in the SECTION A-1, GENERAL, Principal dimensions. The following data are for information only:
Draft, normal, under 28" propellers: 5' 3/4"
and in SECTION S8, TRIAL REQUIREMENTS:
(a) Propeller test. This test shall be conducted in accordance with instructions issued by the Bureau of Ships for the type boat of each boatbuilder for the purpose of selecting the proper propeller for service conditions. Such a test shall be repeated as conditions of loading or design changes require.
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