PT 103 Logo
nc nc nc nc
Elco 103 Class PT Boat Chart House
Elco PT Boat 103 Class Chart House

October 9th 2007, incomplete, details such as the horn, binnacle, and side fixtures are missing.

The following images show dimensions and placement for an Elco 80' PT boat chart house, in particular for an early 103 class. These dimensional images represent a best effort on my part, please confirm dimensions given here for yourself if errors cannot be tolerated. Images are for non-commercial personal use only, please obtain permission for any other use.

The main references used for the chart house were Elco plans, mainly the port and starboard inboard profile framing views for a 103 class, several deck arrangement plans, and a detailed chart house framing plan for PTs 372-383 and 486-563. that has the forward turret moved back. Framing details around the turret (aft of the helm, the after trunk) is part guesswork. Please help if you have additional information such as closeup images of details. I especially need details of the door leading from the bridge to below decks. And please let me know if you see any errors.

The chart house sides were mounted to the top of the coamings. The coamings ran stem to stern, from the front of the chart house sides to the back of the engine hatch. They added strength, helped keep deck wash out, and provided easy installation and field replacement of the houses. At the front, the chart house nose was squared off 1" for mating to a 1.25" x 1.25" L bracket mounted to the deck.

The coamings were 1.75" x 6" mahogany beams tapered 3/8" in on their outside tops. They also had a .375" x 1.5" rabbet cut into the outside tops for insetting the .375" plywood chart house sides. They sat on top of the lower decking. Upper decking thickness varied slightly so coaming height was 5 5/8" (5.625") for boats 103 - 108, 5 11/16" (5.6875") on later boats. Coaming taper started at upper deck level. See an image below for a visual.

According to the chart house plan, the inside of the coamings were 48" out from the boat centerline which gives an outside coaming-to-coaming width of 99.5". With the coamings tapering in as they go up, the chart house width ends up at 99".

The 44" diameter starboard turret was forward of the curved starboard bridge wing on PT's 103 - 196 and 314 - 367. The center of the turret was 8.5" forward of frame 33, or 446.5" from the bow, and 51" starboard of the boat centerline.

Later boats (after 367) had the turret moved back to 24.375" behind frame 33, or 479.375" from the bow. The turret was also tilted 3 degrees forward. A cove was cut into the outside base of the turret to allow additional clearance for the torpedo. Depth of the cove was to 63.75" from the hull centerline, and height was about 28". The chart house top crown (roof camber) became a straight drop of 1" in 3' aft of frame 34. The house was shortened on later boats to 46.5" aft of frame 33, or right past the base of the turret. The starboard bridge wing curve was eliminated and the wing extended to 64.125" out from the boat centerline. The radius of the rounded top at the rear of the bridge wall (that ran behind the turret) was 9".

I notice that the build manual for PT 565-624, see below, states the turret diameter as 48" as opposed to the diameter of 44" for all previous series. I don't have a chart house plan for these later boats so can't verify.

Other construction details, note that the baseline is a horizontal plane located 5.5" below the lowest part of the planked hull:

  • chart house forward point was 1" forward of frame 23, 334" from bow
  • chart house front bottom was squared off for 1" to fit to 1.25" x 1.25" deck-to-house L bracket, and swept back 7"
  • chart house roof camber: 3.5" in 8' 3"
  • roof is parallel to baseline
  • top of roof at centerline is 13' 5 1/4" (161.25") above baseline
  • front of chart house is angled back 45 degrees
  • windshield base top is 10.5" up from chart house roof and angled back 45 degrees
  • front and side window openings were 8" x 16" with a 2" corner radius
  • bridge door to chart house: 18.375" x 48"
  • framing mainly 1" x 1.25" mahogany
  • paneling mainly .375" birch ply

amidships symbol divider

Elco PT Boat 103 Class Chart House Dimensions

Elco PT Boat 103 Class Coaming

amidships symbol divider

The following are selected chart house related sections from the Navy PT boat build manual found at Please note that this manual is a later version than the 103 class, read coverage notes below the title. Details changed even within the same series:

PT 565-624

31 March 1944

NOTE: The Detail Specifications are based on Specifications for Motor Torpedo Boats PT 103 to 138 design No. 80-N-3 (dated 2 January 1942) and addenda thereto (dated 22 February 1943), as prepared by Electric Boat Company, Elco Naval Division, Bayonne, N. J., with the minimum modifications made by the Bureau of Ships to make the hull specifications applicable to PT 565-624 Class.

Detail Specifications For Building Motor Torpedo Boats, March 1944, provides the builders specifications for PT 565-624.


Floor bearers of spruce constitute a part of the framing system, and shall be sided to match the bottom frames, and connected thereto with 5/16 inch plywood gussets, glued and fastened with wood screws. Horizontal bearers and keel posts to be 4 inches molded, with 3 inch diagonal braces on alternate frames in crew's quarters as per plan. Flooring, except in tank compartment and chart house, shall be balsa-core aluminum covered panels having all edges sealed against moisture. Spacers of mahogany shall be fitted to permit easy and complete access to bilges.

Flooring of chart house shall be of 5/8 inch fir plywood, with mahogany bearers, well fastened to longitudinal bulkhead and with headers as required.

Continuous full-length coaming 1 3/4 inches to 1 1/2 by 6 inches and deck shelf 1 1/8 by 9 inches mahogany, shall be through bolted to subshelf below deck beams.


Superstructure shall be of simple form, all straight sided and plumb, except the raked and angled forward end of radio house and bridge shelter.

The trunk above crew's dayroom shall be built with framed-up plywood side and ends, and top only being removable, to permit unshipping fuel tanks. Any tank may be unshipped independent of the other two.

Top shall be molded plastic or fabricated plywood, covered with aeroplane fabric, doped on, and is provided with means of securely bolting to sides and making watertight transverse joints.

It is unnecessary to dismantle turrets in removing either engine or tank hatches.

The radio and chart house shall be constructed in general the same as the after trunk, but shall have permanently fixed top.

Machine gun turret cylinders shall be 48 inches 0. D. and be located as per plan and constructed of molded plastic plywood, with special connections to after trunk and chart house. Top shall be designed to carry government furnished scarf ring gun mount for twin .50 cal. machine guns. Scuppers to deck at low point of base. Firing steps for depressed fire shall be fitted.

House tops shall have heat insulation of Onazote or equal to within about 8 inches of house sides.


Bridge arrangement shall be in accordance with Motor Torpedo Boat PT486 type arrangement. Aperture for sighting radar scope to be provided to starboard of the throttle location, as approved. Throttles to be located to starboard of the steering wheel.

**** Magnetic compasses to be installed in accordance with NY NYK Dwg. No. Sk.-468 (Hull Chg, A-1-(2) 4 June '44 - BuShips ltr. PT-565-624/S24(516f) ****


A wind deflecting airfoil shall be installed over and slightly forward of the steering station.

**** Delete "Airfoil type wind deflector complete with all appurtenances from the vessel." (BuShips ltr. PT565-624/S18(516f) Hull Chg. A-1-(4) 27 July 1944. ****


Watertight doors shall be fabricated of aluminum and plywood, with rubber gaskets and specially designed hinges and quick-operating dogs, located as per plan.


All ports shall be of special type with improved drain pans and scuppers, except in crew's dayroom and chart house sides which shall be fitted with hinged metal ports with integral black-out shutters and equipped with wire mesh insect screens satisfactory to the Supervisor of Shipbuilding. Eliminate windows from forward side of chart house.


Portable insect screens shall be provided to protect all living spaces.

Black-out shutters shall be provided throughout boat, including screens for fixed and hinged windows and ventilators. Screens shall be of solid plywood type, sliding in runners for windows, and under engine room vents, to be combined with spray shields, fitted with drains to deck. Special metal shutter shall be fitted on chart house door. Boots shall be fitted at muffler operating rods at transom. Areas reflecting light near shielded openings shall be painted flat black.


W-1-l. Radio and chart house.-Shall be located forward of the bridge and reached therefrom by a door with fixed window and clamping dog handle bolted on inside. The deck level shall extend inside the chart house on the sides and forward, to form a continuous working table surrounding the floor space. To star board aft there shall be a .50 cal. ammunition locker, opening on deck, but having racks for sub-machine guns on its interior sides. The forward table space shall be reserved for navigation, and navigational equipment, also bookshelf, chart space, and transverse drawers which extend forward to the front of the house itself, having a tray top just under the forward house windows which shall be of fixed type. The port side shall be reserved for all radio and detecting equipment, including a chair against the after bulkhead for the operator. The floor space just forward of the entrance door shall be cut out and hinged as hatch cover, so that the ladder on the bulkhead may extend below the floor and provide a descent to the main floor level below, between the officer's mess and the officer's lavatory partition. The remaining space under the chart room floor, being of low headroom, shall contain the 200-gallon water tank on the forward bulkhead, and the two carbon dioxide tanks for the fire extinguishing system on the after bulkhead. A removable section of flooring between these tanks shall afford access to the bilge. An open arch to starboard shall provide entry to the main passage fore and aft in the boat.

The flooring in the chart house shall be mechanically portable, also a section of the chart house roof, approximately 30 by 54 inches for removal of the potable water tank described above. The flooring shall be fitted for a mat of sponge rubber with ribbed tread.


One voice tube shall be installed from bridge (cockpit) to Radar control station. No calls.



    nc nc