*Thames Measurement (TM) was created in 1855 as a variation of Builder's Old Measurement by the Royal Thames Yacht Club, and was designed for small vessels, such as yachts. It was originally used for calculating the port dues for yachts and was also used in some early handicapping systems for yacht racing. It continued as a generalized size description of sailing yachts until fairly recently. Though it is expressed in "tons" has little to do with the actual displacement weight of the vessel. The formula is:

TM = ((L - B) × B × B ÷ 2)) ÷ 94 where:: L = Length in feet from the fore side of the stempost to the aft side of the sternpost.; B = Maximum beam in feet.

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TM = ((L - B) × B × B ÷ 2)) ÷ 94 where:: L = Length in feet from the fore side of the stempost to the aft side of the sternpost.; B = Maximum beam in feet.

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TM = ((L - B) × B × B ÷ 2)) ÷ 94 where:: L = Length in feet from the fore side of the stempost to the aft side of the sternpost.; B = Maximum beam in feet.

TM = ((L - B) × B × B ÷ 2)) ÷ 94 where:: L = Length in feet from the fore side of the stempost to the aft side of the sternpost.; B = Maximum beam in feet.

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TM = ((L - B) × B × B ÷ 2)) ÷ 94 where:: L = Length in feet from the fore side of the stempost to the aft side of the sternpost.; B = Maximum beam in feet.

TM = ((L - B) × B × B ÷ 2)) ÷ 94 where:: L = Length in feet from the fore side of the stempost to the aft side of the sternpost.; B = Maximum beam in feet.

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Design No. 140

Click image to enlarge

Plans Download: Free

Specification
LOA (deck)	7.075m	23'2½"
LWL	5.935m	19'5⅝"
Beam	2.365m	7'9⅛"
Draught	1.065 m	3'5⅞"
Headroom	1.700m	5'6⅞"
Displacement	3500kg	7716lbs
Ballast	1200kg	2645lbs
TM*		5 tons
Mainsail	19.578m²	210.74ft²
Staysail	5.560m²	59.85ft²
Jib	6.244m²	67.00ft²
Main Topsail	4.517m²	48.62ft²
Jib Topsail	3.904m²	42.02ft²
Engine	6.7-10kw	9-15 bhp
EU Category B - Offshore

Design No. 140 – Deben 5-ton 7.075m (23'2½") cutter

This boat is a long-keeled traditional cruising sailboat, based on the Deben 4 and 6 tonners. The 4-tonners were originally designed for Whisstocks by William Blake 1936. My father, Claude, designed the 6-tonner in a similar style, in 1949. Over 35 4-tonners were built, and three of the 6-tonners, which were reckoned to be very fast and sea-kindly sailboats.

The Deben 5-Tonner is designed in the same spirit as the original Deben 4-Tonner and 6-Tonner to provide robust “little-ship” performance, with traditional carvel construction on steam-bent timbers (frames).

The accommodation comprises a traditional vee-berth fo’c’sle, with good lockers. An infill piece can be added to make a double for harbour and estuary use. The saloon has two comfortable settee berths, one of which extends aft as a quarterberth – perfect for off-watch sleeping on passage. There is a nice self-contained WC compartment opposite the galley. An oilskin locker is located behind the companionway steps. There is plenty of locker space.

She has a full-length cast iron ballast keel bolted to the backbone structure. Her rig is a modern style gaff topsail cutter, but she could be plain gaff rigged (no topsail) as well. The full size cockpit is watertight and self-draining, well protected and comfortable.

In memory of my father, who commissioned the original Deben 4-Tonner, and designed the 6-Tonner, and whose skill and integrity made these boats what they are, this design is available for free. That is you can download the design for free and build from it. And provided you acknowledge the source and design copyright, you can freely distribute the design.

Support for this design is available by email.

To download the design as it becomes available, simply register and the design will appear in your design portfolio. You don't need to make any purchase. Existing members should just login and the design will have been added to their design portfolio.

A larger study plan of this design is available here. It will open in a new window.

The portrait of Claude Whisstock was painted by John Roberts (clicking the link will take you to his website in a new window).