Turnabout (National 10) is a 9′ 8″ / 3 m monohull sailboat designed by Harold R.Turner and built by Parker River Marine / J.R.Duplin Marine starting in 1953.
- Designer
- Harold R.Turner
- Builder
- Parker River Marine / J.R.Duplin Marine
- Association
- National 10 (Turnabout)
- # Built
- ?
- Hull
- Monohull Dinghy
- Keel
- Centerboard
- Rudder
- ?
- Construction
- FG
Dimensions
- Length Overall
- 9′ 8″ / 3 m
- Waterline Length
- ?
- Beam
- 5′ 2″ / 1.6 m
- Draft
- ?
- Displacement
- 260 lb / 116 kg
- Ballast
- ?
Rig and Sails
- Type
- Cat
- Reported Sail Area
- ?
- Total Sail Area
- ?
Mainsail
- Sail Area
- ?
- P
- ?
- E
- ?
- Air Draft
- ?
Foresail
- Sail Area
- ?
- I
- ?
- J
- ?
- Forestay Length
- ?
Auxilary Power
- Make
- ?
- Model
- ?
- HP
- ?
- Fuel Type
- ?
- Fuel Capacity
- ?
Accomodations
- Water Capacity
- ?
- Holding Tank Capacity
- ?
- Headroom
- ?
- Cabins
- ?
Calculations
- Hull Speed
- ?
Hull Speed
The theoretical maximum speed that a displacement hull can move efficiently through the water is determined by it's waterline length and displacement. It may be unable to reach this speed if the boat is underpowered or heavily loaded, though it may exceed this speed given enough power. Read more.
Formula
Classic hull speed formula:
Hull Speed = 1.34 x √LWL
A more accurate formula devised by Dave Gerr in The Propeller Handbook replaces the Speed/Length ratio constant of 1.34 with a calculation based on the Displacement/Length ratio.
Max Speed/Length ratio = 8.26 ÷ Displacement/Length ratio.311
Hull Speed = Max Speed/Length ratio x √LWL
- Sail Area/Displacement
- ?
Sail Area / Displacement Ratio
A measure of the power of the sails relative to the weight of the boat. The higher the number, the higher the performance, but the harder the boat will be to handle. This ratio is a "non-dimensional" value that facilitates comparisons between boats of different types and sizes. Read more.
Formula
SA/D = SA ÷ (D ÷ 64)2/3
- SA: Sail area in square feet, derived by adding the mainsail area to 100% of the foretriangle area (the lateral area above the deck between the mast and the forestay).
- D: Displacement in pounds.
- Ballast/Displacement
- ?
Ballast / Displacement Ratio
A measure of the stability of a boat's hull that suggests how well a monohull will stand up to its sails. The ballast displacement ratio indicates how much of the weight of a boat is placed for maximum stability against capsizing and is an indicator of stiffness and resistance to capsize.
Formula
Ballast / Displacement * 100
- Displacement/Length
- ?
Displacement / Length Ratio
A measure of the weight of the boat relative to it's length at the waterline. The higher a boat’s D/L ratio, the more easily it will carry a load and the more comfortable its motion will be. The lower a boat's ratio is, the less power it takes to drive the boat to its nominal hull speed or beyond. Read more.
Formula
D/L = (D ÷ 2240) ÷ (0.01 x LWL)³
- D: Displacement of the boat in pounds.
- LWL: Waterline length in feet
- Comfort Ratio
- ?
Comfort Ratio
This ratio assess how quickly and abruptly a boat’s hull reacts to waves in a significant seaway, these being the elements of a boat’s motion most likely to cause seasickness. Read more.
Formula
Comfort ratio = D ÷ (.65 x (.7 LWL + .3 LOA) x Beam1.33)
- D: Displacement of the boat in pounds
- LWL: Waterline length in feet
- LOA: Length overall in feet
- Beam: Width of boat at the widest point in feet
- Capsize Screening
-
3.3
>2.0: better suited for coastal cruising
Capsize Screening Formula
This formula attempts to indicate whether a given boat might be too wide and light to readily right itself after being overturned in extreme conditions. Read more.
Formula
CSV = Beam ÷ ³√(D / 64)
- Beam: Width of boat at the widest point in feet
- D: Displacement of the boat in pounds
Notes
The National 10 class was originally known as the Turnabout class, built in 1953 by Harold R.Turner as a small wooden single or double handed dinghy class. Many boats were kit built by “do it yourselfers” in their garages or cellars.
The boats were initially built as a junior training boat, although adults enjoy the boats as well. The class has grown mainly in the New England and Northeastern regions of the U.S. Fleets are located in Northern Lake George, New York, Boston, Massachusetts, Rhode Island, Maine and New Jersey.
In 1972 the turnabout class formally changed it’s name to the “National 10 “ class. It also decided to refine the class by approving a new mold, designed as close as possible to the original wooden design. This was accomplished by J.R.Duplin Marine in 1972, with some major improvements, including aluminum spars. The minimum class weight of 215 lbs was increased to 255 lbs. to keep both the older Parker River turnabout, the woodies, and the new Duplin National 10’s more competitive.
Current builder:
JG Marine
67 Skilton La.
Burlington, MA USA
Details can be found on class website.
