The Moody 31 MkI
is a 30’8” (9.37m) cruising sailboat designed by Dixon Yacht Design
(United Kingdom) and Angus Primrose
(United Kingdom). She was built between 1983 and 1985 by Moody
(United Kingdom). The Twin keel
version allows a shoal draft and stability while beaching.
The Moody 31 MkI
is as well listed, on Boat-Specs.com, in Fin keel
version (see all the versions compared
Moody 31 MkI's main features
Moody 31 MkI
Hull and deck: GRP (glass reinforced polyester)
First built hull
Last built hull
Twin keel : fin without bulb
Single tiller (helm wheel in option)
Single semi-spade rudder
Standard public price ex. VAT (indicative only)
Moody 31 MkI's main dimensions
30’ 8”9.37 m
25’ 5”7.75 m
10’ 6”3.2 m
3’ 8”1.12 m
Light displacement (MLC)
8752 lb3970 kg
3675 lb1667 kg
Moody 31 MkI's rig and sails
Upwind sail area
558 ft²51.8 m²
193 ft²17.9 m²
365 ft²33.9 m²
215 ft²20 m²
75 ft²7 m²
I iFore triangle height (from mast foot to fore stay top attachment)
38’ 6”11.73 m
J iFore triangle base (from mast foot to bottom of forestay)
12’ 6”3.81 m
P iMainsail hoist measurement (from tack to head)
33’ 6”10.21 m
E iMainsail foot measurement (from tack to clew)
11’ 6”3.51 m
Sloop Marconi masthead
Deck stepped mast
Number of levels of spreaders
1x19 strand wire continuous
Moody 31 MkI's performances
Upwind sail area to displacement iThe ratio sail area to displacement is obtained by dividing the sail area by the boat's displaced volume to the power two-thirds.
The ratio sail area to displacement can be used to compare the relative sail plan of different sailboats no matter what their size.
Upwind: under 18 the ratio indicates a cruise oriented sailboat with limited performances especially in light wind, while over 25 it indicates a fast sailboat.
222 ft²/T20.66 m²/T
Displacement-length ratio (DLR) iThe Displacement Length Ratio (DLR) is a figure that points out the boat's weight compared to its waterline length. The DLR is obtained by dividing the boat's displacement in tons by the cube of one one-hundredth of the waterline length (in feet).
The DLR can be used to compare the relative mass of different sailboats no matter what their length:
a DLR less than 180 is indicative of a really light sailboat (race boat made for planning), while a DLR greater than 300 is indicative of a heavy cruising sailboat.
Ballast ratio iThe Ballast ratio is an indicator of stability; it is obtained by dividing the boat's displacement by the mass of the ballast. Since the stability depends also of the hull shapes and the position of the center of gravity, only the boats with similar ballast arrangements and hull shapes should be compared.
The higher the ballast ratio is, the greater is the stability.
Critical hull speed iAs a ship moves in the water, it creates standing waves that oppose its movement. This effect increases dramatically the resistance when the boat reaches a speed-length ratio (speed-length ratio is the ratio between the speed in knots and the square root of the waterline length in feet) of about 1.2 (corresponding to a Froude Number of 0.35) . This very sharp rise in resistance, between speed-length ratio of 1.2 to 1.5, is insurmountable for heavy sailboats and so becomes an apparent barrier. This leads to the concept of "hull speed".
The hull speed is obtained by multiplying the square root of the waterline length (in feet) by 1.34.
Moody 31 MkI's auxiliary engine
1 inboard engine
Fuel tank capacity
24 gal91 liters
Moody 31 MkI's accommodations and layout
Closed aft cockpit
4 / 6
Freshwater tank capacity
35.9 gal136 liters
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