Detailed sailboat specifications and datasheets since 2015
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Imperial & Metricboth
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Moody 31 MkI (Fin keel) vs Moody 31 MkI (Twin keel)

Main featuresMoody 31 MkI Fin keelMoody 31 MkI Twin keel
Model
Moody 31 MkI
Moody 31 MkI
Version
Fin keel
Twin keel
Hull type
Monohull
Monohull
Category
Cruising sailboat
Cruising sailboat
Sailboat builder
Moody
Moody
Sailboat designer
Country
United Kingdom
United Kingdom
Construction
Hull and deck: GRP (glass reinforced polyester)
Hull and deck: GRP (glass reinforced polyester)
First built hull
1983
1983
Last built hull
1985
1985
Appendages
Keel : fin without bulb
Twin keel : fin without bulb
Helm
Single tiller (helm wheel in option)
Single tiller (helm wheel in option)
Rudder
Single semi-spade rudder
Single semi-spade rudder
Unsinkable
No
No
Trailerable
No
No
 
Main dimensionsMoody 31 MkI Fin keelMoody 31 MkI Twin keel
Hull length
30’ 8”9.37 m
30’ 8”9.37 m
Waterline length
25’ 5”7.75 m
25’ 5”7.75 m
Beam (width)
10’ 6”3.2 m
10’ 6”3.2 m
Draft
5’1.52 m
3’ 8”1.12 m
Light displacement (MLC)
8752 lb3970 kg
8752 lb3970 kg
Ballast weight
3675 lb1667 kg
3675 lb1667 kg
 
Rig and sailsMoody 31 MkI Fin keelMoody 31 MkI Twin keel
Upwind sail area
558 ft²51.8 m²
558 ft²51.8 m²
Mainsail area
193 ft²17.9 m²
193 ft²17.9 m²
Genoa area
365 ft²33.9 m²
365 ft²33.9 m²
Jib area
215 ft²20 m²
215 ft²20 m²
Stormjib area
75 ft²7 m²
75 ft²7 m²
I
 iFore triangle height (from mast foot to fore stay top attachment)
38’ 6”11.73 m
38’ 6”11.73 m
J
 iFore triangle base (from mast foot to bottom of forestay)
12’ 6”3.81 m
12’ 6”3.81 m
P
 iMainsail hoist measurement (from tack to head)
33’ 6”10.21 m
33’ 6”10.21 m
E
 iMainsail foot measurement (from tack to clew)
11’ 6”3.51 m
11’ 6”3.51 m
Rigging type
Sloop Marconi masthead
Sloop Marconi masthead
Mast configuration
Deck stepped mast
Deck stepped mast
Rotating spars
No
No
Number of levels of spreaders
1
1
Spreaders angle
0 °
0 °
Spars construction
Aluminum spars
Aluminum spars
Standing rigging
1x19 strand wire continuous
1x19 strand wire continuous
 
PerformancesMoody 31 MkI Fin keelMoody 31 MkI Twin keel
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
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.
242
242
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.
42 %
42 %
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.
6.76 knots
6.76 knots
 
Auxiliary engineMoody 31 MkI Fin keelMoody 31 MkI Twin keel
Engine(s)
1 inboard engine
1 inboard engine
Engine(s) power
28 HP
28 HP
Fuel type
Diesel
Diesel
Fuel tank capacity
24 gal91 liters
24 gal91 liters
 
Accommodations and layoutMoody 31 MkI Fin keelMoody 31 MkI Twin keel
Cockpit
Closed aft cockpit
Closed aft cockpit
Cabin(s)
2
2
Berth(s) (min./max.)
4 / 6
4 / 6
Head(s)
1
1
Freshwater tank capacity
35.9 gal136 liters
35.9 gal136 liters
 
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