Detailed sailboat specifications and datasheets since 2015
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Southerly 420

Sailboat specifications

The Southerly 420 is a 42’2” (12.86m) cruising sailboat designed by Humphreys Yacht Design (United Kingdom). She was built between 2010 and 2017 by Northshore (United Kingdom).

The Southerly 420 has also been marketed as Southerly 435.

Southerly 420's main features

Model
Southerly 420
Hull type
Monohull
Category
Offshore cruising sailboat
Sailboat builder
Sailboat designer
Sailboat range
Country
United Kingdom
Construction
GRP (glass reinforced polyester):
Single skin bottom, sandwich sides and deck: fiberglass vinylester vacuum bagged
First built hull
2010
Last built hull
2017
Appendages
Lifting keel : swing keel
Helm
Single helm wheel
Rudder
Twin spade rudders
Unsinkable
No
Trailerable
No
EC design category
 iThe CE design category indicates the ability to cope with certain weather conditions (the sailboat is designed for these conditions)

A: Wind < force 9, Waves < 10m
B: Wind < force 8, Waves < 8m
C: Wind < force 6, Waves < 4m
D: Wind < force 4, Waves < 0,5m
A
Standard public price ex. VAT (indicative only)
About 
459 000 €
 (2017)

Southerly 420's main dimensions

Hull length
42’ 2”12.86 m
Waterline length
36’ 6”11.11 m
Beam (width)
13’ 2”4.03 m
Draft
8’ 11”2.72 m
Draft when appendages up
2’ 10”0.84 m
Mast height from DWL
61’ 6”18.73 m
Light displacement (MLC)
26015 lb11800 kg
Ballast weight
7782 lb3530 kg

Southerly 420's rig and sails

Upwind sail area
786 ft²73 m²
Downwind sail area
1206 ft²112 m²
Mainsail area
463 ft²43 m²
Jib area
323 ft²30 m²
Gennaker area
743 ft²69 m²
Rigging type
Sloop Marconi 9/10
Mast configuration
Deck stepped mast
Rotating spars
No
Number of levels of spreaders
2
Spreaders angle
Swept-back
Spars construction
Aluminum spars
Standing rigging
1x19 strand wire

Southerly 420'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.
152 ft²/T14.08 m²/T
Downwind 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.
233 ft²/T21.61 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.
244
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.
30 %
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.
8.09 knots

Southerly 420's auxiliary engine

Engine(s)
1 inboard engine
Engine(s) power
53 HP
Fuel type
Diesel
Fuel tank capacity
76.1 gal288 liters

Southerly 420's accommodations and layout

Cockpit
Center cockpit
Cabin(s)
2
Berth(s) (min./max.)
4 / 6
Head(s)
2
Freshwater tank capacity
144 gal545 liters
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