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Seller's Description

Bring your offer as owner is motivated and wants to see the boat used again. The boat has been on the hard in San Carlos Seca Marina for about five years. The teak needs attention as well as the decks needs sanding and paint. The hull looks very good with no signs of damage or blisters.

Equipment: Beginning in the bow on the deck and working aft. The bowsprit has a stainless pulpit. There is a hand operated windlass. There are two anchors, a plow type anchor at the bow with 50 feet of 5/15 chain and 100 of 7/16 line. The chain and rode are stored forward of the bow v-birth. (the other anchor is in the stern lazarette with chain and rode, it is a Danforth)

At the forward bulkhead of the cabin is a propane locker with two tanks. On the lid of this locker is a solar panel. The mast is deck stepped made of aluminum. There is a forward hatch into the v-berth. Dorad air vents are located on the both sided of the cabin top into the main saloon.

The stainless-steel rigging is about 25 years old. There are four shrouds on each side of the mast. One at the head that passes through the spreaders, and two others at the juncture of the spreader and the mast. The fourth shroud is not rigged now. It goes at about the spreader level on the forward side of the mast from each side of the boat and is used in conjunction with the inner forestay (cutter stay) which is not installed either. The forestay is fastened at the tip of the bowsprit and the after stay is secured at the stern with a bridle.

There are three halyards reeved on the mast. One for the main, two for jibs. I installed a new heavy duty main sheet track just forward of the main hatch. A whisker pole is a carried on deck for larger jibs. There are two winches mounted on the mast for trimming halyards. All the sheets are run aft to the cockpit where two sheet winches are located. There is also a main sheet winch. The cockpit has two lazarettes. One each side. The boat is steered with a tiller. At the stern is a stainless steel stern pulpit. I installed a battery operated auto-pilot. The batteries (2) are located in the starboard lazarette. A hand operated gusher bilge pump is located directly aft under the tiller. Engine gauges are on the after bulkhead of the cabin, along with the compass and depth sounder. On the stern rails is another solar panel. All running, anchor and masthead lights have operated and are in place. Down below beginning at the bow. There is a chain locker for the anchor rode. There is a v-berth with mattresses and a removable board to access space under berths. There are lockers on each side of the berths and lighting. Next aft, on the port side is a hanging locker with louvered door and on the starboard is a head. The toilet was new several years ago. The shower is not used. There is a sink, also.

The main saloon has two berths with lots of storage under them. There are lockers along both sides of the boat above the berth/settees. I built a drop-down table with a hinged leaf suspended from the starboard forward bulk head. There is a door between the forecastle and the main saloon. Everything is white melamine trimmed with varnished mahogany. On the port side is the galley. A double basin sink with foot operated fresh water pumps and a salt water pump. The stove/oven is propane operated and gimbled. There is an ice chest with access from the counter. There are overhead lockers.

On the starboard is a chart table with the battery meter, the electronics circuit breakers, Danforth switch and other switches. Under it is storage. Behind the stairs and under the cockpit is the Westerbeke engine and drive. I installed a new racor filter and housing. All the thru-hull fittings were replaced in about 2010 with new brass ball valves.

Specs

Designer
Thomas Gillmer
Builder
C. E. Ryder
Associations
?
# Built
150
Hull
Monohull
Keel
Long
Rudder
Transom hung
Construction
FG

Dimensions

Length Overall
31 0 / 9.5 m
Waterline Length
25 0 / 7.6 m
Beam
9 6 / 2.9 m
Draft
4 6 / 1.4 m
Displacement
13,600 lb / 6,169 kg
Ballast
4,400 lb / 1,995 kg

Rig and Sails

Type
Cutter
Reported Sail Area
496′² / 46.1 m²
Total Sail Area
495′² / 46 m²
Mainsail
Sail Area
213′² / 19.8 m²
P
31 5 / 9.6 m
E
13 5 / 4.1 m
Air Draft
?
Foresail
Sail Area
283′² / 26.3 m²
I
36 6 / 11.1 m
J
15 5 / 4.7 m
Forestay Length
39 7 / 12.1 m

Auxilary Power

Make
?
Model
?
HP
?
Fuel Type
?
Fuel Capacity
?
Engine Hours
?

Accomodations

Water Capacity
?
Holding Tank Capacity
?
Headroom
?
Cabins
1

Calculations

Hull Speed
6.5 kn
Classic: 6.7 kn

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

6.47 knots
Classic formula: 6.7 knots
Sail Area/Displacement
13.9
<16: under powered

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.
13.93
<16: under powered
16-20: good performance
>20: high performance
Ballast/Displacement
32.3
<40: less stiff, less powerful

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

32.34
<40: less stiff, less powerful
>40: stiffer, more powerful
Displacement/Length
388.6
>350: ultraheavy

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
388.58
<100: ultralight
100-200: light
200-300: moderate
300-400: heavy
>400: very heavy
Comfort Ratio
38.8
30-40: moderate bluewater cruising boat

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
38.75
<20: lightweight racing boat
20-30: coastal cruiser
30-40: moderate bluewater cruising boat
40-50: heavy bluewater boat
>50: extremely heavy bluewater boat
Capsize Screening
1.6
<2.0: better suited for ocean passages

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
1.59
<2: better suited for ocean passages
>2: better suited for coastal cruising

Notes

From BlueWaterBoats.org:

The Southern Cross 31 is a no nonsense double-ender designed by Tom Gillmer, a professor of naval architecture at the US Naval Academy. The design takes influence from shapes dating back to Colin Archer’s work nearly a century earlier, and the hull in many respects is similar the straight transomed Allied Seawind 30, an earlier Gillmer creation notable for being the first fiberglass boat to circumnavigate the globe. (The Allied Seawind 30 was successful enough to be updated to the Allied Seawind II)

She’s a full keeled sailboat with an outboard rudder and tiller combo, a configuration often praised for its simplicity and the cockpit is quite small, suitable for ocean passages. The cutter rig with bowsprit has 447 sq. ft. of canvas, plenty for its displacement, but being a heavy displacement boat performance is hampered in light airs. Looking on the bright side, the weight gains dividends with a comfortable motion while underway.

Two interior layouts were offered, one with a stand up navigation station over a large locker and one with quarter-berth. The overall construction quality was of a good standard, suitably strong for offshore work. The hulls were built in fiberglass with the topsides cored in Airex foam, while the deck and cabin house was cored in balsa.

In total 130 boats were built between 1976 and 1987, of which a number were sold as hull and deck kits. A slightly larger and similar Gillmer design is the Aries 32 (around 20 of these were built).

Links, References and Further Reading

» Southern Cross Owners Association
» Twenty Small Sailboats to Take You Anywhere by John Vigor, (Ch19, p117-123) an in depth look at the Southern Cross 31. ISBN:978-0939837328
» Ryder Yachts

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