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1984 Clark San Juan 21 MKII

Listed
Expired
$4,500 USD

Seller's Description

San Juan-21 MK-II Sailboat $4500 Mostly used in fresh water, stored under cover when out of the water. Condition: Excellent Manufactured: 1984 Mono-hull - Fiberglass Builder: Clark Boat Company Model: MK-II Hull identification number (HIN): CLKE2562M84J Length Overall 21 Length Over All (LOA) 20.50 ft. (6.25m) Waterline Length (LWL) 17.50 ft. (5.33 m) BEAM (width at its widest point) 7 ft. (2.13 m) Weight: 1,250 lbs. (567 kg) Draft (vertical distance between waterline and bottom of the keel): 4.00 ft. (1.22 m) with centerboard down

What is a SJ 21: 1) The SJ 21 is a trailer-able, swing keel sloop. 2) The MK-II has (2) 6’ cockpit benches and a V Berth all with cushions, 3) Vessel sleeps 2 to 4 people 4) The swing keel is 400# low and stable when down. 5) The rig is fractional, the sails are easy to handle and reefs easily. 6) It takes approximately 30 minutes to rig and launch the vessel. 7) The SJ-21 is lively and responsive and does well in light air.

Equipment: What is included with the SJ-21: Brand New Sails: Main/Jib/Spinnaker (plus original sails) Motor Mount Tiller Extension Bar Title for Boat King Galvanized Trailer, No Title, (bought the boat in Oregon, they do not require trailer licenses).

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Specs

Designer
Don Clark
Builder
Clark Boat Company
Association
San Juan 21 Class Accociation
# Built
2600
Hull
Monohull
Keel
Swing
Rudder
?
Construction
FG

Dimensions

Length Overall
20′ 6″ / 6.3 m
Waterline Length
68′ 10″ / 21 m
Beam
22′ 11″ / 7 m
Draft
0′ 11″ / 0.3 m — 13′ 1″ / 4 m
Displacement
1,400 lb / 635 kg
Ballast
400 lb / 181 kg

Rig and Sails

Type
Sloop
Reported Sail Area
193′² / 17.9 m²
Total Sail Area
193′² / 17.9 m²
Mainsail
Sail Area
101′² / 9.4 m²
P
22′ 11″ / 7 m
E
8′ 9″ / 2.7 m
Air Draft
?
Foresail
Sail Area
92′² / 8.6 m²
I
22′ 6″ / 6.9 m
J
8′ 2″ / 2.5 m
Forestay Length
23′ 11″ / 7.3 m

Auxilary Power

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

Accomodations

Water Capacity
?
Holding Tank Capacity
?
Headroom
?
Cabins
1

Calculations

Hull Speed
7.9 kn
Classic: 5.6 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

7.86 knots
Classic formula: 5.6 knots
Sail Area/Displacement
24.7
>20: high performance

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.
24.68
<16: under powered
16-20: good performance
>20: high performance
Ballast/Displacement
28.5
<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

28.5
<40: less stiff, less powerful
>40: stiffer, more powerful
Displacement/Length
116.9
100-200: light

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
116.88
<100: ultralight
100-200: light
200-300: moderate
300-400: heavy
>400: very heavy
Comfort Ratio
8.8
<20: lightweight racing 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
8.77
<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
2.5
>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
2.5
<2: better suited for ocean passages
>2: better suited for coastal cruising

Notes

Clark Boat Co. had previously built a number of One-Design Dinghy’s, but this was the first ‘SAN JUAN’ and a huge success.
Designed displacement was 1250 lbs. but it was found that most ended up at 1400 lbs.
Thanks to Samuel Tricky for providing corrected information for this and number of other boats in this category.

This listing is presented by SailboatListings.com. Visit their website for more information or to contact the seller.

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