Seller's Description
San Juan 21, 1981 Mark 2, Asking $2400. Swing keel, fractional rig.
LOA 21’, Beam 7’, Max. draft 4’, Displacement 1400 lbs.
The SJ 21 is a trailerable boat that is quickly rigged. The 400 lb. centerboard is fully retractable and the hull sits low on the trailer for easy launching.
Sails:
New 135% genoa, older main in good shape, good 110 % jib, older genoa. Very good shape spinnaker.
This boat was last sailed and the spinnaker flown on May 3, 2020.
New swing keel winch. Newly installed forward centerboard slot fairing piece, class-legal. Hull in good condition, and the bottom recently faired. Boat is stored dry on trailer, covered with tarps. Centerboard trunk locking bolt hole area was rebuilt in 2019 with marine plywood, epoxy and fiberglass Control lines led to bridge over companionway. Mainsheet traveler in cockpit. Quick release shackles on mainsheet and vang. Adjustable backstay. Rebuilt companionway hatch. Quarter berth cushions recovered 2018. Trailer with new tires 2018, and spare. Motor not included. It has a swing-up motor mount. Masthead fly. Spinnaker pole, whisker pole, boat hook, paddle, anchor and line.There is an unused electrical panel in the starboard locker. Current Oklahoma title, registration, and bow decals. or phone 405-250-2093
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
- 17′ 5″ / 5.3 m
- Beam
- 6′ 11″ / 2.1 m
- Draft
- 0′ 11″ / 0.3 m — 4′ 0″ / 1.2 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
- ?
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
- 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.
- 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
- 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
- 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
- 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
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 SailingTexas.com. Visit their website for more information or to contact the seller.
