The Clipper Marine 21, often referred to as the Mark 21, stands as a foundational pillar of the 1970s trailer-sailer movement in the United States. Designed by the legendary William Crealock, this vessel was engineered to be the "everyman’s yacht," prioritizing affordability, ease of transport, and simplified rigging. Launched during the height of California’s fiberglass production boom, the Clipper 21 utilized a lightweight, fractional sloop rig and a versatile swing-keel configuration. This design allowed the boat to be launched from a standard boat ramp and towed by a mid-sized family sedan, a revolutionary concept that democratized sailing for inland enthusiasts. While the builder, Clipper Marine, ceased operations in 1976, the 21 remains a common sight in North American lakes and coastal estuaries, serving as a testament to Crealock’s ability to imbue even a budget-friendly vessel with balanced proportions and reliable tracking.
Klipper 21 Information, Review, Specs

- Make
- Klipper
- Model
- 21
- Builder
- Clipper Marine
- Designer
- William Crealock
- Number Built
- Production Year(s)
- 1971 - 1977
Sailing Performance & Handling
The Clipper Marine 21 is characterized by its light displacement and fractional rig, which provides a responsive, almost dinghy-like feel on the helm. With a displacement of approximately 1,400 pounds and a ballast-to-displacement ratio concentrated in its 450-pound cast-iron swing keel, the boat is decidedly tender in heavy air. It was designed primarily for light-to-moderate wind conditions, where its narrow beam and relatively high sail area-to-displacement ratio allow it to accelerate quickly and plane slightly in downwind gusts.
Handling is simplified by Crealock's "one-line" rudder system, which integrates an uphaul and downhaul into a single control—a feature highly praised in historical marketing materials for its utility in shallow-water navigation. Because the keel can be fully retracted, the boat draws only 12 inches, making it an excellent choice for "gunkholing" or beaching. However, sailors should note that the boat lacks the ultimate stability of its larger siblings, such as the Clipper 30. In a blow, the Clipper 21 requires early reefing to maintain an upright posture and prevent excessive leeway, as the relatively shallow swing keel provides less lateral resistance than a deep fixed keel.
Interior Comfort & Variations
For a 21-foot vessel, the Clipper 21 offers a surprisingly functional, albeit Spartan, interior. The cabin is typically configured with a V-berth forward and two quarter berths extending aft under the cockpit seats. A small area for a portable head and a minimal galley block were standard, though many owners have since customized these spaces.
The most notable variation of this model is the "Flush Deck" (often called the Mark II) versus the standard trunk cabin version. The Flush Deck variant offers a clean, unobstructed foredeck which is ideal for sail handling and sunbathing, but it significantly compromises interior sitting headroom. Conversely, the trunk cabin model provides a more traditional silhouette and slightly more vertical space for those seated below. Throughout its production, the use of teak was minimal to keep costs low, with most interiors featuring molded fiberglass liners and marine-grade vinyl upholstery.
Known Issues & Buyer’s Checklist
Prospective buyers of a Clipper Marine 21 should approach the vessel with an understanding of its age and the "budget" manufacturing techniques of the 1970s.
- Swing Keel Pivot and Cable: The most critical inspection point is the swing keel assembly. The pivot pin can wear the fiberglass trunk over decades, leading to a "keel clunk" or, in extreme cases, structural failure. The stainless steel lifting cable and its winch must be inspected for fraying or corrosion, as a snapped cable can result in the keel slamming down and damaging the hull.
- Deck Delamination: Like many fiberglass boats of this era, the Clipper 21 utilized a balsa or plywood core in some deck sections. Water intrusion through poorly bedded deck hardware often leads to "soft spots." Buyers should walk the deck firmly to check for flexing.
- Mast Step Compression: The mast is deck-stepped, and the compression post—or the structural support beneath it—can settle over time. Check for a "dish" in the cabin top where the mast sits, which indicates a need for structural reinforcement.
- Hull "Oil Canning": Because the hulls were laid up to be light for trailering, the fiberglass is thinner than that of an offshore cruiser. In some cases, the hull may flex or "oil can" when pushed against a trailer bunk or when slamming into heavy chop.
Community & Resources
The Clipper Marine community is largely decentralized but remains active through enthusiast hubs. The most prominent resource is the Clipper Marine Owners Association, which provides a repository of technical manuals and historical brochures. Owners also frequently congregate on broader trailer-sailing platforms to share modifications for the swing-keel mechanism and rigging upgrades.
The Verdict
The Clipper Marine 21 is a classic entry-level cruiser that excels in versatility and ease of ownership. While it is not intended for blue-water passages, its Crealock pedigree ensures a level of grace and balance often missing in other mass-produced trailer-sailers of the same vintage.
Pros:
- Extremely easy to trailer, launch, and rig single-handedly.
- Very shallow draft (1 foot) with the keel retracted allows for exploration of thin waters.
- Predictable handling and good light-air performance.
- Highly affordable entry point into the world of overnight cruising.
Cons:
- Lightweight construction may feel flimsy in heavy weather or choppy seas.
- The swing-keel trunk requires regular maintenance and is a common failure point.
- Minimal interior amenities and restricted headroom, particularly on the Flush Deck model.
Measurements
Construction & Hull
- Construction Material
- Fiberglass
- Hull Type
- Monohull Sailboat
- Keel Type
- Wing
- Rudder
- 1x —
- Ballast
- 410 lbs (Iron)
- Displacement
- 1800 lbs
- Water Capacity
- -
- Fuel Capacity
- -
Dimensions
- Length Overall (LOA)
- 20.87 ft
- Waterline Length (LWL)
- 16.67 ft
- Beam
- 7.25 ft
- Draft
- 4.33 ft
- Max Headroom
- -
- Air Draft
- -
Rig & Sails
- Rig Type
- Fractional Sloop
- P (Main Luff)
- 21.33 ft
- E (Main Foot)
- 9 ft
- I (Foretriangle Height)
- 21.78 ft
- J (Foretriangle Base)
- 8.85 ft
- Forestay Length (est)
- 23.51 ft
- Sail Area
- 192 sqft
Calculations
- Sail Area / Displacement (SA/D) Ratio
- 20.76
- Ballast / Displacement Ratio
- 22.78
- Displacement / Length Ratio (D/L) Ratio
- 173.47
- Comfort Ratio
- 11.08
- Capsize Screening Formula
- 2.38
- Hull Speed
- 5.47 kn