BoatsDiamond 27

Diamond 27

Masthead Sloop · Long Keel w/trans. Hung Rudder · 1963–1966

A masthead sloop with a 50% ballast ratio, built for only three years before the molds were sold to Offshore Yachts

Designed by Alan H. Buchanan, built by Thames Marine Ltd.

LOA
Beam
Draft (max)
Displacement
Ballast
Hull type
Long Keel w/trans. Hung Rudder

Is it for you?

Character

Where this design lands on the numbers a shopper trusts — read straight from her own ratios.

LivelySea-kindly

Her heavy displacement on a narrow beam gives 28 — a moderate, middle-of-the-road motion.

Comfort ratio 28
CoastalBluewater

At 1.69 she sits well under the 2.0 line — a solidly ocean-capable hull for her size.

Capsize screening 1.69
LightHeavy

323 — heavy for her waterline, built to carry stores and ride steadily.

Displacement / length 323
EasygoingPowered-up

14.2 — modest power for her weight; easygoing rather than lively, and happier with a breeze.

Sail area / displacement 14.2
TenderStiff

50% of her weight is ballast — stiff, standing up well to her sails.

Ballast 50%

Built heavy and sea-kindly — a boat made to cross oceans and forgive a rough night.

  • Narrower than ~80% of boats her size on file

Compared with 304 boats of the same type within a quarter of her length.

The record

Full specifications

The complete reference set — tap any figure to switch between metric and imperial.

Dimensions
Weights
Ballast / displacement
50.0%
Rig & sail area
Rig
Masthead Sloop
Ratios
SA / displacement
14.2
Displacement / length
322.6
Comfort ratio
27.6
Capsize screening
1.69
Hull speed
6.0 kn
Pounds / inch immersion
555
Hull
Hull type
Long keel w/trans. hung rudder
Construction
Fiberglass
Production
Years built
1963–1966
Units built
12
Designer
Alan H. Buchanan
Builder
Thames Marine Ltd, Stebbings, Sons

Boats like this, on the water

Nobody has filmed this one — but these are close.

Comparable boats the fleet has on camera: same type, within a quarter of her length. Open the boat, or watch the video — a timestamp means she only appears in passing.

Contessa 267.77 mSame hull family0.5 m shorterA David Sadler-designed long-keel masthead sloop, built in both England and Canada with a 25-year production run
Pearson Yachts-USA Triton8.63 mSame hull family0.4 m longerA Carl Alberg-designed long-keel fractional sloop that pioneered fiberglass cruising and saw international production.
Bristol Yachts 247.49 mSame hull family0.7 m shorterA Paul Coble-designed masthead sloop with a long keel and over 50% ballast ratio for stable coastal cruising
Flicka 207.32 mSame hull family0.9 m shorterA Bruce Bingham-designed cutter with a long keel, originally offered as amateur plans before becoming a production classic
Nor'Sea Marine 278.23 mSame hull familyNear-identical lengthA masthead sloop with a versatile rig and ballast configuration, designed for trailerable offshore cruising
Vancouver 278.23 mSame hull familyNear-identical lengthA Robert B. Harris-designed cutter with a long keel, built across two continents to provide a stiff, comfortable passage

The family

Related models

The designs closest to hers — usually the rest of the builder's range, sometimes the same hull sold under another name.

Keep looking

Nothing filmed of this one yet

Two ways to keep looking — both search what the fleet has actually recorded.

The newsletter

New boats, new stories, from everywhere.

One email from the fleet — boats newly added, videos newly analyzed. No noise.

Report an issue