Home/ Boats/ Thames Marine/ Snapdragon 21/ Performance
Performance

Snapdragon 21 Performance

How the Snapdragon 21 performs on the water — racing handicap, sail-carrying power, stability and comfort.

+ Add to Compare

The Snapdragon 21 is moderately powered for comfortable coastal cruising, with a quick, snappy motion best suited to day sailing.

Hull Speed

The theoretical displacement-mode speed limit — determined by waterline length, not engine or sail power.

5.7 kts
A displacement hull pushes a bow wave whose speed is limited by the waterline length. With a waterline of 18.0′, the Snapdragon 21 tops out around 5.7 knots in displacement mode — after that, the bow wave outruns the hull and resistance climbs steeply.
1.34 × √18.0′ LWL = 5.7 kts

Performance Ratios

Racing handicap, sail-carrying power, stability and comfort — and what each one actually tells you about a day on the water.

SA / Displacement
17.8
Moderate sail power — a capable coastal cruiser, not overpowered.
Comfort Ratio
12.9
Quick, snappy motion — better for day sails and racing than long passages.
Capsize Screening
2.23
Above the 2.0 offshore threshold — best suited for coastal and protected waters.
Hull Speed
5.7kts
Pounds/Inch Immersion
466lbs
Weight needed to sink the hull one inch — loading sensitivity.

Motion & Offshore Suitability

Two ratios that matter most when you're planning passages — how the boat feels in a seaway, and whether the hull geometry is suitable for open ocean.

Comfort Ratio
12.9
Quick, snappy motion — better for day sails and racing than long passages.
Under 20 — Snappy, racing motion
20–30 — Acceptable coastal
30–40 — Good offshore comfort
Over 40 — Very comfortable offshore
Capsize Screening Formula
2.23
Above the 2.0 offshore threshold — best suited for coastal and protected waters.
Under 2.0 — Acceptable for offshore
Over 2.0 — Coastal / protected waters

PHRF Fleet Position

Where the Snapdragon 21 sits on the PHRF handicap spectrum — lower numbers mean faster boats.

Cruiser 150–210
Heavy Cruiser 210–300
Venture 21 252s/nm
South Coast 21 258s/nm

Estimated Speed by Wind

Rough boat speed estimates at different true wind speeds and points of sail — derived from hull speed, SA/D, and displacement, not measured polars.

Point of Sail 6 kts TWS 10 kts TWS 15 kts TWS 20 kts TWS
Close-hauled40–50° 2.3 2.9 3.3 3.4
Close Reach60° 2.8 3.5 4.0 4.1
Beam Reach90° 3.4 4.3 4.9 5.1
Broad Reach120–135° 3.2 4.0 4.5 4.7
Run150–180° 2.5 3.2 3.6 3.7
These are simplified estimates based on hull speed (5.7 kts), SA/D (17.8), and empirical efficiency curves — not instrument-measured polars. Real-world speed varies with sea state, bottom condition, sail trim, and current. Speeds in gold approach hull speed; bold gold means near or at hull speed.

Wind Range & Comfort Envelope

Estimated wind ranges for comfortable sailing on the Snapdragon 21 — based on sail area, ballast, and displacement characteristics.

Ghost
Sweet Spot
Reef
Heavy
0–7 kts 7–20 kts 20–28 kts 28+ kts
Ghosting
0–7 kts
Light air, motor-sailing likely. Need patience and a light genoa.
Sweet Spot
7–20 kts
Comfortable under full sail. Best speed-to-comfort ratio.
Time to Reef
20–28 kts
Time to shorten sail. Reef the main, swap to a working jib.
Heavy Weather
28+ kts
Storm conditions. Storm jib or bare poles. Seek shelter if coastal.

How It Compares

Side-by-side with the boats most often cross-shopped against the Snapdragon 21.

Snapdragon 21 Jouster 21 Westerly Parker 21 Trailer Sailer 21 South Coast 21 Varianta Venture 21
Dimensions
LOA 21.0 21.0 21.0 21.0 21.0 21.0
LWL 18.0 18.3 18.8 14.3 17.7 18.5
Beam 7.3 7.5 8.2 6.9 6.9 6.8
Displacement 2 2 1 2 1 1
Ballast 950 950 800 625 573 400
Sail Area 188 210 220 206
Performance
PHRF 258 252
SA/Disp 17.8 19.9 22.6 20.8
Bal/Disp 41.0 31.3 44.1 26.7
Comfort 12.9 12.2 9.5 14.4
Capsize 2.23 2.31 2.62 2.20
Hull Speed 5.7 5.7 5.8 5.1