Tanks
One scale per liquid across every boat: a tank twice the height holds twice as much.
CNB 78
Fuel660 galWater396 galOyster 745
Fuel528 galWater396 gal40 gal of water per berth
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CNB 78vsOyster 745
CNB 78 is 3.9 ft longer than Oyster 745 (5%). CNB 78 is 0.6 ft wider than Oyster 745 (3%). Oyster 745 is the heaviest at 118,955 lb, 13% more than CNB 78.
Anyone with the link sees this comparison.
Key differences
Worked out from the published figures below — arithmetic, not opinion.
- CNB 78 is 3.9 ft longer than Oyster 745 (5%).
- CNB 78 is 0.6 ft wider than Oyster 745 (3%).
- Oyster 745 is the heaviest at 118,955 lb, 13% more than CNB 78.
- Oyster 745 draws the least water, 6.5 ft — 5 ft less than CNB 78.
- Oyster 745 has the lowest air draft, 106.6 ft; CNB 78 stands 5 ft taller.
- Oyster 745 offers up to 5 cabins; CNB 78 at most 4.
At a glance
Dark icons are the standard layout; faded ones are what the larger layout adds.
CNB Yacht Builders
CNB 78
Sailing Monohull
- Length
- 78.5 ft
- Beam
- 20 ft
- Draft
- 11.5 ft
Length : beam 3.9 : 1
Cabins4Headsnot publishedBerthsnot publishedOyster Yachts
Oyster 745
Sailing Monohull
- Length
- 74.6 ft
- Beam
- 19.4 ft
- Draft
- 15 ft
Length : beam 3.8 : 1
Cabins5Headsnot publishedBerths10
Length : beam is length divided by beam — the higher it is, the slimmer the hull. Multihulls read low by nature.
A figure marked with a quote mark was read from the builder's page. Open it for the exact line, the page and the date.
| Model |  CNB Yacht Builders CNB 78 |  Oyster Yachts Oyster 745 |
|---|---|---|
| Overview | ||
| Brand | CNB Yacht Builders | Oyster Yachts |
| Model | CNB 78 | Oyster 745 |
| Generation | Unknown | Unknown |
| Hull type | Sailing Monohull | Sailing Monohull |
| Propulsion | Sail | Sail |
| Production status | In production | In production |
| Production start year | Unknown | Unknown |
| Production end year | Unknown | Unknown |
| Designer | Unknown | Unknown |
| Dimensions | ||
| LOA | 78.5 ft | 74.6 ft |
| Hull length | 75.6 ft | 71.9 ft |
| Beam | 20 ft | 19.4 ft |
| Draft | 11.5 ft | 6.5 ft–15 ft |
| Displacement | 105,601 lb | 118,955 lb |
| Accommodation | ||
| Cabins | 4 | 5 |
| Heads | Unknown | Unknown |
| Berths | Unknown | 10 |
| Performance & Rig | ||
| Main sail | 1,722 ft² | Unknown |
| Jib | Unknown | Unknown |
| Genoa | 1,550 ft² | Unknown |
| Upwind sail area | Unknown | Unknown |
| Downwind sail area | 5,059 ft² | Unknown |
| Engine power | 175 hp | 247 hp |
| Engine count | 1 | 1 |
| Materials | ||
| Hull material | Unknown | GRP |
| Deck material | Unknown | Unknown |
| Mast material | Unknown | Unknown |
| Keel type | Unknown | Unknown |
| Rudder type | Unknown | Unknown |
| Sources |
10 of 11 figures here carry the builder's own words |
7 of 10 figures here carry the builder's own words |
Size, to scale
Each boat's published length and beam seen from above, and its mast height and draft from the side, all drawn on one scale.
Outlines are schematic; the dimensions are the builder's.
Speed, power & tanks
What the builders publish about how fast, how strong and how far — each figure on one scale for every boat.
How they sail, in numbers
Classic yacht-design ratios worked out from each builder's published figures. They compare boats; they don't grade them.
Sail area / displacement
How much sail the boat carries for its weight — its power in light air.
- CNB 7823.4· Performance
- Oyster 745not published: sail area
How it is worked out
sail area (ft²) ÷ (displacement as ft³ of seawater)^⅔
CNB 78: mainsail + genoa, added up
Displacement / length
How heavy the boat is for its waterline length. Lower is lighter and quicker; higher is steadier and roomier.
- CNB 78122· Light
- Oyster 745187· Moderate
How it is worked out
displacement (long tons) ÷ (0.01 × waterline length in ft)³
Ballast ratio
The share of the weight carried in the keel — a rough guide to stiffness, though how deep that weight sits matters as much.
- CNB 7826· Low
- Oyster 745not published: ballast
How it is worked out
ballast ÷ displacement × 100
Comfort ratio
Ted Brewer's measure of how gently a boat moves in a seaway. Higher means a slower, easier motion.
- CNB 7840.2· Heavy offshore
- Oyster 74551.4· Very heavy
How it is worked out
displacement (lb) ÷ (0.65 × (0.7 × LWL + 0.3 × LOA) × beam^1.333), lengths in ft
Capsize screening
A guide from the inquiry after the 1979 Fastnet race: below 2 was taken as suited to ocean passages. It ignores hull shape and where the ballast sits.
- CNB 781.69· Below 2
- Oyster 7451.58· Below 2
How it is worked out
beam (ft) ÷ (displacement as ft³ of seawater)^⅓
Hull speed
Roughly the speed a displacement hull reaches before it has to climb its own bow wave.
- CNB 7811.4 kn
- Oyster 74510.9 kn
How it is worked out
1.34 × √(waterline length in ft), in knots
Most builders publish a light displacement. The ratios were defined on a loaded boat, so every boat here reads a little lighter than a surveyor's figure would — all alike, which keeps them comparable.
Worth adding to this comparison
The boats most like the ones above, by hull form, size and use.
Contest Yachts
Contest 72CSSailing Monohull · 75.7 ft
Oyster Yachts
Oyster 675Sailing Monohull · 69.1 ft
Contest Yachts
Contest 67CSSailing Monohull · 71.2 ft
Hallberg-Rassy
Hallberg-Rassy 69Sailing Monohull · 72.9 ft