yacht hull outline

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A guide to superyacht hull design

In this guide to superyacht hull design, we break down the specs, must-know information and outline all of the pros and cons of the typical superyacht hull shapes.

Displacement yacht hull design

Fn: up to about 0.42
Average power requirement: 5hp/ton
Prismatic coefficient: 0.56 0.64
LCB: 0.50 0.54 (54 per cent back from waterline entry)
Can be optimised for resistance
Capable of doing hull speed
High displacement over length
Much more forgiving in terms of weight, where the impact on performance is minor
Less initial stability, but more dynamic stability, which equals more comfort
If you want more speed, you have to increase the length
Can carry more fuel, and use less, which equates to more range
Offers the most volume at common interior positions
Engine room smaller less power:weight ratio
Increase stability by reducing weight (if the centre of gravity remains the same) a heavy boat is not necessarily more stable
Interior materials do not need to be lightweight

Semi-displacement (semi-planing) yacht hull design

Fn: 0.6 1.1
Average power requirement: 10hp/ton 40hp/ton
Prismatic coefficient: 0.63 0.68
LCB: 0.53 0.57 (more volume aft)
More buoyancy aft means can keep pushing more power, but this means increased resistance at lower speeds
Resistance heavily depends on the frictional component; reducing weight can minimise it
Flatter, lighter, sharper forebody all more suitable for generating hydrodynamic force on the bottom
Higher initial stability
Larger transom beam means more broaching tendency in a following sea
Less flexibility in weight and weight position
Wider speed range, so lower speeds mean lower engine loading which is not optimal
There is an optimum size going smaller and smaller makes semi-planing hull harder to achieve, and going larger and larger means the weight increases disproportionately
Much superior seakeeping compared to planing boat
Can optimise for higher or lower speeds, but not both
Less volume in hull, especially forward part
Best of both worlds lots of possibilities

Planing yacht hull design

Fn: 1.1 and above, preferably from 2 and up
Average power requirement: 60hp/ton plus
Prismatic coefficient: 0.68 0.76
LCB: 0.58 0.64
Typically monohedral prismatic aft shape constant deadrise
Light displacement
Engine room forms a significant part of hull volume (up to 30-40 per cent)
Weight matters power:weight ratio is critical
Usually very sharp entry angles, although Fn 1.2 to 2 favours LCG forward and blunt entry
Big beam and little weight mean extreme initial stability
Uncomfortable in certain sea conditions
Friction significant, so if left in the water for a couple of seasons speed will drop
Wavemaking coefficient very low, so frictional resistance is the dominant component
Lots of exotic hull shapes, designed to reduce wetted surface and improve comfort in a seaway
Little effective volume foreship, nothing fits; aft ship all engines
Dynamic stability is a big factor, and can limit what is possible
Speed benefit, and can escape bad weather