Construction materials

Like to find out more about the relative pros and cons of the different materials used to build boats? Below we have compiled a list of information on traditional wood, modern wood/epoxy, aluminium and steel construction organized by keyword and including the advantages and disadvantages for each category.

All wood

Wooden boats are traditionally constructed by laying planks over a skeleton of frames and stringers. A 12 m (40 ft) vessel would typically have frames of 30-35 mm at 300 mm intervals and planks of approx. 30 mm

Reference length: 42 ft
Hull weight: approx. 2.5 tonnes
Hull construction cost: approx. EUR 100,000
Person hours to make boat ready for use: approx. 6000

Advantages:
- very solid hull
- large number of frames, stringers and floor timbers
- repairs are relatively easy, as planks can simply be replaced
- high life expectancy, as material degrades very little
- keel usually bolted through hull, so grounding relatively unproblematic
- well insulated, only problem is condensation
- cosy below decks

Disadvantages:
- one-off construction means extremely high production costs
- building your own traditional wooden boat could take years!
- frames, stringers etc. reduce available space below decks
- may not be totally watertight (depends on types of construction and wood used and presence of deposits on hull)
- limited resistance to abrasion if drying out on a stony bottom
- natural wood needs to be protected against sunlight/UV - white paint is best
- limited strength in a collision

Wood/epoxy

Today most wooden boats are built by laying planks of veneer up in a mould, bonding with epoxy and then stiffening the hull with additional stringers and floor timbers (large floor timbers in the keel area).

Reference length: 42 ft
Hull thickness: approx. 20-25 mm
Stringers approx. 60 mm
Stringer spacing: approx. 600 mm
Hull construction cost: approx. EUR 100,000
Hull weight: approx. 2 tonnes
Person hours to make boat ready for use: approx. 6000

Advantages:
- good value for a one-off project, as moulds are relatively simple to produce
- suitable for self-build construction
- diagonally bonded planks make for excellent dimensional stability
- large number of stringers and floor timbers
- absolutely watertight
- lower overall hull weight
- materials degrade very little over time (Stormvogel has been going for more than 30 years)
- well insulated, only problem is condensation (in the Tropics)
- more straightforward to fit out inside, as fittings can be fastened anywhere
- reparable and easy to maintain
- keel usually bolted through hull, so grounding not a particular
problem
- cosy below deck

Disadvantages:
- the price of a perfect surface finish is hard labour!
- limited abrasion resistance when dried out on a stony bottom
- natural wood needs to be protected against sunlight/UV - white paint
is best
- limited strength in a collision

Strip planking/composite

Cedar planks are laid up on moulds and coated inside and out with GRP or strips of veneer.

Reference length: 42 ft
Hull weight: approx. 1.5 tonnes
Hull construction cost: approx. EUR 75,000
Person hours to make boat ready for use: approx. 5500

Advantages:
- good value for a one-off project, as moulds are relatively simple to produce
- suitable for self-build construction
- composite construction gives hull excellent dimensional stability
- large number of stringers and floor timbers
- GRP coating makes exterior skin very durable
- absolutely watertight
- low hull weight
- well insulated
- reparable and easy to maintain
- keel usually bolted through hull, so grounding not a particular
problem
- cosy below deck

Disadvantages:
- the price of a perfect surface finish is hard labour!
- limited abrasion resistance when dried out on a stony bottom
- natural wood needs to be protected against sunlight/UV - white paint is best
- limited strength in a collision

GRP

Fibreglass mat is laminated (by hand or sprayed on) with epoxy resin in a negative mould and the floor and interior are then strengthened to stiffen the hull.

Reference length: 42 ft
Laminate thickness: approx. 6 mm above the waterline/approx. 25 mm in
the keel area
Hull construction cost: ?
Person hours to make boat ready for use: ?

Advantages:
- suitable for large-scale production runs
- interior can be completed easily using same moulding techniques
- perfect surface finish above and below decks
- interior components can be moulded to any desired configuration (e.g. heads compartment)
- easy to maintain
- lower hull weight due to absence of closely packed frames
- insulation usually provided by interior components (i.e. spaces
between interior fittings and hull
- hull repairs usually relatively straightforward provided damage is not too widespread

Disadvantages:
- hull stiffness may sometimes be lacking
- fewer stringers and floor reinforcing members
- bulkheads in newer boats often no longer fully laminated into hull
- strength in a collision may be limited
- distribution of rig and keel loads basic and direct (vibration)
- materials may fatigue
- possibility of osmosis
- grounding can lead to problems if keel is bolted through hull
- limited lifetime (GRP loses flexibility and becomes brittle)

Hard chine steel

Large steel sections are welded together over a small number of frames or a mould. Interior structures are then added to stiffen the hull.

Reference length: 42 ft
Hull thickness : 4 mm above the waterline and 5 mm below
Hull weight: approx. 4 tonnes
Hull construction cost: approx. EUR 40,000
Person hours to make boat ready for use: approx. 4500

Advantages:
- relatively inexpensive even for self-build construction
- no problems with grounding
- high strength in a collision
- high local strength
- impacts can be absorbed in the form of dents
- material does not fatigue over time
- will last almost forever
- no problems with distribution of rig and keel loads
- can be repaired easily almost anywhere

Disadvantages:
- smaller steel hulls are relatively heavy
- chines can impair sailing performance
- danger of corrosion means maintenance is essential (especially in the tropics)
- problems with condensation

Round chine steel

Steel plates are welded together over a skeleton of frames and stringers.

Reference length: 42 ft
Hull thickness: 4 mm above the waterline, 5 mm below
Hull weight: approx. 4-5 tonnes
Hull construction cost: approx. EUR 100,000
Person hours to make boat ready for use: approx. 6000

Advantages:
- any shape can be produced
- enormously strong hull
- unbeatable strength in a collision
- no problems with grounding
- high local strength
- material does not fatigue over time
- can be repaired easily almost anywhere
- will last almost forever
- no problems with distribution of rig and keel loads

Disadvantages:
- the ultimate in shipbuilding, so more expensive
- self-build construction extremely difficult
- smaller steel hulls are relatively heavy (really practical only for boats of 12m/40ft or longer)
- danger of corrosion means maintenance is essential (especially in the tropics)
- problems with condensation - hull conducts heat and cold readily

Hard chine aluminium

Large sections of aluminium plate are welded together over a small number of frames or a mould. Interior structures are then added to stiffen the hull (Ovni).

Reference length: 42 ft
Hull thickness: 4 mm above the waterline, 5 mm below, 10 mm at keel plate
Hull weight: approx. 2 tonnes
Hull construction cost: approx. EUR 100,000
Person hours to make boat ready for use: approx. 6000

Advantages:
- relatively inexpensive even for self-build construction (Reinke)
- favourable hull weight
- no problems with grounding
- high local strength
- excellent strength in a collision
- impacts can be absorbed in the form of dents
- material does not fatigue over time
- AlMg5 alloy is resistant to corrosion
- hull needs no paint above the waterline
- will last almost forever
- no problems with distribution of rig and keel loads

Disadvantages:
- chines can impair sailing performance
- electrical systems must be installed very carefully due to danger of corrosion/electrolysis
- aluminium will corrode at points of contact with certain materials, so care must be taken with every new fitting
- right antifouling system essential
- problems with condensation - hull conducts heat and cold readily
- interior must be insulated and cold bridges eliminated
- professional skills required for repair

Round chine aluminium

Aluminium plates are welded together over a skeleton of frames and stringers.

Reference length: 42 ft
Hull thickness: 4 mm above the waterline, 5 mm below
Hull weight: approx. 2.6 tonnes
Hull construction cost: approx. EUR 100,000
Person hours to make boat ready for use: approx. 6000

Advantages:
- favourable hull weight
- any shape can be produced
- enormously strong hull
- unbeatable strength in a collision
- no problems with grounding
- high local strength
- material does not fatigue over time
- impacts can be absorbed in the form of dents
- can be repaired
- AlMg5 alloy is resistant to corrosion
- hull needs no paint above the waterline, so is easy to maintain
- will last almost forever
- no problems with distribution of rig and keel loads

Disadvantages:
- the look of natural unpainted aluminium takes some getting used to
- the ultimate in shipbuilding, so more expensive
- self-build construction extremely difficult
- electrical systems must be installed very carefully due to danger of corrosion/electrolysis
- aluminium will corrode at points of contact with certain materials, so care must be taken with every new fitting
- right antifouling system essential
- problems with condensation - hull conducts heat and cold readily
- interior must be insulated and cold bridges eliminated
- professional skills required for repair
Price comparison: a finished Hutting 40 (round chine hull) costs EUR 390,000 in aluminium and only EUR 340,000 in steel