Boatbuilding Materials

In some parts of the world they still knock down a big tree, axe-shape the trunk and produce a boat.

We do it much differently nowadays. The choice and the variety of widely used DIY boatbuilding materials could be confusing. Your decision in which material to build the hull of your boat is one of the key decisions you need to make. A decision that determines not only the selection of the design, the building process and techniques, the tools used and the skills required, but also the on-going care of your boat, frequency, complexity and costs of the required regular maintenance.

Today, the most popular and widely used DIY (backyard) boatbuilding materials are (in order of popularity):
 (click on the blue text to expand/shrink)

1. Wood
   • Traditional boatbuilding material, widely popular
   • Except for exotic kinds, widely available
   • Reasonable price (except for exotics)
   • Relatively light for its strength
   • More expensive wood may be required for spars (spruce), decks and decoration (teak)
   • Widely available designs
   • Non-magnetic (does not affect the compass), non-conductive
   • Basic skills only required (easy to learn)
   • Fine saw-dust is toxic and a health hazard; wear effective respiratory protection when sanding or similar
   • Simplest tools required for DIY boatbuilding
   • Easy to shape as required
   • Pleasant to touch in natural form
   • Absorbs moisture; rots at 20% moisture
   • Has to be protected by painting/varnishing
   • Looks good varnished; often used for decoration
   • Regular maintenance/repainting required
   • Easy to repair (with basic skills)
   • Main problems rot, humidity (cracked/peeled paint or varnish)
   • Relatively easy to puncture/damage
   • Boat lifespan forever, as parts can be replaced relatively easy
   
   
   
2. GRP (Glass-Reinforced-Plastic, fiberglass)
   • Rather popular
   • At some point considered a "wonder-material", yet today there is a better understanding of its limitations
   • Availability away from population centers questionable
   • High price
   • Heavy material; requires substantial thickness for strength; strength depends on the type of glass fabric used and the quality of the polyester compound
   • Requires masts and other spars from wood/aluminum
   • Non-magnetic (does not affect the compass), non-conductive
   • Basic skills easy to learn, yet may produce sub-standard results
   • High quality products may require expensive equipment (professional workshop and skills)
   • Apart from moulds, simplest tools required for DIY boatbuilding
   • Very easy to shape into any form
   • Could to touch, yet can be good looking (gelcoat)
   • Color included in the gelcoat
   • No painting required
   • Minimal maintenance for as long as the gelcoat is intact
   • Easy to patch; professional help may be required for more extensive work
   • Main problem cracked gelcoat; underneath, fiberglass actually absorbs water and starts delaminating (osmosis)
   • Relatively heavy boat displacement requires a bigger engine, yet provides a smoother ride
   • Lifespan typically 10-15 years; be careful if you buy second hand
   
   
   
3. Aluminum (non-US: aluminium)
   • Great boatbuilding material
   • Not all aluminum is made equal; marine grade aluminum (6063) used in the hull and spars is different from the one used where elements need bending (handrails, bent pipes)
   • Availability away from population centers questionable
   • High price
   • Light and strong
   • Aluminum masts and spars are by far prevalent
   • Non-magnetic (does not affect the compass), highly conductive
   • Specialised metal-working skills and welding equipment required:
     • Argon-protected welding (MIG or TIG); electricity essential; avoid welding in highly humid conditions (impure, porous weld)
     • There is no change in color while welding (like with steel), so you don't know how hot the material is; it takes experience
     • Hot-short material to weld: the weld shrinks and easily deforms the material when cooling; it requires careful preparation of the welding conditions and experience
     • The weld is weaker than the base material
     • Sub-standard welds may be expensive to repair and risky to use
     • High quality welding may require expensive equipment
   • Apart from the specialised aluminum welding tools required, simple metal-working tools required for DIY boatbuilding; much softer and easier to work with than steel
   • In spite of all the above challenges, a wonder boatbuilding material once you learn (everyone can) the aluminum welding skills and get some experience (you can always hire a pro)
   • Easy to shape into any form, yet building a round-bilge hull and bending complex-shaped handrails (pipes) will probably require services of a professional workshop to bend the plates
   • Could in could weather, hot in hot; should be covered from the interior
   • No painting required for protection; painting is purely aesthetic; once painted, it is the paint that you are trying to protect from scratches
   • Minimal to no maintenance required
   • Relatively easy to patch or change any part; yet workshop conditions (electricity, argon gas, MIG or TIG welder) required for any aluminum welding work
   • Main problem electrolysis:
     • use sacrificial zinc anodes to protect
     • avoid any other metal as far as possible, use stainless steel where necessary;
     • electrically isolate all other metals on board
     • possibility of stray currents through the hull should be continuously monitored and prevented
     • deterioration by electrolysis is a very slow process that may take many years to weaken the material, after which the structurally damaged parts must be changed
   • With smaller boats, relatively light hull requires a smaller engine, yet it may cause rough ride on choppy seas, especially with high-speed flat bottomed hulls
   • Lifespan forever, for as long as electrolysis is kept at bay
   
   
   
4. Steel
   • Great boatbuilding material (too heavy for small boats)
   • Largely available everywhere (not as much as wood, though)
   • Reasonable price, much lower than aluminum
   • Immensely strong; much harder than aluminum
   • Aluminum masts and spars (or wooden) required
   • Magnetic (strongly affects the compass); highly conductive
   • Most basic metal-working and welding skills required:
     • The cheapest, widely available welding equipment used
     • The easiest material to weld and produce good welds with basic skills
     • While welding, the heated area changes color to bright red so you can easily judge how hot is the material
     • The weld is actually stronger than the material around it
     • simple metal-working tools required for DIY boatbuilding
   • Easy to shape into any form, yet building a round-bilge hull and bending complex-shaped handrails (pipes) will probably require services of a professional workshop to bend the plates
   • Could in cold weather, hot in hot; should be covered from the interior
   • Detailed sandblasting and high quality painting essential (and not cheap) to protect from rust
   • Regular periodic paint renewal required
   • Relatively easy to patch or change any part; only basic metal-working tools and the simplest welding gear required (electricity essential)
   • Main problem rust:
     • Sandblasting to the bare metal before painting
     • Quality priming and painting essential
     • If rust appears on the hull, usually visible as ugly rusty spots and "leaks"
     • It takes a long time for the rust to do any serious damage, yet when it does, damaged parts must be changed
   • Because of its heavy weight, typically used for larger and very large displacement boats
   • Lifespan forever, for as long as rust is kept away
   • Buying a rusty steel hull cheap may mean you need to spend a fortune removing the rust and re-painting
   
   
   
5. Wood/Epoxy and Wood-Core/Epoxy
   • Two different techniques of work, using similar materials and producing lightweight and immensely strong hulls
     • Wood/Epoxy
       • cold-laminated: strips of wood veneer (Western Red Cedar wood is often used, second lightest after balsa, yet has directional structure) laid in layers diagonally to each other, protected from moisture and glued together with marine grade epoxy
       • optionally, could be covered on outside with a layer of glass-roving saturated with epoxy for extra strength
     • Wood-Core/Epoxy
       • a wood core (often balsa wood is used because it is very light) is covered on outside with a layer of fiberglass roving saturated with marine grade epoxy
       • strength achieved not from the wooden core, but from the sandwich-structure of the two outside glass-epoxy layers; the thicker is the inner core, the further apart are the glass-layers and the stronger is the material
       • not so strong and long-lasting as cold-laminated wood/epoxy, but exceptionally light, preferred for racing boats
       • moisture must not reach the soft wood core
   • lightweight and very stiff
   • perfect for round-bilge designs
   • requires specialized designs (widely available)
   • working with wood requires simple basic tools; working with epoxy and glass roving requires very simple tools; all easy to learn
   • fine wood-dust is toxic and a health hazard; avoid breathing epoxy fumes while working and before it cures; epoxy could irritate eyes and skin; wear effective fume-protective respiratory mask when conditions require; wear light rubber gloves when working with epoxy; small strands of glass and glass dust are sharp, irritating to the skin (wear rubber gloves when handling), serious hazard if inhaled (wear respiratory mask)
   • epoxy is UV-sensitive, should be re-varnished every few years for protection against discoloration
   • fixing a damage should be done with care, to avoid weakening the area
   • main problem abrasion by other hard objects (easy to avoid, unless you run aground)
   • long lifespan
   
   
   
6. Plywood
   • popular with some builders because of the simple and quick building
   • marine grade plywood, rather costly
   • may not be readily available everywhere
   • strong, rather heavy
   • requires specialized designs, hard-chine and multi-chine only
   • the simplest wood-working tools required
   • fine wood dust is toxic and a health hazard; grinding plywood releases toxic chemical fumes; wear quality respiratory mask as required
   • it has to be carefully protected from moisture (especially carefully sealed edges, but also the outside wooden surface)
   • has to be painted or varnished for protection; sometimes the outside is covered with glass roving/epoxy for extra protection and strength
   • main problem moisture, if water breaks through the paint/varnish
   • relatively easy to replace whole sheets if required
   • replacing rotten/damaged parts, the hull can be maintained forever
   
   
   
7. Ferrocement
   • had a period of renewed popularity, now gone
   • cheap material (steel mesh and cement)
   • when properly done, immensely strong
   • very heavy, suitable only for heavier displacement (and slower) boats
   • requires specialized designs
   • the inside iron mesh has to be very carefully protected from moisture
   • has to be painted for protection
   • any modifications requiring through-hull drilling are risky, may result in an excessive damage to the inner mesh and a weaker spot
   • main problem rust of the inner mesh
   
   
   

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