How to Buy a Boat – 7 Hull Materials
For those who are wondering how to buy a boat, the first decision is sail or power. Once that’s decided, then there is the choice of boat hull construction, decided by the designer and not the boat builder. For those who are buying a used boat or home boat building, there are many choices. Most modern boats are made of GRP – glass reinforced polyester aka fibreglass. It offers many benefits, but there are disadvantages and there are poorly-built examples on the market. Here, we review 7 of the wide choice of hull materials available, together with the main pros and cons of each type.
Composite GRP (Basic/Traditional)
This is the most common production material. Older boats used heavier layering (scantlings) – woven and chopped strand glass mat – than modern ones. For: GRP has a good strength to weight ratio, low maintenance requirement, and is cheap for high volume construction. It has moderate repair complexity – minor repairs are easily dealt with by the average home DIY’er. Against: Older compounds can be subject to osmosis, and bleaching in prolonged sunlight. Modern resins are more resistant. Good for: General purposes – e.g. fishing boats, sailing boats, dinghies and even small ships!
This boat hull construction use Kevlar or carbon fibre mat, impregnated with a high performance polyester or epoxy base resin.
For: High strength to weight ratio. Against: Costly to build, requires high-tech (= expensive) repair. Ideal for: Big budgets and high performance.
Composite (Epoxy on balsa or foam core)
A popular construction for one-offs, and also for production models, though foam has now surpassed balsa.
For: Good Strength to weight, cheap and quick to build. Against: Not easy to repair. Major problem if the core is balsa wood and water gets in (a very careful survey needed here). Ideal for: Home build, one off designs.
Composite (wood strip, epoxy coated)
Most often built using cedar strip planks for stiffness, strength and shape. For: Moderate strength to weight, inexpensive and quick build. Against: Moderately complex to repair. Good for: One off and home build projects.
Wood / Timber (traditional build)
After the dugout canoe, the oldest build was timber boat building, with some ‘modern’ variations. A range of planking types: clinker (overlapped), carvel (‘smooth panked’), diagonal (single/double/triple layup). Double or triple diagonal may be oven cured – no longer produced these days.
For: Lovers of wood, low technology. Against: Generally lower strength to weight ratio (except cooked laminate). Increasingly difficult to find craftsmen for repairs, high maintenance requirement, fastenings eventually fail. Ideal for: owners with time and money.
Plywood really kicked off the home-build boat business way back in the early 1950’s. Some smaller designs use the ‘stitch and glue’ technique. There is also a ‘lapstrake’ variation – plywood planking, essentially.
For: Cheap and easy to build, light to moderate strength to weight ratio. Against: Moderate maintenance requirement. Poor quality non-marine plywood may have been used, and there are design constraints. Ideal for home boat building projects.
For: High strength:weight (for builds over 38′-40′), inexpensive and straightforward to build, cheap and low-tech repairs and modifications, very durable. Against: Corrosion issues. Ideal for: Larger boats, one-off designs, home build, larger vessels, even kits.
For: High strength:weight, durable, low maintenance (no painting necessary above water). Against: Specialist builders, repairs and corrosion risk. Ideal for: Those who want higher performance with a durable material.
Rigid inflatable boats have GRP or sometimes aluminium base hulls, with inflatable collars, and are outside the scope of this article.
Whichever hull material you opt for when you buy a used boat (and you probably chose the boat before the material), do get a professional survey (unless of course it’s a low value item to you), or get it checked over by a knowledgeable friend. Many plywood, strip planked and steel boats may have been home-built, with variable quality hidden problems. But watch out – there are many poor examples of professionally constructed GRP boats too, even modern ones.
This was just a short summary of the constructions used for boats. If you are thinking of buying a used boat, or even building a boat, then there are other materials too, some of which offer great value for money.