Alongside ‘what size engine do I need, how many feet should my boat be, and what hull form is best?’, ‘what material should my boat be constructed from?’ or words to that effect is one of the most commonly asked questions among prospective boat owners. It’s a great question, and as you might expect, not one with a clear answer. Each material has its strengths and weaknesses, from the timeless grace of a wooden boat, to the brick ****house appeal of aluminum, and the aesthetic superiority of GRP, each material needs to be appraised on its individual merits before you can make a decision on the right option to suit you.
Marine grade aluminum is a proven building block of the marine industry, particularly when it comes to work boats where it has been the go to material of choice for generations. The reasons for this really all stem from one overriding factor: reliability. Whilst wooden and composite hulls require a level of care, maintenance and monitoring that would simply be prohibitive for the ever growing demands of industry; aluminum is a reliable, low maintenance material.
Besides boasting the same properties most people would associate with metals: strong, tough, solid; on top of this aluminum has the distinct advantage of being lightweight, whilst still being cost effective (relative to another light and strong metal like titanium anyway).
Whilst it’s difficult to compare like for like when it comes to the weight of an aluminum hull compared to a composite one, on a smaller vessel you’ll probably find there isn’t a lot in it. A composite hull of comparable strength and rigidity will have a fair degree of reinforcement within it’s laminate, while the internal structure of an aluminum boat could potentially be fairly minimal.
Where aluminum can’t typically compete is in the complexity of hull form it is possible to achieve. A truly fair hull form is challenging to achieve, with the subtle curvature of a soft chine in particular being difficult to achieve once you factor in weld shrinkage and deformation of the hull over time.
To elaborate on the last point; don’t forget the ductility or ‘bendiness’ of aluminum can be both a blessing and a curse; sure a slight kink here and there won’t damage the structural integrity of the hull plating, but it certainly does stand to throw a spanner in the works from a hydrodynamic point of view.
Strength and Resilience
Aluminum really shines in the hands of those who treat their boats with the kind of tough love a stoic parent projects on their child! In other words it can take a bit of a beating!
Over zealous docking maneuvers can be particularly unhealthy for fibreglass and wooden boats, with accidental blows presenting a real risk of cracking and breaching of the hull. No such issue exists with aluminum, where the worst you can expect is a nasty dent. Annoying yes, but at least it won’t sink the boat.
Whilst aluminum has a rugged charm all of its own, particularly when left in its natural unfinished colour, it’s fair to say it doesn’t suit everyone’s tastes. As I mentioned above it’s not possible to ‘mould’ aluminum, so achieving the sexy curves of composite boats is out of the question.
Whilst aluminum hulls are certainly functional and practical in most ways, the same cannot be said for user comfort. The limitations on sheet aluminum that prevent it being formed into a fair hull form, also mean that the ride is usually a bumpier one. If the structure is particularly lightweight, then it’s great news for fuel economy and speed, but bad news for comfort because the vessel will be more likely to bounce up and down rather than slice through the waves.
In many ways aluminum is a great material to work with, it’s relatively soft and malleable, and easy to cut, bend, and drill. This is all great news from a maintenance perspective because dents can be easily knocked out, scratches can be buffed out, and holes can easily be repaired; whether crudely with riveted on plates or more professional welded repairs.
In theory aluminum doesn’t require surface finishing of any kind, so if you wanted to have a bare, unpainted hull, you could! However over long periods of exposure, the salt in the sea water will cause the aluminum to oxidise and corrode, so a bare hulled aluminum boat should be removed from the water, cleaned and stored in something like a ‘dry stack’ facility when not in use.
More commonly aluminum hulls are painted with an epoxy primer, surface coat, and antifoul below the waterline. Touch ups are of course possible if necessary, but antifouling needs to be reapplied every 2 years or so, just as it would need to be on a composite hulled boat.
Aluminum boat building isn’t a particularly cheap process, especially when it requires an army of coded welders to do the job, but for building one off designs it works out a lot cheaper than a fibreglass moulding which requires expensive mould making – suited to the repeatability of a run of production vessels.
Bottom line – if you’re looking to have a custom vessel built, aluminum is the material for the job.
Composites (Glass Fibre and Carbon Fibre)
Since the mid 1950s one material has reigned supreme in the commercial yacht building industry: a composite of plastic resin and reinforcing material, either in the form of glass or carbon fibres.
Composites, especially the more widely available and cost effective fibreglass (GRP), more or less rewrote the recipe for boat building overnight when it was first introduced. Suddenly the laborious and expensive craftsmanship required to build a wooden boat was out (albeit replaced with an entirely new type of craftsmanship) and in came stunning, curvaceous vessels, that could be produced in high volumes.
The technology around composites continues to improve and develop, with the next generation of epoxy resins and carbon nanotubes appearing at the high tech end of the industry at the moment.
Composite vessels can take on any weird and wonderful form you can possibly imagine. A composite hull can be the ideal shape from of naval architecture perspective, as well as in the looks department.
If you’re after a fair hull then you really can’t beat the results of a properly reinforced GRP layup. However for a lesser cost on smaller, homemade boats it’s also possible to use wood as the complimentary material instead of glass or carbon. A traditional ‘strip planking’ wooden design laid across frames can be coated with epoxy on the outside to achieve a smooth and fair result.
GRP Strength and Resilience
Given that GRP layup schedules and reinforcements differ so much among different models it’s not easy to say just how strong this material can be, but try taking a hammer to a scrap section of fibre glass panelling at a boatyard and you might be surprised when it simply bounces off!
Whilst a thicker laminate reinforced with woven roving (or biaxial) glass fibres will certainly stand a better chance of remaining largely intact in the case of an impact with the full weight of the boat behind it, there will always, at the very least be some surface damage.
As for overall ‘sturdiness’ and rigidity, much like aluminum boats this come down to how much additional reinforcement is present in the form of bulkheads, ribs, and stiffeners etc. The great thing about GRP reinforcements is they don’t add much additional weight as they are often simply styrofoam batons. The strength comes when they are over laminated with mat and resin.
Unsurprisingly nothing else can compete with the superior look of a GRP boat. In the hands of a skilled designer anything is possible on paper, and thanks to the limitless potential of GRP mouldings, anything is then possible in reality.
Of course when the sleek, smooth lines of a GRP hull is combined with the finesse of other quality materials such as a leather interior or an epoxy coated teak foredeck, then the projection of quality steps up to another level.
GRP boats are generally a much smoother, more forgiving ride, particularly at speed when such things become most noticeable. Again this is all down to the fact that GRP hulls are much fairer than their metal or wooden counterparts.
There is also an argument for GRP hulls, particularly on smaller boats, being heavier than like sized aluminum boats, and as such ‘slicing’ through the water with less bounce.
For me this is a bittersweet benefit, knowing how much additional weight can reduce performance in other ways.
GRP can certainly be patched up and repaired, but the process is a bit more messy and involved than a lot of repairs to aluminum hulls, where a hammer and pot of paint are all that are usually needed.
If you’re just dealing with scratches, then carefully filling, sanding and painting can usually do the trick. Holes and cracks however, require considerable laminating skill to repair (usually best left to the experts at your local boatyard).
The unfortunate reality is that in a collision that would result in an aluminum boat simply getting dented, a GRP boat would very likely suffer a fracture or puncture.
On the plus side, the paint or gel-coat finish of a GRP hull won’t suffer any ill effects from saltwater exposure (ie. no corrosion) as aluminum hull would eventually do. It is of course still necessary to paint the hull with antifoul below the waterline to avoid any unwanted marine life making a home for itself on the hull.
From an aesthetic point of view, the repeated onslaught of spray onto the non antifouled top sides of a hull will ultimately cause the grp to lose it’s brilliance. If you’ve ever seen an older boat moored up that looks a dull creamy colour, you can bet that at one time it was a nice crisp white.
To prevent this from happening to your boat, a regular application of wax (specially designed for boats, the stuff for cars doesn’t cut it) is the solution. Giving your hull a regular wax and polish will keep the microscopic imperfections in the hull filled and protected from effects of salt water spray.
If your boat has really suffered from a lack of care and attention, whether it’s improper sealing to penetrations through the hull, or damage to the gel coat has exposed the raw laminate underneath, then you might suffer issues of water ingress.
Water ingress into the laminate can result in some fairly extensive repairs being needed. You might find the layers within the GRP start to seperate or ‘delaminate’, or where foam or wooden core is present, this can begin to rot from the inside, causing structural weakness.
Whilst you can keep on top of basic maintenance on a boat you’ve owned from new, such that you’ll stop serious water ingress issues from arising in the first place, you’ll need to be a bit more careful when looking to buy a second hand boat, as you won’t know what the previous owner has or hasn’t done in the way of maintenance, at least not without a through inspection.
Besides the great looks, the great naval architecture, and the easy maintenance, the other great selling point is, in theory at least, that typically being ‘production’ boats, that economies of scale make them more affordable than aluminum boats, which are typically one offs.
Wooden boats are of course at the heart of the traditional boat building industry, and the expertise and knowledge involved in designing and building wooden boats goes back many hundreds if not thousands of years.
Despite continual advances in technology wooden boats remain as popular as ever, particularly when it comes to older vessels that have been kept in good condition.
In many ways wooden boats are crem dela crem of craftsmanship in the boat building industry, and the boutique companies who construct them do so with a level of care and attention unrivalled by those working in the sheds of composite and aluminum boat builders. Whilst GRP hulls are fair largely by design, wooden hulls are often fair as a result of exquisite craftsmanship.
As such the end result can be a real pleasure to drive, and the oft quoted difference noted by those who have first hand experience of driving both GRP and wooden boats is that wooden boats make for a much quieter ride. It seems that despite the advances in composites technology, wood has yet to be beaten for its sound dampening qualities.
Strength and Resilience
Most modern wooden boats aren’t strictly purely wooden in their construction; most are coated in epoxy, which both serves to provide a surface gloss, a tight seal against water ingress, and a degree of additional strength.
None the less wooden hulls are by far the weakest of the bunch of all the materials on offer, lacking the multi layered reinforcement of GRP, and the inherent strength of aluminum.
Collisions of any kind are likely to be pretty unforgiving to wooden hulls, so at the helm of a wooden boat you either need to be a careful mariner, or otherwise be prepared for some expensive repair bills.
Wooden boats are the same kind of cool and vintage sports cars, but perhaps trump sports cars by not being as tragic or cliched (at least in some cases).
It goes without saying that all of the visual appeal comes from the wooden construction being on display (albeit ideally sealed with clear epoxy). A painted vessel that doesn’t clearly show off the wooden construction isn’t worth the expense and possible heachaches (leaks, warping and shrinkage due to water ingress) that are inherent with many wooden boats. Why have the negatives if you’re not reaping the rewards of the positives?
For me there’s something unmistakingly classy about sipping champagne atop the deck of a meticulously maintained wooden boat that a composite vessel (equivalent to the garish pomposity of a modern supercar) simply can’t compete with.
Wooden boats have much of the same ‘give’ in them as GRP boats that aluminum boats just can’t seem to compete with. In fact many would testify that wooden boats offer an even ‘softer’ ride than GRP boats, so they might actually be the most comfortable of the bunch. And of course, let’s not forget; a wooden hull’s dampening properties are a major plus point too.
Depending on the exact method of construction and the nature of the repair needed, repairing a wooden boat can be a very costly process.
For minor scratches in kinks it may be possible to repair the damage using some careful sanding an epoxy filling, but this is if you’re lucky.
If a panel is damaged extensively in on place (with a hole in it for example) the best solution will to be to replace it altogether, which in most cases will require the specific (and these days scarcely found) expertise required in wooden boat building. If it’s a hot formed hull you’ll need the surfaces of someone who can steam plywood and form it in its loosened state. However even cold forming panels (without the need for steaming) is a skilled job.
For a truly traditional build, gaps between planks will need to be filled with hemp or oakum mixed with tar, but the chances are your boat will be built using more modern techniques, so gap filling can again be carried out using epoxy.
Whilst I advocate keeping as much of the wood ‘natural’ in finish (albeit painted with clear epoxy and varnish, it is of course prudent to paint the hull with antifoul paint below the waterline.
Varnish needs more care and regular inspection than paint as it is more vulnerable to breaking down as a result of exposure to air, sunlight and sea water. So you’ll need to keep a close eye on this. You don’t need to sand back to bare wood everytime, just sand back deteriorated areas to provide a ‘keyed’ surface. Obviously the amount of varnish required depends on the manufacturers instructions, but between 4 and 8 layers is pretty typical.
Besides keeping on top of the surface finish, the most important thing to remember about wooden hulls is the need to keep them clean and dry, especially where both air and water are present. Whilst technically the hull beneath the waterline cannot rot due to the lack of air, the same can’t be said for areas such as the bilge where air and water can potentially be present at the same time.
Hence keeping the bilge dry, as well as other interior areas is of vital importance to ensuring the longevity of a wooden boat.
Newly constructed wooden boats are seen as something of an anachronism, and are as such quite rare. Unsurprisingly then, the boutique shipyards that offer newly built wooden boats can to a large extent name their price with the vessels they sell.
The second hand market on the other hand is a pretty active with vintage wooden boats dating back to the early 70’s, of which some change hands for extremely reasonable prices. There’s a fair degree of risk involved with buying such a vessel of course, and you’ll want to thoroughly survey anything you’re thinking of buying to avoid falling foul of any hidden nightmares in waiting.