THE term “plate boat” is widely used by the boating fraternity. While plate boats are relatively common these days, these heavier set aluminium vessels can often differ in construction and composition from one manufacturer to the next. I liken the category of vessels that fall under the plate boat banner to four wheel drives in the car market. Hard-core 4WD enthusiasts will gravitate to a vehicle that can handle tricky offroad situations in the punishing Australian outback. On the flipside, an inner city mum taking her kids to soccer practice is probably sitting in the driver’s seat of a car that may have some similarity to a true offroad machine, albeit with a lighter build and more creature comforts.
Owners of “soft roaders” will generally never expose their vehicle to anything more than sealed roads and shopping centres. As you can appreciate, a serious 4WD with mud tyres is a different beast to a soft roader with highway rubber and aesthetic adornments! The key point here is not all 4WDs are comparable. It’s very similar with plate boats. Some manufacturers produce solid hard-core plate vessels designed for extreme toughness, others build less serious boats suitable for average fishing conditions. The trick is to be able to understand the differences so you can make a purchase decision that’s best for your needs and budget.
A number of years ago, I commissioned construction of a “serious” plate aluminium boat. During the process I visited a number of manufacturers to learn more about construction methods and the many subtle nuances of the boat building process. I reached out to a number of aluminium boat manufacturers more recently to discuss plate boats in a little more detail and learn about the offerings in the market today.
Origins
The general view surrounding the origin of the term “plate boat” comes, not surprisingly, from the material used. Plate aluminium is formed when an aluminium ingot is heated and rolled to form a slab. This slab is then rolled and may be heat treated to obtain the desired level of strength or temper. Once the desired thickness and temper is achieved, the plate alloy is then cut into the required sizes to be welded together. The aluminium used in “pressed” boats – a construction process where the aluminium is formed into shape by machines – is created in a similar fashion to plate, however, it’s further rolled and wound onto a coil for delivery to the manufacturing facility. In order to roll the aluminium it’s generally a softer and thinner material than plate alloy.
In the marine industry, plate boats are manufactured from the thicker and higher tensile plate sheets whereas pressed boats are generally manufactured from the thinner and softer coiled sheets. Generally speaking, a serious plate boat will have a hull constructed of five or 6mm plate alloy with the sides of at least 3-4mm alloy. The average pressed alloy vessel would generally have 2-3mm sides and a 3-4mm hull. Most of the standard tinnies used by Aussie fishos are constructed via the pressed hull method, athough more and more boats are being marketed as being “plate alloy”.
Plate construction
Apart from materials, it’s the unique construction methods used when manufacturing plate boats that gives them their strength and sets them apart from pressed and lighter built boats. As mentioned above, the thickness, grade and temper of the aluminium used are key to the construction of a robust plate boat. The structural elements of the hull including the bottom sheets, side sheets and subfloor frame are generally manufactured from quality, high tensile aluminium plate of five or 6mm thickness. DNV (or similar) certified marine grade 5083 aluminium is widely recognised as the material of choice.
Plate boats are generally constructed with a subfloor frame featuring longitudinal and lateral supports that are welded to the bottom sheets to create a rigid subfloor matrix which helps to stiffen and strengthen the hull. This welding of supports to the bottom sheets is a key differentiating factor that sets plate boats apart from their lighter grade pressed counterparts. The visual elements are also noticeable when you look closed at the construction of a plate boat. An aluminium floor welded to the deck further enhances the strength and rigidity of the overall structure. These decks are usually fully sealed and pressure tested.
Plate boats can either be self-draining or feature a well with a bilge pump. Supports or bracing to the topsides of the boat are generally welded to the topside sheets themselves – the thickness and grade of plate aluminium allows for structural bracing to be welded directly to the aluminium sheet used for the topsides, unlike a lighter pressed hull which may have the supports welded at the chines and gunwales only. Also, the welds on a plate boat are generally displayed in their original form and often left unground so you can see the strength inherent to the weld patterns and weld penetration.
Performance
Plate boats are heavier than their pressed counterparts. The increased weight allows them to carry more deadrise in the hull. This deadrise, or deeper vee at the transom, coupled with the rigidity in construction and increased weight, generally gives a plate boat more of a surefooted feel when driving through the chop and swell encountered in open bays and at sea. Combining this feature with wide chines or a flooding keel can give plate boats relatively soft-riding characteristics and stability at rest.
The heavy-duty construction of a plate aluminium boat is generally suited to larger vessels, often five metres in length or greater, used for fishing in open and offshore waters. Generally speaking, plate boats are geared towards boat buyers who have either owned a boat before and want to upgrade to a more specific blue water vessel with a certain level of customisation or to new boat owners wanting to pay a little bit more for robust nature and improved sea keeping abilities that plate construction offers. It is worth noting that the lighter construction and affordability of a non-plate or pressed aluminium boat is ideally suited to people on a modest budget or for boats that are used in relatively calm waters. Plate boats aren’t necessarily “better” than the pressed models. They’re just built differently and offer different features.
Variations
Not all plate boats are created equally. As mentioned in the opening paragraph of this piece, the term “plate boat” is used quite loosely by the boating community. The consensus from a number of boat manufacturers, both plate and non-plate, is that plate boats are invariably associated with the heavy-duty style of hull featuring fully welded subfloor utilising high tensile plate aluminium, manufactured and tailored for the discerning recreational fishing and boating market.
Any decent plate boat manufacturer or dealer will happily detail the construction process of the boats they build and sell, including details on the type and thickness of alloy used and the all important sub-floor frame design. Some may even show you through their factories so you can see how the boats are made or provide schematics or blueprints of designs and construction processes. If the manufacturer or dealer is a bit coy about confirming exact details on materials and design, then you should probably be dubious as to whether the boat is a “true” plate hull.
That said, as the boat building industry develops and aluminium fabrication technologies advance, there will no doubt be variations of aluminium boats that straddle the pressed and plate boat definitions. For example, I’ve heard the terms “pressable plate” and “recreational plate” bandied about in recent times. While some purists may roll their eyes, the reality of technological advancement and improvements in materials science will continue to blur the lines of plate boat construction. That said, the more “serious” end of the plate industry will doubtless continue its tried and tested construction methods as there’ll always be a market of hard-core fishos who love their “platies”.
Which boat – plate, pressed or maybe some kind of hybrid “pressed plate” – would suit you best? That depends on your budget, your car’s towing capacity and your personal tastes. As one insightful chap recently said to me, at the end of the day you should probably buy the boat that will catch you the most fish!
