BOAT BUYING TIPS (2) – What is a plate aluminium boat?

Another common question asked by prospective boat buyers is: “What is a plate aluminium boat?”

While there are some manufacturers who enjoy the confusion surrounding the definition of a ‘plate boat’, Bar Crusher sits comfortably at the opposite end of the spectrum and we’re happy to provide as much detail on boat building techniques as you require.

DEFINITION: A ‘plate boat’ is a boat that’s built using a properly constructed sub-floor frame; heavy-gauge, high-tensile 5083 aluminium cut from flat plate; and has a welded-in aluminium floor…

KNOW WHAT YOU’RE BUYING

A true plate boat draws great strength from an engineered sub-floor frame that supports, braces and stiffens the hull. A real plate boat also has a fully-welded and sealed aluminium floor, which essentially turns the entire hull into one very rigid structure.

real plate boat construction with fully welded floor

When a boat is used in a metre or more of wind chop or swell, it will be subjected to tremendous forces that will stress the hull. True plate aluminium boat construction, with a hull that’s been properly designed and well braced and stiffened, ensures it won’t flex excessively.

Excessive flex causes fatigue cracking, which means a lesser-built boat will start to crack around the welds, split and, ultimately, fail. Well-built plate aluminium boats can withstand these forces, while lightly-built boats can fail.

BEWARE: If a ‘plate boat’ has a carpeted plywood (or similar) floor held in position with a few tabs and self-tapping screws, it’s a dead give-away the boat’s built using a ‘hybrid’ tinnie construction method. These pretenders will never have the strength and durability of a true plate boat…

Think about what happens when you bend an empty aluminium can to and fro. Yes, that’s right… it cracks, splits and tears! This is exactly what can happen to a lightly-built aluminium boat if stressed by running through waves on windy days.

pretend plate boat with carpeted plywood floor

If the boat you’re looking at has ribs or extrusions running down from the side deck to the floor along the inside of the boat, and/or a carpet-covered plywood floor, it’s obvious the boat has been built using the lightweight ‘tinnie’ construction method, or a combination ‘hybrid’ method, rather than true plate boat construction.

TIP: There are opportunists who try to pass-off lightly-built aluminium boats as plate boats. Smooth sides don’t turn a tinnie into a plate boat, so take a closer look!

Technically, aluminium plate is 6mm alloy plate and thicker. However, few trailer boats are built from 6mm aluminium these days as decent-quality 6mm material is expensive, it’s heavy, and doesn’t provide any significant advantage in terms of strength and durability over high-quality 4mm and 5mm plate aluminium.

(If you’re looking at a sharply-priced aluminium boat claiming to be made from 6mm plate alloy, you can confidently expect an inferior grade material has been used and there have been many corners cut in the boat’s production.)

ASK THE RIGHT QUESTIONS

A few questions to keep front of mind when you’re looking at a plate aluminium boat…

  • Do the plate aluminium boats you’re considering incorporate a properly constructed sub-floor frame?
  • Are they constructed from high-quality, heavy-gauge, high-tensile aluminium cut from flat plate?
  • Do these boats feature welded-in, fully-sealed aluminium floors?

If the answer to any of these three basic questions is ‘no’ (based on your research, rather than the opinions of people hungry to make a sale), then our advice is to keep looking…

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