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

Another common question we’re 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 is happy to provide as much detail as you require.

Most people perceive a plate boat to be a heavily-built aluminium boat and therefore more durable. There will always be opportunists who try to pass-off lightly-built aluminium boats as plate boats.

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

In this light, the best definition of a ‘plate boat’ is a boat that’s built using a properly constructed sub-floor frame with a welded-in aluminium floor; heavy-gauge, high-tensile 5083 aluminium alloy and cut from flat plate.

If it has ribs or extrusions running down from the side deck to the floor along the inside of the boat, it’s obvious the boat is built using the lightweight ‘tinnie’ construction method, rather than a true ‘plate’ style build.

If a boat is to be used in a metre or more of wind chop on bays or in swell offshore, it will be subjected to tremendous forces that will stress the hull. To withstand these stresses, the hull needs to be properly designed and well braced and stiffened so it won’t flex excessively.

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

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.

Do the plate aluminium boats you’re considering purchasing incorporate a properly constructed sub-floor frame? Are they constructed from heavy-gauge, high-tensile aluminium cut from flat plate? Do these boats feature welded-in, fully-sealed aluminium floors (as opposed to carpeted plywood or treadplate held in place with a few self-tapping screws)?

If not, our advice is to keep looking…

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