WHAT IS A TRUE "PLATE" ALUMINIMUN BOAT?

There are essentially two types of aluminium boat-building techniques used in Australia.

 

1) Pressed sheet 'tinnie' construction (great for smaller boats that will be used in calmer waters such as rivers, lakes, estuaries and bays on calm days)

 

2) 'Plate' construction (great for bigger boats over 5m in length that will be used for bay, coastal and offshore boating)

1   LET'S LOOK AT THE TYPICAL TINNIE CONSTRUCTION

Around 60 years ago manufacturers started experimenting with very thin-gauge aluminium to build small roof-topper dinghies. These first 'tinnies' were often riveted together and were a great improvement over alternative construction materials of the day.

 

Today, manufacturers who use the tinnie construction method have also attempted to build larger boats. These boats, however, don't have the strength and durability of a plate boat.

 

The tinnie method involves using an aluminium alloy with a softer temper that allows the aluminium to be easily pressed into shape. (Often cut from coils of aluminium rather than from flat plate.)

 

This softer material is typically pressed in a brake press to give the sides of the hull that distinctive 'clinker' look, which adds strength. Some manufacturers now choose not to press the hull sides, to give the impression the boat is a plate boat. Flat sides don't turn a tinnie into a plate boat and, in fact, will significantly reduce the vessel's overall strength if the framing is inadequate.

 

The next step involves inserting the bottom, side and deck material into slotted extrusions around the gunwale, chine and keel. The whole structure is then stitch-welded together or welded along the extrusions. A number of ribs are then welded between the extrusions (down the sides and under the floor), in an attempt to give the structure some strength.

 

This design often relies upon plywood flooring to brace the hull. Typically, a piece of marine ply, covered with carpet, is fitted as a floor and held in position with a few tabs welded to the ribs or a few self-tapping screws. Often, plastic mouldings are then used to fit out the dashboard, side pockets and cabin areas.

 

This method is great for mass production of trailer boats.

 

The tinnie method is great for smaller boats which are to be used in calm conditions, but it simply can't provide the durability of the Bar Crusher style plate aluminium hull.