Aluminium

Aluminium – General

This is gaining popularity, driven in part by its widespread use for plate boats (over 3 mm thick) in the professional market. It offers light weight, excellent weather and corrosion resistance (but beware of electrolysis), and construction with a modest inventory of hand and power tools.

The development of the kit boat has facilitated the ease of construction by the home boat builder.

This page coves both Aluminium from Plate and Aluminium Kit Boats, as these differ only in the sourcing of the information and cutting of the plate parts. After that the technology is common, and covered on this page.

Sheet aluminium  boats (under 3 mm thick) is rarely suited to home boat building, as many of them make use of pressed, rather than welded panel stiffeners. Also, the welding of sheet is more demanding than the welding of plate.

In professional construction the hull sides and superstructure are usually painted, to allow the filling and fairing to achieve the finish expected in the leisure market. The bottoms of trailer boats, and hulls and superstructures of work boats are commonly left unpainted by professional builders. Similar choices will apply to the home boat builder.

This is suited to trailable and moored boats, with shell plating thickness around 3 – 6 mm. Single or multi chine is common, to facilitate the plating being wrapped around the hull framing without the need for stretch forming/rolling. However, round bilge yacht forms have been built successfully by home builders, with plating being stretched by a roller unit.

Normally the full internal structure (centre keel, stem, longitudinal and transverse bulkheads, engine bearers, chines if applicable, decks, transverse frames, stringers) is built before plating the hull; commonly inverted.

Plate outlines are taken from the hull structure, and the plates cut to shape (usually with trimming onto the vessel), pre-bent where required, and then pulled into place, trimmed, tacked and welded.

An alternative, usually used only for smaller chine vessels, is to cut the plates to their outlines, and then pull them together, progressively tacking and welding the longitudinal seams. Typically this would involve joining the two bottom panels along the keel/stem line, then adding the topside panels progressively joining to the bottom panels along the chines. The transom is then added, the hull pulled into shape, then internal framing of stringers, bulkheads and transverse frames, decks etc are added. Note that this technique requires access to plate development skills to template and cut the shell plates to achieve the desired vessel shape as the plates are joined together.

The welding of aluminium, although more demanding of skill, and requiring more specialised welding machines than for steel welding, need not be an issue. If the builder hasn’t (or doesn’t learn) the necessary skills, and arrange access to the equipment, it is quite practicable to bring in some0ne on a contract basis to to the necessary welding. Hiring in of a person with suitable skill is not a major demand on the project. Several sessions of welding may well be required.

 

 

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