Hybrid Laser Welded Octagonal Hollow Sections for a Wind-Kite Telescopic Mast
One approach to reducing fuel consumption on large ships and container vessels uses a kite to harness wind energy, with a telescopic mast on deck serving as the launching and recovery tower. When the kite is deployed the mast extends fully; when not in use it retracts. For a project destined for Germany, the construction of this mast required a set of tailored hollow sections: one nested inside the other, each a different size, all in a custom octagonal geometry and all made from special marine carbon steel. The sections had to be stiff enough for safe operation under load but as light as possible to avoid overloading the vessel.
Stiffness, Low Weight, and Extremely Tight Tolerances
A telescopic mast places conflicting demands on its structure. It has to be stiff enough to handle the mechanical loads during kite deployment and recovery, but every extra kilogram adds to the topside weight of the vessel, so the design had to be as light as possible within the stiffness constraint. Because the sections nest inside one another and the mast has to slide smoothly in and out, the dimensional tolerances were extremely tight: any deviation in cross-section geometry would affect the mechanical function directly. The specification also called for a custom octagonal profile, which is not a standard catalogue shape, and required special marine carbon steel D36, a grade certified for shipbuilding.
Octagonal D36 Sections from 800×800 mm to 180×180 mm by Laser Hybrid Welding
A set of octagonal hollow sections in marine carbon steel D36 was produced, ranging from the largest segment at 800 x 800 mm down to the smallest at 180 x 180 mm outer dimension. Each section was joined using laser hybrid welding with 3D laser technology. Laser hybrid welding combines the deep penetration and low heat input of laser welding with the gap-bridging capability of arc welding, which produces sound welds with minimal distortion and good mechanical properties throughout the joint. Both qualities, weld integrity and dimensional stability, were essential for the sections to function correctly inside a precision telescopic mechanism.
Application Context
This case sits in Montanstahl’s shipbuilding and maritime segment, where custom laser welded hollow sections are specified for precision structural applications on vessels and offshore equipment. A wind-kite propulsion mast is a good example: it has to combine structural performance with tight dimensional tolerances across a range of section sizes, in a certified marine steel. Custom hollow sections like these are produced to the customer’s design and supplied worldwide to shipyards, marine equipment manufacturers, and vessel operators.