SOLUSV outgrows the cradle for unmanned boats

The established method of using an intermediary ‘cradle’ to connect davits and unmanned surface vessels for safe launch and recovery is being challenged by a lighter weight, more cost-effective alternative – the SOLUSV.

With applications that range from minesweeping and research to environmental monitoring, inspection and surveying, the unmanned surface vessel has become a utility asset enjoying ever wider deployment across the offshore, service and naval vessel sectors.

The USV’s rise has been matched by the emergence of an intermediary ‘catcher’, ‘cage’ or ‘cradle’ that attaches the davit to the vessel itself. The cradle clamps over the USV’s central pillar to ensure that, with no one on board the boat, launch and recovery is nonetheless accomplished safely and at no risk to what is a very expensive item.

Mature and adaptable, cradles require no design modifications or additional equipment as far as the USV is concerned. Again, the strong grip placed on the USV means that handling can be supervised by a single operative with no intervention required by personnel near or on the USV, even in sea states up to 5-6. Cradle systems can also be adapted to handle Underwater Vehicles and to work with Active Heave Compensation included in the davit design.

If the ‘pros’ are well-established, there are also ‘cons’. Cradles eat up deck space and add weight – enough to become factors at the ship design stage; again, while providing an efficient solution for USVs weighing up to 4 tonnes, heavier loads can be challenging. The cradle also adds complexity to boat handling – a definite drawback for any equipment used in harsh conditions on the high seas. Avoiding shocks or other impacts during ‘docking’, for example, demands a sophisticated guidance system.

To compound its operational inflexibility, getting access to a USV that is ‘docked’ in the cradle to switch payloads or for maintenance is often difficult while removing the USV will only be  possible if the cage is ‘split’ or divided in two, which itself will demand special tools that take up deck space.

These challenges affect costs, operational efficiency and maintenance, leading a growing number of USV users to seek an alternative solution.

Urgent and frequent inquiries made to Vestdavit and H. Henriksen – two of the leading forces in advanced boat launch and recovery solutions – have driven the development of the SOLUSV hook system, a powerful challenger to the traditional cradles used in USV handling.

Used in combination with single and dual point davits, the SOLUSV includes an integrated/dual lifting hook/painter hook system for safe and easy USV launch and recovery. Patented by H. Henriksen, the solution is marketed through Vestdavit, with both companies offering through-life product support.

Approved by DNV-GL, SOLUSV uses standard H. Henriksen hooks but deploys a unique spring-loaded rope drum mounted on the USV, tuned for easy connection to the fall rope via a special soft link. The low weight and compact handling system is easy to operate and offers a plug and play solution that also demands minimal design work for the mother vessel.

Because a member of the crew needs to ‘catch’ the retrieval line, the SOLUSV is acknowledged as limited to a maximum operational window of sea state 3. However, for a wide variety of conditions,  this is a limitation counterbalanced day-in, day-out by the flexibility of added access for maintenance or payload switching.

In short, if there are pros and cons when it comes to the ‘cradle’ vs. the SOLUSV, it is also fair to say that – now, at least – the user has a choice!

For more information, contact: Atle Kalve, Development Director, +47 908 93939; atle.kalve@vestdavit.no