Wings take to the water

Dr Dryden is a very keen windsurfer

A retractable boat mast with a variable sail has been developed by a UK researcher after he studied the wings of bats and birds.

Dr Richard Dryden, a part-time lecturer at the University of Plymouth, believes his patented design will work on a range of watercraft from sailboards and dinghies to larger vessels such as wind-assisted tankers.

The structure is jointed and segmented which allows the shape of the rig to be adjusted to match the conditions.

When the rig is not required it can be folded away into a compact bundle that is convenient for mooring and transporting and safer when riding out extreme weather.

Wind strength

"I am a very keen windsurfer and I wanted a rig that would adapt better to changing wind strengths," the anatomy and physiology teacher told BBC News Online. "After looking around at what was available, I decided to develop a rig that changes shape a bit like a bat or a bird's wing.

Just like a bird

"The joints I use are quite biological to look at and the actual arrangement of the mast is rather similar to a limb."

The mast is in three adjustable segments and is tensioned to hold it in the desired position. When sailing in light winds, the mast can be fully extended. In stronger winds, the joints of the mast become more flexed, with the upper segment sweeping back - just like a bird when it pulls its wings in.

This brings the centre of effort of the sail - the place where all the forces seem to be focussed - lower down and prevents the boat from being overpowered.

Project development

Because the mast changes shape, the sailcloth has to be able to adapt and move with it.

"It's quite unlike modern sailcloths which are designed not to stretch, not to give at all," Dr Dryden explained.

"I'm still searching for the perfect material but the one I am using currently is like a nylon cloth that has been coated on one side with a polyurethane - a highly elastic material."

Dr Dryden has been given £45,000 in funding from Nesta (National Endowment for Science, Technology and the Arts) to develop the project further.

"We need to do some market research to see how people react to the idea, and then we need to develop some pre-production prototypes and that should be underway within 12 months."