Dutch engineers have unveiled a radical idea for a tilting lock to allow tall sailing boats to pass under bridges without them having to lift.
Royal HaskoningDHV designer Carolus Poldervaart told NCE he was motivated to come up with the product by frustrations waiting for bridge spans to open.
The consultant is engaged in talks with the Dutch government over a proposal to use the design in three locations in the country.
Poldervaart told NCE: “The idea came a year ago. I do a lot of sailing on a river that has an opening bridge, which I also cross by car. So it was an obstacle in two ways.
“I first thought you could tilt the yachts, but the sailors don’t like that idea too much.”
Instead he settled on a plan to dig trenches below the river, allowing yachts to be dropped down below surface level to pass under bridges.
The floating lock contains two separate water-filled channels for yachts to use.
When the lock is level, the water surface in both channels is 4m lower than that in the river. The lock tilts to raise the level of one of the channels to meet the water level outside, and let yachts enter.
It then tilts the other way to lower the yacht by 8m, allowing it to sail beneath the closed bridge before being returned to water level.
“It works on the principle of a football floating in water,” said Poldervaart. “You just need a little energy to turn it around.
“It is the same principle with a pipe, and this is essentially an open pipe that floats and tilts a total of 32 degrees.”
Poldervaart said the lock would cost €60M (£48M) to build but that this could be easily justified by the benefits of keeping a bridge open 24 hours a day
Royal Haskoning claims the lock would pay itself back within 12 years if used at the site of the Haringvlietbrug opening bridge in the Netherlands, making a profit of €100M (£80M) over 25 years.
“It has been designed specifically for three locations in Holland,” said Poldervaart.
“You need a lot of space, and a bridge with more than one span so other ships can still pass through.
“You also need bridges with existing lifting spans as the economic justification is the ability to keep the highways open.”
Talks are underway with the relevant government department, and the designer said he would look further afield if necessary.
“We hope this will lead to other projects. We will consider looking abroad if it does not work out in Holland. There must be locations elsewhere in the world where this would work.”
The main practical challenge would be weather conditions, said Poldervaart.
“The idea is simple but the challenge is making sure it is easy to move the lock in high wind.”
The lock is designed to tilt 32 degrees in three minutes, with 30 seconds needed to set the tilting in motion.
In normal weather conditions this would use just 0.04 kWh, according to the designers.
In addition, the lock can use energy it produces when stopping, as well as from solar panels on its structure.
The lock would be made of steel and enable 15 to 30 yachts per hour to pass a bridge without it opening.