Sidelined sub to get new tiles

The navy is planning to replace thousands of acoustic tiles that cover the Halifax-based submarine HMCS Windsor.

The tiles help the diesel-electric sub stay stealthy underwater.

"The replacement tiles will be required in areas as small as one tile, but generally in areas comprising many tiles," say recently published tendering documents that note the work must be done in Eastern Canada.

"The total area of tiles to be applied is approximately 7,000 square feet, with each individual tile measuring one square foot."

That’s almost half the outside surface area of the submarine.

Before the new tiles are applied, the sub’s surface must be treated with "ultra-high water jetting" and "the use of sponge blast surface preparation," said the tender.

"During the bonding process, the tiles will be held in place using a vacuum-restraint system."

Installing the tiles, which are tuned to various sonar frequencies, likely won’t be cheap, said Eric Lerhe, a retired commodore living in Dartmouth.

"It’s inconceivable that it would be less than $1 million," he said.

A sub missing thousands of acoustic tiles would be easier for enemy warships and helicopters to spot, Mr. Lerhe said.

"It would be a significant degradation in the stealth of the submarine."

Windsor returned to Halifax in December 2005 looking slightly battered after losing at least 70 tiles in rough seas during a six-week exercise with the Canadian and U.S. navies off the eastern seaboard.

Big waves swept off the rubber tiles meant to keep the sub’s position secret by masking its acoustic signature and reflecting sonar signals from other vessels.

"The tiles perform two functions, all of it related to stealth," said Mr. Lerhe, now a doctoral fellow with the Centre for Foreign Policy Studies at Dalhousie University in Halifax.

"And given that a submarine’s greatest advantage is its stealth, these tiles are like a key to achieving that. You send submarines in to do intelligence gathering or for landing special forces.

""You’re sending them into dangerous places in wartime, and in some peacetime operations. They must be silent to avoid detection to achieve their job."

The tiles reduce the reflective nature of the sub’s hull to sonar, he said. If the sub is detected by enemy warships, the tiles also help defend the sub from torpedoes, which use sound to hone in on a target.

"So it gives the submarine a better chance of escaping if it ever is detected," Mr. Lerhe said.

Navy officials weren’t available for comment.

In the past, the navy has said Windsor is slated to emerge this year from an extended work period at HMC Dockyard that started in late 2006. The sub is then expected to go through six months of sea trials and weapons certification.

Mr. Lerhe said he suspects many of Windsor’s original acoustic tiles had to be removed so technicians could work on the sub’s hull.

"In every operation, you’re going to lose a couple of them — five, 10, 15, 20, whatever," Mr. Lerhe said.

"But when you take off 7,000, you have to ask yourself, is it because, in a docking (work period), you should be taking off some horrible, some large amount, so you can actually access the steel surface of the submarine to do maintenance on it?"

Windsor is one of four diesel-electric subs built in the late 1980s and early 1990s for the British navy. The British mothballed them in1994 when they decided to concentrate on a nuclear sub fleet.

Windsor first arrived in Halifax in October 2001. Like the other three used subs Canada acquired from Britain in a lease-to-own deal, it still hasn’t fired a Canadian torpedo.

That isn’t likely to happen until at least 2010.