The developers of an escort-tug system in which the winch and staple rotate together have received a U.S. patent for their invention.
Brandon Durar of JonRie Marine Winches and Greg Castleman of Castleman Maritime were awarded a patent in June for their “Staple Torque Aligning Winch System for Escort Tugs.”
Durar’s and Castleman’s system, installed farther aft and allowing the pivot point to move, improves tugboat stability and allows for faster turning in emergency situations. The creators are aiming their product at the burgeoning LNG tanker industry as well as the new Panama Canal and other high-risk large-ship escort environments.
Model-basin testing has proved that the moving the pilot point increases the turning force and reduces turning time to correct a tanker’s course. At the same time, it prevented the edge of the tugboats’ decks from tipping into the water.
“What we were trying to do is reduce the heeling angle,” said Castleman, a naval architect and president of Florida-based Castleman Maritime. “Once deck-edge immersion comes into play, you have to stop pulling and you can’t pull any harder. It’s a comfort thing with the captains. You reduce the heeling and you can pull a little faster.”
Durar and Castleman had collaborated on various possibilities for a rotating fairlead or rotating winch as early as 2007. Eventually the tandem winch-staple concept was incorporated into JonRie’s auto position escort winch, or APEW (See story, PM 161, September 2012).
JonRie enlisted the services of British Columbia-based tugboat scale model expert Capt. Ron Burchett to conduct hundreds of tests on the evolving rotating winch designs to determine their efficacy and safety attributes in various conditions. Testing was conducted at a laboratory model basin at Stevens Institute of Technology in Hoboken, N.J. Additional tests occurred later at the Port Revel training facility in France.
Durar, founder of JonRie, said the industry has yet to fully appreciate the significance of the stability created by coordinated rotation.
“When the winch and staple rotate as a single unit, you change the pivot point and you create more force and you create less heel,” Durar said. “What we found out at Stevens is that when you are attached to the ship, the rope lifts the boat out of the water and prevents it from capsizing … The more you pull, the more you pull the vessel back out of the water, so it solves a very, very hard problem to get around.”
Burchett’s testing confirmed over time that the adjusted position creates a more favorable pivot point and has a positive impact on stability.
“Instead of having the tow point amidships-high, you have it bulwark-low and aft, so you minimize the angle,” Burchett said. “I could go faster — up to 12 knots — because I didn’t get that heeling moment and I didn’t get water on the deck and the added weight to the deck. I had that reserve buoyancy that I didn’t have before. I said, ‘This is it! We’ve done it!’ … We’ve turned the tipping lever into a righting lever.”
With more direct pull, the tests indicated that the rotating staple increases tanker turning force by as much as 35 percent compared with a fixed staple. The aligned forces would stretch out the allowable reaction time when a vessel is in extremis.
“The farther you move that back, you create more force and you can turn faster and it makes the whole revolution a lot faster,” Durar said. “You’re not side-loading the staple. You’re not side-loading anything.”
Among the obvious customers would be the LNG terminal operators who have a high motivation to reduce risk and to enable the escorted tankers to move in more challenging sea conditions with confidence, Burchett said.
“With ugly weather, that’s where you need that extra factor of safety,” Burchett said. “We can work in weather that we’ve never worked in before because you’re not going to roll the tug.”
Durar said the system would be helpful in close-quarters waterways such as the new Panama Canal locks, which won’t have mooring mules, and many other ship-escort environments. JonRie, based in Manahawkin, N.J., and Castleman are shopping the concept but haven’t yet found an operator willing to incorporate it into a new tug.
“For people who want to have the ultimate tugboat, this will increase the capacity of an escort tug significantly,” Castleman said. Now it’s a matter of “finding an owner that has the vision to say this is a great idea (and) rather than recycling old tug designs, let’s design a tug that takes full advantage (and) enlist the support of the guys advising the gas companies that this is what they need.”
“The model testing clearly proved the superiority of this thing.”