SHARK SKIN SHIPS?

“A new envi­ron­men­tally friendly coat­ing based on sharks’ skin may soon help the U.S. Navy increase ship speeds while sav­ing fuel,” Wired News reports.

The coat­ing… will be applied on the hull of ships below the water­line, where all man­ner of algae, bar­na­cles and other wee beast­ies attach them­selves, slow­ing ships and reduc­ing their maneu­ver­abil­ity…
Of the $550 mil­lion to $600 mil­lion the Navy spends annu­ally on pow­er­ing its ships and sub­marines, at least $50 mil­lion stems directly from drag due to marine growth foul­ing the ves­sels’ hulls, said Stephen McElvany, an envi­ron­men­tal qual­ity pro­gram offi­cer in the Office of Naval Research’s phys­i­cal sci­ence divi­sion.
Existing antifoul­ing paints such as trib­utyltin, or TBT, kill algae and bar­na­cles when they latch on. TBT is being banned world­wide by… the U.N. body respon­si­ble for over­see­ing shipping-​​related issues…
To find a way to per­suade algae to move on rather than killing them, Anthony Brennan, a University of Florida pro­fes­sor of mate­ri­als sci­ence, and his col­leagues turned to nature. Sharks don’t have algae or bar­na­cle prob­lems despite being under­wa­ter all their lives. Shark skin is made up of tiny rec­tan­gu­lar scales topped with even smaller spines or bris­tles. This makes shark skin rough to the touch. This irreg­u­lar sur­face makes it dif­fi­cult for plant spores to get a good grip and grow into algae or other plants.
“It’s like try­ing to walk across a bed of nails when some nails are longer and unevenly dis­trib­uted,” Brennan said.
Using a com­bi­na­tion plastic-​​and-​​rubber coat­ing, Brennan repli­cated a ver­sion of shark skin that is made up of bil­lions of tiny raised, diamond-​​shaped pat­terns, vis­i­ble under a micro­scope. Each “sharklet” dia­mond mea­sures 15 microns, or 15 thou­sandths of a mil­lime­ter, and con­tains seven raised ribs that resem­ble dif­fer­ent lengths of raised hor­i­zon­tal bars.
In lab tests, the coat­ing — pro­vi­sion­ally named Gator Sharkote — reduced by 85 per­cent the set­tle­ment of spores from a very com­mon and detri­men­tal type of algae called Ulva, a green sea­weed often seen on the sides of ships.
“The only place the spores land right now is where we have a defect in the pat­tern,” Brennan said. 

The Navy has had a wicked case of shark envy, lately. A few months ago, the ser­vice started look­ing into how sailors could use sharks’ elec­tric sen­sors to spot under­wa­ter mines.
THERE’S MORE: Over on the Defense Tech forum, there’s an impas­sioned defense of TBT, the old-​​school ways to clean ships.
(photo credit: Callaghan Fritz-​​Cope/​Pelagic Shark Research Foundation)

March 10th, 2005 | Ships and Subs | Comments Off Both comments and pings are currently closed.