Posted by: towmasters | March 28, 2010

New Life For Old Spectra – Part I: Hanging Tires On A Tractor Tug

Most of us never cease to be amazed by the increasing strength and decreasing size of modern synthetic lines. What used to require a length of manila as big around as your thigh can now be achieved with a piece of Spectra the size of your little finger. The worn hands and aching backs of many sailors have found welcome relief in ditching wire rope and instead utilizing lightweight softlines where appropriate. While wire rope hawser (steel cable) is still used for long towing astern there has been some discussion about the use of soft towlines if the same catenary could be duplicated. On heavier crane booms with multiple block systems it’s harder to imagine how a soft line would lead and wear better than wire rope, but that’s about the only application I can think of where cable may not be replaced by synthetic line soon. Headlines, mooring lines, pennants, and single part lifting gear can usually be adapted and replaced with synthetic line for better performance and safety margins.

Recently a few of us we were sitting around on Starlight Marine’s z-drive tractor tug Z-5 (these pictures are of the Z-4) in Alameda, Cal. brainstorming on how to hang a set of three giant tires on the tugs bow for fendering. Chain and, to a lesser extent, wire have  traditionally been the materials of choice for hanging tires. Chain is inexpensive and strong enough to withstand the heavy abuse inflicted on a tug’s bow. We had just rotated out a length of used 2 1/8-inch diameter Samson Amsteel-Blue 12-strand headline. After about 1,000 hours, depending on its condition and what kind of abuse it’s been subjected to, the headline is taken out of service. Often we can utilize different lengths of it for other less-critical applications and, after trying out a few ideas, we came up with an interesting way to hang tires. First you have to endure the fun of hand-drilling a few holes through several inches of heavy rubber. Lots of dish soap and a strong back are needed, and the bigger the drill the better. We started out using a sharp, two-pronged “Pickle-Fork” with a long drill bit in the center to start the hole and guide the forks. It really worked better than the wide auger-type bitts I’ve used before, but it still sucked the life out of the poor sap clinging to the drill. After one of the forks broke off it actually worked  better because the rubber wasn’t pinching the steel tips on both sides.

With lots of wrestling and soap we finally made enough holes to try hanging the tires. We actually made a “bra” out of three tires, and bolted them together with a length of 3-inch diameter all-thread and some large plates of steel for washers. Then we stabbed the “bra” with a forklift and hung the whole contraption over the bow of the tug on four lengths of the old headline. By running it down through the holes in the tires and then tying double-overhand knots  in it we had obstructions the size of basketballs that couldn’t squeeze through the fist-sized holes. After burning a pair of holes through the bow bulwarks just below the rail we welded in little 3-inch chocks to lead the two middle lines through, allowing them to be tied off to the support posts under the staples. To pin the tires up and aft from the ends we made holes in some existing loop-fendering gussets, installed screw-pin shackles, and ran the Samson through them, finishing the ends in an overhand or figure-8 knot. Burning the bitter ends to prevent future unraveling is also a good idea. Short eye splices were also tried, but they tended to loosen up under strain, so for now the knots seem to be the best way to go.

After several ship jobs and some adjusting of the Samson the tires hung where we needed them to and the softline has been an awesome improvement over chain. There are several advantages to the tires  being hung on softlines: the new headline (shipline) runs smooth and free from snags over the old line and it doesn’t get chewed up on rusty chain, with shackles and wire sticking out. This extends the working life of this very expensive but vital component of all modern ship-assist work. In addition, the rusty chain doesn’t beat up the tugs hull and paint when you mash the tires or bounce them around while sliding up and down against the ship, and the dings in the ships hull and scratches to their paint (which we never caused!) are also eliminated.

The lengths of Samson are rated for about 400,000 lbs. of pull apiece, even in a somewhat worn condition, and with four lengths holding up the tires we’re good for around 1,600,000 pounds. The tugs bow would probably peel off before any of the lines ever parted. All that and it beats throwing worn line in the dumpster to be trucked off to an ever-expanding landfill. What to do with it after the tires I don’t yet know, but it will probably be a long time before that becomes a worry.

Captain Jordan May

Co-Director, Master of Towing Vessels Association

Editor’s Note: repairing, reusing and finding new uses for things has been going on in one form or another on all kinds of boats for as long as boats have been around. Most owners of the vessels we work on generally try not to knowingly waste money and resources if it can be avoided. Money wasted is money not being reinvested in the company or returning a profit to the owner, who may use it periodically to give us improved wages, benefits and working conditions. Assuming that you don’t work for undeserving troglodytes, it’s in the interest of all working mariners to use your bean regularly to try to improve safety and operational efficiencies whenever possible. It’s also a long-standing tradition amongst seafarers from all over the world. Please do your part to keep that fine tradition going and contribute to the overall body of nautical knowledge. The MTVA welcomes to this blog any and all ideas that serve that cause. Clear photos, drawings and diagrams are particularly useful and we encourage all of our readers to share their knowledge on any relevant subject. If you click on our recently-added ClustrMap you’ll clearly see that our readership is worldwide. Everyone knows that there are many ways to skin the proverbial cat, so with towing vessel (and other) mariners from all around the globe reading, constructively criticizing and modifying each others ideas this has the potential to be very useful, as well as interesting.

About these ads

Responses

  1. [...] more » [...]

  2. [...] This post was mentioned on Twitter by Miami Towing, San Francisco Towing, DC Towing, Atlanta Towing, Dallas Towing and others. Dallas Towing said: New Life For Old Spectra – Part I: Hanging Tires On A Tractor Tug …: While wire rope hawser (steel cable) is sti… http://bit.ly/aeOjtb [...]


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

Categories

Follow

Get every new post delivered to your Inbox.

Join 330 other followers

%d bloggers like this: