*Pics: The damage … and the culprit? Geelong Star, before its renaming. And below, Basslink cable damage, including the gouge …
I was going to pose this question in comments to see if any of the fishing folk interested could answer. However, my own inquires have given the the answer.
I have now dismissed any electrical-type effect as the cause of the cable failure. Thanks to those putting cases for and against electrical failure.
I have no found no reason to change my mind that external mechanical trauma was the logical cause.
Exactly what type of object did impinge on the cable?
Could the same type of object – or multiples thereof – be responsible for both types of damage illustrated by the two photographs.
The lower component of the seine fishing nets towing system are the weights. I always thought these to be selected scrap iron … something cheap (no expensive environmentally unfriendly lead these days).
Scrap iron is not uniform and could resemble other types of objects that ‘could’, for some obscure reason, be dragged along the sea bed.
To my great surprise the fishing industry has long had a low cost solution to the problems above. It also solves problems of net-fluid-flow under tow.
Flat steel plates … resembling a door off its hinges. The are often referred to as Flying Doors.
These are drilled in one corner and shackled via short hawsers to the lower tow line and lower mouth; they effectively flutter under tow. This provides a constant drag pattern and, being symmetrical in design, each one has a predictable effect on the whole net stability profile. So adjustment for correct net performance can readily be gauged by removing or adding plates.
If the net is out of adjustment and dives into the seafloor these plates evidently can gouge deeply like a plough … and as someone in comments ( HERE ) pointed out such an event can cause considerable damage to the net.
Not only that, the corners being right angles, are extremely vicious and extremely damaging when coming into contact with another object.
Such action and corner profile would be more than capable of inflicting puncture damage matching that exhibited in the first photograph (above) of the damaged section of the Basslink cable.
Also if the cable was pulled up momentarily by one door (weight) catching the cable lifting it slightly then another adjacent door (weight) could swipe the cable on the flat.
This would account for the superficial damage on the upper part of the main conductor in the second photograph.
I believe this logical mechanical trail leads to the conclusion that a towing fishing vessel damaged Basslink.
If so which fishing vessel?
The spacing between the puncture and the surface damage on the cable could indicate the size of net involved. It does seem some symmetry in weight distribution is needed to keep net dynamics in balance. The spacing between nets is likely to be different on the huge net of Geelong Star against the much smaller nets of the local fishing vessels.
As it seems all seine net type trawlers use this type of flying door technology they are big enough to have to carry AIS (Auto Identification System) and satellite.
I believe past AIS records are available?
The Geelong Star is the only ship to be operating without AIS.
There can only be very few fishing vessels, if any, in the area, at the time of cable failure with the capability of damaging Basslink in this way.
Then by a process of elimination there is a real possibility of narrowing down and eliminating the other vessels.
I have not heard back yet from Basslink concerning the status of the brochure sent to me by Clive Stott ( Comment 27 HERE ). This brochure indicates it is voluntary for fishing boats to notify authorities in the event of accidentally striking the cable – and they have no liability.
The question of testing nets with open gates in Bass Strait where fishing trawling is evidently banned is still not fully researched.
This starts a whole series of other questions concerning the saga. Including Bryan Greens document being censored for poltical purposes? ( HERE: Hydro document censored for political purposes )
Also ultimately … In whose interest?
*Bio of Kelvin Jones: Technically trained and qualified in the UK by a major electrical engineering manufacturing company in Power Engineering with Switch and Protection specialisation, moving on to defence electronics, commissioning RADAR and development of underwater weapons. TV transmission, field work and commissioning work on industrial electronics and HVAC carrier protection. Research in cellular and fibre optics communications. Field work on scientific, bio, and medical instrumentation with extensive work on Medical Imaging particularly CT scanners and Nuclear imaging. Mature age universty studies in computer science and Technology with emphasis on the viability of renewable energy technology on legacy power grids.
EARLIER on Tasmanian Times …
• Pete Godfrey in Comments: Hi Kelvin, there is historical ships position data available but unfortunately we have to pay to get it. It seems that data stored on computers costs heaps to supply. If we want data on who owns a company, we can look up ASIC records and pay to see the information. Now we can look up data on ships on sites such as AIS Vessel Tracking but again we have to pay. John Hawkins said in your previous article that Basslink have left the off cuts of the cable on the ocean floor. I would have thought that with the price of scrap copper these days that they would have recovered it, even if it was to buy a few years’ grog supply for the shipmates.
• Pete Godfrey in Comments: This is a bit of a stab in the dark. I am wondering if the rush to get a second Basslink cable has more sinister reasons. The possibilities are endless but lets look at a couple. First Tasmania is almost totally reliant on Hydro Power. The Dams have a finite lifespan. Already Lake Rowallan Dam has needed extensive repairs to prevent failure. What if the Government know more than they are letting on. Wouldn’t that be novel …
• Kelvin Jones in Comments: … A friend of mine in UK has been reading Tas Times … he is an ex-academic and lived for a number of years in Australia. He has quite a sardonic turn of phrase … here is a sample of his comments about Tasmania: “I followed the latest comments on the BassLink saga in the Tasmanian Times. Quite a multi-faceted debate is it not? Enough of you ‘stirrers’ exist to suggest the Geelong Star is culpable. From this part of the world, the State Government’s avoidance behaviour and disingenuousness seems absurd. Tassie is a relatively small place. The truth will out eventually. Better to face it now. I note that the Tassie Times considers itself a “cheeky, irreverent” alternative to mainstream media. It certainly appears to be that. Reading it as an outsider the impression created is of an island populated by seething malcontents, venal local councillors, devious soothsayers, single-agenda activists, and anti-government anarchists for whom any form of “rule” is the stuff of nightmares. Makes for a fun read though …