Someone else could say; In this case the tug operator had the tug and barges under control while the pilot did temporarily not have the tanker under control. The pilot did recover while the tug operator lost the tug and barges control. The whole situation went out of control!
The AIS vector at Conning Position seems to be heading straight for the bank but the Bow vector goes to Port, so the stern to starboard.
Prior meeting BW Oak, Genesis was aiming just inside marker 75. As she got closer to the channel limit, the pressure started to build at the bow and a depression at her stern. To maintain that heading, she had to apply a starboard wheel. When the vessels bow met, just calling amidships would make her swing to port by herself. Then, you better have a look at the rate of turn indicator. If you let her go to Port beyond say 15°-20° a minute without a counter starboard wheel … that could ruin your day!
The rate of turn depends on the shape of the bow. A large bulky one will turn much faster than a fine one. If you observe the dent on the barge, I conclude that she was not turning to Port as expected so finally, the vessel landed to close to the bank…
This video image capture shows that the navigable barge space was not invaded by the LPG. How could that be otherwise since she was drawing almost 37 feet while the barge channel is only 12 feet deep? Her draught just prohibited such an invasion. We also see that there was another tug & barge inbound aiming safely for beacon 74. Finally, the propeller wash shows that the LPG made her starboard turn on an engine turning ahead while such swing could be achieved on an astern engine.
We could question why such large vessels are allowed to meet at such a speed while they are confined in such a narrow channel bend, as we are all aware that Interaction between vessels and/or channel outer limits is exponential to the square of speed and inversely proportional the available room…
I certainly can not claim any expertise in this maneuver, but what you are describing doesn’t seem to match how I’ve seen it done.
There is an explanation from the Houston Pilots, who are experts here
HOW WE MEET IN OUR CHANNEL
For vessels meeting on the Houston Ship Channel, generally the center channel approach is used.
This maneuver is regarded as the safest way to meet two,large or deep draft vessels in a narrow channel.To begin this maneuver vessels initially approach head to head. When they are approximately 1/2 mile apart the vessel’s rudders are put to starboard to move the vessels to their side of the channel. When the ship’s bows are approaching abeam, her helm is put to port to move the sterns away from each other.Right rudder is used to check the swing of the vessels
caused by bank suction and the vessel’s interaction.
From what I’ve seen the ship is in a port turn and is headed back for the center of the channel even before the ships are past each other so that the sterns swing clear. Both ships are making the same maneuver at the same time
This issue in this case is as you have pointed out is meeting in a bend. I don’t recall that being the normal practice.
The maneuver described in the booklet has proven effective on straight narrow fairways but the dog leg at 75 adds an extra level of complexity. I wonder if the particularly fine entry on the tanker might have had an effect contrary to the pilot’s expectations.
It’s probably a mistake to try and derive much from those screen shots. For one those blue ship triangles don’t accurately depict the hulls.
I don’t know how much more difficult the bend would make the meeting, I would guess that the Genesis River would have to make more of a turn to port. The GR needs to both make the turn to port and swing the stern clear of the other ship. Even more so because the other ship has to make a slight turn to stbd.
In at least six previous investigations the NTSB has concluded that attempting to meet or overtake deep draft vessels in channel bends to be highly dangerous.
The excessive speed of both deep draft vessels meeting in the bend will undoubtably be the causal factor that lead to the Genesis sheering. Despite the pilots obvious contribution to the collision , the towboat operator will also take 50% fault for the ill-fated decision to turn to port rather than run aground in the safety of the barge lane.
I think so for having done the same maneuver thousands of times onboard on all types of vessels even longer and wider. I used to compare the entrance of the bow to the stake of an ax at 45 °to a log. A well sharpen ax will wedge whereas a dull one will bounce. At slow speed, fine bows still provide dynamical stability while bulky ones none. A vessel with a fine bow runs lesser than a bulky one at stop. Etc.
Turning to port is much easier than veering to starboard. Bernoulli-Venturi bank effects and propeller walk is put into contribution while turning to starboard, you only have the rudder to help. Turning to port swings the stern away from the meet vessel while to starboard brings the stern toward. Reducing speed to just half ahead gives you engine reserve in case of a kick ahead needed…
Been quite a few years, but Houston was my regular run for some time and you have it correct. Houston Chicken looks worse than it is, all the hydraulics are in your favor.
Not big on speculation, so just a guess - if ships are light enough they will drive around each other at the turn with out playing chicken. looks like the BW Oak may have gotten Genesis River far over on the bank and it took a sheer off the bank. Hard to second guess the tow too much watching the ship turning hard into it.
My display will have a rough outline of a ship that will be correct as long as the other AIS got the length, beam, and antenna location correct.
Barges, not so much.
“There is a member here that is a Houston Pilot.”
Yeah, but that (retired) pilot is going to stay out of the discussion. I will say that most of the above speculation misses the mark by a wide margin.
“as we are all aware that Interaction between vessels and/or channel outer limits is exponential to the square of speed and inversely proportional the available room…”
The hydrodynamics of ships in narrow channels and shallow water is not well understood at all. Add interactions from multiple vessels and we are all definitely not aware of anything at all. The formulae used to predict these interactions are woefully inadequate.
Guess I could quibble a bit with what exactly “not well understood” means. But in practical terms in the Houston Ship Channel the hydraulics of bank cushion and suction, and hydraulics associated with meeting and overtaking are well know and understood in a practical sense by all the players in the game.
I was a pilot in Houston for 30 years. In terms of maneuvering actual ships I agree that the interactions of ships with the banks, bottom, and other ships are well understood by the pilots. My post referred to the ability of the science of hydrodynamics to understand these interactions mathematically and to recreate them in computer simulations. I should have made that more clear.
