A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Greg Rudzinski
Date: 2017 Jun 20, 15:09 -0700
" Which part of the crystal would have to be oriented 22.5 abaft of abeam to be deemed overtaking? The bow, the beam, the stern or the lubber line? "
At night the watch officer has only the side lights, stern light, and masthead lights to observe therefore the angled blinders within the running lights will dictate whether to stand-on or give-way. If in doubt then assume to be the give-way vessel when overtaking as per Rule 13. There is also the point where general rules are swapped for the action that best avoids collision as described in Rule 17 action by stand-on vessel. Another rule to look at that may apply to this collision would be Rule 10 traffic seperation schemes.
If Jeremy is following this thread then perhaps he can weigh in since he is actively sailing these waters now.
From: Bill B
Date: 2017 Jun 20, 16:01 -0400On 6/19/2017 9:43 PM, Frank Reed wrote: > Yes. I suppose so. If the container ship was on course 070° (which the > AIS indicates at the suggested collision time of about 1629 UT) and > which corresponds nicely with that track south of Oshima Island, then if > the impact angle was about 45° from starboard aft (sorry, I'm not > "salty" enough to describe this right).... Perhaps from the Department of Redundancy Department for most, but it strikes me that the Traditional Navigation discussion group is comprised of many non-sailors. For example, discussions of Lewis and Clark/surveying. For those members who do not have a copy of "The International Regulations for Preventing Collisions at Sea" (COLREGS) handy a few definitions might shed some light on what is being discussed in regards to the orientation of the ships. A ship is considered to be "overtaking" if she is 22.5 degrees abaft of abeam, and is required to keep clear. The beam is the waist or widest part of the ship, generally about 1/2 way between the bow and stern. Abeam is 90 degrees to the keel (a line fore and aft dividing the left and right sides of the vessel). Mostly. Abaft is towards the rear/stern of the vessel. A crossing situation is exactly what the name implies; not overtaking and subject to roughly the same rules as a 4-way stop sign in the US. Given the above I have questions regarding 22.5 degrees abaft of abeam rule that some of our Navy, professional mariners or sea lawyers can address. Reducing the argument to the absurd consider overtaking in the case of an aircraft carrier and a 42' power vessel on a possible collision course. The smaller craft's lubber line is at a constant angle of 113 degrees to the carrier's lubber line. At one stage she could be pointed at the carriers bow, hence not 22.5 abaft of abeam. In the next phase she is pointed amidships so is overtaking. In the finally phase she is pointed just forward of the carriers stern, so overtaking. Common sense would suggest the change of relative bearing of a given point on the carrier would have the 42' craft pass safely behind given enough distance between them (or get beat up in the carriers prop wash). Now let's apply this to two large ships like the Fitzgerald and ACX Crystal. Which part of the crystal would have to be oriented 22.5 abaft of abeam to be deemed overtaking? The bow, the beam, the stern or the lubber line?