Yes, if the chief uses the term “sleeve oil” I tell him you mean “margin”, which we still use of course. Keeping sleeve oil aboard is not worth the trouble.
“Margin” meaning on the books vs “sleeve oil” which is off the books.
1 Like
with the ever increasing oversight, micro-managing, and required daily performance reports - ship operators (big brother) desire to obtain maximum fuel savings by sailing with min required GM and min required bunkers (based on the spec market of course). They will employ weather routing services that are really fuel savings services with many times the recommended route being to optimize the time that your ship is burning heavy fuel vs low sulfur. Added to this is an industry where the shippers try to (sometimes successfully) cheat on the declared weight of containers (creating discrepancies in GM calculations - an MOL ship comes to mind), some Captains have used the practice that I called “sleeve ballast”. It’s not metered and it provides you with a more comfortable margin of GM should you desire it, then there are those planners that stow a ship using max ballast to get the min required GM (many times to avoid overstowage and/or minimize crane moves), that’s when the fun begins, and of course the emails, protests, arguments, etc,
1 Like
my apologies, I got off the track of the topic (my XTD error was maybe too much), whether the Captain performs the ocean crossing weather routing or a routing service is used, the goal threefold in my opinion: 1) make the transit safely to crew, ship, & cargo 2) make the required ETA 3) optimize fuel conservation. Now the long standing saying “the shortest distance between to points is a straight line” or “a great circle on a sphere” is important only when it doesn’t factor in weather, ocean currents, and / or eddies. In the case of crossing the Atlantic, the Navy ocean current maps are a good resource for gulf stream and Labrador current info and to a lesser degree eddies. I found that eddies (cold and warm) were somewhat difficult to ascertain and changed frequently, so somewhat unreliable. There have been more than a couple of times that I would setup the route so that the ship would be against the gulf stream for a few hours but have the advantage of running with the current for many hours afterwards. Once the weather routing has been decided on (and this can change on a daily basis depending on the weather - thus your routing might change), it is necessary in my opinion (traffic and COLREGs notwithstanding) to maintain as little cross track error as possible. Steering BACK to the course line adds miles and over a 3000+ voyage, those minor deviations and corrections can begin to add up in additional miles. I always wanted the mates to “keep the bubble in the middle” referring to the GPS and now ECDIS with GPS input. It’s a valid point that keeping the ship in the safety contour of the ECDIS is good seamanship based on the trail runs made to identify any navigational hazards. It is also true that (other than in heavy weather), no quartermaster can steer as well as a properly adjusted, adaptive autopilot. Just watch how much rudder a quartermaster (or cadet) uses to maintain the same heading as on autopilot. In my experience, once the routing is decided on and with any other subsequent changes to it for whatever reason, the best speed will be made by traveling the shortest distance - using the autopilot and maintaining very little cross track error. And if for some reason the ship had a large course deviation causing a greater than 5-6 mi XTD, a new routing would be setup up for the next waypoint and not try to steer back to the “road” for the next waypoint.
My guess is that the problem of finding the optimum strategy for track-keeping is going to be very similar to optimum course-keeping. That is the amount of correction should be in portion to the error.
Assuming the minimum steering correction is 1 degree than a XTE of 0.1 mile or less is likely noise (temporary variations in wind speed or current) and no correction is needed. Efforts to maintain the correct COG should increase as XTE increases.
As to what the max allowable XTE should be, my guess is that traditional practice of staying within a mile or two is likely in the ballpark.
Hi Everyone,
The Center for Coastal and Ocean Mapping (CCOM) of the University of New Hampshire (UNH) has developed an online survey for professional mariners and other professionals working with ENCs available at https://unh.az1.qualtrics.com/jfe/form/SV_9tPKpnrcZusJ4RT (the use of mobile devices is not recommended).
The current Zones of Confidence (ZOC) symbology with stars has received much criticism for its effectiveness in maritime navigation. As a result, the International Hydrographic Organization (IHO) relevant working groups have decided that the star symbology will not be used in S-101 and alternative methods are being investigated.
The purpose of this survey is to obtain informed opinions about different ways of displaying depth uncertainty in electronic chart displays. The greater the participation, the more representative the results will be and the more likely is for the new methodologies to be embraced by the maritime community.
Thank you,