Freighters vs. Sailboats

[Seaworthy Lass]

If anyone would like to state how low they are happy having the closest point of contact, I will post diagrams tomorrow showing when evasive action needs to be taken by the yacht if they are the stand off boat.

It has gone midnight here and matchsticks are holding my eyelids up .

[markpierce]

These boats are (wisely) diverting to their port toward our stern as we are leaving the berth (especially note the wake in the foreground).

[Seaworthy Lass]

Originally Posted by Lodesman

I appreciate the assist Lass. Perhaps you could explain how you disagree with the parts that you do. As to my 2nd para, I concede that if the sailboat was on a perpendicular course (ie. as far away from the freighter's path as is possible), and pointed at the freighter when the freighter was over the horizon at 20 odd miles, then the sailboat would avoid collision and have a nice safe passing, but in a more typical situation where the freighter is 5 or 6 miles away, and the sailboat is closer to the freighter's course or reciprocal, then I stand by my remarks.

I'm intrigued by your last statement, and await further explanation. I feel that a deep discussion on the requirements of the stand on vessel (rule 17) is forthcoming.

Yes, I agree that the further off perpendicular your track is from that of the freighter, the less use it is pointing to the stern of the freighter, but just give me what you consider a safe distance for the CPA and I will illustrate tomorrow that it is still often a good option for a wide range of angles.

I won't debate the requirements of the stand off vessel LOL. That has been done at length here for months now. I personally think ColRegs need to be followed and they are clear. I do, however, feel people completely underestimate at what stage they need to take evasive action to maintain a safe CPA (and there may be debate in what is considered 'safe' - to avoid this, for my calculations just give me a CPA you consider safe and I will work on this figure).

Night all.

[Lodesman]

Originally Posted by Rakuflames

BUT IT'S ALL HYPOTHETICAL, assuming that a sailboat will be so busy watching dolphins that they don't see a FREIGHTER until the moment of collision.

Who said he didn't see the freighter until the moment of collision?
The sailboat could be fine on the freighter's bow before they've come into radar range. The sailboat could be fine on the freighter's bow, before it shows on AIS. If they are closing on a steady bearing, then the relative bearings stays steady in both vessels for the entire period that risk of collision exists or could potentially exist.

The point is, that if there is a large speed difference between the two vessels (as would typically be the case in a sailboat/freighter interaction) the sailboat is not going to be broad on the freighter's bow or out on his beam, where he can swing around enough to be apparent, and point at the freighter's stern. Too many here think that what works between a couple of crossing harbour tugs can be applied in the open oggin when a cruising sailboat meets a merchantman at full cruise. Of course you can do a 180 and get out of the way - I've never said you couldn't. I think we should be discussing when to do that 180. I don't believe it needs to be done when you spot a smokestack over the horizon on a steady bearing. I'm sure we'll be discussing that.

[Lodesman]

Originally Posted by Seaworthy Lass

for my calculations just give me a CPA you consider safe and I will work on this figure).

CPA is all relative isn't it? You could pass a Panamax in the canal at 100 yards going in the opposite direction and not bat an eye, but open ocean at night in 20-ft seas, and you're going to want a couple miles. If you just want a SWAG, then use 1000 yds.

[Rakuflames]

Originally Posted by Lodesman

Who said he didn't see the freighter until the moment of collision?
The sailboat could be fine on the freighter's bow before they've come into radar range. The sailboat could be fine on the freighter's bow, before it shows on AIS. If they are closing on a steady bearing, then the relative bearings stays steady in both vessels for the entire period that risk of collision exists or could potentially exist.

The point is, that if there is a large speed difference between the two vessels (as would typically be the case in a sailboat/freighter interaction) the sailboat is not going to be broad on the freighter's bow or out on his beam, where he can swing around enough to be apparent, and point at the freighter's stern. Too many here think that what works between a couple of crossing harbour tugs can be applied in the open oggin when a cruising sailboat meets a merchantman at full cruise. Of course you can do a 180 and get out of the way - I've never said you couldn't. I think we should be discussing when to do that 180. I don't believe it needs to be done when you spot a smokestack over the horizon on a steady bearing. I'm sure we'll be discussing that.

I think you're engaging in what is, for you, a fascinating discussion. But practically speaking, I'm not concerned about a freighter I can't see yet because he's ove the horizon. I have lots of time to get out of his way. I'm not speculating; I see freighters here all the time. It's just not hard to avoid them. You see the freigher; you avoid a collision course; everyone goes home happy. I keep asking where all these collisions are occuring but get no answer, which I why I think it's all academic. Not that there's anything wrong with that, but ...

Cappy's point that beginners need to know to avoid freighters (my point too, at the beginning) is still valid. My point is that it doesn't have to be as complicated as is being presented here. That's shown by the last picture -- all the smaller boats just headed off to port to pass via the boat's stern. A freighter can't hit you where it's already been.

[sabray]

Recently I found my self under sail on the edge of a channel. A tug under tow was coming tword me . I clearly had right of way. I was not obstructing safe passage but he was determined to head for my side of the channel.
I was all for a game of chicken so I stood ground. Meanwhile he's wimping out blowing his horn real hard about 5 times. I blew my horn just like he did. Pretty sure he knows I'm pissed and not going to budge. Still he thinks he wants to play.
I go below and squirt unrefigerated mayo on home baked bread using store bought eggs stored without refrigeration and slathered in Vaseline. I turn on my ais b that i accidentally programmed to show me as a aircraft carrier headed for Norfolk naval base. That got his attention and some how he was able to find a good course that did not kill us both. Later as I came into harbor I dragged out my production anchor with 300 feet of true value double braid clothes line . Snubbed it up using bungee cords tied together.
Unfortunately the harbormaster didn't like the mold growing on my boat or the potted plants. Bastard hauled my boat boat cleaned it and replaced everything that didn't work and kicked me out of town. I think he stole a bottle of miracle whip I keep in case my mayo goes bad. Because I have felt a need to inform you of all this activity I have not waxed my mast today. Dammit.
I did do some scraping on my bottom today. The marina wants us not to work on our bottoms. Or anything outside the cockpit I think. I will probably be expelled for working without approval or a permit or a harness or helmet.... Etc

[Rakuflames]

Boy, you've just p-o-ed everybody! Very efficient, though.

[sabray]

Sometimes I'm just doing the best I can with what I have. This day it worked out real well.

[Therapy]

Originally Posted by sabray

Sometimes I'm just doing the best I can with what I have.

That is all anybody does. Every day. Some just can't afford mayo. Or a clean knife.

[cappy208]

Ok. I am taking this to task, because even a society approved instructor, (an experienced seaman) needs to see how the 'other half lives'.

Here are two photos I took of a simple (potential) meeting between a 20knot vessel and a 6 knot vessel.

The key points are, the scale is 12 miles, the range rings are 2 miles. (all amazingly like a radar screen!) As a point of reference, a vessel moving 20 knots moves 2 miles in 6 minutes. (and a vessel moving 6 knots moves .6 miles in 6 minutes)

In these presentations a vessel is in the center. (the 20 knot vessel)

The target is 6 miles off the stbd bow (30 degrees) the first position is plotted at 6 miles off, at 30 degrees.

6 minutes later the same target is plotted at 1.9 miles, 30 degrees.

The resulting relative motion (RM) line shows a collision is imminent.

The interesting thing is: the 20 knot vessels course is 000 degrees T. So the 6 knot vessels course is derived at (apprpxomately) 285degrees T.

The corresponding attitudes are: 20 knot vessel has a target 30 degrees off their stbd bow (most definitely NOT fine on the bow) And the 6 knot vessel has a target at about the port beam. NOTE, neither are 'fine on the bow' of ANYONE.


This is exactly how these situations occur. What appears to be a 'wide open' meeting is actually a Colregs accident waiting to happen.



Now, back to the example.

E to R is "Our Course, speed" The 20 knot vessel. E to M is Them, (their course and speed) The 6 knot vessel.

R to M is (amazingly enough) the Relative Motion line of this particular meeting. NOTE: in this case it is a collision.


Want to see how it looks from the 6 knot vessel?

[sabray]

I think you and mark need to quit drawing on your chart plotters. Looks like the Egyptian sign for female.who changed her mind and took a cab to a seedier side of town.. I find 5 blows clears my way.

[cappy208]

Originally Posted by sabray

I think you and mark need to quit drawing on your chart plotters. Looks like the Egyptian sign for female.who changed her mind and took a cab to a seedier side of town.. I find 5 blows clears my way.

Huh? I thought you hit the bunk????

[sabray]

Originally Posted by cappy208

Huh? I thought you hit the bunk????

I ran into, did not hit bast. Not bunk

Bast, Egyptian goddess of sensual pleasure, protector of the household, bringer of health, and the guardian saint of firefighters mistress of multi-tasking!

[Paul Elliott]

Cappy208, I figure that the 6-kt vessel can be no more than 24.4 degrees off the bow of the 20-kt vessel (for them to collide). The math is arcsin(6/20), which gives the widest possible angle. The largest angle for a 4-kt boat and a 20-kt ship will be 11.5 degrees, I think the point here is that "fine" or not, aiming for the ship's stern in these cases (assuming that you can even see it) will probably not give you the desired clearance. For that matter, turning 180 degrees may not help either -- you have to figure the angles. In most of our crossing situations, I end up telling the crew "we couldn't hit him if we tried", and I'm right.

I've seen a few close crossing situations on San Francisco bay, and these seem to be caused by the pleasurecraft seriously underestimating the speed of the oncoming ship. (Yes, this has been said here before.) In some of our races if you get the five-blasts from the ship's horn you're automatically disqualified (if you survive ).