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-   -   Collision Avoidance, Cones of Uncertainty, and Appropriate CPA (https://www.cruisersforum.com/forums/f90/collision-avoidance-cones-of-uncertainty-and-appropriate-cpa-189919.html)

evm1024 30-10-2017 10:38

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by robbievardon (Post 2509429)
evm1024, bit biased to quote Restricted versus GREAT LAKES data? I would think it pretty obvious that the concentrated line of traffic in Ontario is quite simply the shortest route.
Lodesman, I thought you pretty fair minded but your post 784 goes against Fact as per post 773.

Agreed, shortest route divided into 2 lanes. A defacto traffic separation scheme.

Off the Washington coast where I sail there exists North and South bound lanes which are not law (like a VTS). There are well known.

Not sure what you mean by Restricted vs Great Lakes. But if I have made an error I am happy to correct it.

Dockhead 30-10-2017 10:50

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
793 posts of different people explaining to you why you can't. You were invited to draw it; you did not. Some people patiently attempted to lead you to resources and skills, which would help you visualize it.

Here's me done with this.

evm1024 30-10-2017 10:59

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Of course it can be done. With enough BFI (brute force and ignorance) you can do most anything. At least theoretically it can be done. But theory and reality are far apart.

I've shown after having set up the crossing 1 mile out if you have a 1% difference in your speed you could end up with the ship +- 600' along its path thus screwing up all your well laid plans. A 1 degree variance in your path give like results.

Lets put this in prospective. You are really good so you take your wife and stand her up 24' from you. After all part of the modifications was to only do this crossing if your wife needed medical help.

So your wife is 24' feet away and you place an apple on her head. Picking up your bow and arrow you take aim. Hit the apple dead center and your are SuperMan. 5" low and good by wife, 5" too high and you mis the apple but your child is hit instead.

That is a 1 degree aiming window.

Do you feel lucky? After all William Tell did something like this.

ramblinrod 30-10-2017 11:25

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by evm1024 (Post 2509498)
Of course it can be done. With enough BFI (brute force and ignorance) you can do most anything. At least theoretically it can be done. But theory and reality are far apart.

I've shown after having set up the crossing 1 mile out if you have a 1% difference in your speed you could end up with the ship +- 600' along its path thus screwing up all your well laid plans. A 1 degree variance in your path give like results.

Lets put this in prospective. You are really good so you take your wife and stand her up 24' from you. After all part of the modifications was to only do this crossing if your wife needed medical help.

So your wife is 24' feet away and you place an apple on her head. Picking up your bow and arrow you take aim. Hit the apple dead center and your are SuperMan. 5" low and good by wife, 5" too high and you mis the apple but your child is hit instead.

That is a 1 degree aiming window.

Do you feel lucky? After all William Tell did something like this.

Huge strawman.

Scenarios totally unrelated.

Every skipper, regardless of plan or proximity always makes corrections to hold course and plan.

Once the arrow is released, it is no under command and control, completely opposite the crossing scenario.

It isn't like someone would ever come up with a navigation solution, set course and speed and never look at it again. Have you ever crossed any boat in close quarters before? Did you set course and speed and close your eyes?

evm1024 30-10-2017 11:41

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by ramblinrod (Post 2509514)
Huge strawman.

Scenarios totally unrelated.

Every skipper, regardless of plan or proximity always makes corrections to hold course and plan.

Once the arrow is released, it is no under command and control, completely opposite the crossing scenario.

I isn't like someone would ever come up with a navigation solution, set course and speed and never look at it again. Have you ever crossed any boat in close quarters before? Did you set course and speed and close your eyes?

Speaking louder and faster will not help you.

You ignored the point completely - you are not stupid, you choose to ignore the point. In case you are a bit dense (gosh I hope not) it is not about the path of the arrow. It is about the the results of a 1% error. Dodge this. All of the corrections happen in the aim.

LOL - You ask if I've ever crossed any boat in close quarters before. (wow, you won't answer that question but ask me, golly gosh)

In fact you do not answer questions and as a result your credibility is darn close to zero.

Make you a deal - answer my questions and I will answer yours.

First Rod, have you ever passed behind or attempted to pass behind a ship going 20 kts with a 180' CPA?

Second Rod, You stated a preference for a 180' CPA in the crossing. Would changing the CPA to 200' improve the crossing or degrade the crossing. You will need to justify your answer for this question.

Heck, I'll answer your question up front in the hopes that you will too.

Yes, I have crossed a SHIP in close quarters before. More than once.

ramblinrod 30-10-2017 11:52

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Dockhead (Post 2509493)
793 posts of different people explaining to you why you can't. You were invited to draw it; you did not. Some people patiently attempted to lead you to resources and skills, which would help you visualize it.

Here's me done with this.

Sorry , but yo have no auhority to direct me what to do. I know it can be done . If you feel it can't, by all means knock yourself to prove it .

I proved beyond any shadow of a doubt that your solution was doomed and could not possibly be done, whereas mine could.

Exile 30-10-2017 12:08

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by ramblinrod (Post 2509428)
Of course it CAN be done.

Whether one considers it "safe" or not, is a completely separate matter.

* * *

My boat is not required to have AIS, radar, or even VHF. I am required to have a radar reflector if in an area where ships may be travelling. Why? Because the ships are required to have this equipment, training, and personnel to use it, and are expected to see me, and avoid running into me, even if I don't adhere to Colregs.

These few sentences from a recent post explains everything for me. Whether crossings are "safe or not" is, of course, the entire theme of these threads. The "expectation," i.e. assumption, that the obligation rests with professional mariners to avoid colliding with ROD's boat (apparently whether he's adhering to the Rules or not) is all too similar to his very personal approach here which ignores & obfuscates the desire of others to learn how the Rules are applied, and what best practices may be.

And all over a sense of personal aggrievement over the words of another poster. :nonono: Oh well, his loss.

Paul Elliott 30-10-2017 12:30

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
I have enjoyed this thread, and learned a few things from it. Some of these are about piloting. Other things are about people.

evm1024 30-10-2017 12:50

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by evm1024 (Post 2509530)
Speaking louder and faster will not help you.

You ignored the point completely - you are not stupid, you choose to ignore the point. In case you are a bit dense (gosh I hope not) it is not about the path of the arrow. It is about the the results of a 1% error. Dodge this. All of the corrections happen in the aim.

LOL - You ask if I've ever crossed any boat in close quarters before. (wow, you won't answer that question but ask me, golly gosh)

In fact you do not answer questions and as a result your credibility is darn close to zero.

Make you a deal - answer my questions and I will answer yours.

First Rod, have you ever passed behind or attempted to pass behind a ship going 20 kts with a 180' CPA?

Second Rod, You stated a preference for a 180' CPA in the crossing. Would changing the CPA to 200' improve the crossing or degrade the crossing. You will need to justify your answer for this question.

Heck, I'll answer your question up front in the hopes that you will too.

Yes, I have crossed a SHIP in close quarters before. More than once.

Rod, I thought we had a deal. You are not crapping out on me are you?

You asked me a question and I answered you. Now it is your turn to answer my question. But all I hear is crickets.

El Pinguino 30-10-2017 13:23

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Pay attention people.... Dockhead has left the building... I repeat... Dockhead has left the building...

#797 'Here's me done with this.'

Move along... nothing more to see here... move along....

Sigh..... how long is it until the spring thaw? I feel for you people in the frozen north.. its going to be a long winter for some.

conachair 30-10-2017 13:35

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Paul Elliott (Post 2509569)
I have enjoyed this thread, and learned a few things from it. Some of these are about piloting. Other things are about people.

:thumb:

Staying safe around other boats following the colregs aren't really much of a problem even in busy areas, wafis thinking they know better can be... :whistling:

Dockhead 30-10-2017 15:26

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by El Pinguino (Post 2509615)
Pay attention people.... Dockhead has left the building... I repeat... Dockhead has left the building...

#797 'Here's me done with this.'

Move along... nothing more to see here... move along....

Sigh..... how long is it until the spring thaw? I feel for you people in the frozen north.. its going to be a long winter for some.

Ha, ha. Thanks, Ping :thumb:

I only "left the building" for a while -- had to fly back the route I sailed a couple of months ago. Kind of shocking that you can fly in 4 hours what it takes a few weeks of hard sailing to do by sea :banghead:


But I am indeed done with the argument -- and I'm sure no tears will be shed. Listen, can't we just all be friends? The main problem we have here, is that everyone has been looking to get something different out of the conversation. Some people want to drill into the issues, visualize situations they haven't experienced, learn something, test their beliefs. And others, well:

Quote:

Originally Posted by ramblinrod (Post 2509336)
. . . His proposed distance behind the lead ship was exactly the knee-jerk reaction I expected, before I even posted the scenario.

It's why I posted it. . . .

In other words, he wasn't actually interested in the issues at all (why he never participated in any of the analyses, never drew anything, never responded to any of the technical challenges) -- he was actually trolling me for a "knee jerk reaction" -- and I don't mind admitting that I fell right into it. Grappling with the wrong pass with the ship ahead, and not paying attention to the separate problem of the ship behind.

So let's let Rod have, what he was after -- YOU DID IT! WELL DONE! BRAVO!

Are we done now? Can we all move on to something more adult?

Dockhead 30-10-2017 15:30

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by Paul Elliott (Post 2509569)
I have enjoyed this thread, and learned a few things from it. Some of these are about piloting. Other things are about people.

Ha, ha.

I learned a LOT. It was a very good exercise.

One of the many interesting things I learned was that it is not nearly so easy to visualize these things, as you might think.

We definitely need a simulator. I just arrived in Finland and I'm going to talk to some game development guys I know tomorrow. Should be child's play for them, I imagine.

Lodesman 30-10-2017 16:38

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by El Pinguino (Post 2509259)
Rollocks.....

The OP seems fixated with 1000 ft boxboats doing 20+ knots... I simply suggested that most ships are not that fast or that big..... not that there were no big fast ships....

Well a thread about how to cross ships going slower than yourself would be rather anticlimactic, don't you think? The point of the exercise was to do with the dangers of crossing ships that are going significantly faster than you - and that doesn't have to happen 30 times a day; once in a bloody lifetime, if done wrong will be the last in a bloody lifetime. And they don't have to be 1000' - your last ship could go 20 kts, the ferries in Stu J's neck-of-the-woods go 20+, and Rod's ridiculous scenario had the ship 600' long, not that that made a whit of difference.

Lodesman 30-10-2017 16:42

Re: Collision Avoidance, Cones of Uncertainty, and Appropriate CPA
 
Quote:

Originally Posted by robbievardon (Post 2509429)
Lodesman, I thought you pretty fair minded but your post 784 goes against Fact as per post 773.

Sorry mate, I can't figure out what the connection is between the two posts. I'm pretty good at puzzles, but you've got me stumped???


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