Not celestial navigation...but

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Paul H

Paul H

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Nov 2, 2005
91
- - Ohio
since we're brushing up on our navigation during the winter months...here's a question: Your course is 290 @ 6.5 kts your radar tells you that there is a contact bearing 090 @ 3.5 nm. The contact is tracking 310 @ 14 kts. What will your closest point of approach be, and how long till you get there? NO CALCULATORS!!. Hope you have fun....
 
sailaway78

sailaway78

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May 11, 2005
3,431
Seidelman S37 Slidell, La.
My answer is

I'm retired, and this exercise just takes too much brain power. :)
 
J

John24107

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Feb 25, 2007
191
- - Sandusky, Ohio
If a train left Chicago....

If a train left Chicago at 3 pm and you left New York at 4 pm, how much was the cheesecake? Ooooooohh my brain hurts.
 
KorculaChris

KorculaChris

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Feb 6, 2006
249
Hunter 23 Bay Shore, LI, NY
Turn right 40 degrees

wait a half hour, turn left 40 degrees and see his lights pass astern.
 
P

Peter Milne

My Estimate

If I am interpreting the riddle correctly, we are now as close to the contact boat as we will ever get (3.5 nm), i.e. when it is 90 degrees off our beam.
 
C

caguy

If he is 90* to you with those headings

your paths should not cross. So now would be the closest encounter. I would go out and check his movements against my stanchions however. Frank
 
F

FrankR3878

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Nov 20, 2007
27
Flying Scot and self built wooden dingy 19 foot and V12 WV and MD
You are both diverging from each other

Your closest point is NOW. Your paths will continue to diverge and you will get further apart.
 
Dan

Dan

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Jul 26, 2006
190
Hunter 420 Stamford
Semi - off topic . . .

Does anyone know of a workbook that simply offers a bunch of navigation problems to solve? My winter project is to improve my navigation skills so it's much more second-nature.
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
At the great risk of being wrong I shall present

answer. In 15 minutes you will be separated by 2.75 miles and he will bear 53 degrees from you. In 45 minutes he will cross you course about 4.7 miles ahead of you. Chances are without radar you would not be aware of him.
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Dan this site looks promising.

The more you dig into the strange art you more you realize how little you know. I love it . Enjoy!
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
I am not always right but I

am never in doubt. :eek:
 
Roger (Ninette Manitoba)

Roger (Ninette Manitoba)

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Jan 22, 2008
519
Sundance Sundance 20 Weekender Ninette, Manitoba, Canada
dan, navigation exercises

Although not a workbook, Saunders (1982) Small Craft Piloting and Coastal Navigation has all of the techniques set out in a logical fashion. As for the answer to the question, you are on diverging courses so now is the closest you will ever be, and even if you turned to starboard for your tracks to cross, you would do so behind him as he is moving faster.
 
Bad Obsession

Bad Obsession

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May 23, 2004
3,319
I'm in the market as were . Colonial Beach
Shoot a warning shot across the bow

of the oncoming ship and then run up the colors. If it is an oil tanker you are VERY rich!
 
Paul H

Paul H

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Nov 2, 2005
91
- - Ohio
Give Ross a Cigar...

Not at the risk of being wrong at all... WOW...it looks like the problems are going to have to get harder...Well done Ross!!! Just because a vessel bears off your beam...doesn't necessarily mean thal will be your CPA...that's specifically why I chose the vessel to bear 090...
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Paul, On reflection I believe that the contact

crossed your course prior to your present position. I got my protractor turned wrong. Check to be sure. Course 310 is divergent from course 290. I think my numbers may be right but the crossing happened 45 minutes ago.
 
Roger (Ninette Manitoba)

Roger (Ninette Manitoba)

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Jan 22, 2008
519
Sundance Sundance 20 Weekender Ninette, Manitoba, Canada
okay I see where us divergent types may have gone off track

We assumed that the bearing was a relative bearing. There is no way that there is a convergent course even if the contact 'bearing' of 090 refers to 90 on the chart which is actually a (360-290=70)+90=160 relative bearing to your heading. Somewhat misleading, but we'll let it go this time. Its still early in the winter after all! :) So assuming that is the case, and the radar contact is behind you (essentially) he is approaching from behind but still diverging. The way I understand it, he is still at your closest right now. Assuming I am wrong, could you please explain your findings so that we can learn from it. And thanks for taking my mind off of the ongoing snow storm for a few minutes.
 
Roger (Ninette Manitoba)

Roger (Ninette Manitoba)

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Jan 22, 2008
519
Sundance Sundance 20 Weekender Ninette, Manitoba, Canada
I found an old workbook

I took a coastal nav course some years ago and found an old workbook and exam. It also has the 'correct' answers, so when you folks are ready for another brain teaser, let me know and I'll start another thread. (Don't want to get too many going at the same time)
 
Paul H

Paul H

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Nov 2, 2005
91
- - Ohio
I will give the answer tomorrow...but

you don't have to have converging courses to have a closest point of approach...You're right Roger...assuming a relative bearing is incorrect...a little tricky yes...but hey, it's all in good fun. Ross...I don't know how you would have gotten the correct answer with wrong angles...mmmmm I'll have to look at that one...
 
Ross

Ross

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Jun 15, 2004
14,693
Islander/Wayfairer 30 sail number 25 Perryville,Md.
Paul I think the closest was prior to your radar

contact. I had them converging but if they had been on constant courses then the reciprical of my numbers would would work.
 
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