Anchor Circles

[psneeld]

Man it must be hard to have an ego that big. I mean seriously....

You don't need to make some kind of "non-circle" to anchor. I know on the ship I'm on we don't and we let out way more chain then the average boater. Your circle is so small compared to the size of the earth that it really doesn't matter. Stop trying to make yourself seem smart.

I don't think your ship anchors in the same types of situations.....plus I am pretty sure you have live watches and empires running g in certain extreme weather.

The point is, at higher lattitudes the circle does developed quite the error for being perfectly round.

Some people may not think that's a big deal and that certainly is their right.

But personalities aside, it is an interesting thing for me to enjoy on the forum, I can ignore the personal twists and it just as interesting to me as a lot of the drivel threads started.

Once again, it wasn't Jeffery that started the thread...but I can see his reaction to some...then again I think he just may want to ignore some too.

 

[rwidman]

The question is, how much does the circle distort and is it relevant too actually anchoring a boat?


Is it one foot? Five feet? Ten feet? One hundred feet?

 

[Jeffrey S]

Once again, it wasn't Jeffery that started the thread...but I can see his reaction to some...then again I think he just may want to ignore some too.

I should ignore some...but the target shooting is just too easy.

For what it's worth, my own anchor alarm is very simple and doesn't handle most of the issues I've been bringing up. But it always seems to go back to that - like I can't discuss an issue with navigation, etc. without someone thinking it's all an angle to make money. Guys, I have all the money I need. I'm not looking for some grand scheme to make more on creating free tools to allow people to anchor more safely. I'm done with that part of my life - it's all about giving the money away from here on.

I do love the findings that I have an ego though. Heck, come on, it goes much further than that. There's a difference between having an ego and being confident. I'm way over on the confident side. Way past the line into confidence-land. Always have been. Surprisingly, that's often what makes a good entrepreneur. When a whipper-snapper asks me for business help, I'll most often turn them down if I don't think they're confident enough.

That said, I've alway tried to create products and services that provided real benefits in ways that are less expensive (if not free) while funding it by taking advantages of changing markets. ActiveCaptain was the realization that a major change was happening with guidebooks (all paper products, actually, even paper charts). By taking advantage of that change, boaters could get better information, marinas would strive to be better, and boating could be made safer. Yep, I made money through that path. Isn't that the American way?

 

[psneeld]

The question is, how much does the circle distort and is it relevant too actually anchoring a boat?


Is it one foot? Five feet? Ten feet? One hundred feet?

Depends on the lattitude.

Then it depends on the rode out.

In much of Puget Sound from what I can tell it is around 30%.

So draw a 100 foot circle and in one dimension, it is only going to be a 70 foot radius.

Now...the million dollar question that needs to be asked,....is the circle distorted in conjunction with the chart? Is it calculated in lat/long or arithmetically inside the device.

I have to think about this some more and draw things out whether the problem is self correcting or not if on plotters, and what apps are doing to you also.

I know in high lattitudes that most nav is off grid charts because the low angles associated with GPS signals, but also because of distortion of charts.....If I recall correctlyfrom my polar expedition days....hmmmm...now this has got me realky thinking.

 

[Baker]

Depends on the lattitude.



I know in high lattitudes that most nav is off grid charts because the low angles associated with GPS signals, but also because of distortion of charts.....If I recall correctlyfrom my polar expedition days....hmmmm...now this has got me realky thinking.

Yep, that is correct. Most airplanes are limited in how high in latitude they can go. The ones that are authorized to do polar navigation use a different grid system.

 

[Fletcher500]

There is a line between confidence, and arrogance...when anchoring.

 

[BruceK]

There is a line between confidence, and arrogance...when anchoring.

Posting too.

 

[drb1025]

Does the rise and fall of the tide have more of an impact on the swing "circle" than latitude? For example, I am anchored with 75 feet of chain out in an area with a 10 foot tide. The swing area will be bigger at low tide and smaller at high tide, resulting in a swing pattern that won't be round.

 

[ksanders]

There is a line between confidence, and arrogance...when anchoring.

Not really. Especially when it comes to anchoring.

There has been two threads lately discussing anchoring and the technical aspects of drag sensing.

You can over analyze anything. You can focus on one single aspect of anchoring (Gps inaccuracy) and get caught up in the details.

The reality is that setting your anchor and having the confidence to know you are safe depends on allot of different data sources. Position is one, but depth, proximity to other objects, etc... All combine to create a picture in your mind.

That takes time to learn by
All of us. Aragonce no, experience yes

 

[Jeffrey S]

Does the rise and fall of the tide have more of an impact on the swing "circle" than latitude? For example, I am anchored with 75 feet of chain out in an area with a 10 foot tide. The swing area will be bigger at low tide and smaller at high tide, resulting in a swing pattern that won't be round.

That's a great question! When you start thinking like that, you're starting to grab all the nuances with anchoring and totally understanding the factors involved with it. There will always be those who just ignore everything - good for them. But if you want to actually think, then that question is one you'd come up with.

Pythagoras will solve your question. Anchoring creates simple right triangles perfect for the Pythagorean theorem. The only thing you're missing is the depth of water anchored in at low tide. So let's assume that's 15 feet.

So if you're at low tide, you have a leg (15 feet off the bottom) and the hypotenuse (75 feet of chain out). Solving for the distance along the sea floor gives 73.48 feet - your low tide distance.

Switching to high tide would mean the water depth is 25 feet. Solving for the distance along the sea floor gives 71.71 feet.

So the difference is 1.77 feet which feels wrong since there is a 10 foot tide. But that's the magic of triangles. Tide doesn't have much of an effect on how much you'll pull in or out. I doubt you could detect a non-circular track at that size.

But...

Tide can have a big effect on scope. And scope provides confidence in the anchor set and the amount of force you can withstand before dragging..

At low tide in this situation (assuming you have a bow eye at the water line), your scope would be 75:15 or 5:1 which is a pretty good scope for the night.

Now switch to high tide and you're at 75:25 or 3:1 which is significantly less and might not hold if the wind comes up.

 

[dhays]

Does the rise and fall of the tide have more of an impact on the swing "circle" than latitude? For example, I am anchored with 75 feet of chain out in an area with a 10 foot tide. The swing area will be bigger at low tide and smaller at high tide, resulting in a swing pattern that won't be round.

Likely already answered but it won't make a big difference. If I recall, it is a simple matter of the Pythagorean theorem, a^2 + b^2 = c^2.

 

[dhays]

Yup, already answered I see.