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Old 10-08-2012, 11:06   #31
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Re: Really Bad Anchoring Examples......Pictures

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Originally Posted by decatur1945 View Post
I thought about starting a new thread on this but since this is an eclectic group and the responses interesting and amusing I'll go ahead here.

I'm always concerned about how to judge how far from another boat I should anchor. I always try and anchor far enough away to avoid swing problems but on several occasion when chartering in the BVI or somewhere I haven't had the luxury of lots and lots of room. So, recetenly I've been looking around on the interwebs about how to calculate swing of a boat on anchor. And, (and this isn't unusual for me) I am a little confused. Some articles indicate that the swing room is the length of the rode, doubled.

Let's say you are anchoring in 7 feet of water, and the height of your bow is 3 feet above water, so that's 10 feet total. So you pay out 70 feet of scope. So does that mean you will swing 70 feet, well plus the length of your boat? Seems to me, using the Pythagorian theorem, that the swing would be more like 20 feet. Here's my thinking, often faulty. The theorem is a2 + b2= c2 (2 supposed to mean squared). A is the depth of the water plus your boat's bow above the water, b is unknown, and c (the hypotnuse) is 70.

So we have 10squared= 100 + b squared = 70squared which is 490.

So we have 100 + b = 490. To make it simple, let's make b = 20 so b = 400. But we have to convert b to the square root of 400 which is 20.

That makes the boat 20 feet from the anchor. Right? If I'm right, the radius of the potential swing is 20 for a total of 40 feet swing room. Plus the length of the boat of course.

So to dissuade the typical ridicule when I start thinking, please just make jokes about the computations and not the author!!!!!!!

As an aside, charter boats rarely have any markings on the rode, and I have no idea how to estimate how much chain is paying out.
Only semitopical, but if you want to use exponential notation, there's a language called mathmatica. It also works as a plugin language with Wolfram Alpha's site for a math shortcut, in that you can enter the variables and numbers, you get the solution from the calculator engine.

Ex: a^2+b^2=c^2.

^ signifires an exponent or superscript, depending on whether you're doing algebra or calculus.
_ signifies a subscript


and so on. Wolfram also has an online integrator, as well. It may yield different results than hard calc, though due to rounding errors.

They also have an online navigation and geodesy algorithm.
Navigational mathematics - Wolfram|Alpha

I'm not trying to be a jerk, or a math nazi, here, either.....I'm just trying to share a couple cool tools and the language to use them.
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Old 10-08-2012, 11:35   #32
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Re: Really Bad Anchoring Examples......Pictures

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Well some times its just pure entertainment.
Here is a dingy anchor to shore that I witnessed last week.
Really, do you really think that flippin shoe will hold you’re dingy when the tide comes in?

Oh, it’s a magic shoe, well that is different.

It'll hold great. Can't you see it's a golf spike, holds a lot better than a Sperry!!
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Old 10-08-2012, 12:01   #33
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Re: Really Bad Anchoring Examples......Pictures

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they must be nuts expecting that to hold, i always use both shoes

Lol
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Old 10-08-2012, 12:23   #34
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That's what I love about the boating world, for every numpty there is always someone decent like yourself who is willing to put themselves out without expecting anything in return, good for you sir!

I can't believe that that couple never gave you anything, imagine returning to find someone had towed their car out of a ditch and not giving them something! Oh well, let's hope they at least learnt a lesson.
Is it bad of me to say the opposite? Mid it weren't for the nice folks in the anchorage then maybe these muppets would learn something. In brazil, they love to anchor largish boats of the beach with a mushroom anchor that wouldn't hold a dingy. In small anchorages they motor up drop the hook and I don't know how many meters of chain into a pile and then steam off in their dink...

Same in the med, same in ....


...sigh...

I have a personal anchor story where I am the muppet but looking for pics at the moment so stay tuned...
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Old 10-08-2012, 13:33   #35
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Re: Really Bad Anchoring Examples......Pictures

I can't believe there is not a captain Jay photo on here.
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Old 10-08-2012, 14:02   #36
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Re: Really Bad Anchoring Examples......Pictures

Anchoring can be tough in Croatia ... those islands are very steep to.

We decided to stay in Hvar Town one night, where it wasn't bad for depth, but man, was it crowded. Before we really got settled, some guys left and managed to drag four anchors in the process, including ours.

Took us a long time to get reset. and when we did a 50-foot Beneteau dropped in behind us. Next morning, he decides to leave and starts shortening his rode using the windlass. His hook is up abeam of us (so it's a good thing the wind didn't shift in the night) and next thng we know, he's almost on our transom. My friend actually had hold of his pulpit and was pushing him off.

But no harm done.


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Old 10-08-2012, 14:19   #37
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Re: Really Bad Anchoring Examples......Pictures

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Originally Posted by Connemara View Post
Anchoring can be tough in Croatia ... those islands are very steep to.

We decided to stay in Hvar Town one night, where it wasn't bad for depth, but man, was it crowded. Before we really got settled, some guys left and managed to drag four anchors in the process, including ours.

Took us a long time to get reset. and when we did a 50-foot Beneteau dropped in behind us. Next morning, he decides to leave and starts shortening his rode using the windlass. His hook is up abeam of us (so it's a good thing the wind didn't shift in the night) and next thng we know, he's almost on our transom. My friend actually had hold of his pulpit and was pushing him off.

But no harm done.


Connemara
I'll often intentionally place my anchor abeam of another boat. When the wind changes, we'll all swing around together. Anchorages around here can be stupidly busy. I prefer to drop even with their transom, of course, but it depends how deep and how crowded.
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Old 10-08-2012, 15:35   #38
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Re: Really Bad Anchoring Examples......Pictures

Had another anchor calamity the other day. Was taking a nice siesta in my saloon the other afternoon, a nice warm day with a reasonable breeze, not much more than 15kts, blowing through the bay when WHAM!!!!!

Dashed outside to find a 50 foot Sunseaker Predator T-boned across my bows!! Fortunately, my boat had a thick rubber edging running around the entire deck and bows so no damage but this huge great gin palace was jamed on me good. Wife looks over and says, almost like it's the kind of thing that happens every day, "oh, I'd better wake my husband" !!!! Well, im puffing away trying to push 20 tons of giant speedboat off my pride and joy so how I never swore at her i'll never know!

Husband came up on deck looking bleery eyed and started peering over the side in dissbelief. "dont just stand there, start the bloody engines!" says I getting the hump now! Well, the idiot decides to reverse off my bows, promptly scooping up my anchor chair with his anchor which wife had not fully retracted!

So, with our boats now well and truely hooked up, I had no choice but to jump in and free it myself. Eventualy got my chain over the end of his anchor and shouted to them to move clear. Climbed back on board and my final words were to warn him about the very shallow reef I was anchored next to (deliberately in my shallow draft so other boats would leave me alone in the first place!) to which he nodded and promptly turned the boat around and ran aground!

Million pound boat and not a braincell between them, ive seen it all now. Just to add that little Rubessa never budged or dragged with a huge great Sunseeker broadside to the wind on her bows, I love my 5-1 ratio and good old Bruce anchor!!

Shame I never got a pic as I was a bit busy!
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Old 10-08-2012, 15:40   #39
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Re: Really Bad Anchoring Examples......Pictures


What do you expect from a boat that looks like a pair of sunglasses crossed with a sex toy?
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Old 10-08-2012, 15:45   #40
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Re: Really Bad Anchoring Examples......Pictures

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Originally Posted by decatur1945 View Post
So we have 10squared= 100 + b squared = 70squared which is 490.

So we have 100 + b = 490. To make it simple, let's make b = 20 so b = 400. But we have to convert b to the square root of 400 which is 20.

That makes the boat 20 feet from the anchor. Right? If I'm right, the radius of the potential swing is 20 for a total of 40 feet swing room. Plus the length of the boat of course.
I believe 70*70 is 4900, not 490.

In your example, b = sqrt(4900 - 100) = sqrt(4800) = 69.3

You can safely estimate the swing radius to be the length of rode you have out plus the length of your boat.
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Old 10-08-2012, 15:49   #41
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Re: Really Bad Anchoring Examples......Pictures

Have a Good laugh I,store my dingy anchor in an old reef runner shoe,prevents dangerous anchor flying,You Got it I,forgot to take it out of the shoe,a couple of hours later after shell searching,only about a 100 ft swim out to fetch the Dink.It drags slow.
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Old 11-08-2012, 06:26   #42
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Re: Really Bad Anchoring Examples......Pictures

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I'm not trying to be a jerk, or a math nazi, here, either.....I'm just trying to share a couple cool tools and the language to use them.
Both of you could use another (new) thread.
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Old 15-08-2012, 04:45   #43
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Re: Really Bad Anchoring Examples ... Pictures

Heres a nice example of, ahem, 'friendly' anchoring....

Drop right next to one boat, then pull back untill you're 5 feet off the bow of the boat behind, job done!
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Old 15-08-2012, 05:12   #44
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Re: Really Bad Anchoring Examples ... Pictures

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Originally Posted by simonmd View Post
Heres a nice example of, ahem, 'friendly' anchoring....

Drop right next to one boat, then pull back untill you're 5 feet off the bow of the boat behind, job done!
In those situations, I bring up my VERY large set of bolt cutters to the bow. I'll hail the boat and tell him it looks fine; him being so close, and I'll watch his boat for him when he goes ashore.... all the time fondling the bolt cutters. If he doesn't "get it", I ask where he keeps his "spare" anchor in case something should happen to the main.
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Old 15-08-2012, 05:26   #45
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Re: Really Bad Anchoring Examples ... Pictures

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Originally Posted by simonmd View Post
Heres a nice example of, ahem, 'friendly' anchoring....

Drop right next to one boat, then pull back untill you're 5 feet off the bow of the boat behind, job done!
At least he's prepared to drag into the other boat. I notice the fenders are still hanging over the side.

From the color of the water, guessing the depth he must have all of 1-1 scope out.
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