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Old 10-21-2012, 06:37 AM   #1
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Some Basic anchoring info

Tuning an Anchor Rode
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Old 10-21-2012, 06:02 PM   #2
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Well that clears everything up?? HA HA
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Old 10-22-2012, 12:47 AM   #3
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You might be amused, but this reflects a serious attempt to analyze and understand the statics and dynamics of anchoring. It is a fairly sophisticated piece of work reflective of what engineers do in the design of a system. I rather admire the rigor taken and the careful conclusions reached. Boaters on the forum argue endlessly about the pros and cons of anchors and anchoring, mostly with only one data point of experience each, without making any progress in really understanding what is happening down under the boat. Even if you don't comprehend the math, taking time to read the variables in play and the analytic conclusions reached will give you a better understanding what is most important to a good anchor/rode/bottom combination for your circumstances. Note that those who only want to argue about which anchor is best are ignoring the many other considerations to be taken into account.
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Old 10-22-2012, 04:01 PM   #4
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FF,
Very good information that should clear up many misconceptions here on the forum.

GL,
Somebody needed to say it and you said it well.
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Old 10-22-2012, 06:27 PM   #5
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How does the foregoing technical treatise handle anchoring in thin sand on limestone or when you pick up a t shirt wrapped around your anchor, or when the rode fouls the flukes due to reversing current, or .....

David
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Old 10-22-2012, 06:46 PM   #6
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I guess nothing can calculate exactly all the variables David, but Larry is right, it did give a good analysis of how the rode works, as a separate issue from the anchor performance itself. I was also interested to see it supported Eric's belief that a mixed rode, ie chain to the anchor, and rope (preferably nylon), to the boat was the best in the extreme. The evidence being that one tries to use longest & heaviest reasonable length of chain, and then the length of rope rode becomes fairly flexible, from almost nothing in the light, to "let her all out" in a blow. That's how I read it anyway. I guess what was implied was that it was also sensible to have the best performing anchor possible locating the end, though that particular debate was not covered. Good stuff.
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Old 10-23-2012, 01:06 AM   #7
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Away the morale suppression team, Away. Not to start a pissing contest but let me ask the question. How many on this forum actualy have read that prior to owning a boat or anchoring a boat? Most have learned from trial and error on what works for the individual. I spent 22 years in the US Navy and never came across anything as in-depth as that when it came to anchoring, to include Frigates to Aircraft carriers and I have never seen anything but chain rodes on ships. Yes it is a nice technical read, I will not try to inject humor in my future posts.
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Old 10-23-2012, 01:24 AM   #8
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Quote:
Originally Posted by knotheadcharters View Post
Not to start a pissing contest but let me ask the question. How many on this forum actualy have read that prior to owning a boat or anchoring a boat? Most have learned from trial and error on what works for the individual. .
Yep. Prior to acquiring our GB all I knew about anchoring was that you dropped an anchor down the bottom with a line from it to your boat and you stayed put. When we chartered a GB we didn't know much more than that. We anchored a few times and simply let the anchor down with a whole bunch of chain on top of it. We didn't go anywhere but fortunately there wasn't any wind any of those times either.

When we got the GB we learned initially from talking to people. Bought a Bruce anchor because every GB in the charter fleet had them as did a lot of other boats and several people recommended them. If everybody's got them they must be good, right? (Took us a few years to finally figure out it's not right.)

The best single source of anchoring information for us was Earl Hinz's book. Then we joined a yacht club and started talking to the most experienced members and learned a lot more. We're still learning from these people. In fact on our last club outing where we had a raft of boats I learned an anchoring technique for a raft I never would have thought of on my own. So you build up your knowledge.

Armchair theory can be good sometimes. You have to know the rules before you can break them intelligently. But you also need to learn when the armchair theory doesn't apply, or at least doesn't matter.
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Old 10-23-2012, 06:25 AM   #9
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How many on this forum actualy have read that prior to owning a boat or anchoring a boat?

As a NYC kid (15) I started reading boat stuff.

It was right next to the auto stuff , and one day I looked in a sail book and realized it was filled with words and concepts I had never seen before. So I got hooked.

At the NY boat show (with no money) I became a bag stuffer , took and read all the free literature the exhibitors passed out , and visited as many booths to see the hardware.
It was a long time ago so folks like Merriman and Wilcocks Critten were just begining to sell pre made hardware , where usually the boat builder had a foundry and made the winches, cleats etc.

Ogg's booklet was my intro to anchoring , and I still believe Danforth does a fine job .
My library in FL has a better collection of early author created sailing books than any library I have so far visited (Library of Congress excepted).
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Old 10-23-2012, 08:03 AM   #10
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So I got hooked.

FF, I like your choice of words!
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Old 10-23-2012, 12:40 PM   #11
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Interesting to play with the anchor size calculation and the Rode calculation. The hardest to realize understand is imputing/changing the tension which is dependant on the length of the boat and the wind speed. The tension input is what changes/calculates the anchor weight and scope. Took me a while to figure that out.

Our 60 ft boat, with a 65# anchor, 176 ft all chain, medium sea bed holding should hold up wind speed of 30 to 40 knots. If the winds kick up to 60 knots the sea bed holding would have to be good and the rode 225 ft all chain.

So what itís telling us is the weight of the anchor is important, but so is the anchor rode length, the sea bed holding. I have save this for future reference.
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Old 10-23-2012, 02:16 PM   #12
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knotheadcharters,

I love the humor in the forums, without which we would be a boring lot! I was just trying to contrast your humor with my more serious perspective, and as an scientist I wanted to point out the value of such analysis.

Cheers
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Old 10-23-2012, 07:26 PM   #13
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Thanks FF, good stuff, it adds to available information, even though I recently bought Earl Hinz book. A lot of what happens underwater we can`t see, it`s obscured by water and distance. Anything that helps understand what actually goes on, and makes us think and act to improve anchoring and systems, is welcome. BruceK
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Old 10-23-2012, 07:47 PM   #14
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That is a great resource. The Synthesis spread sheet is really valuable, and what I used to select my ground tackle. The author is the developer of the Spade anchor, as I recall.
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