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Old 24-04-2009, 18:09   #61
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My maths and physics are rusty but if you mean is the force on the anchor the same as on the stem when the boat is being held by a person ie the horizontal force due to wind, the same as on the warp and therefore the anchor.
Drawing a triangle of the depth and the rode the third line is the horizontal force equal to the wind effect since the boat is not moving.
The force on the warp is the hypotenuse and is clearly greater than the horizontal (the lengths of the lines being the horizontal and vertical forces relative to each other.)
We have two lengths usually the depth and the length of scope and need to find the length of the third side the horizontal . We can calculate the angle of the scope to the bottom from the angle whose sine is depth/scope.
The resultant force on the warp is the horizontal force/cosine of that angle say a.
On my calculations the force on the rode is 106% of the horizontal force at 3 times depth 103.3% at 4 down to 101.04 at 7 times depth.
So there is a difference but it is not great.
The vertical component that is the force lifting the anchor or conversely pulling the boat down is about 35% at rode/depth of 3 down to 14.5% at 7.
That is simplified by assuming an all rope rode to avoid the complications of changing angles of a cantenary of chain and the weight of the chain. Of course when the chain is tight it has the same angle as a rope. The forces on both the anchor and stem of the boat are both vertical and horizontal so will be greater than the horizontal force of simply holding the boat at the dock by the bow.
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Old 24-04-2009, 19:59   #62
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It's far from uncommon for many of these cruisers to up in size and length of their anchor chains before heading back upwards again.
OK better put us on that list. Just increased from 40 meters of chain to 90 meters.
Rope rode in coral is a joke... As is not sleeping at night because you have to anchor outside the line of boats in 14 meters.

The factor (non mathamaticle) is that the weight of the chain means there must be one hell of a storm to pick all the chain off the ground. Thats all I want ... a zero angle to the anchor shank. Its got nothing to do with the strength of the chain.

As for dragging, the chain itself will creat a huge amount of drag.

We dont intend on anchoring any deeper than we have been, but we want to ride out a blow with just one anchor and a lot of scope.

I would think the max we would anchor in would be 20 meters (60 feet) as the windlass would have a heart attack after that.
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Old 25-04-2009, 15:24   #63
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I would think the max we would anchor in would be 20 meters (60 feet) as the windlass would have a heart attack after that.
When I used to cruise Kenai Fjords, National Park, Alaska, USA, 60 feet was an average anchorage. 120' was considered deep. I think I anchored in like 40' maybe twice in three years.

And I had no windlass, mechanical or otherwise. That was back when I used to be a real man. I tell you, by the end of sailing season I was strong. 35# SuperMax and 35' of chain.

Principally nylon rode, of course. I had a method of using the winches on the mast if I was injured, tired, or whatnot.

I can remember more than once the disappointment when the hook didn't set the first time, or second, or third . . . .

Finally broke down and installed a mechanical windlass. Then moved and sold the boat without ever having used it. Rats.

I have a mechanical windlass now on 'the next boat.' That windlass and I have a very good personal relationship, bless it. Also, I've discovered that sailing just about anywhere else involved shallower anchorages. What did I know?

Funny how you get imprinted by your initial sailing experiences.
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Old 25-04-2009, 15:43   #64
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Talk about imprinting.

To this day I still carry 300' of extra three-strand in the cockpit lazarette, 600' of brait under the V-Berth, 35' of chain for each, and 50' more chain in the bilge. And 600' of poly for shore tie.

Yes, I do plan on revisiting my old stomping grounds someday.
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Old 17-06-2011, 14:09   #65
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Re: 1/4"HT vs. 5/16" Proof Chain

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One consideration with 1/4" ht is the lack of suitable shackles. The only shackle that seems to fit (pin size) through the standard 1/4"ht link are the tiny 1/4" ones. Most are rated a "1/4 ton" wll....

Some will have an over sized link welded onto the end of the chain... this seems like a lot of extra work, especially if you go and get that one last link galvanized.

I have a 50' length of 1/4" ht that I have moved from the boat to the house. I do not find it to have much use on the boat since I can not attach it to anything in any meaningful way.

I would recommend sticking with a 5/16" proof chain. The weight is not too tough to handle, but the links will accept a reasonable sized shackle.
The problem of joining 1/4" chain to the anchor is a thorny one that comes up again and again. There are couplers made to do this that are for sale on eBay. The problem is that they are stainless steel so unless one has a stainless chain and a stainless anchor galvanic corrosion will occur. If one has a machine shop a suitable joiner can be made from EN16 round steel bar and an "Unbrako" Allen screw can be fitted. Another way is to use a Crosby Double Chain Joiner rated at a SWL of 2600 pounds with a 4:1 safety factor. Most anchors will drag before the Crosby joiner breaks assuming that the deck cleat or winch doesn't pull off first! Please take a look at this:-

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Old 17-06-2011, 19:19   #66
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Re: 1/4"HT vs. 5/16" Proof Chain

Just use a 8mm pin Green Pin, or knock-off, shackle. Will fit the chain and has a WLL of 500kg at 6:1 design margin.

7mm (1/4") G40 (HT) chain busts at 3000kg and 6 x 500kg = 3000kg. A nice matching pair all done and dusted for $5, probably less.

No need to go inventing any wheels.
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