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Old 11-10-2013, 13:00   #1
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Making your own anchor - who has done it?

I was thinking about the rocna change away from Bis-alloy and that go me to think about those who have rolled their own anchors.

I did a quick search and came up with a few steels that might be usefull for a one off anchor.

Titus steels Endura came to mind along with the various MIL spec armor steels. Harder than heck and tough to boot. You would think that armor steel would not be brittle at all.

One could cut out the shank in the shape of a Delta shank and then a few fluke pieces and weld them up (no me, I've no welding skills). Then have them galvanized.

Cost effective? Hardly. But then again might be interesting.

Any one do this and want to share the details?
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Old 11-10-2013, 13:31   #2
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Re: Making your own anchor - who has done it?

Quote:
Originally Posted by evm1024 View Post
I was thinking about the rocna change away from Bis-alloy and that go me to think about those who have rolled their own anchors.

I did a quick search and came up with a few steels that might be usefull for a one off anchor.

Titus steels Endura came to mind along with the various MIL spec armor steels. Harder than heck and tough to boot. You would think that armor steel would not be brittle at all.

One could cut out the shank in the shape of a Delta shank and then a few fluke pieces and weld them up (no me, I've no welding skills). Then have them galvanized.

Cost effective? Hardly. But then again might be interesting.

Any one do this and want to share the details?
I'm not a materials engineer, but I would think that MIL spec armor is designed for ballistic impact penetration resistance, and maybe even to be brittle and to shatter for energy dissipation, not for the sort of forces that act on an anchor. Also, who knows what kind of specialized welding is required.
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Old 11-10-2013, 13:46   #3
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Re: Making your own anchor - who has done it?

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I'm not a materials engineer, but I would think that MIL spec armor is designed for ballistic impact penetration resistance, and maybe even to be brittle and to shatter for energy dissipation, not for the sort of forces that act on an anchor. Also, who knows what kind of specialized welding is required.
Me neither. However there is glass brittle and anchor brittle if you catch my meaning.

People talk about how brittle G70 anchor chain is. But the material engineers I talk to speak of how tough it is. Thus any "shock" loads given it from snatch loads are just not an issue.

I cannot imagine a tough armor steel even "feeling" anchor snatch. of course I could be wrong.

Here is some of the steel that I was talking about. They talk about how "easy" it is to work with.

Endura Steel | Wear Resistant Steel, Abrasion Resistant Plate - Titus Steel Canada
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Old 11-10-2013, 13:59   #4
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Re: Making your own anchor - who has done it?

The weakest part of any anchor will not be the shank or the flukes, but rather the eye where the greatest concentration of force will be exerted on the smallest mass.

Mass = Strength.

The mass of the eye can be as big as the size of the opening of the shackle that connects the chain. If you can have sufficient mass to achieve the strength required of the eye, you can make the anchor out of whatever you want, for example bronze or aluminum like say a Fortress

At that point the limiting factor is the pin size of the shackle and what's the biggest pin you can fit in your chain. True anchor chain has a larger sized link on the end so that a larger shackle can be used to ensure the weakest link is the chain itself, not the anchor or its connection to the chain.

If you have a plasma cutter and a welding kit you certainly make your own anchor. Pete Smith, the designer of the Rocna Anchor, was a cruising sailor and boat builder who made anchors for himself first, before selling the world over. See for yourself.

Our Story » Rocna Anchors
http://www.stuff.co.nz/sport/boating...d-a-hard-place
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Old 11-10-2013, 14:32   #5
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Re: Making your own anchor - who has done it?

Paint can, rebar, cement - 20 minutes work and overnight to dry and Bob's your uncle.
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Old 11-10-2013, 14:36   #6
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Re: Making your own anchor - who has done it?

Mass = Strength is just too generic to be applicable here. At the extreme an aluminum fortress anchor weighing 10 pounds is a lot stronger than a 20 pound anchor made of frozen butter. Materials do matter - Sorry for making my point in such a silly way.

If we take a crosby G209 and G209a shackle as an example. They weigh about he same but the G209A is much stronger.

The attachment eye of the shank can be made quite strong by sizing it correctly and that is not an issue. Keep the plate thickenss the same as the shank but make large shoulders that just fit the selected shackle with chain attached.

The strength of the shank is important so as to limit the misalignment under load. The goal being to keep the flukes and shank planes 90 degrees to each other.

Of course you could reduce the steel strength and end up with something like this:
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Old 11-10-2013, 15:01   #7
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Re: Making your own anchor - who has done it?

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Mass = Strength is just too generic to be applicable here. At the extreme an aluminum fortress anchor weighing 10 pounds is a lot stronger than a 20 pound anchor made of frozen butter. Materials do matter - Sorry for making my point in such a silly way.

If we take a crosby G209 and G209a shackle as an example. They weigh about he same but the G209A is much stronger.

The attachment eye of the shank can be made quite strong by sizing it correctly and that is not an issue. Keep the plate thickenss the same as the shank but make large shoulders that just fit the selected shackle with chain attached.

The strength of the shank is important so as to limit the misalignment under load. The goal being to keep the flukes and shank planes 90 degrees to each other.

Of course you could reduce the steel strength and end up with something like this:
Of course materials matter. Mass = Strength is not the same thing as saying Strength = Weight, so to say that one shackle isn't as strong as another of a different material isn't saying much.

I never said anything about the strength of the shank, but showing a picture of a bent shank only reinforces my point- if you want a shank that won't bend sideways, buy a CQR that has an "I" shaped shank section. This puts the MASS where you need it to be to resist bending if that's what your goal is.

You can make an anchor out of whatever material you want as long as it is sized sufficiently for whatever your loads are. If you want it to be stronger for less weight use a stronger material that weighs less.
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Old 11-10-2013, 15:10   #8
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Re: Making your own anchor - who has done it?

I have built anchors from stainless steel. All worked well.
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Old 11-10-2013, 15:11   #9
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Re: Making your own anchor - who has done it?

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Of course materials matter. Mass = Strength is not the same thing as saying Strength = Weight, so to say that one shackle isn't as strong as another of a different material isn't saying much.

I never said anything about the strength of the shank, but showing a picture of a bent shank only reinforces my point- if you want a shank that won't bend, buy a CQR that as an "I" shaped shank. This puts the MASS where you need it to be to resist bending if that's what your goal is.

You can make an anchor out of whatever material you want as long as it is sized sufficiently for whatever your loads are.
Mass it the quantity of matter and at STP here on earth is the same as weight. Mass equals weight and does not equal strength.

Using an I beam shape as in the CQR or flat plate as in the Delta of the same mass gives different strengths.

Peter Smith desighed a great anchor and built it out of Bis Plate. Then the steel was changed and there were bent anchors.

This thread is not about Rocna, CQR, Delta or any other existing commercial anchors. I'm asking about home built anchors and very strong steels. I asked for anyone who had done this to tells us about it.
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Old 11-10-2013, 15:12   #10
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Re: Making your own anchor - who has done it?

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I have built anchors from stainless steel. All worked well.

Any details you want to share? What did you learn in making them?
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Old 11-10-2013, 15:24   #11
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Re: Making your own anchor - who has done it?

I think the type of steel used is an often over-worried thing. Steel is amazingly strong and tough. The thin shank on the anchor shown in the picture is the design flaw in my mind. As mentioned an I beam would be much better. Sure, it might not have bent if high grade steel was used, but it may have bent just the same... we dont really know. Anchors usually bend like that from being stuck on an underwater object ... not from being embedded in sand.... heck, I've seen many forged CQR I beam shanks bent. Sand is not going to bend plain steel if the design is good. You get what you pay for, most dont want to pay for hardened steel. It's not just the cost of the steel, it's the cost of special welding, heat treating etc.
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Old 11-10-2013, 15:58   #12
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Re: Making your own anchor - who has done it?

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Mass it the quantity of matter and at STP here on earth is the same as weight. Mass equals weight and does not equal strength.

Using an I beam shape as in the CQR or flat plate as in the Delta of the same mass gives different strengths.

Peter Smith desighed a great anchor and built it out of Bis Plate. Then the steel was changed and there were bent anchors.

This thread is not about Rocna, CQR, Delta or any other existing commercial anchors. I'm asking about home built anchors and very strong steels. I asked for anyone who had done this to tells us about it.
Please pardon my ignorance, as I was unaware of the correlation between the change in material and the increase of incidences of bent shanks. I am surprised to learn this is true as Rocna lifetime warranties their anchors against bending.

Of course their warranty applies when their user guide has been applied. Funny thing, the User Guide states specifically that the anchor is not designed for rock or coral. To figure. Huh.

Anybody got an anchor for rock and coral that is warrantied against bending? Good luck with your anchor project.
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Old 11-10-2013, 16:32   #13
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Re: Making your own anchor - who has done it?

A friend of our built a "rocna". It worked as advertised.

b.
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Old 11-10-2013, 17:38   #14
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Re: Making your own anchor - who has done it?

Introducing THE BOOMER!

The world's first Frozen Butter Anchor! The Boomer uses exclusive high-strength FBA technology with a proven mushroom design and unique cast-in-place chain attachment to provide superior holding. Environmentally friendly material minimizes damage to sensitive marine life like coral heads and goes well with boiled lobster. Guaranteed to never bend or break in below freezing water!


"I've seen the effects of a frozen butter strike on a jet aircraft canopy, it wasn't pretty. This stuff is incredibly strong. So when I heard about The Boomer, I couldn't have been more excited.

I like that the method of chain attachment eliminates a shackle which is a common point of failure on many ground tackle systems. Although I would sleep better at night if butter didn't float, my children sleep good knowing that butter is a renewable resource, and besides it tastes good too!"

- Delancy, avid yachtsman
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Old 11-10-2013, 17:48   #15
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Re: Making your own anchor - who has done it?

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A friend of our built a "rocna". It worked as advertised.

b.
Love to hear about it. Any chance of some photos and a writeup. Without names of course.
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