Making your own anchor - who has done it?

[Matt sachs]

Originally Posted by evm1024

Manson's are Bis Plate at 800 MPa (116,000 psi) so using 50000 psi (344 MPa) steel is worse that the bent Rocna with 420 MPa steel. Rocna started with Bis plate then downgraded to 420 then bent a few before going with 620 MPa steel and called it good enough.

Of course if you used 1/2" plate for a small anchor it could be fine but if you made an 80 pound copy the shank would likely bend like a pretzel at some point.

Fair winds to you (no I really mean that when on anchor Fair winds).

Regards

Well now, thats bad news.....

[evm1024]

Originally Posted by Matt sachs

Well now, thats bad news.....

Not as bad as you might think. Looks like you have a thicker and larger shank that a production anchor of the same size. Bigger is often stronger and the reverse.

Manson, Rocna and the like do (did) use stronger steels so as to allow for thinner and lighter shanks. Weaker steel means that you need thicker / bigger to get the same strength.

The reason I was talking about armor plate or endura was to allow an anchor to be made that would be rigid. And hold its angles better.

One thought (patent pending) I have is to use "thin plate" (1/4") for the roll bar. This would present less surface area and perhaps "slice" through the substrate without balling. A deep diving anchor that comes up much cleaner and with less resistance. And yet still self right. remember folks I invented it, contact me for licensing agreements.


High strength steels allow you to do this.

[Pauls]

Hi Guys,

Regarding grades of steel to use for making anchors, it is basic engineering that weaker or stronger steels will both work, you will simply need more of the weaker steel than you will of the stronger to achieve the same strength.

More weight is good in an anchor. Very few sailors will argue that. The weaker grades of steel (A36 is the standard, very common) are significantly cheaper than the higher strength alloys. Use more of the A36, make the parts a bit thicker and you will have a heavier, more effective anchor for less money.

Making your own anchor is very cost effective if you can weld. If you can't, it's a great project to learn on. I built a 160 lb Rocna clone out of scrap steel that cost me almost nothing, the only significant price was the galvanizing.

[JonJo]

Originally Posted by Pauls

Hi Guys,

Regarding grades of steel to use for making anchors, it is basic engineering that weaker or stronger steels will both work, you will simply need more of the weaker steel than you will of the stronger to achieve the same strength.

More weight is good in an anchor. Very few sailors will argue that. The weaker grades of steel (A36 is the standard, very common) are significantly cheaper than the higher strength alloys. Use more of the A36, make the parts a bit thicker and you will have a heavier, more effective anchor for less money.

Making your own anchor is very cost effective if you can weld. If you can't, it's a great project to learn on. I built a 160 lb Rocna clone out of scrap steel that cost me almost nothing, the only significant price was the galvanizing.

Weaker steels need to be thicker to impart the necessary strength, thicker steels impose resistance to diving, and non diving anchor does not develop holding power - which is why nearly all anchor makers now use higher tensile steels in the shank.

Most anchors today self right, drop them on the seabed, pull the chain the the toe of the fluke engages with the seabed and the fluke then digs in. Use thicker steel and you alter this balance (because the shank is heavier.

Most anchor makers will tell you weight is not the panacea, look at Fortress. Its surface area that is important. Spade needs weight to get that balance right (to allow it to be self righting and have the toe dig in).

And if someone can tell me the difference between a Bugel and a Danforth welded up (with Peter Bruce's roll bar also welded on I'd be most interested.

And of John Knox, he has been testing anchors for over 20 years, his articles are published in Practical Boat Owner and Yachting Monthly (since the late 90's). He is very highly respected and is one of the few truly independent testers, of anchors - though he last lost that independence since he developed his own product!

Jonathan

[JonJo]

On a more positive note the Knox Anchor was being made from a 900 MPa steel. There has also been a minor modification to the toe of the fluke which is now closed (the slot remains). This was to stop the, then, open slot collecting weed or stones.

If you check the YBW forum, do not recall which, there have been some positive reviews - but it is not that cheap (900 MPa steel is expensive, and expensive to work) and there are not that many in use. If it was cheap (in total) to get to Oz I'd have tested it by now - it looks interesting and is well designed (and from what I hear - well made)

It is obviously a variant on the Danforth, Bugel, Rocna, Supreme, Mantus (roll barred) theme and the, as Noelex suggests, small changes in the Knox design may have a huge impact on performance (or not). It is interesting, as contrary to previous comment and presumably based on 20 years background, that John Knox has gone for the strongest plate he could work with to allow a minimum weight to surface area ratio (and retaining strength). I do not know if the roll bar is also 900 MPa.

Jonathan

[sailorboy1]

I what impact a home made anchor would have if involved in an insurance claim?

[Delancey]

I humbly submit for your consideration Harpoon, the world's first open-source anchor design.

Based on the hard-earned experience of thousands of years living in one of the world's most extreme environments, the indigenous people of the arctic developed an anchor that was quick to set and stay set because their lives depended on it.

Updated for today's yachtsman, I'm thinking this thing would be suitable for any bottom type, do well in weeds and grass, and would be cheap and easy to produce. As drawn it would weigh in around 42 pounds when fabricated from 5/8" mild steel plate with an overall length of about 3 feet and is shown here with 3/8" chain and a 1/2" shackle.

Of course this is my first pass at ripping off someone else's concept, but I think it possible if it's balanced properly it should sink nose down and poke itself in the bottom. I played around with it in 3D and it looks to me like regardless of how it lands on the bottom, once it's pulled on it should set itself just fine. Probably the hard part will be retrieving it.

Any input from other would-be anchor designers? It's all prior art so no one can patent it, I offer it free to the world without copyright demands.

Cheers!

[Delancey]

Sitting here looking at my bow roller I'm thinking it would prolly sit just fine. Maybe add a bracket to hold it secure when pulled aboard.

Also, thought about moving the shackle hole towards the bottom and lengthening the shackle. When pulled sideways this would impart torque to the shank and help steer it when turning.