Open Source Anchor Project

[noelex 77]

Firstly great project.

I do have some concerns about stealing someone's intellectual property. I hope this does not become just measuring and duplicating someone's existing design, but that does not appear to be the aim.

I would not look at producing a Spade like anchor. These are complex and the details have to be just right.

A roll bar anchor is a more realistic target. With this type of anchor the balance is still critical. Home designers/fabricators often make the mistake of thinking a beefier/heavier construction has little draw back in an anchor. Adding weight to the shank will not just reduce the fluke area/ weight ratio of the anchor it will destroy the ability of the anchor to set well. The roll bar mainly stops the anchor staying upside down, or at an extreme angle of heel. The correct setting attitude is very dependent on the weight distribution. Keep the weight out of the shank, the roll bar and the heal of the fluke. Weight in the toe of the fluke is good, but the toe should also be as thin and sharp as possible.

The double plate fluke like the Knox anchor looks like it would be simple, strong, easy construction and would be the best starting point. I don't like the heavy Sarca type shank near the heel where the roll bar attaches. A more conventional shank and roll bar would be easier and may actually perform better.

Good luck.

[Cotemar]

Maybe some of my anchor data will help get some ideas flowing.

Here is an illustration of how the seabed forces act on modern day anchor profiles.

the problem bend on a Convex plow anchor not only
cuts the seabed and pushes it to the sides, but it also loses projected surface area

Flat Fluke, holds the seabed on the face of the fluke and has the most surface area.
This is why Fortress with its sharp tip flukes, once set in a straight one direction pull cannot be beat.

Concave fluke, concentrates and holds the seabed on the face of the fluke, but also loses projected surface area.
It loses less projected surface area than a Convex plow anchor, because the bend angles are smaller

[Shawn67]

"if I have left anything out, please let me know."

I would suggest looking at something like the Raya from a few years ago as well.

Raya Anchor

No hoop, very large surface area to weight ratio and the fluke shaped as a section of a cone. (Which may be difficult to fabricate) I have several of them so I could supply pictures if needed.

Shawn

[Delancey]

Originally Posted by Cotemar

Maybe some of my anchor data will help get some ideas flowing.

Here is an illustration of how the seabed forces act on modern day anchor profiles.

the problem bend on a Convex plow anchor not only
cuts the seabed and pushes it to the sides, but it also loses projected surface area

Flat Fluke, holds the seabed on the face of the fluke and has the most surface area.
This is why Fortress with its sharp tip flukes, once set in a straight one direction pull cannot be beat.

Concave fluke, concentrates and holds the seabed on the face of the fluke, but also loses projected surface area.
It loses less projected surface area than a Convex plow anchor, because the its bend angles are smaller

This is really great, thanks for sharing. I have obviously stated my preference for a concave fluke, but I think the fact that the Bügel is an undeniable success tells you something and that a flat fluke deserves recognition. Personally, I think plow shapes are good for fields but that's what Jonjo said he wanted.

[Delancey]

Originally Posted by Shawn67

"if I have left anything out, please let me know."

I would suggest looking at something like the Raya from a few years ago as well.

Raya Anchor

No hoop, very large surface area to weight ratio and the fluke shaped as a section of a cone. (Which may be difficult to fabricate) I have several of them so I could supply pictures if needed.

Shawn

While unique onto itself, I tend in my mind to lump it together with the Spade- types as not viable in that it depends on the shape-strength of the compound curvature in the fluke to develop the required stiffness. I expect this shape is being produced by being stamped in a big press.

There is nothing wrong with this approach per se, however of our purposes it is too complex and costly to fabricate. Definitely an interesting design though.

[Cotemar]

I am with you on the Bügel anchor being a very good anchor.
It is very easy to make and it has no live patents at this time.
Anyone can make one from scraps if needed. They perform very well.

The Bügel anchor is the one that really started this new generation anchor run we are seeing today.

[Jimbo485]

For a simple design for construction in the 3rd world or on a beach, the Bugel-type is hard to beat.

[noelex 77]

The Bugel type anchor is a great candidate for home construction. The problem is that in many parts of the world there are cheap copies already available for not much more than the cost of making and galvanising one yourself.

For the project to be of value it needs to focus the collective energies to develop a more sophisticated, higher performing anchor. However, the balance of difficulty to performance needs to be right. An anchor like the Spade is going to need a lot of development work and when the design is finished construction will be complex. Something in-between offers the most hope for success.

[Cormorant]

Interesting to imagine a bolt-together Bugel-type anchor, too. Three pieces that can all lie flat somewhere out of the way, to be hauled out and assembled quick and dirty when needed.

[monstads]

Originally Posted by Cormorant

Interesting to imagine a bolt-together Bugel-type anchor, too. Three pieces that can all lie flat somewhere out of the way, to be hauled out and assembled quick and dirty when needed.

First, this thread is incredibly timely, as I was just thinking of making a small stern anchor as practice, before thinking about making a larger primary one. To that end, I would be willing to make a scaled down version of whatever design "evolves". I have a plasma torch, wire feed welder, manual bender and a great metal supply store close..

Second, although I can weld to a certain degree I would put a plug in for a design that has the critical load portions bolted/pinned together. Besides being practical to stow, I also think there might be more room for innovation in how to attach the shank to the fluke(s). No welds would be ideal (imho), but a design that was forgiving/fault tolerent of the welding quality I think would have larger appeal.

[Delancey]

Originally Posted by Cotemar

I am with you on the Bügel anchor being a very good anchor.
It is very easy to make and it has no live patents at this time.
Anyone can make one from scraps if needed. They perform very well.

The Bügel anchor is the one that really started this new generation anchor run we are seeing today.

The Bugel is a great anchor in so many ways, however I think it needs to be recognized that the Bugel didn't come into existence until 15 years after Peter Bruce's US Patent 3,777,695 was awarded. Coincidence? I think not.

Peter Bruce created the new generation anchor over forty years ago. While he never put several of the concepts described in this patent directly into use and instead refined what he thought were important elements of it into the Bruce Anchor, he is none the less the direct progenitor of anything any contemporary anchor designer is doing today.

The Bugel exploited aspects of Bruce's work that were perhaps overlooked in the Bruce Anchor design. I am not sure of the terms of the Bugel Patent which was awarded Germany, but about fifteen years after it was awarded the so called "new generation" anchors as we know them came into being.

As much as I recognize the Bugel is an excellent anchor design, I believe we can design a OSA that is better.

You can see Peter Bruce's US Patent 3,777,695 here- http://www.freepatentsonline.com/3777695.pdf

Funny how it looks kinda like a like a Bugel, Rocna, Supreme, Knox, Sacra, Mantus, or any of the others?

Don't get thrown by the location of the roll-bar fore and aft. Just because it's not at the back of the anchor doesn't mean he didn't invent it, clearly he did.

You have to understand that, except for the last one which was to be forged, these were intended to be be cast in steel. The anchor would have been cast in a green-sand mold made in two halves. The medial line represents the part-line of the mold.

The cast object has to have what is called "draft" which means there cannot be any parallel or overhanging surfaces. Patternmaking is more or less a dying art being supplanted today by CNC machining.

The pattern has to be made slightly oversized to account for shrinkage of the cast piece as it cools. Patterns were generally made from the finest Mahogany available and are in and of themselves works of art. I would love to see the original patterns for the Bruce Anchor, I imagine they are beautiful.

[Delancey]

If helps lend some perspective, the process for producing something like the Bruce Anchor back in the day meant that the design was drafted on paper in three views much the same as a ship's lines.

Once the design was completed, same as building a boat, a table of offsets is developed from which scaled versions are extracted, accounting for whatever the shrinkage is. From there each of the sizes is lofted out in the three views full size. From there you start making templates. From there you start carving wood.

Honduran Mahogany was generally regarded as the preferred species for it's dimensional stability and an anachronistic grade of lumber called "Pattern Grade" represented the largest and finest quality wood available. We're talking giant boards of old growth, quarter sawn 4" thick and 24" wide. Stuff that doesn't even exist anymore, gone.

This all before Computer Aided Drafting or Computer Numeric Cutting. All by hand with nothing but slide rules and calipers, and they made a separate pattern for each size. It blows my mind.

Once that's done you can use the pattern as plug to cast a part, once you can cast a part, you can cast a bunch of parts to use as plugs to make as many parts as you want. And so on and so forth.

The mold consists of a box in two halves, the lower half is placed on the ground and partially filled with the sand. Green-sand is the old school mix of sand and clay, the new stuff is more chemicly. The plug is placed in the mold and sand is rammed around it to the medial line of the plug, the top half of the box goes on and sand is packed in on top.

The plug can't have any parallel surfaces or overhangs for you to be able to extract it when you separate the two halves of the mold. Hence the part you are making has to have "draft" as mentioned.

The two halves of the part are put back together, you melt your metal and pour it in, when it cools you break off the sand an voila, there's your anchor. Casting is a great way to mass produce complex shapes like we see in Peter Bruce's design or say a CQR.

Casting might be a good idea if you were stuck on a desert island and wanted to cast an anchor for a boat you were building to get off the island. It's very basic, you can make a rod by wrapping a wood stick in clay and throwing it in the fire, once it's fired you have a rod shape hole you can fill with metal. When it cools you can break off the clay and beat the rod into a spear and catch some fish to eat while you build your boat and make your anchor.

However, for the purpose of the OSA I think we would do better to stick with an arc welder and a cutting torch to make our anchor.

[Shawn67]

"Interesting to imagine a bolt-together Bugel-type anchor, too."

The Raya "Tempest" models had a nice way of dealing with this. The shank fit into the bottom of the fluke and the geometry of the bottom of the shank/slot in the fluke held all the load. An untensioned bolt just kept the shank from coming back out the bottom of the fluke.




The Bugel shank looks like it could be adaptable to that same design.

Shawn

[Delancey]

Originally Posted by Shawn67

"Interesting to imagine a bolt-together Bugel-type anchor, too."

The Raya "Tempest" models had a nice way of dealing with this. The shank fit into the bottom of the fluke and the geometry of the bottom of the shank/slot in the fluke held all the load. An untensioned bolt just kept the shank from coming back out the bottom of the fluke.




The Bugel shank looks like it could be adaptable to that same design.

Shawn

It's a nice feature, the way it works is that it's tapered. Very strong, like a dovetail. Tapered joints are good.

[Delancey]

Just some more thoughts about casting and also extruding.

Previously I had been talking about sand casting. You can totally cast concavity or what we in the business call "negative space" like if you want to make a statue of a famous general on a horse or a winch drum with a flange on the top and bottom.

The process in its most basic form is called lost wax. Like with the spear you made, you make your object to be cast out of wax and wrap it in clay. When you fire the clay the the wax melts out and leaves a negative space behind in the shape of whatever your thing is.

Classical investment is the name for a mixture of sand and paster of paris, same thing, when you are done you "break the mold" to get your part.

Nowadays it's called ceramic shell investment and uses a thixotropic colloidal silica mixture applied in multiple coats to build a shell. Fire it, pour it, break it. Ceramic shell is capable of capturing fine detail and producing parts very precisely which helps to minimize machining.

The downside to these methods is you loose you wax. That is to say you need a separate wax for each piece you cast which in turn is usually cast from a flexible rubber or silicone mold. This double-casting in and of itself adds significantly to the cost. Compare this to the sand cast method and you can see why it's more widely used of the two.

With any of these casting methods shrinkage varies as a function of part thickness. Back in the day before compooters made us so dum the art in pattern making lay in being able to understand the material and being able to calculate the shrinkage accurately so as to produce the part to the correct finished shape.

Keep in mind machining back in the day wasn't just push a button and the pattern itself represent a a significant investment. You don't want to cast a giant propeller to have the blades come out with the wrong pitch, for example.

The same rules of shrinkage apply to extrusion as well. You can think of extruding as something like a Play Doh's Fuzzy Pumper Barber Shop where the pumper is a big heated press and the Play Doh is molten metal.

The presses are gauged by weight in tens of tons and have maximum extrusion diameters accordingly. If you want to have a hollow shape like a tube or a mast the die needs to have fins and gates upstream of the die parting line to hold the center in place and allow for the metal to flow into the desired shape. Dies can be expensive to produce and have lifespans dependent in wear.

To ensure an accurate extrusion the wall thickness is best kept uniform because of shrinkage. Corners can be sharpish or have a radius. Lengths are extruded in aluminum up to 40' that I know of, possibly longer.

The process includes straightening and tempering dependent on alloy, and can include post forming and rolling. The machines are big and the process is energy intensive.

I have to say that the last time I looked at a Fortress I was impressed by the quality of the extrusion. I remember the width was quite wide, it was really nice stuff. The amount of energy required goes up as you go up in size and the largest sizes can be expensive to produce.

Despite the capital costs extrusions are awesome as can be attested by the fact that you see them everywhere. The extrusion for the flukes on the Fortress is a T-shape where the top of the T lies on edge along the inside of the fluke to provide stiffness to transfer the load from the tip back to the shank.

You can see a similar attempt made to stiffen the shank in the Knox anchor by forming an L out of sheet. It's a fine effort to bend an L but it's no where near as sweet as a nice balanced T section like you see in the Fortress. I never said I didn't think the Fortress wasn't a fine piece of work.