Open Source Anchor Project

[Shawn67]

"bet you could make it self righting and ditch the roll bar."

You might also want to add the little wings that are on the Raya and Spade anchors. They keep the back corners of the fluke from trying to dig in when the anchor is initially being set.

Shawn

[colemj]

Originally Posted by Shawn67

I have three Raya anchors.

Perhaps I misunderstood the owner. He has two massive Raya's (75kg - he said they were the "3000"), and perhaps these were the only two of that model made - not the only two Raya's like I thought he said.

How do yours work?

Mark

[Shawn67]

Probably that size Raya is what that owner was talking about. I know of a few others that have Raya 600s or Tempest 800s as well as some big ones. Joao had told me I have the only Tempest 400 made. Everything I have seen written by owners has been positive.

I've used the 800 the most. It sets extremely quickly and haven't had it break free. Comes up clean (much more than a similar weight genuine Bruce that feels twice as heavy when retrieving it) with only a little mud/sand near the point/shank.

Only once have I had an issue. When I dropped it it set but as I was power setting it I was dragging it at about 1/4 of a knot at full throttle. I think I may have hooked something that time as I have never had any issues in the same location. Maybe a branch under the shank as it was burying? I redropped it and it set and held instantly.

I'm a weekender/overnighter so haven't had this out in terrible conditions. Worst would have been 20-25 knots winds with 2-3 foot waves that built up when I was off in the dinghy on an island. Didn't budge at all. I have about 38' of 3/8 chain on the anchor and then 1/2" double braid after that.

I haven't used the 1000 at all, it is waiting for a larger boat. I bought the 1000 off ebay as I have been impressed with the 800 and knew I wasn't going to find another larger one again. It wasn't labeled as a Raya, just a plough and I happened to luck into finding it on ebay. Not much else out there that has the surface area/weight ratio of the Rayas.

Shawn

[Delancey]

I've been letting this one gel in my head a bit, the more I do the more I think this shank/fluke connection is a total slam dunk. Anchors are kinda of a funny thing because they are a one-way street in terms of load and you can't push on a rope.

With this connection we are letting the load do all the work to hold the parts together. I am surprised no one ever noticed this before but it's a funny thing about how our notions of how the world should be influence our design process.

Makes me think of the design of hand saws for wood. For the west our notion of wood cutting is all about getting rid of material, eliminating it, making it go away. Hence our western hand saw cut on the push.

By contrast Japanese saws were designed with a buddhist philosophy in mind and they cut on the pull stroke because the intention is not to get rid of the wood but to bring the work towards your heart.

A nice thing about this whole "bring the work to your heart" is that the material of the saw, being used strictly in tension, is being used at it's greatest efficiency. That is to say because it is being used to cut in tension, it can be thinner resulting in a narrower saw kerf, which means less effort goes into cutting.

I think a typical engineering approach to designing something like this fluke/shank connection is to think that we need to make a connection. We need to join it, we need to weld it, we need to bolt it, whatever. What we really need to is take a step back from trying to control the world around us and instead let it do our work for us.

This connection really gives us a lot of options. I think it's huge to not have to weld. The fact that it readily allows for the use of dissimilar metals is just as huge. Tool steel shank and aluminum fluke is obvious, I am thinking more along the lines of Bestahooks ideas about third world creativity.

You want a concave fluke? Cut one out of a propane cylinder. Doesn't matter what metal it is made from, doesn't matter what your shank is made from. What matters is that there is a shape you need lying there doing nothing usefull. Put it to work! Lazy propane cylinder, shame on you.

For those of you who need a real would example of this connection put to practical everyday use I have attached a couple of images of drywall anchors that exploit this connection. 50lbs hanging off a piece of wire stuck in drywall? I think this connection will do just fine.

[Paul Elliott]

Originally Posted by Delancey

[...] With this connection we are letting the load do all the work to hold the parts together. [...]

Case in point is the Spade. The bolt that secures the shank to the fluke isn't carrying any load. The anchor is designed so the anchoring load itself holds the shank in place. The bolt is there to keep the pieces together when there is no load.

[monstads]

I like it! As I mentioned above, little to no welding is better (imho). Another thought.. What if you had different flukes for different conditions? Seems like some shapes might be good for predominately mud/loose sand, others for tough grass, etc. Why not have separate, specialized flukes instead of suboptimizing the design to make it work the widest possible audience?

[Delancey]

Originally Posted by monstads

I like it! As I mentioned above, little to no welding is better (imho). Another thought.. What if you had different flukes for different conditions? Seems like some shapes might be good for predominately mud/loose sand, others for tough grass, etc. Why not have separate, specialized flukes instead of suboptimizing the design to make it work the widest possible audience?

Love it! When I first started thinking about this project I thought to make it doable, best to set the bar low and just try to make a simple anchor that was good but not great, not the best. You can't make all people happy all the time.


Maybe that paradigm just changed....

[Delancey]

Originally Posted by Paul Elliott

Case in point is the Spade. The bolt that secures the shank to the fluke isn't carrying any load. The anchor is designed so the anchoring load itself holds the shank in place. The bolt is there to keep the pieces together when there is no load.

True, my bad to say no one ever thought of it before. Props to the frenchman!

[Delancey]

It doesn't look quite like our shank, but what is going on with the drywall anchor is that gravity is acting like the load on our shank imposed by our boat, the drywall wall is our fluke.

[noelex 77]

I am no metal fabricator, but the fluke/shaft joint looks a difficult project for the amateur constructor.

It has to have very little play. The spade fluke /shank joint has not been without its problems. It traps mud which together with even a tiny bit of wear leads to a lot of corrosion in a structurally important area of the anchor. The first Spades suffered very badly from this. They replaced them, and the new design is better, but it still has some problems.

An aluminium shank is a good idea. However the spade Shank /fluke design is not suitable for this. It would be impossible to electrically isolate the steel and aluminium to any reasonable degree. It would be possible with the bolt on type Mantus fluke, but this would require a welded aluminium foot on the shank and aluminium welding is not a skill many amateurs possess especially for a structurally important piece.

I think you may be over complicating this. The welded fluke shank joint is used by most anchors and is the cheapest, easiest method.

[Delancey]

Originally Posted by noelex 77

I am no metal fabricator, but the fluke/shaft joint looks a difficult project for the amateur constructor.

It has to have very little play. The spade fluke /shank joint has not been without its problems. It traps mud which together with even a tiny bit of wear leads to a lot of corrosion in a structurally important area of the anchor. The first Spades suffered very badly from this. They replaced them, and the new design is better, but it still has some problems.

An aluminium shank is a good idea. However the spade Shank /fluke design is not suitable for this. It would be impossible to electrically isolate the steel and aluminium to any reasonable degree. It would be possible with the bolt on type Mantus fluke, but this would require a welded aluminium foot on the shank and aluminium welding is not a skill many amateurs possess especially for a structurally important piece.

I think you may be over complicating this. The welded fluke shank joint is used by most anchors and is the cheapest, easiest method.

Taper joints require a fair amount of precision to work properly. The mating surfaces need to be co-planer so that the load forces are distributed over the entire surface, otherwise you have point loading and the deformation that can result.

This joint doesn't work like that at all, it's a simple lever against to fixed points. By it's nature it allows for imprecision. Because there are no other conflicting components you can pack on the mass where you need it to make it as strong as you want.

I used this joint in a knock-down cafe table I designed about six months ago. The four legs get inserted into their respected holes and are rotated into position. The top is hollow. The legs get deflected slightly to allow a block to be inserted into a notch in the legs. The whole thing holds itself together.

I guess if you had to give it a name you would call it a "through- hole cantilever". The first time I saw it was years ago on a crappy foam-core point of purchase display. I rennet at the time thinking "gee, that's neat!".

Thanks consumerism!

[Cotemar]

Here is a self righting anchor with a chisel tip.

Its as simple as it gets.

[nimblemotors]

As I suggested in the other thread, I would make an anchor out of fiberglass.
The shank would fit into a slot as in post 104,
but would be 5x thicker in the bottom part, and just bolt it in.
Maybe make the shovel part from aluminum, or a core of steel covered in fiberglass.
This makes the base heavy and the shank lighter, it will land on the ground with the base down.

The thing is with a fiberglass shaft if you attach the chain to the front and then a lead to the back hole, if it breaks (not bends) when retrieving it, it remains attached to the back hole and it should then pull out and not stay stuck. Then just replace the shank part when you get back your shovel. You can have many extras, they will weight very little.

[Delancey]

Originally Posted by nimblemotors

As I suggested in the other thread, I would make an anchor out of fiberglass.
The shank would fit into a slot as in post 104,
but would be 5x thicker in the bottom part, and just bolt it in.
Maybe make the shovel part from aluminum, or a core of steel covered in fiberglass.
This makes the base heavy and the shank lighter, it will land on the ground with the base down.

The thing is with a fiberglass shaft if you attach the chain to the front and then a lead to the back hole, if it breaks (not bends) when retrieving it, it remains attached to the back hole and it should then pull out and not stay stuck. Then just replace the shank part when you get back your shovel. You can have many extras, they will weight very little.

I think by the time we are done with the OSA we are going to end up with a design adaptable to composite panel fabrication. Especially now that we got rid of that pesky weld.

The thing to look out for when adapting to composite is the fact that metal is isotopic and composite panels are anisotropic. Metal behaves the same in all directions. The inherent strength and stiffness of composite materials lies aligned with the fiber axis.

Not to say it can't de done. Just saying it would be hard to make it as light as possible using a stock panel, a custom layup would get you closer to where you want to be.

I think it's an interesting suggestion to think of more resilient materials. The shank that would bend but not break. One problem with fiberglass is that it suffers from poor cyclic fatigue resistance. Now think of your boat riding at anchor, wave, after wave, after wave. Maybe a Kevlar/carbon fiber mix would be a better choice.

[Delancey]

Originally Posted by Cotemar

Here is a self righting anchor with a chisel tip.

Its as simple as it gets.

We need to get over the weld quickly

Anybody who can drill a hole in something flat, and can stick a rod into that hole, and can then try and bend that rod can make this joint.

The mission is design an anchor accessible to anyone anywhere. Now that we have a no-brainier mechanical connection welding is a waste. In addition to the tools and skills to use them, it requires a great deal of energy.

Conservation of resources is quintessential to the project objective. You could spend a hundred hours debating anchor warranties on CF with the energy required to make one welded OSA.

As for the other bit, we're not ready to right our anchor just yet. We need to look at developing some lateral stiffness first but to do that we need to draw out a couple things. I'll get to it as soon as I can.

One suggestion has been made to use the roll-bar, which is a good one (lazy roll bar, shame on you!) but there are some other ways I can think of.

Maybe you guys can think of some too.