Open Source Anchor Project

[Delancey]

Originally Posted by Cotemar

Peter Smith may disagree with me in his patent filing, but he does agree with me in real life, as he put a larger diameter on his actual production anchors after his testing showed the seabed floor was getting carved up as the narrow roll bar dug in.

This recent Patent Application looks to me like a possibly new-to-market design I don't see featured on their website.

It basically looks like a further refinement of their basic design borne out in cast steel which you can see in the varied tapered sections. Not sure if this is being built, if their testing it, if it will go into production, or what. Looks like a nice design though.

With our bolt on connection from roll bar to fluke it would be pretty easy to try out both and prove the point when we get that far. If it has to be big fat tubing, you can still thread ends of pipe and make the same connection with the fluke.

It's just that usually you need fairly substantial tools to bend the pipe and cut the thread, so if we can make due with some solid bar of some type, all the better.

[Delancey]

Here's another thing about flukes- I always thought the Mantus fluke was a smart design.

Take a flat piece of any given size, not very strong. Bend it once in the middle, you develop shape strength along the fold and reduce your unsupported panel by half. Now take that same panel and fold it twice into thirds, see where this is going....

Turns out there's another potential benefit to having a flat spot where the shank lands on the fluke, check out the abstract on this Peter Bruce Patent from 1979 - Peak Pressure Zones, pretty nifty.

Anchors

[Delancey]

Originally Posted by Cheechako

I'm wondering if a strut from the shank to the roll bar on center to stabilize the roll bar really has any deteriment?

Like in the original Bruce Patent? Or the Knox Anchor? I have thought about it.

[Delancey]

Here are the three in pre-penetration position. That shovel fluke doesn't look so good, prolly needs some work. That said, if it's going into mud with little resistance then that curved knife edge maybe isn't so bad. I think the other two look fine so far.

[Bestathook]

In regard to the fat roll bar, thin roll bar decision, how about a bent steel bar with beads on it to increase its resistance to digging in?

We would only have to deal with bending and forming a piece of bar or strap steel.

The beads could be cut out of a suitable piece of pipe, say 2 inch sections of 2 inch pipe. They would act like rollers to prevent digging in.

I am also trying to predict the result of various angles on the roll bar. The limits would be avoiding a hooking edge toward the eye, that would catch on rock edges, etc. With the angle away from the stock's eye, avoiding an angle that would cause the anchor to skid along upside down, roll bar down is a limit. But in between, what angle between the plane of the roll bar and the overall plane of the fluke, is optimum?

[Delancey]

Originally Posted by Bestathook

In regard to the fat roll bar, thin roll bar decision, how about a bent steel bar with beads on it to increase its resistance to digging in?

We would only have to deal with bending and forming a piece of bar or strap steel.

The beads could be cut out of a suitable piece of pipe, say 2 inch sections of 2 inch pipe. They would act like rollers to prevent digging in.

I am also trying to predict the result of various angles on the roll bar. The limits would be avoiding a hooking edge toward the eye, that would catch on rock edges, etc. With the angle away from the stock's eye, avoiding an angle that would cause the anchor to skid along upside down, roll bar down is a limit. But in between, what angle between the plane of the roll bar and the overall plane of the fluke, is optimum?

I like the roller idea, could be interesting.

As far as the roll bar geometry and how it relates to the shank/fluke goes, I can work up a simple model that illustrates the relationships.

[Delancey]

Ok, let's look at how the roll bar works. First we need to think about stability in general terms. There are three states: actively stabile, neutral, and actively unstable. These states apply if we are designing a sail plan, making boat self-steer, flying an airplane, whatever. In our case we are looking for form stability as it relates to our self righting anchor.

If something is actively stable, it is resisting whatever force is acting on it, such as gravity or the force of the wind on your sails. Imagine a ball bearing in a bowl. If I push on it, gravity pulls it back to the middle and there it stays. The relationship between the bearing and the bowl is one of active stability.

Now if you put that ball bearing on a plate, it also just sits there seemingly stable, but if I push on it, it will react and move until whatever inetria I give it is overcome by friction and it stops. This is neutral stability.

Lasty, active instability. I flip the bowl upside down and put the ball bearing on top. The bearing rolls down hill no matter what. Like an upside down pyramid, or an anchor resting on it's roll bar.

If I am making a boat self steer I am looking for the first one. The boat can pitch, yaw, whatever. My sheet to tiller or wind vane is constantly working like the bearing in the right side up bowl to resist whatever force is working on it.

If I am making an anchor, I want a shape that is actively unstable in any position other than pre-penetration, where I want a shape that has active stability like I can get with a tripod.

Now let's put this to work with a generic anchor. The fluke is an isosceles triangle 16" wide at the base and 16" tall. The shank is 36" long and is attached to the fluke at the center of effort/resistance at a 33 degree angle.

In the first image on the left is the anchor plumb with the tip of the shank and the tip of the fluke aligned with the bottom, ready to set. Problem is it's actively unstable and going to fall on it's side.

No problem, then it's a tripod in the pre-penertation position, like the one on the right. I will add here that if we give the fluke a bird's beak it will be stable in this plumb position resting on the two points of the bird's beak and the shank to make a tripod, but that's neither here nor there.

Unfortunately, our generic anchor doesn't yet have a roll bar so if it lands upside down like in the middle, it's actually in a position that is more actively stable than in the pre-penetration position. No coming back from that one.

So, let's give our generic anchor a roll bar. The fluke shape doesn't matter, it can be convex, concave, flat whatever. To design our roll bar we need to strike a line across the anchor from the widest points of the fluke.

Then we need to draw another line that goes from the top center of the shank and runs the length of the anchor and intersects with the center point of the first line. These two lines define a plane. If we make another plane perpendicular to the first that intersects with the line across the flukes, we draw a half-circle in that plane. Our roll bar design is done!

When the anchor lands upside down, and if the roll bar doesn't get stuck in the mud, it has an actively unstable form and gravity will cause it to roll one way or the other until it falls into the pre-penetration position.

When you look at the side view you can see how the shape of the shank is irrelevant. It can be crooked as a corkscrew as long as it doesn't go outside the zone of the roll bar. If we wanted to go outside the zone we could do so with a roll bar that was an arc that was greater than a half circle and wider than the wide point of our fluke.

One more bit about the angle of the roll bar fore-and-aft when viewed from the side. It's okay if it's not perfectly perpendicular to the axis from the top of the shank to the center of the fluke width.

If you cant it forward or aft what you will see when looking down the axis will be an ellipse that has a softer radius in the middle and tighter on the outsides of the fluke. Still has the unstability we are looking for, just not as much as a half circle. We could make it any angle and shape our roll bar in an ellipse so it looks like a half circle when we look down the axis, but I digress.

Maybe time to start designing flukes that are optimized for penetration….

[Bestathook]

I'll be darned if this old dog isn't learning a few new tricks from this project.

I love it! ! !

[Cheechako]

Originally Posted by Delancey

Ok, let's look at how the roll bar works. First we need to think about stability in general terms. There are three states: actively stabile, neutral, and actively unstable. These states apply if we are designing a sail plan, making boat self-steer, flying an airplane, whatever. In our case we are looking for form stability as it relates to our self righting anchor.

If something is actively stable, it is resisting whatever force is acting on it, such as gravity or the force of the wind on your sails. Imagine a ball bearing in a bowl. If I push on it, gravity pulls it back to the middle and there it stays. The relationship between the bearing and the bowl is one of active stability.

Now if you put that ball bearing on a plate, it also just sits there seemingly stable, but if I push on it, it will react and move until whatever inetria I give it is overcome by friction and it stops. This is neutral stability.

Lasty, active instability. I flip the bowl upside down and put the ball bearing on top. The bearing rolls down hill no matter what. Like an upside down pyramid, or an anchor resting on it's roll bar.

If I am making a boat self steer I am looking for the first one. The boat can pitch, yaw, whatever. My sheet to tiller or wind vane is constantly working like the bearing in the right side up bowl to resist whatever force is working on it.

If I am making an anchor, I want a shape that is actively unstable in any position other than pre-penetration, where I want a shape that has active stability like I can get with a tripod.

Now let's put this to work with a generic anchor. The fluke is an isosceles triangle 16" wide at the base and 16" tall. The shank is 36" long and is attached to the fluke at the center of effort/resistance at a 33 degree angle.

In the first image on the left is the anchor plumb with the tip of the shank and the tip of the fluke aligned with the bottom, ready to set. Problem is it's actively unstable and going to fall on it's side.

No problem, then it's a tripod in the pre-penertation position, like the one on the right. I will add here that if we give the fluke a bird's beak it will be stable in this plumb position resting on the two points of the bird's beak and the shank to make a tripod, but that's neither here nor there.

Unfortunately, our generic anchor doesn't yet have a roll bar so if it lands upside down like in the middle, it's actually in a position that is more actively stable than in the pre-penetration position. No coming back from that one.

So, let's give our generic anchor a roll bar. The fluke shape doesn't matter, it can be convex, concave, flat whatever. To design our roll bar we need to strike a line across the anchor from the widest points of the fluke.

Then we need to draw another line that goes from the top center of the shank and runs the length of the anchor and intersects with the center point of the first line. These two lines define a plane. If we make another plane perpendicular to the first that intersects with the line across the flukes, we draw a half-circle in that plane. Our roll bar design is done!

When the anchor lands upside down, and if the roll bar doesn't get stuck in the mud, it has an actively unstable form and gravity will cause it to roll one way or the other until it falls into the pre-penetration position.

When you look at the side view you can see how the shape of the shank is irrelevant. It can be crooked as a corkscrew as long as it doesn't go outside the zone of the roll bar. If we wanted to go outside the zone we could do so with a roll bar that was an arc that was greater than a half circle and wider than the wide point of our fluke.

One more bit about the angle of the roll bar fore-and-aft when viewed from the side. It's okay if it's not perfectly perpendicular to the axis from the top of the shank to the center of the fluke width.

If you cant it forward or aft what you will see when looking down the axis will be an ellipse that has a softer radius in the middle and tighter on the outsides of the fluke. Still has the unstability we are looking for, just not as much as a half circle. We could make it any angle and shape our roll bar in an ellipse so it looks like a half circle when we look down the axis, but I digress.

Maybe time to start designing flukes that are optimized for penetration….

What if the anchor was an equal sided triangle of sorts and the flukes were symmetrical around the shank? All sides are useable and no roll bar. Doesnt matter how it lands.

[Jimbo485]

Originally Posted by Cheechako

What if the anchor was an equal sided triangle of sorts and the flukes were symmetrical around the shank? All sides are useable and no roll bar. Doesnt matter how it lands.

Like a mushroom anchor?

[Cheechako]

yeah, kinda ....with improved sharper flukes and longer shank.... Each triangle with a center bend for stiffness maybe. I guess one problem is using it on older boats with a bowsprit and roller on the side of the sprit or platform.

[Cotemar]

Originally Posted by Cheechako

yeah, kinda ....with improved sharper flukes and longer shank.... Each triangle with a center bend for stiffness maybe. I guess one problem is using it on older boats with a bowsprit and roller on the side of the sprit or platform.

It has some of these elements in it.
It's a folding anchor.

[Cheechako]

I'm thinking something like this. I had to make a paper model... a little tedius...
* The base/center of the fluke assembly would l ikely be somewhat smaller than shown and cupped in the forming process rather than flat.
*Each fluke would have some sort of gussett welded to the shank on centerline. (not shown)
* the whole Fluke "pan" could be formed on a Cincinatti 32" hydroformer one piece with no welds... including the cupping and bent ridge in the flukes.
* After forming the shape could be cut by laser or similar allowing changing the fluke shape away from a true triangle... maybe each point on the "base" triangle would have a mini fluke... a bit like the tips of a Bruce...or...?

[Cotemar]

Originally Posted by Cheechako

I'm thinking something like this. I had to make a paper model... a little tedius...
* The base/center of the fluke assembly would l ikely be somewhat smaller than shown and cupped in the forming process rather than flat.
*Each fluke would have some sort of gussett welded to the shank on centerline. (not shown)
* the whole Fluke "pan" could be formed on a Cincinatti 32" hydroformer one piece with no welds... including the cupping and bent ridge in the flukes.

Now I get it. Wow, very nice model you made

[Delancey]

Originally Posted by Cheechako

I'm thinking something like this. I had to make a paper model... a little tedius...
* The base/center of the fluke assembly would l ikely be somewhat smaller than shown and cupped in the forming process rather than flat.
*Each fluke would have some sort of gussett welded to the shank on centerline. (not shown)
* the whole Fluke "pan" could be formed on a Cincinatti 32" hydroformer one piece with no welds... including the cupping and bent ridge in the flukes.
* After forming the shape could be cut by laser or similar allowing changing the fluke shape away from a true triangle... maybe each point on the "base" triangle would have a mini fluke... a bit like the tips of a Bruce...or...?

This is so awesome!

Mad props on the creativity, origami is an excellent source of inspiration. Looks a lot more innovative than anything out there on the streets right now.

Before anybody laughs and says no-way, I think what you are getting at here has merit and is demonstrated by the fact that there is a Patent out there from the Fifties I have seen that played off the same idea. I will have to see if I can find it.

It was double-ended and obviously didn't work because you've never seen it, but bringing a triangle to the table could be a deal maker. There are geometry issues that would need to be worked out but I might have a trick up my sleeve for a self-aligning fluke to shank connection that could make it work.

Folds can develop stiffness which is always a good thing and they are cheaper than dirt. If you have a metal break you can make them all day long. That said, to be a successful OSA we need to keep our guy on the beach in mind, so any solution that keeps it simple will be best.

Can we see a side view and maybe a detail so we can get a little better idea about how you have the folds worked out? I can sort of guess but more images would help.

Again, nice work with the fresh idea! If you could make it work the problem with it might be that it was unretrievable, believe it or not.