Open Source Anchor Project

[Delancey]

Originally Posted by Bestathook

What about a plain section of a steel cylinder, with a bar across the bottom to attach a stock.

If the length of the cylinder is cut such that the angle of the stock, from the center of one end of the cylinder, to wherever it touches the rim of the other end, is the desired angle of stock to maximize penetration, the anchor will always be in setting position. A bulawaga has a similar arrangement to set angle.

It would be possible to cut a few big teeth, or whatever pattern minimizes penetration.

OK what do you think of this arrangement?

I tried to play around with this but I am not sure I understand what you are thinking. Can you cut up a cardboard tube with a pair of scissors and post a picture? Like from a paper towel or toilet paper roll, whatever. Doesn't have to be anything fancy, just so we can get an idea of what you have in mind.

[Delancey]

Originally Posted by Cotemar

A Delta 20kg-44lbs anchor has a
.629 inch thick shank
.236 inch thick fluke at the back end.
The tip is just a big casting for tip weight.

BTW, thanks for the info. If we don't get any more responses will just go ahead with what we have, probably the spec from the Manson Supreme provided by Panope from the other thread will be fine.

[Delancey]

One shank, one roll-bar, three different flukes gets you three different anchors each weighing 20kg/44lb. Center of effort/resistance is the same on all three flukes. 145, 228, and 288 square inches of fluke area respectively for rock, sand, and mud.

[magicmoments]

I can't wait for a pdf with angles etc. that I can use to build one.
Thanks to all you tech guys for your efforts.

[Cotemar]

Originally Posted by Delancey

One shank, one roll-bar, three different flukes gets you three different anchors each weighing 20kg/44lb. Center of effort/resistance is the same on all three flukes. 145, 228, and 288 square inches of fluke area respectively for rock, sand, and mud.

Not sure what the roll-bar diameter is, but it appears to be on the thin side. The concern I would have is when the anchor come down on the roll-bar in soft seabed and sinks in, instead of rolling onto the fluke.

The rest of the design looks sweet.

[noelex 77]

A couple of thoughts.
I am not sure the anchor on the right (the "mud" version) will work (although if used just in soft mud almost anything will set). In the setting position there is very little force place on the tip. It would dig in first with the shoulder of the blade.

The other two look good, but a compromise between the two would be more versatile and suffer very little in performance. It is going to be difficult enough to develop one anchor and to optimise its geometry. I think three different flukes is spreading the resources too thinly.

I would not try and develop a "rock" anchor. Rock prevents the anchor diving so all the work to develop an an modern anchor is wasted. An anchor with multiple flukes like a grapnel is much better than most and its important the anchor be cheap and readily disposable if you really want to try anchoring in rock.

If by "rock" you mean smooth rock with a thin sand layer over the top, this is a more laudable goal, as this is a more common, difficult substrate, but it requires an anchor with the opposite a big blade area.

The far left anchor "rock" could be very good in thick weed, but it depends what is under the weed. If it soft mud or thin sand over rock it will not work as well as a more moderate design.

One great advantage of the good modern anchors is that they work well in nearly every substrate. If you develop multiple flukes like you propose they will give up this versatility .The specialist anchors you are proposing have the potential to be poor if used in the "wrong" substrate. It is often very difficult to know which anchor to use when you have a choice. Substrates can vary within the one anchorage and the pilots books are rarely accurate about the bottom type. Even when you know there is "weed" on the bottom for example what is under the weed would still effect the chosen fluke.

[Delancey]

Originally Posted by Cotemar

Not sure what the roll-bar diameter is, but it appears to be on the thin side. The concern I would have is when the anchor come down on the roll-bar in soft seabed and sinks in, instead of rolling onto the fluke.

The rest of the design looks sweet.

The roll bar is something I am very interested in getting feedback on.

In light of the fact that it's sole purpose is to right the anchor when it lands upside down, I am at a loss to understand why they are typically made out of what looks to me like way oversized tubing.

I get it that an anchor is a consumer product and the expectation is that it will keep it's shape throughout its lifetime. So we make roll bars out of big tubing so they never bend.

My concern with this is two-fold. One, big tubing means more frontal area to resist penetration. Two, if that oversize tubing roll bar gets caught on a rock, are you going to bend your shank because the roll bar won't give way?

Perhaps it is better to bend a roll bar than a shank? Maybe be better to have a roll bar of a more appropriate size for its task with the expectation that if it ever bent, you as the maker of the anchor would have the skill necessary to bend it back?

In the previous three anchors, the roll bar shown is 1/2" solid round bar about three feet long with an inch of threads cut on the ends, about as simple as I could make it.

Here is another one made out of 1/4" x 1" rectangular bar stock which has half the frontal area of the 1/2" but twice as much surface area to resist sinking in a soft sea bed as you suggest. 1/4" would be easier to bend also.

Am I missing something here? Why are roll-bars usually so big?

[Delancey]

Originally Posted by noelex 77

A couple of thoughts.
I am not sure the anchor on the right (the "mud" version) will work (although if used just in soft mud almost anything will set). In the setting position there is very little force place on the tip. It would dig in first with the shoulder of the blade.

The other two look good, but a compromise between the two would be more versatile and suffer very little in performance. It is going to be difficult enough to develop one anchor and to optimise its geometry. I think three different flukes is spreading the resources too thinly.

I would not try and develop a "rock" anchor. Rock prevents the anchor diving so all the work to develop an an modern anchor is wasted. An anchor with multiple flukes like a grapnel is much better than most and its important the anchor be cheap and readily disposable if you really want to try anchoring in rock.

If by "rock" you mean smooth rock with a thin sand layer over the top, this is a more laudable goal, as this is a more common, difficult substrate, but it requires an anchor with the opposite a big blade area.

The far left anchor "rock" could be very good in thick weed, but it depends what is under the weed. If it soft mud or thin sand over rock it will not work as well as a more moderate design.

One great advantage of the good modern anchors is that they work well in nearly every substrate. If you develop multiple flukes like you propose they will give up this versatility .The specialist anchors you are proposing have the potential to be poor if used in the "wrong" substrate. It is often very difficult to know which anchor to use when you have a choice. Substrates can vary within the one anchorage and the pilots books are rarely accurate about the bottom type. Even when you know there is "weed" on the bottom for example what is under the weed would still effect the chosen fluke.

Maybe "rocky soil/weeds" weeds is better than to say "rock" as I agree that's what grapnels are for.

I could have it wrong, but I was under the impression that rocky soils were hard to penetrate but offered higher holding power, whereas mud was relatively easy to penetrate but offered comparatively less holding power. Hence small and narrow for rocky soil, big and wide for mud.

I haven't yet played with these designs to see how they work in the pre-penetration position. Yes the curved edge to the mud anchor is less than favorable in terms of angle of attack, but that curved edge is also like the curved edge to a samurai sword blade in as much as all of the force is focused on the single point of contact where the curve meets the flesh. The general shape of the mud fluke as I have it is of course inspired by the common shovel.

As far as the single design/multiple designs go, I am thinking in general that's it's good to have options in life whether or not you actually use them. With a single shank design I don't see being too big of a burden to provide those options for those who want them. So, why not?

[Cotemar]

Originally Posted by Delancey

The roll bar is something I am very interested in getting feedback on.

Am I missing something here? Why are roll-bars usually so big?

Roll-bars tend to be larger round tubing for strength in all directions. The larger diameter also gives them a bit of rolling action on the seabed floor verses a smaller diameter which may act as a cheese slicer and dig or carve into the seabed.

[Delancey]

Originally Posted by Cotemar

Roll-bars tend to be larger round tubing for strength in all directions. The larger diameter also gives them a bit of rolling action on the seabed floor verses a smaller diameter which may act as a cheese slicer and dig or carve into the seabed.

I think Peter Smith of New Zealand might disagree with you on that one. Per his US Application filed Sept. 15,2012 which you can see here-

Anchor

[Cheechako]

a 1/4" flat stock roll bar will be a pretzel rather quickly.....

[Cotemar]

Originally Posted by Delancey

I think Peter Smith of New Zealand might disagree with you on that one. Per his US Application filed Sept. 15,2012 which you can see here-

Anchor

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.

[Delancey]

Another thing I am looking for guidance on, shanks.

Here the shank you've already seen, and below it one from a 25kg Delta. I am only guessing at the CE for the Delta but I think I have it roughly aligned fore and aft with the one above it.

My rusty old CQR that came with my boat doesn't sit very nicely in the cast aluminum bow roller that came with the boat. The fluke digs into the stem and chips my gelcoat and in any kind of a seaway I do well to tie it off so any benefit of the anchor "seating" into the roller is lost.

The shank I have drawn is obviously modeled off of the Bugel shank, which I like for its typically German brutally elegant simplicity. It should fit on any bow roller up to 4" in diameter. Unlike the crooked shank, the Bugel-style can be significantly lighter which means more fluke surface area because it doesn't need so much meat behind it to get around the crooks.

So here's the question, does the OSA have to have a crooked shank? Or is the Bugel-styled straight shank acceptable?

To address the HOE concept, I looked at it early on when I was thinking you were going to end up with an anchor welded from a shank and two triangles cut from plate.

Since we are going weldless, without a reliable way to make a connection between the tip of the HOE hook and the tip of the fluke there is no real structural bennefit to going this route and you end up with a shape that nests poorly out of a sheet of stock.

If the fluke thickness is appropriate, any additional material is redundant. Without a connection between the two tips, if they deflect, they will deflect independently without supporting each other.

With the through-hole cantilever connection between the shank and the fluke, we the enjoy the benefit of stacking different plate thickness for different purposes. For example the middle of the three has a 1/2" shoe that extends from the shank connection down to a cat's paw shaped chisel point on the tip.

Meanwhile the larger area of the fluke itself is formed from 1/4" thick plate. Together they give you 3/4" thickness from shank to tip. I haven't drawn it but the connection between the shoe and the fluke could be rivets (my fav) or bolts.

To anyone who still isn't so keen on my through-hole cantilever connection for the shank to fluke I found some prior art on that one, it goes wayyyyy back.

[Delancey]

Originally Posted by Cheechako

a 1/4" flat stock roll bar will be a pretzel rather quickly.....

Beyond my personal experience but we're here to learn right?

What about the whole bend a roll-bar instead of bending your shank thing? Or is that just in my head?

I mean, if you ever did bend the roll bar you would know it when you retrieved it, swap out a spare or bend it back, right? I mean sure, bend a shank, swap out a spare. Seems easier to bend a roll bar back into shape than a shank, just saying.

Much less consequence to any work hardening or fatigue that could occur by bending and re-bending the roll bar cold as opposed to bending and re-bending the shank. Or are roll bars just not contributors to shank bending?

[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?