Open Source Anchor Project

[Delancey]

Originally Posted by Jimbo485

Bla bla bla

This is starting to get boring.

Delancey, if you want me to build a 30 kg anchor and test it in real conditions, I need the files. If you want to see the momentum lost, just carry on as you are.

Sorry about the abruptness. I am engineer myself but too much talk does not help at this point.

A man of action, I like it. As mentioned I can't send anybody anything until after the New Year but when I do I will post what I have for the 20kg/44lbs version to the opendesign website Foolishsailor has set up as well as email direct to anyone who wants to PM me.

I think it important we go through the process of proof testing as well as side loading but the last thing I want to do is stand in the way of progress.

If you want to give me an idea of what material thickness you think is appropriate for a 30kg/66lbs version I will be happy to work it up and pass it along. Also, some idea of what the working load for that size would be. FEA is great, but not requisite and you are an engineer so I say go for it!

[Delancey]

So, side loading...

...just because there is no "standard" for evaluation doesn't mean we can't make our own. What would that be?

Bent shanks do happen, so far as I know no one has ended up on the beach as a result so I tend to favor the "have a spare shank onboard" approach. Others see things differently.

To keep the design accessible thinner is better but there is a big difference in stiffness between .500" and .625" but not a big difference in cost. I favor a low baseline. With a roll bar design that utilizes geometry instead of CG to provide self-righting, the consequence of beefing up the shank is I believe incidental.

So where does our low baseline lay?

[vientoman]

Since most good design comes from iteration, it seems like a good way to move a few of these ideas forward is to buile a few as a reference point and go from there. I too am a mechanical engineer and would gladly have a few anchors built and tested. Going a bit more, if an anchor design were to show promise, I would be glad to have them quoted, built, galvanized and could even help in shipping them off to those who want to take part in real world testing.

If someone has a design that they think will make a good starting point, post .dxf files and I'll have one built for the good of the cruisers forum.

[JonJo]

Originally Posted by Delancey

A man of action, I like it. As mentioned I can't send anybody anything until after the New Year but when I do I will post what I have for the 20kg/44lbs version to the opendesign website Foolishsailor has set up as well as email direct to anyone who wants to PM me.

I think it important we go through the process of proof testing as well as side loading but the last thing I want to do is stand in the way of progress.

If you want to give me an idea of what material thickness you think is appropriate for a 30kg/66lbs version I will be happy to work it up and pass it along. Also, some idea of what the working load for that size would be. FEA is great, but not requisite and you are an engineer so I say go for it!

Some of the offspec Roncas, built from the Q420 steel did bend. The identical design but built from (last reported as Q620) have not been reported as bending (correct me if I am wrong). I'm not aware that any original NZ or Canadian Bis 80 (A 514) shanked Rocnas ever bent (again correct me if I am wrong).

Some of the Q420 shanks might have bent becuase they were 'abused' - but assuming most anchors are abused - then A 514 anchors have not bent.

Somewhere between Q420 and Q620 (for that shank design) is the point at which the shanks might be considered by some as not strong enough (but certainly A 514 is/was strong enough, Q620 might be on the margin, might be more than enough). You ought to be able to work backwards to calculate at what load a Q420 would bend etc - this might give a basis to define a side load test - you can then add whatever safety margin you desire (but as A 514, to that profile, look indestructible then this might give a basis for the safety margin).

You could, of course, decide that having a few bent shanks, in 100, or 1,000 is a risk you can take.

Jonathan

[Delancey]

Originally Posted by vientoman

Since most good design comes from iteration, it seems like a good way to move a few of these ideas forward is to buile a few as a reference point and go from there. I too am a mechanical engineer and would gladly have a few anchors built and tested. Going a bit more, if an anchor design were to show promise, I would be glad to have them quoted, built, galvanized and could even help in shipping them off to those who want to take part in real world testing.

If someone has a design that they think will make a good starting point, post .dxf files and I'll have one built for the good of the cruisers forum.

Hi Vientoman,

Thank you for your offer of material support for the project. So far we have developed a concept for a super simple mechanical connection between the fluke and shank that does not require welding.

This connection opens up the possibility for an anchor system which includes different fluke styles optimized for different bottom conditions as well as redundancy through the use of spare shanks to address shank bending should it occur.

Mantus Anchors has provided some SolidWorks analysis which suggests the mechanical connection is very robust in a straight line pull and we are on the verge of producing a prototype for testing to include side loading.

Evans Starzinger has recently acquired a 10 ton load cell and has graciously volunteered to provide testing of our connection.

To get the ball rolling the current design is a simple Bügel style anchor with a fluke shape inspired by a shark's tooth and the expectation is that future developments will include both convex and concave styles as well.

[Delancey]

Evans, where are you located? If possible I would like to stick to one of my objectives of keeping things local. If you are in the Northeast I would be happy to provide the test items directly. If you are elsewhere I would like to try find someone closer to your home.

For testing purposes we can skip the roll bar, galvanizing, and some of the finish work such as sharpening fluke edges. At that point it's a matter of cutting parts and dressing the mating surfaces of the fluke slot and shank, cutting and installing pieces of angle for the locator pin.

A single piece of plate measuring 2' x 4' will yield two shanks and a single shark tooth fluke with enough material left over to make a rectangular bar fluke suitable for clamping to test side loads.

[Delancey]

Originally Posted by JonJo

You could, of course, decide that having a few bent shanks, in 100, or 1,000 is a risk you can take.

Jonathan

Jonathan,

You've probably researched this topic more than anybody. Do you have any idea statistically as to the frequency of occurrence of bent shanks? Maybe that's a "my dumb" for even asking, I don't even know if it's possible to know something like that probably not, but I figure you would be the guy to ask.

I think having a spare shank is a way to address the problem, but what's the point of expending the effort of making something destined to fail if the option exists of making one that won't? I think if there was a way to gauge the likelihood of this happening it would help people make their own choices.

Thanks

[vientoman]

Excellent design work so far. IT all comes down to defining a list of design constraints and trying to work out a balance.

To me, I would place a high value in being able to pass a set of G code around so that a sea of people can help do real world testing. From the response here, I think it would be a shame not to take advantage of the motivated people who would like to produce and begin using the real things. I don't think there is any shame in starting with REV 1 and having willing people help arrive at REV 2 .......etc.

Again, I have a water jet shop that can cut components all day long and I could get a price to have the parts galvanized, strapped and stacked in a small shipping crate for delivery anywhere. Test Anchor in a box......why not. I'll be glad to be ginny pig with my 44ft. cat.

As for trying to anticipate shank bending and scale, I would think that all that means is coming up with a chart of ideal plate thickness for each quantum size category of anchor. That chart could be perfected over time. In other words, "scale A" would be for "x" approximate length and displacement boat catagory and would be best cut from "y" thickness range of plate and so on and on up to 10 ton + boats.

I look forward to the official open source G-code release.

Again, Thank Delancey for your motivation and work.

[JonJo]

Sorry - but there is no data, as you might understand anchor makers do not make the information available. Rocna, at the time, went out of their way to play down the problem as much as possible and owners of anchors with bent shanks were requested to keep quiet. I'm not being critical - I'd have wanted to downplay the whole thing as well if I were an anchor maker!

But

A number of Rocnas made from Q420 steel did bend. I am only aware of a few but how many more (no idea). Size did not matter (though I did not hear of any very small ones, less than 10kg), bending. Some bent as a result of bending when in legitimate use as anchors (they bent on severe wind shifts) one bent as a result of the swivel being directly connected to the anchor some might have bent as a result of over enthusiastic retreival. In terms of numbers - 1:200, but 'worse' if you knock out all the small ones and worse when you consider I do not know the true extent.

Based on a Rocna shank profile, and by and large the proportions to shank plate thickness and shank width stay much the same through the range, my view is that Q420 was inadequate. The original alloy Excel but with an 18mm shank plate thickness (otherwise it is similar in dimension to a 15kg Rocna shank) and made from 5083 alloy is/was not strong enough. The 7075 seems to be much better (and looks to be stronger than the A514 shanked equivalent). Mantus Solidworks analysis of their original shank shows it to be inadequate. I'm not wanting to get into a debate on any of this - its my view and I'm trying to give you some background to make your own decisions.


I have not heard of any 620 shanked Rocnas nor A 514 shanked Rocnas bending. I have not heard of Supreme or Excel shanks bending (both A514). I equally have heard of no Mantus bending.

I have a black and white view of shanks - they should not bend and it is not difficult (nor expensive) to make them basically indestructible.

it is quite common for 316 stainless anchors (I'm not referring to either Spade nor Ultra) to bend. Other anchors bend, or break - but most damage is caused during retrieval (stuck under a rock, bend, or simple old age, break).


I did a survey of anchors in the Med during this Northern hemishpere summer and autumn. I visited about 40 marinas and boatyards. There are a lot of 'locally' made bugel types in the eastern Med, maybe 1:20 was bent

Sorry I cannot be a bit more specific.

I do not think it will be possible to cut the shank and fluke from the same steel plate, or not unless you are, unnecessarily, using a high tensile steel for the fluke.

Jonathan

[Cotemar]

JonJo,

This Open Source Anchor is supposed to be a cheap and easy to make anchor for most anyone on the planet. If they have a bent shank every 6 years, so be it. Just bend it straight and use it for another 6 years or just slide it out and put in a spare.

You’re getting lost in what and Open Source Anchor Project is and is not.
Making a perfect anchor is not what this is about. It’s about making a good cheap anchor that works.

[JonJo]

Hi Cotemar,

I'm not losing track of the focus but I'm not putting my name to anything that might be considered a recommendation or even a comment (by me) and with which I am not comfortable.

Here anchors are a safety item. They are not specified to allow a lunch stop they are specified on the basis they might be needed in an emergency. I do not know the practice in other jurisdictions.

A mild steel shank, to approximate Bugel or Delta dimensions, could bend quite easily. It is not something I could endorse (even for lunch).

As I say - my ideas a re black and white.

But hi tensile steels are readily available and are commonly part of the stock of many precision cutters. I do not see that there is any need to sacrifice strength (or not in terms of the materials used).

Jonathan

[vientoman]

Originally Posted by Cotemar

JonJo,

This Open Source Anchor is supposed to be a cheap and easy to make anchor for most anyone on the planet. If they have a bent shank every 6 years, so be it. Just bend it straight and use it for another 6 years or just slide it out and put in a spare.

You’re getting lost in what and Open Source Anchor Project is and is not.
Making a perfect anchor is not what this is about. It’s about making a good cheap anchor that works.

well said Cotemar . The sooner REV 1 is produced, the sooner data can be gathered.

Again, Reems of data are not required to design and produce a REV 1 anchor. In this case, choose .5 plate for shank, "x" thickness for fluke and cut per REV 1 profile then toss it in the water and begin real world tests.

[Delancey]

Ok, thanks for your patience. OSA1.0 ready for testing. I did some work on the fluke and cut out a mock-up today. I'll post some more photos after I sharpen the edges and make a roll bar.

Gimmie a couple days to work up some dimensioned sheets. I think I can post some 24" x 36" PDF's that people could print out for full sized templates. In the meantime if you want the AutoCAD drawings hit me up with a PM and I will email them to you.

Cheers!

[JonJo]

Delancey,

Looks a nice bit of kit.

maybe I should have been paying more attention

But why did you not design the shank such that it would slot in from underneath, then the 'fin' under the fluke would have provided extra strength to the joint. I am sure you will say that the weld will give it all the strength but if this is designed for amateur construction anything that enhances strength would be advantageous.

Is the design going to be self launching! The whole basis of the 'Delta' shank (and everyone including Spade effectively has copied it, except Wasi and on the Supreme/Boss) was that it is self launching (and in the case of Delta etc, self righting without a roll bar). You have chosen to go the roll bar route so the self righting function of the Delta is not an issue - but have you checked that the centre of gravity will allow the anchor to self launch, including the weight of the chain. Again you will possibly say - its easy to go to the bow and tip the anchor off (with which I agree) - but presumably lots of Delta owners like the self launching aspect.

But the design you have looks interesting - good luck

Jonathan

[Delancey]

There is no welding required.

Those bits of angle iron and the bolts are just a locator pin to stop the shank from backing out but the center of effort of the fluke is forward of the connection so that really shouldn't be an issue.

Because there is no welding, there is no Heat Affected Zone. This means you could have one of these wet jet cut from ceramic armor plating and have the unbendable shank you have longed for.

We have already done FEA that suggests this connection is good out past 40,000lbs in mild steel. The prior art for this connection in anchor design is more than a thousand years old.