Open Source Anchor Project

[Delancey]

Originally Posted by Jimbo485

Stop right there with Mark I. This is great, Delancey!

Mark II can have bends, but Mark I is fine with everything flat. KISS.

I think you guys are right. I was going through the process in my head and realized that there is not much point in wasting time designing flukes if we end up having to change the shank design depending on the shank and shank connection FEA. Heavier shank means lighter fluke and so forth.

To that end I think the most productive move would be to take the Bugel version all the way to a finished draft. Once we have that nailed down we can worry about different fluke styles.

I was looking at my quickie Bugel from before, it's not so bad but it needs a little work. I will refine it to where I think it should be then draw it in AutoCAD and upload .dxf's to the opendesign site that foolishsailor set up.

If we make the Bugel type work we will have accomplished our basic goal. At that point, with a proven shank design, we can make it public and people can start building their own as well as designing their own fluke variations.

Maybe I'll cut one out of MDF on the CNC machine to see how it fits on couple bow rollers first.

[Delancey]

Also, needs bottle opener on the back of the shank. Almost forgot!

[Delancey]

Anchor designing is super fun, making mock-ups is way funner!

It's so great to get out of the computer world and actually make something and to get to load it up and feel how it behaves. It's really weird, it's like it gets snugged down on itself and if you pushed sideways on the tip of the shank it steers the back half of the anchor around like a tiller does a rudder.

I had noticed this when I was messing around with slicing plastic water bottles and bending coat hangers back when I was thinking about steel drums.

If you look at the anchor from the top down and see the long axis as a lever between the tip of the fluke and the back of the fluke and then the tip of the shank, you can see a mechanical advantage that as you rotate around the center of effort of the fluke and forces the tip into the direction of the turn.

Yeah I kinda got it in theory before but it is really fun to get to play with it full size. The lack of weight it actually really helpful to get to understand the significance of the geometry.

Shown here in 1/2" Ultralight MDF sans roll bar and bottle opener. Tomorrow after I remake last years' winter cover and get the boat squared away for some cold weather I'll add the chopsticks, which it needs, and throw it on the bow roller and take some pics.

A quick glance tells me it needs a bigger radius on the top inside of the hook, but that's why we mock stuff up. I did cut two sets of parts, one for keeps and one for breaky, cuz sometimes I like to break stuff.

The ole through-hole-cantilever is really super strong, prolly need to squish the proportions around on my circles but I think I am on the right track. When you load it up it's going to break on the fluke between the shank and the tip and I can guess about where, but hey, it's MDF not metal so where it breaks maybe isn't going to tell you that much. Then again when it breaks outside the connection at least you know that part is good.

+1 on the shark tooth inspiration, it give's you a decent fineness to your point but then backs it up with enough meat to get the job done when compared to the sharper point on the original Bugel.

Think about the square top mainsails you see on newer racing boats. They actually have a higher aspect ratio than a more triangular one of the same height and length. Funner how they are kinda like old gaff rigs in that sense, go figure.

Back to the tooth, it's also worth a mention how at certain angles it looks like the space shuttle. Kinda weird, looks like some other things I can think of too. No, I did not forget the bottle opener, it's just down in the noise right now.

[Jimbo485]

Ok! Put up the design for a 30 kg one and I volunteer to be the first guinea pig / lab rat.

[Parmenter]

Originally Posted by Richard_W

Here is my idea based on compilation of the bits and pieces I've read in this interesting topic. It also might answer the following question ...



... by overlaying two flukes to create double thickness center. The shank slides in from the bottom up, and is locked in place by simple shackle.

Introducing the HOE anchor which is as KISS as I could think of ...



...

like it, not sure why the back corners are cut off.

The advantage I can see for this is its easy enough to get the parts produced and galvanised and then have then flat packed left on board and essentially have a few disposable anchors onboard if required or go oversized for a flat packed monster storm anchor

[Delancey]

Originally Posted by Parmenter

like it, not sure why the back corners are cut off.

The advantage I can see for this is its easy enough to get the parts produced and galvanised and then have then flat packed left on board and essentially have a few disposable anchors onboard if required or go oversized for a flat packed monster storm anchor

Yes, I also appreciate the HOE concept but explain in post #253 how I had decided against it early on and why I ended up with the through-hole-cantilever connection instead.

Anyone who feels strongly otherwise is welcome to develop the concept into a workable design with correct geometry and a properly located CE and prove to me wrong as to why the HOE is a more efficient use of materials.

I also don't know why the back corners are cut off but that's neither here nor there, it also needs scalloped edges and a roll bar as well.

As for the rest, yeah, that's the idea!

[Delancey]

Originally Posted by Jimbo485

Ok! Put up the design for a 30 kg one and I volunteer to be the first guinea pig / lab rat.

We'll get there eventually. I also promise we will have some other fluke styles to offer as well.

In the meantime, the shark tooth doesn't look so bad, right? I think the Bügel tends to get overlooked because it's one of the oldest and seemingly simplest. The Wasi version is so freakin expensive here in the US and cheap knock-offs seem to be so prolific in the Med.

Maybe I am wrong but it sure looks to me like it would work just fine in a lot of conditions.

[Jimbo485]

Delancey, this is all great stuff. It truly is. I want to assist somehow. But not with more theory. It is time for action.

At some point it is time for prototypes. That time is NOW.

It may not be the final designs (in fact, probably won't be) but real, full scale, working prototypes are needed now.

[Richard_W]

Originally Posted by Parmenter

like it, not sure why the back corners are cut off.

The advantage I can see for this is its easy enough to get the parts produced and galvanised and then have then flat packed left on board and essentially have a few disposable anchors onboard if required or go oversized for a flat packed monster storm anchor

No particular reason other than less back edge for the thing to get stack backwards if no roll bar. The full corners and screw on roll bar that can be stored flat could be an option.

It's a concept only. The various fluks, flat, scalloped, etc could be an option as well. I am afraid I cannot afford the time take it beyond this concept.

[Cotemar]

Delancey,

Very nice prototypes. I enjoy that part also. Its a lot of fun to see a 3D model in real life.

Great Job.

[motion30]

Do we know the relationship of the angle of the shank to the fluke?

[Delancey]

Originally Posted by Jimbo485

Delancey, this is all great stuff. It truly is. I want to assist somehow. But not with more theory. It is time for action.

At some point it is time for prototypes. That time is NOW.

It may not be the final designs (in fact, probably won't be) but real, full scale, working prototypes are needed now.

Both Fred The Swan and I agree, the need is urgent. That said, we don't want to muck it up just because we are in a hurry. Besides, we are not about producing crap.

We want to optimize our parts to make them the best they can be and to do that we need to do an FEA. To do that we can use a software like Solidworks which I have access to, I just haven't used it before so have a little learning curve with that.

When I told my wife that Mantus had offered to help us but that I felt we should decline she told me she thought I was stupid. If we can build a quorum of at least a couple people who say we should accept the gracious offer of support that Mantus has made to us, it would certainly fast track things a bit.

Depending on how fast their turnaround was you could be cutting parts next weekend for a very decent quality anchor design. We are very close.

Regarding some details, after installing the sheer pins I am maybe thinking we should consider bringing some angle back into game. This would allow for a single locating pin that would be more effective than the two I have right now.

The CE is marked on the fluke just forward of the shank, there is a corresponding mark on the shank. You can see a bit of the radius cut into the forward end of the slot in the fluke that matches the inside radius of the shank when you look at the bottom view of the fluke.

I still have to throw it on the bow roller but it's gusting to 45kts today and colder than crap so that will have to wait for another day. Let us know what you think about accepting help form Mantus. Works for me. Props on them for offering in the first place. Very cool thing to do.

[Delancey]

Originally Posted by motion30

Do we know the relationship of the angle of the shank to the fluke?

Sure, look at the side view from Peter Bruce's Patent. There's a lot going on there but what you want to first look at is a line that extends up from Point C to Point 5.

This line goes from the Center of Effort out into infinity (your boat pulling on the rode) and the angle between it and P (the fluke plane). You can attach your rode to the an anchor at any point along this line. From what I have seen this angle is anywhere from 32.5 to 33.3 to 36 degrees depending on who made the anchors so, you want to be somewhere around that neighborhood.

The next thing you want to look at is the angle B which is line S down from Point 5 down to P. This angle tends to vary more in different designs and is a function of the aspect ratio of the fluke. This angle is key in determining the angle of attack for the fluke tip as it penetrates.

If you look at the plan view you can see the Center of Effort marked as C. This is the balance point of the surface area of the fluke.

[Delancey]

Just as a little primer on Solidworks. 25 minutes, good part is at the end.

E1 SolidWorks Simulation Express FEA.mov - YouTube

[Delancey]

Tweaked it a bit. Should fit on a bow roller just fine, won't guarantee it won't bash your roller furling drum on it's way down. Dimensions provided in inches.