Open Source Anchor Project

[Shas Cho]

Thanks, brother.
I will definitely send them a note of thanks.
Portraying myself as a representative of this forum, though,
might be stretching reality to the breaking point.

Altruism is our only hope of continuing to sail
in a sea with communities of life in it.
To be human is to act altruistically.
I am filled with admiration for your OSA project,
for your investment in it,
and for the motives you elucidated for initiating it.

Respect.

- Shas

[Delancey]

Originally Posted by Shas Cho

Thanks, brother.
I will definitely send them a note of thanks.
Portraying myself as a representative of this forum, though,
might be stretching reality to the breaking point.

Altruism is our only hope of continuing to sail
in a sea with communities of life in it.
To be human is to act altruistically.
I am filled with admiration for your OSA project,
for your investment in it,
and for the motives you elucidated for initiating it.

Respect.

- Shas

Maybe trying to save the world one anchor at a time is as ridiculous a notion as tilting at windmills.

Maybe putting a bottle opener on an anchor is irresponsible because it will encourage people to litter their bottlecaps in the water. Maybe it's better to put them in the water and let them sink into the sludge rather than wasting petroleum to chauffeur those bottlecaps to a landfill somewhere.

I don't know.

One thing I do know is that studies of lifeboat survivors show that oftentimes the biggest threat to our survival is out own apathy. Our own unwillingness I do something to save ourselves.

An anchor is a tool for self-arrest.

Maybe by making ourselves a tool we can use to save ourselves with, we can save ourselves, even if only in a small way.

I don't know but I am willing to try.

[estarzinger]

loading question. . . . What if the fluke is not loaded evenly . . . What if it is loaded only on one side . . . As in lying on its side and bottom half of fluke hooked on a rock? How is the fluke to shank joint going to fare in that situation?

[jjt]

It's not clear to me, how the fluke/shank joint will retain the pieces together while the anchor is going down and the fluke first hits the water

[Delancey]

Originally Posted by estarzinger

loading question. . . . What if the fluke is not loaded evenly . . . What if it is loaded only on one side . . . As in lying on its side and bottom half of fluke hooked on a rock? How is the fluke to shank joint going to fare in that situation?

With a zero clearance through-tenon, it will bend just outside the joint if overloaded. With a joint with some play in it, it will still bend just outside of the joint if overloaded. The zero clearance joint I have in the MDF mock-up is actually quite stiff.

I didn't want to be that guy who had to fall back on everybody's bitch to make a connection work but in the end I think adding angle is the best, most practical solution. Perhaps most importantly, it allows you to mess up the slot in the fluke if you suck or have few skills and no experience with making something like this.

Zero clearance requires precision some may lack, but with angle on either side of the fluke and slightly oversized holes bolting the angle to the fluke, you can be as sloppy as you want when you cut the slot in the fluke.

You will see in the latest drawing of the shank how there is a 3/16" hole just to the right of the bottle opener. This is a locating hole that would receive a shear pin through the angle to stop the shank from backing out of the fluke.

[Delancey]

I have to make this quick and hit the road for turkey. Here is the first two simulations so far for the shank from Mantus. The first one I posted earlier is the dreaded side load. Shows our mild steel shank is good out to at least 300lbs. of side load.

Why is this important and what do I care? I will leave that for others to debate knowing that for OSA owners it is an issue obviated by the fact that we probably can afford to have several spare shanks with all the money we saved by not buying crap from China which will keep us safe until we have a chance to straighten the bent shank out.

We set the baseline low which means Jonjo can make it out of whatever he wants and still bend it when the time comes. There is and will never be an un-bendable anchor. Get over it.

The second one is a straight line pull of 40,000lbs. where you are only beginning to see red at the shackle attachment point, the rest is blue. What this tells you is that 99.9% of the time all that extra strength from up-spec'ing the steel is a waste, and that mild steel is plenty well suited for making good anchors.

Waste away you wasters! In the meantime we have a weight surplus of about 3 lbs. based on our current design so we can put that back into the fluke but not today.

I am out for turkey. Cheers

[Delancey]

I am a human and a sometimes I do dumb things. One of the dumb things I did recently was to get involved in a different anchor thread. This was dumb because it was counter-productive to our objective of producing and distributing a free anchor design. If I do a dumb thing again, lease point this out to me. I am here to learn and contribute, I am not here to act like a jerk or be a dick.

That said, back to anchors. Now that we sketched out the part and have done some simulations we can optimize.

What you see in the two different simulations is that in general the shank is very robust, maybe too robust, for the straight line pull. We could prolly trim a considerable amount of material off of the shank and still be good for the straight line pull which would give us more weight to put in the fluke for more surface area.

However, what you also see in the simulations is that we are only good out to about 300 lbs for the side load, which we all know is the worst case load for our anchor. Trimming down the shank won't help this any.

What you all have to tell me is are you okay with this? Does that work for you to assume you have a spare shank or two and that if you ever did bend the shank you would be happy to swap it out and go about your merry way?

We could make the shank more able to resist the side load if we made it thicker, but to be efficient with our materials we might want to make it out of the same stock as the fluke. Currently for our 20kg/44lbs Bugel-style we are expecting to use 1/2" material for the fluke becasue that looks like about what the Wasi version of the same anchor uses.

If we are okay with leaving it the way it is we can go ahead and cut the part and a mock-fluke, which approximates the thickness and width of the proposed shark tooth at the one third point, and start bending. We need to proof test the shank and fluke connection before anybody starts making any actual anchors.

Once we do that we can put the digital files on the opendesign site Foolishsailor set up and it's game on to start designing and making flukes. One thing I will add is that at some point we need to decide if we want to add the extra 1/4" to the blade thickness I took away so that our shank can accommodate more the 1/2" we currently have in the design.

I think so, this would let us stack a wide 1/4" fluke onto a 1/2" bar that runs from the shank to the tip provide both the area and the stiffness we need and where we need it. the only downside I can see is if you only end up ever making a 1/2" thick fluke, you will still need to have a 1/4" shim in there to make up the difference.

Down the road we will know better, I just would hate to see an early adopter get shorted because we don't know this now.

[foolishsailor]

Excellent.

[monstads]

Not to derail the current design specs, but I would also be very interested in how well the design scales (in particularly down).

I assume that if you want to make one half the weight, you wouldn't just want to half every measurement, including shank thickness?

[Shas Cho]

Originally Posted by Delancey

What you all have to tell me is are you okay with this? Does that work for you to assume you have a spare shank or two and that if you ever did bend the shank you would be happy to swap it out and go about your merry way?

I'd like to see this most excellent project
proceed on its present course.
After the prototype has been tested
it may be seen that tweaking is required.
Let's not make "what if ...?" changes
before we know what we have.

Carry on, brother!
You are doing a fine thing,
and doing it very well!

- Shas

[Delancey]

Originally Posted by monstads

Not to derail the current design specs, but I would also be very interested in how well the design scales (in particularly down).

I assume that if you want to make one half the weight, you wouldn't just want to half every measurement, including shank thickness?

It is actually good that you mention this now, as it is an issue we will need to address with the current design for our 20kg/44lbs anchor.

Area is squared, volume is cubed. If I have a 12" x 12" x 12" cube I have a volume of 1,728 cubic inches. If I scale it down 50% so that I have a cube that measures 6" x 6" x 6" I end up with a volume of 216 cubic inches.

1,728 cubic inches of mild steel weighs 489.54 lbs whereas 216 cubic inches weighs 61.19 lbs which is 1/8 of the cubic foot so scaling down to match an arbitrary weight isn't so easy.

Let's say I have a 1/2" plate that measures 12" x 12" and weighs 20.4 lbs. If I want to scale down to a plate that is less thick but weighs about the same I end up with a 3/8" plate that measures 10" x 10" and weighs 10.62.

I think you can see this at play with some of the larger Ronco anchors where different weight anchors are all fabricated out of the same thickness plate. Not sure if I have that totally correct but I think I read it on a thread somewhere.

Basically weights assigned to anchors are sort of arbitrary but the materials we have to work with are not, so you do the best you can given your structural requirements. I would be interested to see how closely different sized anchors actually match their stated weights. Anybody ever actually weigh their anchor? There are lots of boats called an X-brand 40 that are really only 39' 6" or whatever.

The reason I say this is an issue we will have to address is because of different material standards, Metric and Imperial. Think about the Russian copy of a US B-29 bomber, it flew just fine but was a bit heavier.

I mentioned earlier how the Bugel fluke on a Wasi anchor is about half inch so we should be good to go if we use that size for our version and prove it through testing. In fact that Wasi fluke is probably made out of 12mm plate.

I live in the States and I design using Imperial Measurements but the OSA isn't for me, it's for anybody anywhere which means we need to address the Imperial/Metric conversion. Specifically I am designing for 1/2" thick plate which equals about 12.7mm.

Uh oh, that's about 5% thicker than 12mm plate. This means that if someone takes our design, doesn't change the square area of any of the parts but makes them out of 12mm plate they are going to end up with an anchor that weighs 5% less so their 20kg anchor and is really only going to weigh 19kg.

Is this a big deal? I don't know you tell me. Since the shank is so overbuilt for the straight line pull, I don't think 5% less strength is going to matter. The side load the simulation for 12mm is going to look how it does now for 1/2" at 285lbs instead of 300lbs. Since it is not possible to produce an un-bendable shank and we plan on having a spare anyway I think it is a moot point.

To save the headache of producing different designs for different material standards I think it best to accept that one design will produce slightly different results and that is okay as long as they still meet the minimum strength criterea. To save headaches for the builder, wherever he/she may be, we will provide plans with dimensions in both Imperial and Metric measurements.

For the sake of getting the biggest bang for the buck I originally suggested we start with a 20kg/44lbs design because it seems like an appropriate size for a working anchor for a generic 40' 20,000 cruising boat, and would serve as a BIB for smaller boats.

Using this as starting point, as we scale up and down I think it would be best to scale cubicly, to maintain the proven shape and proportion, based on commonly available Imperial/Metric sizes, where the finished weight is whatever weird not-round number we end up with. Trying to produce a separate design that weighs exactly 15kg or 25kg or whatever seems like a waste of effort with no real benefit.

For those of you who work with metric stock but think you're getting shorted, don't be so quick, 10mm is thicker than 3/8" so it can go both ways. We just need to design for the thinner material.

[Delancey]

Originally Posted by Shas Cho

I'd like to see this most excellent project
proceed on its present course.
After the prototype has been tested
it may be seen that tweaking is required.
Let's not make "what if ...?" changes
before we know what we have.

Carry on, brother!
You are doing a fine thing,
and doing it very well!

- Shas

Works for me. I also think maybe we should start with just 1/2" thickness for the fluke and skip the 1/4" shim for now, KISS. I hope any early adopter would be happy to have a very inexpensive but totally functional Bugel-style anchor. Should have plenty of money left over to make future versions.

As far as the spare shank goes, getting these funny shapes out of a rectangle means you are going to end up with a fair amount of drop (waste) material if you are making a one-off which will be more than enough for an extra shank or two.

In fact, when it comes to dressing edges it will be easier for the inexperienced to get better results by working with two parts instead of one. You can clamp the two pieces together and start grinding. If you start to go off-square with you edges you can just switch the parts around so the opposite faces are matched up and start working back to square.

As far as a next step, I want to make another mock-up using the current shank design to try it on my bow roller again. The first one fit about as well or better than my rusty CQR and I think in general the Bugel style should work for most. That said I increased the clearance on the current design because it seemed like the first one could fit better. We shall see.

After that, we need to decide who is going to make and test our prototype. Since I obviously have a dog in the fight, I suggest it not be me. Mantus has offered kindly, they also have a dog in the fight so to speak, but mainly I don't want to be a burden to them any more than we have to.

I am willing to put my money where my mouth is and front some cash, just don't tell my wife, we are trying to save for our cruising kitty. Maine Sail comes to mind as a pretty well regarded individual. Also, sounds like there are a couple folks down in Oz who are anxious to get building.

Any thoughts?

[NahanniV]

What about self launching ? Has that been taken into account ?

I thought the angle in the Rocna shank and the round in the Manson shank was to promote self launching.

I find it a pain to have to push the anchor overboard. My windless is too far aft to operate and push the anchor at the same time.

Perhaps I missed that discussion ?

Cheers,
JM.

[Delancey]

Originally Posted by NahanniV

What about self launching ? Has that been taken into account ?

I thought the angle in the Rocna shank and the round in the Manson shank was to promote self launching.

I find it a pain to have to push the anchor overboard. My windless is too far aft to operate and push the anchor at the same time.

Perhaps I missed that discussion ?

Cheers,
JM.

Well, I did bring the subject up earlier. Shortest distance between two points is a straight line, if you make a crooked (self launching shank) you need to add more meat to resist straightening out which means less fluke area so the Bugel style is more efficient in that sense. Also the Bugel style shape will nest better out of a sheet of stock than the crooked shank so their is more efficiency in production through less waste.

Nobody responded, so a Bugel style is what we ended up with.

I am down for whatever but need the feedback to guide my hands if you guys are going to get what you want out of this project. Personally, the Bugel style fit my roller as good or better than my rusty CQR, for what that's worth.

My roller drum is so low that I will probably have a problem with any style, which is a me-problem and should not influence the design. I'm planning on replacing my thirty year old standing rigging next summer and can maybe solve my own problem down the road.

Crooked or straight doesn't matter to our shank/fluke connection. I think a nice thing we have going for us is that we have options. As Shas Cho mentioned however, too many options and what if's can be a distraction. Maybe be best to start out basic with the Bugel style and add a crooked shank into the mix later?

These things said, the nice thing about design is that you can always change your mind.....

[Delancey]

Originally Posted by Delancey

Let's say I have a 1/2" plate that measures 12" x 12" and weighs 20.4 lbs. If I want to scale down to a plate that is less thick but weighs about the same I end up with a 3/8" plate that measures 10" x 10" and weighs 10.62.

Meant to say "weighs about half"