DIY- make your own anchor

[30boat]

I've made a Bugel and a Rocna copy.I used mild steel and made the shanks with an I beam section so they wont bend or weigh too much.The Rocna copy especially holds fantastically and as I made it oversized for my 32ft boat I don't think I'll ever test its limits.The Bugel is massive and holds very well indeed too.

 

[noelex]

How about just using whatever material you fancy and stressing it based on the yield strength of the chain?

The shank creates a lever arm, so the shank can be bent even if it considerably stronger than the chain.

There is some concern a bent anchor will break out, due to the poor geometry, although I suspect this happens rarely to a well set anchor (which it needs to be to bend in the first place). At best it cannot be used again until replaced, or repaired.

 

[John the kiwi]

Of course you can make your own anchor. The three obvious elements are the Design, the Material and the Fabrication. As you are a Mechanical Engineer you should be able to manage each of these elements separately and then integrate them to produce the final product.

Hi all. Thanks for all the inputs. Engineers do tend to specialise. Having done so one realizes how ignorant one is about areas outside ones own specialty. The downside of being an engineer is realizing just how dangerous that ignorance can be and how cautiously one should tread......

(If you want to know why engineers are conservative, consider this: If an engineer gets it right he may, if he is really lucky get an award that consists of a plastic desk ornament. If, on the other hand he gets it wrong, he can look forward to days in court and jail time and bankruptcy.
Anyway lots of interesting information and some avenues to explore that i wasn't aware of plus a bit of humour, so thanks again to all who have contributed.
Cheers

 

[Neeves]

Much might depend on the cost of the anchor, the value of the yacht, the value you place on the crew and exactly what role the anchor is to play but given the history of poorly made anchors, by even companies that ought to know better, I'm sceptical of the concept of a home made anchor. Ignoring any financial costs - but an idea must be to ensure ones crew (and any third parties involved - other yachts) are as safe as possible. A decent anchor is not that expensive.

Jonathan

I sent this prior to reading John the Kiwi's post above.

 

[John the kiwi]

Much might depend on the cost of the anchor, the value of the yacht, the value you place on the crew and exactly what role the anchor is to play but given the history of poorly made anchors, by even companies that ought to know better, I'm sceptical of the concept of a home made anchor. Ignoring any financial costs - but an idea must be to ensure ones crew (and any third parties involved - other yachts) are as safe as possible. A decent anchor is not that expensive.

In general i would agree with your sentiments as expressed, but 3 things made me start this thread:
1. Poor performance of what you might classify as a "decent anchor"
2. Apparent poor quality of some new modern pattern anchors that i looked at. Sure Hot Dip can make things look rough, but on the other hand visually poor welds and poor edge finishing cant be disguised either, and that was on what was meant to best quality anchors.
3. The belief that i could build an anchor that could out perform my professionally built one at a fraction of the cost of a new modern pattern anchor.

The nice thing is that i can easily test my(hypothetical self built) anchor against the professional one in my conditions.
So is the existing anchor the recommended size for my boat? Yes it is. also has 8 metres of chain and 10 mm nylon rode.
Can i drag my CQR by motoring in reverse? Yes i can.
Does it breakout and not reset with a 180 degree change in load? Yes it does!
If my (hypothetical at this stage )anchor doesn't compare favourably then i wouldn't risk my self/crew/boat by using it.
OTH if it performs better than a professionally built anchor, how am i worse off?
Cheers

 

[Avocet]

The shank creates a lever arm, so the shank can be bent even if it considerably stronger than the chain.

There is some concern a bent anchor will break out, due to the poor geometry, although I suspect this happens rarely to a well set anchor (which it needs to be to bend in the first place). At best it cannot be used again until replaced, or repaired.

Understood, but I wasn't thinking about just a failure in pure tension along the axis of the shank. As a home-made one-off it might be sensible to design it such that no force that could ever be applied by the chain, in any direction, will damage the anchor. Yes, it'll end up being a bit heavier than it otherwise might, but would that be such a bad thing on an anchor?

 

[Neeves]

John the Kiwi, If I read as being sanctimonious that might have been my fault. I'd actually love to see someone build a better anchor (and I could not care who does it!). Currently all anchors are a compromise, one of those compromises is cost, but if anyone can build something that reduces those compromises then the world will beat a path to that door. In the light of your posts you seem to have some ideas of the implications - and if you are will to try the ride, go for it. But I'd also still go to your boat show, you might get some ideas! My guess is you should see, possibly excluding the Spade, nearly all the current 'good' anchors and there should be a decent cross section of ideas on display.

But if your baseline is the CQR you need to raise your standards

Jonathan

 

[Neeves]

Understood, but I wasn't thinking about just a failure in pure tension along the axis of the shank. As a home-made one-off it might be sensible to design it such that no force that could ever be applied by the chain, in any direction, will damage the anchor. Yes, it'll end up being a bit heavier than it otherwise might, but would that be such a bad thing on an anchor?

You want the weight, (preferably as surface area) in the fluke, not the shank. If you beef up the shank it will be 'top heavy' (needing a bigger fluke) which is why everyone went to ASTM 514 (or Bisplate 80) - so not beefed up, stronger steel. If the fluke is efficient then the risk is that if you snatch load at 90 degrees to the length of the shank (and the shank is not strong enough) then the fluke will be immovable and the shank bend. If you use thicker plate - it retards the ability of the fluke to dive (it needs to pull a thicker lump of steel down through the seabed) - so thicker steel plate would be stronger, but the fluke will not set so well (which is why everyone went to Bisplate 80 in the shank).

On the basis you want surface area you do not want a lead toe, so to self right you need a roll bar, a roll bar has surface area that detracts from the surface area of the fluke - its yet another lose, lose (and the roll bar does not fit on some bow rollers). The Boss and Bruce are almost the only exceptions to the lead in the toe/roll bar compromise.

John the Kiwi you have your work cut out

Jonathan

 

[noelex]

Yes, it'll end up being a bit heavier than it otherwise might, but would that be such a bad thing on an anchor?

It depends where the weight is added. For most modern designs extra weight in the shank will decrease the performance.
Extra weight in the toe, is less critical and can be beneficial ( but the toe also needs to kept as thin /sharp as possible)

There are plenty of reasonable anchors constructed of mild steel, but you cannot simply add weight without considering its impact on the anchors COG and also if the thicker material will reduce penetration. (Such as an I beam shank).

 

[John the kiwi]

John the Kiwi, If I read as being sanctimonious that might have been my fault.

No i didnt take it as sanctimonious. You are exactly right in that as skipper i have a responsibility to myself and boat and crew to use gear that is appropriate and fit for purpose and safe. If i make and use something that endangers self/crew/boat then i am rightly culpable. Hence my softly softly approach.
Ironically, i am in working in the West island(sometimes known as Australia) for the duration of the Hutchwilco show so wont get to see it.
Regards

 

[Avocet]

Ok, that's more to think about than I had bargained for! But the OP's boat is a 26 footer. While I appreciate that proportionally, all the same arguments apply to a smaller anchor as to a big one, I wouldn't have thought it was beyond the wit of man to come up with a shank that the sort of chain / warp carried by a 26 footer couldn't damage and still have the CoG in the right place?

 

[NormanS]

Much might depend on the cost of the anchor, the value of the yacht, the value you place on the crew and exactly what role the anchor is to play but given the history of poorly made anchors, by even companies that ought to know better, I'm sceptical of the concept of a home made anchor. Ignoring any financial costs - but an idea must be to ensure ones crew (and any third parties involved - other yachts) are as safe as possible. A decent anchor is not that expensive.

Jonathan

I sent this prior to reading John the Kiwi's post above.

Frankly, I find that a pathetic attitude. What do you think about home built yachts?

 

[30boat]

Frankly, I find that a pathetic attitude. What do you think about home built yachts?

I've installed my own rig.Does that make my boat unsafe?

 

[fishermantwo]

You want the weight, (preferably as surface area) in the fluke, not the shank. If you beef up the shank it will be 'top heavy' (needing a bigger fluke) which is why everyone went to ASTM 514 (or Bisplate 80) - so not beefed up, stronger steel. If the fluke is efficient then the risk is that if you snatch load at 90 degrees to the length of the shank (and the shank is not strong enough) then the fluke will be immovable and the shank bend. If you use thicker plate - it retards the ability of the fluke to dive (it needs to pull a thicker lump of steel down through the seabed) - so thicker steel plate would be stronger, but the fluke will not set so well (which is why everyone went to Bisplate 80 in the shank).


On the basis you want surface area you do not want a lead toe, so to self right you need a roll bar, a roll bar has surface area that detracts from the surface area of the fluke - its yet another lose, lose (and the roll bar does not fit on some bow rollers). The Boss and Bruce are almost the only exceptions to the lead in the toe/roll bar compromise.

John the Kiwi you have your work cut out

Jonathan

You seem to have missed the point entirely. This bloke wants an anchor for a 26 foot trailer sailer. He is going to hand craft this anchor so he is able to correct those limitations of those expensive but well designed anchors. Roll bar anchors are not going to fit in a trailer sailers anchor locker. The choice is probably down to a look alike Ultra or spade. Both hollow shank and handcrafted in SS with a really sharp leading edge will be overkill.
Make a small version as a trial run. I have spade about half a kilo in SS I use with my yacht tender for fishing etc. Search out the Youtube videos of the model modern anchors operating in a sandpit at some boat show someplace.
When I was a fisherman I used SS anchors I built myself, first was a Bruce then a Delta. There was never any indication of failure, bent shafts etc and the surveyors were always impressed.
Remember the makers of these expensive anchors started off as amateur constructors!

 

[Neeves]

Home built yachts are surprisingly common here, there is a complete industry established to support the building of catamarans at home up at least 50'. About 5 years ago one of the deck hardware companies estimated there were 550 in build. To have it insured would need the services of a surveyor. To enter a marina in Australia you need 3rd party insurance,I think to the value of $5 million. To me the test is 'would I allow my 10 year old grandchild on a vessel for a one week cruise (in say the Western Isles). Most people building boats do so from plans. A mast is slightly different in that it involves little owner input, stay and turnbuckles are well defined as to strength etc. People building from masts commonly have the old mast to refer to. Building an anchor, from scratch, is slightly different the manufacturer needs to know the possible loads placed on the anchor and buy steel to meet those loads, he then needs to be a competent welder (for example Manson's welders are Lloyds approved, Anchor Right proof test their models, Deltas are made with Lloyds approved welders, when Rocna obtain full RINA certification they will need RINA approved welders etc. Possibly you know what loads are likely to be placed on an anchor shank and can advise John?

A runabout here ended up on a beach, there was some damage. The insurance surveyor assessed that the anchor was inadequate. The insurance company refused to pay up, in this case the insurance company passed the responsibility to the chandler that had sold the anchor.

My attitude might be pathetic, but its a pathetic real world.

Jonathan

 

[30boat]

When I built my anchors I just overbuilt them,simple.They're a little heavy and they're too big for my size of boat.I don't care.I know they are safe and I'm still more than strong enough to haul them up.

 

[Neeves]

Pathetic?

A Buizen, a rather desirable yacht in Australia, had its rigging replaced recently. Completed by a professional, new stays, new turnbuckles but done with the rig left standing, so bit by bit. The rig went over the side recently, insurance company has refused to pay as the mast was not completely removed (maybe a tang failed). It might be pathetic but its real life. maybe coming to an insurance company near you?

Jonathan

 

[NormanS]

Pathetic?

A Buizen, a rather desirable yacht in Australia, had its rigging replaced recently. Completed by a professional, new stays, new turnbuckles but done with the rig left standing, so bit by bit. The rig went over the side recently, insurance company has refused to pay as the mast was not completely removed (maybe a tang failed). It might be pathetic but its real life. maybe coming to an insurance company near you?

Jonathan

And your point is? What has that to do with a competent person making their own anchor?

 

[30boat]

I should point out that the op is a mechanical engineer with welding training.He should be more than capable of putting together a decent ,safe anchor.

 

[oldbilbo]

In the words of the notorious Blue Peter presenter - "Here's one I made earlier...."

Er, I seem to have some difficulty with scale factors.... After reading the Wikipedia entry, I'm still confussed....