Bow roller Delta vs Rocna

[lustyd]

Hi all does anyone know how a Rocna compares to Delta in terms of how they sit on the bow roller? I'm considering a Rocna to replace the Delta on the bow for various reasons (none performance related, perfectly happy there). Short of making cardboard cutouts I can't think how to work this out without buying and trying.

This question is 100% about fit in the bow roller.

 

[AMOREST]

It all depends on the diameter of the roller and the diameter of the shank which is in contact.
ROCNA have an optimum Roller size which provides good vertical retention if the shank remains pulled in to the roller.
Link enclosed
Bow roller assembly design (Rocna Knowledge Base)

I made new roller Diameter of groove 90mm to suit shank of 15Kg ROCNA.

 

[Bouba]

Hi all does anyone know how a Rocna compares to Delta in terms of how they sit on the bow roller? I'm considering a Rocna to replace the Delta on the bow for various reasons (none performance related, perfectly happy there). Short of making cardboard cutouts I can't think how to work this out without buying and trying.

This question is 100% about fit in the bow roller.

The cardboard cutout is exactly how I did it. I downloaded the A4 paper templates, stuck them together to make the full size anchor then stuck it on cardboard. I then put it on my Delta bowroller and it fit perfectly. It’s a little close to the gelcoat of the bow when it comes out the water (and the tip of a Rocna is sharp) but I now lift the anchor slowly when it comes out the water

 

[lustyd]

thanks, that link suggests they are more similar than I thought and shows them overlaid which is comforting!

 

[AMOREST]

Yes the overlay shows the ROCNA has a smaller angle of shank on the roller which acts as a bit of a hook which gives the vertical retention when the shank remains tight.

I attach a pic of my roller / ROCNA / Retaining strop which works well. MOODY 336.
No forestay in the pic but offset groove keeps shank away from Pin.

 

[RJJ]

We recently changed from Delta 20 to Rocna 25 following the same line of enquiry via our class FB pages. All ok.

The Rocna actually has a slightly narrower shank which is more prone to wobbling laterally in our particular bow assembly. This is disconcerting not dangerous and easily dealt with by a webbing lanyard secured tight around the shank while under way.

 

[Neeves]

The Delta shank is a brilliant and simple piece of design - but it was designed, specifically, for a Delta. If you lay a Delta on a beach (or your floor) any way you can conceivably imagine and apply a small amount of tension at the shackle end (ie by the rode) then the anchor will roll and engage the seabed. I'm not aware that the Delta design influenced Spade, or vice versa, but if you take a Delta shank and align a Frech curve to the corners - you get a Spade shank (or vice versa). I know this as I compared a 15kg Spade, Excel, Delta and a couple of others (which I forget).

Let's say by serendipity the two designers, Delta/Spade came to the same conclusion (and everyone else copied).

If you look at most anchors since then they have copied, with minor changes, the concept.

Its the outer edge that is critical - cutting the shank to retain strength and allow self deploying (courtesy of Sir Isaac) is not a big deal - and again copied by most anchor makers.

Exceptions are Bruce, which pre-dates Delta and then, in no order, Supreme, Kobra and .....CQR (not forgetting Danforth).

The design of the shank was predicated by the concentration of ballast in the toe of the Delta. Rocna got this wrong as their ballast is not focussed in the toe - and this has led to the need for a roll bar - the roll bar accommodates the poor concentration of the ballast. But the addition of the roll bar did not impact the design of the shank - and Rocna and Excel etc all use the 'Delta' shank design. I have not checked but possibly also Ultra, Vulcan and........

Others have copied as the internal profile of the shank allows self launching, Gravity and the shank/fluke interface allows the fluke to drop and it 'self deploys'.

Most bow rollers - accepting the commonality of design, and the simple fact Delta is cheap, accepted and Classification Society certificated (and copied) - are produced to accept a Delta.

People don't produce bow rollers to accept a Fortress, Danforth but bow rollers on the common European vessels all accept Delta.

Basically - most bow rollers accept a Rocna, its usually whether your bow furniture, bowsprit. furler accept the roll bar and importantly was the bow roller designed for a smaller Delta than your choice of Rocna (or other anchor).

The answer is as suggested - draw the anchor you desire (of the right size), cut it out and try it - simple stuff.


Though, almost, every anchor maker has copied the Delta shank - the designing team has been forgotten and remains un-acknowledged.

Jonathan

 

[NormanS]

We recently changed from Delta 20 to Rocna 25 following the same line of enquiry via our class FB pages. All ok.

The Rocna actually has a slightly narrower shank which is more prone to wobbling laterally in our particular bow assembly. This is disconcerting not dangerous and easily dealt with by a webbing lanyard secured tight around the shank while under way.

I find it fascinating that many people change from an older type of anchor to a HEAVIER anchor of a more currently fashionable type. I wonder why they do this? ?

 

[Tranona]

I find it fascinating that many people change from an older type of anchor to a HEAVIER anchor of a more currently fashionable type. I wonder why they do this? ?

My thoughts exactly, but I guess the "heavier the better" school of thought is well entrenched, despite the copious evidence to the contrary. Given the significant holding power of a Rocna over a Delta (if all the tests are to believed why go up in weight?

 

[Boathook]

The cardboard cutout is exactly how I did it. I downloaded the A4 paper templates, stuck them together to make the full size anchor then stuck it on cardboard. I then put it on my Delta bowroller and it fit perfectly. It’s a little close to the gelcoat of the bow when it comes out the water (and the tip of a Rocna is sharp) but I now lift the anchor slowly when it comes out the water

I used the paper template on cardboard as well. Printing was easy each sheet of A4 paper having alignment marks.

 

[Pye_End]

I find it fascinating that many people change from an older type of anchor to a HEAVIER anchor of a more currently fashionable type. I wonder why they do this? ?

Many people change to a heavier anchor full stop.

However, if you do want a larger anchor and not confined to the traditional anchor of your choice, you may well take the opportunity to go with the most recent designs. Nothing odd or strange about this behaviour if you believe 'bigger is better'.

I changed the original CQR to a larger CQR (before new gen were available), and then changed to a slightly smaller new gen (but still bigger than original).

 

[Neeves]

One problem with buying a bigger anchor than was originally supplied is that the location of the windlass was specifically for say a 20kg model 'X'. Yachts today are designed around maximising accomodation not at necessarily considering windlass/bow roller spacing. if you then 'upgrade' (I use the word with caution) with a heavier, more modern, anchor you may then find that there is not enough room, sensibly, or any room at all for the longer shank, between fluke against bow roller and shackle/swivel at the gypsy. This is all compounded with the other inexplicable fashion statement - inclusion of a swivel (which gets even worse if you include a few links between swivel and shank).

If the anchor cannot be housed with the fluke against the bow roller (or cheeks of the bow roller) then the anchor will wobble at sea - grinding the bow roller

Jonathan

 

[Bouba]

One problem with buying a bigger anchor than was originally supplied is that the location of the windlass was specifically for say a 20kg model 'X'. Yachts today are designed around maximising accomodation not at necessarily considering windlass/bow roller spacing. if you then 'upgrade' (I use the word with caution) with a heavier, more modern, anchor you may then find that there is not enough room, sensibly, or any room at all for the longer shank, between fluke against bow roller and shackle/swivel at the gypsy. This is all compounded with the other inexplicable fashion statement - inclusion of a swivel (which gets even worse if you include a few links between swivel and shank).

If the anchor cannot be housed with the fluke against the bow roller (or cheeks of the bow roller) then the anchor will wobble at sea - grinding the bow roller

Jonathan

Yes, true which is why the template is so important. And Rocna don’t recommend a swivel, another reason to get a Rocna !

 

[doug748]

It's always useful to know the boat, it's size and the location. However, Force 4 were happy for me to take a new anchor and try it against a later exchange, in fact I think I had a refund.

I have a Rocna, tho I think I like the Manson Supreme better, it might be worth looking at.

.

 

[Hoolie]

Yes, true which is why the template is so important. And Rocna don’t recommend a swivel, another reason to get a Rocna !

We have a 20kg Delta and 10mm chain, but have never needed or wanted a swivel.

 

[Bouba]

We have a 20kg Delta and 10mm chain, but have never needed or wanted a swivel.

I had a Delta with a swivel. It didn’t make any difference, it still can’t hold
A Delta is not an anchor, it’s a plough. If a plough can’t stop a horse how can it stop a boat ?

 

[Boathook]

Many people change to a heavier anchor full stop.

My Rocna is about the same weight as the Danforth I had. The Rocna is sized according to the Rocna selection 'graph'. As usual my boat was on the top range of one size and bottom of the next size and seeing that I like anchoring I went for the bigger one. My boat does seem to dig the anchor in well seeing the mud on it upon retrieval.

 

[Bouba]

My Rocna is about the same weight as the Danforth I had. The Rocna is sized according to the Rocna selection 'graph'. As usual my boat was on the top range of one size and bottom of the next size and seeing that I like anchoring I went for the bigger one. My boat does seem to dig the anchor in well seeing the mud on it upon retrieval.

I agree, I take the mud on the anchor during retrieval as a good sign. But the anchor testers on YouTube consider it a bad thing

 

[Neeves]

I agree, I take the mud on the anchor during retrieval as a good sign. But the anchor testers on YouTube consider it a bad thing

Its very simple - and you can try it yourself.

Take your anchor and set it as normal, power set and see how happy you are.

Retreive the anchor, have a look at the mud compacted into the fluke - that's (apparently) your measure of success. Without touching the mud reset your anchor and compare how far you need to drag your clogged anchor before it resets - if it resets at all. If it was well clogged - it will not reset.

Your anchor was designed to set with a clean fluke, not a fluke filled with mud. Tests show that the anchor will not reset properly and quickly until the mud is washed out. Anchor Resetting Tests - Practical Sailor. Imagine a change of tide or wind and your well set anchor somersaults - its now full of mud - your yacht starts to move with the change of tide and wind, accelerating as it goes - the anchor will reset as during the time it is bouncing across the seabed it 'self cleans' - just hope the shore, other yachts are far enough away.

The likelihood of your anchoring in cloying mud, there being a change of tide or wind and your anchor somersaulting is not high - but it happens.

Your measure of anchor excellence is flawed. The longer it takes to clean your anchor the more dangerous the issue.

Today there is a huge range of anchors available of different designs. You don't need to use an anchor with known flaws. There are cheep and cheerful anchors, like Kobra, there are light, flat pack anchors like Fortress or the Lewmar clone, there are concave anchors with 'holes' in the fluke like Viking or Knox there are convex anchors like Excel and Kobra. 9 times out of 10 or 99 times out of 100 a Rocna is perfection - don't lose any sleep, don't rush out and buy new - just acknowledge - Rocna are not perfect.

BUT all anchors are a compromise - there is no perfect anchor. Know the weaknesses of your specific anchor, be careful whichever anchor you use and know that luck is commonly on your side. There were some spectacular failures, concluded to be a function of anchor design causing clogging. Reports more recently have been notable by their absence - in fact reports of modern anchors dragging at all have been notable by their absence. You should carry more than one anchor - even if only because you might lose (even if temporarily) your bower anchor. It would be wise to choose your back up with different characteristics to your primary and if you are in mud and you know there is going to be a big wind shift you can then use an anchor more appropriate to the conditions. Using the anchor you have replaced, with the flash new modern design, should not be your spare anchor - if its not good enough as your primary - its not good enough. There are plenty of reliable anchors - buy one. Over the time you own your yacht the costs are not significant. People buy anchors too big/small - check eBay - your second anchor might be there.

Take care, stay safe

Jonathan

 

[NormanS]

Jonathan, I think you're worrying too much. If you're not happy anchoring in good sticky mud, as I certainly am, confine yourself to anchoring in sand. I'm with Bouba with this one, and if the anchor comes up with mud on it, that Information gets filed in my head for future reference, as a good place to anchor. I've got a good and powerful deckwash pump, and I'm happy to use it.