GHA
Well-Known Member
What size boat? I went up a little to 25Kg, it's never ever missed a beat either. Proves nothing.
Why has the market not embraced alloy anchors?
- Thread starter Neeves
- Start date
What size boat? I went up a little to 25Kg, it's never ever missed a beat either. Proves nothing.
knuterikt
Well-Known Member
I have two Spade 100 anchors, the one made of aluminium I got for the same price as the steel one due to the supplier being out of stock of steel version.
A 100 = 9kg, S 100 = 20kg same surface area.
I prefer the steel on one, it's better at digging in when the surface is hard or covered with weed, the holding power is the same for both once they are fully dug in.
Steel version is permanently on the bow roller.
The aluminium on is used as stern anchor and is lighter to take in the dingy.
A 100 = 9kg, S 100 = 20kg same surface area.
I prefer the steel on one, it's better at digging in when the surface is hard or covered with weed, the holding power is the same for both once they are fully dug in.
Steel version is permanently on the bow roller.
The aluminium on is used as stern anchor and is lighter to take in the dingy.
dom
Well-Known Member
48' I'm guessing since yours is steel it weighs around 256x more
BTW, a friend of mine looked at the 25 but for some reason was harder to get hold of. No idea why.
Neeves
Well-Known Member
Zing - maybe you can elaborate
Why precisely will the bigger anchor hold - if it is not fully buried it's buried area, or volume will be similar to that of the smaller anchor. It cannot be buried 'more' as the tension are the same. The difference is that the shank will protrude further upward, providing a bigger lever arm to tip the anchor over when the yacht veers.
If we think of this in its simplest form - a large Fortress will have roughly the same fluke area buried as a small one (actually the big one will be buried less because it is made from a thicker plate) - what makes the bigger one better and thus more reliable?
What is important is that the anchor design is such that the anchor will continue to dive, even in a hard or soft seabed with increased tension - and fortuitously most of the new anchor have this characteristic. However they do depend, in diving further, that the tension is roughly in the same straight line.
But hold is measured in a straight line pull - a pull at an angle, from the side (veering) or in the vertical (horsing) with a longer lever arm and a fluke set in lower shear stress substrate - ie shallow.......??
Now explain why the bigger anchor is better.
Jonathan
Why precisely will the bigger anchor hold - if it is not fully buried it's buried area, or volume will be similar to that of the smaller anchor. It cannot be buried 'more' as the tension are the same. The difference is that the shank will protrude further upward, providing a bigger lever arm to tip the anchor over when the yacht veers.
If we think of this in its simplest form - a large Fortress will have roughly the same fluke area buried as a small one (actually the big one will be buried less because it is made from a thicker plate) - what makes the bigger one better and thus more reliable?
What is important is that the anchor design is such that the anchor will continue to dive, even in a hard or soft seabed with increased tension - and fortuitously most of the new anchor have this characteristic. However they do depend, in diving further, that the tension is roughly in the same straight line.
But hold is measured in a straight line pull - a pull at an angle, from the side (veering) or in the vertical (horsing) with a longer lever arm and a fluke set in lower shear stress substrate - ie shallow.......??
Now explain why the bigger anchor is better.
Jonathan
NormanS
Well-Known Member
55 knots eh? I don't really want to get into a pissing contest, but at 55 knots I'm not thinking of needing to have my engine running. Try 74 knots gusts, and steady in the mid 60s. It ain't pleasant.:disgust:
Zing
Well-Known Member
I did assume the anchors were properly dug in. For other specialised scenarios, I have no idea really, including for the other examples you gave.
noelex
Well-Known Member
I agree Norman, it is an important difference
My Fortress has had very poor “holding” over the last few months in many different anchorages. Some of these have had nice mud bottoms where I would have expected the Fortress to do well. I have even tried altering the fluke angle but this has made absolutely no difference. I have not checked with a load cell, but I suspect the “holding ” of my Fortress anchor has been close to zero for all this time.
Of course if I took it out of the anchor locker and dropped it in the water, its “holding” would be much better
.The above is nonsense, but it illustrates how confusing and silly it is to use the term “holding” to indicate anything other the potential or if you prefer the maximium holding ability that would be developed just before dragging. I am sure this is in fact exactly what most posters mean when they refer to an anchors “holding”.
Last edited:
thinwater
Well-Known Member
Northill. But either way, you will foul the fluke when the tide swings.
GHA
Well-Known Member
48' I'm guessing since yours is steel it weighs around 256x more
BTW, a friend of mine looked at the 25 but for some reason was harder to get hold of. No idea why.
Boat is about 10.5T with all the cruising bits & without full water & diesel so towards the top end of 20Kg sizing. Commonplace for full time cruisers to go up a bit, can't be too far off universal. Apart from one lone voice on the internet.....
Can't really understand how a slightly bigger anchor wouldn't set solid with a load of force any different to a smaller hook, I give mine a good wallop with some reverse momentum usually anyway, if the bow dips down as the boat bangs to a halt then it's a good sign that all is well.
thinwater
Well-Known Member
What is soft mud? The US Navy used to have a practice where they would send couple guys out in a small boat with a blunt stake and a hammer:
• Very dense sand: more than 50 blows/foot.
• Sand: 25-50 blows/foot.
• Hard clay: more than 16 blows/foot.
• Consolidated mud/clay: 4-16 blows/foot.
• Soft mud: 2 blows/foot.
• Very soft mud/silt: you don't need the hammer to push it in several feet.
• Very dense sand: more than 50 blows/foot.
• Sand: 25-50 blows/foot.
• Hard clay: more than 16 blows/foot.
• Consolidated mud/clay: 4-16 blows/foot.
• Soft mud: 2 blows/foot.
• Very soft mud/silt: you don't need the hammer to push it in several feet.
GHA
Well-Known Member
I agree Norman, it is an important difference
My Fortress has had very poor “holding” over the last few months in many different anchorages. Some of these have had nice mud bottoms where I would have expected the Fortress to do well. I have even tried altering the fluke angle but this has made absolutely no difference. I have not checked with a load cell, but I suspect the “holding ” of my Fortress anchor has been close to zero for all this time.
Of course if I took it out of the anchor locker and dropped it in the water, its “holding” would be much better
The above is nonsense, but it illustrates how confusing and silly it is to use the term “holding” to indicate anything other the potential or if you prefer the maximium holding ability that would be developed just before dragging. I am sure this is in fact exactly what most posters mean when they refer to an anchors “holding”.
Very funny
And guaranteed that you'll get the sharp end of a keyboard when your stalker wakes up
Birdseye
Well-Known Member
Your steel anchor is not hardened ie heat treated.
moomba
N/A
Hardened by drop forging rather than castings and plate steel, the process of drop forging, the grain flows of the steel are altered, conforming to the shape of the part. making it stronger (tougher, harder, etc) just a play on words
the point was that the Steel anchor will be less pliable to that of Aluminum
vyv_cox
Well-Known Member
The shanks of Rocna and Delta (maybe others) are most definitely heat treated. It is not possible to achieve strengths above maybe 300 MPa without heat treatment regardless of manufacturing method (forging, casting, hot rolled plate, etc.) Rocna shanks are around 700 Mpa, Delta a bit less.
Drop forged components, when well designed, give additional fatigue resistance but still need to be heat treated for strength.
noelex
Well-Known Member
And guaranteed that you'll get the sharp end of a keyboard when your stalker wakes up
I hope the absurdity of my example makes an impression. Some posts are using “holding” or “holding ability” to refer to an anchor’s actual current holding rather than the more conventional use of the term to mean the potential holding ability.
It is true that if yacht is not dragging the actual holding force is the same if the anchor is big or small, if the substrate is good or bad, if the anchor is good or poor, etc etc.
It is going to make anchor threads even more confusing (if this is possible
) if we adopt this terminology. The sensible use of the term an anchors “holding ability” is the point where the anchor will just start to drag if the force increases further. This value will vary depending on the type of anchor, scope, holding ground, size of anchor, etc, etc just as you would expect.
To use an analogy if we take two otherwise identical cars, but one has a large and powerful engine and the other has a small and less powerful engine. Driving along the freeway at a steady 100 km/h both engines are producing the same horsepower (ignoring minor frictional differences) and both cars have the same acceleration (0).
However, the car with the larger engine can produce more hp and have better acceleration than the car with a smaller engine. To state both large and small engines produce the same hp and acceleration is misleading and obviously silly even though in some situations, providing we ignore the greater potential of the larger engine the statement may be technically correct.
Last edited:
NormanS
Well-Known Member
Actually the shank of a fisherman anchor is generally of largely consistent section throughout it's length, and initially until fully dug in, is anything but lying on the bottom. However, I think you may have your terminology mixed up. The stock of a fisherman anchor is designed to lie flat on the bottom, in order to orientate the anchor, so that one of the available flukes is bearing down on the seabed, assisted by the complete weight of the two flukes, and half the weight of the stock. In that respect, the stock serves the same function as the "roll bar" on some more modern anchors.
If you think back to the days of the old sailing ships, their anchor flukes were somewhat similar to those of a fisherman's, but often the stock was made of wood. Iron bound wood certainly, but maybe these guys knew something?
I'm not suggesting that everyone, or indeed anyone, should dash out and get a Fisherman's anchor, but they have their uses, and being able to penetrate hard or weedy ground, is one of their clear advantages.
vyv_cox
Well-Known Member
As I said, there is no consistent definition of a Fisherman anchor. We are clearly considering different designs under the same generic name.
NormanS
Well-Known Member
There is however, consistent definition of the parts of a Fisherman anchor. Please show me a Fisherman anchor, sitting with a fluke ready to drive into the seabed, and yet with its shank lying on the seabed. I suspect that you are thinking of the part generally known as the stock.
vyv_cox
Well-Known Member
Quite possibly, not being an authority on fisherman anchors. However, I would imagine the non-business end would be pressing the seabed more heavily than the fluke, which is where we started.
NormanS
Well-Known Member
Thanks for your grudging apology. It's actually quite easy to remember which part the "Stock" is, if you think of what a "stockless anchor" looks like.
Anyway, since I don't think Fisherman anchors are ever made in (aluminium) alloy, I suggest we leave it there, and agree to differ.
Last edited: