Anchors - Bigger is Better ?

[JonJo]

Originally Posted by Jim Cate

Could you please explain why this is so? Counter intuitive to me...

Jim

A hollow, sealed, steel shank will contain air. When the sealed shank is dropped into the galvansing bath at about 570 degrees C the air is heated and expands, (this is all the fault of Robert Boyle I believe) I guess it depends on the amount of air and the thickness of the shank but considering an Ultra type shank - the resultant air pressure will blow the shank apart, there will be zinc everywhere. Galvanisers will not galvanise sealed bodies of this type. Spade's being open do not suffer with this issue - a steel Ultra would.

Seems intuitive to me.

You could make the shank open, as per Spade, but I am guessing that the buoyancy of the shank is part of the balance - but this is a guess.

Jonathan

[Jim Cate]

Originally Posted by JonJo

A hollow, sealed, steel shank will contain air. When the sealed shank is dropped into the galvansing bath at about 570 degrees C the air is heated and expands, (this is all the fault of Robert Boyle I believe) I guess it depends on the amount of air and the thickness of the shank but considering an Ultra type shank - the resultant air pressure will blow the shank apart, there will be zinc everywhere. Galvanisers will not galvanise sealed bodies of this type. Spade's being open do not suffer with this issue - a steel Ultra would.

Seems intuitive to me.

You could make the shank open, as per Spade, but I am guessing that the buoyancy of the shank is part of the balance - but this is a guess.

Jonathan

Actually, Jonathon, if you apply the combined gas law you will find that with a fixed volume, the pressure increases as the ratio of temperatures expressed in Kelvin. In this case that is roughly 843:295 which is about 2.9:1. So, when the putative hollow, sealed shank is dipped into the galvo bath, the pressure goes from around 15 psi to around 42 psi... hardly enough to blow up a steel anchor shank.

I see no reason that one can't galvanize a hollow steel shank, sealed or not.

Cheers,

Jim

[Delfin]

Originally Posted by Jim Cate

Actually, Jonathon, if you apply the combined gas law you will find that with a fixed volume, the pressure increases as the ratio of temperatures expressed in Kelvin. In this case that is roughly 843:295 which is about 2.9:1. So, when the putative hollow, sealed shank is dipped into the galvo bath, the pressure goes from around 15 psi to around 42 psi... hardly enough to blow up a steel anchor shank.

I see no reason that one can't galvanize a hollow steel shank, sealed or not.

Cheers,

Jim

Jim, why does Spade pour the lead in after galvanizing? Why not just pour the lead in, box it off like the stainless Ultra and then galvanize? Bit confused on that, since one of the complaints leveled against the Spade is that you can't re-galvanize easily because the lead melts and has to be recovered and re-poured, or so I think I've been told.

[noelex 77]

Originally Posted by Delfin

You need to do more research. In this test, a convex anchor showed similar performance to the convex designs, with the ballasted toe Spade outperforming the roll bar anchors. http://www.newmorning.info/page65/fi...hor%20test.pdf

Delfin I am not sure of your point. The top anchors in this test that you quote behind the Fortress were all concave anchors of the Spade, Rocna and Manson Supreme. The only other concave anchor in the test was the quirky Oceane (which was erratic but overall in the middle of the pack) The convex anchors all did significantly worse than the concave anchors. Surely this supports my conclusion:

Originally Posted by noelex 77

You must be reading different anchor tests.
I think the anchor test have shown overwhelmingly the superiority of the concave anchors and the (flat) aluminium Fortress.

[Delfin]

Originally Posted by noelex 77

Delfin I am not sure of your point. The top anchors in this test that you quote behind the Fortress were all concave anchors of the Spade, Rocna and Manson Supreme. The only other concave anchor in the test was the quirky Oceane (which was erratic but overall in the middle of the pack) The convex anchors all did significantly worse than the concave anchors. Surely this supports my conclusion:

No, the Hydrobubble is a convex anchor. Its performance in the first study was the same as the Manson and the Rocna in one location, but worse in another.

In the second study, the Excel and Kobra were deemed superior to the concave group, if only marginally so.

In the PS test, the convex anchors (Excel, Kobra) beat out the concave anchors in one seabed, and lost slightly in another.

My point was that the assertion that all convex anchors are always inferior in tests compared to convex is clearly wrong, as these tests indicate, so no, your conclusion is not supported by the data.

We can agree, nor have I ever doubted, the superior holding capacity of the Fortress, which is why I carry their Guardian as a back up and supplemental storm anchor.

[noelex 77]

Originally Posted by Delfin

No, the Hydrobubble is a convex anchor. Its performance in the first study was the same as the Manson and the Rocna in one location, but worse in another.

So behind the aluminium Fortress the next three top anchors were concave Spade,concave Rocna and concave Manson Supreme (of only four concave anchors in the test). The next best anchor was the unconventional convex Hydrobubble (with an aluminium shank) which only beat the one remaining concave anchor (the quirky Oceane).

From these results you conclude concave and convex anchors are equally good

[Delfin]

Originally Posted by noelex 77

So behind the aluminium Fortress the next three top anchors were concave Spade, Rocna and Manson Supreme (of only four concave anchors in the test). The next best anchor was the unconventional convex Hydrobubble (with an aluminium shank) which only beat the one remaining concave anchor (the quirky Oceane).

From these results you conclude concave and convex anchors are equally good

And I thought you didn't believe one study could tell us anything. Now I'm confused. The convex Hydrobubble tests better in some, and slightly worse in other tests. My point has nothing to do with they Hydrobubble, but merely that your statement

Originally Posted by noelex 77

I cannot think of single anchor test where the convex anchors have done anywhere near as well as the concave.

is wrong, whether you wish to acknowledge it or not.

You see, this is why anchor threads become so tedious. People make declarative statements like yours above, or

Originally Posted by Cotemar

I Would recommend a new generation anchor that is either flat or concave as the convex ones have a problem bend that lets the horses run a bit.

without providing the slightest empirical basis for the conjecture. When others who have a great deal of experience testing anchors (JonJo), or building and testing them (Congo) try to correct the record, they are ignored, or their integrity impugned. I've posted objective test results that disprove statements like yours and Cotemar's, but such data rolls off like water off a duck's back.

Your opinion and Cotemar's is that concave anchors are superior (always, you say) than convex designs because of a "problem bend" (so says Cotemar). My position is that ample evidence exists in objective tests to show that none of what you say is true.

To each his own opinion, I guess.

[Jim Cate]

Originally Posted by Delfin

Jim, why does Spade pour the lead in after galvanizing? Why not just pour the lead in, box it off like the stainless Ultra and then galvanize? Bit confused on that, since one of the complaints leveled against the Spade is that you can't re-galvanize easily because the lead melts and has to be recovered and re-poured, or so I think I've been told.

Well, I'm not sure about that issue. I suspect that it has to do with the difference in coefficients of expansion between lead and steel. lead being nearly three times higher (29 vs ~10.8 ppm/deg C). Unlike a gas filled cavity, the pressure which could be built up by an expanding solid in a sealed container is quite high and could indeed burst things apart.

Lead is pretty malleable, and I've wondered if simply leaving some head space in the ballast chamber in the anchor would prevent destructive forces building up. However, I suspect that some wily anchor builder (say CQR for instance) would have tried this out at some time, and since we don't see the practice in use, I'd guess that it fails to work! I know that my friends with CQR anchors go through the removal/replacement of lead exercise each time the anchor is regalvo'd, and it is a PITA for them.

Cheers,

Jim

[Delfin]

Originally Posted by Jim Cate

Well, I'm not sure about that issue. I suspect that it has to do with the difference in coefficients of expansion between lead and steel. lead being nearly three times higher (29 vs ~10.8 ppm/deg C). Unlike a gas filled cavity, the pressure which could be built up by an expanding solid in a sealed container is quite high and could indeed burst things apart.

Lead is pretty malleable, and I've wondered if simply leaving some head space in the ballast chamber in the anchor would prevent destructive forces building up. However, I suspect that some wily anchor builder (say CQR for instance) would have tried this out at some time, and since we don't see the practice in use, I'd guess that it fails to work! I know that my friends with CQR anchors go through the removal/replacement of lead exercise each time the anchor is regalvo'd, and it is a PITA for them.

Cheers,

Jim

That makes sense.