Anchors - Bigger is Better ?

[JonJo]

Originally Posted by foggysail

OK, I am stumped! Barnakiel referenced BiB. In a later post Ocean Girl referenced BIB.Too many acronims, I admit I cannot keep up. But in my over 30 years in this stuf I have never heard of BIB or BiB. I thought from OG it could mean "BIG IS BETTER" . But look at Barnakiel's quote, he has bigger but the same anchor type.

Yeah I know its stupid... and I thought I was on top of things. Frankly, until today I never heard the term.

Relax Foggy,

Some one much wiser than me got tired of typing the title 'Bigger is Better' and shortened it to BIB. Its limited, as far as I know to this thread!

[JonJo]

Originally Posted by Snowpetrel

Jonjo. intersting ideas about the effect of momentum and the speed vs weight. Guess it really depends on the boat. In my limited experiance of light boats they just don't seem to load up the anchors like a heavy boat can, even with the extra windage a light boat might have?

If you access the PS article, or one of them, Kettlewell might have a link, I looked at loads on anchor rodes - but using our cat.

We used different scopes so each scope took basically a day's work. We have the technique sorted out now so all the trial and error's done. I had wanted to repeat the tests with a yacht (any yacht of 'cruising' size). As you can imagine I have not received any offers of a loan, yet. However recently this has changed and I now have access to a 50' x 12t cruiser racer, but it all takes time. It will not give answers but it might give indications.

[Snowpetrel]

It was interesting to see how snow petrel sat in commonweath bay in hurricane force katabatics. One 50lb fishermans on 60 meters of 10mm chain. Plus 5 shore lines she was trussed up like a turkey. She could not yaw and sail about and the wind was very consistant at maybe 70knots. So she just sat very comfortably head to wind with relatively light mooring loads.

Considering I could hardly breath when on deck (my cheeks were flapping!) I was impressed with how much less the loads were when the yawing and other dynamic loads are removed.

Get a boat to lie quietly and you possibly half the loads?

[Snowpetrel]

Originally Posted by JonJo

I now have access to a 50' x 12t cruiser racer, but it all takes time. It will not give answers but it might give indications.

I look forward to hearing how the tests go. It's some excellent work youre doing.

[JonJo]

Originally Posted by Snowpetrel

I look forward to hearing how the tests go. It's some excellent work youre doing.

Thanks Snowpetrel. I fully agree - stop yawing (or whatever anyone wants to call it) and you have minimised snatch loading caused by momentum. Its then 'just' windage. Its something to measure, maybe anchor the transoms with long stern lines?

[DumnMad]

Theory would say not so much momentum when the chain is held bar tight by the wind but a bigger factor when the chain is in catenary. In storm force winds the wave surge & pressure are trying to launch the boat downhill and more so if the waves are spilling.
I figured this is why the anchor charts indicate LOA is more important than boat weight.

[Bash]

Originally Posted by DumnMad

I figured this is why the anchor charts indicate LOA is more important than boat weight.

I don't see the charts making such a statement. It seems that both factors must be considered. What I don't see the charts taking into consideration is windage.

[DumnMad]

Bash, I don't see the charts saying that either, they just give the sizes.
But if you double the boat weight they up the anchor weight by around 50%.
And if you double the boat length for the same weight they up the anchor weight by around 100%

[onestepcsy37]

from the fwiw department.

i used a genuine cqr 45 for several years. in florida we have soft mud over clay. while the cqr generally held, it always seemed to have a little 'creep'. not noticeable on an overnight anchorage but noticeable if we stayed put for a few days. rode is all 3/8" chain, scope is never less than 7 to 1 (my self imposed minimum). boat weighs 20000lbs. in the bahamas i had problems with the cqr even penetrating the heavy clay bottoms; fortunately the water is warm and clear and diving on the anchor a lot more pleasant.

i switched to a manson supreme two years ago - same weight, 45lbs. huge improvement. it sets first time every time, doesn't creep at all. it seems to set almost immediately, unlike the cqr which would run along the bottom until it began to dig in. and that in florida or the bahamas.

the cqr is of course, convex; the manson, concave. the manson does bring up more bottom with it when i retrieve, but i consider that not a liablity but an asset; it's proof to me that the manson has really penetrated the bottom and dug itself in.

i also had a bruce for a short while. a 66 pounder. but it took forever to get down through the soft mud and begin holding in the hard sand in florida. in the bahamas, it wouldn't penetrate at all. after one really scary night at gun cay i took it off, replaced it with the cqr, and never used the bruce again.

just my two cents.

[Snowpetrel]

Originally Posted by JonJo

Thanks Snowpetrel. I fully agree - stop yawing (or whatever anyone wants to call it) and you have minimised snatch loading caused by momentum. Its then 'just' windage. Its something to measure, maybe anchor the transoms with long stern lines?

Yes, this would make an interesting test with your load cell. You might get a more accurate result by anchoring the bow sideways with two anchors set directly abeam to port and stb from the bow and a lightly loaded stern line to take some of the dynamic stretch out of the system. You could 'tune' the system with different loads to see how any resonance or for and aft momentum effects the anchor load.

Seems the other part of the BIB question is getting accurate ideas of the comparative loadings of different boats and configurations. The manufacturers charts often seem rather vague.

[JonJo]

Originally Posted by DumnMad

Theory would say not so much momentum when the chain is held bar tight by the wind but a bigger factor when the chain is in catenary. In storm force winds the wave surge & pressure are trying to launch the boat downhill and more so if the waves are spilling.
I figured this is why the anchor charts indicate LOA is more important than boat weight.

Waves are issue that I have not seen addressed.

We have tried to take all our measurements with minimum wave action. Mainly to reduce variables, there are plenty without the waves. We would accept waves are very significant but we are at the beginning and simplistically thought we would start without waves, as if one were in an anchorage sufficiently close to shore such that waves were not an issue.

We also could not decide how to measure them, waves, but have sorted that one out. We can use a rather large, tall, navigation mark, anchor nearby and take measurements from the mark. Another project for the future.

[JonJo]

onestepcsy37

I'm not sure I like your analysis that your failure with a CQR, convex, and success with a Supreme, concave should lead you to damn Convex. You will start to sound as if you want to join the Luddites. I think you will find that a Bruce is concave, like a Supreme, but whereas you might damn the concave Bruce you do not damn the concave Supreme. I might be totally wrong but the Boss, also concave, and ostensibly like a tarted up Bruce - might be different again. Again I have no idea but the broad roll bar base of the Mantus might not allow a concave to collect so much mud - time will tell. If you want to find the ultime problem with carrying mud in your roll barred anchor - just read the final few posts in the Manson Supreme and weed thread. The concave diehards do not like, nor believe, the thread - but it is about someone who really tried to make it work. Do not judge a book by its cover. Simplistically - do not damn Convex on the basis of the CQR. When, if,the opportunity arises, broaden your mind

[foggysail]

Originally Posted by JonJo

Relax Foggy,

Some one much wiser than me got tired of typing the title 'Bigger is Better' and shortened it to BIB. Its limited, as far as I know to this thread!

Foggy

[noelex 77]

Anchorright are naturally trying hard to promote convex anchors.

This is what Rex had to say about the reasons for the choice of convex design. Make up your own mind.

"When we originally developed the Sarca anchor we developed it in a concave design. It worked extremely well, but back in those days we didn't have winches......My son said to me ...... Gee dad, these anchors are working fantastic , but I cannot pull this up.
So we turned it the other way. "

YouTube

[downunder]

Originally Posted by noelex 77

Anchorright are naturally trying hard to promote convex anchors.

This is what Rex had to say about the reasons for the choice of convex design. Make up your own mind.

"When we originally developed the Sarca anchor we developed it in a concave design. It worked extremely well, but back in those days we didn't have winches......My son said to me ...... Gee dad, these anchors are working fantastic , but I cannot pull this up.
So we turned it the other way. "

YouTube

I believe he is refering to the original SARCA Supreme that was a concave roll bar anchor. The newer Super Sarca apparently has better holding power moving from concave to convex still with roll bar. It was the original Sarca Supreme that was tested in the american tests not the newer improved anchor.