G70 chain

GHA,

Maybe I posed the question in the Opening Post inadequately but one of the reasons for the thread was to elucidate where people might have had issues with the use of G70, issues that are simply not apparent with G30. I confess that I had not realised so few people had any experience of G70, it seems more acceptable in America. I had known about the problem of actually attaching HT chain to an anchor but had not appreciated that 'chain hooks' (or their alternatives) were such an issue (and an issue with those few that use them for G30). I have a cross section of answers or solutions for hooks, I'm honing them as you are soft shackles, but my chain links are simply too small for me to play around much with dyneema. My 5/6mm dyneema soft shackles, given to me to test, with a UTS of 12t - so great, but they will not fit my 6mm chain and are a bit overspeced for a bridle application.

I do note that some whom I know have used G70 don't want to share their experience - which might be a pity.

The big problem is you do not know what you don't know until someone points you in the right direction :( - so thread drift is very educational.

Jonathan
 
Neeves said:
) where the lighter chain has sacrificed much catenary.
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So much of what you say makes sense but I'd be very careful stating that lighter chain provides less shock absorption through catenary without thinking through the physics (and anyone who has snorkelled over their chain in more than 15-20 knots of wind).The shock absorption characteristics of chain catenary are based on the difference in the curve of the chain between one wind strength (or momentum of the boat when it veers) and the peak wind strength in a gust (or when the boat comes to a halt at the end of the veer). In moderate winds and above there isn't much curve left and every tiny reduction in curve takes a bigger force to achieve it, so in effect you've lost the catenary advantage at the time when you actually start needing elasticity.

So as this happens even to 12mm chain and probably at bit above that then the catenary disadvantage of lighter chain has only a tiny impact under any strain - so snubbers and reducing veering are your only tools to reduce snatch loads. But this is debated to death here I know with a considerable number of people having watched their chains go taut and almost straight at 20knots of wind still thinking there is a catenary curve somewhere at 30 knots plus to help them.
 
Totally agree.

I'm not sure that you need a higher windspeed to pull 12mm chain taut. 12mm chain would be used on a larger vessel which would have extra momentum.

But, arguing against myself, I'm not sure that a larger yacht, of the size to need 12mm chain actually veers as much so maybe the issue is only one of smaller yachts and those, say upto 55' (I do see a number of lightweight high windage, quite large. new yachts). I simply don't know I'd have to sit and watch, or be on a 60' yacht in specific anchorages to find out - and that's not likely to happen.

But the vast majority of us have yachts in the 25' - 45' range (maybe higher?) and many of us buy AWBs so yawing is an issue and catenary a myth - above, say, 25 knots.

One of the little tests to do is touch your anchor when all the chain is just off the seabed, you will find it twitches, touch your chain at 30 knots and every movement of the yacht and chain is transmitted to your anchor and it twitches more. Add a snubber (and bury chain if you can) and you reduce the twitching. That twitching reduces the shear strength of the seabed surrounding the anchor. Deeply buried anchors with chain buried and supported by a snubber maintain a higher sheer strength seabed.

Jonathan
 
Neeves said:
Totally agree.

I'm not sure that you need a higher windspeed to pull 12mm chain taut. 12mm chain would be used on a larger vessel which would have extra momentum.

But, arguing against myself, I'm not sure that a larger yacht, of the size to need 12mm chain actually veers as much so maybe the issue is only one of smaller yachts and those, say upto 55' (I do see a number of lightweight high windage, quite large. new yachts). I simply don't know I'd have to sit and watch, or be on a 60' yacht in specific anchorages to find out - and that's not likely to happen.

But the vast majority of us have yachts in the 25' - 45' range (maybe higher?) and many of us buy AWBs so yawing is an issue and catenary a myth - above, say, 25 knots.

One of the little tests to do is touch your anchor when all the chain is just off the seabed, you will find it twitches, touch your chain at 30 knots and every movement of the yacht and chain is transmitted to your anchor and it twitches more. Add a snubber (and bury chain if you can) and you reduce the twitching. That twitching reduces the shear strength of the seabed surrounding the anchor. Deeply buried anchors with chain buried and supported by a snubber maintain a higher sheer strength seabed.

Jonathan
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I agree with all you have said but in addition veering or yawing is not simply size dependant. Having a ketch we yaw a lot less than a same size sloop. The wind resistance of the mizzen helps to keep the boat pointing to windward. We have spent lots of time anchored with friends who have the same hull as us but theirs is rigged as a sloop so this is a direct comparison. It seems to me that yachts with a mast further forward sail around their anchor a lot more than those with a mast slightly further back. We have watched small light yachts in gusty 40 kt conditions sailing around their anchor like a wild horse on a long rope. The loads the boat imposes on the anchor as it veers must be considerable. A great way to see how your boat behaves in these conditions is to leave your chart plotter on maximum zoom for a few hours and look at the track pattern.
We have also seen yachts making great use of riding sails. They seem to transform the behaviour of anchored boats that would otherwise be wild horses
 
I know about riding sails but have never ever seen one used in Australia. I did wonder about how to install one on our cat, but never solved the conundrum. I often leave the chart plotter on then save the plot (only of the moment in the anchorage - you need a decent accurate plotter to get a useful plot).

But veering is not only about 'design' and having or not having a riding sail. Some anchorages 'look' delightful and safe but in very strong winds they funnel bullets in totally unpredictable directions. We have sat and been buffeted by really strong bullets at 180 degrees to each other - and nothing can stop you yawing in these circumstances the answer is (such anchorages tend to be small) get close to shore, set anchor(s) and shore lines and you then simply do not move. The net of lines, anchor/shore lines are common practice in higher latitudes.

Yachts do vary in how they yaw - but I've never thought much about differences in behaviour. Your comment of 2 yachts with the same hull but different mast configurations is the first time I have heard of anyone making a serious observation. Interestingly, or it is to me, Lagoon are moving their masts back, which is what Prout did decades ago - different reasons to anchoring (though it might be part of the whole philosophy) - but they may find an unexpected benefit.

I'm not ignoring design being an issue - its one of more than one issue.

I noted recently when we were at anchor for 4 days with winds at the masthead of 30 knots and a few hours at 35 knots, that we were not veering, really very steady. The shelter was a 10m high 'ridge' so not very much. and beyond was open sea. I wondered if the 20m snubbers were reducing veering - but it might have been that the wind was constantly in one direction without much shear. Normally we would veer and but would have used shorter snubbers - but previously I would have said that was because the wind had more shear.

I did measure loads when we veered at at very short scope, 2.75:1, we were generating just under 700kg snatch loads at around 30 knots, no snubber. It was quite frightening and I was concerned for the yacht so did not extend that test for long. When we anchored, above, at 30knots we were at 7:1 scope (but 6mm chain - so looks straight - I measured 50kg at the end of the snubber/bridle (I didn't believe it until i found I could hold, restrain, the snubber).

I have considerable confidence in snubbers/bridles - as long as they are both long and elastic (which most aren't and this installs confidence in the idea of lightweight chain.

Jonathan
 
Re the "net of lines, anchor/shore lines......".

If you are doing that, would you rig it so that the boat can still swing head to wind, as in a Bahamian Moor? Or are you suggesting that the boat is moored in fixed attitude, with lines radiating out from several points on the boat.
In my experience, the former is fine, but the latter puts undue stress on the boat, and is very uncomfortable.
 
NormanS said:
Re the "net of lines, anchor/shore lines......".

If you are doing that, would you rig it so that the boat can still swing head to wind, as in a Bahamian Moor? Or are you suggesting that the boat is moored in fixed attitude, with lines radiating out from several points on the boat.
In my experience, the former is fine, but the latter puts undue stress on the boat, and is very uncomfortable.
Click to expand...

In my experience of lines to shore then the key thing is that there is no fetch but otherwise it seems fine in a cross wind with anchor from the bow and two shore lines at a 45 degree ish angle. Because the anchor is pulling in one direction only the once set it seems to stay and just dig in a little further.

The big advantage for us is that we veer about a lot and lines to shore feels better and safer. Still thinking about a riding sail so experimenting in increasing windage aft to see if it makes a difference.
 
Neeves said:
I know about riding sails but have never ever seen one used in Australia. I did wonder about how to install one on our cat, but never solved the conundrum. I often leave the chart plotter on then save the plot (only of the moment in the anchorage - you need a decent accurate plotter to get a useful plot).

But veering is not only about 'design' and having or not having a riding sail. Some anchorages 'look' delightful and safe but in very strong winds they funnel bullets in totally unpredictable directions. We have sat and been buffeted by really strong bullets at 180 degrees to each other - and nothing can stop you yawing in these circumstances the answer is (such anchorages tend to be small) get close to shore, set anchor(s) and shore lines and you then simply do not move. The net of lines, anchor/shore lines are common practice in higher latitudes.

Yachts do vary in how they yaw - but I've never thought much about differences in behaviour. Your comment of 2 yachts with the same hull but different mast configurations is the first time I have heard of anyone making a serious observation. Interestingly, or it is to me, Lagoon are moving their masts back, which is what Prout did decades ago - different reasons to anchoring (though it might be part of the whole philosophy) - but they may find an unexpected benefit.

I'm not ignoring design being an issue - its one of more than one issue.

I noted recently when we were at anchor for 4 days with winds at the masthead of 30 knots and a few hours at 35 knots, that we were not veering, really very steady. The shelter was a 10m high 'ridge' so not very much. and beyond was open sea. I wondered if the 20m snubbers were reducing veering - but it might have been that the wind was constantly in one direction without much shear. Normally we would veer and but would have used shorter snubbers - but previously I would have said that was because the wind had more shear.

I did measure loads when we veered at at very short scope, 2.75:1, we were generating just under 700kg snatch loads at around 30 knots, no snubber. It was quite frightening and I was concerned for the yacht so did not extend that test for long. When we anchored, above, at 30knots we were at 7:1 scope (but 6mm chain - so looks straight - I measured 50kg at the end of the snubber/bridle (I didn't believe it until i found I could hold, restrain, the snubber).

I have considerable confidence in snubbers/bridles - as long as they are both long and elastic (which most aren't and this installs confidence in the idea of lightweight chain.

Jonathan
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We have anchored where we were getting 40kt gusts coming around a hill. The direction of the gusts varied by 90deg as the wind came around opposite sides of the hill. In the bigger gusts when we were pointing 90 deg from the direction of the next gust the yacht would be laid over to about 20 deg and she would veer until the chain started to pull on the bow. Being a deep keel, heavy boat the motion was quite reasonably but others around us in lighter boats put in some serious mileage around their anchor. The lighter boats with shallower draft than us that were using a riding sail didnt veer so dramatically as similar boats without one but they did heel over in the initial gust until the windage of their riding sail pushed the bow into the wind. The other advantage I can see with the riding sail up the backstay is that in rolly amchorages they do seem to reduce the roll. We set out mizzen bar tight occationally to reduce rolling in particulary rolly anchorages for the same reason
 
NormanS said:
Re the "net of lines, anchor/shore lines......".

If you are doing that, would you rig it so that the boat can still swing head to wind, as in a Bahamian Moor? Or are you suggesting that the boat is moored in fixed attitude, with lines radiating out from several points on the boat.
In my experience, the former is fine, but the latter puts undue stress on the boat, and is very uncomfortable.
Click to expand...

Effectively immovable - lines, or anchor, off the stern anchors off the bow in a 'V'. Can be done with 3 lines better with 4.

If you can get close to shore the bullets are much less. Close to shore you don't need to worry about swinging to somewhere more shallow. You can also get more boats into small spaces.

But I agree if you cannot get close to shore - there could be an issue. There is another issue if you are far from shore - you need good marks on the shore lines - but the idea is to so close to shore that no-one would think of passing inshore of you. Cheap LED fishing buoy markers on the lines work well.

Edit,

Having said that - where we sail its unusual to see another yacht. This is only Tasmania, but not frequented that much - the words 'Bass Strait' and 'Great Southern Ocean' are great deterrents - maybe like St Kilda and Shetlands?

Close edit
 
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As
Neeves said:
RobbieW,

That's a wordy post, even more wordy than mine - but Krusty's has more useful content. :)

Thanks, I'll have a read at leisure.

Jonathan
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Well - although I must have read Krusty's quote or something similar when thinking about reducing veering, when I read it this time my mind went in the opposite direction.

The quote, "A yacht ranges about on her anchor because her ''Centre of Windage'' (CW) is forward of her underwater ''Centre of Lateral Resistance'' (CLR): it is an 'unstable configuration' in that direction, and like all unstable systems, it is easily set oscillating.
A Riding Sail works because it shifts the CW behind the CLR, to become a stable configuration. "

So to reduce veering all I've ever really thought about (apart from one random experiment) is to shift the CW behind the CLR by increasing aft windage.

But this time I thought that as water is so much denser than air (784 times when I just looked it up) then surely you need far less surface area if you design something that shifts the CLR forward of the CW instead. But we don't change our underwater profiles, but instead think only of sails and windage above the water line,

So, if as a thought experiment, I had a dagger board right at the bow , would that move my CLR forward? Or a pair of drogues on very short lines from a bridle just below the waterline?

Experiments will follow, although alas I'm not out at the boat for another 6 weeks.
 
A mizzen set as a riding sail can only "do something" when the wind strikes it at an angle. Think of a servo pendulum vane gear as a comparable case. When the wind is from ahead, all the mizzen can do is flog itself to bits. Once the boat has started a sheer, the mizzen will fill with wind and do something - probably to increase the oscillation.

We are assuming that a boat at anchor will be wind rode but in many parts of the world she will be tide rode, so a riding sail will be worse than useless.

In my capacity as Resident Dinosaur, I'd suggest giving the boat a sheer - by lashing the helm down of course, and, case need, by putting a spring on the cable. Boats I have owned have settled down nicely when I did this, even when the tide turned...
 
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I have, and occasionally use, a twin anchor sail, probably much the same as that used by the late Krusty. Because it's a twin sail, hoisted on the mizzen, it always presents area to the wind, unlike a standard mizzen sail, which only presents to the wind once yawing has occurred. For me now, yawing is not a problem.
 
Neeves said:
Effectively immovable - lines, or anchor, off the stern anchors off the bow in a 'V'. Can be done with 3 lines better with 4.

If you can get close to shore the bullets are much less. Close to shore you don't need to worry about swinging to somewhere more shallow. You can also get more boats into small spaces.

But I agree if you cannot get close to shore - there could be an issue. There is another issue if you are far from shore - you need good marks on the shore lines - but the idea is to so close to shore that no-one would think of passing inshore of you. Cheap LED fishing buoy markers on the lines work well.

Edit,

Having said that - where we sail its unusual to see another yacht. This is only Tasmania, but not frequented that much - the words 'Bass Strait' and 'Great Southern Ocean' are great deterrents - maybe like St Kilda and Shetlands?

Close edit
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Sorry, but I would hate to be moored broadside on to some of the wind strengths in which I have been anchored. The heeling and screaming would do my head in. (The screaming would be coming mainly from the masts, but I might also contribute). The loading on the boat's fittings would also be massive. If I was ever persuaded to take lines ashore, I would have to connect them to the anchor rode, below keel level, so that the boat would still lie head to wind.
 
From memory Norman has commented in the past on his split riding sail and I think he was the motivation behind my having a look. I can see it being easily possible to rig on a mizzen mast and I can understand, as Normal says. that one 'side' of the device is always presented to the wind. For the life of me I could not work out how to devise any arragangement on a catamaran without a back stay. The luff could be attached to the mainsail topping lift, the head lifted tight by the main halyard - but what to do with the clews. The clews would nearly vertical and 2-3m above the transoms. And at this point I was, well, clueless.

I give up easily.

Jonathan
 
NormanS said:
Sorry, but I would hate to be moored broadside on to some of the wind strengths in which I have been anchored. The heeling and screaming would do my head in. (The screaming would be coming mainly from the masts, but I might also contribute). The loading on the boat's fittings would also be massive. If I was ever persuaded to take lines ashore, I would have to connect them to the anchor rode, below keel level, so that the boat would still lie head to wind.
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Totally agree. With a constant or steady wind direction you would not want to be secured cross wind.

But if the gusts of strong bullets at 180 degrees then, in certain locations, its better to get out of the bullets and seek the shelter close to shore, obviously if the shore does not offer the shelter stay out.

Its horses for courses.

Jonathan
 
GHA,

As we seem to have drifted.

I'm interested in your Bahamian moor, Ive only once had the need and did not use it.

I know the theory, 2 rodes off the bow in a straight line with the vessel moored at the centre of the line. Anchors at the end of each rode allow the vessel to sit to wind or tides that move through 180 degrees.

One rode is presumably the primary rode and the other the secondary rode, that most of us keep in a locker. You deploy the secondary rode - how do you stop the 2 rodes twisting round each other. I assume you attach to a swivel but where, how is the swivel attached.

Its not that much of a drift - as with a smaller link there is less room to attach anything, or it needs to be small - and also HT.

Jonathan
 
Neeves said:
Totally agree. With a constant or steady wind direction you would not want to be secured cross wind.

But if the gusts of strong bullets at 180 degrees then, in certain locations, its better to get out of the bullets and seek the shelter close to shore, obviously if the shore does not offer the shelter stay out.

Its horses for courses.

Jonathan
Click to expand...

A couple of weeks ago, we were anchored in a sealoch on the east side of North Uist. Our normal spot is in a sheltered bay, which happens to be right under a cliff, which is part of a moderate isolated hill. I should have known better. We were getting frequent strong gusts, interspersed with periods of total calm. OK during the day, but not conducive to sleeping. We lifted the anchor, and moved half a mile or less, but still in the loch, and anchored just offshore of low ground, behind which there is a extensive freshwater loch. We then had a completely steady 25 knots. Perfect peace.
 
NormanS said:
Sorry, but I would hate to be moored broadside on to some of the wind strengths in which I have been anchored. The heeling and screaming would do my head in. (The screaming would be coming mainly from the masts, but I might also contribute). The loading on the boat's fittings would also be massive. If I was ever persuaded to take lines ashore, I would have to connect them to the anchor rode, below keel level, so that the boat would still lie head to wind.
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It's a very common way in the Med as you know whether the shore lines are 3m to a quay or 50m back to rocks and it does seem to work well for those who have dug their anchors in. You can't really swing around the ropes joining point as you would bash the other boats alongside you anchored in the same configuration.
 
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