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Anchoring: Kellets versus Buoys?
Hi all
Having looked at Chapman's 'Piloting, Seamanship and Small Boat Handling' (now available in your local library for UK readers), I was a bit surprised to see recommended that a mooring-type buoy be used rather than attaching some other flotation to the intact anchor chain (one more link to go wrong). I think Hinz discusses this in his books but I haven't managed to get hold of any in the UK. I know this method of anchoring is for extreme conditions but has anyone any experience with it or the alternative method of using weights slid down the rode. I would guess there is a better argument for avoiding shock loading than there is for anchor dragging and that the buoy method is better at doing this. I am assuming all chain here due to chafe resistance. Regards Steve Remove defcv if etc. |
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#3
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Aa kellet and a float have oposite effects on the cantenary of the rode. A
float deflects the cantanary upwards while a kellet deflects it downwards. A downward deflection increases the angle of attack of the anchor's flukes thus increasing the net holding power under steady moderate load. If anything a float will reduce the angle of attack. While this reduces the ultimate holding power somewhat the float will react faster over a greater distance to shock loads. Once the tension on the rode is high enough to remove the cantenary the difference is pretty minimal. In an anchorage with a short fetch exposed to a more or less steady wind load I would prefer a kellet. With a longer fetch generating larger swells the float may be the better choice. -- Glenn Ashmore I'm building a 45' cutter in strip/composite. Watch my progress (or lack there of) at: http://www.rutuonline.com Shameless Commercial Division: http://www.spade-anchor-us.com "Marc Auslander" wrote in message ... I have read, and it seems plausible, that in bad enough conditions, a kellet does no good because it can't really deflect the rode very much. And it may cause trouble if it starts to bounce up and down - pulling up on the rode on the upswings. I would think a mooring ball would similarly fail under extreme load. (Steve Smith) writes: Hi all Having looked at Chapman's 'Piloting, Seamanship and Small Boat Handling' (now available in your local library for UK readers), I was a bit surprised to see recommended that a mooring-type buoy be used rather than attaching some other flotation to the intact anchor chain (one more link to go wrong). I think Hinz discusses this in his books but I haven't managed to get hold of any in the UK. I know this method of anchoring is for extreme conditions but has anyone any experience with it or the alternative method of using weights slid down the rode. I would guess there is a better argument for avoiding shock loading than there is for anchor dragging and that the buoy method is better at doing this. I am assuming all chain here due to chafe resistance. Regards Steve Remove defcv if etc. -- |
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#4
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#5
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"Rodney Myrvaagnes" wrote in message
... Kellets increase effective scope. Buoys decrease it. Yes, that's the key. Kellets are only really useful when you can't put out enough scope. Most anchors are optimized for an upward pull at 8 to 12 degrees, so they shouldn't pull out if the scope is 7 to 1 or better, especially if the there's a healthy bit of chain. The other interesting property of a kellet is that boats that horse around an anchor may be quieter if a kellet is lowered down so that it rests on the bottom. This approximates a hammerlock setup, which is a small anchor on very short scope added to keep the bow stable. When I had a Nonsuch I kept a dinghy anchor for that purpose. And while a kellet may provide some shock absorbing in a limited scope, moderate wind situation, it gives little advantage if longer scope is used. (And I'm sure we all know by now, a caternary, as the term is used in anchoring, has virtually no shock absorbing quality.) Also, the OP mentioned it in terms of an all chain rode, but I've almost always heard of it used with a mixed chain/rope rode. A buoyed anchor rode is used by fishing boats anchoring in a large sea - I'm not sure its relevant to cruising boats. I suppose it might be handy in an area of coral heads to keep the scope small in lighter air. |
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#6
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Marc Auslander wrote:
I have read, and it seems plausible, that in bad enough conditions, a kellet does no good because it can't really deflect the rode very much. And it may cause trouble if it starts to bounce up and down - pulling up on the rode on the upswings. I would think a mooring ball would similarly fail under extreme load. Strange how similar in effect kellet and float are, and how different. The ball sinks, deflecting the snubbing chain / painter junction to a degree adjustable at the painter end. Once it floats, it implies that mooring forces are minimalised. Any tangle occurs at the surface. A kellet can only effect snubbing to one degree, unless it slides and is adjustable. Once it rests on the bottom, it implies that the mooring forces are minimalised. There is also a tangle possible, at the bottom. A longer float painter can produce a larger and more gentle anti-snubbing force in either analysis. Under the most demanding conditions, both a kellet and a float with a long painter totalling sufficient scope are best, wether at anchor or mooring weight. A strong nylon painter is preferrable to a light floating painter, except if the tide and wind conspire, until the floating painter is wound around the keel root. That is probably easier to clean up than is a tangle on the bottom. Perhaps a cart before the horse? A float with a long painter and a kellet on the painter between the float and the boat? Perhaps a daisy chain of floats with kellets suspended barely above the bottom? Perhaps even a clothesline or string, with which to bring the moored boat's stern within wading distance of the shore, or floating dock out to the boat? (I draw 2'-10".) I presently can draw the dinghy out to the mooring using a messenger cable instead of oars, but the dinghy is too small for that to be really convenient. Cable ferries are common out here. We do get some medium sized wakes. This ties in with a desire to provide isolated bifilar hydro to my moored boat, perhaps via a mooring raft made of tires on wheels? That would require a swivel above the float and a strong stainless steel messenger wire to the shore, such as I presently use to retrieve the sunken mooring chain after the ice goes out. A two wire extension cord, isolated, in fresh water, may work out well. How much current would you expect a similar circuit to draw if the outlet was dropped in salt water? How dangerous would you expect such a mishap to be? I get a feeling that might not be a bad plan, and see that there may be no tangle, despite wind and tide conspiracies, except I cannot really trust what such a daisy chain might do under Murphy's influence. I'm gonna give it a try. Any experiences? Any bets? Perhaps pennant is a better word? Terry K (Steve Smith) writes: Hi all Having looked at Chapman's 'Piloting, Seamanship and Small Boat Handling' (now available in your local library for UK readers), I was a bit surprised to see recommended that a mooring-type buoy be used rather than attaching some other flotation to the intact anchor chain (one more link to go wrong). I think Hinz discusses this in his books but I haven't managed to get hold of any in the UK. I know this method of anchoring is for extreme conditions but has anyone any experience with it or the alternative method of using weights slid down the rode. I would guess there is a better argument for avoiding shock loading than there is for anchor dragging and that the buoy method is better at doing this. I am assuming all chain here due to chafe resistance. Regards Steve Remove defcv if etc. |
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#7
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Actually neither the ball no the kellet has any effect in extreme
conditions. Nor is chain desirable under such coditions. The problems is that above 35 knots of wind or so you have a straight rode. Neither kellet nor ball makes any difference...its straight. At that point nylon is a lot better than chain because of its elasticity. A long nylon rode keeps the anchor from tearing your boat up as a chain rode can do. The downside of course is you really need to maintain a nylon rode under such conditions...rigging chaff protection or letting out small increments to minimize chaff. Hinz deals with all this in his books. Jim Donohue "Steve Smith" wrote in message om... Hi all Having looked at Chapman's 'Piloting, Seamanship and Small Boat Handling' (now available in your local library for UK readers), I was a bit surprised to see recommended that a mooring-type buoy be used rather than attaching some other flotation to the intact anchor chain (one more link to go wrong). I think Hinz discusses this in his books but I haven't managed to get hold of any in the UK. I know this method of anchoring is for extreme conditions but has anyone any experience with it or the alternative method of using weights slid down the rode. I would guess there is a better argument for avoiding shock loading than there is for anchor dragging and that the buoy method is better at doing this. I am assuming all chain here due to chafe resistance. Regards Steve Remove defcv if etc. |
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#8
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"Jim Donohue" wrote in message news:X2Uid.82404$bk1.80735@fed1read05...
The problems is that above 35 knots of wind or so you have a straight rode. Uhm, maybe for your boat. In fact, just last weekend I was anchored out in 30 gusting 45 and neither chain+rope rode was bar-taut. On the other hand, I was wishing I had a bit more chain on both because I didn't have quite enough out for the weather (7:1 on a 7.5kg Bruce, and 5:1 on a 25lb. CQR) as I'd anchored 8 hours before the peak of the blow. To get a reasonable amount of shock absorption with all-chain, use a chain hook on about 30-40' of light nylon laid line and veer out a few more feet of chain. You'll get all the spring you want, but if there's much fetch you don't want too slack a chain to save your bows from a beating. I've never used either a kellet or buoy, but I'd like to experiment with both. Who has used which? Amgine http://wiki.saewyc.net/ |
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#9
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Uhm, maybe for your boat. In fact, just last weekend I was anchored
out in 30 gusting 45 and neither chain+rope rode was bar-taut. The point still holds, in heavy weather conditions, when things are at their worst, an all chain rode or a chain/rope rode will be stretched taut and a kettle will do no good. Paul "Amgine" wrote in message om... "Jim Donohue" wrote in message news:X2Uid.82404$bk1.80735@fed1read05... The problems is that above 35 knots of wind or so you have a straight rode. Uhm, maybe for your boat. In fact, just last weekend I was anchored out in 30 gusting 45 and neither chain+rope rode was bar-taut. On the other hand, I was wishing I had a bit more chain on both because I didn't have quite enough out for the weather (7:1 on a 7.5kg Bruce, and 5:1 on a 25lb. CQR) as I'd anchored 8 hours before the peak of the blow. To get a reasonable amount of shock absorption with all-chain, use a chain hook on about 30-40' of light nylon laid line and veer out a few more feet of chain. You'll get all the spring you want, but if there's much fetch you don't want too slack a chain to save your bows from a beating. I've never used either a kellet or buoy, but I'd like to experiment with both. Who has used which? Amgine http://wiki.saewyc.net/ |
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#10
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"Amgine" wrote in message om... "Jim Donohue" wrote in message news:X2Uid.82404$bk1.80735@fed1read05... The problems is that above 35 knots of wind or so you have a straight rode. Uhm, maybe for your boat. In fact, just last weekend I was anchored out in 30 gusting 45 and neither chain+rope rode was bar-taut. On the other hand, I was wishing I had a bit more chain on both because I didn't have quite enough out for the weather (7:1 on a 7.5kg Bruce, and 5:1 on a 25lb. CQR) as I'd anchored 8 hours before the peak of the blow. To get a reasonable amount of shock absorption with all-chain, use a chain hook on about 30-40' of light nylon laid line and veer out a few more feet of chain. You'll get all the spring you want, but if there's much fetch you don't want too slack a chain to save your bows from a beating. I've never used either a kellet or buoy, but I'd like to experiment with both. Who has used which? Amgine http://wiki.saewyc.net/ See Complete Book of Anchoring and Mooring by Hinz page 113. On the ABYC hypothetical power boat of 45 feet and 15 foot beam the cantenary has 1 foot of "droop"per 100 feet of rode at 30 knots and 0 feet at 40 knots. If your boat is smaller and has a smaller section it may be a little higher. Hinz advocates the use of chain riding stoppers for all chain boats. He points out that all chain rodes are very good at parting or destroying something in high winds. They are also sufficiently noisey in high wind conditions to make sleep difficult. Jim Donohue |
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