One of the reasons for the heavy chain is because here in the PNW we have some really deep anchorages. The extra weight increases the centenary which provides more shock absorbing affect to the anchor.
Chain splice
- Thread starter Hayden Watson
- Start date
["One of the reasons for the heavy chain is because here in the PNW we have some really deep anchorages. The extra weight increases the centenary which provides more shock absorbing affect to the anchor."]
I love Google speak to print, but to find myself often embarrassed using it to make technical arguments when the spelling is a bit off because it seems to happen to me so often.
I love Google speak to print, but to find myself often embarrassed using it to make technical arguments when the spelling is a bit off because it seems to happen to me so often.
Numbers might help. If it is really deep, you may have enough weight over with 1/4". The problem with light chain and rope is really more one of swing circle, which I think must be what you are getting at, since the math is really more about total pounds than pounds per foot. I sail the Chesapeake, and anchorages where you must anchor in more than 10 feet are very few. I could goo whole years without deploying 100 feet of chain (1/4" on a 34' cat). No need.
It depends on the gypsy, but I prefer not to give the windless anything to jam or slip on. Best of luck!
I believe that chain splices using 1/2" anchor line would significantly reduce the overall strength of your ground tackle. According to Jimmy Green, 1/2" anchor line is undersized (downsized) when used with 5/16" G43 chain to start with. Mix in 2 splices with up to 30% less strength (your words) then the line itself does not do justice to your 35lb Mantus. The "weak link" IMHO is your anchor line.
According to Practical Sailor: "To match the strength of the new chain (G43 or G70) we need a much larger-diameter rope, and this has proven too bulky to feed though some windlass gypsies. So, at least in the case of G43, we find ourselves returning to the 19th-century solution: the two-strand, long chain splice."
So ideally your 5/16" chain would be matched with 3/4" line and a 2 strand long chain splice or at a minimum 5/8" with a traditional 3 strand backsplice.
References:
Jimmy Green - Anchor Chain and Rope Size Guide
Practical Sailor - Rope-to-Chain Splice Test
According to Practical Sailor: "To match the strength of the new chain (G43 or G70) we need a much larger-diameter rope, and this has proven too bulky to feed though some windlass gypsies. So, at least in the case of G43, we find ourselves returning to the 19th-century solution: the two-strand, long chain splice."
So ideally your 5/16" chain would be matched with 3/4" line and a 2 strand long chain splice or at a minimum 5/8" with a traditional 3 strand backsplice.
References:
Jimmy Green - Anchor Chain and Rope Size Guide
Practical Sailor - Rope-to-Chain Splice Test
If I anchor at high tide in a spot showing a depth of 10' on the sounder, the boat could be laying on its side as much as 10' above the water level at low tide because at my harbor, we have a tidal range from -4' to +16'. My minimum anchorage depth is a charted depth of 10' which gives me at least 5' under the keel. Then you add on 15' of tide and I am in 25' for a minimum. It is not uncommon to need to anchor in 40' or more in order to ovoid shallow places within the swing room because the one thing about the PNW is that nothing is flat and there are lots of rock outcrops.
At extream anchoring depths, the 5:1 or 7:1 rules do not really apply if you are using enough chain. The catenary affect means that the weight of the chain will make the pull on the anchor be at a much more horizontal angle that what you get with shorter lengths of chain out. It also makes a big difference in the shock loads on the anchor because as the loads increase in a gust, much of the energy is put into straightening the centenary form the chain so that the max pull does not end of being transferred to the anchor.
Here is an article on deep anchoring with all chain.
I are an Engineer which by default means that language and especially spelling are not my thing.
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,503
Maybe I am being too simplistic. I'll take the critique.
If I use 100 feet of chain, attach a 30-foot nylon snubber, and have a target scope of 5:1, I can anchor in water 22 feet deep at high tide. With a keel depth of 5 feet, I'm good (1 foot of water between keel and sea bed) up to a tidal change of 16 feet. I am good even during King tidal periods in most anchorages around the Salish Sea.
If I use 100 feet of chain, attach a 30-foot nylon snubber, and have a target scope of 5:1, I can anchor in water 22 feet deep at high tide. With a keel depth of 5 feet, I'm good (1 foot of water between keel and sea bed) up to a tidal change of 16 feet. I am good even during King tidal periods in most anchorages around the Salish Sea.
"BBB is unnecessarily heavy" It has always been my belief that weight over strength was the point of anchor chain. Catenary curve and all that.
Quite simply, you are never going to realistically carry any anchor chain that is strong enough to hold your boat, once the chain is tight between the anchor and boat. The catenary curve is what one wants to use as a "shock absorber" in the system.
However, the catenary curve doesn't always do the job. I use a snub line, a 15' to 30' nylon three strand line hooked into my chain and secured to a cleat is what I use as a shock absorber. When you have the proper snub line, or a combination of chain & line, the strength of the chain is no longer of importance.
Case in point, though this usually happens @ 3am. Pics show Rodney Bay in a WSW wind but an hour or so earlier it was calm and the wind from the East.
At the point in which any additional weight difference between BBB and G43 could possibly make a practical difference in catenary, it won't matter at all. It is the reason kellets don't work. Shock loads should be handled by a bridle/snubber - catenary will never mitigate shock loads.
Mark
Agreed. The math in deep water and shallow water are completely different, with a continuum in the middle. In shallow water, catenary means little and nylon is your friend. In deep water catenary it is everything, reducing the need for crazy long rodes, swing there isn't room for, and snagging.
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If discussing catenary in chain rode, yes,
But kellets have another purpose: in reversing currents they can keep the rode from fouling the keel.
Continuing this thought, Nautic Ed's recommendation for the amount of rode out is 2x depth plus 50' for all chain rode and 4x depth plus 50' for chain plus rope rode. I'm kinda warming up to the idea over my usual 4:1.
Explanation below:
Anchoring: How much rope or chain should I let out?
Anchoring and getting how much chain and rope right to let out is such an important topic that we thought we'd make this excerpt available for free in open space. Please enjoy how we dive into science and mathematics in these techniques.
sailing-blog.nauticed.org
excelent read and makes a ton of sense. I think this will be my new rule of thumb.Continuing this thought, Nautic Ed's recommendation for the amount of rode out is 2x depth plus 50' for all chain rode and 4x depth plus 50' for chain plus rope rode. I'm kinda warming up to the idea over my usual 4:1.
Explanation below:
Anchoring: How much rope or chain should I let out?
Anchoring and getting how much chain and rope right to let out is such an important topic that we thought we'd make this excerpt available for free in open space. Please enjoy how we dive into science and mathematics in these techniques.
I have snagged my nylon rode twice in the past couple of years and it is a real bugger to get free if youhave any current. The last time was at Cornet Bay just inside Deception pass and there was a 6kt current in the pass. I was on the outskirts of the anchorage and had at least a couple of knots of current and there was nothing I could to to clear the keel. I ended up waiting for slack and then the rode just dropped away as if to say, "now you may leave".
Kellets. Better to understand what they are and thus their limitations.
- They can help a mostly rope rode swing more in sync with all-chain rode in light winds. Once the chain or kellet starts to lift they should be roughly in sync anyway.
- They weigh maybe 15 pounds. The difference in weight of 100' of 5/16" BBB and 1/4" G43 is about 33 pounds. No, obviously it won't do as much as heavier chain. More to the point, letting out about 15 feet more 1/4" chain adds scope, nearly as much weight, and is simpler. Skip the kellet for that purpose and let out 10 feet of chain.
In 6 knots current a kellet would be totally ineffective at preventing a keel wrap, even with heavy chain. It’s all a matter of degree. Lighter wind and current, yes. If a strong wind wants to point the boat one way and current opposes, at some point the equilibrium between water resistance and air resistance will change and that point is usually a dynamic constantly changing thing. I’ve been anchored or moored in several situations where my boat and others around were literally spinning, even while the rode was pulling tight.
Being aboard in the black of a moonless night while the chain is pulling aft alternately grinding against the keel, letting go with a boom that shakes the boat, then grinding again is very unnerving, and I was afraid to start the engine for fear of involving the props.
I didn’t have a drogue aboard (do now) and a bucket was not effective. Then it raises the question of whether it would have been smart to deploy a drogue - as it may add enough drag to cause anchor dragging (in strong currents and pitch black with nearby shoals and anchored boats).
jssailem
SBO Weather and Forecasting Forum Jim & John
- Oct 22, 2014
- 22,503
Back to the original question - joining two pieces of chain.
I have done it in the past with a rope splice. It was about a 3 foot segment.
My reasoning for this was that it is easy to inspect and if needed, repair on the water.
I also knew it would work fine with the windlass since it was a chain+nylon rode already.
This was 5/16" G4 chain and 5/8" nylon.
My only concern was the possibility of chafe, like it getting sawed through in heavy weather, but I am in the Pacific Northwest so no coral heads here anyway.
It worked just fine this way, and I as I mentioned, it is easy to inspect regularly just as part of deploying/retrieving the anchor.
I have done it in the past with a rope splice. It was about a 3 foot segment.
My reasoning for this was that it is easy to inspect and if needed, repair on the water.
I also knew it would work fine with the windlass since it was a chain+nylon rode already.
This was 5/16" G4 chain and 5/8" nylon.
My only concern was the possibility of chafe, like it getting sawed through in heavy weather, but I am in the Pacific Northwest so no coral heads here anyway.
It worked just fine this way, and I as I mentioned, it is easy to inspect regularly just as part of deploying/retrieving the anchor.
Yep!Some nights, you are just not meant to get any sleep.
And with 2 hulls it was made even more crazy - it would grind on one keel then slide free (with a loud boom resonating through the hull) then catch/grind on the other hull and we’d spin and repeat. I had a mental image of the anchor chain sawing off flakes of fiberglass in the water. A later underwater inspection showed no damage. It sounded a lot worse than it was.This was Fort Pierce Inlet (near the Active Captain mark named “North Anchorage”). The top ranked review in AC reads “Anchorages like this will have you calling your yacht broker, and mommy.”.
Edit - we were back there last year for a second time on our return from the Bahamas and decided to open the wallet for a marina slip rather than anchor there again.
Another edit - if anyone cruises through there it’s a beautiful nature preserve on the north side of the inlet. It would be nice to dinghy through the wetlands and maybe go for a paddle through the wetlands if you have a kayak to take in towed by the dinghy. However, due to the strong currents this isn’t a good place for underpowered dinghies.
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