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
- 22,486
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.