Anchoring 32' Sloop

[Jim Cate]

The beauty of forums is that you don't have to reinvent the wheel.

True, but you do have to make your own decision about whether the three, four or five sided wheel is best to replace your old round one, or if the expert who recommends leaving the wheels off to lighten things is in fact correct!

Jim

[rgleason]

Originally Posted by rslifkin

I personally ignore the anchor manufacturer's chain sizing recommendations. They suggest my 73 lb Vulcan should use 3/8" G43 instead of the 5/16" I'm actually using. Basically, they're sizing the chain based on best case holding power of the anchor, rather than the real-world loads the boat in question can apply to the anchor at the wind speeds you're using for a sizing basis (which will typically be less than best case holding loads, as you're sizing for the less than optimal holding scenarios).

Thanks rslifkin. I guess I am going to get:

• 30' x 1/4" G43 (.73lb/ft, 21.9 lb)
• 300' x 9/16" NER 8-Plait (7.2 lb/100ft, 21.6 lbs)
• Keep the existing Bruce 22 for a year.
• Get a Vulcan 15kg next year

The new anchor and ground tackle will be about 8.6 lbs more than present and will hopefully be a better system than we have now. I backed away from 80'-100' of 1/4" or 5/16" chain, as I found it does not do very much for us, the way we use the boat, and I have not experienced trouble with our current anchor and rode other than when foolishly anchoring at the eelgrass line.

I would like to thank everyone for their suggestions. If I did not land at the same place, it does not mean your contribution was not considered or invalid. I've learned quite a lot and run a number of trials with Bjarne and MathiasW calculators. I may have ended up with a 3 sided wheel, but I think it will be fine for our coastal use. When and if we go voyaging, I can always add 100' of chain.

[rslifkin]

Originally Posted by rgleason

Thanks rslifkin. I guess I am going to get:

• 30' x 1/4" G43 (.73lb/ft, 21.9 lb)
• 300' x 9/16" NER 8-Plait (7.2 lb/100ft, 21.6 lbs)
• Keep the existing Bruce 22 for a year.
• Get a Vulcan 15kg next year

The new anchor and ground tackle will be about 8.6 lbs more than present and will hopefully be a better system than we have now. I backed away from 80'-100' of 1/4" or 5/16" chain, as I found it does not do very much for us, the way we use the boat, and I have not experienced trouble with our current anchor and rode other than when foolishly anchoring at the eelgrass line.

I would like to thank everyone for their suggestions. If I did not land at the same place, it does not mean your contribution was not considered or invalid. I've learned quite a lot and run a number of trials with Bjarne and MathiasW calculators. I may have ended up with a 3 sided wheel, but I think it will be fine for our coastal use. When and if we go voyaging, I can always add 100' of chain.

That should do the trick. And as you pointed out, you can always add more chain later if you feel it's needed.

I took the same cautious approach to chain quantity (also due to bow weight concerns). Currently we're carrying 90 feet of chain and 300 of line. At some point when either something needs replacement and/or our cruising grounds expand, I'll likely to go 150 or 200 feet of chain (and enough line to make 400 total).

[rgleason]

BTW responding to Jim Cate's post

Yes will use thimble and shackle.
I found that our typical anchoring depths will not benefit much from long chain, which is Mathias Wagner's point, and why it was initially only a chain calculator.

Thank you for the Mathias Wagner suggestion.

I found his AnchorChainCalculator and learned from him a technique to compute loads with chain and rope ground tackle, which proved to be useful. Hopefully he will add this feature to his app. Then later I found Alain Fraysee's spreadsheets and BjorneK's online calculator. These both handle rope-chain rodes and are very useful for different things.

BjorneK's calculator has an excellent data entry system, allows kellets and floats, stores multiple results in a given session, and shows comparative graphics.

Alain Fraysee's calculator is more detailed with regard to snubbers and offers predictive graphical results for the dynamic loads.

All of these calculators are trying to model real world conditions and loads with mathematics. However there are still some unknowns and difficulty establishing the dynamic loads that one can expect.


There are links and examples below.

[rgleason]

Had to go up to 5/16" acco G43 chain so that a 7/16" shackle pin would just fit inside link width and have a chance of accepting a 1/2" thimble. I hope it works . Chain is 11 lbs heavier.

[rgleason]

Found remnant 210' x 9/16" 8-brait at Defender for $75. Got home and ran some calcs using http://www.svamanda.dk/anchor/intro

and learned that the WLL was not high enough, such that at 40 knots the loads exceed 20% of WLL thus causing perminent stretch

I went back to Defender and found 5/8" x 185' 8-brait for the same price which has 11,000 WLL. The manager said it was not cut goods so I could exchange them.

The Titan 7/16" shackle does work .5" dia. pin dia into 5/16" x 30' chain (increased chain size due to finding a shackle that would work) and this shackle does passes into the thimble.

[thinwater]

Originally Posted by rgleason

Had to go up to 5/16" acco G43 chain so that a 7/16" shackle pin would just fit inside link width and have a chance of accepting a 1/2" thimble. I hope it works . Chain is 11 lbs heavier.

Actually, you did not. Splice the rope to the chain, just as easy, fewer parts to fail. And are you certain a 1/2-thimble won't slide into a 1/4-inch anchor shackle? It helps to splice it in place.

[thinwater]

Originally Posted by rgleason

Found remnant 210' x 9/16" 8-brait at Defender for $75. Got home and ran some calcs using http://www.svamanda.dk/anchor/intro

and learned that the WLL was not high enough, such that at 40 knots the loads exceed 20% of WLL thus causing perminent stretch

I went back to Defender and found 5/8" x 185' 8-brait for the same price which has 11,000 WLL. The manager said it was not cut goods so I could exchange them.

The Titan 7/16" shackle does work .5" dia. pin dia into 5/16" x 30' chain (increased chain size due to finding a shackle that would work) and this shackle does passes into the thimble.

Nope. Perhaps you used the ABYC table as though those are loads, or made some minor error on a load calculator. I used your link and got 325-350 pounds for your boat at 40 knots, which squares with my instrumented testing experience. ABYC H-40 table 1 is a design basis, not an estimate of tension. The actual load, with a rope rode, is typically about 3-4 times less.

1/2-inch rope is enough and is normal for that size boat. That said, larger rope is easier to handle. But you are overbuilding this. Just sayin'.



Welcome to the paranoid nature of internet anchoring forums! Take a very conservative standard (ABYC H-40 includes a proven safety factor), add a bit because you want to be safe, and then double it.

[rgleason]

Thinwater, you did not look at the %WLL for 1/2" rope at 40 kn as shown in svamanda calculator, but it is over 20%.

Sure the 9/16" x 210" would have worked, but I wanted a line that was not quite so stretchy too.

Yes. I certainly could have gotten 1/4" G43 Acco and done a direct splice, but I believe this alternative is better and I don't have a windlass. The 1/4" would have been fine for loads and been lighter which was a goal, but I would have needed two shackles and one of them would have been too weak, or I would have needed to do a direct splice to chain.

Going with 5/16" chain adds 11lbs total, will improve anchoring, and allows me to use one shackle without having to use a direct splice which would need to be redone on a regular basis, and is definitely substantially weaker because the rope fibers wrap around a much smaller chain wire diameter than a thimble.

So contrary to your "opinion" , I made the choices I felt were appropriate.
I do agree the rode is a little heavier than I finally decided upon.

Finally. what was your setting for the effect of wave surge, veering, and wind gusts on the hull? I believe mine was intentionally set higher based on some good advice from Markus.

At this point, I feel good about these choices, some anchoring this summer will reveal more. The boat displacement is in the middle of two sets of choices.

I am advised 8-brait does absorb more water, may hold more mud and may snag sometimes, but coils easily.
I usually, leave the rope on deck tied down to let it dry before stowing in the forepeak. We will see how long that takes. I had not considered the
Idea that 5/8" might be easier to haul in since I am used to 1/2" 3 strand for the last 33 years.

[rgleason]

PS I errored, the 5/8" 8-brait break strengnth 11,000 lbs and WLL is 2200 lbs (20%).

[rgleason]

Also the other reason for using 5/8" is so that a 3/8" snubber can be used to adjust the amount of stretch.

With a longer rope rode (+ 30' chain), needed with higher winds, I had a concern that the amount of stretch might be too much (causing veering, for example), while the longer scope is needed to keep the anchor angle down, excessive stretch might become an issue. Having a slightly oversized rope rode, to reduce stretch somewhat and then being able to make smaller adjustments by adding stretch with an appropriate snubber, is my strategy.

I consider using polyester rope, but its elasticity is about 1/2 of nylon, although it does not loose 15% of strength when wet like nylon!

[rslifkin]

Originally Posted by rgleason

Also the other reason for using 5/8" is so that a 3/8" snubber can be used to adjust the amount of stretch.

With a longer rope rode (+ 30' chain), needed with higher winds, I had a concern that the amount of stretch might be too much (causing veering, for example), while the longer scope is needed to keep the anchor angle down, excessive stretch might become an issue. Having a slightly oversized rope rode, to reduce stretch somewhat and then being able to make smaller adjustments by adding stretch with an appropriate snubber, is my strategy.

I consider using polyester rope, but its elasticity is about 1/2 of nylon, although it does not loose 15% of strength when wet like nylon!

I've debated going to polyester and just using a snubber all the time. I've got 5/16 chain spliced to 5/8 8 plait currently. When time comes to replace, it's a debate between 3/4 8 plait (officially not supported by my windlass but should work except maybe being hard to get the splice through) or 5/8 polyester.

[Uncle Bob]

Originally Posted by thinwater

Nope. Perhaps you used the ABYC table as though those are loads, or made some minor error on a load calculator. I used your link and got 325-350 pounds for your boat at 40 knots, which squares with my instrumented testing experience. ABYC H-40 table 1 is a design basis, not an estimate of tension. The actual load, with a rope rode, is typically about 3-4 times less.

1/2-inch rope is enough and is normal for that size boat. That said, larger rope is easier to handle. But you are overbuilding this. Just sayin'.



Welcome to the paranoid nature of internet anchoring forums! Take a very conservative standard (ABYC H-40 includes a proven safety factor), add a bit because you want to be safe, and then double it.

Mate, come-on, fess up, where did you find the mini coke can?

[rgleason]

Well, I got the word. My sweetheart when consulted, instantly said thats too big, how heavy is all that?
Still at 40kn the 5/8" WLL% is around 20% and 9/16" is close to 30%.

So maybe I should just accept the line will degrade when used above about 35kn and try to go back to the 9/16" line. We haven't anchored in over 30kns more than once or twice.

Thanks rsliftkin and thinwater for the perspective.

But dont know what to do about excessive stretch on long rope rode, if it happens. Put out a dynema snubber of the right length?

[thinwater]

Originally Posted by rgleason

Thinwater, you did not look at the %WLL for 1/2" rope at 40 kn as shown in svamanda calculator, but it is over 20%.

Sure the 9/16" x 210" would have worked, but I wanted a line that was not quite so stretchy too.

Yes. I certainly could have gotten 1/4" G43 Acco and done a direct splice, but I believe this alternative is better and I don't have a windlass. The 1/4" would have been fine for loads and been lighter which was a goal, but I would have needed two shackles and one of them would have been too weak, or I would have needed to do a direct splice to chain.

Going with 5/16" chain adds 11lbs total, will improve anchoring, and allows me to use one shackle without having to use a direct splice which would need to be redone on a regular basis, and is definitely substantially weaker because the rope fibers wrap around a much smaller chain wire diameter than a thimble.

So contrary to your "opinion" , I made the choices I felt were appropriate.
I do agree the rode is a little heavier than I finally decided upon.

Finally. what was your setting for the effect of wave surge, veering, and wind gusts on the hull? I believe mine was intentionally set higher based on some good advice from Markus.

At this point, I feel good about these choices, some anchoring this summer will reveal more. The boat displacement is in the middle of two sets of choices.

I am advised 8-brait does absorb more water, may hold more mud and may snag sometimes, but coils easily.
I usually, leave the rope on deck tied down to let it dry before stowing in the forepeak. We will see how long that takes. I had not considered the
Idea that 5/8" might be easier to haul in since I am used to 1/2" 3 strand for the last 33 years.

Not opinion. I gave you facts based on code and testing.

I did not say you had to splice to chain. I said you did not have to use a thimble. That is different.

No, one of the shackles would not have to be too weak. You use a load-rated high test shackle. That is how it high test chain is mated to an anchor. You can search the topic.

The rode tension at 40 knots does not exceed 500 pounds with your boat. You entered an incorrect number, or something along those lines. I've done a lot of testing, in exposed locations, using load cells. I went to your link and got about 350 pounds. You must have mixed up units or entered a rode length/scope combination that did not make sense (caused snatching) The breaking strength of 1/2-inch nylon is about 9500-10,000 pounds and the WLL about 2000 pounds if you use 20%. So just facts.

You are incorrect in assuming a rope-to-chain splice is weaker than using a thimble. Google it. Instead of a 1/2-rope going around a link, there are 3 separated 1/4-inch strands going around the link. Second, there are 6 stands carrying the load, not 3 (think like a block and tackle), meaning each strand only needs to carry 1/2 its share, and the strand is only weakened about 1/2 by the bend. Study the topic and you will learn that this has been tested and that it is full strength. Why else would EVERY windlass manufacturer recommend it? So its acceptability in this service is a fact. This is a common misunderstanding.

Yes, it would need respliced every 5 years. On the other hand, the end of the rope should be renewed every few years anyway (standard practice), so this is a non-issue. You will resplice it once, possibly replacing the shackle, and then replace the rode. If you splice eyes in the ends, then you still have two splices. Same difference. This gets into the realm of opinion, but I think many opt for a thimble because either a) they don't understand that the strength is the same or b) they can buy a rode with the thimble pre-spliced, since they are not sure they know how to splice to chain. But one less thing to catch on your hand or when the rode comes over the roller, and one less thing to fail (no shackle).



A less stretchy line is a good reason. I've done testing that suggests minimum size nylon gives an excessive sling-shot in some circumstances. The nylon rode on my F-24 is slightly oversized for that reason, and for ease of handling. I also use very little chain on that boat (weight).



You do not need a fat rope so that you can put a snubber on it. a) You don't need a snubber on rope. Just make sure you deploy at least 25 feet of the rope. But you may want to for chafe or to add a bridle. b) You attach the snubber with a Dyneema climbing sling or similar. Been doing this for 20 years with bridles. Use a prusik hitch and a carabiner. Very fast and more secure than a rolling hitch. Will hold far beyond your working load on ropes as small as 10 mm (lots of testing related to climbing). But 3/8-inch is a good snubber size for that boat.

The ABYC standard is based on 40 years of experience and includes safety factors for everything you can think of. Certainly, you are free to go stronger, but that won't be based on calculations, just your feeling, which is fine.

Guess you didn't like that picture. Sorry, that was just for fun. It's a fun picture.

---

An opinion? I would add a windlass, and use 120-150' 1/4-inch G43 chain rode backed with 1/2-inch for special occasions, with a snubber when anchoring on all-chain, which would be 98% of the time. No risk of cutting on coral, plenty strong, and much easier to manage in a blow. For an anchor, there are many fine choices around 35 pounds and I' not getting into that. Yes, this would cost a few $$, but well worth it if you are cruising far, which your initial post suggests you are. I've had boats with and without a windlass, and a windlass is much easier and safer. But that is an opinion.



And excessive use of quotes is ... tiresome.