Perspective on Chain Length Vs. Sailing Performance

[noelex 77]

Originally Posted by Ziggy

Once in St. John river, the tidal range is virtually nil, and the bottom is all mud so no danger of chafe.

On small or lightweight boats using a combination of chain and rope is the only practical option, but it is important to realise that if rope is on the bottom there is always a slight risk of chafe cutting the rode.

I have dived in many anchorages and even in relatively deserted spots it is amazing the amount of debris that is on the bottom. Unfortunately much of it man made junk. There are also isolated patches of rock on the bottom of many sand and mud anchorages.

If the rode is cut, the boat will move very rapidly without the drag of any anchor or chain. There is less time to remedy the situation and if the boat hits anything the higher speed will cause more damage, so while the risk may be low the consequences can be serious.

[MathiasW]

When you are using a mix of rope and chain, and provided the chain is shorter than the rope, then most of the shock load absorption is done by the rope and not the chain. In this scenario the chain is effectively in its 'shallow water mode'. Its only function is to reduce the pulling angle at the anchor shaft (and thereby prevent a degradation of the maximal holding power of the anchor) and help raise the rope off the seabed to prevent chafing.

Thus, as long as those two points are satisfied, adding more chain will make very little difference indeed.

Cheers, Mathias

PS: I am currently working on allowing a mix of rope and chain for my anchor chain calculator app. Quite involved to catch all corner cases, but I am slowly getting there.

Anchor Chain Calculator

[goboatingnow]

I carry 60 metres of all chain on the Bav 36. But if anything she’s stern heavy. I’m upgrading to 80 m this summer

[epoxyman]

MiathiasW,
A very interesting response regarding the chain / rope rode correlation and the app is very cool as well.
There has been a lot of discussion around how long a snubber should be and how much chain to use as the catenary (loop of chain between boat and snubber link), do you have any thoughts, suggestions, rules of thumb.
Clearly with your app on Anchor calculations, this is an area that you have considerable knowledge about. I would love your perspective.
Thanks again.

[Pete the Cat]

Originally Posted by Chotu

I think you and your friend are splitting hairs. The extra 45 pounds isn’t going to kill the boat, nor do you need the extra 30 feet of chain rode.

Neither is a big deal.

As long as you have enough of that three strand to anchor in the depths you want to anchor in, you are good to go. 30 feet of chain is not going to change anything.

I agree. I live in Maine and have cruised the coast there for the last 30 years. You need that 90 of chain because of the gravel and rocks in many anchorages, and 90 feet is probably the minimum for a boat your size, but the difference between your choices is inconsequential. Make sure you are able to use your radar well. There are passages in Maine where you must be able to navigate in close quarters in morning fog. Some of the best cruising grounds in the world.

[Atcowboy]

Originally Posted by Ziggy

Almost all harbors along your planned cruise have mud bottoms, so 90 ft of chain should suffice. However, the tidal range of up to 30 feet means that you will want to have at least 300 feet of rode to allow for adequate scope in stronger winds. More would be better.

Once in St. John river, the tidal range is virtually nil, and the bottom is all mud so no danger of chafe. The greatest hazard is the nasty big flies that drove me nuts when I was there.

I agree that the extra 45 lbs of weight on the bow won't make any significant difference.

This was my reaction reading The OP's ground tackle specs. Just not enough length.

I used to think I wanted 100% chain and a snubber. I went with 50/250 feet because that's what I could afford. I would tell past self to get about 100' more rope. After a year, I would like to cull the first 25' of line. But I don't like the idea of only having 275' of rode total. I could flip the line, but then when I get to that bitter 25' I REALLY am in need of that rode doing it's job.

It's worked really well, and having that much rope really takes all the snap out of the waves when I start chucking rode out. This is on a 27' boat, and I'm not advising to go less than 90' of chain either, and I haven't cruised in Maine (yet). Also, only through stories, but your anchor is a part of your navigational safety gear. You might need to anchor in 90' or more some day off a lee shore to take care of some pressing need. Your current gear would be 2.6:1.

- AT

[Chotu]

Originally Posted by Pete the Cat

I agree. I live in Maine and have cruised the coast there for the last 30 years. You need that 90 of chain because of the gravel and rocks in many anchorages, and 90 feet is probably the minimum for a boat your size, but the difference between your choices is inconsequential. Make sure you are able to use your radar well. There are passages in Maine where you must be able to navigate in close quarters in morning fog. Some of the best cruising grounds in the world.

I started sailing in Maine. No radar. Pre-gps. No loran. You’re bringing back fond memories of a different type of navigation.

I used to make it through those rocky islands on foggy mornings with:

1) Paper charts
2) Dead reckoning using set and drift
3) my EARS. You could always hear the shoreline and the channel marker you were looking for. It was exhilarating and fun to navigate without sight, using ears to hear the shoreline, channel markers and other vessel traffic. The fog signals they emit or the sound of their engines.


It was an art. It was so much fun to pop out where you planned using only your ears and set and drift. The satisfaction of seeing the channel market or safe water marker were really something. Steering by compass too.

We were so much more in tune with the environment and reality back then.

[Atcowboy]

Originally Posted by Ziggy

Almost all harbors along your planned cruise have mud bottoms, so 90 ft of chain should suffice. However, the tidal range of up to 30 feet means that you will want to have at least 300 feet of rode to allow for adequate scope in stronger winds. More would be better.

Once in St. John river, the tidal range is virtually nil, and the bottom is all mud so no danger of chafe. The greatest hazard is the nasty big flies that drove me nuts when I was there.

I agree that the extra 45 lbs of weight on the bow won't make any significant difference.

Originally Posted by epoxyman

MiathiasW,
A very interesting response regarding the chain / rope rode correlation and the app is very cool as well.
There has been a lot of discussion around how long a snubber should be and how much chain to use as the catenary (loop of chain between boat and snubber link), do you have any thoughts, suggestions, rules of thumb.
Clearly with your app on Anchor calculations, this is an area that you have considerable knowledge about. I would love your perspective.
Thanks again.

There have been times when I wanted more snubber but less scope for tight anchorages in Florida. I attached a 1/2" 50' spring line to the fore cleat, ran it back along the deck to a huge frictionless turning block on my stern cleat (made for snatching stuck trucks) and then forward to a rolling hitch on my chain. Allows for short scope with lots of lovely 3 stand stretch. And not that it's ever really more than 10' of excess, but the chain behind the hitch always all goes overboard for more weight in play. Kind of like a kellet.

- AT

[EmeraldCoastSailor]

Might as well use the new and longer chain. It isn’t a big deal either way but more chain is better (within reason) if you have a windlass, IMHO.

[Rumrace]

THe anchor type size length of chain ride etc seems very regional.
As a scuba diver the guys with a pile of chain on an anchor don’t know how to lay an anchor and that’s about half. Fresh or salt water.

[GopherBaroque]

Getting back to the original question, I would pose:
a) When sailing, do you notice a change when a person (3 to 4 * 45 lb) moves to the bow?
b) Not being familiar with the area, how do anchor depths / tidal range at the destination compare to your current location? How much longer rode would you need to have the same scope that works well for you now?

[R Hutcheson]

Excessive weight at the ends will affect sailing performance, however 45 lbs as you point out is not much. You may want to consider adding 45 lbs of weight on deck above your chain locker at the dock, and just look at the boat. If she is still sitting level on her waterline, you are probably OK adding the extra weight. If it looks OK but your still concerned swap the rodes, it won't take long and go sailing on a day when the seas are up. If your happy with the performance you can make the change permanent.

[MathiasW]

Originally Posted by epoxyman

MiathiasW,
A very interesting response regarding the chain / rope rode correlation and the app is very cool as well.
There has been a lot of discussion around how long a snubber should be and how much chain to use as the catenary (loop of chain between boat and snubber link), do you have any thoughts, suggestions, rules of thumb.
Clearly with your app on Anchor calculations, this is an area that you have considerable knowledge about. I would love your perspective.
Thanks again.

Hi epoximan, thanks! Just arrived at new anchorage after a couple of days sailing in too little wind...

It all depends on the vessel, obviously, so rule of thumb answers are difficult.

But as to elasticity of the snubber - regardless of how small or large your vessel is, when your vessel pulls at the snubber at 8 Beaufort or something like that, so quite some wind, the snubber should stretch by much more than a metre, so at least 4 - 6 feet. If it does not, it will not absorb enough energy. More is better, obviously, but the additional gain will be smaller and smaller.

Now, this is not possible with the short 3 feet snubbers one too often sees. As a snubber can only stretch by perhaps 20%, if you want the stretch to be 5 feet, then this means that the original snubber needs to be 25 feet long at least. And obviously, it needs to be chosen such that at that wind it does stretch by that amount. So neither too thin nor too thick. You can work out the load given by your vessel using the anchorchaincalculator and then go the specifications of the rope vendor of your choice to see which diameter of rope would give you the required stretch.

I have a day snubber that is just 3 feet long, for when it is very calm and I just drop anchor for a few hours. I then have my every day bridle that is 14 feet long. And finally I have my heavy weather bridle of 45 feet length. It makes sense to use different bridles / snubbers for different scenarios. For one thing, my heavy weather bridle is then fit for when I need to use it, and not worn out by many months in moderate but high UV conditions.

Some folks like Jonathan Neeves have come up with clever designs to have part of the snubber run along the deck. This way your swinging circle is reduced, and less of the snubber will be dangling in the water and have all kind of things grow on it. Perhaps one day I will install something like that. But it requires some effort to avoid chafing and my set up at the bow is not ideal.

As to the mix of chain and rope - it will depend on the wind and swell load, how much you need. You do not want the rope to touch the seabed, so in lighter winds, you will want to pull in some of the rope, and pay out more when it blows harder. Unfortunately, no rule of thumb here that I know of. Perhaps I will find some over time, but for now I don't have it. Sorry.

Cheers, Mathias

[col50]

Originally Posted by GordMay

Indeed.

Or, go on a diet, lose 45 Lbs [to compensate], and add the extra chain & rope.

FWIW: I went on a whisky diet, 2 months ago; and I’ve already lost 10 days.
Finally, my winter fat is gone. Now, I have spring rolls.

Very funny.

[rgleason]

clever designs to have part of the snubber run along the deck. This way your swinging circle is reduced, and less of the snubber will be dangling in the water and have all kind of things grow on it.

It also keeps the nylon out of the water which causes a 15% reduction in strength.

Anchor and chain at the bow + Anchor and chain in the stern locker increases the opportunity to hobby horse. Some older boats have a short footprint (not much waterline length), these boats need be aware, but extra weight in the ends affects most boats to some extent.

If you have a lot of chain, it is best to have an arrangement where the chain will by gravity, land in a locker further aft, if at all possible.

As I understand it, snubbers need to be adjusted to respond to the wave patterns with the right amount of elasticity, this can reduce the loads on your anchor quite significantly, and reduce the anchor angle.

It is possible to have too much elasticity, which causes the boat to yaw back and forth, with acceleration and more force. Obviously this is to be avoided, but it takes a very significant amount of thinner line to reach this point.