Anchor rope size and suitable breaking strain

[Darren J]

Hi,
I am preparing to fit an anchor drum winch to a 22ft Glacier Bay cat. Boat weight is around 2.2-2.8t depending on load/fuel etc.

I was looking for options in 6mm preferably to maximise capacity and was considering 6mm double braided nylon. It has a claimed breaking strain of 950kg. That is comparable with 10mm silver rope.

Are there any guys out there with experience using the smaller breaking load ropes on this size boat and do you believe it would be ok?

Otherwise you move to 6mm dyneema, very high breaking strains around the 3t mark, BUT very expensive ($3-5/m) and not really worth it I don't think. I am hoping to run 200+m of rope.
I was considering running the first 20-50m or so in 8mm, (1250kg break strain) for increased strength against possible abrasion, and then dropping back to 6mm. Boat will also run around 8m of chain to protect from abrasion. I may do the odd overnighter out wide etc, but generally would always be on "watch" when anchored etc.


Is 950kg sufficient of this sort of use, or am I asking to loose anchors from broken ropes the first time one gets hooked up a bit???
Would be great to hear from guys with boats this size, using similar ropes.

Cheers.

[marto78]

I found this from Club Marine.

http://www.clubmarine.com.au/interne...22-2+Technical

I use 12mm nylon rope on a 5.1m but I would rather have to cut the rope then have it break when I'm not expecting it.

[Darren J]

I found this from Club Marine.

http://www.clubmarine.com.au/interne...22-2+Technical

I use 12mm nylon rope on a 5.1m but I would rather have to cut the rope then have it break when I'm not expecting it.

Thanks for the reply. I had seen that article, but it appears to be referring to anchoring in the worst case weather etc. I note it has 12mm nylon recommended for anything between 4.5 and 7.5m. That is a lot of difference in tern=ms of boat weight and possible wind load etc. It also suggests 8mm for 3.5m and under. That is a rope rated to over a ton for effectively a "car topper". I guess I was taking that report as very conservative, and for anchoring through all and any weather conditions etc.

I also note that the double braided nylons seem to be stronger than standard 3 strain, and then different manufacturers of 3 strand strengths seem to vary a bit also.

Out of interest I used 12mm on my 5m boat as well, easier on the hands with no winch...

[Crocodile]

Hello Darren J,

Some random thoughts;

The limiting factor is what load is required to bend the tines on the reef anchor.

Using double braid etc. is problematical because it has very little stretch, you may need to use a rubber snubber to reduce the jerking(of the anchor line that is!).

You still need some chain to lower the angle of the rode as it rises from the anchor.

On my tinny I use 6mm silver rope of unknown breaking strain, which easily straightens the anchor tines but is very hard in my delicate hands.

Also to consider, when you swap the reef pick for a sand anchor you need all the breaking strain that you can get.

[Darren Mc]

12mm silver rope with your 8m of chain would be the go I reckon. The rope has to have a decent amount of stretch to it and those other rope's you mentioned( especially the dyneema) may not have enough of it.
The stretch helps to hold bottom better and takes some stress off of your hardware on the bow. I know your trying to get 200 m plus on there but that may not quite fit. What does the drum say it's capacity is?
12 mm is pretty strong and that is what that club marine info recommends also.
It's the worst weather that you wan't the anchor to hold in after all isn't it?

[Darren J]

12mm silver rope with your 8m of chain would be the go I reckon. The rope has to have a decent amount of stretch to it and those other rope's you mentioned( especially the dyneema) may not have enough of it.
The stretch helps to hold bottom better and takes some stress off of your hardware on the bow. I know your trying to get 200 m plus on there but that may not quite fit. What does the drum say it's capacity is?
12 mm is pretty strong and that is what that club marine info recommends also.
It's the worst weather that you wan't the anchor to hold in after all isn't it?

I believe it takes about 150m of 12, 200m of 10 or 300+ with 6mm (depends how full you want the drum. I am The info varies a bit so needs some interpolation. I was thinking of 150m of 6mm with 100m of 8mm on top.

I believe the nylon will have appropriate stretch form all accounts, and is recommended as anchor rope for exactly that reason. I could do a top shot over other line without stretch (such as polyester). The dyneema keeps coming up (no stretch), but it is just to expensive. From what I have read, it appears nylon is about 20% stretch, silver rope (polyethylene) up to 40%, Polyester about 5% (not enough give for anchoring, but ,maybe ok under nylon).
The silver rope is commented regularly as too much stretch and also floats, so not recommended. Having said that, I used it without concern on my old boat....

Comments re load to dislodge an anchor in sand (or straighten a reef pick) are a fair point. You would think 900+kg would easily do that.

Re holding in bad weather, yes and no. For what I do, I would never likely be in a situation where I am forced to stay anchored in really bad weather. This set up is really for deeper offshore stuff. For other circumstances like camping away for a week or something, I would possibly change to a shorter but heavier rope for close to shore type anchoring.

My main question is will I break off 900kg line pulling anchors etc offshore?
Any one else with ideas or experience out there?

10mm silver breaks at the load of what I am looking at, I would expect that would be ok..... anyone running 10mm silver on a larger boat???

[Darren Mc]

Yeah dyneema is used in some of the better quality braid fishing line's so it's no wonder it's dear and it's certainly got little to no stretch.
Maybe 10 mm silver would be sufficient. I've got that on my boat and I certainly feel's like it's plenty strong. I've had to drag the anchor off with the motor a couple of times and it's held up no worries.

[EdBerg]

Personally I would not use 6mm nylon on a boat that size and weight, no one expects to get out in a storm but it happens, your engines may not start up and a storm could catch up to you, having a boat that size on 6mm nylon would probably stretch it's limit in strong winds and together with a large wave could shock stress it past its limit and snap. Also you have to take in consideration the rope deterioration due to sun, moisture, abrasion, constant stretch and release and other such factors, so whilst it may have 950kg breaking strain when new it will degrade over time and it won't be 950Kg for long.

You sometimes don't get a say in not getting caught in a storm, I was anchored at Bulwar at Morton Island once, beautiful day and night, mirror seas and the forecast was for a change about lunchtime to mid afternoon, about 5:00am I woke up to the boat rocking strongly so stuck my head out and saw roll clouds heading our way, woke the missus up and quickly started to hammer it across the bay back to Bribie Island, the wind was about 30-35 knot and the leading edge of the storm just caught us for about 10 minutes, the seas turned quite nasty across the bay and we managed to outrun it back home to Spinnaker harbour. Thoroughly drenched and cold but we made it. Had we stayed, we would have had to ride it out and 6mm probably would not have been sufficient, we might have been able to get to Yellow Patch. But if we weren't next to a big Island which was close by, it would have been a different story. Dyneema is not suitable for anchor rope due to lack of stretch as it will put too much shock stress on the rest of the components and will probably jerk the anchor out of the sand/mud, where as using nylon would just stretch the rope and the anchor would stay buried.

In my opinion 10mm Nylon would be the absolute minimum for your size boat and preferably 12mm Nylon. My boat is about 2.6t and I use 12mm Nylon with 16m of 8mm chain plus I carry spares.. Just my 2 cents.

Cheers

Ed.

[Fed]

15 Kg mono can hold a 5 Metre boat in a 1.5 Metre swell with a jig treble as an anchor.... from the back.

Sort of makes me wonder just how big your rope really needs to be for day tripping.

Same goes with reef anchor prongs for day trips, when I see how much grunt it takes to straighten one 8 mm prong there's no way that could happen from normal wave action.

Another thing that bugs me is the recommended amount of rope to let out, 3:1, 5:1, 7:1... I never let out more than about 1.5:1 which puts the rope angle at about 45 degrees.

No flames guys just my thoughts after a lot of years anchoring on reefs, I don't do sand.

[ShaneC]

Hey Darren,

Go the 12mm silver mate and load it on tight. I have 12mm on my stress free and fit 200m on it quite neatly. I also use 12mm in the anchor locker and got 500m in there for no other reason than if I have to cut it I still have enough to stay out and anchor comfortably. I very rarely use the stress free in preference of a big float and using the boat to do the work with a Mooloolaba pick. Its an easy job pulling in the rope in everything but the worst conditions and since its your boat it wont be you doing it.....

[Dignity]

Hi Darren J, twice I have been caught out wide in some pretty severe unpredicted weather, both times Coast Guard were still issuing calm weather warnings and the storms hit hard and fast. Another time we were anchored south of Tipplers with a rear anchor to shore, I was with a club at the time and we checked all the boats and those with only 6mm were shifted to sit midstream or we loaned extra anchors and rope to those that wanted to listen. This storm we could see building over Brisbane and when it hit it hit hard, this was the one that flipped boats and planes at Southport many years ago, quite a few of our tents were flattened, all of the boats that took extra precautions came out unscathed, a houseboat that wouldn't accept our advice ended up somewhere near Couran Cove and another boat who "knew what he was doing" broke his 6mm rope but fortunately he stayed on board and was able to manage the storm but he did have to change his pants after.
I used to use 6mm offshore on a 6metre boat, but after loosing 3 anchors, the last one only put on the same day, I swapped to 10mm as a minimum. This was silver rope, brand new and it snapped 2m from the bowsprit and it wasn't under any real load at the time. I am also looking to changing to a drum winch and I also will have to make a decision on what type of rope and what size so I don't envy your current position, good luck.

[Darren J]

I used to use 6mm offshore on a 6metre boat, but after loosing 3 anchors, the last one only put on the same day, I swapped to 10mm as a minimum. This was silver rope, brand new and it snapped 2m from the bowsprit and it wasn't under any real load at the time.

Thanks for the info, this is the first confirmation I can get of lighter rope breaking in "normal" conditions. That doesn't surprise me either, 6mm silver is typically rated about 380kg. Bunnings etc don't even give ratings, so who knows what their 6mm would really be, after use and wear it may be under 200kg.... The 6mm nylon I was considering is 2.5 times the new 6mm silver ratings.

After changing, did you find the 10mm silver ok, as in never had concerns of it breaking? The 6mm double braided nylon I was considering was the same break strain as 10mm silver, so directly comparable I think.

I am seriously thinking about 150m of 6mm nylon (950kg rated) with 100m of 8 or 10mm nylon (1.3t-2t+ rated) on top. That way in shallower water I will have high strength, should I ever drop in deeper it would be in "good weather" etc if anchoring on a mark. Possibly also with reef anchor only or at least a trip for easier release.
I also always will cary a spare 100m spool of 12mm cheap silver in reserve for emergency. I also typically carry spare anchor and chain.

I will have other gear for storm type scenarios, I mainly want to determine an acceptable minimum strength so I am not getting break offs for no reason in normal conditions.

I might talk to some of the winch suppliers further, it was one of them who was pushing me toward 6mm dyneema with a top shot of 50 or so metres of nylon for shock resistance.

[Darren J]

Hey Darren,

Go the 12mm silver mate and load it on tight. I have 12mm on my stress free and fit 200m on it quite neatly. I also use 12mm in the anchor locker and got 500m in there for no other reason than if I have to cut it I still have enough to stay out and anchor comfortably. I very rarely use the stress free in preference of a big float and using the boat to do the work with a Mooloolaba pick. Its an easy job pulling in the rope in everything but the worst conditions and since its your boat it wont be you doing it.....

Shane,
I was thinking the same, but it may only be the wife and I from time to time. That means its me driving and pulling in....I have free fall, so while it may take a bit, want to be able to release a large amount if needed.

[Fed]

Dignity did your 3 ropes break while you were anchored or were you doing something like pulling the anchor up?

[ShaneC]

Shane,
I was thinking the same, but it may only be the wife and I from time to time. That means its me driving and pulling in....I have free fall, so while it may take a bit, want to be able to release a large amount if needed.

Ah cool, no worries mate. I dont take chicks fishing. I dont want to take the wife and she does not want to go so no such dramas for me....