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Old 19 October 2017, 11:35   #1
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Anchor Weight, chain and rope size

Hi,

I'm looking to get an anchor for my new rib, I think I need a Bruce anchor but am unsure what weight I need the anchor to be and what type of rope, chain and what diameter the rope and chain should be. it's a 3.8m Rib.

Any comments would be great

Cheers Matt
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Old 19 October 2017, 11:57   #2
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Anchor Weight, chain and rope size

My recommendation would be a 2kg Bruce (or 3.5kg for overnight/rough conditions), 4m of 6mm short link chain, 30m of 8mm nylon rope (plus another 30m as back up).
P.S. Good choice of anchor for mixed conditions.
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Old 19 October 2017, 15:31   #3
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I have similar anchor Bruce 2.5kg? Similar chain 6mm 3/4m, but less rope 10m on anchor and another coil as mostly anchor in bays and need 3/4m of rope.

One tip fix the chain to the wide end, with shackle then to the thin end with a cable tie, that way if it gets stuck in. A rock or heavy chain etc the cable tie snaps and the anchor pulls away from the other end.


PS much better than a grapnel in all sea beds!





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Old 20 October 2017, 02:29   #4
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One of these as a secure killick in heavy weather / fast currents...



Qtr cwt version for light / normal duty...!

Also helps to ballast the bow when riding solo...!
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Old 20 October 2017, 03:11   #5
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HDAV are you sure those cables ties would snap? Looks like three of them in the photo Iím not sure I could pull one apart with my hands - think cheap handcuffs for police - are they a weaker type?
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Old 20 October 2017, 05:33   #6
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Cable ties have always worried me - I doubt you could pull the anchor rode hard enough to snap three cable ties if the anchor was stuck and in rough conditions I don't have enough confidence in cable ties.
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Old 20 October 2017, 09:28   #7
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RRK

If you ever get some "air" a la MattH that 56 will punch a nice square hole in your hull.

Regards
TSM
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Old 21 October 2017, 02:32   #8
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We use up to 10 cable ties to secure our Bruce. They dont snap. The ratchet part fails and they pull out. If necessary they can be re-used a couple of times. Much easier than using cord. Also better than losing the ground tackle😀😀
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Old 21 October 2017, 06:00   #9
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Quote:
Originally Posted by charliee View Post
Cable ties have always worried me - I doubt you could pull the anchor rode hard enough to snap three cable ties if the anchor was stuck and in rough conditions I don't have enough confidence in cable ties.
You need to trust the physics! There are plenty of yachts far bigger than your RIB using this method and I've never heard any of them say it failed. I think yachts tend to only do it with someone around (not leaving the boat in a storm for instance). Some yachts only do it on uncertain bottoms.

You should be able to snap a standard cable tie with a good few heavy pulls. But the angle is important! You want to be snapping in the thin direction (?1.5mm) vs the width (?6mm). That is why lying at anchor doesn't snap them - the chain is pulling across the tie width. You should be able to test if you can create the force to break it by attaching chain to a solid point ashore and pulling hard.

In a storm you'd need your rib to be above the anchor and then pulling hard on the cable tie (as you will be if retrieving). That won't happen... if you have drifted above the anchor there will be slack on the line & chain.

As for force to break it - I can snap a cable tie with some arm force. But you don't need to be strong. Use physics again. Pull in all the slack on your anchor rode so you will be directly above the anchor. take a single turn round a strong cleat on the boat. Now as soon as the bow gets to the bottom of a wave take in the slack on the cleat and hold it. As the wave peaks the bow is pushed high with all the bouyancy of the boat you are looking at several 1000N of force. (If there are no waves you can achieve the same by simply standing well forward to push the bow down, cleat tight, move weight back...

(We should be conscious that we are adding to the plastic pollution in the sea doing this.)

Even if you do get a "freak wave" (You know that the media blame for all sea disasters) that somehow snapped the cable tie the load will remain in the direction needed unless the wind or tide shifts...
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Old 21 October 2017, 11:01   #10
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Quote:
Originally Posted by j.i.wilson View Post
We use up to 10 cable ties to secure our Bruce. They dont snap. The ratchet part fails and they pull out. If necessary they can be re-used a couple of times. Much easier than using cord. Also better than losing the ground tackle����

This is my experience....and even though I don't use 10!...(two or three smallish ones ) on a 7m RIB with pretty long reasonably heavy gauge chain... ( the key to good anchor performance IME) even pulling up directly above the anchor (when stuck) it takes some prolonged effort to snap the cable ties and release the Plough or Danforth anchor I use.

I've held many many times in extremely strong Bristol Channel tides...Sometimes coupled with Big Seas with no problems,plenty of suitable warp (with some stretch ) also helps.
It always amuses me that people will argue endlessly about the superiority of this or that VHF..aerials...PLB's...Mobiles phones...DSC..Laser...Piro Flares ...Radar Reflectors Plotters ect ect ...and as important these things undoubtably are.

IMO the Anchor Warp and deployment/recovery system whilst being the most Basic piece of Saftey Kit you carry in terms of tech..Is in the final analysis THE MOST important....and something you should practice with and have 100% confidence in!
In an emergency situation a well deployed/secure anchor will let you ride out most events in Safety ....and buys you that most precious of all commodity's... Time!
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