Originally Posted by charliee
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...