rope cutter advice

prv said:
I guess that works for free-floating litter, but not if you get hung up on a pot rope. The outboard may push Harmony along OK, but it ain't gonna tow a string of pots along the bottom.

Pete
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I am sure it will not but in my experience x 2 - you can usually get hold of the pot rope with a boat hook to get a knife to it so that you can cut it free - not before leaving a nice fender on it to mark the pot line for the owner of course

it is pretty awful when the biggest fear of a non crustacean eating sailor who is planning a trip around the top of Britain is lobster pot crud getting caught around a prop

I really wish that British people would decide to stop eating salty spiders and scorpions
 
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dylanwinter said:
and staying well out of the lonster pot fields

D
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The west coast is one big field of pot buoys!
We've seen them in the middle of the Minch, just off Cape Wrath, up and down the coast absolutely everywhere. Don't have a cutter but would like one. We try to avoid motoring at night, and during the day try to keep a regular enough look out the front. Size of waves makes a big difference.

The only time that we have actually hit one was in perfect visibility in the middle of the day, during a race, of course. It was lying about a boat length to one side of us and our keel hit its rope, it was dragged rapidly towards us, then under, and then bobbed up again behind us. Count that as lucky/foolish.
 
As you already (will) have propulsion back-up with the outboard motor the rope cutter performance is less critical. I have had the disc cutter type fitted to my last two boats and on each lift out have found evidence of them "doing their job" as indicated by marks on the cutter blade. My present boat came with a Spurs cutter which requires additional maintenance in the form of anode and bearing replacements at regular intervals. The money saved with the disc cutter pays for a fair chunk of the outboard or bracket.
 
Don't forget that it's also possible to be brought to halt by a rope snagging in the rudder. This happened to me off point lynas and i had to call out rnli. We weren't motoring at the time.
I presume you'll be sailing most of the time but you're still not completely immune and a rope cutter won't help (or a standby motor). Keep a good lookout at all times and don't sail in the dark.
It doesn't happen very often!
 
My experience of the Ambassador is less than good. We have picked up ropes twice and on each occasion the fixed part on the P-bracket was ripped off. There is now a collar designed to strap around the P-bracket boss to prevent it but by the time it was introduced I had given up and bought a Prop protector. No idea whether this works or not but we certainly have not had a rope problem since buying it.

The article linked to above, also printed in YM, found the Prop protector to be almost as good as the Ambassador, only failing to cut electric cable. However, it has been suggested that the test procedure is flawed.

Dylan, if your shaft is 1" I have an Ambassador, minus the fixed cutter, that you can have cheap.
 
Hadenough said:
http://m.youtube.com/watch?v=WADETXBD3Pc&desktop_uri=/watch?v=WADETXBD3Pc

Have you seen this? My actual experience us that the disc cutters are a waste of time but the scissor, in my case Ambassador, type are lethal to ropes. As long as you are motoring of course! Expensive though.
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My actual experience is that they do work. I fitted a disc at the same time as my Maxprop. On the first cruise with it my prop was entangled with a mooring line which stalled the engine, I restarted, put it astern, then forward and the disc cut it free. I wrote it up in Yachting Monthly, together with a photo of some of the rope that remained wound round the prop until a diver pulled it off, but it did not stop me motoring.

The more complex ones can be broken by the forces involved. The problem with them is that the fixed part has to be screwed to the P bracket. On a modern yacht there is often insufficient metal in the bracket for much thread engagement, and as a result the threads can be stripped out. There is a link to another thread on here where the owner of such a device describes its failure, and that is not an isolated instance as I have seen a boat on the hard in my marina with the same problem.

I have found a photo of some of the rope recovered from the prop.. What happened was that a plastic bottle was attached to piece of polypropylene string which led to a mooring rope attached to a chain on the seabed. The bottle was under the bat when I started the engine. It wound up the string then wound the rope round the prop. Going into reverse then forward cut it free. The rope it cut was 16 or 18mm braid on braid.
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Dylan,

save your fenders !

I asked ' Fisherman ' of these forums what to do about pot lines & buoys, his answer - and he is a very experienced pro' at it, not some berk laying a few illegal pots for his mates' pub menu - was not to bother marking a pot he can recover them easily by grappling, as long as they're not pulled too far out of position.

Fisherman is obviously a good type, but if these other people are going to lay dangerous traps for everyone else I don't see why we should donate more expensive gear like fenders when they already cost adding prop cutters etc, detours around useful short cuts when bad weather threatens, and the damage including engines ripped off beds sometimes...
 
It helps if you understand how the disc cutter works. It does not work as a spinning blade slicing the rope. What it does is provide a sharp edge against which the rope is pulled tightly by the turning propeller. If the first pull does not cut right through the rope before the engine stalls all you need to do is restart and slacken the rope by giving the prop a few turns in reverse, then go forward again, if necessary repeat procedure. Some discs have a serrated edge, mine does, but I am not sure whether that adds anything.
 
It's good to see one person Norman_E appreciates what is going on at the prop.

For balance there are three distinct types, Scissor, Disc and Shaver. I supply the Shaver so anything I say may be considered biased but I try to just stick to facts or explanations of what happens and I'm happy to list the other suppliers.
Spurs/Gator/Stripper are scissor
Shaft shark/prop protector there are many single and double discs from stern gear suppliers, serated plain, split clamp on.
quicKutter shaver

Debris caught is caught by the rotating blades, this winds the debris onto the shaft directly in front of the prop, eventually reaching the bearing carrier P bracket or stern tube, then you start to do damage as there is significant pressure that tries to pull the shaft out or bend the bearing carrier whilst at the same time blocking any water exiting the bearing causing it to run hot. The debris will climb over the disc and will be pushed hard against it but as Norman spotted it is not slicing as the debris revolves with the shaft. Scissor cutters will cut rope that lies along the shaft line, but a rope across the path of a vessel would not be in a position to be cut but could be caught by rotating prop blades, that's why I think you get reports of scissors happily chopping line but also some that get damaged in the process of chopping.

This was the fundamental flaw in the tests that you can find on youtube, in the tests the rope was fixed at the P bracket so the rope could not rotate with the shaft, if it got caught by a blade it was pulled apart and if it wasn't caught by a blade it was fixed in relation the the spinning scissors or discs so it was easily cut. It was also forced to lie along the shaft line so in an ideal position for a scissor cutter to cut it, it was almost as if the test fed rope/wire etc into the chopping blades rather than get debris caught by a prop blade and wind it in to see what happens. As the shaver cutter only cuts what is caught by a prop blade this test would not have worked so we declined to take part as it didn't represent what happens in practice. Had they done the test that we would have liked I think there would have been damage to the other cutters or the test rig.

The cutter we supply (to the RNLI and RN) is a shaver not disc or scissor, this is a fixed blade that relies on the debris rotating with the shaft to work, a spool or winch drum effectively is attached to the prop to give a flat surface for debris to wind on once caught by a blade, the debris winds forwards until it is pushed against the cutting blade and is shaved through much as a lathe tool works. There are many other benefits but then this might sound like a sales pitch.

In answer to a comment about more complex cutters having fragile fixings, to date two quicKutters broken one by chain (Falmouth VT pilot boat) and another by metal ware in a net. On commercial vessels including many fishing vessels they have operated effectively for more than 5 seasons without maintenance.
 
Have had a disc cutter for eight years: it certainly cut through the genoa sheet some herbert dropped over the side and once caught something else which a couple of f-n-r's cleared though I never saw what it was.
 
I've not had a boat with a cutter. The skeg idea did not work on my skegged Macwester 26' when some eejit :rolleyes: caught a sheet off Sutton on Sea and had to beach. 6 hours for 60 seconds work..

I think the water flow, the whole idea of a prop after all, will collect junk whatever the shape? Edit: I guess a skeg would help with a taut rope, eg between a pot and a buoy....

My vote is boat hook, bread knife and duct tape. (my Mirage 2700 has a transom hung rudder and a prop visible and in arms reach from a dinghy or low pontoon (ask me how I know....)

Nick
 
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