Rope cutters... a useless waste of money?

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Bloater

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Having read the article on rope cutters in this month's MBM I was struck by a) how expensive they can be, b) that anyone believes they actually work and c) how little evidence there exists as to their success rate.

Taking the pictures at the top of MBM pages 78 and 79 it occurs to me that if a 'bundle' of rope like that is caught around your propeller then no rope cutter could be successful in cutting that away. It would take a very long time with a sharp knife to cut away by hand even when held in a crane's slings.

Surely the senario where one strand of rope miraculously finds its way into the jaws of the cutter only exists in the manufacturers brochures.

How many times do you think the propshaft would be able to rotate with that amount of line on it? ...Enough to cut it all to shreds or to 'shave' it away? - You decide.

How do you know when the cutter has worked? - you only know when it doesn't. Are the manufacturers trying to sell us something that can't be proved? Where are the statistics?

(That's just my opinion for all it's worth).
 
Can't comment on the artcle either, BUT

Rope cutters have worked for us 100% so far. Agree they can't cope with every senario, but even if they copy with 70% of fouling incidents, that 7 more times they'll get you home safe! /forums/images/graemlins/wink.gif I wouldn't be without them either.
 
Again, not seen the article but have always worked for me - feel a lurch/drop in rev/ and bits of net/rope floating behind.

We did manage to break the fixed part on a couple of occasions.

W.
 
>> .......... Surely the senario where one strand of rope miraculously finds its way into the jaws of the cutter only exists in the manufacturers brochures.

How many times do you think the propshaft would be able to rotate with that amount of line on it? ...Enough to cut it all to shreds or to 'shave' it away? - You decide.... <<

You clearly haven't thought this through.

For example, at 2000 rpm with a 2:1 reduction gearbox, my propshaft is turning at 1000 rpm. I have the Spurs cutter which has two 'blades'', so each 'blade' is rotating at 1000 rpm, so with two blades, it means there are 2000 cutting actions each minute.

That is 33 'cuts' a SECOND!!! So the cutter is NEVER actually trying to cut a full thickness rope, but actually cutting into it at over 33 cuts a second as it is dragged into the prop! It's a progessive cut.

Like others here, I KNOW mine works after it cut through my brand new 25mm nylon mooring line virtually instantly. I just heard/felt a dull thud, then watched the pick-up buoy and remains of the line drift off downriver!

So yes, the cutter type (Ambassador/Spurs) work extremely well! /forums/images/graemlins/smile.gif /forums/images/graemlins/smile.gif
 
Saw a bloke in our marina last week, shred a 28mm bow mooring line!! A marina one, they were not chuffed, but he didnt even notice it. He has spurs on his.
If I could fit them I would, unfortunateloy with my shaft set up, its impossible, without buying new shafts.
 
Sorry, I don't see what the speed of rotation has got to do with it.

If the propellor snags a line then the line will be twisted around the shaft once per revolution. At 33 wraps a second... That's a big knot in a very short time.

If everyone says that these devices work then I will accept it and maybe invest in one - but I just don't see it makes sense - yet.

(Sorry - I mean't 16.5 tangles a second, not 33)
 
Re your poll - Quote "I've not got a rope cutter and never had a problem with a tangled prop"

That's the answer I would poll but me thinks it's tempting fate to shout about it - so I haven't voted.

But then again . . .
 
Exactly! ...debris caught by prop wraps around the space in front of the prop very quickly pushing hard against whatever it meets, this is either the Bearing carrier or P bracket. Without a cutter this debris can just pull the gearbox off the engine.

Shaver cutters don't need to grab the strand that's being wrapped to stop this build up, they let it happen for 1 or 2 turns and then start shaving.
 
I was wondering - most shafts you can fit cutters, outdrives you can't but then there's a fair chance you can lift and see the drives. What is the situation with ips? Anybody know?
 
I have a friend with rope cutters on his 13.80, I was with him when he tangled around a clump of fishing net, one short burst of the engines and the thing was shredded. Impressed me!
 
Having been caught by a poorly marked fishing net I resolved buy a cutter, and have been very pleased with it.

When crossing the channel its extraordinary how often one sees ropes, nets, lifejackets adrift, and it certainly makes me feel more confident having a rope cutter, particularly when the revs drop momentarily and then recover.

Of course if I were just sailing not motorsailing I might feel something different.

(Fishermen in these parts are reportedly using steel risers though, so I dont think a cutter would cope with that).
The big problem is unmarked pots and improperly marked nets in my area.
 
Had a disc type rope cutter fitted (the normal ones apparently couldn't be fitted on our shaft) and the following weekend picked up blue floating polypropolene rope at an anchorage off an island in the estuary.

Rope thoroughly wrapped itself around shaft, cutter et al. Melted into a blue humongous lump of plastic. Cutter was taken off and manufacturer never charged for the disc.

I'd still feel happier with a rope cutter though. It was just that this disc type didn't work.
 
Volvo and cutters

Volvo have been offered the quicKutter™ technology, which could be used on IPS drives with some minor mod's to the casting. They have shown no interest.

As an example of what a cutter for this type of drive would look like the outboard version is very similar, picture below. This would be behind the prop so it would have no effect on performance. This is a picture of one fitted to a Suzuki 90 leg.
Outboard cutter image
 
On one of our web sites, 'www.yachtlife.co.uk', that we used two years ago when taking our boat through the French Canals to the Med there is a section titled 'From Hayling Island to France'. On there is a photo of a fishing net that we 'picked up' 22miles south of St Catherins Point with a big hole in the middle shredded by our Ambassador rope cutter. This was the first of a number of lines etc. that it shredded on that trip. We often wonder how many more there were that we didn't notice. Well worth the money.
 
Re: Volvo and cutters

[ QUOTE ]
This is a picture of one fitted to a Suzuki 90 leg.

[/ QUOTE ] I have a Suzuki 90. Would you like me to test one for you? /forums/images/graemlins/smile.gif
 
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