Rope cutter - worth it?

[tudorsailor]

+1 for an Ambassador. It certainly saved me when I got the mooring line into the prop when leaving the berth in Mallorca. When I returned later to the marina, I could see that the cutter was able to deal with a very chunky line!


TudorSailor

 

[GTom]

Any thoughts about this guy?

Shaft Knife Plus - Rope Cutter

I am a bit reluctant to use anything with moving parts - besides, 400+pounds sounds a bit heavy for scissor type cutters...

 

[peter gibbs]

There are cheaper cutters - the least complicated and least effective is just a disc with an edge. Trouble is you need two surfaces for effective cutting.

This one is new to me but I know the Ambassador cutter with serrated cutting edges is effective and well sold. Yes that costs £400+ but one engagement with ropes or netting pays the cost outright, and you get home in reasonable certainty of maintaining control. Mine have saved my bacon on several occasions, and no doubt others where it has cut me free without my knowledge.

PWG

 

[Daydream believer]

I have made a clone of the Ambassador. It is the second one I have done having had the first on my boat for 4 years & I know it works because I have cut several bits of net & rope . It is for sale at £ 370-00 ( Ambassador quote something like £ 590-00)

I will be making some more if anyone wants one & could do some variants if I can see the boat.

I would rather sell it to someone near to Bradwell as it is for a 120 saildrive & I would like to check owner is happy before taking the cash. It is the 2 bladed cutter version. The prop needs 2 holes drilling for the cutter drive. Details on the Ambassador site & it is quite easy to do. It may fit variations of the 120 but I cannot be sure. Dimensions are virtually the same. Includes a spare set of bearings.

I have also supplied some friends with the “Prop Protector Rope Cutters” & I can supply the 80mm diam ones at £ 65-00 for the one piece ones & £85 for the 2 piece . I would make to order over the winter. These are OK for saft drive props. However, in my opinion, they are nowhere near as effective as the Ambassador. But better than zilch.

 

[GTom]

I have made a clone of the Ambassador. It is the second one I have done having had the first on my boat for 4 years & I know it works because I have cut several bits of net & rope . It is for sale at £ 370-00 ( Ambassador quote something like £ 590-00)

I will be making some more if anyone wants one & could do some variants if I can see the boat.

I would rather sell it to someone near to Bradwell as it is for a 120 saildrive & I would like to check owner is happy before taking the cash. It is the 2 bladed cutter version. The prop needs 2 holes drilling for the cutter drive. Details on the Ambassador site & it is quite easy to do. It may fit variations of the 120 but I cannot be sure. Dimensions are virtually the same. Includes a spare set of bearings.

I have also supplied some friends with the “Prop Protector Rope Cutters” & I can supply the 80mm diam ones at £ 65-00 for the one piece ones & £85 for the 2 piece . I would make to order over the winter. These are OK for saft drive props. However, in my opinion, they are nowhere near as effective as the Ambassador. But better than zilch.

Thank you. I am reluctant to use anything with moving parts in it. OTOH, a braided blade, such as the shaft knife I linked above might not be as bad as a plain disc...

 

[Norman_E]

Disc cutter is useless....but I think with the combo of saildrive and Ewol prop that it's the only option available. Happy to look more broadly if anyone has recommendations, thank you.

Keep spreading the myth about disc cutters, they do work, and I have ample proof of that. See Yachting Monthly April 2012, page 75.

 

[Norman_E]

Any thoughts about this guy?

Shaft Knife Plus - Rope Cutter

I am a bit reluctant to use anything with moving parts - besides, 400+pounds sounds a bit heavy for scissor type cutters...

Interesting design, but it seems to be founded on a view that rotating teeth will cut a rope, which is not how single piece cutters work. They work by the simple fact that the rotating propellor pulls the rope tight against a sharp edge, which at that point is not spinning relative to the rope, instead small relative movement of the rope fibres in tension against the sharp edge causes them to be cut. By trapping rope in its deep notches that design might well have reduced effectiveness compared to a plain disc. I would be interested to see a comparative test.

 

[GTom]

Interesting design, but it seems to be founded on a view that rotating teeth will cut a rope, which is not how single piece cutters work. They work by the simple fact that the rotating propellor pulls the rope tight against a sharp edge, which at that point is not spinning relative to the rope, instead small relative movement of the rope fibres in tension against the sharp edge causes them to be cut. By trapping rope in its deep notches that design might well have reduced effectiveness compared to a plain disc. I would be interested to see a comparative test.

sharp teeth?

 

[Daydream believer]

Thank you. I am reluctant to use anything with moving parts in it. OTOH, a braided blade, such as the shaft knife I linked above might not be as bad as a plain disc...

You are probably correct & I have been thinking of making a disc cutter with serations; but fairly small so they just grind through the polythene or netting. I n my experience I have caught more nets & other rubbish, as well as weed ,than simpe rope. However a rope attached to a line of pots can put a lot of strain on a "P" bracket & do a lot of damage. That is why the item needs to be cut quickly in the case of a rope. With polythene & net the prop needs to be reversed & forwarded a lot of times. Puts strain on theclutch though.
One also has to accept that once the item has been cut it may still be in the prop. I have a Brunton & that gets seriously out of balance when I get the sort of weed with long strands that one finds in North Britainy. A Rope cutter chops the main stalk but there is always a bit stuck to the prop causing imbalance for quite a while.
I know this because I have seen the bits float free plus I have dived over to clear some.

 

[sailorman]

I know that the Ambassador Stripper works - I have cut one of my warps, 16 mm double-braid polyester, and 12 mm polypropylene pot marker without a buoy. Unfortunately, each time it ripped the static part out of my P-bracket. There is nowadays a beefed-up sleeve to put around the P-bracket to avoid this, but of course just beefing things up results in something else failing if the load is sufficiently high. Since these problems I have had a disc type cutter. On the only known occasion that I picked up a rope it did nothing but that was understandable as it was caught by the blades and pulled astern.
View attachment 86560

Was that an East Coast pot line

 

[peter gibbs]

You are probably correct & I have been thinking of making a disc cutter with serations; but fairly small so they just grind through the polythene or netting. I n my experience I have caught more nets & other rubbish, as well as weed ,than simpe rope. However a rope attached to a line of pots can put a lot of strain on a "P" bracket & do a lot of damage. That is why the item needs to be cut quickly in the case of a rope. With polythene & net the prop needs to be reversed & forwarded a lot of times. Puts strain on theclutch though.
One also has to accept that once the item has been cut it may still be in the prop. I have a Brunton & that gets seriously out of balance when I get the sort of weed with long strands that one finds in North Britainy. A Rope cutter chops the main stalk but there is always a bit stuck to the prop causing imbalance for quite a while.
I know this because I have seen the bits float free plus I have dived over to clear some.

I endorse the comment that the cutting has to be immediate on contact. The idea of the prop continuing to exert a sawing action over numerous revolutions is false. A rope of any thickness to impede the boat will bring the prop to a halt within a couple of revolutions by which time the opportunity to cut and free is gone, the engine has stalled and possibly rope is wound solidly onto the gear. When nylon is put under stress it is capable of fusing, at which point the remedy is limited to a diver.

I have no commercial connection with Ambassador but their gear, amongst other similar suppliers, does exert maximum sheering force from the outset so optimising the chance of cutting clear before the prop comes to a halt. When this happens you have a second chance by reversing the prop, employing short stabbing bursts back and forward to let the cutter have a further go at cutting clear; this is what I did successfully when wrapping a large plastic sheet on my gear.

Single cutter discs do not support this approach.

Yes, there is always the possibility of stressing the propulsion gear or the shaft / support bracket when using a cutter but going over the side in anything other than the most benign conditions is a very risky personal move for 99% of sailors. Done that too.


PWG

 

[AntarcticPilot]

Yes, there is always the possibility of stressing the propulsion gear or the shaft / support bracket when using a cutter but going over the side in anything other than the most benign conditions is a very risky personal move for 99% of sailors. Done that too.


PWG

+1 about going overboard - I too have done that, in my teens! I've told the story before, but it bears retelling as a warning a) that diving at sea is the last resort and b) that you can only do it with support from an able-bodied crew.

We were sailing my Dad's Halcyon 27 down the east coast of Scotland, roughly off Arbroath, and I was at the helm. We encountered a pot buoy which I hadn't spotted, and came to a grinding halt, held by a rope on the propeller. Various attempts to remove it were made (knife lashed to a boat-hook, forward and reverse gear etc.) but none were successful, so I was volunteered to dive to free the prop. I was, and am, quite happy underwater and can hold my breath for a reasonable length of time. Anyway, we deployed our inflatable, and my father and my brother tended a line from the dinghy while I dived. First of all, I didn't hang around at the surface - the water was cold, and the swell made the overhang of the boat likely to hit my head! I went down and sawed away at the rope (my knife was sharp - I've always kept sailing knives sharp!) . After the first dive, I could, JUST, get back onto the inflatable under my own steam, but was glad of help from my father and brother. After the second, I definitely needed help to get into the inflatable, and after the third, they had to resort to letting pressure out of the inflatable to get me back into it; even with two grown men assisting me (my brother and I were in our late teens). My strength in the cold water dropped very quickly. Fortunately, I'd got the rope free on the third dive! Ever since, I have been VERY respectful of the weakening effect of cold water - as documented by videos of Olympic swimmers on the Sea Survival course.

Ever since, I have regarded voluntarily going into the water as something to avoid unless there really is no other option.

As an aside, the Halcyon 27 has the best protected propeller that you can imagine; it is in a small recess at the back of a long straight keel. It is also the only time I've snagged a line!