Rope Cutters

[ianc1200]

Any views on the merits of Qwickutter rope cutters

http://www.h4marine.com/?page_id=72

vs Ambassador Rope Cutters?

Ambassador Marine

I can see a MBM YouTube comparison video but it was 15 years ago and didn't include the QwicKutter, which I believe the RNLI are using. Had a fishing net on my port prop (on an Aquastar 38) break the Spur Rope Cutter, so now need new & probably do both props whilst I'm at it.

 

[Tranona]

The qwickutter requires custom fitting to the propeller. Although the RNLI tried them a few years ago. not sure they still use them. Otherwise they have made no impression on the market in the UK which is dominated by Ambassador Marine.

As you have discovered Spurs have flaws, particularly the weird shape of the blade which is narrow at the base and is prone to breaking under load - not helped by being made of a hardened stainless alloy necessary to get a sharp cutting edge (also prone to corrosion hence the small anode required). The Stripper works on a different principle of progressive cutting with the serrated edges - like pinking shears as opposed to plain scissors where the cutting action is by the blades sliding over each other. This substantially reduces the loads on the stern gear when cutting and the blades are tapered from narrow at the ends to wider at the base. Made of 316 stainless so no corrosion problems.

Now boats are out of the water for the winter have a wander round the yards. This will give you a good idea of what others choose. Nothing has changed since the tests in MBM and Sailing Today all those years ago as no new products have entered the market since then.

 

[Bouba]

My rope cutter is just a circular blade with a scalloped edge…no moving parts.
Does anyone have an opinion or experience with them ?

 

[PaulRainbow]

My rope cutter is just a circular blade with a scalloped edge…no moving parts.
Does anyone have an opinion or experience with them ?

Yes, they are as much use as a chocolate fireguard. Had one on a previous boat, useless, honestly.

 

[Refueler]

I had the 'Stripper' ..... the serrated blade type ....

After a couple of years - when running the engine - a terrible banging / ratlling noise ..... lifted the boat ...:

Basically whatever had got into the cutter caused the anchored part to rip free from the shaft tube ... the amchored part to distort and then freed banging against the shaft blade part ...

I removed the fwd part of the assembly and left the blade fixed to the shaft ... and as Paul says for the disc version .. about as much use as a 'chocolate fireguard' ......

I am sure that the full assembly did its job ,, trouble is you will never know if it does or not - unless you drop a rope over .. but as you see - it does have its limits.

The half still in place did not cut / solve a weed / rope problem a few years later - despite those serrations still being razor sharp .... here's video of clearing the prop :

 

[Tranona]

I had the 'Stripper' ..... the serrated blade type ....

After a couple of years - when running the engine - a terrible banging / ratlling noise ..... lifted the boat ...:

Basically whatever had got into the cutter caused the anchored part to rip free from the shaft tube ... the amchored part to distort and then freed banging against the shaft blade part ...

I removed the fwd part of the assembly and left the blade fixed to the shaft ... and as Paul says for the disc version .. about as much use as a 'chocolate fireguard' ......

I am sure that the full assembly did its job ,, trouble is you will never know if it does or not - unless you drop a rope over .. but as you see - it does have its limits.

The half still in place did not cut / solve a weed / rope problem a few years later - despite those serrations still being razor sharp .... here's video of clearing the prop :

That is exactly what should happen if you hit something that jams it solid (very, very rare) as it is the "fail safe" feature. Reduces the chances of even more serious damage to the stern gear. However from your photo it looks like 2 of the screws were already missing as there seems to be only the remains of one that actually broke.

You (and others) are right a whirling blade however sharp isn't effective. Hang a bit of rope down then try and cut it by swinging your sharpest carving knife. Then use a pair of pinking shears to see the difference.

 

[Refueler]

That is exactly what should happen if you hit something that jams it solid (very, very rare) as it is the "fail safe" feature. Reduces the chances of even more serious damage to the stern gear. However from your photo it looks like 2 of the screws were already missing as there seems to be only the remains of one that actually broke.

You (and others) are right a whirling blade however sharp isn't effective. Hang a bit of rope down then try and cut it by swinging your sharpest carving knife. Then use a pair of pinking shears to see the difference.

The unit was secured with 3 machine screws as designed ... but two pulled out while one sheered ...

The only way to replace would be to either drill and retap original holes as the threads are 'pulled' or to mount in different position ... which I am loathe to weaken it further.

 

[Bouba]

You (and others) are right a whirling blade however sharp isn't effective. Hang a bit of rope down then try and cut it by swinging your sharpest carving knife. Then use a pair of pinking shears to see the difference.

 

[Roberto]

Yes, they are as much use as a chocolate fireguard. Had one on a previous boat, useless, honestly.

Have one from previous owner, works very well to make wounds in the hands when working around the propeller, otherwise basically useless.

 

[Tranona]

The unit was secured with 3 machine screws as designed ... but two pulled out while one sheered ...

The only way to replace would be to either drill and retap original holes as the threads are 'pulled' or to mount in different position ... which I am loathe to weaken it further.

Remounting in a different position typically opposite side is not a problem with a meaty casting like that. Unusual for the screws to pull out. Suggests poorly cut threads. Important to use the correct size tapping drill - 6.8mm for the M8 set screws (not 7mm which is for fine metric).

 

[Alicatt]

Visiting the Imperial War Museum in Leeds in the late 1990s, in the section with Katana there was one sitting edge down on a piece of silk, the silk was cut through to the padding underneath.

 

[Refueler]

Remounting in a different position typically opposite side is not a problem with a meaty casting like that. Unusual for the screws to pull out. Suggests poorly cut threads. Important to use the correct size tapping drill - 6.8mm for the M8 set screws (not 7mm which is for fine metric).

I've survived years without it and boat after keel repairs will spend its life on the River now ...

 

[Bouba]

I have to say, looking at it logically (without proof or evidence)....I just don’t understand how you can cut a rope with pinking sheers. If a rope got between the blades then surely it would stop the shaft instantly....whereas, a blade would just keep spinning until it’s sliced it’s way through, even if it takes hundreds of revolutions.
Of course, I am just surmising

 

[Jerbro]

I’m trying this… no idea how good it is… yet

 

[Tranona]

I have to say, looking at it logically (without proof or evidence)....I just don’t understand how you can cut a rope with pinking sheers. If a rope got between the blades then surely it would stop the shaft instantly....whereas, a blade would just keep spinning until it’s sliced it’s way through, even if it takes hundreds of revolutions.
Of course, I am just surmising

Then I suggest you have a look at this yachtingmonthly.com/gear/propeller-rope-cutter-test-30012 An enormous amount of research went into the development of the Stripper with its unique cutting action. It has been around for over 30 years in a huge range of applications from small yachts to big fishing boats, ferries, lifeboats, patrol boats, drug busters. shafts from 25mm up to 100mm plus saildrives.

I have spent many happy hours demonstrating how it works and meeting happy customers with their photos of what theirs have cut, in some cases bringing bags full of the net or rope they cut. Happy days!.

 

[Tranona]

I’m trying this… no idea how good it is… yet
View attachment 185421

Better than nothing but relies on chance rather than physics to catch and cut anything serious. Thge serrations are arguably better than plain because of the greater cutting area, but they mimic the blades of the real thing without understanding why they are that shape.

 

[Bouba]

I’m trying this… no idea how good it is… yet
View attachment 185421

I have never seen that style before.......it looks deadly !

 

[Bouba]

Then I suggest you have a look at this yachtingmonthly.com/gear/propeller-rope-cutter-test-30012 An enormous amount of research went into the development of the Stripper with its unique cutting action. It has been around for over 30 years in a huge range of applications from small yachts to big fishing boats, ferries, lifeboats, patrol boats, drug busters. shafts from 25mm up to 100mm plus saildrives.

I have spent many happy hours demonstrating how it works and meeting happy customers with their photos of what theirs have cut, in some cases bringing bags full of the net or rope they cut. Happy days!.

So you are the expert !......excellent....so the Stripper is best. Then probably the one I will buy next

 

[Jerbro]

Better than nothing but relies on chance rather than physics to catch and cut anything serious. Thge serrations are arguably better than plain because of the greater cutting area, but they mimic the blades of the real thing without understanding why they are that shape.

Another viewing angle… I can kinda see how it should work… rope gets caught, p-bracket is static, prop and cutter are rotating, rope is tightened and pulled into channel in cutter, vertical blade edge cuts rope!

 

[Refueler]

View attachment 185423
Another viewing angle… I can kinda see how it should work… rope gets caught, p-bracket is static, prop and cutter are rotating, rope is tightened and pulled into channel in cutter, vertical blade edge cuts rope!

Compared to the Stripper ... I think the gap is insufficient to allow the rope to drop in and get trapped / cut ...

The Stripper has tapered cutter blades specifically to allow the rope to get into the cutting area ....