Rope cutter

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robertj

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Just wanted to ask the forum about rope cutters.
My spurs ropecutter has again snapped off at the blades this one being only 2 seasons old.
I wondered if other formulites have had the same problem with the Spurs Cutter or is it just me.
When the previous cutter broke after picking up my dinghy painter I put it down to bad luck even though the rope was quite small dia. or possibly out of alignment etc etc.
It was installed by myself to the fitting instructions, checked each season and readjusted if needed checking all screws etc etc
the difference being the previous breakage was the base block, this time the cutters snapping.
I am not sure about replacing with another 'Spurs' or even replacing at all.
I know if two boats who have had same problem is there more?
 
We have the Ambassador Stripper on our leg - I have no idea if it has ever been called into use - certainly not from a trailing warp from my boat anyway - but there is no way in hell those blades are going to break off ...
The weakest point is the pin that holds the static part in place - I had to get that bit re-welded as it had come loose ...
It's a lot of money for one - but ours is still very sharp despite being ignored on the bottom of the boat for years!
 
robertj said:
Just wanted to ask the forum about rope cutters.
My spurs ropecutter has again snapped off at the blades this one being only 2 seasons old.
I wondered if other formulites have had the same problem with the Spurs Cutter or is it just me.
When the previous cutter broke after picking up my dinghy painter I put it down to bad luck even though the rope was quite small dia. or possibly out of alignment etc etc.
It was installed by myself to the fitting instructions, checked each season and readjusted if needed checking all screws etc etc
the difference being the previous breakage was the base block, this time the cutters snapping.
I am not sure about replacing with another 'Spurs' or even replacing at all.
I know if two boats who have had same problem is there more?
Click to expand...

It is a function of the design. It is narrow at the base and if the hook at the end catches something the blade breaks off. Also it is not made out of 316 stainless but a hardened stainless (because the blades are sharpened) which is both brittle and can corrode - hence the need for the little anode.

The fact that you are picking up ropes suggests you need a cutter - but one that works and doesn't break.
 
Csail said:
Ambassador stripper is regarded as the best.
Click to expand...

It may be, but beware that the metal thickness of many P-brackets is extremely small, no more than a few millimetres. The screws holding the fixed block to the cutless bearing housing have fairly coarse threads, easily stripped. The first time this happened to me was with polypropylene rope of about 16 mm, shown in http://coxengineering.co.uk/Pbracket.aspx. The P-bracket looked a little corroded and I blamed its condition on the failure.

However, the replacement new bracket, with the Stripper block fitted under ideal conditions in my workshop, failed in exactly the same way the first time it was called upon to do anything.

I have now abandoned the blade type and use a Prop protector, which came out almost as well in the YM tests and does not involve a fixed block.
 
This latest incident has made me decide to abandon the stripper, as I didn't pick up anything at all other than weed. I'll contact Harold Hayes as they were extremely helpfull last time hopefully even more so this time!?

Vyv is this the disc type cutter you have fitted now?
 
TJB1 said:
I had a fixed blade break off an Ambassador Stripper - never did find out what caused it.
Click to expand...

Shark?

There must have been a longer term problem for the blade to break off as (I think - from my inspection) it is machined out of a plate of (stainless?) steel - the only weld is the pin that goes into a locating hole in our sail drive leg - this is where I would expect a failure.
 
vyv_cox said:
Yes, the Prop Protector is a plain blade. Until I saw the YM videos I couldn't see how a blade like this could work. Of course, I was not realising that the rotation of the prop pulls the rope in against the blade, so it cuts perfectly. Easy once you know!
Click to expand...

I don't often disagree but I will now, I witnessed the testing and as a result decided not to allow YM to test the quicKutter in the way they had planned. They did not test rope caught by prop blade rotating with the shaft and winding onto the shaft, and were unwilling to try this test. This is how we have tested the quickutter as this is what happens and causes most damage. If you have ever seen a disabaled prop shaft, the debris is wrapped tight against the shaft between the prop and P bracket with many turns very tight. It is not attached to the P bracket and dragged across the area in which cutters are fitted.

In practice a rope caught by the prop will be winding onto the shaft and hence rotating with the shaft, in this scenario the discs are not moving relative to the debris so there is no slicing action.

By fixing the debris to the P bracket (as ym test did) rather than the prop blade (ie caught by prop) the disc is slicing and the rope is pulled across the cutter (the debris is stationary once it is tight relative to th erotating shaft). If a pot rop is caught by a prop blade it can be winding the rope up from the sea bed from aft of the P bracket in which case the rope will wind onto the shaft at shaft speed aft of the disc or scissor, even if it climbs over the disc it will be rotating with the disc so there will be no slicing action.

the test demonstrated how you could use the disc or scissor to cutter to cut debris rather than evaluate if or how the cutter would cut debris caught by a prop.

I hope readers see this as an accurate analysis to inform people of facts and let them make their own decisions rather than anything blatantly commercial.
 
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Fair enough, yours are valid criticisms of the test, I think. Seeing as my cutters failed twice on the only two times they were asked to do anything I'll take my chance with the disc.

How is the shaver attached to the P-bracket? Would it be any more secure than the fixed part of the Stripper?
 
I have a plain disc cutter. Last week I picked up the riser from a mooring and it cut off a rope that was either 14 or 16mm braided line. The rope remained wound round the boss of the Max Prop, but was cut free so that I could still motor. Often the simplest designs are the best.
 
vyv_cox said:
Fair enough, yours are valid criticisms of the test, I think. Seeing as my cutters failed twice on the only two times they were asked to do anything I'll take my chance with the disc.

How is the shaver attached to the P-bracket? Would it be any more secure than the fixed part of the Stripper?
Click to expand...

The blade holder is attached with three bolts (M8 on smallest cutter) but the highest part of the blade is only 10.00mm above the fixing level and the blade only extends aft of the fixings by around 25.00mm so leverage on the fixings is far less, there are also no shock loads when it meets debris.
DSCF0370thmb.jpg

There's a high def image here http://www.h4marine.com/Images/DSCF0370.JPG
 
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