Prop Shaft Line Cutters

[4HMainer]

Originally Posted by Eleebana

Does anyone have any real world experience of how effective line cutters are with feathering props?

The shouldn't be a great difference, the shaver cutters only cut debris that is caught by a rotating prop blade but they do work better if the cutter to prop blade root distance is kept below a couple of inches, on some feathering props this required some engineering in the form of a tube.

One thing I have experienced is that debris can prevent folding props opening or closing, I came into a dock at night after a long hard passage with debris on prop it worked OK in forwards but when I came to apply reverse there was nothing! I parked in the marina launch trying to explain in my best spanish I didn't normally park like this. next day revealed debris jammed in the folding gear teeth of the volvo prop.

[osirissail]

I have the Spurs from Spurs Mfg, Inc. and the unit has "saved" me three or more times when floating lines have tried to foul my propeller. Crab/fish/lobster pot lines and float are "scissored" very efficiently and unless you listen carefully for the little "thunk" you will not know you have snagged one and it was cut off.

Floating drift nets in the Caribbean passages - encountered two of them and the first one was cut cleanly from the propeller but the rest of the net was caught on the rudder and I dragged it all the way to Provo where I could anchor and untangle it. But the propeller was free, thanks to the "Spurs" so the boat was maneuverable although slowed down by dragging the rest of the net.

Another drift net was encountered west of Antigua and it was cut so that the prop/shaft and engine did not experience a sudden stoppage. But some of it was trapped on a propeller blade (I have a 4-blade wheel) until I put into reverse and then the net fell off.

For the reasons mentioned about getting cut while bottom cleaning - I don't like the razor disc types. The "scissors" style like "Spurs" has a curved enclosed cutting edge and it is very difficult to get your fingers in there to get cut. So I have never ever gotten injured while scrapping the prop/shaft/Spurs area of the boat.

Biggest problem with the "Spurs" is you need the free shaft space between the propeller hub and whatever is on the other side (hull/cutless/strut). That is why the company also sells a "spacer" for your transmission/prop shaft coupling/flange to move the prop & shaft aft to make room for the "Spurs" unit.

This could also be a problem with boat that have the propeller in an aperture in the rudder/hull. You cannot move the propeller any further aft without hitting the rudder.

All in all, I am very pleased and happy with the "Spurs" - so much so that I carry a second one as a spare in case somehow the installed one breaks. There are limits on how big or tough a line it will cut and when it cut a 1 inch thick line once, it did damage the nylon bearing in the unit. But the whole unit can be serviced and repaired underwater with no difficulty.

[Pete the Cat]

Originally Posted by Eleebana

Does anyone have any real world experience of how effective line cutters are with feathering props?

Been using my Shark two piece with my three blade AutoStream prop for about 15 years with no problems. Works every time. No maintenance besides cleaning.

[Melkal]

I have not had good luck at all with my serrated disk cutters on a twin engined powerboat. I think they are shaft sharks, from Hamilton Marine. Three dives last year, a bunch of pot warp tightly wrapped. The northern cold waters are wall to wall pots, no regard for marked channels. Damariscotta River, st johns river, are the worst ever. Can't fault anyone for trying to make a living, and I hate to wreck their gear, but I don't have a kayak.

Considering paying the price for spurs. Chop, chop.

[Target9000]

Originally Posted by Melkal

I have not had good luck at all with my serrated disk cutters on a twin engined powerboat. I think they are shaft sharks, from Hamilton Marine. Three dives last year, a bunch of pot warp tightly wrapped. The northern cold waters are wall to wall pots, no regard for marked channels. Damariscotta River, st johns river, are the worst ever. Can't fault anyone for trying to make a living, and I hate to wreck their gear, but I don't have a kayak.

Considering paying the price for spurs. Chop, chop.

I hate when they put pots in channels. On the lake where we sail they also have no regard for placement. And whats worse we see pots regularly buoyed by black floats, commonly black nerf footballs! Impossible to spot.

[4HMainer]

Originally Posted by Melkal

I have not had good luck at all with my serrated disk cutters on a twin engined powerboat. I think they are shaft sharks, from Hamilton Marine. Three dives last year, a bunch of pot warp tightly wrapped. The northern cold waters are wall to wall pots, no regard for marked channels. Damariscotta River, st johns river, are the worst ever. Can't fault anyone for trying to make a living, and I hate to wreck their gear, but I don't have a kayak.

Considering paying the price for spurs. Chop, chop.

Christensen, Fleming, the Royal navy and the RNLI have all replaced spurs with quicKutters not so much chop chop as shave through, and no maintenance.

[cat man do]

Christensen, Fleming, the Royal navy and the RNLI have all replaced spurs with quicKutters not so much chop chop as shave through, and no maintenance.

And no ability to chop nets or other rubbish either

[4HMainer]

Originally Posted by Melkal

I have not had good luck at all with my serrated disk cutters on a twin engined powerboat. I think they are shaft sharks, from Hamilton Marine. Three dives last year, a bunch of pot warp tightly wrapped. The northern cold waters are wall to wall pots, no regard for marked channels. Damariscotta River, st johns river, are the worst ever. Can't fault anyone for trying to make a living, and I hate to wreck their gear, but I don't have a kayak.

Considering paying the price for spurs. Chop, chop.

Originally Posted by cat man do

And no ability to chop nets or other rubbish either

Not sure where you get that information from? but it is not the experience of the many commercial users I'm afraid. They quite happily chop through net, rope and they've also cut stainless steel wire, but they do have a problem with chain. They were trialled by the UK lifeboat service for more than a year before they decided to remove spurs cutters from their whole fleet, so maybe ask them if they work?

[4HMainer]

Originally Posted by cat man do

And no ability to chop nets or other rubbish either

They're an Australian (Perth) invention as well! (just noticed you're from Brisbane)
ask these guys for some references locally
Stella Marine - Marine Servicing, Engineering & Refits, Brisbane, Australia

[dirkdig]

Has anyone fitter a line cutter to yanmar sd50 sail drives with Gori folding props?

[osirissail]

Originally Posted by 4HMainer

Not sure where you get that information from? but it is not the experience of the many commercial users I'm afraid. They quite happily chop through net, rope and they've also cut stainless steel wire, but they do have a problem with chain. . . .

Likewise, I am not sure where you got your information about the QuicKutters - from their own webpage they are quite specific that they do NOT chop or even cut line/debris but instead "shave" through it strand by strand as the propeller rotates. That's how the ss wire was severed, strand by strand and not chopped.

But the most interesting thing about the QuicKutters is as posted at: H4 quicKutter shaft rope / line cutter

"Fitting does require the removal of the prop and the spool is machined to suit each individual drive to a pre determined length and diameter. Once fitted to the prop the cutter is then adjusted to run close to the spool. Debris can not build up against the bearing carrier with the cutter in place and in only one case has a cutter been broken. This was as a result of catching chain. The vessel was the Halmatic built Falmouth pilot boat."

Whatever the cost of the unit itself you have to add the cost of custom machining at a metal machining shop. That has the potential to become very expensive over and above the cost of the unit.

Maybe for commercial and larger vessels this system is better, but for private recreational vessels, IMHO, the unit and its need to be custom fitted and machined to fit would make it less than a serious competitor to the Spurrs or even the "razor" disk-style units that are complete right from the box and easily installed by the boat owner without the need for professional machine shop assistance.

One potential problem with any "scissors" style cutter is the problem of snagging something metallic rather than fiber/nylon type material. An ordinary "scissor" will cut paper/twine fine but not do to well against a metal bolt or rod (e.g., chain). Then you could get a sudden stoppage of the engine if you encounter a metal or non fiber material with subsequent damage to transmission, etc.

Blades/razor type cutters would just ignore non-fiber materials so you might get less than sudden stoppage.

Like most things, "for boats" you need to evaluate what your requirements and needs are and pick the style/type that fits you.

Here is a photo from the above link showing the "shaving" . . .

[annk]

We have had a 'stripper' Ambassador Marine - Home of the Stripper Propeller Protector for the last twelve years. I cannot speak too highly of it, at least 4 times it has saved us from rather nasty situations.
It has to be serviced whenever we haul the boat, the service kit is around $40 I think.
Wouldn't sail without one now...

[osirissail]

The "Stripper" appears to be a good improvement on the "scissors" type cutter, and looks like it takes less room to do the job. They even advertise versions for "Saildrives:" Ambassador Marine - Saildrive Stripper Propeller Protector

[cat man do]

Originally Posted by osirissail

Likewise, I am not sure where you got your information about the QuicKutters - from their own webpage they are quite specific that they do NOT chop or even cut line/debris but instead "shave" through it strand by strand as the propeller rotates. That's how the ss wire was severed, strand by strand and not chopped.

Sounds like a slower process than ripping and tearing and hacking and chopping.
I might be wrong but you would think the propulsion system would be overcome by debris before it had a chance to delicately "shave" that debris away.

Whatever the cost of the unit itself

H4 quicKutter prices

you have to add the cost of custom machining at a metal machining shop. That has the potential to become very expensive over and above the cost of the unit.

Maybe for commercial and larger vessels this system is better, but for private recreational vessels, IMHO, the unit and its need to be custom fitted and machined to fit would make it less than a serious competitor to the Spurrs or even the "razor" disk-style units that are complete right from the box and easily installed by the boat owner without the need for professional machine shop assistance.

It does appear to be a sizeable chunk of coin for what appears to be a small piece of metal with a hardened steel blade bolted in the end.

Seeing as I as the end consumer has to employ a machine shop to spin up a tapered "Prop Hub" I wonder how hard it would be to go an additional step and make the metal shaving component as well?
Not that I would, I dont have the space for that device anyway

[4HMainer]

I did say "chop" its true to indicate cut completely. many commercial and leisure users have seen the QuicKutter cut through debris with a shaving action, so it is chopped/cut through, but strand by strand. In practice this is almost instant, but there is less of a shock to the transmission as happens with scissor cutters. The emphasis on shaving is to indicate the type of cutting process.

The nice thing is if the debris has items such as large fish hooks or ss swivels from fishing gear these just slide over the blade and will sometimes leave evidence as scratches or chunks of the blade edge missing but the cutter is not broken and is able to cut the line or rope when it arrives.

QuicKutters were first used by long line tuna boats, who would wrap fishing line with ss traces, hooks and swivels causing damage to bearings, fishing boats tend to catch rope or net with metal gear. Leisure boats often catch discarded nets as well as the usually pot ropes.

What is interesting talking to commercial end users, mainly fishing boats, is that with other cutters they have tried they all experienced breakages of the cutter and the cutter needed periodic maintenance, quicKutters have been on some fishing boats for 4 years without maintenance and they are still working.

In terms of fitting the spool, machining is a simple quick process for any competent marine engineer. Many hundred have been fitted to leisure boats with shafts from 25.00mm / 1" some by DIY installers.

One comment about a slow cut, slow means a 12.00mm rope is cut over about half a turn of the prop on a small shaft, even if it takes a whole turn that is 0.06 of a second so quite quick on a 1000pm shaft.

The spool can be very small it can even be sleeved over the prop hub, it needs less space and actually improves the streamlining of prop and P bracket in many cases, we've even fitted them to surface drives.

It is simple and surely that's a benefit in any marine system as far as wanting to copy it, it has world wide patents granted, and the spool material (ToughRtex) has been developed especially to withstand the pressures and increased temperature as debris winds on.