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Meridian · 30-04-2009, 23:21

Sea Conquest...I can't answer your "which one is best question", though I firmly believe any is better than none.
However, you accidentally brought up an important point. You state that you have 2.5" of shaft between your prop and keel, and that a zinc "just fits there".
Its important that your shaft gland gets adequate water circulation, for cooling and lubrication purposes. If the zinc, or anything else (like cutters) blocks this water flow into the shaft gland (packing gland), you risk damaging the gland and allowing ALOT of water into the boat.
If you are set on installing a cutter, I would: 1) install as close to the prop as possible, and 2) relocate the zinc. Maybe to the aft-end of the shaft.
Food for thought...
John

svHyLyte · 01-05-2009, 05:50

Joe500--

You might find the following worth a look:

http://www.prop-protector.co.uk/SAIL...acc16d5a90691e

FWIW...

4HMainer · 03-06-2011, 10:53

Quote:

Originally Posted by Meridian

Sea Conquest...I can't answer your "which one is best question", though I firmly believe any is better than none.
However, you accidentally brought up an important point. You state that you have 2.5" of shaft between your prop and keel, and that a zinc "just fits there".
Its important that your shaft gland gets adequate water circulation, for cooling and lubrication purposes. If the zinc, or anything else (like cutters) blocks this water flow into the shaft gland (packing gland), you risk damaging the gland and allowing ALOT of water into the boat.
If you are set on installing a cutter, I would: 1) install as close to the prop as possible, and 2) relocate the zinc. Maybe to the aft-end of the shaft.
Food for thought...
John

As a bearing supplier the distances we work to are.

for soft mounted drive train, where thrust is taken on engine mounts which are rubber.
12.00mm this allows for 9.00mm forward movement and leaves a gap of 3.00mm for water to exit the bearing.

For rigid drives 3.00mm is sufficient to allow cooling and lubricating water to exit the bearing.

1" = 25.40mm for the US readers.

HopCar · 03-06-2011, 11:31

I've had Spurs on my little Maine built lobster yacht for more than twenty years. I've never been stopped by a piece of rope. I have found small pieces of rope trapped in the running gear when I dive on it but it is cut before it can stop the prop. I didn't even know I hit it. I am careful when I work around them. They are sharp. The oysters that love my prop are more of a danger.

SV Demeter · 06-06-2011, 07:56

Dont bother. None of these devices will prevent 100% of prop snags no matter what the manufacturers tell you. If they did they would offer a guarantee. If you absolutlely think you have to have one I would go with either the spurs or shaft shark and keep a good set of gloves on board for when you have to go down there.

My boat came with a spurs cutter and I rebuilt it but if it wasnt already there I would spend my cruising dollars on more important stuff.

I grew up sailing the chesapeake which is littered with pots and I sail mostly at night. I can count on one hand the number of times ive caught one on my prop. Snagged plenty on race boat keels and rudders though.

Keep a good lookout, motor in float free channels, sail more motor less...

zeehag · 06-06-2011, 08:06

only time i found great and dire need for spurs was in fla when the line being used to get us out of a slip into a very strong current actually went around prop..oops... the rest of my time has been not needing that kind of deal ....now i cruise a full keel and attached rudder combo-- havent found any need for spurs or cutters.... btw-- a collar zinc fits the boats with small clearances nicely and allows watr to enter the cutlass and keep the shaft nicely lubed. dont use a streamlined zinc for those-- doesnt work well, as they are larger and longer than the collar type...

4HMainer · 06-06-2011, 09:04

Quote:

Originally Posted by SV Demeter

Dont bother. None of these devices will prevent 100% of prop snags no matter what the manufacturers tell you. If they did they would offer a guarantee. If you absolutlely think you have to have one I would go with either the spurs or shaft shark and keep a good set of gloves on board for when you have to go down there.

My boat came with a spurs cutter and I rebuilt it but if it wasnt already there I would spend my cruising dollars on more important stuff.

I grew up sailing the chesapeake which is littered with pots and I sail mostly at night. I can count on one hand the number of times ive caught one on my prop. Snagged plenty on race boat keels and rudders though.

Keep a good lookout, motor in float free channels, sail more motor less...

This manufacturer doesn't claim to prevent prop snags but explains clearly the approach to damage prevention.
Rope and Line Cutters - A New Development - The Shaver Cutter by Quickwater Marine

Cheechako · 06-06-2011, 09:35

I've often wondered...wouldnt a piece of light line or net be wrapped up in the prop before winding down to the shaft/spur location?
As far as the zinc being too close to the cutlass bearing...I dont think that's really an issue.... try putting your zinc up close and removing all your packing...my bet is it comes out of there like a garden hose!

4HMainer · 06-06-2011, 09:53

Quote:

Originally Posted by Cheechako

I've often wondered...wouldnt a piece of light line or net be wrapped up in the prop before winding down to the shaft/spur location?
As far as the zinc being too close to the cutlass bearing...I dont think that's really an issue.... try putting your zinc up close and removing all your packing...my bet is it comes out of there like a garden hose!

You've hit the nail on the head, this is exactly what happens and is in my view why scissor and discs are of limited help, as the debris will wind and push forwards, it doesn't go into the scissor blades as they suggest in videos (fore and aft) it will be winding at 90degress to the shaft. Try scissors like this and they struggle. This is why the shaver cutter was developed, debris is caught by the prop and it is only caght rope that is the problem, as it winds forwards it meets the shaver angled like a lathe tool, the debris is shaved at this point prevent a build up of pressure and subsequent drive damage.

ViribusUnitis · 06-06-2011, 09:56

Any suggestion how these devices increase fuel consumption, and/or lower sailing speed?

Saltyone · 31-01-2012, 09:48

Sea Shield Marine have come up with a new line cutter called the SALCA (Sacrificial Anode Line Cutter Assembly). It's basically a serrated disc blade cutter attached to a limited clearance shaft zinc. It's the "Bic Razor" of Line Cutters! When the anode is consumed, the whole unit is replaced (no maintenance or corrosion), which makes it a dual purpose unit (zinc anode and cutter combined). It's much cheaper than regular line cutters & can easily be installed before important trips, or as a back-up to your permanent line cutter - "The more cutting power the better!!" ....You need the zinc anyway!
Here's a link to a video clip -
SALCA - Sacrificial Anode Line Cutter Assembly (Patent Pending) - Shaft Zincs

cfarrar · 31-01-2012, 10:22

Our Spurs have worked many times. Only once did they fail to cut a line from the prop. I don't know about the other brands.

More often we snag a lobster pot on the keel or rudder. Usually we free ourselves without cutting the warp. For the other times, we carry a line cutter on a boat hook, a sharp knife, wet suit, snorkel and dive gear. There are places in Maine where you can walk on the lobster pots from one island to the next. The "toggles" don't help. We catch a few every season.

My wife and I have an arrangement. She snags the pots, I jump over the side to free us from the warp, and she makes me hot tea while I'm in the water.