What do you think about rope cutters

[Tranona]

Depends on what causes the block to come off. The mechanical fastening might fail, for example because of corrosion if there are incompatble materials. It might also come off because the design of the cutters is such that something could be caught up in the blades and not cut. It might also come off because something was picked up that could not be cut (such as a mooring chain), so you would want something to "fail" before the load was transmitted up the line to the gearbox, causing the sort of damage in a post only last week on the MOBO forum. For those who have not seen it, a rope wound its way round the prop and sterngear, pulling the whole sterngear back and shattering the bell housing. Not a pretty sight!

Can't see why having no moving parts as in a disc cutter is a good thing. Try cutting a rope by waving a sharp knife at it randomly compared with using a pair of pinking shears. Of course a sharp knife will cut if there is tension on the rope or if it is cut against something like a chopping board, neither of which situations occur when a prop meets rope, nets or plastic bags.

 

[TigaWave]

No moving parts can work as and active cutter, any debris that is caught is being effectively driven by the engine, it is nearly always tight on the shaft. As it spirals forwards if you place a fixed blade at such an angle that that it shaves into a rope like a lathe tool it will cut using the engine as the power behind the cutting/shaving action.

Look at a lathe, the blade is fixed. If the work is rotated and can then be moved towards the blade you can easily cut metal.

The forces pushing the debris forwards against the cutter are huge, as demonstrated by the number of bell housings that fail when larger engined vessels get debris wrapped.

316 bolt fixings are the weakest link, they should be bedded on an epoxy to prevent any water getting in to cause crevice corrossion, but they will sheer in extreme cases.

 

[Sailfree]

[ QUOTE ]
Initially I went for a cheapo disc type one but it soon seemed to get blunt and I doubted whether it was fit for purpose. I changed it for an Ambassador stripper which has cut cleanly through a trailing rope without my noticing.

[/ QUOTE ]

Snap - initial Seaventures fitted a cheap disc cutter. Ours is a charter boat with many miles per year. After 4 ropes in 1st year I fitted an ambassador at 1st lift out.

Be aware though that rope cutters may not always be the complete answer. The Ambassador has always cut the rope/fishing net but sometimes the remains are still wrapped round the free prop upsetting balance a prop efficiency.

 

[DaveS]

I have a rope cutter; it came with the boat when I bought it about 9 years ago. It's happily chopped through a number of ropes in that time. As to make, well that's a little harder. It looks like a Spurs, but it doesn't have a label, and it's fitted to a saildrive - and Spurs claim not to make a saildrive model...

At the end of last season I found its driving dogs sheared, presumably after hitting something solid - though I have no memory of such. With no acknowledged manufacturer spares weren't an option, so a bit of DIY drilling & tapping followed up by a bit of good quality (i.e. not my) SS welding has (hopefully) done what is required...