Harken sheave worn flat

[Davidasailor26]

I noticed the other day that the sheave in one of my jib sheet blocks has a flat spot worn into it-

The block is 7 seasons old. Anyone seen anything like this or have any ideas on how to prevent it? Or is it just routine wear? I checked the one on the other side and it feels like it might have a bit of a flat but definitely not as severe as this one.

Incidentally, if you have blocks like this do check periodically that the set screw on the back of the base is still tight. On both of ours the screw has worked out over time. Once that happens the pin that holds the block to its base works out, letting the front of the block escape, and bending the flange on the back of the block. Here is what the whole base and block look like (with an improvised replacement set screw on the back) -

 

[Ken Cross]

My furler line did the same. In order to make a flat spot, the bearing/bushing must have been stuck.
I suspected salt or other junk kept it from rolling. Now if I could just find a replacement sheave. So far, no luck for me.

 

[Joe]

Why don't you try Harken customer service. Good chance they might replace it. The sheave was not rotating. If you never touch it, wash it, lube it, salt water or not....it still shouldn't do that.

 

[Justin_NSA]

My furler line did the same. In order to make a flat spot, the bearing/bushing must have been stuck.
I suspected salt or other junk kept it from rolling. Now if I could just find a replacement sheave. So far, no luck for me.

I just replaced all of the worn sheaves for my Hood 810 continuous line furler. Got them at Garhauer

 

[Davidasailor26]

Thanks for the ideas. The sheave does spin smoothly when not under load. I have it at home now so I can’t really test it fully loaded. I could try Harken support though to see if they have any suggestions.

 

[Jackdaw]

It's common wear. Rolling sheaves need to roll, so need to be soft enough to generate friction against the line. So they wear, and flat-spot. High tech lines make it worse. It's becoming more common to see those being replace by low friction ceramic rings.

 

[Jackdaw]

PS - its worse on newer boats with non-overlapping headsails. The angle off the roller is usually much higher and tighter than you see on a big genoa.

 

[Justin_NSA]

This stuff might help. Your balls will thank you!

Only one drop of this new conditioner will repel salt, dirt and other deposits to protect, lubricate and condition the bearing surfaces. Reduced friction allows balls to roll freely and evenly, greatly improving traveler performance

 

[FastOlson]

My '88 Lewmar wide genoa sheaves experienced that same failure back in the 90's. Rolled easily when not under load, as others have commented. I still recall my unhelpful phone conversation with a Lewmar tech.... he told me that they did have problems with the axel of that series. So I asked about a solution....... and he said I should buy their newer version.
I pointed out that this was not much of an endorsement, and he relented and sent me two new ones at their wholesale price.

This is in marked difference to Harken, who rebuilt my mainsheet block system at no charge when some of the ss bent under load.

Looking back at my boat's prior usage in salt water, I imaging that salt crystals had jammed up around the axel. Fresh water environment here, and no recurrence of the problem.

 

[jssailem]

have any ideas on how to prevent it?

It is common. My preventive approach is to give the blocks a good freshwater wash and the occasional squirt of liquid soap to help keep the bearings clean and reduce the chance that the sheave will jam in the block.

As Jackdaw shares, the materials are not forever designed. They will wear and will need replacement.

 

[rgranger]

Also happens to fairleads... I replaced all of mine for the furler last season.

 

[Justin_NSA]

Could dirty, abrasive lines be causing some of this?

 

[jssailem]

I suspect that is plausible.

 

[Davidasailor26]

Could dirty, abrasive lines be causing some of this?

Possible I guess. Water where I sail is pretty much all fresh so I don’t think salt is involved. But I don’t really wash the lines other than whatever rinsing they get when the boat is washed. In the case of rgranger’s worn fairlead that makes a lot of sense because the line is meant to slide through the fairlead and causes friction by design. The sheave is meant to spin so there really shouldn’t be any friction involved, until a bit of a flat spot starts and the line slides instead of rolling.

 

[Hunter216]

I checked the one on the other side and it feels like it might have a bit of a flat but definitely not as severe as this one.

I found this point interesting. Logically the one that has failed did actually stop rotating but maybe the sheet on that tack gets used differently. I know that sounds kind of strange so in other words does that sheet get hung up etc where the sheet is pulled through at a faster rate?

 

[Calif. Ted]

Had both the genny cars and Hood furling line sheaves as described on a previous boat, not sure about cause but Garhauer low lead cars and shaeffer furling blocks work well for me now, also a Harken racheting block at the end of furling. The racheting block was suggested by a rigger, just enough tension going out so it's hands free and coming back in much more so it easier.
Garhauer Marine Low Lead Genoa Car
Schaefer Marine Clamp-On Stanchion Furling Block
Harken 75mm Carbo Ratchet Block - Swivel, Becket