I reached out to the internet for some more info on sheave and rope sizes. I stumbled upon a Marlow website which was loaded with technical details. They had a FAQ section and then a submit your own question section. Here is their answer.
We normally say the ideal groove is one that has a width around 10-15% bigger than the rope diameter and has a semicircle profile. The reason for this is that it supports the rope's shape without causing abrasion or distortion. If the groove is too small then the rope rubs against the sides when entering and leaving the sheave and is squeezed, this causes abrasion and can accelerate rope wear. If the groove is too big it allows the rope to distort and flatten as it enters the sheave, this will cause more internal abrasion and so accelerate fatigue. V grooves are normally used where the rope, or wire, is driving the sheave (or vice versa). In this case the 'V' serves to increase the friction between the rope and the sheave at the expense of rope life. I hope this explains things. Regards, Paul Dyer | Technical Manager WWW.MARLOWROPES.COM So there you have it. As previously discussed I'll be having the sheaves made with a 1/2" groove. I'm willing to trade off slightly reduced service life for the versatility of a larger groove. Hopefully this helps someone else. Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Jan 23, 2018 7:41 PM, <captain_j...@cox.net> wrote: > Josh, > > > > I use the term stopper as a generic for sheet stoppers, halyard stoppers, > jammers, rope clutches, or almost any kind of mechanical cleat (except a > cam cleat. I call those cam cleats). I have some really old Schaefer rope > clutches that work just fine. They hold 3/8” or 10mm line well, 7/16” most > of the time too. > > > > I don’t think there is any serious concern if the sheave is slightly too > large. Yes, the halyard will be slightly flattened, as it will not be > supported quite as well, but as long as the difference is only 1/8” or so, > it’s not an issue. A serious mismatch (1/4” or more) might be cause for > some concern, but it would be the long term damage from being repeatedly > flattened and reshaped as the line runs over the sheave. > > > > Jake > > > > *Jake Brodersen* > > *C&C 35 Mk-III “Midnight Mistress”* > > *Hampton VA* > > [image: cid:image001.png@01D2F43E.567E4070] > > > > > > > > *From:* CnC-List [mailto:cnc-list-boun...@cnc-list.com] *On Behalf Of *Josh > Muckley via CnC-List > *Sent:* Monday, January 22, 2018 21:42 > *To:* C&C List <cnc-list@cnc-list.com> > *Cc:* Josh Muckley <muckl...@gmail.com> > *Subject:* Re: Stus-List Masthead sheaves C&C 37+ > > > > Halyard stopper? What's that? Haha, no really what's that? Stopper > balls? Or jammers? > > > > You're right though 3/8ths is almost too small for my winches. So smaller > is pretty unlikely. But bigger might be nice, particularly if it becomes > necessary to run the taper of a core to core eye splice. > > > > The 3/8ths sta-set I have for my spin halyard is almost too small at ~5000 > lbs break strength. I really like to make sure my lifting rigging is > sufficient for climbing standards. > > > > I guess my question is, is there any disadvantage to running smaller line > in a big sheave. > > > > Josh >
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