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25-10-2016, 04:46
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#1
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Registered User
Join Date: Jun 2012
Location: Australia
Boat: Hinckley 49, Evening Star, originally owned by Lawrence Rockefeller
Posts: 282
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Low friction ring vs block
I need to replace my turning blocks for my 70 sqm genoa, they are excellent Schaefer 12series stainless blocks, that have now just worn out.
Rather than spend the approx $1000 each to replace them, I was thinking to use low friction rings instead.
Apart from not looking right, is there any other reason not to use them?
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25-10-2016, 05:40
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#2
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Senior Cruiser
Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 49,084
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Re: Low friction ring vs block
"Low frictions rings" is probably a misnomer. They aren't very low friction.
__________________
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"
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25-10-2016, 06:01
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#3
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Registered User
Join Date: Feb 2013
Location: Bumping around the Caribbean
Boat: Valiant 40
Posts: 4,625
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Re: Low friction ring vs block
Don't do it. The turning angle is too acute and the load on it, with a sail that size, is going to be large. Low friction rings are used almost exclusively in setups where they "deflect" the path of the line more than turn it. I would not consider using one for any application where the turn was greater than 60 degrees, depending on the load and application. Maybe if you have electric winches it won't be an issue (at least to you, not the winch and the lines).
If you end up with new turning blocks, consider getting doubles while you're at it. A lot of utility particularly if you run a kite of some sort.
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25-10-2016, 06:47
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#4
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Registered User
Join Date: Mar 2010
Location: Annapolis MD
Boat: Building a Max Cruise 44 hybrid electric cat
Posts: 3,194
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Re: Low friction ring vs block
You'd at least want to use high tech line striped to the dyneema core where it turns through the ring. Much easier to do on halyard where it stops at the same point every time.
Try Garhauer for some lower cost options.
Matt
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25-10-2016, 06:57
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#5
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Moderator
Join Date: Mar 2009
Location: Denmark (Winter), Helsinki (Summer); Cruising the Baltic Sea this year!
Boat: Cutter-Rigged Moody 54
Posts: 33,750
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Re: Low friction ring vs block
I am a big, big fan of low friction rings, but I would not use them for that application.
They are superb for any line which doesn't move much, OR where there's not much angle of deflection. A turning block -- where you have miles of sheet running in and out AND with a large angle of deflection -- is exactly the wrong place for them.
You want a nice ball bearing block for that. Which means biting the bullet and paying the cost.
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25-10-2016, 08:15
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#6
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Registered User
Join Date: Mar 2013
Location: Oriental, NC
Boat: Shannon 37 cutter-ketch
Posts: 10
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Re: Low friction ring vs block
Find a machinist to rebuild your blocks.
Don Green does great work.
don@dreamgreen.org
dreamgreen.org
__________________
sv Silk
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25-10-2016, 08:51
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#7
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Registered User
Join Date: May 2014
Location: Houston, TX
Boat: Catana 471
Posts: 245
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Re: Low friction ring vs block
Depending on what's "worn out" on the blocks you have, you may be able to get replacement parts to recondition the existing Schaefer blocks fairly inexpensively.
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25-10-2016, 08:59
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#8
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Registered User
Join Date: Dec 2007
Boat: Mahe 36, Helia 44 Evo, MY 37
Posts: 5,731
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Re: Low friction ring vs block
Low Friction Rings will also add a twist to any long lines being pulled through them.
There is very limited places where Low Friction Rings can be used successfully.
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25-10-2016, 09:55
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#9
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Registered User
Join Date: Mar 2015
Location: Boston's North Shore
Boat: Pearson 10M
Posts: 839
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Re: Low friction ring vs block
Friction increases as the radius of turn decreases and as the angle of the turn increases, those stainless turning block probably have a nice large diameter sheave in them and that does reduce the friction.
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25-10-2016, 10:53
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#10
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Registered User
Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
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Re: Low friction ring vs block
In addition to the already stated drawbacks if you go with rings, you'll wind up destroying lines at a pretty rapid & regular pace. Some of this because there's so little bearing surface on the rings, so the lines get point loaded. Thus hastening their demise. So that in pretty short order you'll wind up spending more on jib sheets than good blocks would have cost you.
Odds are the blocks that you have can be rebuilt. Or if not, good used ones are often available. And you can get a set of Harken Black Magic Air Blocks that are more than big enough for under $1k for the pair. So look around.
If you're unsure as to how to rebuild the ones you have, take them apart & post the pictures here. They should be relatively easy to fix, though you may need the services of a professional for part of it. But it can't hurt to try/have us evaluate them.
__________________
The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
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25-10-2016, 11:24
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#11
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Registered User
Join Date: Mar 2011
Location: fl- various marinas
Boat: morgan O/I 33' sloop
Posts: 1,447
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Re: Low friction ring vs block
I agree with those who say contact Shaeffer first. An $800 block should be repairably
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25-10-2016, 14:47
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#12
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Registered User
Join Date: Jun 2012
Location: Australia
Boat: Hinckley 49, Evening Star, originally owned by Lawrence Rockefeller
Posts: 282
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Re: Low friction ring vs block
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25-10-2016, 14:53
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#13
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Registered User
Join Date: Jun 2012
Location: Australia
Boat: Hinckley 49, Evening Star, originally owned by Lawrence Rockefeller
Posts: 282
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Re: Low friction ring vs block
Above are some pictures of the block. I figure I can just reverse the cheeks and put a new sheeve in. Yet I don't think Schaefer make non ball bearing sheaves any more, well I can't find them on the website.
It looks like a resounding no to the rings, so I will accept the forum and not do it.
Adding a double block is a good idea, maybe I could replace the axle bolt with a large shackle and give myself a becket that I can attach an extra block to.
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25-10-2016, 14:55
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#14
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Registered User
Join Date: Jun 2012
Location: Australia
Boat: Hinckley 49, Evening Star, originally owned by Lawrence Rockefeller
Posts: 282
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Re: Low friction ring vs block
Also note in the pictures the wear in the bolt, the sharp edge on the sheave and the small nut which has broken in two!
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25-10-2016, 14:59
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#15
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Registered User
Join Date: Jun 2012
Location: Australia
Boat: Hinckley 49, Evening Star, originally owned by Lawrence Rockefeller
Posts: 282
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Re: Low friction ring vs block
I'm also stuck with this way of attaching the block, unless I hacksaw it off. Hinckley welded this on I suppose to stop it unscrewing itself and or to stop theft. Has worked well for 35 years.
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