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12-07-2022, 04:52 PM
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#1
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,136
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20mm nylon snubber failure - well not quite.
Noticed the 20mm nylon anchor snubber looking a bit weird.
This is the short daily use one, not the rarely used storm snubber.
Slid the protective chafe tube back and found this.
Rope is still clearly in good condition appearance wise, protected from sun and hose has not chafed through.
It's a new one for me, never seen Nylon do this before.
I spliced this one in Feb 2021
Need to replace more often it would seem.
__________________
Everything on a boat is broken, you just don't know it yet
Full time cruising is repairing boats in exotic locations
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12-07-2022, 08:28 PM
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#2
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Guru
City: Oconto, WI
Vessel Name: Best Alternative
Vessel Model: 36 Albin Aft Cabin
Join Date: Oct 2012
Posts: 2,904
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It looks like chafing damage right at the end of the chafe guard.
pete
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12-07-2022, 09:28 PM
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#3
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Senior Member
City: Ballard
Vessel Model: 1998 RealShips Voyager
Join Date: Mar 2014
Posts: 380
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Could be the chafe guard. It looks leather. My leather chafe guard got hard as a rock with age. The surface was like sandpaper. I wonder if the leather itself caused the abrasion on the rope.
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12-07-2022, 09:29 PM
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#4
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,136
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Quote:
Originally Posted by Mac2
Could be the chafe guard. It looks leather. My leather chafe guard got hard as a rock with age. The surface was like sandpaper. I wonder if the leather itself caused the abrasion on the rope.
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Chafe guard is clear PVC tube
Never had an issue before.
__________________
Everything on a boat is broken, you just don't know it yet
Full time cruising is repairing boats in exotic locations
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12-07-2022, 09:30 PM
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#5
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,136
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New one made.
__________________
Everything on a boat is broken, you just don't know it yet
Full time cruising is repairing boats in exotic locations
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12-07-2022, 09:33 PM
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#6
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,136
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Quote:
Originally Posted by Pete Meisinger
It looks like chafing damage right at the end of the chafe guard.
pete
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It's only because I slide the chafe guard back to see why the lay of the rope looked weird.
The individual strands seemed dry and damaged, 6 inches either side looked perfectly normal.
I think the roller the snubber goes over creates a localised load point.
__________________
Everything on a boat is broken, you just don't know it yet
Full time cruising is repairing boats in exotic locations
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12-07-2022, 11:32 PM
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#7
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Guru
City: Seattle
Join Date: Jun 2012
Posts: 2,991
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Quote:
Originally Posted by Simi 60
I think the roller the snubber goes over creates a localised load point.
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Absolutely. Notch concentration stress. I recall that you're 60+ tons, which can present a big load even on 3/4 inch nylon. Have you experienced numerous strong conditions while anchored since 2021, with lots of wave surge?
On the positive side, the snubber is obviously doing its job of protecting your windlass, and it is sacrificial anyway. Cheap insurance.
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12-08-2022, 01:21 AM
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#8
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Guru
City: Queensland
Vessel Model: Milkraft 60 converted timber prawn trawler
Join Date: Jul 2016
Posts: 5,136
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Quote:
Originally Posted by Mako
Absolutely. Notch concentration stress. I recall that you're 60+ tons, which can present a big load even on 3/4 inch nylon. Have you experienced numerous strong conditions while anchored since 2021, with lots of wave surge?
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Guilty as charged.
Early days of ownership had us going for a longer storm snubber if expecting over 25 knots for any length of time - now it seems 35 has become the new 25.
And, now we have flopper stoppers we have been spending more time in exposed anchorage's - if we are comfortable enough we might as well stay.
Quote:
On the positive side, the snubber is obviously doing its job of protecting your windlass, and it is sacrificial anyway. Cheap insurance.
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Absolutely.
This was the first snubber out of a 300ft roll of new old stock I bought in 2021
A lifetime supply of snubbers for $150.
Still, it was a bit of a surprise to see that hidden behind the hose.
__________________
Everything on a boat is broken, you just don't know it yet
Full time cruising is repairing boats in exotic locations
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12-08-2022, 07:38 AM
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#9
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Guru
City: Rochester, NY
Vessel Name: Hour Glass
Vessel Model: Chris Craft 381 Catalina
Join Date: Aug 2019
Posts: 6,702
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If you start to experience a similar failure again, it may be time to up-size the snubber a bit. With larger line you'd need to make it longer to get enough stretch, but the end product wouldn't be loaded as close to its breaking strength, so it would last longer and you'd be less likely to develop a failure like this quickly (meaning more chance to notice the problem before it fails entirely).
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12-08-2022, 07:55 AM
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#10
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Guru
City: Saint Petersburg
Vessel Name: Weebles
Vessel Model: 1970 Willard 36 Trawler
Join Date: Mar 2019
Posts: 5,971
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Simi - couple thoughts to reduce point load over bow roller:
First, guidance for rope rode in storm conditions is to ease-out some line periodically to move the point load. Easier said than done but wonder if that might help?
Second, for docks with a lot of surge, common to see a loop of chain used at the dock cleat connected via shackle to a thimble on the dockline. Any way to safely (and quietly) eliminate line as it comes over the roller?
I guess 18-months of full time use isn't bad, but that line was further gone than I would have liked too
Thanks for sharing.
Peter
__________________
M/V Weebles
1970 Willard 36 Sedan Trawler
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12-08-2022, 08:14 AM
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#11
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Guru
City: Walkabout Creek
Join Date: Jan 2013
Posts: 9,114
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Is it nylon that heats up and degrades when there is a lot of stretch cycling? Or is that polyethylene? Could that be what degraded to local area?
__________________
MVTanglewood.com
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12-08-2022, 08:27 AM
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#12
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Guru
City: Here and there
Join Date: Oct 2019
Posts: 541
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I’ve read in a few places and from a couple old salts that using hose or plastic tube for chafe is not good. The abrasion of nylon strands as they are stretched and contract under load is a large contributing factor in chafe. The plastic hose prevents water from cooling and lubricating the line at that point. Just a thought.
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12-08-2022, 09:36 AM
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#13
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Guru
City: Seattle
Join Date: Jun 2012
Posts: 2,991
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That makes sense Porgy, but the age old recommendation is to use fire hose, which has a rubber inner liner.
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12-08-2022, 09:41 AM
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#14
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Guru
City: Here and there
Join Date: Oct 2019
Posts: 541
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My understanding is the age old recommendation for old fire hose was because it was cheap or free not because it was necessarily superior. But folks have different experiences.
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12-11-2022, 08:13 AM
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#15
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Senior Member
City: Newport
Vessel Name: Privateer
Vessel Model: Kadey Krogen 52
Join Date: Jun 2014
Posts: 157
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Quote:
Originally Posted by twistedtree
Is it nylon that heats up and degrades when there is a lot of stretch cycling? Or is that polyethylene? Could that be what degraded to local area?
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For what it is worth, I think stretchability of a snubber is overrated and very hard to calculate. For a given boat, trying to determine just the right diameter of snubber that will stretch but not degrade or break under various wind and wave loads is next to impossible.
The goal is to avoid shock loads at the limits of swing or bucking at anchor. And those shock loads are only an issue under storm conditions. In normal conditions, the lifting of the chain absorbs any shock loads, not the snubber, so there is no need to select a snubber diameter that provides stretch. And one that stretches under normal conditions will degrade rapidly with any conditions above “ normal”.
The desired strength of a storm snubber can be roughly estimated based on an assumed wind speed and boat displacement, etc. But then, one would want to add a safety factor, erring towards not breaking, which would reduce stretch. Sharp bends and splices would all add to reducing the ultimate strength and would need to be added to the equation. So one might select a storm snubber that will stretch at 50 knots, but what will it do if the winds are 70 knots?
Our boat is around 45 tons and we have 7/16” chain and a 1 1/8” 12 plait snubber. Our snubber runs from the deck to a bow eye and then to the chain via a soft shackle. So about 12’ long. I have gone in the water to watch chain and anchor behavior under various wind and depth conditions.
In 10’ of water with 70’ of chain out ( from the end of the snubber, so 7:1) it takes 30 knots of wind or better to lift the chain completely off the sea bed, and then there is still a fair amount of catenary that absorbs the swing of the boat at anchor, so stretch in the snubber would not be a significant benefit.
Recently we sat through a cold front with 50 knots plus for about 10 minutes. We did swing quite a bit, but the snub at the end of each swing was mild and I doubt we ever stretched the chain taught.
I selected 1 1/8” so that even with bends, splices and wear it is still much stronger than the chain. In a choice between ultimate strength and a little stretch ( but not too much) I go for ultimate strength.
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12-11-2022, 08:24 AM
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#16
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Guru
City: Walkabout Creek
Join Date: Jan 2013
Posts: 9,114
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Quote:
Originally Posted by Porgy
My understanding is the age old recommendation for old fire hose was because it was cheap or free not because it was necessarily superior. But folks have different experiences.
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I have been using nylon hydraulic house sleeving. It's robust yet flexible, readily available at any hydraulic shop, and reasonably priced.
__________________
MVTanglewood.com
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12-11-2022, 09:13 AM
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#17
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Guru
City: Here and there
Join Date: Oct 2019
Posts: 541
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“nylon hydraulic house sleeving”
Some of those products look the same as those sold as marine chafing sleeve and- coming as utterly no surprise- considerably cheaper than the “yacht” stuff. Rather than buying by the foot from Defender when I need a piece, I think I’ll throw a spool of it on the boat for whenever I want it.
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12-11-2022, 10:00 AM
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#18
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Guru
City: Rochester, NY
Vessel Name: Hour Glass
Vessel Model: Chris Craft 381 Catalina
Join Date: Aug 2019
Posts: 6,702
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Quote:
Originally Posted by SailorGreg
For what it is worth, I think stretchability of a snubber is overrated and very hard to calculate. For a given boat, trying to determine just the right diameter of snubber that will stretch but not degrade or break under various wind and wave loads is next to impossible.
The goal is to avoid shock loads at the limits of swing or bucking at anchor. And those shock loads are only an issue under storm conditions. In normal conditions, the lifting of the chain absorbs any shock loads, not the snubber, so there is no need to select a snubber diameter that provides stretch. And one that stretches under normal conditions will degrade rapidly with any conditions above “ normal”.
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It's not as hard as a lot of people make it. Size the snubber to be strong and durable enough, then just make it longer until you're getting enough stretch.
And ideally, when you let out extra chain to allow the snubber to stretch, don't over-do it. If you only let the snubber stretch 20 - 25% before the chain goes tight, you're much less likely to have a snubber failure. And if you see the chain going tight, you have an indicator that you're using up all of your available stretch and either need to make the snubber longer or larger.
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12-11-2022, 01:05 PM
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#19
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Guru
City: Walkabout Creek
Join Date: Jan 2013
Posts: 9,114
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Quote:
Originally Posted by Porgy
“nylon hydraulic house sleeving”
Some of those products look the same as those sold as marine chafing sleeve and- coming as utterly no surprise- considerably cheaper than the “yacht” stuff. Rather than buying by the foot from Defender when I need a piece, I think I’ll throw a spool of it on the boat for whenever I want it.
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I have suspected they are the same.
__________________
MVTanglewood.com
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12-12-2022, 01:15 PM
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#20
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Senior Member
City: Green Cove Springs FL
Vessel Name: Shellerina.com
Vessel Model: Mainship 390
Join Date: Jul 2020
Posts: 166
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Here is a pic of my snubber with a rubber shock absorber in-line:
https://shellerina.com/2020/09/21/splicing-8-plait/
I really believe it helps in the job a snubber is supposed to do.
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