|
|
25-04-2016, 17:53
|
#61
|
Registered User
Join Date: Jan 2006
Location: North Carolina
Boat: 44 footer
Posts: 953
|
Re: Chain Stopper Installation Questions
Jedi...
I've got envy, I wish my toe rail mounted track went all the way to the bow...
|
|
|
25-04-2016, 18:08
|
#62
|
Marine Service Provider
Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,974
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by Jim Cate
Are you quite sure about this bonding issue? I'd think that one could bond a chunk of 6061 Al quite securely, and that it would make a fine mounting pad or backing plate. I've used such before without problems, although an isolating gasket between s/s and the alloy is a good idea.
Jim
|
Jim,
No question you can use aluminium plate though I would go with a higher corrosion resistance alloy than 6061 and take the trade off for the rigidity.
But..... And this is nit pickie...
G10 is better in compression lighter, has no corrosion comparability with stainless bolts, is cheaper, and can be tapped.
I have installed a lot of aluminium and stainless backing plates over the years, but by preference I won't use anything but G10 or the equivilant carbon plates anymore. It's just so good at what it does it has become hard to justify using anything else. Luckily it has become so ubiquitous that you can find it laying around as scrap in most boat yards.
I am not sure why there is so much general resistance to the stuff. It's almost textbook ideal as a backing plate. It's so good, even carbon plate is difficult to justify in most applications, the few grams of weight and the marginal stiffness gained isn't worth the conductive issues of carbon. Which is why A-Cats generally use G-10 as backers.
__________________
Greg
- If animals weren't meant to be eaten then they wouldn't be made of food.
|
|
|
25-04-2016, 19:13
|
#63
|
Marine Service Provider
Join Date: Sep 2008
Location: Victoria B.C.
Boat: Wauquiez Centurion 32
Posts: 2,874
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by funjohnson
We just use a chain hook attached to a cleat with a few feet of dyneema.
|
What a snubber should do is stretch under load. Dyneema does not stretch like nylon 3 strand. Should be a lot longer as well.
|
|
|
25-04-2016, 19:17
|
#64
|
always in motion is the future
Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 18,864
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by mitiempo
What a snubber should do is stretch under load. Dyneema does not stretch like nylon 3 strand. Should be a lot longer as well.
|
He did not speak of a snubber at all so must be a chain stopper. I agree that his setup is better than what most suggest, which are (sacrificial) snubbers.
|
|
|
25-04-2016, 20:39
|
#65
|
Registered User
Join Date: Mar 2010
Location: Annapolis MD
Boat: Building a Max Cruise 44 hybrid electric cat
Posts: 3,194
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by mitiempo
What a snubber should do is stretch under load. Dyneema does not stretch like nylon 3 strand. Should be a lot longer as well.
|
The dynemma/hook is just our chain stopper. We still use a snubber/hook to limit shock load.
Here's our anchor process:
Release anchor to seabed
Slowly reverse while paying out chain
Hook the dyneema/hook to chain
Back down on anchor
Let off throttle which typically unloads the chain
Unhook dyneema/hook stopper
Attach snubber/hook
Let more chain out until loop of chain between windlass and snubber
reattach dyneema/hook stopper
|
|
|
25-04-2016, 21:01
|
#66
|
Marine Service Provider
Join Date: Sep 2008
Location: Victoria B.C.
Boat: Wauquiez Centurion 32
Posts: 2,874
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by funjohnson
The dynemma/hook is just our chain stopper. We still use a snubber/hook to limit shock load.
Here's our anchor process:
Release anchor to seabed
Slowly reverse while paying out chain
Hook the dyneema/hook to chain
Back down on anchor
Let off throttle which typically unloads the chain
Unhook dyneema/hook stopper
Attach snubber/hook
Let more chain out until loop of chain between windlass and snubber
reattach dyneema/hook stopper
|
I understand.
|
|
|
25-04-2016, 23:05
|
#67
|
Registered User
Join Date: Aug 2010
Location: NSW Australia
Boat: Traditional 30
Posts: 1,980
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by bytownboy
Snip
I am using oak as that is the most suitable wood I have handy - is there a better material to use that is fairly easy to obtain (small town Vancouver Island but Home Depot not too far away)?
|
One of the most under rated pieces of load spreading materials is cheap nylon breadboards available at most two dollar shops. They are very tough, relatively cheap and require no ongoing painting, sanding or polishing. One or two (laminated) of them might be a very easy option.
__________________
Cheers
Oz
...............
|
|
|
26-04-2016, 07:29
|
#68
|
Registered User
Join Date: Jun 2008
Boat: Tartan 40
Posts: 2,460
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by funjohnson
We just use a chain hook attached to a cleat with a few feet of dyneema.
|
++1.
Same on my boat. Why complicate things with another piece of hardware? Much more comfortable having dyneema, a chain hook, and a well supported bow cleat as a backup in case snubber breaks. That rare but possible incidence is exactly when you need a bulletproof, not questionable, attachment
Sent from my iPhone using Cruisers Sailing Forum
|
|
|
26-04-2016, 07:31
|
#69
|
Registered User
Join Date: Jun 2008
Boat: Tartan 40
Posts: 2,460
|
Re: Chain Stopper Installation Questions
And yes the above is a stopper as backup for snubber. I only use it alone for a quick stop in clear weather and no significant breeze or chop
Sent from my iPhone using Cruisers Sailing Forum
|
|
|
26-04-2016, 08:02
|
#70
|
Marine Service Provider
Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,974
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by ozskipper
One of the most under rated pieces of load spreading materials is cheap nylon breadboards available at most two dollar shops. They are very tough, relatively cheap and require no ongoing painting, sanding or polishing. One or two (laminated) of them might be a very easy option.
|
The reason why not to use them is spelled out in some detail in posts above... These plastic cutting boards are HDPE and are junk in this application.
They do make great skid plates for dragging the anchor chain around however.
__________________
Greg
- If animals weren't meant to be eaten then they wouldn't be made of food.
|
|
|
26-04-2016, 08:06
|
#71
|
Writing Full-Time Since 2014
Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 9,569
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by s/v Jedi
He did not speak of a snubber at all so must be a chain stopper. I agree that his setup is better than what most suggest, which are (sacrificial) snubbers.
|
Snubbers are only sacrificial if poorly designed. They should be sized long enough (nearly a boat length) to reduce all loads to within a working load they can endure for years. Chafe is also reduce by the reduced load, and chafe gear manages the rest. Rather like calling tires sacrificial because they only last a few years. Functional would be more apt.
Short snubbers tend to be sacrificial, since they are not long enough to dissipate energy. They chafe, heat, and fail. Very predictable, in fact, unless they are monsterouly strong and used as stoppers, which is also smart and has been suggested.
The thing is to remember that there are 3 classes of snubbers:
1. long and shock absorbent.
2. short, not extending beyond the chocks or rollers and used as stoppers
3. snubbers that are going to fail from chafe or heating
Using a sort bit of Dyneema as a stopper is a completely different case.
|
|
|
26-04-2016, 21:05
|
#72
|
always in motion is the future
Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 18,864
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by thinwater
Snubbers are only sacrificial if poorly designed. They should be sized long enough (nearly a boat length) to reduce all loads to within a working load they can endure for years. Chafe is also reduce by the reduced load, and chafe gear manages the rest. Rather like calling tires sacrificial because they only last a few years. Functional would be more apt.
Short snubbers tend to be sacrificial, since they are not long enough to dissipate energy. They chafe, heat, and fail. Very predictable, in fact, unless they are monsterouly strong and used as stoppers, which is also smart and has been suggested.
The thing is to remember that there are 3 classes of snubbers:
1. long and shock absorbent.
2. short, not extending beyond the chocks or rollers and used as stoppers
3. snubbers that are going to fail from chafe or heating
Using a sort bit of Dyneema as a stopper is a completely different case.
|
No, your snubber will be ripped to shreds in minutes during hurricane conditions. The chafing is internal, inside the rope, amongst the fibers themselves as the snubber stretches. This melts the nylon or polyester until the outer layer of fibers is too thin for the load and it snaps. This is documented many times and everybody should know it and make sure they are secure.
|
|
|
26-04-2016, 21:27
|
#73
|
Writing Full-Time Since 2014
Join Date: Nov 2008
Location: Deale, MD
Boat: PDQ Altair, 32/34
Posts: 9,569
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by s/v Jedi
No, your snubber will be ripped to shreds in minutes during hurricane conditions. The chafing is internal, inside the rope, amongst the fibers themselves as the snubber stretches. This melts the nylon or polyester until the outer layer of fibers is too thin for the load and it snaps. This is documented many times and everybody should know it and make sure they are secure.
|
Again, it comes down to proper sizing. I said that the rope had to be working within the correct range. What you have described is a design error. If the line is working hard enough to heat, obviously it is either too short to absorb the energy (very common fault--one boat length required) or undersized. This is obvious.
I've not anchored in a hurricane, but I have worked with oil equipment moorings in hurricanes, and they are fiber, not chain. It is all about the design.
|
|
|
27-04-2016, 00:43
|
#74
|
Registered User
Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by thinwater
Again, it comes down to proper sizing. I said that the rope had to be working within the correct range. What you have described is a design error. If the line is working hard enough to heat, obviously it is either too short to absorb the energy (very common fault--one boat length required) or undersized. This is obvious.
I've not anchored in a hurricane, but I have worked with oil equipment moorings in hurricanes, and they are fiber, not chain. It is all about the design.
|
I'm not attempting to be flippant with the following, but rather, would genuinely like to know. Where does one look to find the (proven) math, in order to design such?
As common sense would dictate that a snubber which well in 40kts, won't do so in 60kts or 80kts. And one can't easily (if at all) go & swap them out in such conditions.
Especially if it involves, say, snaking out onto the thin bows of a tri's amas under such conditions, in order to switch to a different bridle. Or to replace one which has failed, or is about to.
I know that Yale (& some others) have specially designed mooring pendants for attaching one's boat to a mooring in heavy weather. But that's a bit different than a snubber. In terms of both; design, & materials used.
Not to mention the cost of said pendants. Ouch!
__________________
The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
|
|
|
27-04-2016, 07:10
|
#75
|
always in motion is the future
Join Date: Feb 2009
Location: in paradise
Boat: Sundeer 64
Posts: 18,864
|
Re: Chain Stopper Installation Questions
Quote:
Originally Posted by UNCIVILIZED
I'm not attempting to be flippant with the following, but rather, would genuinely like to know. Where does one look to find the (proven) math, in order to design such?
As common sense would dictate that a snubber which well in 40kts, won't do so in 60kts or 80kts. And one can't easily (if at all) go & swap them out in such conditions.
Especially if it involves, say, snaking out onto the thin bows of a tri's amas under such conditions, in order to switch to a different bridle. Or to replace one which has failed, or is about to.
I know that Yale (& some others) have specially designed mooring pendants for attaching one's boat to a mooring in heavy weather. But that's a bit different than a snubber. In terms of both; design, & materials used.
Not to mention the cost of said pendants. Ouch!
|
Exactly, if the snubber survives hurricane conditions, then it does not do it's job during "normal" conditions. It must stretch to absorb the shocks and this stretch is what does the internal chafing. If you go up in size, or change to Dyneema, then it may not break during a hurricane but it also doesn't do it's shock absorbing in 20-25 knots of wind.
|
|
|
|
|
Thread Tools |
Search this Thread |
|
|
Display Modes |
Rate This Thread |
Linear Mode
|
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
|
Advertise Here
Recent Discussions |
|
|
|
|
|
|
|
|
|
|
|
|
Vendor Spotlight |
|
|
|
|