Pad eyes for tethers and jacklines - Page 3 - SailNet Community

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > On Board > Gear & Maintenance
 Not a Member? 


Like Tree1Likes
Reply
 
LinkBack Thread Tools
  #21  
Old 07-19-2012
pdqaltair's Avatar
Senior Member
 
Join Date: Nov 2008
Location: Deale, MD
Posts: 2,285
Thanks: 1
Thanked 36 Times in 36 Posts
Rep Power: 7
pdqaltair is on a distinguished road
Re: Pad eyes for tethers and jacklines

FRP can be many things, but G10 is a commonly quoted product (from manufacturer web site):

Tensile Strength 40,000 psi
http://www.wshampshire.com/pdf/Ryertex-Grade-G10.pdf

FRP is my choice for backing plates an such, as I get cut-offs for free, it's easy to work (compared to SS), and can be bonded to the boat for special cases (I've done winches and windlasses that way). Will last the life of the boat.

I will also use Al and SS a times, specifically when thickness matters.
__________________
(when asked how he reached the starting holds on a difficult rock climbing problem that clearly favored taller climbers - he was perhaps 5'5")

"Well, I just climb up to them."

by Joe Brown, English rock climber




To view links or images in signatures your post count must be 10 or greater. You currently have 0 posts.
Reply With Quote Quick reply to this message Share with Facebook
  #22  
Old 07-20-2012
Irunbird's Avatar
Senior Member
 
Join Date: Aug 2008
Location: Charleston, SC
Posts: 293
Thanks: 6
Thanked 4 Times in 3 Posts
Rep Power: 7
Irunbird is on a distinguished road
Re: Pad eyes for tethers and jacklines

I couldn't find much info out there about G10, but it is available through a number of online sources. How easily cut/drilled is it, and what thickness would you guys suggest?
Reply With Quote Quick reply to this message Share with Facebook
  #23  
Old 07-20-2012
Senior Member
 
Join Date: Feb 2012
Location: New Orleans Louisiana
Posts: 2,077
Thanks: 6
Thanked 55 Times in 52 Posts
Rep Power: 3
Stumble is on a distinguished road
Re: Pad eyes for tethers and jacklines

It takes a jig saw with a metal cutting blade, but doesn't take anything special. Carbide blades of course make it easier, but aren't necessary. Drills about like thickened epoxy, so sharp bits and medium preassure, just keep the bit cutting, anymore is unhelpful, any less and you can scorch the bit.

I typically use 1/4" for everything, except where weight is a major concern (unless you have paid for carbon fiber everything weight isn't a big enough concern to worry about here). I would trace the size of the pad eye then add about 1/2" to the profile and cut to that. I also like to knock down the endges with a file or rasp before installing Epoxy and bolt it into place and it will last forever.

Like I said technically you can tap it for the fasteners, but I just don't trust threads tapped into FRP, so I always go with washers and nuts unless there is a specific reason I can't
__________________
Greg Rubin
Attorney
Reply With Quote Quick reply to this message Share with Facebook
  #24  
Old 07-20-2012
Irunbird's Avatar
Senior Member
 
Join Date: Aug 2008
Location: Charleston, SC
Posts: 293
Thanks: 6
Thanked 4 Times in 3 Posts
Rep Power: 7
Irunbird is on a distinguished road
Re: Pad eyes for tethers and jacklines

Thanks, Greg- yeah, I don't like the idea of relying on tapping the plastic and not using washers and nuts!
Reply With Quote Quick reply to this message Share with Facebook
  #25  
Old 07-20-2012
Irunbird's Avatar
Senior Member
 
Join Date: Aug 2008
Location: Charleston, SC
Posts: 293
Thanks: 6
Thanked 4 Times in 3 Posts
Rep Power: 7
Irunbird is on a distinguished road
Re: Pad eyes for tethers and jacklines

Man, is that stuff expensive! I just checked with 4 or 5 different web-sites, and a reasonable sized piece (0.25" x 12" x 24") is at least $100, if not $200. I think I'll stick to stainless!
Reply With Quote Quick reply to this message Share with Facebook
  #26  
Old 07-24-2012
Senior Member
 
Join Date: Nov 2008
Posts: 164
Thanks: 1
Thanked 7 Times in 7 Posts
Rep Power: 7
VallelyJ is on a distinguished road
Re: Pad eyes for tethers and jacklines

U-bolts.
Given that the Chinese make unreliable crap, and Wychard markets to hedge fund managers, the question occured to me: why not use U-bolts? They have ample load ratings and intuitively, I can't see how they differ structurally from pad eyes. With a suitable backing plate, and with nuts and a plate on the exposed side, the only downside I can see is that they protrude, as do non-folding padeyes. And they aren't as finished looking. But they're a whole lot cheaper.
I'd have a welded ring in the u-bolt to clip on to in order to minimize accidental opening.
Does anyone see a practical disadvantage that I'm missing?
Reply With Quote Quick reply to this message Share with Facebook
  #27  
Old 07-24-2012
Senior Member
 
Join Date: Feb 2012
Location: New Orleans Louisiana
Posts: 2,077
Thanks: 6
Thanked 55 Times in 52 Posts
Rep Power: 3
Stumble is on a distinguished road
Re: Pad eyes for tethers and jacklines

Valley,

There are really two major problems I see with what you are suggesting. That really make U bolts unsutable for this.

The first is that a proper pad eye should have at least three, but better four fastening bolts. This allows the loads to be spread over a larger area than is possible with just two.

Secondly a pad eye not only helps spread the force over a larger area in the back, but also helps spread angular loads. As a though experament consider pulling at 90 degrees to the u-bolt, when you do this it is easy to see that the only contact area of the U-bolt is the very small side of the bolt that penetrates the fiberglass regardless of the tensile strength of the bolt itself. Even a large backing plate here doesn't help, since the force is trying to pull the bolt sideways through the glass.

Now if we assume that the backing plate is fixed, and won't pull sideways, we create torque on the bolt. A pad eyes solid front plate helps to distribute this load evenly over the frontal area, while a u-bolt cant.

You suggested adding a plate to the front side, but the problem is unless it is welded to the u-bolt there is too much movement between the bolt and the plate to absorb this side loading.
__________________
Greg Rubin
Attorney
Reply With Quote Quick reply to this message Share with Facebook
  #28  
Old 07-24-2012
Senior Member
 
Join Date: Nov 2008
Posts: 164
Thanks: 1
Thanked 7 Times in 7 Posts
Rep Power: 7
VallelyJ is on a distinguished road
Re: Pad eyes for tethers and jacklines

Greg--
Thanks for giving the idea some thought, and for the reply.
I take your points about the 4 vs 2 fasteners spreading the load, and the 90-degree load. In thinking over your points, it seems that both those features of a padeye seem to address the same issue--that of sideways pull.
It still leaves me wondering whether the benefit is worth the cost. Ultimately, assuming the hardware itself is strong enough, the padeye's resistance to torque protects the substrate it's bolted to--i.e. the cockpit material--from damage due to a forceful pull from a heavy fall. But with an appropriately-sized backing plate, (given nuts/washers/plate on the top/front of the unit as well) would that kind of shock load would lead to seperation from the boat any more than the same backing plate under a proper padeye?
If not, then would the likelyhood of cracked FRP if you fell overboard warrant the expense of a padeye vs a properly-sized u-bolt?
John V.
Reply With Quote Quick reply to this message Share with Facebook
  #29  
Old 07-24-2012
Senior Member
 
Join Date: Sep 2006
Location: British Columbia
Posts: 129
Thanks: 5
Thanked 5 Times in 4 Posts
Rep Power: 9
tjvanginkel is on a distinguished road
Re: U bolts as padeyes

I would think that it would be difficult to stop water from leaking in around a U bolt drilled through the deck. How would you maintain the seal around the outside?
Reply With Quote Quick reply to this message Share with Facebook
  #30  
Old 07-24-2012
Senior Member
 
Join Date: Feb 2012
Location: New Orleans Louisiana
Posts: 2,077
Thanks: 6
Thanked 55 Times in 52 Posts
Rep Power: 3
Stumble is on a distinguished road
Re: Pad eyes for tethers and jacklines

John,

The goal is to spread a torque load out over a larger surface area. With a pad eye, the torque loads are spread both on the front face, and from the backing plate, over a larger surface area, while a U bolt can only spread them from the back. This could lead to a systems failure where the backing plate (farthest from the direction of pull) applies force in a very small area, and the front applies it in an even smaller one.

Think of it like a see-saw. One edge is trying to push into the boat, the other is trying to pull out of the deck. A backing plate only works on one side of the interface .


The real risk of course is not a broken section of the boat, but that general working over time could fracture the hull laminate. Likely below the surface, or below the backing plate. This could lead to a catastrophic failure of the system when it is put under the type of loads generated by someone falling overboard. Of course this is to some extent dependent on the thickness of the hull section it is bonded into.

For the OP on an Olson 30, the laminate where he is talking about is either 1 or 2 layers thick, and that's it. I actually own an Olson 30 and know exacally where he is talking about. So for this installation I think the risk is much higher, than if you were talking about a high strength area where there is a lot of deck thickness to help absorb these loads.


As to value, To me anything that I am going to absolutely have to trust my life too better be the best possible option. There may be places where a U bolt would work fine (places where the load path is more predictable) but in life saving gear, I want it absolutely right.


TJ also raised an issue that I missed. With no flange to bed down, a U-bolt would be more difficult to waterproof. It can be done, by drilling out the core from the back side, filling the larger holes, then replacing this with epoxy. Then redrilling the mounting holes strait through the epoxy. This is the proper way to seal core anywhere you have a core penetration anyway, but then you are relying on just the goo at the backing plate to keep water out. Particularly in a verticle installation there will be standing water in the bolt holes. Which is almost begging for stainless crevice corrosion.
__________________
Greg Rubin
Attorney
Reply With Quote Quick reply to this message Share with Facebook
Reply

Quick Reply
Message:
Options

By choosing to post the reply above you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.




Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Jacklines, again tweitz General Discussion (sailing related) 35 03-01-2009 12:39 PM
Tethers/Jacklines/Harness.... SailChick20 Gear & Maintenance 21 10-06-2008 04:14 PM
Jacklines xort General Discussion (sailing related) 44 08-27-2008 03:23 PM
roll your own tethers janders Gear & Maintenance 33 08-19-2008 05:23 PM
how to on jacklines capt.stu Gear & Maintenance 18 03-08-2008 01:57 PM


All times are GMT -4. The time now is 03:32 PM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.