Chain Stopper Installation Questions

[Cheechako]

Originally Posted by deblen

Always use nyloc nuts &/or locktite on SS bolts if possible. SS doesn't stretch like steel & regular nuts can vibrate loose.
That oak will probably last you out,but if you know of a salmon cage mfgr. outfit near you,get a square of HDPE from them. Lasts forever & also great for backing plates also.

Cheers/ Len

In fact SS has nearly an identical Modulus of Elasticity as Steel.

[Scout 30]

Isn't HDPE Starboard?

[Terra Nova]

HDPE and King Starboard would be exceedingly poor choices for a pad under a high load deck fitting.

[thinwater]

Originally Posted by Red Sky

Exactly why I recommended Starboard.

But the stopper in question is a load-bearing design, not an anchor-holder.

[Marqus]

Ok, maybe here's a chance we can all learn something here. I do not doubt those questioning the use of HDPE, but simply want to understand the issue better.

Let's say the OP uses a HDPE/Starboard pad, say 1/2" thickness, in compression underneath the chain stopper.

Bolted through deck and under-deck steel backing plate with four 3/8" bolts.

Now the anchor is out, and the snubber happens to break, so the anchor is loading the chain stopper.

What exactly is the mode of failure of the HDPE pad - does it compress to 1/4" thickness on its forward edge, or melt or breakup or.... anyone with first hand knowledge/experience ?

[Terra Nova]

What it does is act as if it were a greased pad, allowing the chain stopper to slide around on the deck, eventually worrying the mounting holes larger. It will not bond to anything. And you cannot seal it. Horrible choice.

[Stumble]

Originally Posted by Marqus

Ok, maybe here's a chance we can all learn something here. I do not doubt those questioning the use of HDPE, but simply want to understand the issue better.

Let's say the OP uses a HDPE/Starboard pad, say 1/2" thickness, in compression underneath the chain stopper.

Bolted through deck and under-deck steel backing plate with four 3/8" bolts.

Now the anchor is out, and the snubber happens to break, so the anchor is loading the chain stopper.

What exactly is the mode of failure of the HDPE pad - does it compress to 1/4" thickness on its forward edge, or melt or breakup or.... anyone with first hand knowledge/experience ?

HDPE/starboard have almost zero tensile strength, and almost zero rigidity. Basically it sucks as a structural member in almost every alpplication. As an example, the tensile strength of stainless is about 65,000psi for HDPE it's 2,200psi. Yield strength for stainless is 36,000 psi or so, HDPE is 1,890psi.

HDPE is so weak it can't support its own weight, it will eventually cold flow away from the nuts, so over time you have to continually retighten the bolts to keep enough torque on them. Which causes the material to flow away from the bolt heads, so you have to retighten them....

Using HDPE as a backing plate in a load bearing application is worse than using fender washers, and far worse than using a reasonable material like G10, aluminium, or stainless.

HDPE has a lot of great properties and applications, but structural applications aren't one of them.

[Marqus]

Originally Posted by Stumble

...you have to continually retighten the bolts to keep enough torque on them. Which causes the material to flow away from the bolt heads, so you have to retighten them....

I get the fact that bolt heads or nuts will dig in deeper as you tighten up more. Not good.

In the case of the OP, there are no bolt heads/nuts in contact with the starboard pad. The anchor stopper has a base plate, say 2" by 2", and this base plate sits on top of the starboard pad.

So Greg you're saying that when the bolt heads on top of the anchor stopper are tightened, the 1/2" starboard pad under the stopper's base plate will respond by becoming thinner and expanding in size, so you would see its horizontal dimensions increase measurably ?

[Terra Nova]

Sometimes it's actually painful to watch someone try so hard to not get it.

[Island Time O25]

Why reinvent the wheel so to speak? One can usually pick up G10 scrap pieces from a boat yard or marine shop for a few dollars, just ask for them and ye shall find them. I don't see any reason to use anything else at this point both below the deck or above it. When we were installing elec. windlass I went to a carbon mast manufacturing place my marine pro buddy was working at and asked for some G10. The owner was happy to sell me some by weight. It came out a better deal than ordering online, paying for delivery, etc. and I guess he made a little extra over his wholesale cost. At my request he also threw in a bunch of scrap pieces for a few bucks each. I used those to back my cleats and spinnaker pole holders.

[skipgundlach]

We have a couple of those gorgeous stoppers, too.

But it's merely to hold the anchor in the rack; the snubber and the windlass are the load.

Of course, I went to overkill (1" megabraid with a fancy hook I once saw someone identify in a different thread; I bought it at a boat show) on my 5/16G4-to-77#Rocna) in the snubber, but I'm pretty sure that my footprint and security on my windlass would provide a better backup than that pretty chain stopper. I can't imagine what a 2" square footprint would look like under a few thousand/tens-of-thousands pounds of pressure. How thick is your deck?? My windlass bolts are substantially thicker than the 1/4" holes in the AL stopper, too.

You can see some of the reinforcements we did to the windlass, as well as our installation of the AL stopper, here:

Pictures: Flying Pig Refit 2011-2012/Anchor System Refit

Click #s 4 and 7 for the relevant issues.

L8R

Skip

[Marqus]

Originally Posted by Terra Nova

Sometimes it's actually painful to watch someone try so hard to not get it.

I put a hypothetical specifically to explore the limits of the material. Greg (Stumble) answered usefully backed with some good detail.

Questions are a good way to learn; majority of forum members are gracious in sharing their knowledge.

Why answer questions with negative/snide comments?....Be nice, life is short.

[Charlie]

Originally Posted by bytownboy

I am installing a chain stopper made by Anchorlift - a nice skookum looking piece of gear. I need to raise it about 3/4" off deck to have chain flow smoothly and not pull up on stopper when chain tight. As per pictures I plan to put a block of wood under stopper. Will bolt through wood, through stopper, deck and backing plate.

Should I also drill a set of four separate holes through wood and bolt it down to deck and backer plate, or is this overkill?

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)?

My guess is that Home Depot is selling you red oak which is not a marine material it rots. If it was white oak it would be fine. Personally I would use starboard. I think you can get it in Sidney at west Marine. It is a spacer and is fine with a compression load you would have. It will be at leasy as good for taking the abuse of the chain as the oak would be.

[uncle stinkybob]

Originally Posted by bytownboy

I am installing a chain stopper made by Anchorlift - a nice skookum looking piece of gear. I need to raise it about 3/4" off deck to have chain flow smoothly and not pull up on stopper when chain tight. As per pictures I plan to put a block of wood under stopper. Will bolt through wood, through stopper, deck and backing plate.

Should I also drill a set of four separate holes through wood and bolt it down to deck and backer plate, or is this overkill?

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)?

White poly cutting boards from walfart. wonderful stuff, cheap, tough, never rots, very dense. cuts with a saw.

[Charlie]

Originally Posted by Marqus

I put a hypothetical specifically to explore the limits of the material. Greg (Stumble) answered usefully backed with some good detail.

Questions are a good way to learn; majority of forum members are gracious in sharing their knowledge.

Why answer questions with negative/snide comments?....Be nice, life is short.

Perfectly good question. Perfectly rude reply.

My experience with starboard is that it expands and contracts around screw holes so you need to drill the holes larger then normal. As far as thickness goes I have never sen it expand measuraby over that dimension. I have a hard time seeing how it would comptess anymore than a traditional teak or oak block. I have a piece handy I will put it in a vice to see. Also had a piece of white oak. Put them both in a vice. Starboard was 1/4 in. It compressed .25 to .249. When removed no visible compression marks. White oak went from .886 to .763. When removed obvious dents in wood.

I do not think that it has good qualities for a backing plate.