Dock Construction - Setting Eyebolts into rock

[swist]

I can't think of any other place to ask this question so please feel free to redirect me.

I am rebuilding my saltwater dock on the Maine coast - it was more or less destroyed in the big mid-April Nor'easter. I have noticed that some commercially built docks "help" the pier (fixed part) of the dock stay down on the rocky shore by attaching it with chains to big eyebolts lagged into the rock. This prevents a big wave striking the underside of the pier from knocking it loose.

How are these eyebolts set into the rock? Do they use a hammer drill ( a big one?) and then put some kind of lag shield (like the ones made of lead) into the hole and then use an eyebolt with a self-tapping thread?

Some of the ones I have seen here on old wharfs and piers have huge loads on them and are decades old - there must be some way to get a real solid mounting.

Thanks for any help or redirection!

 

[tashasdaddy]

Re: Dock Construction - Setting Eyebolts into rock

there has to be something out there like the eye bolts the Electric company uses for the guide wire on their poles. in Florida, they screw into the ground, as we have fairly soft soil. but there has to be one that is like a red head concrete fastener. also something that is coming in to it's own for home built docks, is jetting 6" pvc in the bottom. inserting reinforcing bars. and filling with concrete. make a great piling.

 

[Chris1956]

Re: Dock Construction - Setting Eyebolts into rock

Swist, I do not have an answer, other than to say that standard lag and lead sheilds are not a good idea. The rocking of the waves will work them loose. If you could find or create some hollows in the rock big enough to pour concrete and install bolts nuts and washers in the wet concrete, that might work.

 

[BillP]

Re: Dock Construction - Setting Eyebolts into rock

Here in Florida virtually all muni and many private moorings now use screwed in shafts. They drill a pilot hole when doing rock...the hole for a mooring that holds a 50' boat in rock is about 2" dia. Probably the same thing they use up north for docks. I'd think any dockbuilder should be able to clue you in on it.

b.

 

[Bondo]

Re: Dock Construction - Setting Eyebolts into rock

How are these eyebolts set into the rock? Do they use a hammer drill ( a big one?) and then put some kind of lag shield (like the ones made of lead) into the hole and then use an eyebolt with a self-tapping thread?

Ayuh,..............

And setting the anchors into Epoxy helps Alot too.........

 

[burroak]

Re: Dock Construction - Setting Eyebolts into rock

I think the Fastenal Co. has locations all over the U.S. They service the commercial and industrial sector, but they have been very helpful with my little projects. They sell in quantity but can steer you to their customers from whom you can usually buy what you need. Those people also become good resources for your project with tech support (they don't off-shore you, they speak English) Check they out.

 

[studlymandingo]

Re: Dock Construction - Setting Eyebolts into rock

A good strong epoxy is injected into the hole that is drilled by a hammer drill.​

 

[larky]

Re: Dock Construction - Setting Eyebolts into rock

at work I've used something called rock-tite. not sure what it is made of but it mixes alot like tile grout. The box sayes that its designed to hang equipment from concrete ceilings.

 

[scoutabout]

Re: Dock Construction - Setting Eyebolts into rock

I used threaded eye bolts and inserts to hold an 8 x 20 floater tight to a slab of Canadian Shield for about ten years with no signs of loosening. Actually, it was the ramp that was pinned to the shore and the dock was hinged to the ramp. The bay we were on was only a few hundred feet wide and beset by wakeboarders and tubers from April to October going round and round and round (one of the major reasons we sold the place)...so that dock took a good pounding. In the end I became more worried about the rods snapping as I noticed they would flex visibly during extra heavy hits.

Anyway, I was talking about this very topic last weekend with someone who has installed a lot of floating docks into rock and he too isn't keen on threaded method, instead recommending the use of hydraulic cement worked into the holes around nice big pins.