[novic]

Just a random thought....

My sailing grounds (Georgian bay) consists of a big puddle sitting on top of a granite minefield. Nav hazards aside, lots of pretty anchorages where stern tying or "docking" against a rock face is useful/necessary.

The usual method seems to be looping a line around some large immobile object (tree/boulder). This is not always possible and I've seen some folks pounding pitons/rebar into the rock.

I occurs to me that rock climbers have lots of nifty nuts/cams and other devices for securing to rock faces. Granted a 15000lb boat is a bit different than a 150lb person but these devices are rated for shock loads up 2000-3000lb.

Am I crazy in thinking 2-3 of these devices linked together would provide sufficient holding for a stern tie ? Anyone try this before?

 

[knuterikt]

Where I sail (Norway/Sweden) we often tie on to rocks.

It's common to carry different types of wedges
I use this type a lot - from Fortøyning.no

I also have a kit similar to this

 

[kwaltersmi]

Not sure about the suitability of climbing gear for this application, but we have used plenty of pre-placed/installed d-rings in the granite rocks of the North Channel adjacent to where you are without problem. When doing so, I usually include a secondary anchor off the beam or ensure that the primary anchor is set in such a way that if the shore-tie gives way I won't end up on the rocks.

 

[danvon]

As a (admittedly terrible) climber, I can see this working but have a couple of concerns. First, I'd be a little concerned about the pieces moving as the boat continuously loaded/unloaded the line with wave action, tides, etc. In particular a single piece like the picture shows is prone to coming out of the crack if it is momentarily pushed up out of the narrow spot it is placed in. Unlike an anchor, they are not going to reset themselves if that happens.

A cam (which is a spring loaded device that expands when pulled and jams itself into the rock; I can't post images yet but google for Camalot or Alien) can walk itself further in if rocked back and forth, and make removal hard or impossible. [Of course, if you do get one irreversibly jammed in, the next guy will have a very solid anchor.] That is less of a concern with pieces that do not have moving parts, like hexes, nuts, etc. They are also cheaper than active protection like cams. What works will really depend on the nature of the cracks in the rocks available to you.

If you are planning to use several pieces together, there is a right and wrong way to do it. improper placement can actually INCREASE the load on each piece. Take a look at some climbing sites for tips on how to build anchors/place gear. Also, watch carefully for corrosion if you are on salt water. Having said all this, the static load from an anchored boat is relatively small and the gear should in principle be able to hold it.

 

[pdqaltair]

First, everything Danvon said. I've been climbing for 30 years at a pretty high standard.

1. I would stick to wedges called "stoppers" or their equivalent. Cheap, versatile, durable, and not prone to walking. They are the work horse anchors and you probably need nothing other than 6-12 (anything smaller than 6 will tend to get stuck and are not as strong). Hexes continue into larger sizes. Climbers use many other gadgets, but they are dependent on the crack in front of their face to work with and often need something very specific. I would stick to big stoppers for anchoring.

2. Use wire gate carabiners (no corrosion). No lockers needed.

3. Pulling out with sideways movement is the main problem. The solution is generally to set them as equalized pairs. This will reduce movement, increase strength, and make them easier to remove. But not needed with good placements.

4. Read up and practice. The library should have a book on climbing. Experiment. There is also a huge difference between good placements and poor ones. Good placements are text book in all ways, the marginal placements aren't worth the time they take.

5. Try to keep some steady pressure. No big slack.

6. Do not run the rope though the cable loop. That is a big no-no. It will cut under high load. Use a carabiner.

7. A nice advantage of the nut in the photo above is that the upper loop can be used to pull the nut out backwards, should it get stuck. However, this trick can be used on any stopper (done that), and normally a sharp poke from the bottom with a tool like a large screw driver is faster and more effective. Additionally, that big loop can get in the way. Thus, climbing nuts are not built that way. But it looks valid for the purpose.


Yes, this has been done by many.

 

[novic]

Thanks for the tips!
I think i'll buy a set of nuts and play around a bit with this over the summer. I already have a bunch of carabiners/slings for "ascending" the mast, so should be minimal cost.

As Kwaltersmi pointed out, many of the more popular anchorages already have previously installed permanent fixtures, but I think having these on board will certainly increase our anchoring possibilities.

Have to say, adequate or not, the little bits of wire/dyneema on these things sure looks wimpy compared to the anchor chain holding the other end of the boat...

 

[bobmcgov]

Good advice from PDQ. Actually, most climbing gear is rated to 22 kN -- 5000lbs! And because we're talking life saving applications, you can be sure both the rating and QA are conservative.

Camming devices ('Friends', as one brand is known) are bulky, expensive, and take some maintaining. Each size covers a significant range, but you'd still need a mort of them to cover your likely needs. The type with flexible stems are more versatile & less prone to walking.

Did I mention expensive? The photo above shows roughly $700 USD in cams. You might find some at a swap meet.

Various chocks (nuts, stoppers, hexes ... aka 'passive pro') are available & you could buy an entire set for half the cost of one cam. Light & compact enuf to carry a whole set on one carabiner. A clean stopper placement is very nearly orgasmic. You could hang a Winnebago off of it.

Hexcentric nuts (hexes) were popular for ... no wait, they were never popular. But they sold a bunch of them, and you'll find them for peanuts, and the buggers do stay put once you bash them into place. Also, you can clang them together as a fog bell.

For your purposes, I might advise an esoteric piece of climbing protection called the TriCam. They are stupid-versatile: they cam like a Friend, they wedge like a stopper, you can tuck them into solution pockets....

Bend 'em around edges or corners, they don't mind. Inexpensive, lightweight, compact, and not prone to rust. Why are they so obscure? Because they are tricky to place on lead, hanging from your fingertips; and your second will hate you when she has to remove them one-handed. But that's not a problem on flat ground. I never, ever set out on a multi-pitch climb without four Tricams on the back of my harness.

Finally, don't overlook the possibilities in natural anchors. You can make your own chock by wedging (yes!) a chockstone (or length of wood) into a crack & slinging it. I've rappelled off lots of those. And a tied nylon sling allows you to wedge the knot into a constriction, or to thread a pinch-off.

 

[OldEagle]

As an experienced climber myself, I think pdqaltair hit all the key points. Two in particular I would emphasize:

- "sideways movement is the main problem". In most climbing applications the direction of pull is predictable (down), especially if a runner has been interspaced between the chock and the carabiner through which the climbing rope runs. This will not necessarily be the case when you are setting a chock to support a mooring line--a shift in wind will alter the direction of pull

- "The solution is generally to set them as equalized pairs"--Yes--but it need not be just pairs--you could use 3 or more chocks, each one optimally set to hold pull from a somewhat different direction, but then equalized with a rope or webbing loop. Any decent climbing text will illustrate this--or just Google "climbing protection equalization" for online illustrations