Author Topic: Wall bumpers  (Read 1469 times)

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Offline Garbonzo

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Wall bumpers
« on: October 26, 2008, 11:32:29 pm »
Last winter's discussions of ledge design got stirred up in my mind again recently (as once I finish building doghouses I will once again have time to go fire up the sewing machines).

The design issue I want to particularly focus on is the ledge to rock interface.  On my ledges the wall side fabric gets chewed up pretty fast (duh).  I've yet to deploy the fly (thank god!), but it doesn't exactly have any extra immunity.

Presently the approach on BD, Fish, and probably Metolius is just extra rash guarding, a sacrificial layer to take the beating before the structural fabric starts getting chewed.  My fish has 3" webbing, and the fly has 18 oz VCN.  Yet, despite this, I got a hole due to a fairly shallow blunt edge as there is still a hell of a lot of force concentration even with the extra layer of webbing.  No biggy, but it seams clear to me better can be done. 

1.  Previous posters used clamp on rubber blocks that could even be clamped on the outside of the ledge with bolts and wingnuts.  Neat, but kind of awkward.  Also I don't see someone going out in a storm to deploy them...


2.  Recently I saw a home brew ledge on Ebay with rubber donuts on the wall side poles.  Also neat, but these looked like they would really reduce the packing efficiency, unless of course the could be removed (didn't look like it would be easy in this case).  Also the looking like big rubber washers, thin and flat, so they would just fold over and really not keep the ledge from wearing away against any bump more than 1/2" high.

3.  So I want to propose a cheap option I have yet to see.  Pipe insulation.  Yep, that black closed cell foam crap from Home Despot.  My idea is simply that by putting a layer of squishy stuff over the wall side tubing, the force is spread out more, keeping nubbins and blunt features from creating pressure points.  I'm thinking that in addition to the usual rash guard, you'd have a limp tube of ballistics (or whatever) that would allow the pipe insulation to be slid in (and over the tube).  Packin size would go up, but it would also even reduce chewing of the fly, as the pressure would be spread over a large area of the rock/fly, so there would be less pressure on the fly fabric as the ledge shifted.

Other ideas?  Thoughts?
« Last Edit: October 26, 2008, 11:35:08 pm by Garbonzo »

Offline Mike.

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Re: Wall bumpers
« Reply #1 on: October 27, 2008, 06:59:28 pm »
Hey G,

I had a ledge that lasted nearly 200 bivies and have two others currently in use. Not one is showing signs of heavy wear in that area. The older of those ledges was returned to the mfr and replaced b/c the bed fabric stretched out. The ballistic cloth on the wall side rails looked great. I don't think there's enough consistency in every bivy situation to assume the ledge will rest squarely against the wall. My ledges end up resting against haul bags a bunch of the time. Sometimes a corner will take the brunt. Sometimes a rail.

I would look closely at how you tend to set up your bivis. Is there something there that promotes wear? Not saying this is your issue, but would the manufacturers not include some sort of protective system if this was a chronic issue?

I actually do not want any sort of really grippy thing between my ledge and the wall because I think it will impede the ledge's capability of being adjusted while loaded.

Maybe it's just the way I've been doing things, but IMO there is no need for a bumper. I like the ledges the way they are on the wall side. The burly fabric works perfectly for me.

Cheers.
Say no to limbers, excavators and retro-bolters. No matter how much he smiles.

Offline Mike.

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Re: Wall bumpers
« Reply #2 on: October 29, 2008, 11:01:24 am »
Thought about this more.

I think the lengthier the ledge suspension straps are adjusted, the less force there is on some parts of the ledge. Particularly, the force between the ledge and the wall. I try to have the straps as long as they can be for this reason. Garb, could it be that you generally keep your ledge adjusted short? BTW, how much do you weigh?

Also, I think clipping the non-deployed fly in series with your ledge can reduce the pressure against the wall. That effectively gets the ledge's clip-in point up to a foot or more away from the wall than clipping it directly to a bolt or rivet. (Read: Less force against the wall.) G, do you typically incorporate your fly when setting up?

Jus tinkin...
« Last Edit: October 29, 2008, 11:03:44 am by Mike. »
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Offline marde

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Re: Wall bumpers
« Reply #3 on: October 30, 2008, 10:56:09 am »
Anyone ever thought of a suspension system for two masterpoints?
Because a lot of bivies on El Cap have more than enough bolts for that.
And at least a double ledge would hang way more stable so no worries if only one moves on the ledge.

Offline mungeclimber

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Re: Wall bumpers
« Reply #4 on: November 01, 2008, 06:48:45 pm »
marde, can you clarify?  2 separate suspension points, a la a hammack, seems more stable longitudinally, but inevitably tippy throug the waist of the ledge, i.e. rock face to air direction.  not sure I described that well.

Offline marde

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Re: Wall bumpers
« Reply #5 on: November 02, 2008, 04:30:34 am »
I just thought about hanging the ledge from two points instead of one (horizontaly spaced for ~3-6feet)
so it won't shift just because your partner moves (I'm talking about a double ledge).
You still need the straps in the middle, these just go both to the right and the left masterpoint

Edit to add:
I don't see a reason for this setup beeing less stable than the traditional one in any axis.
« Last Edit: November 02, 2008, 05:40:52 am by marde »

Offline lunchbox

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Re: Wall bumpers
« Reply #6 on: November 05, 2008, 09:47:39 am »
I always try to hang the bags to the outside of the ledge so you can get things out.  So this doesn't me help protect the bed from wear, but I don't see it being very important.

While the corners of my Bomb Shelter show signs of wear, they still look good and fit together just as they always have.   The fabric on the ledge and fly is also in great shape.

I know the ledge doesn't always sit flush with the surface of the wall and can make the damn thing shift around a lot.  When this happens I use my shoes (in good weather) to shim things out and stabilize the bed.

The shoe shims would protect your ledge without any modifications.  You just clip them in and stick them where they're needed.