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Both my fiancee and myself bought some climbing gear recently and we're planning our first trip to an indoor rock gym this weekend. We decided to practice our knots and belay technique before we went so we rigged some rope to a chin-up bar to practice letting one person hang while the other person held the "brake" position to get used to how it would feel.

The problem is, while I could hold my fiancee just fine, she weighs about 70 lbs less than me and had a really hard time holding my weight, in fact she could barely hold it at all. I'm worried that she won't be able to hold me if I were to fall while climbing. Surely, we can't be the first climbing pair to have different weights...is there a way to fix this? Is there any mechanical advantage of having the "lever" of the top rope much higher than the practice chin-up bar is?

EDIT: From some research, it seems like there may be a difference when top-roping vs. lead climbing? For reference, we will only be doing top-roping for the foreseeable future.

FOLLOW-UP: We just got back from climbing for the first time today at an indoor gym and we didn't have any trouble at all. My partner anchored herself to the ground as mentioned in the answers and the weight wasn't even an issue.

Thanks for any insights!

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Great! I hope you enjoyed your climbing. Did you take an introductory class? –  Mr.Wizard Feb 16 at 2:48
    
Yeah, it was really fun. We did take an introductory class. He went over the basics of belaying and the basic knots needed. –  Blackbear Feb 17 at 14:30
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2 Answers

up vote 7 down vote accepted

In a gym, the toprope will be wrapped over a cylindrical bar. Some gyms have it just over the top of the bar (180 degrees of contact), while others give it an additional full wrap around (540 degrees of contact). In the former setup, a belayer can hold the static weight of a climber who weighs roughly twice as much as she does; the friction between the rope and the pulley keeps it from slipping. In the latter setup, the factor is much larger, maybe 10 or more.

In your chin-up bar test setup, I assume you had 180 degrees of contact. When you say she could "barely hold" your weight, are you describing a situation where she was simply sitting in her harness with her weight hung from her end of the rope? She shouldn't be trying to hold the weight with her hands. Only a relatively small force from her braking hand (below the belay device) should be needed in order to keep the rope from slipping through the device.

If it's in doubt whether your partner's body weight is enough to suspend you, she should anchor herself to a weight or to a carabiner connected to the floor. Ask at the desk and they can show you what they have for you to use and how to use it.

In case she isn't anchored and does get picked up off of the floor, it's extremely important for her not to panic and release the rope through the belay device. Practice having her catch a fall when she's expecting it. (You typically want to practice this about 15 feet off the ground. It should be high enough so that rope stretch can't bring you to the floor, but not so high that a fumble gets you killed.) Even in a real fall where you're 50 feet above the floor, if she stays calm and keeps tension on the brake strand, the worst that will happen is that you'll accelerate down to the floor relatively gently, you'll survive, and she'll be left suspended until someone comes along to help.

For toproping, none of this is as much as of an issue as you might imagine. It becomes more of an issue for lead climbing. Even for lead climbing, I've seen very small belayers competently catch big lead falls by big guys.

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Another helpful and well thought out answer from you in regards to my climbing questions, thanks a lot. You are right, with the chin up bar we only had 180 degrees of contact. It does seem she was braking properly though because she was sitting back in her harness and only using a small force on the belay device itself. –  Blackbear Feb 13 at 3:33
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Alright, there are several different issues here that we must be sure to address. I'll give you my thoughts on each of them.

As before I recommend receiving in-person instruction as there may be serious technique problems at the root of this question.

Sufficient braking friction

A basic requirement is that your belayer is able to easily produce enough friction to arrest any fall you might take, be it one foot or fifty. (I sure hope I never experience fifty on either end of the rope but such things have both happen and are survived by others.) It is concerning for you to say: "she ... had a really hard time holding my weight, in fact she could barely hold it at all." In the mock-up you described it should be easy to merely hold your weight with one hand. Unless your fiancée is quite weak this must be due to the combination or rope, belay device, and braking position. A thin and slick rope will slide through a belay device with much less friction than a thick and used (fuzzy) rope, but the kind of rope you should be using for top-rope climbing (10mm or thicker) usually has enough friction in even the base-model ATC, so if you are using a 10mm or thicker rope first make sure that the braking position is correct.

Braking position

Friction increases as the bend angle in the rope increases and bend radius decreases. The greatest braking force will be possible when pulling your hand(s) tight to your pelvis below the device, to the front. While gripping the rope tightly is important, especially at the moment of catching a fall and for hands that have not yet become strong from climbing, the primary focus should be on bending the rope across the lip of the belay device rather than gripping it more tightly.

Hands should be thumbs-up, that is thumb pointing toward the device, not away from it; NOT like this:

enter image description here

Be sure that your fiancee does not slide her hand all the way up against the belay device. The web of the hand can get "sucked into" the belay device; for a belayer of equal size to the climber this can result in a nasty pinch, but I heard that this happened locally to a new belayer paired with a much heavier climber (much greater size disparity than I believe you and your partner have) and it resulted in serious damage to the hand that required reconstructive surgery. Practice a consistent brake position at least several inches below the device indexed against the body rather than floating in space.

A device with more friction

If the correct braking position is being used and the belay device still does not provide sufficient friction you will need to change something. I recommend the Black Diamond ATC-XP (which I have experience with, though similar designs are available):

enter image description here

The V-shaped grooves greatly increase braking friction on skinny and slick ropes, and should let your fiancee easily hold your weight. Assisted-braking devices (like a GRIGRI) will also provide greater braking force but as I stated in a different post I am convinced that learning to belay starting with one of these devices is a mistake. They may however be a good idea for lead belaying where a size discrepancy exists. (See caveat below.)

Relative weight

If the problem is not lacking sufficient braking force but instead you are lifting your belayer off the ground you will need to attach weight to the belayer. My local gym provides sand bags for this purpose; they have an adjustable "leash" and people clip them to the belay loop (with an attached carabiner) with just enough slack so that it isn't pulling down while standing.

The amount of friction in the effective pulley at the top of the wall will affect the allowable weight discrepancy before this becomes necessary. From experience I know that the tipping point on a large-diameter anchor is right around a 3:2 ratio; if your belayer weighs two thirds or more of what you do it should not be needed.

Consideration for lead belaying

I have limited experience with lead climbing at this time. Nevertheless I can tell you that catching a lead fall is a completely different experience from catching a top-rope "fall." Even a moderate fall by a climber your own size will pluck you well off the deck. Beyond that I shall pass on making recommendations regarding size disparities in lead climbing as I'm simply not qualified. However I wish to firmly impress on any top-rope climber reading this that lead climbing is an entirely different game, even for the belayer. Get well-qualified instruction before stepping into this realm.

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Thanks for your answer @Mr.Wizard, she seems to be holding the brake position correctly because the rope didn't move at all, and it didn't even require a lot of strength on her part to hold the rope in the brake position. The problem was, as you mentioned in your answer, she was just too light and was pulled up in the air when my weight was on the rope. –  Blackbear Feb 13 at 13:16
    
@Blackbear I see. For reference would you mind telling me each of your weights? –  Mr.Wizard Feb 13 at 15:40
    
Sure! I weight 185 lbs and she weighs 115 lbs. –  Blackbear Feb 13 at 16:49
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