Figure 8 for 1/2" rope?

LordFarkwad

Active Member
Black Diamond, Fusion, etc...all of the ones I can find specs on say they are good for up to 11mm or so rope diameters.

Are there any that are good for 1/2" rope? Or will pretty much any work, even if the spec says to use smaller diameters?
 

climbstihl

Well-Known Member
I have one by camp (I think) which is pretty small. It works very well with 1/2". It could even use a little more friction sometimes.
 

LordFarkwad

Active Member
I've used my mini 8 on 1/2" double braid before and it works ok.
What does 'ok' mean? As in, if you were to use it on whatever it is spec'd for, what behavior would be different?

I have one by camp (I think) which is pretty small. It works very well with 1/2". It could even use a little more friction sometimes.
I've not searched yet for this one, but does 'pretty small' mean <5-6" long? That's the long dimension of the couple I've looked at (the Fusion and the Black Diamond, specifically).
 

Z'sTrees

Well-Known Member
I guess I'd say 11mm fits better and is easier to lock off, etc. I believe rock Exotica rates it on 8-13mm ropes.
I really dont descend very often on an 8, but I keep it on my saddle just in case. I do use it for a redirect pretty often though.
 

Tom Dunlap

Here from the beginning
I quit using a F8 when I read tests the showed the Munter ha d ore friction. I always carry a large ISC Mongoose HMS biner on my saddle. It does so many things. An F8. Only does one thing
 

LordFarkwad

Active Member
A local guy who is about my same size said that he uses it to take heat off his rope runner on long (~100' or so) descents. My RR feels perfect except if it gets hot, then it won't lock up instantly on a hard stop. I don't mind it, but he saw a video of me descending and said he will - rarely - use an 8 to help with that.

He also uses one for a quick little redirect. Showed me how during a training morning a few weeks ago, for a limb walk.
 

climbstihl

Well-Known Member
I've not searched yet for this one, but does 'pretty small' mean <5-6" long? That's the long dimension of the couple I've looked at (the Fusion and the Black Diamond, specifically).
It's around 4.7" long. Also, the end is tapered, not sure how that affects the friction or the rating (of which there is none, I don't know if it even is rated, I havent even seen one online that looks like mine).
Also, if I soft lock with my 1/2" 16 strand, it will slip, adding only little friction.20190609_201814.jpg20190609_201834.jpg20190609_201906.jpg
 

LordFarkwad

Active Member
It's around 4.7" long. Also, the end is tapered, not sure how that affects the friction or the rating (of which there is none, I don't know if it even is rated, I havent even seen one online that looks like mine).
Also, if I soft lock with my 1/2" 16 strand, it will slip, adding only little friction.View attachment 60293View attachment 60294View attachment 60295
Aaahhhw shucks, you didn't hafta go measuring on account of me! Thanks, man! That's nice and compact.
 

Woodwork

Active Member
I have one of these big stainless steel figure 8 descenders, and it's rated for 11mm to 16mm ropes.
About $35 on Amazon.
Curious how that compares with an aluminum F8. Do you notice any performance difference as it gets hot?

I know from welding that SS is one of the least thermally-conductive metals, while aluminum is one of the most conductive...plus a black finish should radiate heat a lot faster than shiny "silver"...

In use, I would expect the SS version to get hotter faster locally where there's friction while the rest of the F8 should remain cooler (at least until it reaches equilibrium) and once it gets hot all over, it should take quite a bit longer than aluminum to cool down ... whereas the alum version should get hot all over pretty fast and dissipate the heat faster. On the other hand, the downside of dissipating heat faster is that it will also dump the heat faster into your hand (or the rope) when you touch it...when welding steel or SS, you can often pick up the piece (away from the weld) right after welding, but if you try that with freshly-welded aluminum, even though it ain't glowing orange like the steel, it'll stick to your hand like a steak sticks to a red-hot pan and burn you bad in the blink of an eye...it's almost like a capacitor the way aluminum discharges heat through conduction...only gold, copper and silver conduct heat better. I'm guessing this is one big reason why they won't make Unicenders out of SS.
 
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Mowerr

Well-Known Member
Only when I think I might need it. I use that monster mostly for rigging purposes. Sometimes I descend on it after rigging with it, just to hear the crowds scream, "We're all gonna die!" and to taunt the safety police. I'm probably going to burn in Hell for it.
LOOK WHAT JESUS DID !! LOOK WHAT JESUS DID!!
 

JeffGu

Well-Known Member
...only gold, copper and silver conduct heat better...
Yes, silver/copper/gold in that order... but among common metals used to make such things:

1Copper223
2Aluminum118
3Brass64
4Steel17
5Bronze15

And, yeah... SS has more thermal mass, so stores heat better, aluminum has more thermal conductivity, so dissipates heat better... so the SS f8 behaves just as you said. It will eventually get pretty hot if you burn a lot of rope over it, and will take longer to cool down. A splash of beer over it... er... water.... will cool it down instantly, though. It really hasn't been an issue, and the SS holds up to the abuse better than aluminum, by a long shot. I've found that aluminum devices get real hot, real fast and that the SS ones take quite a bit longer to get too hot to handle. Black anodizing would only make a metal absorb radiant heat faster, so doesn't improve anything in this application.

The tradeoff for the high wear resistance is weight, of course. That will be very important to some folks, not so much for me. I'm never in that much of a hurry, so tend to just bundle stuff up on the ground and pull it up into the tree with a haul line when I need it. I'm no production climber, I'm far too old and slow to give a rat's ass about how long stuff takes to do.

I think for climbing applications, the big SS ones aren't very practical. I doubt if a small, aluminum one would do any serious damage to a 1/2" rope for occasional use. Especially in these applications where it is just providing some (not all) of the friction in the system. It is a small bend radius, though. There needs to be a small, aluminum device for just such applications that has nice, fat bend radius parts for the rope friction. I need to think about that some more. Actually, DMM and RE and all those other companies should think about it more.
 

Woodwork

Active Member
Thanks for the reply with your experiences on this, JeffGu.

(FWIW, black objects radiate heat faster, was well as absorb radiant heat faster, than white objects...I wouldn't have believed it if I didn't see it in an experiment in a HS physics class...)
 

southsoundtree

Well-Known Member
A local guy who is about my same size said that he uses it to take heat off his rope runner on long (~100' or so) descents. My RR feels perfect except if it gets hot, then it won't lock up instantly on a hard stop. I don't mind it, but he saw a video of me descending and said he will - rarely - use an 8 to help with that.

He also uses one for a quick little redirect. Showed me how during a training morning a few weeks ago, for a limb walk.

Would a munter-hitch (carabiner on a sling-tether) do the same job? I already have a steel biner on me.

I've never climbed with a F8, except for the F-eight Revolver system, back in the early days of hitch based SRT.
 
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