Frog Change-overs

[fuzzy-hair-man]

- attaching the descender BELOW the Croll. (FHM??)

Correct

However, I think rigging the descender above the Croll - rather than simply removing the Croll after replacing it with a third ascender - adds unnecessary complication to the changeover. Dwight explained this method earlier, but to me it seems to have no benefit over removing the Croll.

Just my 2 cents...

I think 'ek' is saying the same thing, ie if he had an extra ascender then he would use this in preference to pulling up rope between his upper ascender and the Croll.

I was just saying the risk of shock loading the Croll would only appear to be present whilst you have only the hand ascender weighted, as soon as you have the rack on the rope (but not yet locked off) your Croll would act similarly to your brake hand below the rack so the danger period for shock loading the Croll may be shorter than it appears at first.

'ek' was observing that if this is the case, then it might be preferable to conduct a change over when an extra ascender isn't availablle by installing the rack between the ascenders. This is because when using the knot to protect you it has to be a fair way (~1m?) below you to allow sufficent room to rig and lockoff your rack, meaning the length of the fall could be significant (or at least relatively scary).
Further(ek's suggestion) the shock load could be minimised by initially pulling up only enough rope to rig the rack (this is not very much at all) then once the rack is rigged(rack is now sort of protecting the Croll from a shockload) pull up enough rope to lock off.

Clear as mud?

[Dwight Livingston]

Are you sure this is the method recommended in Alpine Caving Techniques? The 2002 English edition (p. 165) says: "Install the descender on the rope as close to the bottom of the Croll as possible and lock it off." (emphasis mine)

They describe it just after, in the paragraph at the end of 7.2 (on page 165.) They say to remove the Croll from the rope completely rather than leave it on, but I have not had trouble leaving the Croll on.

Dwight