Prussik vs magnus

[Suffolkrafter]

Fell down a rabbithole of knot nerdery this evening.
I'm sure many of us use prussiks for securing tarps to ridgelines and various other uses.
And I'm sure many of us use tautline hitches for making adjustable guy lines. Tautline hitch is a rolling hitch tied to its own standing end, and is very similar to the Magnus hitch. It occured to me this evening that the magnus hitch is just one turn short of a prussik. So has anyone used a prussik tied to its own standing end to make an adjustable guy line? Why do we rarely do this? And conversely, why do we rarely secure a tarp to a ridgeline using a Magnus hitch (or rolling hitch for that matter)? I'm guessing it's just habit or convention?

 

[Nice65]

Before prussik loops became the norm for tree climbers we used to use what I think you’re describing by tying a prussik and using the rope as a huge adjustable loop ie; up over the branch and back down to the carabiner.

 

[Stew]

I suspect the reason that folk use a certain knot rather than another is that the knots they are using work well enough with no major advantage to switching.

I do have guy lines with Prussics for the adjuster. On tents at the peg end. On hammock tarps at the tarp end with the peg end just straight cord - I don’t know if it’ll be tied to a peg or a tree or whatever and for me that’s easier.

When tree climbing, and before owning mechanical ascenders, I wouldn’t use a Prussic as I found they bound up too much. I would use a Bachmann as the krab would help support and make it easier to release and slide. If no spare krab then a klemheist knot. For a long time I was very anti prussic because of this but it’s just finding where it fits.

I don’t use any sort of pussic variant for a ridgeling as I think they slip over time. I use something that can be firmly tied off and usually with a mechanical (pulley style) advantage to increase tension. Your mileage may vary.

 

[Suffolkrafter]

don’t use any sort of pussic variant for a ridgeling as I think they slip over time. I use something that can be firmly tied off and usually with a mechanical (pulley style) advantage to increase tension. Your mileage may vary.

Some kind of truckers hitch?

I wasn't very clear in my original post; I meant using a prussik to hold a tarp in place on an already established ridgeline. I wouldn't use a prussik to tension a ridgeline either, although I suppose it could work.
I was playing around with some horrible, springy cord last night, and found that the tautline hitch (i.e. rolling hitch), held better than either the magnus hitch or the prussik, which surprised me. The last two tended to spring apart a little. And thinking about it, a prussik ideally uses a thinner line on thicker line, which of course can't be done if using it on its own standing end to make a guy line. I find them to be very satisfying knots and love how they all interelate.

 

[Stew]

Sorry, my misreading. Yep, trucker variant.

I guess for the Magnus v Prussic it’s familiarity - Prussic is the commonly known knot and it’s only us geeks who get further into it.