Ways to extend a rappel without passing a knot

Trip coming up needs a 90m rappel, I have an 80m dynamic which should get me to about 85m with stretch. Can anybody think of a good way to extend an rappel without needing to pass a knot. Single line rap. 

Crash pad strategically placed at the base of the route.

Are you leaving your rope fixed?  And will you have a partner with you who also wants to avoid passing a knot?

Send partner down first on single line with a bit of extra cord or slings. Extend and fix one end at the next station, single line rap the other end.

Bring a short rope and tie them together, fix them so the 80m reaches, rap the short rope side until past the joining knot, put a 2nd rap device on 80m and transfer over to that.

Basically an easier version of passing a knot that's also useful on fixed lines where there's 2+ ropes with some knots isolating core shots.

Biner block and single line rap on long end. add pull cord to short end, use slings or draws or whatever to lengthen. Pull cord/slings when at next belay/ground

that guy named sebwrote:

Trip coming up needs a 90m rappel, I have an 80m dynamic which should get me to about 85m with stretch. Can anybody think of a good way to extend an rappel without needing to pass a knot. Single line rap. 

90m?!?   Bring hardware for a new mid-point anchor.

Austin Donisanwrote:

Bring a short rope and tie them together, fix them so the 80m reaches, rap the short rope side until past the joining knot, put a 2nd rap device on 80m and transfer over to that.

This was the first way I thought of doing it.  Though I think the description isn’t super clear.  The short rope is doubled up and fixed just offset from the middle.  Tie 80m rope to short side, then rap on the long side.  Once past the knot use another device on the 80m

Another sorta funky option is to tie a 15m piece to the 80m.  Fix the 15m section, put a rap device on it (don’t clip it to you)  Just below the joining knot (80m side) tie an overhand on a bight and clip it to the rap device biner, then put a second rap device on the 80 and clip it to you and tie off or use a prusik.   So when you go to rap, you start with the top device and once you reach the end the knot will hit the top device.  At that point release the tie off on the lower device and start rapping.  No knot pass, no adding a device mod rap and needs the minimum amount of rope.

To clarify, we are rappelling into seacliffs, we are trying to make something faster and less of a ball ache than passing a knot(so making a new anchor is out). New beta is the rock is extremely abrasive and bad for ropes so will be bringing a 50m static and a dynamic instead to save ropes the ropes, I think this sadly means we won't be able do any sort of possible trickery and will just have to get good at passing knots.

Well only one of you should have to pass a knot.

Tie both ropes together.  Put rap device on lower rope and clip in to it.  Tie a munter just above the knot and clip it to the anchor.  Partner lowers you the length of the top rope.  Then your rap the lower rope.

Maybe you already know, it can be reliable and relatively easy to pass a knot if you can leave something behind that the next person cleans up …. possibly even reuses .., or it just remains up there

1. Attach prusic on rope at a point above rap device with other end tied off with loaded-releasable hitch to locker on belay loop; a long loop of cord is useful but rig so prusic can’t get out of reach until passing the rope-joining knot
2. Rap while tending prusik to bring it with you.
3. When rope-joining knot is as close as practical, let prusic take load
4. Tie catastrophe knot in rope at point well below rope-joining knot
5. Move rap device to below rope-joining knot
6. Release the loaded-releasable hitch to lower self onto rap device
7. Remove catastrophe knot

Continue rap, probably leaving that prusik cord which could become out of reach during step 6

Might take some practice to get lengths / distances dialed. And, be prepared to ascend if things do not go to plan. 

This thread pretty much reviews all the fast knot-passing options I know of, all requiring rappelling on a munter, which is pretty straightforward

Munter overhand feed-through thread