uni and clinch knot have failed so far

what kind of knot are you tying? line to lure? braid to fluro? i can help you as can many others on here. you'll get  a lot of answers but i'll give you the basics. Are you tying braid to lure or mono to lure or fluro to lure. I suspect I know the answer already.

CXX as in P-line CXX? I've always tied a palomar but can't imagine either of the knots listed failing with that stuff either, it's one of the strongest (but also thickest), lines out there. 

I use a clinch knot in baits up to 6oz with it, so I'm not sure what you have that is failing. 

you are not tying your knots properly, those 2 knots work very well

Uni has never failed me. Never.

Most well tied knots should hold just fine with CXX.   Take your time and make sure you tie a good knot, it is one of the most important fundamentals of fishing, while you're at it make sure the hook is sharp also.

4 hours ago, Stingray23 said:

Uni has never failed me. Never.

Same here.  Although I have some CXX, it hasn't been spooled yet.  I use the Uni on mono, co-polymer, fluorocarbon and braid.  Never a problem.  I've straightened out jig hooks with the Uni and 30# braid.

I use the improved clinch with .014 CXX and as long as I lubricate it, it cinches down perfect.

Both those knots work very well, as do many other knots. I suggest you spend time practicing off the water until you are confident you are tying any knot correctly on the water. There are tons of videos available online as references.

I've been using #10 cxx for a couple months now as a cheaper alternative to yozuri hybrid. It's only as  a leader, but that means I have to use 2 knots. My joining knot is the albright special and my terminal knot is the uni. Both haven't failed yet. Unless I've purposely made it fail when getting a bad snag. Even then it still takes way more force than I feel it should to break the line. 

OP??? You out there?

I have been using cxx for the last 6 years as a main line and leaders.  I use 10 pound cxx moss green as a leader all of the time. A properly tied palomar knot, wet down before clinching, should almost never fail. That has been my go to terminal end knot along with the Trilene knot.  I use backing on every reel I own. So every reel has a uni to uni between the backing and main line. I use a leader on over half of my rods so there is another uni to uni between the main line and the leader. I have no problem with those knots. 

Every fishing knot will work just fine if it is properly tied, but "If it ain't perfect, it ain't good enough".

Try the 16/20, also known as the Pitzen Knot or Duncan Knot.

 

pitzen will work when all else fails…..that's what Shaw Grigsby says.

uni to uni works well, palomar does too, uni and clinch with six wraps broke at the knot in a snag

I use the San Diego Jam for every type of line now with absolutely zero complaints.

I use 20lb for swimbaits and a UNI knot, never had any issues. If I ever respool with different line I may downsize to 15lb, I've snagged one swimbait deep from shore so far and trying to break off was an ordeal. I can't imagine you would be unexpectedly breaking that stuff unless you are using a really small diameter for the application (like 6lb for jigs or something). 

Never had a problem with Palomar knots. Use it for just about everything

I have used the Uni Knot, Palomar Knot, and The Clinch Knot. I've never had any issues with them and find them to be very dependable. What applications are you using them for ? 

Something I havnt seen mentioned. How often do you retie? Knots can get damaged by a variety of factors. I start my day with a fresh knot and at a minimum I will retie after every decent fish.

Try the improved clinch knot or Trilene knot, CXX is mono and very forgiving and easy to tie quality knots when tied properly.

Tom