What is a sure fire, works every time, never fails way to get the main to unlock?

Disconnect your mast rotator control line first, so you can rotate your mast at least 90 degrees or more, and if you can, park the boat with the bows slightly (30 degrees maybe) off the wind. Pull the halyard up, then rotate the mast th other way for maximum angle between sail head and mast. Then hold the rotator there, release halyard, pull down on the tack with the other hand. That usually works for me. Oh, I forgot to mention, you did spray the entire track and bolt rope with some type of dry silicon lube before you put it up, right? That always helps.

I think this varies by boat and setup. Sometimes it takes a long time to get the system figured out.

On my 20, the best way is to get the skipper behind the rear crossbeam with his foot on the beam and tugging on the halyard. Once the sail has been pulled up an inch, the crew over-rotates the mast so the rotator mast is past parallel with the front beam and while its rotated, he pulls down on the sail.... once it comes down a little bit, the halyard is simply let go of and it comes down super easy.

However, I know Trey's sail requires a mule-team to get off the hook. Again it all depends on the boat.

I am jealous of the A-catters system

Turn boat on side. Walk to mast head, unhook ring ... right boat. Sail comes down, no problem.

RE A cat system. I got down to Tradewinds early so I went over to check out the A cat regatta, there were more than one of them who had trouble getting their rings to "hook up" while putting their sails up and they have the same problems coming down. No perfect solution there.

Yes but I bet none of them had "line tatoos" on their hands where the halyard was wrapped around trying to get that damn thing off the sail.

I bet I have nerve damage in my hand because of that :P

when putting the sail up, make sure halyard is tied to the middle of the halyard ring thingie- not the top ring. Make sure the SS ring is aft of the halyard line. Never had much, if any, problem this way.

No 'sure-fire' way but like everything on a cat it needs to be set-up to work properly in the first place.

-Make sure the main is not binding in the track.
-Make sure when halyard is tensioned the lock ring angles away from the mast.
-Put the boat on it's side with the main up and check the length of the hook. These are often standard components and are often too long. Grind back if necessary.

Note: The cringle position at the head of the sail varies from sail to sail. I have one sail I have to reverse the ring to get it to lock (it does come down easy though).

Cheshirecatman

Also a huge benefit is having a "welded" ring/shackle. I have my suspicions why its so helpful, but I'm not 100% sure.

I think it allows you to use the actual sail to rotate the ring a bit more than if it was unwelded.

You need to get back on the water. I see from your avatar you'd make the perfect string bitch

I wrap the halyard line around my harness spreader bar and pull with that.. Keeps my hands soft and supple, cause that's important to wanna-be sailing hacks like me...

take down jib and carefully roll it and put it in trailer box, then take pin out of forestay - dodle!
if you have been having problems with the halyard lock, this is a good time to get hammer out of tool kit, scream like a banshee and beat the c--p out of it.

RIng is the most important. My fav was the Nacra ring with twisted shackle but the NEXT SIZE DOWN twisted shackle as the Nacra factory choice is too big.
If using the welded shacke and ring then knot is important and it should be simple once these things are seen to.
Release all downhaul etc.
Pull halliard tight, twist mast to 90 degrees and let sail down.
If it is not that simple something is wrong...if you have a jib remove first and raise after main.