On Wednesday, June 3, 2020 at 11:40:37 AM UTC-7, Alex Fordham wrote:
I've just done our Astir CS.

A few tips:

Lifting the tail onto a tressle for better access made it a lot easier. You will also need to adjust the trim to get the bell crank in a suitable position for disassembly. If i remember right, about 3/4 stick back was about right.

To get the lower rudder bolt off, a standard 10mm open end spanner fits on vertically (not side on as normal) and wedged into the small gap between the rudder and fin. Allen key in the bolt on top. I was a bit worried about the spanner damaging the rudder , but the release torque on the bolt was pretty low so no trouble here.

Access to the nut/bolt at the bottom of the pushrod is tricky, but possible (I have big hands so at a bit of a disadvantage here!) You'll need 2x 10mm spanners, one with a ratchet. Ours was installed with the bolt through from the left (close to the fin skin) and the nut on the right, open side. I would recommend keeping it this way as getting the nut on the skin side would be tricky to say the least.
Open end spanner on the bolt head, ideally with a bit of tape on the back side to prevent it from falling off. Ratchet spanner on the nut. The open end spanner will need bracing on the bottom of the fin (left hand) and the nut loosened with the right hand. Light pressure on the ratchet spanner is needed to stop it falling off the nut, which means you have to put your hand quite far in, restricting the ratchet motion to 1 or 2 clicks. Not a quick job in other words! Be careful when taking the nut off as it can fall into the tail boom through the bulkhead holes and is a bugger to get back out (don't ask!)

Drilling the hole is straight forward, although not sure how they expect you to deburr the inside of the hole!?

I took the chance to restore the paint on the rod, as I didn't fancy ever having to take it out again!

Reassembly posed its own challenges, especially as a 1 man job. Ideally you will have someone to hold the rod in position from above while you reassemble the joint, but if not you can rest the pushrod on the bellcrank with the correct trim position. 2 problems:
1. The bolt was too long to fit back in between the rod and the fin skin
2. I couldnt get both hands in to push the bolt in while holding the rod in the correct position
I used the other bolt off the rudder/pushrod connection, and partially inserted the win the wrong (right!) side of the joint to align it, then inserted the actual bolt in the correct way, coming in from above at downward angle to fit in the tight gap. Then remove the rudder bolt and push the main bolt in all the way. Similar setup with taped spanner & ratchet spanner to re-assemble and same strategy for the rudder hinge bolt

No corrosion in ours either, and that is with a very leaky trailer!

The club Twin II Acro has been another story altogether, seems that the wrong pushrod (rivetted version) was installed and impossible to remove through conventional means, so a few new holes going in that one by the looks of it

Thanks for all this great info Alex, very much appreciated!