Discus 2 rudder stiff help please

On Tuesday, August 27, 2019 at 6:40:25 AM UTC-6, Dave Nadler wrote:
On Tuesday, August 27, 2019 at 1:24:06 AM UTC-4, wrote:
When you disconnect the rudder cables, be sure to attach a section
of safety wire as the cables are spring loaded and may retract into
the fus which will make retrieval of the cables difficult.

Really now, don't go spoiling the entertainment value for onlookers...

Dang, ran out of popcorn, but put it on the shopping list. Doesn't look like Amazon.com has one day delivery yet.

I’ll second Karl’s remarks. I remember a pilot at a Nationals that had a tow hook that was jammed........wouldn’t budge! I told him to pull the seat and we found a tow pulley that was sitting in water from a leaky wing bag..........he said the bag had always leaked. The problem comes from situation known as dissimilar metal corrosion. Usually, the brass bushing and steel bolt + water will set up an electrolytic action..........aka a little battery! Our little battery needs water to make it work and it works even better if it finds salt water or urine. The little battery hates lubrication, so inspect and lube everything you can git to, every year!
JJ

Thanks to everyone who posted suggestions. I appreciate your help.

Having now disassembled the rudder with my AME, the answer seems to be that the retaining nut was too tight.

The rudder on this ship is kept in place by an M8 metal locknut and washer on the lower pivot pin. On disassembly, the nut was hard to turn at first. After loosening by 1/2-turn the rudder moved freely. Upon removing the rudder the bronze bushing and washer on the lower pivot had bright mating faces showing sliding contact.

Not so clear is why the nut had become overtight. The rudder never been taken off. One theory is that the nut worked itself tighter through friction as the rudder moved.

No significant corrosion was seen on the rudder horn, bearing or mounts.

On reassembly after cleaning and lubrication and with a new metal locknut my AME could reproduce the issue by tightening the nut against the bearing. After backing off the nut slightly to give slight clearance the rudder moves freely.

Some pics here if anyone wishes to take a look. https://1drv.ms/u/s!Al9GDrAowZRAi59D...aIqCA?e=jhOKn8

Ian IN

Situations like this can be avoided if the annual inspections are done properly. Both the rudder and the seat pan must be removed to catch problems. When I was the dealer for a German company years ago I and the company were sued for a fatal crash where the flight controls under the seat pan were compromised. This happened because water had puddled under the seat pan and the ship was parked in a hangar with the tail elevated. The seat pan had never been removed.

Regarding rudder hinges, they are prone to corrosion from wing water dumping, flying through rain, tail ballast dumping and, especially, urine contamination. A friend had to replace the lower rudder hinge in his D2 due to corrosion.

Removing the rudder and seat pan annually is a must.

KS

On Monday, August 26, 2019 at 7:55:09 AM UTC-4, India November wrote:
The rudder on my D2b has become very stiff on its hinges during this season. I disconnected the cables at the rudder horn, and it's clear the problem is in the rudder not elsewhere in the control circuit. Removed mylar seals without effect. No visible damage to the rudder, and no foreign objects visible between rudder and fin. Before I remove the rudder, has anyone out there encountered a similar problem? Glider has 650hrs TT, always hangared.

Thanks in advance for all suggestions!
Ian IN

Do you have a bladder relief exit on the fuselage behind the gear? Urine can run backward and up to the first hinge point and cause problems there. If that is the case, move the exit from where it is and to one side of the landing gear structure and have the tube clear the ground a couple of inches. This means you must lower the gear before urinating.