Discus 2 rudder stiff help please

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

On Monday, August 26, 2019 at 5:55:09 AM UTC-6, 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

The rudder rides on two surfaces that you could try to lube without removing the rudder. A lubricant with an extension nozzle should reach both. That said,
the rudder is relatively easy to remove (one nut). It is probably a good idea to remove it and clean the hinge points properly.

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

I've got an ASW19B with a similar issue. I've adjusted the nut at the bottom of the rudder with no affect. I too would appreciate any suggestions. And thanks!

Is the gap between the rudder and fin skin OK? Check it by sliding 80 grit sandpaper in the gap with smooth side towards the rudder. Run it all the way up and down on both sides, all gaps should be free, sand till it is.Spray lube both hinge points.
JJ

On Monday, August 26, 2019 at 7:05:05 AM UTC-7, wrote:
Is the gap between the rudder and fin skin OK? Check it by sliding 80 grit sandpaper in the gap with smooth side towards the rudder. Run it all the way up and down on both sides, all gaps should be free, sand till it is.Spray lube both hinge points.
JJ

JJ, it's likely there are "V" seals in addition to the standard mylar seals.. Running sandpaper in the gap will likely destroy those seals.

Ian, the rudder comes off fairly easily with just removal of a single nut at the bottom of the rudder. I haven't looked specifically at the Discus, but if it's like all the other SH aircraft I've worked on, there's a castellated nut secured by a cotter pin. The cotter pin can be accessed by pushing the rudder to full deflection. Once the nut is off the rudder can be shifted upward and it will come off the hinge pins. It's helpful to remove the rudder cables first.

It may be time for new V-seals or cleaning and lubrication of the plain bearings. There's no mechanical reason why it should be stiff.

Hope all goes well. If there's any question, get it to an aircraft mechanic for some help.

Cheers,
Craig

Totally agree....
Minor bit....as swiping the coarse sandpaper between rudder and fin, move rudder maybe 20* and try again.
Do NOT assume the front radius on the rudder is constant....... may be fine in spots, my bind in others.
Yes, sounds like check binding between rudder and fin....if OK.....pull rudder, clean stuff (WD-40 can work here), lube and go from there...

Do you use an overboard type relief system?

At 14:06 26 August 2019, wrote:
Do you use an overboard type relief system?

If so, corrosion in the lower rudder hinge usually is the culprit.

Agree, hinges are the most likely problem. Definitely worth removal for an inspection of any possible damage from corrosion. If OK, clean and lube should fix.

Mike

On Monday, 26 August 2019 16:47:27 UTC+3, Bravo 8 wrote:
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

I've got an ASW19B with a similar issue. I've adjusted the nut at the bottom of the rudder with no affect. I too would appreciate any suggestions. And thanks!

There is a brass bushing inside lower hinge. This has worn short over time. You notice this by tightening the lower nut, rudder has no vertical play anymore and bolt is crushing the hinge. Replace brass bushing and you are good to go. Note, rudder must ALWAYS have vertical play, even when nut is tight. If there is no play, bushing is not doing it's job.