Help! Wrong Hinges On Rudder ?
 

Based on the problems with the elevators last flight, this morning I removed the rudder to lube/inspect. Found two GMM-3M-670 rod ends and one -670. This can't be right according to plans, right? The -680's were barely hanging on with only 3 threads engaged in the nutplate! :eek: At least the jam nuts were tight.




So, assuming this is NOT according to plans, where are the shorter -670's used so I can go hunt for my two missing -680's?

Otherwise, I'm ordering a new set from Spruce.

Thanks

From my experience. What you have is correct. Sometimes it is noticed that the vertical is not trimmed enough forward at the top so the bearings in the rudder are not installed in as far in as they should be. The bottom bearing is longer so to accommodate the rudder horn. Some builders have installed the longer bearings in the top and center because of the issue you have come up against. Larry

I just finished the rudder on my RV-7. DWG-7 calls out MD3614M rod end bearing for the top 2, and a larger MD3616M at the bottom. At each location there is a unique spar web-to-bolt-center dimension. You need a set of plans to determine the proper rigging. I don't know the details of your RV-8, but I wouldn't be concerned about different hardware in different locations.

OK, weird.

However, these top hinges are only catching a few threads and that is a major problem in my book. Going to have to look at this more carefully, because there is not much room to bring the rudder forward. Certainly not enough to get the threads fully engaged, anyway.

Thanks much for the heads up!

Just for a data point. My 8 plans show the same set up. 14s for the top and middle and 16 for the bottom.

Each is set at a specific distance from the attach bulkhead. I made a couple wood jigs with a bolt inserted in a hole to get them near that distance. Later today I will find that specification if you need it.

I'm at a disadvantage without plans, but is there any reason why the longer rod ends are not used on the top? Is there some structure aft of the rudder spar that the longer shank would interfere with? In other words, if you had say a half inch of thread protrusion through the nut plate, would that be bad (aside from dead weight)?

I recommend getting and having plans on hand so that the issues that come up can be addressed properly. If the parts are assembled per plans and the correct measurements are obtained from the plans, the supplied parts should work just fine. I have and others as well have seen your scenario pertaining to the rod end bearings way to many times. Please get a copy of the plans and go from there and maybe ask a seasoned builder to look it over. :-) Larry

FWIW ... I put those rod end bearings in my -7 rudder a few months ago and I had to run them in until the threads were nearly invisible to make the dimensions called out in the plans. I only had to tighten the jam nut a turn or two to lock it down.

Rod End Bearing Length
 

If you feel uncomfortable with how many threads are engaged, I recommend purchasing a couple of the longer ones and simply replacing them. It's a small price to pay for "peace of mind" don't you think? :rolleyes:

Good luck.