Rudder Arm Bolts

[alaskabearhawk]

I was talking to a friend about the rudder arm. I turned mine down to fit the rudder and I had some questions about springs, etc. He asked me how I was going to bolt the arm to the rudder. I told him the plans spec a single AN4 bolt. He said it would be better to use two AN3 bolts. I asked why and he said that was the standard practice for aircraft he was familiar with. Today on my way home I stopped out at the local airport and looked at rudder arms...lots of rudder arms...about 15 total. PA18, PA12, PA14, PA20, Citabria, Maule M5/M7, T-Craft...they all had two AN3 bolts holding the rudder arm on the rudder. Any thoughts on this?

[Enewton57]

I am not an engineer so I can't really comment on the strength differences. I do tend to trust Bob and stick with the plans. Also, I have not heard of any failures of that bolt on any Bearhawks. I guess there is a slight amount of weight penelty when you add a second bolt, washer and nut. Bob is always telling me, "don't add weight unless there is real good reason for it". So I guess I would say, what is the reason for this added weight?

[alaskabearhawk]

I checked with a friend that is an active A&P and works on a lot of Super Cubs that work for a living. Not the weekend guys, but the air taxi folks. I explained what the BH plans have and what I saw at the airport. He asked of all the BH aircraft flying, how many do off-airport work...and by that he meant real bush flying off unimproved areas. I told him probably not that many, if at all. I told him that I knew of one that may fall into that category and that is Pat Fagan. He indicated he checks that very closely on every aircraft that comes into his shop and very often sees the rudder arm is loose...loose in the sense you get movement out of it. He strongly recommended two AN3 bolts. He said, like you, he's not an engineer but goes on what he sees in practice.

[marcusofcotton]

I'm very glad you brought this up Paul. The two AN3s will distribute stresses more, weight will be within a small fraction of an ounce, and adds some redundancy.
Mark J