Rudder attachment

[vetdrem]

A friends 46 bc-12d has an issue that was just discovered. The tube attached to the vertical post that is the lower hinge for the rudder broke off.

It appears that it was brazed on to the post, not welded. Is that how the hinge was originally attached, or is this an improper repair done at some time in the past.

Louie

[Pearson]

Re: Rudder attachment

Louie,

It is supposed to be welded.

[vetdrem]

Re: Rudder attachment

I was pretty sure it was, I just couldn't believe someone did a repair like that.

thanks

Louie

[M Towsley]

Re: Rudder attachment

Pretty drastic to replace the fin if not repairable, but I have a vertical fin for sale.

[vetdrem]

Re: Rudder attachment

I haven't seen it, but from the description, I am sure it can be repaired (correctly this time)

Louie

[Hank Jarrett]

Re: Rudder attachment

You need to get ALL of the braze out or it could contaminate the weld. We had a BEAUTIFUL homebuilt here that was entirely brazed together instead of welded. The builder brazed it together and primed it before it was inspected and they let it pass (this was back when the FAA actually LOOKED at homebuilts at phases of construction, although not very well on this one!). It had been flying for years when it was found out. A lot of planes in the 20s and 30s were brazed, and if done correctly it can be strong enough, but the design MUST ACCOUNT for the strength of brazing instead of welding. You CAN NOT substitute and most welders won't touch a joint once it has been brazed. You may have to cut the affected area out and splice in new tube to get rid of ALL of the braze. DO NOT weld on it unless ALL of the braze is gone!
Hank

[vetdrem]

Re: Rudder attachment

Yea, we talked about that. It will be done right, whatever it takes

[Guest]

Re: Rudder attachment

I was pretty sure it was, I just couldn't believe someone did a repair like that.

thanks

Louie

I see brazed joints a couple of times a year on Aeronca landing gear case frames (.a.k.a. landing gear "vees").

The perpetrators are quite clever they hide it by making the joint have a nice bead that looks like a weld.

Its so well done that sometimes the owners are hard to convince that it is really a braze joint.

They all must be removed and most often its best to replace all but the biggest parts.

I clean up the large parts (in this case 2" dia. tubing .050" to .062" wall) with a flap wheel on an angle grinder or a grinding disc for aluminum.

I inspect the cleaned surface in bright sun light and I also apply heat to watch the steel turn blue and look for places that do not turn blue.

Here's the thing though; the rudder spar is .027" wall as I recall so you don't have much grinding margin.

Also I recall that the hinges have a small piece of sheet about .020" thick and 1/4" by 1/4" between them and the tube to stand them off the tube.

Without it the hinge pin head may scrape the spar.

Dave