Rudder bottom fairing interference with VS bolts

[PaulvS]

I'm doing the final installation of the rudder on my -6A and have encountered interference between the rudder bottom fiberglass fairing and the lower AN4 bolts that attach the vertical stabilizer. The bolts are of the correct length and installed per plans with the heads facing forward. The tails are contacting the rudder fairing, preventing full travel. I previously trial fitted the rudder before painting and the VS bolts were not all installed at that time and so the interference was not evident.
One option is to reverse the direction of the VS bolts and put the heads backwards so as to eliminate the contact points. Another option would be to cut away the rudder fairing where it touches against the bolts. Access is very tight to reach and remove/replace the VS bolts down in the tail cone and that seems to be the cleanest solution, though it is not per plans for the way the bolts are supposed to be oriented.
What do you think?

Picture of bolts:



Picture of rudder bottom fairing. The white mark in the centre is where the bolt contacts the fairing, on both sides.

 

[D-Dubya]

There's another option. It looks like you have plenty of length on those bolts, with maybe six threads showing past the end of the Nylock nut. Go down one size on the bolt length. I think the standard is to have at least one but no more than three threads showing past the end of the nut. Use a thin washer under the nut if you have to.

 

[wirejock]

Don't know how similar the 7A is, but mine was all done and painted like yours when I found it hit the fuse. I had to carve it up and refinish it.

 

[bjdecker]

Concur with @D-Dubya, bolts are too long.

Attached from the -7A, but you get the idea. The 6A tail tie down must be different. For the -7A, Van's created a new part (F-712E) that sits on the forward side, catches 4 bolts, all AN3-6A's, etc..etc...

 

[mburch]

Also worth noting that the 7/7A plans have the bolts the other way around, nuts forward / head aft.

 

[Ironflight]

Also worth noting that the 7/7A plans have the bolts the other way around, nuts forward / head aft.

They are that way on the -8 and the -3 as well as on our -6….. I seem to remember the plans showing that for the -8, but didn’t go look to confirm. Remember that “heads up and forward” is a general guideline, and not a hard-and-fast rule…..

 

[RV7 To Go]

Same as what Paul said. Bolts forward on my 7,8 and 4. No interference on any of them.

 

[RV8Squaz]

Yet another option is to adjust the rod end bolts to “push” the rudder aft. You only have 2 threads showing so you may have some flexibility there. Of course, the other two, particularly the middle one, will have to be adjusted as well.

 

[lr172]

I probably should have flipped the bolt around, but just ground out two divots in the fairing with a die grinder. You can’t really see it unless looking for it. I wasn’t going for extreme beauty when i did the 6.

 

[rocketbob]

I install 1/4" nutplates so one doesn't have to remove the elevators to install or remove the VS. Bolts point forward.

Before anyone questions this, a friend of mine did pull tests and found regular AN nut threads were not as strong as nutplate threads. In this case it doesn't matter as these bolts are loaded in shear.

 

[PaulvS]

Thanks all for the replies, I flipped the bolts around and that solved the interference problem.

I agree the AN4-6A bolts look too long with more than 3 threads exposed beyond the nut, this is even so without any of the smooth shank protruding out of the hole. An extra washer results in about 2 visible threads.

 

[JonJay]

I install 1/4" nutplates so one doesn't have to remove the elevators to install or remove the VS. Bolts point forward.

Before anyone questions this, a friend of mine did pull tests and found regular AN nut threads were not as strong as nutplate threads. In this case it doesn't matter as these bolts are loaded in shear.

You can find almost anything on VAF

Bolt and nut versus bolt and plate nut

Is a plate nut with a bolt equivalent shear and strength to the same size bolt with a nut and washer? Wondering if I could substitute a nut for a plate nut or if there is more to it due to strength, so it is more dependent on the situation.

vansairforce.net

Thread strength, in and of itself, doesn’t seem to be the potential failure scenario Mr. Smith speaks of, but, as you say, it’s irrelevant in shear.
Still, I don’t deviate from plans in critical areas that have been proven over time. I don’t know what I don’t know.
1000 hours and 18 years and haven’t had the need to remove either VS or HS.