[Fenderbean]

I was wondering about the forward vertical stab mount bracket. After seeing the design and the single aluminum bracket with a bolt, is it safe to assume the main rear spar is most of the strength?

 

[Carl Froehlich]

Yes.

Remember that single bolt has a castle nut with cotter pin. Don’t let the DAR find you used a nyloc nut instead.

Carl

 

[Fenderbean]

Yes.

Remember that single bolt has a castle nut with cotter pin. Don’t let the DAR find you used a nyloc nut instead.

Carl

I will follow Vans manual like always; thanks figured such a simple bracket couldn't be structural in the sense of main load.

 

[MV-RVer]

I will follow Vans manual like always; thanks figured such a simple bracket couldn't be structural in the sense of main load.

Structural loads can be transferred through fixed, pinned, or sliding connections. This joint is intentionally designed as a pinned connection, allowing rotation about the bolt while transferring the required shear loads without developing significant bending moments. The flap piano hinge operates on the same principle, although it permits a much larger range of rotation about the hinge pin. If either joint were made rigid, normal control surface movement and structural deflection would generate high cyclic bending stresses. Over thousands of flight cycles, those stresses could initiate fatigue cracks and eventually lead to structural failure.

 

[Halleffect]

I will follow Vans manual like always; thanks figured such a simple bracket couldn't be structural in the sense of main load.

...and don't forget the NeverSeize on the bracket face.

 

[Fenderbean]

Structural loads can be transferred through fixed, pinned, or sliding connections. This joint is intentionally designed as a pinned connection, allowing rotation about the bolt while transferring the required shear loads without developing significant bending moments. The flap piano hinge operates on the same principle, although it permits a much larger range of rotation about the hinge pin. If either joint were made rigid, normal control surface movement and structural deflection would generate high cyclic bending stresses. Over thousands of flight cycles, those stresses could initiate fatigue cracks and eventually lead to structural failure.

Are we talking about the same thing? Im referring to the forward vertical stab attachment to the horizontal stab.

 

[Fenderbean]

...and don't forget the NeverSeize on the bracket face.

Thanks, I need to get something for this and all bolt installations. Are you referring to "Never- seez" or something else?
Currently building the tail cone elevators

 

[D-Dubya]

There are several brands of anti-seizing compounds and they all go by different names. Formulations are slightly different, as some may have more copper, nickel or aluminum in them. Use whatever type the instructions say, but you don't need it for all bolted connections. First off, you'll have that stuff everywhere until the day you sell the plane. Secondly, it can affect the torque values required for bolts & nuts.

 

[Halleffect]

Thanks, I need to get something for this and all bolt installations. Are you referring to "Never- seez" or something else?
Currently building the tail cone elevators

Yes, corrected: Never-Seez. Agree with DW; other than maybe spark plug threads, you won't use it much on this kit.

 

[dmattmul]

I was wondering about the forward vertical stab mount bracket. After seeing the design and the single aluminum bracket with a bolt, is it safe to assume the main rear spar is most of the strength?

This is what the 10 and 14 plans call for (I am assuming you are discussing this bolt) calling out Anti-Seize in the 10 and 14 plans. The 14 plans do a little bit better job of documenting this but unfortunately the well specified meaning of (bolt the using hardware called out in Figure 1 is a little unknown). I've seen builders torque to a cotter position and then back off to insert the pin, and I've seen builders once more torque to the correct value and then go to the next cotter position possible. The "loose is better camp (to allow the bracket to pivot) has created in some cases the hole to "woller out" yes not very technical I know but that's what occurs. Mine are tight (14 and 10) and don't allow the bracket to free float but maybe some movement occurs with the anti-seize in place? Aeronautical engineers welcome to correct what is the proper torque procedure is.

 

[Fenderbean]

Yelp that’s it.

 

[Richard Connell]

This is what the 10 and 14 plans call for (I am assuming you are discussing this bolt) calling out Anti-Seize in the 10 and 14 plans. The 14 plans do a little bit better job of documenting this but unfortunately the well specified meaning of (bolt the using hardware called out in Figure 1 is a little unknown). I've seen builders torque to a cotter position and then back off to insert the pin, and I've seen builders once more torque to the correct value and then go to the next cotter position possible. The "loose is better camp (to allow the bracket to pivot) has created in some cases the hole to "woller out" yes not very technical I know but that's what occurs. Mine are tight (14 and 10) and don't allow the bracket to free float but maybe some movement occurs with the anti-seize in place? Aeronautical engineers welcome to correct what is the proper torque procedure is.

View attachment 121450View attachment 121452

Proper procedure for castle nuts is to torque to the minimum recommend torque (plus drag) and then go tighter if required to get to a cotter pin slot.
AC43.13 refers

 

[dmattmul]

Proper procedure for castle nuts is to torque to the minimum recommend torque (plus drag) and then go tighter if required to get to a cotter pin slot.
AC43.13 refers

Since this document is over 700 pages can you give us less gifted readers section number? (Hopefully cover brackets with Anti-Seize bolted) Thanks

 

[Fenderbean]

Proper procedure for castle nuts is to torque to the minimum recommend torque (plus drag) and then go tighter if required to get to a cotter pin slot.
AC43.13 refers

Completely aware of torque requirements and the AC43. Military follows the same torquing procedures, we typically use solid film which dried like spray paint on all exposed threads. Never seen once affect torque but again like always I follow the manual from vans and the required torque for the bolt and nuts used. Cheers

 

[dmattmul]

Completely aware of torque requirements and the AC43. Military follows the same torquing procedures, we typically use solid film which dried like spray paint on all exposed threads. Never seen once affect torque but again like always I follow the manual from vans and the required torque for the bolt and nuts used. Cheers

Yes, but you are not using spray painted solid paint. What does Vans recommend with Anti-Seize on the brackets? What does AC43.13 recommend with Anti-Seize? What does your original question assume from Vans engineering "is it safe to assume the main rear spar is most of the strength?" So, you are assuming this pivot point provides limited strength, don' think so and probably not ? Seems a rear mounted attachment point providing the majority of the structural strength might not be a great plan.

 

[Dr_Dave_MT]

Since this document is over 700 pages can you give us less gifted readers section number? (Hopefully cover brackets with Anti-Seize bolted) Thanks

AC 43.13-1B Page 7-7
See insert

For the TLDR folks -

set minimum torque value for cotter pin alignment (do NOT back off)
if no alignment, tighten to maximum torque value.
If still not aligned, add sub-thickness washers, i.e. AN390-3L - NAS1149FN316P
DO NOT BACK OFF TO INSERT COTTER PIN

I'm assuming one understands "friction drag torque" if not read over Van's Section 5, 5-20 Rev 4.


I'm ass


From the Anti-Seize folks -

 

[dmattmul]

AC 43.13-1B Page 7-7
See insert

From the Anti-Seize folks -

Doesn't clamping a bracket with Anti Seize on both surfaces change the dynamics of the system and thus the clamping torque required? I guess the question is why does Vans specify Anti-Seize on the brackets? Do they want both surfaces to move or not? This is not the design Anti-Seize documents in their torque specification guide I'm pretty sure but I'm here to learn. Per plans 10 and 14.

 

[justa6ereh]

This is a contentious issue…but if you are adding anti-seize, dry lube…moly…anything…it’s because the designer has realized that this being a pinned joint, actually allows for movement and two aluminum surfaces rubbing on a steel bolt, with no bushing present will rub one of the surfaces away.

The 3,4,6,7,8.. ( I believe) all used multiple bolts to not allow this joint to move…bolts and nylok nuts.

When aluminum frets, through the clad layer and into the substrate, there is a rolled grain direction that tends to propagate cracks in the long transverse direction.

Adding anti-seize is an attempt to reduce wear to the movable joint. The holes in the aluminum being softer than the steel bolt should be the item to wear earliest.

My concern has always been that as the aluminum does wear and the particles of the worn aluminum joint with the anti-sieze and become a lapping compound of sorts…and then of course the possibility of cadmium wearing off the bolt leading to other corrosion potential over time.

I’m sure it’s all good and it’s all been tested and approved…but it still isn’t how I prefer to see a joint, when you have alternative choices with such robust history of not breaking up in flight or failing over and extended time frame, as yet, un-defined.

Given the 8,000 or so Vans aircraft all flying with fixed joints at the same location, ya might wonder why they’d ever change such a simple, robust solution for something that seems to make a lot of people ask lots of questions about and probably more than a few that didn’t do it quite right, with what appear to be more failure mode variables…

Me, being me….I’d just do it the way it was done for the first 40 years and be comfortable knowing mine wasn’t per the plans, just better.

 

[Richard Connell]

I really don’t think it’s worth over thinking.

If vans thought that this particular joint was so critical as to require deviation from generally accepted practices in then I’m sure it would be noted. I assume people put a wrench on this bolt occasionally.

Im a mech eng by training. At college I did an entire semester subject called “bolted joint design”. It’s fair to say that theres more to these things than meet the untrained eye - and there are plenty of other bolts that I’d spend more time contemplating.
I don’t tend to second guess the field tested designs of professional engineers.

I’m all for people TLARing their own airplane. It’s experimental after all. I just put that in the category of people turning up to their surgeon with their own scalpel and X-rays and saying ”I got this”

 

[rvbuilder2002]

As has been mentioned in other threads where this was previously discussed,
The spec for use of the antiseize was based on actual service experience on the prototype RV-10.
After a significant amount of flight time ( maybe 1500 hrs… I don’t remember the exact amount) light surface fretting was discovered on the front face of the web of the fwd spar and the aft face of the attach plate where they contact each other.
Keep in mind this was on an airplane that besides having a lot of hrs, was used extensively for transition training which included a lot of departure stall training
( have you ever looked back at the tail shake that goes on during that ).

The anti-seize resolved the fretting issue.

Keep in mind that when it says “thin coating “, it means THIN COATING.
Think just barely coating the surface by smearing a very small amount on one surface with a finger tip. There should not be enough such that there is any hydraulic action with antiseize being squeezed out when the bolt is fully torqued. That would result in a situation where it would continue to do so over time, which would cause the bolt pre-load to be lost.

 

[Fenderbean]

Yes, but you are not using spray painted solid paint. What does Vans recommend with Anti-Seize on the brackets? What does AC43.13 recommend with Anti-Seize? What does your original question assume from Vans engineering "is it safe to assume the main rear spar is most of the strength?" So, you are assuming this pivot point provides limited strength, don' think so and probably not ? Seems a rear mounted attachment point providing the majority of the structural strength might not be a great plan.

I think people are just over thinking the original question. I was just wondering, seems like this bracket stabilizes the forward side of the vertical. Keeping it from moving left and right and the anti-seize is between the two plates not the bolt or threads. Again I assume this is for flexing of the vertical under normal flight causing the two plates to rub a little.

 

[David Paule]

The aero load isn't directly centered on the rear spar, it's forward of that, and the rudder load adds some additional off-spar force. The rear spar carries the bending but the front spar keeps the vertical stable. Being an elastic structure, there's a slight bit of rotation at the fasteners, hence that anti-seize.

Dave

 

[Ironflight]

ALthough I have never built an RV that has the forward VS spar bolt configuration in its design, for those who think it is unusual, think about your wing attachment. One spar is firmly bolted with a bunch of fasteners. The other spar has a single bolt through a hole with a castle nut to allow some rotation/flexing. For the wing, the firmly fastened spar is the front - the rear is allowed to move a little. For the -10’s VS, it is reversed, but the idea is the same. If you have a large surface, and it is doing some twisting, the joint that is allowed some motion relieves the stress. If it was firmly bolted or riveted, there is a lot of stress at those smaller fasteners, and cracking can begin.

Why the difference between the smaller, short-wing RV’s and the -10? The size of the VS maybe? I haven’t done the math or talked to the engineers about this particular solution….but I can hypothesize. That allows me to ask better questions, which is the art of engineering…. I’ll have to ask Rian some day!

 

[justa6ereh]

ALthough I have never built an RV that has the forward VS spar bolt configuration in its design, for those who think it is unusual, think about your wing attachment. One spar is firmly bolted with a bunch of fasteners. The other spar has a single bolt through a hole with a castle nut to allow some rotation/flexing. For the wing, the firmly fastened spar is the front - the rear is allowed to move a little. For the -10’s VS, it is reversed, but the idea is the same. If you have a large surface, and it is doing some twisting, the joint that is allowed some motion relieves the stress. If it was firmly bolted or riveted, there is a lot of stress at those smaller fasteners, and cracking can begin.

Why the difference between the smaller, short-wing RV’s and the -10? The size of the VS maybe? I haven’t done the math or talked to the engineers about this particular solution….but I can hypothesize. That allows me to ask better questions, which is the art of engineering…. I’ll have to ask Rian some day!

Paul, I would acquiesce and buy all of that for a dollar if a bushing were used to deal with the rotating component, but to bear an aluminum hole on a steel bolt, and torqued castellated nut and throw in anti-seize as a means of stopping the fretting…well, you already know that the hole will enlarge over time WHEN it moves, doesn’t take much…and as soon as it starts…it continues.

To me, it’s just a bad practice. And with ten thousand successful examples demonstrating it isn’t an issue the “old way”…zero failures…I’ve always had a tough time calling this progress. But I say the same thing about a bush plane full of pop rivets…

I’ll go back to repairing my fabric on my Waco and quit raining on the parade.

 

[Ironflight]

Paul, I would acquiesce and buy all of that for a dollar if a bushing were used to deal with the rotating component, but to bear an aluminum hole on a steel bolt, and torqued castellated nut and throw in anti-seize as a means of stopping the fretting…well, you already know that the hole will enlarge over time WHEN it moves, doesn’t take much…and as soon as it starts…it continues.

To me, it’s just a bad practice. And with ten thousand successful examples demonstrating it isn’t an issue the “old way”…zero failures…I’ve always had a tough time calling this progress. But I say the same thing about a bush plane full of pop rivets…

I’ll go back to repairing my fabric on my Waco and quit raining on the parade.

OK - so what do you think of the wing aft spar attachment on pretty much all of the low-wing RV’s? Have you changed that on yours? Do they need a bushing as well? Its the same basic concept.

As I have said, I am not privy to the actual engineering on the joint in question - but it is that way for a reason because they changed from what had traditionally been used. I wouldn’t decide to change a critical attachment point until I understood the design criteria.

 

[lr172]

Paul, I would acquiesce and buy all of that for a dollar if a bushing were used to deal with the rotating component, but to bear an aluminum hole on a steel bolt, and torqued castellated nut and throw in anti-seize as a means of stopping the fretting…well, you already know that the hole will enlarge over time WHEN it moves, doesn’t take much…and as soon as it starts…it continues.

To me, it’s just a bad practice. And with ten thousand successful examples demonstrating it isn’t an issue the “old way”…zero failures…I’ve always had a tough time calling this progress. But I say the same thing about a bush plane full of pop rivets…

I’ll go back to repairing my fabric on my Waco and quit raining on the parade.

i also don't understand why if the joint is suppopsed to move, why are we tightening the bolt which would seem to be a pivot point. also agree that rotational movement around that bolt will wear away the hole ID on the plates, but have to wonder if that is really happening.

Is there a reason that a second bolt wasn't added to prevent the movement and associated fretting vs using a lubricant?

 

[lr172]

OK - so what do you think of the wing aft spar attachment on pretty much all of the low-wing RV’s? Have you done that on yours? Do they need a bushing as well? Its the same basic concept.

As I have said, I am not privy to the actual engineering on the joint in question - but it is that way for a reason because they changed from what had traditionally been used.

i always assumed one bolt was due to the limited space / inability to get a second one in there vs an actual pivot point. the front spar is fully secure, yet still allows the wing to move and flex. why does the rear spar need to pivot, yet the front doesn't?

 

[justa6ereh]

OK - so what do you think of the wing aft spar attachment on pretty much all of the low-wing RV’s? Have you changed that on yours? Do they need a bushing as well? Its the same basic concept.

As I have said, I am not privy to the actual engineering on the joint in question - but it is that way for a reason because they changed from what had traditionally been used. I wouldn’t decide to change a critical attachment point until I understood the design criteria.

What I feel about the aft spar joint is two-fold…

A; It’s in trail with a supporting structure of the main spar and forward attachment, that in a failure mode, or loosening mode from wear…you would see and feel a lot of weird symptoms, before an actual complete structural failure…


and B: roughly 10,000 airplanes and no specific issues about this joint and that it’s mainly a panacea when people can’t answer the actual question, used as a means of diverting to an issue they feel they can defend.

IF the forward spar bolt failed on the vertical, in an excited fashion…meaning recovering from an aerobatic maneuver….or bumpy flight condition…I assure your that rear spar will not get you back to the ground in one piece by itself.

if the rear spar attach fitting wore to the point of being an 1/8” of an inch oversize and was flexing around in flight, Inthink you’d still get back to the ground in one piece,

That’s all…

 

[rvbuilder2002]

Don’t lose sight of the principle of arm distance vs relative movement….

The bolt is the center of rotation (if movement occurs).
The contact area on the spar extends out beyond the center of rotation point.
If there is a consequential but extremely minimal amount of movement out on the fringe edges of the spar to bracket contact area, the actual movement around the perimeter of the bolt hole would be infinitesimal.
In turn, wear within the hole would be as well.
In cases were there has been, I believe there were other factors involved.

 

[justa6ereh]

Don’t lose sight of the principle of arm distance vs relative movement….

The bolt is the center of rotation (if movement occurs).
The contact area on the spar extends out beyond the center of rotation point.
If there is a consequential but extremely minimal amount of movement out on the fringe edges of the spar to bracket contact area, the actual movement around the perimeter of the bolt hole would be infinitesimal.
In turn, wear within the hole would be as well.
In cases were there has been, I believe there were other factors involved.

Scott, I don’t disagree with you at all on that. The issue to me has always been the fretting, which once started can lead to crack propagation.

My hope is that people inspect their airplanes , not overlooking this joint. Meaning clean the anti seize, remove the bolt and inspect for wear at each condition inspection.

 

[Fenderbean]

wow you guys are going there lol I was basically asking what holds the thing on mainly, because the aluminum there is not all that beefy so being more like your wing attachment points would make more sense with the rear spate that has a much thicker spare and more contact with the tail cone. If there was a bunch of load on that bracket, I would also guess it would be a different design.
If that bolt hole did wear and or a one of the rivets failed I don't think the vertical would fail?