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Longerons are cracked on each side on the front of the roll bar

riobison

Well Known Member
Hello

On my RV 4 the longerons are cracked on each side on the front of the roll bar attachment as attached in the fotos. I’m thinking probably my girl friend riding jump seat has used the roll bar to pull on to get out of the jump seat over the last 10 years. Now, the more I think about it, its probably me using it as dipping bars to maneuver my 230 pound frame in and out.

I’m thinking to stop drill the cracks then a doubler to go on top of the longeron and under the roll bar riveted to the longeron to reinforce it?

Extend the doubler several inches pass the cracks on each side? At least cover where my hands go.

What thickness of doubler?

I could also go under the longeron but could be a lot more difficult to do.

Of course I’m open to any and all recommendations from you all if anyone has been down this path in the past.

Thanks

Tim
 

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I don't have an RV4, but (to me) that does not look like the correct way to mount the roll bar. I can see why it cracked, it had no choice.

Get ahold of the plans and figure out the proper way it should be, then repair with standard procedures. You may need to spread the roll bar to allow for a better edge distance.
 
Not the longeron

Not an expert ...but that isn't the longeron ....it is .040" piece that goes over the longeron ....F-416 cockpit rails (available from VANS ) ....as to fix ...I'll leave that to someone else ,but I would investigate why it is cracking
 
The piece with the cracks is not the longeron it is the "cockpit rail" F-416. The roll bar is bolted to a piece of 1X1 angle underneath F-416 that is also riveted to the two bulkheads below and the .063 plate at the top of the bulkheads.

On the picture of the left side you can see the 1x1 angle, you can not on the the right. Is it possible the that it is missing or not properly installed. The bolts for the roll bar go through this angle. See the attached picture.

https://photos1.blogger.com/blogger/2531/2999/1600/HPIM0091.jpg
 
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Roll bar installation......

The piece with the cracks not the longeron it is the "cockpit rail" F-416. The roll bar is bolted to a piece of 1X1 angle underneath F-416 that is also riveted to the two bulkheads below and the .063 plate at the top of the bulkheads.

On the picture of the left side you can see the 1x1 angle, you can not on the the right. Is it possible the that it is missing or not properly installed. The bolts for the roll bar go through this angle. See the attached picture.

https://photos1.blogger.com/blogger/2531/2999/1600/HPIM0091.jpg

It appears this roll bar was not installed correctly. If it does not have the above pictured reinforcements, it is merely decoration and needs to be fixed "before the next flight". Your shoulder harness is likely attached to it and it's function as roll-over protection is dependent on proper support and installation. The pictures you submitted are.....how can I put this without sounding extreme.....SCARY :eek::eek::eek: The attach bolt holes actually appear oval which means the roll bar has been moving. The cracks indicate the same thing only movement in a different direction. Did I mention SCARY? Fix before next flight......just a suggestion.

I'm pretty sure most people are using the roll bar as hand-holds to enter and exit the airplane. Even with your and passenger weights there should be NO movement where the bar attaches. There is obviously movement in yours. It is designed to take the entire weight of the airplane in the event it lands upside-down on the roll bar, including the force of the weight jamming into whatever surface it is hitting.

If you can, get under the roll bar attachment area and take more pictures like the ones MS1095 posted. That may help us sages better determine what might be going on.
 
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When the roll bar is installed correctly, lifting one's self out of the airplane using the side rails will flex them and eventually crack in the locations shown.

I have stop drilled some minor cracks on my airplane (and can assure you that there is no play in the roll bar, and that the supporting side structures are in place).

As I did not perceive the top rail as structural, it did not even occur to me to replace them unless the cracks started to progress toward the outboard edge. I'm curious if anyone here thinks differently?
 
Dipping in and out of the RV4 causing cracks

Gents

All of the pieces are there including the 1 inch angle. The roll bar is solid, its not shifting and the holes are not oval. It was built by someone more than qualified and if the roll bar is ever needed, it will serve its purpose.

It appears the F-416 cockpit rail is what's cracking right next to the 1 inch angle (where my big mitts go). Probably from me over the last 10 years and hundreds of dips getting into and out of the cockpit has caused enough flexing to induce the cracks.

I`ve stopped drilled the cracks and that will probably do the trick until I put my hands there the next time to get in and out.

So it appears that this rail isn't a longeron and isn't structural?

Suggestions on the best way for getting in and out now that this isn't going to work after all of this time?

Suggestions on repair and prevention for the future? Of course I need to quit doing what I've been doing.

Thanks

Tim
 
Brace

It looks like a vertical brace is needed between the rail and the side wall gusset so as to take the load and support the rail from flexing (and cracking) when you push down on it.
 
That crack happens from lifting one’s self out of the plane, it flexes the f416 which over hangs the longeron it happened to me. I put a strip of .063 steel under the 416 to stiffen it
 
Suggest you get a design recommendation from Vans. It is just a super stiff structure right up to the point that part of the rail is cut and left with an opportunity for unexpected loading. Clearly the rail needs to be tied into the structure.

Vans knows the loads and specifics of the structure, and it should not be too difficult to make a strong and light repair so you can still use the rail for entry and exit.
 
Same here

Mine has done the same thing, and I’m positive that area is built per plan.

I am certain it’s because that’s where I put my weight to lift myself out (180 lbs) I have since started sliding up the seat slightly so I can grab the lower part of the roll bar to extricate myself.
 
I also had the same issue years ago. I stop drilled the cracks and installed a couple of .063 doublers to spread out the load.
 

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Not quite right.....

OK: I guess that lifting yourself from the cockpit by the side rails is a common method of entering and exiting the airplane. And it looks like cracks have occurred there before. The last post looks like a decent fix to that problem. Personally, I use the rollover structure to slip in and out of the cockpit.

However, looking at the second image I am concerned with several things:
1) There is no underlying angle seen under the cockpit rail as seen on the other side and as plans call for. Thus, the bolt holding the rollover structure is not within edge-distance requirements of proper construction.
2) There is a hole peeking out from under the foot of the roll over structure indicating that a hole was previously drilled in the underlying angle (that I assume is there) and the hole for the current bolt is very close to that hole and, if it goes through the underlying angle, once again, does not comply with edge-distance requirements of construction.

IMHO. The mechanic in me sees things that don't look quite right, like this. If you are happy with how this is, I guess I should be as well. I apologize for being so picky.......:p:p
 

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OK: I guess that lifting yourself from the cockpit by the side rails is a common method of entering and exiting the airplane. And it looks like cracks have occurred there before. The last post looks like a decent fix to that problem. Personally, I use the rollover structure to slip in and out of the cockpit.

However, looking at the second image I am concerned with several things:
1) There is no underlying angle seen under the cockpit rail as seen on the other side and as plans call for. Thus, the bolt holding the rollover structure is not within edge-distance requirements of proper construction.
2) There is a hole peeking out from under the foot of the roll over structure indicating that a hole was previously drilled in the underlying angle (that I assume is there) and the hole for the current bolt is very close to that hole and, if it goes through the underlying angle, once again, does not comply with edge-distance requirements of construction.

IMHO. The mechanic in me sees things that don't look quite right, like this. If you are happy with how this is, I guess I should be as well. I apologize for being so picky.......:p:p


I agree it looks like the angle is missing. Can you post a few other pictures from the side and underneath looking up?
 
Repair

Mine has done the same thing, and I’m positive that area is built per plan.

I am certain it’s because that’s where I put my weight to lift myself out (180 lbs) I have since started sliding up the seat slightly so I can grab the lower part of the roll bar to extricate myself.

I can remember when I was 180 pounds, everything was easier;)

I like RVspikes fix. it's similar to what I was thinking. I'm glad I'm not the first that this has happened to.

Yes, all of the 1" angle is there as well as all of the supports and rivets.

Thanks for the help everyone.

Tim
 
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