Sheet metal stress failure - center rock guard cover

[H_Mark]

2014 Flying Cloud has developed metal fatigue stress fractures at both right and left front rock shield upper middle stud mounts. There have been no impacts or collisions to cause this. I believe the cause to be wind pressure and wind turbulence from passing vehicles. The left stud mount body surface shows the most damage on the side where vehicles pass. So far the only suggested remedy is replacing the panels. The problem with this is, it does not correct the underlying failure which is the sheet metal at that point can't support the wind pressure. Just replacing the segment with the same material would likely result in the same stress failure. I wondering about alternate solutions. One is an external patch afixed with 3M marine sealant. Another might be to reinforce a new panel on the backside in a similar manner. The attached photos show the sheet metal failure.

[Belegedhel]

Welcome to the forums!


Well, I can't say that I have ever seen an issue like you are showing.



The solutions you describe are major surgery (ie., replacing the entire segment), and I would agree that assuming the new segment is of the same alloy as the original, there is no reason to expect different results. Reinforcing from the backside is even more labor intensive. Your reference to marine adhesive sounds like you don't want any "additional" rivet heads visible...


One suggestion I would have is to add mounting points so that the rock guard is supported by more points on the segment. Problem again is, that you are creating more disfigurement (in the form of the mounts) on the shell, but the question is, are the rock guards not really a fairly permanent part of the trailer anyway (so anything hidden by them is not really going to be a glaring defect)?


good luck!

[eubank]

Maybe a nice patch would be best! Lots of vintage Airstreamers have fun creating interesting looking patches: Hearts, stars, animals, whatever! Then mount the guards right into the patch, serving as a much stronger location for it.


Lynn

[BayouBiker]

Because this is uncommon, I would attribute it to high vibration cycle failure not due to passing cars but something unusual about your Combination. They must be getting hit by the vortexes shedding from the tow vehicle. Can you also change up the configuration slightly?

[crispyboy]

For a budget fix I would get a matching piece of aluminum maybe 4" x 6" and olympic rivet it on the outside. Caulk up the patch with Sikaflex sealant before riveting. Shouldn't be too noticeable as most of the patch material will be hidden behind the panel.
It may just be that run of aluminum was not up to spec - bad metallurgy. This rock guard issue seems very rare.

[ROBERT CROSS]

Ours segment protectors don't have the 'center support'. I suspect it's just another improvement.
Consider removing them and cover the cracks with 3m extreme sealing tape, stainless bolt and acorn nut to fill the hole in the protector.

Bob
🇺🇸

[panamerican]

I would have to agree with BayouBiker-

There has to be something with your connection that is torquing the frame/body. My guess is that this would only be the tip of the iceberg. If correct, expect leak from windows, etc as the body torques. It's either that or some kid hung on it.

I looked for what tow vehicle you use, but couldn't find it. Also knowing your hitch setup would be helpful. If using weight distribution, how many chains are you using. Typical is 3-4 depending on setup. If needing to use more than that, would try to figure out why.

I will say that the kind of forces needed to really do this kind of damage isn't insignificant, so I still like the kid hanging from it theory better than over-hitching. IIRC way back in the day when I went on a couple of factory tours, I seem to recall some reinforcement behind those mounts.....I do not feel they are just screwed and caulked to the skin alone.

[ROBERT CROSS]

^
Based on how our SP's fit the profile of the panel they protect, I believe the differing contours of the two also cause quite a bit of stress.👎
I know it does take a LOT of twisting to get the two studs to line up with the holes in the panels. The difference being the stud brackets on 'Cloudsplitter' are riveted to a rib not a bare panel as is the hinge mount.👍

Bob
🇺🇸

[D-Rod]

You may consider drilling a hole at the ends of the crack to prevent the crack from traveling any further as you ponder the best solution for the problem. Good luck

[hhendrix]

It would be helpful to know your tow combination, truck and and weight rating of your WD system bars. A too stiff combination can cause stress fractures as the WD and truck suspension can literally beat the trailer to death. Is yours a front or rear bedroom. Another sign is on the front bedroom models, look for stress fractures at the bottom corners of the front compartment.

[BillfromWI]

I have the same year and FB model as you with about 47.000 miles (Datatrak Hubodomenter), including Alaska and Newfoundland. I have no sign of this problem. Did you buy yours new? Have you swung the rock guards out to inspect the entire stud mount?

I agree with hhendrix. On my way to my current rig (Andersen with GMC Duramax), I tried to make a Blue Ox correct for inadequate F-150 cargo capacity. It was clear that the setup that came closest to getting the TV axle weight ratings within spec was so stiff it would have shaken the trailer apart. Even so, the problem you have is about the last thing I would have expected.

Good luck!

[Tim A.]

You have received some good answers about possible causes for the problem. If it were my problem, here is how I would take care of the cracking already present:

Remove the support bracket from the Airstream panels by drilling out the rivets. Cut pieces of 1/16" thick aluminum sheet large enough to extend at least 1/2" beyond all of the present cracks. Shape the aluminum to fit the contour of the Airstream's panels. Drill the aluminum pieces to fit the support brackets. Using something like Sikaflex, liberally coat the backside of the aluminum pieces and rivet them and the brackets in place.

Doing this will reinforce the Airstream panels and using something like Sikaflex will give an elastic bond between the reinforcements and the panels.

Tim

[RivetED]

We had that happen to our 2004 Safari after Jackson Center installed the 'taller' rock guards. That was to cover a rock that hit just over the top of the lower (original) S/S rock guards, of course!

The earlier rock guards did not have the top center bracket/stabilizer.

When the trailer was back at J.C. for some other service they made a small patch and sealed it over the holes. When remounting they used a 6 rivet, not the original 4 rivet, brace with the foam type padding/gasket. The type that is now commonly used on production models.

Originally I did not want a patch but after I saw the work I was more than impressed with how good a job they did. Unless your were a very careful observer you would not notice it. The patch is mostly below the guard.

J.C. also used Olympic rivets to mount it for the extra holding ability of the 'legs' on the Olympics. They changed the other brace to a 6 rivet kind, foam gasket, and also used Olympic rivets.

This is a fairly common failure. Those rock guards are buffeted by the air flow on their front and from behind (the gap). Add in all the torquing of the body and the rough roads we drive over and those points of contact get a good workout.

[ttrout]

Interesting in that I have a similar problem but it is on the passenger side rock guard. On my 2003 28' Classic the bolt actually pulled out of the mounting bracket. Could turbulence from Rock Tamers be to blame, they are a new addition. I also replaced the bottom attachment bracket a couple of months ago.

[H_Mark]

A little more information - Front bed room. The trailer was new but interesting is that the weld of the tongue jack was fractured from the mount flange about half way around. The unloaded (no water, no cargo) tongue weight of the trailer is 883 lbs. The "bathroom scale" method tongue weight for loaded trailer came to about 940 lbs. After discovering the left panel fractured mount - the piano hinge top three machine screws were loose, top most being the loosest. On tightening the machine screws for the piano hinge in place, mounting the center rock shield bolt through the shield top center hole required much flexing of the rock shield. It seems the hole is about 1/4" off center of the bolt such that the bolt is pulled toward the piano hinge. There are no cracks on the lower front body panels. Front body sheet metal show no signs of bending, open seams or loose rivets. No leaking windows. There was side body panel leaking early on which lead to rotted floor (my wife stepped through the floor during trip packing, trip cancelled)- both covered under warranty by Airstream.

Tow vehicle is Ford F350. WD system is Equalizer 12K. The original 10K hitch WD bars were extremely flexed. The change made per consultation with Equalizer. Several comments mention too much WD harming the trailer which I am trying understand.

Again thanks for the helpful comments.

[ROBERT CROSS]

Appears a stiff lash-up and a stressed segment protector is the most likely cause.
IMHO a 3500 is overkill
We have a 2500 Burb, 1200lb TW. 1000lb bars on a Hensley hitch moving 720lb.
Light bars moving correct weight helps soften the lash-up.

Have you been to the scales?

Bob
🇺🇸

[panamerican]

Originally Posted by H_Mark

A little more information - Front bed room. The trailer was new but interesting is that the weld of the tongue jack was fractured from the mount flange about half way around. The unloaded (no water, no cargo) tongue weight of the trailer is 883 lbs. The "bathroom scale" method tongue weight for loaded trailer came to about 940 lbs. After discovering the left panel fractured mount - the piano hinge top three machine screws were loose, top most being the loosest. On tightening the machine screws for the piano hinge in place, mounting the center rock shield bolt through the shield top center hole required much flexing of the rock shield. It seems the hole is about 1/4" off center of the bolt such that the bolt is pulled toward the piano hinge. There are no cracks on the lower front body panels. Front body sheet metal show no signs of bending, open seams or loose rivets. No leaking windows. There was side body panel leaking early on which lead to rotted floor (my wife stepped through the floor during trip packing, trip cancelled)- both covered under warranty by Airstream.

Tow vehicle is Ford F350. WD system is Equalizer 12K. The original 10K hitch WD bars were extremely flexed. The change made per consultation with Equalizer. Several comments mention too much WD harming the trailer which I am trying understand.

Again thanks for the helpful comments.

I'm no engineer, nor do I play one on TV, but a fractured flange doesn't sound good. I have towed larger rigs with far less robust bars with a 3/4 ton truck for tens of thousands of miles and my rock guards and mounts don't look anything like yours in 15 years of travel.

The max hitch bar you need for that rig, is a 600lb bar, if that. You have a 1 one truck. If you had significant flex with a 1k bar (10% of the hitch capacity), you had that way too amp'd up. I have a similar sized trailer and though I do have some flex, I do with 800lb bars. Keep in mind that you are spreading the weight of the RV and the truck to each other, vs dead hitch, weight of the RV on the ball alone.

Given you have a rough riding 1 ton and massive bars, I am not surprised you are seeing front end issues. The forces it would take to fracture a flange tells me the coach has been or continues to be over hitched and being subjected to forces that the RV cannot handle. You do not have to diversify the hitch weight, your 1 ton can handle that entire weight on it's own, so having stiffer bars is only going to make a harsh ride, even more harsh for the RV. You only need a slight bit of flex to have a good connection for built in sway if you use a cam type sway. If you are using friction sway, in your case you can prob even forgo WD bars completely. If you had a 1/2 ton my suggestion would be to go with 600lb bars and distribute that weight, but you have a 1 ton.

As I said I run 800lb bars with my 3/4 ton on my smaller of the two. I also have an air hitch to soften the connection between the two vehicles.

I have never seen or heard of anything like what you are exp. I have to say, IMHO, your problem is with your connection and my guess is that unless solved things may not get much better. IMHO, and please take this at face value-- you are massively over-hitched for what you have.

[KevinFH]

Originally Posted by eubank

Maybe a nice patch would be best! Lots of vintage Airstreamers have fun creating interesting looking patches: Hearts, stars, animals, whatever! Then mount the guards right into the patch, serving as a much stronger location for it.


Lynn

Find a piece of 0.060 thk aluminum sheet.
Cut it in a 3.5" X 3.4" Square
Cut the corners so that they are rounded (R=1/2")
Rivet it on with using 8 rivets (four corners and for sides).

[H_Mark]

Originally Posted by panamerican

I'm no engineer, nor do I play one on TV, but a fractured flange doesn't sound good. I have towed larger rigs with far less robust bars with a 3/4 ton truck for tens of thousands of miles and my rock guards and mounts don't look anything like yours in 15 years of travel.

The max hitch bar you need for that rig, is a 600lb bar, if that. You have a 1 one truck. If you had significant flex with a 1k bar (10% of the hitch capacity), you had that way too amp'd up. I have a similar sized trailer and though I do have some flex, I do with 800lb bars. Keep in mind that you are spreading the weight of the RV and the truck to each other, vs dead hitch, weight of the RV on the ball alone.

Given you have a rough riding 1 ton and massive bars, I am not surprised you are seeing front end issues. The forces it would take to fracture a flange tells me the coach has been or continues to be over hitched and being subjected to forces that the RV cannot handle. You do not have to diversify the hitch weight, your 1 ton can handle that entire weight on it's own, so having stiffer bars is only going to make a harsh ride, even more harsh for the RV. You only need a slight bit of flex to have a good connection for built in sway if you use a cam type sway. If you are using friction sway, in your case you can prob even forgo WD bars completely. If you had a 1/2 ton my suggestion would be to go with 600lb bars and distribute that weight, but you have a 1 ton.

As I said I run 800lb bars with my 3/4 ton on my smaller of the two. I also have an air hitch to soften the connection between the two vehicles.

I have never seen or heard of anything like what you are exp. I have to say, IMHO, your problem is with your connection and my guess is that unless solved things may not get much better. IMHO, and please take this at face value-- you are massively over-hitched for what you have.

--------------------
Thanks for taking time to comment. I am going give this issue some serious consideration. Trying to interpret: a sturdier tow vehicle and more rigid WD hitch could induce extreme flexing into the front part of the trailer frame which would be transferred upwards into the body of trailer? If based on Equalizer's WD formula, the measurements were in spec, would this stiffer or more robust tow/WD hitch arrangement still be an issue? So no excessive weight distribution but excessively rigid or stiff WD?


On the fractured flange weld - perhaps a distracting issue? Not sure. That was the flange of the tongue jack. This was where the jack mount flange was welded to the vertical tube of the jack. My guess on that issue was that the trailer was supported on the tongue jack during transport to dealer and was subjected to a hard jolt or was the jack was not adequately raised during a move at the dealer thereby cracking the weld.

[guskmg]

You might ask an aluminum boat welder if he can weld up the crack. You may need reinforcement. It is amazing how good of a job a skilled welder can do.
guskmg