DIY Repair for Broken Wall Welds from Frame Flex

[Planenut99]

2019 Montana 2131RL

OK, so I noticed a bulge in my outside sidewall just below the bottom front corner of the bedroom slide. While I do not have a crack in the fiberglass, I was sure that I had the dreaded broken welds on the studs. After reading all the posts here, and being as particular about who works on our rig, I decided to undertake this myself. I would not have done this without all the information and pictures that the people of this site have posted. I am an aircraft mechanic by trade so I have some mechanical skills. This is the story of my repair. It’ll probably take a couple of posts.

I decided to gain access to the area from inside the rig instead of the outside. The outside repair seemed too invasive and my fiberglass siding isn’t damaged. I removed the bed and the bed platform to give myself some working space. I also removed the closet roofs and the bottom closet door track. I cut the inside paneling level with the lower edge of the cabinet countertop so that I could hide it with trim later if I need to. I cut next to the shelf and along the floor line using an oscillating saw. There is an area of metal adhered to the back side of the paneling where the doors hit and the hold close is screwed. It cuts a little harder but the saw will cut it, just be careful of the two aluminum studs in the wall. One is next to the in-wall actuator ant the other is about 15” forward of that. After carefully peeling the paneling off and cutting/prying the foam out, I found that both studs were broken off at the bottom. I was able to hit the outside with a wood block and hammer and get them back into place. I also decided to gain access to the outside underneath. I pulled the lower front cap trim strip, the left side trim and the cover screws around the hitch area. I managed to peel the skin down far enough on the left side to see what was going on. After cleaning up the debris, insulation, and a few old mud dauber nests, I found the screws attaching the steel frame to aluminum frame loose. This also gave me a chance to slide a pry bar between the skin and the frame and get all the debris between them out.

 

[Planenut99]

Now it was time for the repair. I decided to make a bent angle with a riveted gusset for each stud to hold the studs in place. This was my idea of the aluminum welded gusset in TSB 180328. The studs were 1 1/2” wide so I wanted to use the heaviest aluminum angle that I thought I could bend 90* (degrees). I found a couple pieces of 1/8” X 1 1/2” X 10” long aluminum angles in my stuff, cut a 45* angle out of the middle and bent it 90*. I then used a piece of 0.063” 2024-T3 aluminum sheet, fabricated a triangular gusset, and riveted it to the angle. I made two out of stuff I had laying around. After grinding the broken weld enough to allow the radius of the angle gussets to fit tightly to the studs, I used Henkel EA9309.3NA aviation grade aluminum structural adhesive and CherryMax rivets to attach them to the studs. I then added 3 2X4’s with pocket holes and screws above the angle gussets. These were coated with Loctite PL MAX adhesive on the ends and the contact area of the outside wall. Once it all set up, I don’t think it’s going anywhere.

 

[Planenut99]

 

[Planenut99]

Lastly, when I went to close up the hitch underbelly, I ran into some issues. The trim between the front cap and underbelly had stripped screws, lots of sealant, and the insulation was in poor condition. I cleaned out the insulation and replaced it with new. I found there were two 1 X 3/4” boards laying loose. I realized that these were needed to hold the underbelly skin and had come loose from the closet floor. I reattached the 1 X 3/4’s with some deck screws and reinstalled the hitch underbelly skin. I had to straighten the trim molding and turn it around so that the holes were in a new place and use new #4 stainless screws through the fiberglass cap into the plastic skin. If you carefully straighten the aluminum trim, it can be reformed like the factory does it. They put two screws in and then bend it to the next screw, screw it, and move to the next. This worked OK and looks factory again. Once everything was installed and tight, is was a sealing party on all the seams. I had purchased several hundred #8 and #10 stainless screws from Amazon and installed them in place of all the square drive self drilling screws. My plan is to work my way around the rig and replace everything with stainless.

 

[Planenut99]

Still need to have that sealing party but it’s been blazing hot here.

 

[Carl n Susan]

Nice work!!!!!

 

[mtheo]

Good explanation

 

[scottz]

Nice job, nice write-up. Looks like an aircraft repair.

 

[John and Barbara]

View attachment 2500808
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Still need to have that sealing party but it’s been blazing hot here.

I'm an A&P also, But sir, Your also an Engineer. That work is awesome.

 

[Mikendebbie]

WOW! This is great info and good work!
I have some questions…
1. In post #2 above you describe “the in wall actuator” - I am not familiar with this term.
2. The 2x4 blocking…What is the species of the wood blocking? Treated?
3. You left the wood blocking out of the bottom space where the gussets attach to the wall…what was your thinking behind that decision?
4. The rivets that attach the gussets to the aluminum studs and bottom member…are they short so that they only grab one face of the stud? Or are they long to go all the way thru the stud?
5. Just curious about the duration of the project…did you work straight thru day after day? Or a little bit each day over a week (for example)

 

[Planenut99]

WOW! This is great info and good work!
I have some questions…
1. In post #2 above you describe “the in wall actuator” - I am not familiar with this term.
2. The 2x4 blocking…What is the species of the wood blocking? Treated?
3. You left the wood blocking out of the bottom space where the gussets attach to the wall…what was your thinking behind that decision?
4. The rivets that attach the gussets to the aluminum studs and bottom member…are they short so that they only grab one face of the stud? Or are they long to go all the way thru the stud?
5. Just curious about the duration of the project…did you work straight thru day after day? Or a little bit each day over a week (for example)

The actuator in the wall is the Lippert Schwintek slide drive system. One of the highest failure rate slide systems out there. If there is any binding in the slide, the drive will fail.

The 2 X 4’s were standard house studs. Actually from scraps I had around. No treatment since they should never get wet.

The gussets provide most of the structural strength so I really wasn’t worried about jamming a piece of wood in there. I did stuff it with some fiberglass insulation before I closed it up. I reattached the inside panel with spray glue and a few screws so I can access it easily and inspect it in the future.

The rivets are an aerospace fastener (CherryMAX) used where you cannot access the back side to buck a solid rivet. They are specialized rivets with a locking system to prevent the from loosening and they only penetrate the one side of the hollow aluminum tube.

I recently retired from managing a large aircraft repair shop and “upgraded” to this Montana. I enjoy working with my hands and fixing things so this was a bit fun for me. But to keep it fun, I only worked a few hours a day over the course of about a week. It’s been really hot lately so I work outside in the morning and inside with the AC later in the day. I have a lot of projects so III am still busy working on it. I can’t tell you how many nights it took to come up with this repair idea.

I’ll try to post about the broken water tank that I had to replace

 

[scottz]

A little off topic, but educate me on the strength of rivets vs welding.

 

[Planenut99]

I think welding is fine but I wasn’t about to remove the outer skin like the TSB instructed to just to weld. Definitely a better method because I could have rewelded the broken stud welds too. I’m hoping that my repair is sufficient and was done by internal access only.

 

[Mikendebbie]

A few more questions...
1. You stated "After cleaning up the debris, insulation, and a few old mud dauber nests, I found the screws attaching the steel frame to aluminum frame loose." I'm having a hard time figuring out where these screws were located so that you could tighten them. Do they show up in any of your photos?
2. In addition to riveting the gusset plate to the aluminum angle - did you use the adhesive to glue the angle face to the plate?
3. I can see (what I believe to be) red adhesive glueing the angle backs to the studs (and I assume the base tube) - correct? Did you glue the backs of the 2x4s to the fiberglass exterior panel?
If you go outside and push on the fiberglass skin at the wood blocking - does it feel solid like the rest of the wall?

 

[Planenut99]

The loose screws have a #3 Phillips head and hold the aluminum wall down to the steel frame. There is a flange welded to the bottom of the tubular steel frame that extends outward to hold the bottom of the wall. Some people have found the welds broken or cracked but mine were not. They can be seen in this picture with the yellow marks. Per my writeup, the angle faces were bonded to the studs using an aviation grade adhesive and the 2 X 4’s with adhesive from Home Depot. I did not bond the gusset plate to the angle as the rivets should provide enough strength in the shear mode. Both adhesives will come up if Googled. The wall feels very solid on the outside.

 

[Mikendebbie]

...and the questions just keep coming!
- I am not familiar with CherryMAX rivets. Apparently, they are common in the aircraft industry, and they are expensive (by my money tree standards!). I think I found bags of 100 rivets for about $300...but I'm not sure what size is correct. Do you have a rivet size and a source for buying?

- I think you put about 20 rivets in each gusset + another 8 to 10 thru each gusset to the studs.
Are the rivets used for the gusset-to-the stud the same as you used for the gusset build? If they are all the same - then a 100 rivet pack would be about right.
- Can they be installed with a "normal" hand rivet puller?

 

[Planenut99]

I used CherryMAX rivets that I had. Yes they are quite expensive. Cherry has a guide for drill size and grip length. Watch out for the oversized. They are designed to fix a slightly larger hole and take a different size drill. I took pictures of the size card that I have. I’ve pulled -4’s and -5’s with a good pop rivet tool but you need some good hand strength. It took everything I had to get a -6 to pull. I don’t suggest that without a hydraulic puller.

I only used them attaching the angles to the RV structure. There were 16 total and different sizes. Again, what I had. The gusset is held with countersunk solid rivets squeezed with a pneumatic rivet squeezer.

 

[Mikendebbie]

Thankyou!
This is excellent info for those that want to attempt the fix themselves like you did.

Being a retired construction estimator - I made a parts list with budget costs (perhaps to compare to out-of-pocket Affinity Repair Group fix) I would need to buy about $650 of stuff...

My labor and sweat equity is FREE!
Please add or correct any item you see fit...

Tools I have on hand:
Oscillating saw -
Screw gun and drill bits -
Dremel with a point grinder -
Hammer –
Jig saw -
Caulk gun for Locktite adhesive –
Flat Pry bar -
Bench vise -

Tools I would have to buy:
Hand rivet puller (not sure I have the right type) – Harbor Freight $50
I don't have a pneumatic rivet puller, so I would have to make do with standard puller
Pocket hole mini-jig and bit – Lowes $30
Non-ferrous saw blades for jig saw – Lowes $20

Materials to buy:
2x4 – 8’ wood non-treated – Lowes $10
Aluminum angle – 4’ long 1.5”x1.5”x 1/8” - Lowes $35
Aluminum plate – 12”x12” x 0.063 (not sure where to find this, maybe a local metals shop) - $50 ?
Henkel Loctite 2-part epoxy adhesive – online - 50 gram EZ pack - $50
CherryMAX rivets – 100 rivet pack – online $300
Loctite PL Max adhesive for wood – Lowes - 1 tube - $20
#8 x 1” SS screws – 1 box – Lowes $20
#10 x 1” SS screws – 1 box – Lowes $20
Pocket hole screws – 1 box – Lowes $20

TOTAL $650

 

[Planenut99]

So, a few things to note; Drilling the horizontal holes to attach to the studs down inside a 1 1/2” cavity is a clearance problem. I used a specialty 90* angle drill. You wont fit the average cordless drill in there and get a straight hole. Regarding the CherryMAX rivets, if I didn’t have them, I had thought about using stainless steel pop rivets or even self drilling screws. I believe there is a lot of strength in the adhesive and the addition of a good fastener to keep the joint tight while setting up and also to provide some sheer strength is probably all that is needed. Either of these is a much cheaper alternative.

Attaching the gusset to the angle might need some additional thought for you. Aviation countersunk rivets are 100* where general industry is 90*. If you were to use countersunk pop rivets (90*) then your gusset would need to be thick enough to countersink your hole and not leave a knife edge in the hole. If you purchase and use aviation solid rivets (100*), then you need to buy the proper countersink tooling. The rivets can be set using a hammer and punch while the head is laying on a flat solid surface like an anvil or vise. I could walk you through that process if needed. If you know any A&P’s, they might help or loan you the tools. If you have a local A&P school, you might get the gussets mad as a school project.

If you do decide to try this, I’d be glad to have a phone conversation and provide some guidance. I am no expert but I do sympathize with those that have suddenly found that they have cracks in their frame and may be looking a thousands to have it repaired. I know that I panicked at first!

 

[Mikendebbie]

Thankyou! Fortunately I do not have any broken welds - yet. I just wanted to make this thread as complete as possible for those who may be contemplating a DIY approach.