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Topic: Fixing minor rear end wood damage in 2001 MB (Read 492 times) previous topic - next topic
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Fixing minor rear end wood damage in 2001 MB
Hi! I've been working on resealing the back end caps on my 2001 mid-bath, and discovered a bit of wood damage. On the right side the 2x6 sandwiched in the bumper is rotten on the last 12 inches or so on the passenger side, and maybe half that on the driver side. On the passenger side it also extends up above the 2x6 about another 6 inches of the corner wood piece. The rot gets pretty close to the right lower ladder mount, but everything feels sound. I'm not sure what kind of structural support the corner piece supplies. I removed the rear paneling in the rear storage compartments, and everything looks clean except at the bottom of the very ends. I haven't removed the left bottom end cap yet but will do that once back from a week camping down the coast.

I've been reading the forum threads on some pretty intrepid efforts at rear end rebuilds, and that all looks pretty daunting, and I was wondering if it's possible to do something more minor in this case since the damage looks limited. I'd love any advice on this. Cut out a little more wood and shove a foot of 2x6 up in the gap using the screws of the right bottom ladder mount to hold that in place? Just foam in some insulation? We've had this coach since the beginning and it's in pretty good shape otherwise.

Thanks!

Larry
Larry K
2001 Mid-Bath
Re: Fixing minor rear end wood damage in 2001 MB
Reply #1 –
I haven't done any fixes on that area, and honestly I'm scared of finding out what damages I might have under the end caps!

I've seen those daunting renovations and they seem like a loot of work. Although they seem well worth it.

I feel like if you manage to cut off the rotted areas and shove a replacement piece of wood and somehow manage to also screw or nail it in place that should do it. But it seems like that may require the back aluminum panels to be removed in order to screw it in place properly.

I would not use foam filler since that's not so structural. Instead for a possible easier solution, I would look into using epoxy since that will harden super hard to become structural or so I would think....
1995 23.5 Rear Lounge
 
Re: Fixing minor rear end wood damage in 2001 MB
Reply #2 –
Thanks, I like the idea of epoxy resin. I'd just need to figure out a way to contain it, but that would make a good seal as well. I wonder if anyone has tried that here? I'm guessing any end cap leakage, for this model at least, may result in water pooling on top of the 2x6 inch bumper board, resulting in this kind of minor rot. An RV shop resealed my back end caps about 10 years ago, with silicone sealant (!), which has since separated, and probably caused the leaks. It has taken a while to remove this old caulking, I'm planning on using the 3M 5200 to reseal.
Larry K
2001 Mid-Bath
Re: Fixing minor rear end wood damage in 2001 MB
Reply #3 –

If mine, I would remove the entire 2X6 across the bottom of the wall, or as muchrotted wood as possible. It helps support the bumper, extremly important if you tow.
Replace all of the 1/4 carriage bolts that secure the bumper to the rear wall. I use a vibratory tool with a metal cutting blade to cut through any staples or wood that is in the way. Before installing the new wood, treat the wood with a preservative or paint it with a paint primer, to seal the grain.

Do the same in the corners, make a flush, flat cut where the ‘good’ wood begins and replace the bad  with the same size wood. Seal it too. Yellow carpeters glue is fine or use a polyurethane to glue thngs in place. Gorilla glue is good too but wear disposable gloves, it badly stains skin
Make sure he window is leak free, they leak around the perimeter of the frame and around the smaller window. If water is leaking arounf the wind panes, the rubber molding  can resealed with a special silicone made for this purpose.
Amazon.com: Permatex 81730 Flowable Silicone Windshield and Glass Sealer,...

I glue the caps in place using 3M 520 FastCure and add #8 stainless steel screws where ever they are needed to pull the caps tight.  The Mothership uses screws on the caps too, if needed during construction.



Larry

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Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Fixing minor rear end wood damage in 2001 MB
Reply #5 –
Thanks for the feedback! Larry: the idea you'd suggest is to cut out the existing board with the bumper in place, then slip a new 2x6 in? Or would you need to pull off the bumper too? The rot is confined to the last foot of the 2x6, and just a half inch or so of the corner wood piece going up about 6 inches. I have a reciprocating saw, but not sure I want to take that to the 2x6...

I looked into epoxy, but a 2x6x12 chunk would get excessively hot. However, it seems that an epoxy paint on the bottom of the 2x6 would work to seal it from the elements.

I had my first experience with the 3M 5200 today, sealing the upper end cap, and the outside edges of a few windows. I could only get the cartridge size, so was thinking of using it to seal the exposed wood under the end caps. Pretty messy stuff, but fun; glad I had the box of nitrile gloves, went through about 20 pair messing with this.
Larry K
2001 Mid-Bath
Re: Fixing minor rear end wood damage in 2001 MB
Reply #6 –
[quote author=larkenyon link=msg=239519 date=1642396543

the idea you'd suggest is to cut out the existing board with the bumper in place, then slip a new 2x6 in? Or would you need to pull off the bumper too? The rot is confined to the last foot of the 2x6, and just a half inch or so of the corner wood piece going up about 6 inches. I have a reciprocating saw, but not sure I want to take that to the 2x6...

I looked into epoxy, but a 2x6x12 chunk would get excessively hot. However, it seems that an epoxy paint on the bottom of the 2x6 would work to seal it from the elements.
I had my first experience with the 3M 5200 today,[/quote]

If only a small section of the bottom board at each end is rotted, I leave the bumper in place. After removing the 1/4” carraige bolts securing the bumper to the rear wall, cut the rotted section out and graft in a new piece. Replace the carriage bolts, the ones in the rotted section will be rusted.
To make a clean, straight cut in the 2X6, I use a vibratory tool with a 1” wide wood/metal blade. It allows cutting away the rotted 2X6 between the inner and outer walls without damaging the walls.
Once the 2X6 replacement is trimmed to fit, coat the inside of the inner and outer walls with adhesive to bond everything together. Immediately, install the new 1/4” carrigage bolts, clamping the repaired wall.

The Factory seals the bottom of the rear wall with asphalt undercoating, it seals the wall so well that water entering through a leaking end cap or window gets trapped inside the wall, leading to more rapid rot. Water needs a way of escaping if it gets around the seals, I prefer to paint the new wood and avoid totally sealing the bottom of the wall. Sealing the bottom of the wall with epoxy might have the same effect as the Factory’s undercoating.

3M 52000 FC, yes use lots of disposable gloves and wear old, painting-type clothes. When using 5200, I wear two or three pairs of disposable gloves, discarding the top pairs when contaminated.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Fixing minor rear end wood damage in 2001 MB
Reply #7 –
Thanks Larry! The vibratory tool is different than a reciprocating saw, or same thing?

Heading down the coast to camp a bit this week before getting back into this (Morro, Jalama). I did use the rest of the 3M cartridge to seal the exposed wood under the end cap, maybe overkill but looks nice; will go "end-cap-less" this week, weather looks great :-)
Larry K
2001 Mid-Bath
Re: Fixing minor rear end wood damage in 2001 MB
Reply #8 –
Quote from: larkenyon  - 
The vibratory tool is different than a reciprocating saw, or same thing?

Also called an Oscillating Multi-Tool.  Much more precise than a reciprocating saw.  It's the right tool for this job. 

The Home Depot Logo

Cheap Harbor Freight corded version.
https://www.harborfreight.com/2-amp-variable-speed-oscillating-multi-tool-57808.html

You also need a blade (cheap version):
https://www.harborfreight.com/1-18-in-bi-metal-plunge-blade-for-oscillating-multi-tools-61812.html

If you're a tool person, buy the cordless version of the brand you prefer (or have batteries for).  I guarantee you will wonder how you ever lived without it.

Rich

2003 MB
Re: Fixing minor rear end wood damage in 2001 MB
Reply #9 –
Quote from: larkenyon  - 
Thanks Larry! The vibratory tool is different than a reciprocating saw, or same thing?

For two decades, the German tool company Fein held the patents on oscilating tools, I had used them at work but could not see spending several hundreds dollars buying one.
When the patent expired, prices dropped and I bought the first Rockwell oscillating tool to hit the market and have loved what it can do ever since. No other tool can do what it does.
The Home Depot Logo

This the blade I would use to cut out the rotted sections of the bottom 2X6.
The Home Depot Logo

This is the blade to use when removing any roof sealant, keep it sharp.
https://www.homedepot.com/p/Dremel-Dremel-Universal-2-in-Flexible-Scaper-and-1-57-in-Rigid-Scraper-Oscillating-Multi-Tool-Blade-2-Piece-MM620U/315677601

There are a multitude of different blades for wood, metal, tile, grout, drywall and more. It’s a tool every RV and home remodeler needs.

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Fixing minor rear end wood damage in 2001 MB
Reply #10 –
Sounds great, thanks for enlightening me :-) It’s always nice when you have the right tool. Reminds me of fixing my old VW bug in the early 70s, there was a book that told you exactly what you needed (and supplied some encouragement ;-)
Larry K
2001 Mid-Bath
Re: Fixing minor rear end wood damage in 2001 MB
Reply #11 –
Quote from: larkenyon  - 
Sounds great, thanks for enlightening me :-) It’s always nice when you have the right tool. Reminds me of fixing my old VW bug in the early 70s, there was a book that told you exactly what you needed (and supplied some encouragement ;-)

How to Keep your Volkswagen Alive for the Complete Idiot, by John Muir, was one of the first auto repair books I bought. It’s still out in the garage, it taught me the basics of VW repair and engine rebuilding and turned into a small college business and a long-term hobby. VWs were basic cars and didn’t require a fortune in tools to work on…ah, the good, old days when car were simpler….and smog producers and not crash worthy.
https://www.thesamba.com/vw/archives/books/idiotsguide.jpg

Larry
Larry
2003 23.5' Front Lounge, since new.  Previously 1983 22' Front Lounge.
Tow vehicles  2020 Jeep Wrangler Rubicon, 2001 Jeep Cherokee
Photo Collection: Lazy Daze
Re: Fixing minor rear end wood damage in 2001 MB
Reply #12 –
Ah yes, brings back memories :-) My copy was pretty oily, scanned it a couple years ago before discarding. I had never worked on cars, after a couple years with that book I even did the engine rebuild on my ‘66 sedan (guess I monopolized the front porch of the house I was renting with two other guys, but it worked out).  I guess nowadays it would be a collaborative wiki with links to YouTube videos :-) Loved his diagrams, best how-to book ever. I still have some of the tools.
Larry K
2001 Mid-Bath
Re: Fixing minor rear end wood damage in 2001 MB
Reply #13 –
Ok, ordered the Rockwell tool and blades, looks like it will be very useful. Can I use the roof scraping tool to help remove end caps too? That bottom end cap was glued on with some pretty thick grey gummy substance that required a lot of effort to cut thru with a putty knife. Thanks for all the help!
Larry K
2001 Mid-Bath
Re: Fixing minor rear end wood damage in 2001 MB
Reply #14 –
Some remnants of the gray goo show up in this photo. I used the 3M to seal the upper end cap without removing it since at the top it slides under the roof sealant LD used when resealing the roof 10 years ago, and I didn’t want to compromise that. I think I was able to remove all the silicone sealant that my local RV place had used 12 years ago (scraping with a putty knife, then plastic razor blades, MEK, 400 grit sandpaper, more MEK. I also started sealing around the windows, but using Lexel around the tan places (harder to get a good bead, but clear, and hard to see). Larry, you mentioned window leaks: is that the inner window where the pane meets the rubber? Is the symptom leaking into the unit? So far I haven’t seen any of that.
Larry K
2001 Mid-Bath