Floor repair in '76 mini motor coach

[jwestlake]

Hi all,

We just purchased a '76 mini motor coach, built on a Dodge B300 RV chassis. The floor is pretty shot out, rotten through to the bottom layer of plywood in some places I can see from underneath. I know there's a leak around the skylight that should be rectified soon (parts/materials on the way) and I'll be using Eternabond alumibond to cover the roof seams, so that should hopefully take care of any leaks from above so we protect the new floor going in.

I don't see evidence of a belly pan... is anyone familiar enough with these rare models to know if that's correct? The plywood on the bottom just appears to be painted with some sort of coating from what I can tell in a few spots.

We're going to be working back to front, starting with removing the bathroom, the bulkhead panel between the exterior door and the bathroom shower, and the panel/closet between the kitchen and bathroom (where the inverter sits underneath). I'm thinking by doing it in sections, we can minimize any issues with the interior skin settling without the floor support.

From there, we'd remove the middle section, including kitchen equipment and wardrobe (where the furnace sits underneath), and finally closer to the cab where the dinette and other chairs are.

Does this sound like a workable plan?

Also, I've seen a couple of posts say that they've been told not to bother replacing with foam, just an equivalent thickness of plywood. What's the verdict on that?

While we have things removed, are there any upgrades/improvements we should make? Thinking along the lines of upgrading water lines, etc.

Anything else we should know?

Thanks in advance!

(Edit: Drat... looks like the board is rotating all my pix to the side... sorry about that!)

[silverloaf]

Hi all,

We just purchased a '76 mini motor coach, built on a Dodge B300 RV chassis. The floor is pretty shot out, rotten through to the bottom layer of plywood in some places I can see from underneath. I know there's a leak around the skylight that should be rectified soon (parts/materials on the way) and I'll be using Eternabond alumibond to cover the roof seams, so that should hopefully take care of any leaks from above so we protect the new floor going in.

I don't see evidence of a belly pan... is anyone familiar enough with these rare models to know if that's correct? The plywood on the bottom just appears to be painted with some sort of coating from what I can tell in a few spots.

We're going to be working back to front, starting with removing the bathroom, the bulkhead panel between the exterior door and the bathroom shower, and the panel/closet between the kitchen and bathroom (where the inverter sits underneath). I'm thinking by doing it in sections, we can minimize any issues with the interior skin settling without the floor support.

From there, we'd remove the middle section, including kitchen equipment and wardrobe (where the furnace sits underneath), and finally closer to the cab where the dinette and other chairs are.

Does this sound like a workable plan?

Also, I've seen a couple of posts say that they've been told not to bother replacing with foam, just an equivalent thickness of plywood. What's the verdict on that?

While we have things removed, are there any upgrades/improvements we should make? Thinking along the lines of upgrading water lines, etc.

Anything else we should know?

Thanks in advance!

(Edit: Drat... looks like the board is rotating all my pix to the side... sorry about that!)

It sounds like the quite the project.

I do have a comment about the chassis. Unlike Ford and GM, the Dodge vans were a unibody body construction; there was no frame. All of the strength and support came from the floor pan. The edges of floor pan were bent into a box section to provide the stiffness for the powertrain and body.

As part of your diagnostic and teardwn process, I suggest you look at the floor for signs of rust. If the plywood floor is rotted, the moisture could have caused some issues with the floor pan.

I'm curious to learn what you find.

Bob

[jwestlake]

Hi Bob,

That’s interesting to know about the unibody. The only floor pan I’ve physically seen is the one in the cab, which seems to be in pretty good shape from what I’ve seen so far. I don’t see anything like that under the cabin, though I haven’t crawled all the way under it.

Assuming there’s no pan of any sort under the cabin plywood, what do you think might be the best method of protecting it? Some sort of exterior paint, or maybe that rubberized paint? Looks to me just to have a dark paint of some sort on it now.

Getting all our ducks in a row this week, tools and materials-wise, so maybe this weekend we can actually move forward (assuming there’s no rain...)

Thanks for the reply!

[Razorback]

I would suggest the Automotive Coating that comes from reRubber to coat just about anything under your motorhome. And, to eliminate any self-promotion (because I can sell the stuff), you can contact reRubber directly. Check out this post... viewtopic.php?f=9&t=567...... it has Ken Winters' contact information. He'll be glad to fill an order.
The Automotive Coating or the Rubberized Primer would do a good job. The Automotive Coating is a bit thicker and more of a black color compared to the Rubberized Primer's dark grey color. The thicker consistency is good if you are under a vehicle with a brush. As with any coating, a good clean surface will provide the best results. Even if you have an exposed plywood surface under the MH, the coating will protect it nicely.

[jwestlake]

I would suggest the Automotive Coating that comes from reRubber to coat just about anything under your motorhome. And, to eliminate any self-promotion (because I can sell the stuff), you can contact reRubber directly. Check out this post... viewtopic.php?f=9&t=567...... it has Ken Winters' contact information. He'll be glad to fill an order.
The Automotive Coating or the Rubberized Primer would do a good job. The Automotive Coating is a bit thicker and more of a black color compared to the Rubberized Primer's dark grey color. The thicker consistency is good if you are under a vehicle with a brush. As with any coating, a good clean surface will provide the best results. Even if you have an exposed plywood surface under the MH, the coating will protect it nicely.

Thanks! I'll definitely look into that. Was the price you got ever quoted?

What was your application method? Just get under there with a paint brush, or did you have it sprayed?

[silverloaf]

Hi Bob,

That’s interesting to know about the unibody. The only floor pan I’ve physically seen is the one in the cab, which seems to be in pretty good shape from what I’ve seen so far. I don’t see anything like that under the cabin, though I haven’t crawled all the way under it.

Assuming there’s no pan of any sort under the cabin plywood, what do you think might be the best method of protecting it? Some sort of exterior paint, or maybe that rubberized paint? Looks to me just to have a dark paint of some sort on it now.

Getting all our ducks in a row this week, tools and materials-wise, so maybe this weekend we can actually move forward (assuming there’s no rain...)

Thanks for the reply!

I spent some time trying to find a picture of the 1976 B300 van-cab chassis. Here is a YouTube video of one. The guy is trying to convert it into something other than its original intent; hence, the steel cross- members.
https://www.youtube.com/watch?v=gnvsIfQFhbU

The light gray platform under these cross-members is the floor pan. Note how the edges of the stamped pan are formed into a box. It is the structural part that mimics the standalone frame found on Ford and GM vans. The powertrain, chassis and body live or die by the strength and integrity of this sheet metal box section.

The Avion floor likely rests on the box sections. Any moisture trapped between the wood and box could result in rust perforating the top edge of the box section.

I suggest taking a serious look at this intersection of wood and metal as you progress through your rebuild. While undercoating might be worthwhile, polishing a turd with it is not in your best interests.

My goal here is to offer suggestions on making your camper safe, not to throw manure at your vintage project. For further clarification, I suggest a trip to your local Dodge dealer and talk to an old-timer about the B300's nuances.

Bob

[jwestlake]

Hey Bob,

Thanks for that video... definitely shows me what to look for. I'm pickin' up what you're layin' down. I'll get up under there deeper here soon to see what I can see, and try to get some pix. It's been rainy in the afternoons, so I haven't done much outside lately... hope to change that soon.

Thanks again!

[Razorback]

I would suggest the Automotive Coating that comes from reRubber to coat just about anything under your motorhome. And, to eliminate any self-promotion (because I can sell the stuff), you can contact reRubber directly. Check out this post... viewtopic.php?f=9&t=567...... it has Ken Winters' contact information. He'll be glad to fill an order.
The Automotive Coating or the Rubberized Primer would do a good job. The Automotive Coating is a bit thicker and more of a black color compared to the Rubberized Primer's dark grey color. The thicker consistency is good if you are under a vehicle with a brush. As with any coating, a good clean surface will provide the best results. Even if you have an exposed plywood surface under the MH, the coating will protect it nicely.

Thanks! I'll definitely look into that. Was the price you got ever quoted?

What was your application method? Just get under there with a paint brush, or did you have it sprayed?

The quoted price for the Automotive Coating is $62/gallon, $294 for a 5-gallon pail, plus shipping.

I have simply used a brush to coat anything I have used the Automotive Coating on, although it can be sprayed or rolled on as well.

[polcat]

What ever happened with this re-floor? We were fortunate to find one with very little rot out, only under the water heater and refrigerator.

[Razorback]

Wow!!!! That is a beautiful motorhome!!!!