covering ribs with plywood

[druidwood]

Hello. I have seen a couple of pictures of people who covered their ribs with wood so they could attach the ceiling without forming a thermal bridge. Running wood front to back would be easy, but figuring out how to do it side to side has me stumped. How did they get the wood to bend. Is there a type, thickness of wood that works? Do you score the back? If you have prepped your ceiling in this way can you please let me know your technique? I plan to put 1/4" cedar tongue and groove on the sides and decorative tin down the center. Thanks.

[Dizzyman]

There are several ways but if I understand your question correctly let me direct you to Curious George’s build thread, he had a novel method.

His build thread is: http://www.skoolie.net/forums/f11/4-...ner-18205.html

Look for the last pic in post #289.

[Mgulley82]

We used plywood

Episode 6 - Skylights, Furring Strips and Random Fun https://youtu.be/8a9yToA5MEk


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[druidwood]

Thanks MGully82. You have lots of good helpers there! I see your post was recent, and was wondering what you planned to use for the ceiling and if you have started that? Was going to do cedar tongue and groove on the sides and wondered how pieces would lay across 2 furring strips (since angled) or perhaps the trick is to make them the same width as the tongue and groove so each piece sits flat? Not sure the tongues and grooves would line up though. Or maybe using that adhesive insulation strips cut to lay front to back between the two pieces to sort of smooth it out?

I hope someday to replace the escape hatches with opening skylights (this will be how I get on the roof) so that was of interest too.

[druidwood]

Thanks Dizzyman. Another way to go attaching to side of ribs.

[Mgulley82]

We are installing pine tongue and groove. I assume I may need to modify the tongue and groove a bit around the initial tight radius. Also the first three sections of the curve are with pieces of plywood the same width as the tongue and groove so hoping that helps.

We will be spray foam insulating the roof


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[dbhost]

I haven't done it myself in a bus, but I have done curved ply faces on furniture in the past. The process is done one of a couple of ways.

#1. Steam bending.
Or...
#2. Kerfing.

Both have advantages and disadvantages. For a bus ceiling. I would probably line up firring strips front to back, and then insulate, and lay in thin, like 1/8" ply veneer, using something like a Vicks Vapo Steam machine, just get the interior good and steamy, and apply the ply / veneer to the ceiling...

I believe Steampunk Steve on Youtube did something like that in his bus build. Awesome series to watch if you want to get some ideas...

[trueheart]

I've been told you can buy bendable plywood. It's apparently made by glueing all the layers with the grain running in the same direction, I think. I'll be checking it out for my ceiling, as well, and plan on running it side to side.

[Twigg]

Couple of thoughts ...

First is that the "bendy" plywood is $75 per sheet!

The way I plan on doing this is by ripping 8 x 4 sheets of ply into 2" strips.

The first strip will cover the bulk of the ceiling rib (all except the tight curve), and be glued and screwed to the rib. I may or may not add some insulation there too

Then two subsequent strips will be glued to the first one. That should give 3/4" to fasten into and break the thermal bridge about as well as I can.

It's not necessary to cover all of the curve, so short strips can be added to the sides in the same manner.

[o1marc]

I'm envisioning band saw cut pieces for the curves of the rib and straight pieces (2x2) for the long runs and then securing them to the sides of the ribs before insulating. That way I lose no roof height adding another sunroof. The ceiling material will attach to the side of the ribs, wood to wood.

[dbhost]

Originally Posted by Twigg

Couple of thoughts ...

First is that the "bendy" plywood is $75 per sheet!

The way I plan on doing this is by ripping 8 x 4 sheets of ply into 2" strips.

The first strip will cover the bulk of the ceiling rib (all except the tight curve), and be glued and screwed to the rib. I may or may not add some insulation there too

Then two subsequent strips will be glued to the first one. That should give 3/4" to fasten into and break the thermal bridge about as well as I can.

It's not necessary to cover all of the curve, so short strips can be added to the sides in the same manner.

Just a thought, glue and reasonably short pins should be a good strong bond assuming you are using good quality glue and prep. The problem is going to be making the bend across the ceiling if you are going to furr that way...

[o1marc]

No one really mentioned what kind of "plywood" in talking about bendable. There is Luan and thin plywood sheeting in as little as 1/8"-1/4" thickness that is easily bendable for curved ceilings. But then I realize you are talking about using bendable slats of plywood secured to the rib faces as a sub ceiling to secure the final ceiling.

[Twigg]

Originally Posted by dbhost

Just a thought, glue and reasonably short pins should be a good strong bond assuming you are using good quality glue and prep. The problem is going to be making the bend across the ceiling if you are going to furr that way...

I've debated furring across the ribs (and there's not too much bend) or furring lengthwise. Titebond II would work well for the glue.

I have the ceiling height so I can go either way.

What are the pros and cons of each?

[o1marc]

If you need stiff wood bent, one way is to cut reliefs on the back side about 3/4-7/8 of the thickness of the board. It leaves "V" shaped openings on the back that someone will surely bring up an issue with no insulation in that cavity, but it is so minimal I wouldn't be concerned.

[2martins]

Originally Posted by dbhost

I haven't done it myself in a bus, but I have done curved ply faces on furniture in the past. The process is done one of a couple of ways.

#1. Steam bending.
Or...
#2. Kerfing.

Both have advantages and disadvantages. For a bus ceiling. I would probably line up firring strips front to back, and then insulate, and lay in thin, like 1/8" ply veneer, using something like a Vicks Vapo Steam machine, just get the interior good and steamy, and apply the ply / veneer to the ceiling...

I believe Steampunk Steve on Youtube did something like that in his bus build. Awesome series to watch if you want to get some ideas...

Having looked at some ceilings I am hoping this approach works. I am also going to TRY to cut the edge of each piece at an angle so that it overlaps the one next to it rather than having a butt joint. And then if it still looks bad, I'll TRIM! I have a halfway decent steamer....

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[Twigg]

Originally Posted by 2martins

Having looked at some ceilings I am hoping this approach works. I am also going to TRY to cut the edge of each piece at an angle so that it overlaps the one next to it rather than having a butt joint. And then if it still looks bad, I'll TRIM! I have a halfway decent steamer....

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Does it matter what it looks like? You will be covering it. It just needs to be solid.

[2martins]

Originally Posted by Twigg

Does it matter what it looks like? You will be covering it. It just needs to be solid.

I don't mean the furring strips, I mean the actual bendable, but pretty nice birch plywood on the ceiling.

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[Twigg]

Originally Posted by 2martins

I don't mean the furring strips, I mean the actual bendable, but pretty nice birch plywood on the ceiling.

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Gotcha.

All you can do is test it.

Home Depot currently has some 2.7mm ply that will bend around and looks very decent on the sanded side. Not birch though, which is a ply I like too.

[OldWardBus]

I'm really liking this wood to wood idea, and I have actually sketched an idea very similar to what o1marc is describing. Vertical extensions or webbing of sorts, made of wood, that are secured with horizontal fasteners to the side of the ribs. Perhaps just something as simple as 2x4 nubs cut slightly longer than the height of the ceiling or wall rib. Place them anywhere you are going to secure a wall, cabinet, panel, etc. Then, insulate. You're left with a series of wooden points to secure anything a screw will hold it to. The inner covering of whatever you choose can be secured to it and easily be removed in the future without bothering ribs or insulation. The screws are isolated, as is the inside skin. this would seem to also allow a certain inherent air gap to allow any condensation to evaporate and keep both sides of the inner skin dry. shoot you could fasten to both sides of the rib to pervent torque on the rib from an unbalanced load, just cut a crotch in every wood piece to straddle the rib. Anyone done it?

[Twigg]

Yep, plenty have done that. Everything is a compromise and I'd choose that method if height was an issue.

RollWithIt bus did it that way, you can Goog;e the videos.