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Old 11-01-2019, 01:33 PM   #1
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Removing the ceiling panels

I remember sometime back replying to someone on this site saying, ďthe ceiling panels arenít structural!Ē

Now Iím worried about it.

On a Thomas Minotour is that interior ceiling panel providing shear strength? I tried to get photos of the unskinned from from Thomas, but no success.

On Saf-T-Liners I see that there are two longitudinal channels running the length. Is the Minotour the same?
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Old 11-01-2019, 05:35 PM   #2
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Originally Posted by Danjo View Post
I remember sometime back replying to someone on this site saying, ďthe ceiling panels arenít structural!Ē

Now Iím worried about it.

On a Thomas Minotour is that interior ceiling panel providing shear strength? I tried to get photos of the unskinned from from Thomas, but no success.

On Saf-T-Liners I see that there are two longitudinal channels running the length. Is the Minotour the same?
the ceiling panels do lend structural strength to the bus - they are what prevents the ribs from collapsing for and aft in case of an accident - the skin is thin, both inside and out, but like spokes in a bicycle wheel, the stress comes from pulling, not pushing, and the multi gazillion little screws and rivets make sure the skin holds the ribs in place
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Old 11-01-2019, 06:37 PM   #3
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the ceiling panels do lend structural strength to the bus - they are what prevents the ribs from collapsing for and aft in case of an accident - the skin is thin, both inside and out, but like spokes in a bicycle wheel, the stress comes from pulling, not pushing, and the multi gazillion little screws and rivets make sure the skin holds the ribs in place
There are a gazillion screws on the ceiling of a Minotour compared to the exterior which is relatively sparse.

I took a speaker off the ceiling and found the poly wool insulation looking pretty substantial. I know itís not near as good as the rigid stuff, but Iím going to hole saw some holes in it to do the anchors for the PV panels and cover it with that 1/4Ē T&G they sell at Lowes
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Old 11-01-2019, 07:36 PM   #4
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I took a speaker off the ceiling and found the poly wool insulation looking pretty substantial.
I'll say pretty firmly... it doesn't matter. It wouldn't matter if there was magic insulation in the ceiling with an R value over 9000- the metal-to-metal connections throughout the ribs creates a thermal bridge.


I wasn't going to replace the ceiling panels, I thought hey, I'll be fine. Winter comes along, I point my thermal optic at the ceiling. Two inch wide, pitch black (coldest color) lines across the ceiling at every rib. I HATED taking down the ceiling, but no regrets. If you want to be comfortable in really low or really high temps, just do it.


And I honestly don't see why structural integrity is even a concern here. I don't plan on rolling my rig over.
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Old 11-02-2019, 12:32 AM   #5
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I'll say pretty firmly... it doesn't matter. It wouldn't matter if there was magic insulation in the ceiling with an R value over 9000- the metal-to-metal connections throughout the ribs creates a thermal bridge.


I wasn't going to replace the ceiling panels, I thought hey, I'll be fine. Winter comes along, I point my thermal optic at the ceiling. Two inch wide, pitch black (coldest color) lines across the ceiling at every rib. I HATED taking down the ceiling, but no regrets. If you want to be comfortable in really low or really high temps, just do it.


And I honestly don't see why structural integrity is even a concern here. I don't plan on rolling my rig over.
Playing Devils Advocate, why does it matter that the ribs are a thermal bridge, you're never going to get 100% efficiency. I heard so many people say your wasting your time insulating if you don't do this or that. I say some insulation is better than none. and the thermal bridge the rib may make will be minor compared to the value of the insulation that large cavity. Without numbers, it's much ado about nothing.
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Old 11-02-2019, 01:45 PM   #6
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Playing Devils Advocate, why does it matter that the ribs are a thermal bridge, you're never going to get 100% efficiency. I heard so many people say your wasting your time insulating if you don't do this or that. I say some insulation is better than none. and the thermal bridge the rib may make will be minor compared to the value of the insulation that large cavity. Without numbers, it's much ado about nothing.
Yeah this was my guiding principle for insulation. 100% efficiency is impossible, but if I can insulate as much as I can, then itís much better than it was before. I didnít insulate the forward cabinets because I wanted the extra space and figured the air gap was good enough, even though Iím losing like 3% insulation on the bus. But Iím still 80% better than with stock insulation. Same thing with the windowsóthey cover like 25% of the bus and have zero insulating capabilities, so what does it matter if I cover every little nook and cranny with insulation? Itís a little better, sure, but Iím okay leaving a few gaps between boards if it makes installation easier. But thatís just me and my lazy ass.
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Old 12-01-2019, 01:05 AM   #7
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Hey man. I have a 2006 thomas minotour mfsb also. 5 windows around 23ft chevy express 3500 chassis.

Do you know what is above the ceiling panels? I agree they hold the bus together structurally as all the screws are thru the inner skin into ribs, not the roof skin. Unless there are longitudinal members connecting the ribs? (Flexing may cause roof or window leaks is my worry).

I want to insulate inside the roof in the future but may just cover ceiling panels and loose 1/2" headroom aprox.
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Old 12-01-2019, 04:56 AM   #8
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Hey man. I have a 2006 thomas minotour mfsb also. 5 windows around 23ft chevy express 3500 chassis.

Do you know what is above the ceiling panels? I agree they hold the bus together structurally as all the screws are thru the inner skin into ribs, not the roof skin. Unless there are longitudinal members connecting the ribs? (Flexing may cause roof or window leaks is my worry).

I want to insulate inside the roof in the future but may just cover ceiling panels and loose 1/2" headroom aprox.
I've removed the interior panels and driven the bus around for quite some time. WHat will flex? I didn't have any ill effects from it.
You'll fix more leaks removing it than leaving it.
Are your interior panels even steel or are they aluminum?
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Old 12-01-2019, 04:59 AM   #9
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the ceiling panels do lend structural strength to the bus - they are what prevents the ribs from collapsing for and aft in case of an accident - the skin is thin, both inside and out, but like spokes in a bicycle wheel, the stress comes from pulling, not pushing, and the multi gazillion little screws and rivets make sure the skin holds the ribs in place
Huh- so the cardboard in a wanderlodge is structural? BB sure didn't think so.
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Old 12-01-2019, 12:22 PM   #10
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I've removed the interior panels and driven the bus around for quite some time. WHat will flex? I didn't have any ill effects from it.
You'll fix more leaks removing it than leaving it.
Are your interior panels even steel or are they aluminum?
I dont think thomas would install a screw every 1/2" along the rib for no reason.

That being said... I think there is enough support.
Im going to tear the ceiling down one day and add insulation and do a shiplap wood or thin ply to reduce heat transfer. Im watching my heat get sucked out through the ribs and melting the frost on the roof....
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Old 12-01-2019, 12:32 PM   #11
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I dont think thomas would install a screw every 1/2" along the rib for no reason.

That being said... I think there is enough support.
Im going to tear the ceiling down one day and add insulation and do a shiplap wood or thin ply to reduce heat transfer. Im watching my heat get sucked out through the ribs and melting the frost on the roof....
It wasn't for no reason, they want to overbuild the bus for transporting children. Is it necessary, maybe not. In the same bus built for other applications, they use fewer ribs and screws.
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Old 12-01-2019, 12:40 PM   #12
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I dont think thomas would install a screw every 1/2" along the rib for no reason.

That being said... I think there is enough support.
Im going to tear the ceiling down one day and add insulation and do a shiplap wood or thin ply to reduce heat transfer. Im watching my heat get sucked out through the ribs and melting the frost on the roof....
MIne had a rivet every half inch!
It never deformed or "flexed". Never developed any new leaks and still hasn't years later. Its still not skinned inside completely and its been thousands of miles.
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Old 12-01-2019, 12:55 PM   #13
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I dont think thomas would install a screw every 1/2" along the rib for no reason.
On the other hand, if the ceiling were a major structural component, why is it only riveted to every other rib (my ceiling panels had a few rivets on the alternate ribs, but not like on the ribs had two panel edges meeting)? Why are some ceiling panels perforated for acoustics when perforations weaken sheet metal? For that matter, why is the roof only riveted to every other rib? (Note: my bus seems to have a unique feature which is one of the ribs in the middle of a roof panel has rivets run on it - I don't know why, no other bus that I've seen has this.)

None of us actually knows what the situation is here - I think a conversation with an actual school bus designer/engineer would settle these issues. Anybody know one? Personally, I think a bus is engineered around a combination of structural and economic concerns, which makes it difficult to tell exactly what the rationale is behind any particular feature.
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Old 12-01-2019, 01:46 PM   #14
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https://www.google.com/amp/s/www.biz...homas.amp.html

Thanks for replys. I feel better about dropping ceiling panels. Lots of pros, not many cons. Check out this demo in the link.. I wouldnt try that with a rotted rv roof.

A bus engineer is trying to meet to meet the laws I guess. Seems like every bus is a little different.. I was hoping the OP could inform me more on this exact minotour design.
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Old 12-01-2019, 03:25 PM   #15
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Hey man. I have a 2006 thomas minotour mfsb also. 5 windows around 23ft chevy express 3500 chassis.

Do you know what is above the ceiling panels? I agree they hold the bus together structurally as all the screws are thru the inner skin into ribs, not the roof skin. Unless there are longitudinal members connecting the ribs? (Flexing may cause roof or window leaks is my worry).

I want to insulate inside the roof in the future but may just cover ceiling panels and loose 1/2" headroom aprox.
Sorry I didnít see this sooner. The ceiling is filled with Poly fiber sheet much like the stuff in puffy jackets. It is quite full from what I can tell. This is part of my reason for not dropping it. Since it already has some speaker holes that will be deleted, Iím going to cut holes in it as necessary to fish wire for lights and more substantial sound and then Iím going to skin it with 1/4Ē T&G that is sold at Lowes.
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Old 12-01-2019, 03:49 PM   #16
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https://www.google.com/amp/s/www.biz...homas.amp.html

Thanks for replys. I feel better about dropping ceiling panels. Lots of pros, not many cons. Check out this demo in the link.. I wouldnt try that with a rotted rv roof.

A bus engineer is trying to meet to meet the laws I guess. Seems like every bus is a little different.. I was hoping the OP could inform me more on this exact minotour design.
Well that's why I keep bringing up the wanderlodge. The SAME folks that designed the Bluebird All American designed the 'Lodge. THey were going for "the ULTIMATE tank/RV". I'd think they knew what they were doing.
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Old 12-02-2019, 06:52 AM   #17
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Removing panels

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Yeah this was my guiding principle for insulation. 100% efficiency is impossible, but if I can insulate as much as I can, then it’s much better than it was before. I didn’t insulate the forward cabinets because I wanted the extra space and figured the air gap was good enough, even though I’m losing like 3% insulation on the bus. But I’m still 80% better than with stock insulation. Same thing with the windows—they cover like 25% of the bus and have zero insulating capabilities, so what does it matter if I cover every little nook and cranny with insulation? It’s a little better, sure, but I’m okay leaving a few gaps between boards if it makes installation easier. But that’s just me and my lazy ass.
I can attest to the benefits of removing panels. I’m sure the metal panels help the structure a little bit, but it’s a non factor except in a rollover I would imagine. I took the panels out of my Thomas and they were heavy duty and riveted every few inches it seemed. My last bus though a US bus had ceiling panels that had little vent holes and literally only had a handful of screws holding them in. I would just assume any bus with panels removed will still be a much safer vehicle than an RV.

As for insulation, again speaking from my current situation. Spray foam is amazing! I have been working on the bus everyday here in Indiana in the freezing cold. The bus stays warm by simply turning it on using the dash heater to get it warm for about 15 minutes and then turn it off. I have high powered work lights in there after and it Stays warm all day and into the night like that. I will also reiterate how quite the bus is now with the spray foam. It just seemed to have eliminated all the little rattles, squeaks, and wind noise.

My 2 cents
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Old 12-02-2019, 07:28 AM   #18
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Any school bus is only built to meet the many federal/state safety regs for hauling our darling fomites around.

To that end, the engineers design the bus to comply with said regs; it's very rare that a company goes out of its way to exceed such regs...
Sometimes it's cheaper/more cost effective to exceed the regs -- great -- don't think that's from the altruism inherent in a capitalist model...

The manufacturer needs to stay in business -- make a profit -- and this is achieved by building to the requirements as cheaply as possible.

I'm not gonna bother to research the regs in place when my 2002 thomas was built... maybe a bus has to withstand sliding over rocks that will tear the outer skin so an inner skin is required...

Yes, of coursethe inner skin adds strength -- never said it wouldn't -- do YOU need that much strength? I know that I won't -- I'll never have a bunch of passengers in the back of my bus...

And if you're adding Ĺ" T&G which many do -- if properly fastened that will likely be as strong or stronger than the sheet metal you removed.

The acoustic perforations in a sheet of metal make almost no difference to it's overall strength -- you think you can squeeze one of those panels like a sheet of tin foil because of those holes? No, no you can't...

The zillion little holes in the panel are an extra manufacturing step in the process of making that sheet of steel. That means somebody wanted and paid for it. The bus still meets what ever strength regs were in place at the time of build.

Coffee's finished, rants over...
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Old 12-02-2019, 07:38 AM   #19
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The acoustic perforations in a sheet of metal make almost no difference to it's overall strength
This is incorrect - perforations weaken sheet metal: IPA :: Strength of Perforated Metals . It's not really hugely relevant, though, since the designers could easily compensate for the weakness of perforations by using a thicker base material.
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Old 12-02-2019, 07:46 AM   #20
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This is incorrect - perforations weaken sheet metal: IPA :: Strength of Perforated Metals . It's not really hugely relevant, though, since the designers could easily compensate for the weakness of perforations by using a thicker base material.
I wasn't thinking of a panel that perforated...

JK -- excellent reference -- but I did also say -- the bus would still be built to whatever strength was required by reg at the time...
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