Roof Stiffener...any thoughts

[dhanna]

So I removed the headliner and I looked at the underside of the roof and it's a single piece of sheet metal with no stiffeners running the width of the car

Has anyone ever tried to make or install some kind of a metal member to stiffen the roof against vibrations (not that it ever needs it)
I imagine this would screw with the installation of the headliner when I go to re-install
IDK why or how I think this would improve anything but it seems like it would at the very best help with cabin noise / NVH and at the very most improve structural integrity of the roof (if this thing rolls I'm pretty sure it's a done deal with those tiny A-pillars) but anything helps no?

 

[aearch]

for cabin noise there a filler that goes there made of cardboard and supports and gives form to the headliner
you could add flat plates but wouldn't help w noise.

 

[HB Chris]

OCCoupe added stiffeners.

 

[Markos]

Wow I had no idea!

 

[dhanna]

OCCoupe added stiffeners.

Any photos of said stiffeners?
Did he give any reasons as to why this is done?

 

[HB Chris]

He will chime in. Roof gives in just waxing the paint so the stiffeners help.

 

[deQuincey]

you can reinforce using PU adhesive to glue some metal bands that cross the roof transversally and that they have the right length to rest in the lateral structure, but i can not see the point
NVH is your friend there,
such a wide surface would obviously give you noise problems as it will be excited by noise and vibration and depening on eigenmodes you will have noise amplification that will disturb you
do not Weld anything there, i would propose just adding some selfsicking mass to avoid vibration, many brands, but dynamat is probably the best known one, just a 1,2 or 1,6 mm bituminous layer, that spreads less tan 40% of the surface would be enough, (do not cover all the surface)
i would prepare three bands aprox size (800x100mm) and will place them separatedly in the roof

 

[OCCoupe]

I'll see if I can find some pictures. After prepping the metal we added three metal bands that followed the contour of the roof from side to side then tack welded them at the ends and seam sealer as an adhesive to prevent any vibration. Then we painted, coated with 2 layers of latex sound material and finally some heat insulation that has foil heat deflection. The result is a solid roof that isn't flimsy, sounds, and feels solid.

 

[dhanna]

YAY!
Thank You!

 

[dhanna]

you can reinforce using PU adhesive to glue some metal bands that cross the roof transversally and that they have the right length to rest in the lateral structure, but i can not see the point
NVH is your friend there,
such a wide surface would obviously give you noise problems as it will be excited by noise and vibration and depening on eigenmodes you will have noise amplification that will disturb you
do not Weld anything there, i would propose just adding some selfsicking mass to avoid vibration, many brands, but dynamat is probably the best known one, just a 1,2 or 1,6 mm bituminous layer, that spreads less tan 40% of the surface would be enough, (do not cover all the surface)
i would prepare three bands aprox size (800x100mm) and will place them separatedly in the roof

Haven't taken the time to calculate the eigenvalues or mode shapes the roof could take / make (We Aerospace engineers tend to overhtink EVERYTHING) by stiffening the area don't I raise the frequency and reduce the amplitude of deflections of that part of the system?
Is the concern then that adding stiffening here could cause a high pitched standing wave to occur that would make the cabin unbearable?

I was thinking onceI got some sort of stiffener in there I would use Lizard skin Sound and Thermal protection to mitigate the effects I think you're describing.

but I suppose until I 'do the math' it's all speculation in my head.

Do I understand what you said correctly?

While were on the subject does anyone know of a good vinyl repair place My headliner is in overall good shape and could use some minor teeny tiny repairs in 3 spots,

 

[aearch]

the oem cardboard w/ a thin layer of foam

although
mine is the 74 which is much stiffer with bracing and the sunrooof

 

[dhanna]

View attachment 21441 the oem cardboard w/ a thin layer of foamView attachment 21440 although
mine is the 74 which is much stiffer with bracing and the sunrooof

Do you have an electric motor on your Sunroof! That's so cool (IDK if that's stock)

 

[dhanna]

I'll see if I can find some pictures. After prepping the metal we added three metal bands that followed the contour of the roof from side to side then tack welded them at the ends and seam sealer as an adhesive to prevent any vibration. Then we painted, coated with 2 layers of latex sound material and finally some heat insulation that has foil heat deflection. The result is a solid roof that isn't flimsy, sounds, and feels solid.

Any dice on pics of your roof stiffener application? I would graeatly appreciate!
I have an idea for a stiffener with a 'top-hat' or channel type construction... I will post a sketch tomorrow

 

[OCCoupe]

I can't seem to find any pictures. Of all the pictures I took of the restoration you'd think I would have taken a few of the roof

 

[Sven]

for cabin noise there a filler that goes there made of cardboard and supports and gives form to the headliner

The cardboard and foam is only on sunroof cars. Non-sunroof cars use the metal hoops to support the headliner.

I'd recommend OCCoupe's method. Keep it simple. Hat channels would be hard to bend to the correct profile and maybe cause deformation of the roof skin if not perfect.

 

[dhanna]

I can't seem to find any pictures. Of all the pictures I took of the restoration you'd think I would have taken a few of the roof

Darn oh well I'll mock something up in cardboard next week and post some pics.