PorscheFanatic202

1 month and holding

PorscheFanatic202

3 months and holding

Alan 91 C2

I have worked this issue, resealing the rear glass, since my 1977 1/2 924. Now have two 944s that need a solution. Still have the 924, yard art??

is there any rethink option? Given that we know the existing system will fail, can we redesign to mechanically make the frame structurally capable to handle the twist moments, in conjunction with isolation from body deflection and eliminate bonding shear forces, and allow the adhesive to be the water seal?

On one end, we have a light weight frame, called flimsy. I like the idea of additional tabs welded in. So, additional structural tabs spaced around the frame. Even though the glass is the structural component of the window. So how do we keep the glass/frame torsion manageable. Tabs can yield more structure. But we must achieve more structure to the window/frame, and allow the frame to "float" in position.

Do we need a couple of ribs from the hinge tab to the latch points? Could be small structure 1/2", or so, just inside the glass, bonded to the glass. Would we add a cross brace to the gas shock mount (bent to install just inside the glass)? With a good window tint, the braces would not be visible.

Seems like all our attempts to bond the frame fail, as the window is more rigid than the frame. Perhaps a frame rethink, with careful torsional stability, will help stop the two systems from fighting the body twist.

Unless we accept the frame and window have separate twist moments, and are joined by a viscous seal, who's function is to keep the water out.

The other end of the spectrum is to decouple the frame, and window, from body twist. Much like bridge structural design, where on end is constrained and the other floats. This could occur with elastomeric mounts rework for the hinges, allowing some lateral movement, and let the latch pin anchor the movement (the latch pins do have some elastomeric allowable movement, need more). The body twist would still need to be addressed. Perhaps a rework of the latch pin to a more floating retention for the latch pin. The key is we can predict/measure body twist, and allow for these forces to occur without forcing the rear window restraining system to fail. So from a hardness perspective, the hinge mount would yield/deflect before the latch point, in longitudinal stress, and the latch/hinge would yield to twist. But both would be designed to yield, and not transfer the twist moment/body bend moment, to the window/frame bond.

Thoughts? And I have two rear windows that need to be sealed.

sparkydog

What if there was a replacement frame made from carbon fiber. Still light, much stiffer, probably impossible to fabricate on an affordable basis...

And one additional thought - what if the gas struts were to be replaced with electric versions (like what are used in modern hatches to raise/lower electronically)? This would eliminate the constant force from the gas struts being applied to the weak frame. The only time there would be force on the strut tabs was when the hatch was being opened.

PS: Thanks for letting me make my first post on the forum

AkechiMotors

I like the idea of electro-pneumatic struts - it would be really cool to install those and wire them up the hatch button, so that when you pressed it, it both unlocked the hatch and raised it.

Alan 91 C2

Thinking to weld perimeter aluminum 1/8" thick, 3/4~1" wide top and bottom, 3/8~1/2" wide on sides, for a full perimeter reinforcement. Incorporate selective 1/8" round shim tabs, black poly, to center frame and glass with no tension. Shim tabs to be the clamp locations for the curing process.
Spray the frame with 2 part SPI urethane sealer. The Sika bond agent to bond with the sealer, when done within a day or two of painting. Will have to verify compatibility.
Would like to renew the flex material in the hold down pins, for the locks. Any thoughts on material choice here.
The above approaches the window/frame de-lamination, from two directions; improve window frame bond, and reduce body twist transmission by rebuilding the lock flex point.

PorscheFanatic202

Hatch separated today. Left side, top of frame. Adhesion on the glass failed. Pulled the 3m single step primer off the glass. I knew the risks. Sika next summer or find a shop to do it.

Most frustrating thing about it is how hard the stuff is to separate from the glass in the other places, but ironic since it won't hold in the places we want it to.

Dan Shea

My hatch is failing... Who's done it, had it last, and knows what products they used?

Anyone try the SikaTack Mach 30 super kit? has the 220 adhesive (higher tensile strength than the P2G product) Aktivator, and Primer in a kit. Seems these are sold by the case, anyone know a shop that would sell individual?

AkechiMotors

That would be so trick, and shouldn't be all that hard to do.

Gregs04.5

I cannot imagine the look on your face, when the one day the hatch latch fails to open, and the power lift breaks your hatch in half. And the extra weight, why?

kens_74911s

Spence, is on the right track, mask and bead blast the perimeter of the glass
K.

AkechiMotors

Is that a common occurrence on the millions and millions and millions of cars that currently use them? I'd imagine there's a sensor that keeps them from actuating when it senses resistance, just like they won't close if there's something blocking them. As for added weight, how much are we talking? 1lb? Maybe 2lb? Regardless, the look on my face wouldn't be any different than the one when I realized my hatch had delaminated due to the constant pressure of gas struts.

tempest411

I agree that electric linear actuators are probably a good solution to this problem. Yes, it is a bit of extra weight, but if anyone cared that much about the weight they'd probably have a track-bound car, with a plexiglass hatch window anyway.

kens_74911s

Old School engineering term K.I.S.S. Keep It Simple Stupid. Why add complexity to this old bird.

tempest411

I agree with you as well. But in this case it could well be warranted. These cars have a long history of problems wiith the hatch glass delaminating, and a servo-type support that does not keep the glass-frame interface constantly under stress when closed would be welcome.