Prevost XLII Skin Delamination Repair

[davidbrady]

(05-04-2017 15:45)cmillsap Wrote:  Could it be that “over” compression of the panel edges to the forms by the jigs created the condition but improved the adhesive’s ability to remain adhered, I’m only guessing? I also don’t know if these same type jigs were used during the original assembly. But if anyone else has seen this condition on an XL2 or XL3, I’d be interested in knowing about it.

Hi Chuck,

I've seen those depressions on XLII's from time to time. The jig does predate the adhesive failures and fixes. If you go back to early versions of the CatBase or early versions of parts documentation you'll find that jig. I've seen it in documentation that came with SpongeBob which tells me it's a factory jig which turned out to be useful for panel repair.

Again, I couldn't agree more about applying the right pressure to the adhesive to ensure a good spread and to allow curing. Not too thick and not too thin. To thick and you risk curing issues and less bonding surface area; too thin and you risk venturing outside the elastic limits of the glue as the panel tugs at the interface.

(05-04-2017 22:57)Hisham Amaral Wrote:  Great job David, I love this program fast results. The results are at room temperature and not 100Deg F, when factoring in the high temperature the adhesive expands and thus failure can be induced.
Please look up the adhesive properties at 100 and 150 deg. F.

Thanks Hish. It was fun working thru this exercise. The attached paper, page 7, shows the results of 200 psi on a metal to metal 1" square joint adhered with MMA (Methyl Methacrylate like Loctite H8000) at 120 deg F, and 140 deg F. Their test was simply hanging a weight from the sample which actually turns out to be the worst case for adhesives. Fatigue loading is more pronounced as the frequency decreases - creep sets in. The results are good at low psi and higher temps as shown on page 7.

BTW, the results of the FEA agree remarkable with theory:
Fiberglass:
Theory: 6686 lb, FEA 6830 lb

Flat Stainless Steel:
Theory: 731 lb, FEA 748 lb

The ribbed stainless panel is too complex for theory; numerical methods are required.