Prevost XLII Skin Delamination Repair

[davidbrady]

(05-01-2017 15:07)cmillsap Wrote:  David,

It may be fixed but only time will tell.

I find it hard to argue that glue is a better fastener than rivets. But I do understand why Prevost does it. There are several reasons but mainly because it is more economical and it improves the bus’s appearance.

Hi Chuck,

Mostly because rivets aren't very good, especially blind rivets. They're terrible in tension and in shear they're only as strong as the thinnest material being joined. Prevost uses a 3/16" blind rivet which has an allowable shear strength of a few hundred pounds but the loads are always a combination of shear and tension so the strength is actually something less. I haven't measured a Prevost lately but I'm guessing there's a rivet every 3" or so. This gives a linear strength of 100lbs/in. A properly adhered panel using urethane, epoxy, or MMA can achieve better than 2000 psi, so if the bead is one inch wide that's 2000 pounds per inch. This leaves lots of safety factor for heat aging, shrinkage, and variations in application. Plus, glues allow expansion of the panel. How many of us have listened to rivets popping and movement as the sun shines over the coach. Each time this happens there's fretting of the rivet hole. Rivets require holes that are imperfectly filled by the rivet and which allow water in. They make prepping and painting difficult, they allow little expansion of the panel, they create point loads and stress raisers, and they don't dampen movement as well as adhesives. There's also a list of disadvantages to adhesives, but it's the future.

(05-01-2017 15:07)cmillsap Wrote:  It would be prudent to add a panel inspection to any P.D.I when purchasing any coach with glued panels including an H3 as there have been a few loose panels found on them as you well know.

I did have Donny Myers of DMRV remove a leaking panel and re-bond it. It was the upper panel between the slides, originally put on by Vantare, and leaking since the bus was new. I have documentation from the first owner, dated months after taking delivery, complaining about clothing getting wet in basement bay 4 on the driver's side. He took it back to Vantare and they tried to squeeze in additional adhesive but they never permanently fixed it. Donny said, "Vantare barely had any adhesive at the top of the panel". It wasn't a hard fix. If you have a leak, remove the panel and reattach it! No big deal. BTW, Donny's shop is the only shop in town for Vantare owners!

Here's an interesting paper by Loctite on bonding various metals.