The reference to "steaming" my old BD-5 Hysol joints relates to Aircar's observation about the de-bonding of the HP-18 in the presence of water. My untreated BD-5 aluminum/Hysol joints would probably have de-bonded after only a couple of hours in the presence of steam with no work needed from me. The Hysol softened with heat only but still stuck very well. The Proseal came apart rather easily with heat, and cleaned up completely with MEK and a plastic scraper.Thanks for the inputs above. I wondered about the comment on "steaming" the joints, were you saying that that worked on something later on, or that a heat gun would not work, only steaming? We just received our Fusor acrylic glue package and will be testing the repair aspect of it by trying to separate test sheets. Sam
Yep. I've yet to see this point adequately addressed in this thread. I can think of a half-dozen homebuilt aircraft types (Cri-Cri, several by John Monett, and the entire Schreder "HP" line of homebuilt sailplanes) that use adhesive bonding of aluminum to foams, composites, or to other aluminum parts - all with scuff-and-solvent-wipe (and/or primer) prep. The Cri-Cri's are often flown aerobatically.
With all due respect to the experts here, Moni's, Monarai's, Cri-Cri's, and HP-11, HP-14, HP-16, RS-15, and HP-18's are not falling from the sky with debond failures, and many, many examples have very significant service histories. A blanket dismissal of the technique flies in the face of reason - all evidence points to it being perfectly adequate for these relatively low-stress applications.
If scuff-and-solvent-wipe is "completely inadequate" and will "always" result in bond failure, why are we not seeing structural failures in these aircraft types after multi-decade service histories? If it turns out that you'll "always" see a bond failure but it takes sixty years for the breakdown to happen in these types of applications, how is this discussion any more than academic? There's a disconnect here somewhere, and I'd like to hear more explanation than vague generalities about "they are failing, but maybe just not bad enough yet" before we're encouraged to abandon a technique with good history of service.
I find this interesting, and a reason for concern. Do you have any more insight on just what types of resin and/or conditions to watch for this phenomena? Is the lack of surface cure due to some kind of chemical equilibrium reaction with the atmosphere or some other mechanism? Is the uncured surface a problem with secondary bonding using the same type resin as used for the lamination or does it only manifest if using a different bonding resin?Then, we have also found resins that under certain conditions may not achieve a proper cure, even at high temperature, leaving a somewhat "loose" surface. these are virtually impossible to bond to.