Yes, they continued using LaF through the eighties and I think even after that point. They did try several methods of surface sealing (Core Bond or similar) prior to bonding the core to the glass but according to a recent builder of one of the kits from those days, he is still running into areas where the inner skin has de-bonded from the core. In his case he came up with a fix where he injects a thin epoxy into the area of the de-bond. He has expressed concern about other areas developing the separation as he's working on it but apparently the fix seems to be working for him. Outside of that one case, I have not run into anyone lately who is building a G III or the Super IIS.
That's quite disturbing. I was actually considering buying an already completed and flying Glasair SII-S but I find this potential issue downright scary. It also seems to fly in the face of the conventional wisdom of "if they've logged a few hundred hours, then it ain't gonna fall out of the sky". A little Google searching seems to indicate the Last-a-Foam was prevalent in most of the composite kits of the late 1980s/early 1990s, so I don't know that looking at early Velocities or Lancair 320/360s is going to do me any better.
I really don't want to follow the line of thinking I've seen alot of "old-school" mechanics air about composites. You know this notion of them being made from some mysterious witches' brew, that you never really know what went into them, and that they're difficult/impossible to truly evaluate from a structural standpoint. However, as a shopper looking at 15 - 30 year old composite kitplanes which are now multiple owners away from their original builders, I'm starting to wonder.
I've operated under the assumption that I just need to gain the proper knowledge and skills, and be willing to hire the appropriate experts who have material-specific experience, but I'm not so sure anymore....
Yea, it's a tough issue, especially because there is so little data and what there is, is sparse and sporadic since NTSB investigations rarely dig deep into homebuilt accidents. Furthermore, given the type of construction and the nature of the homebuilt market, even nice flyable airframes may not show any issues until too late. Personally I'd like to see an investigation of totaled or abandoned kits in order to get a better statistical picture of these materials.
Several years ago I was trading e-mails with a guy that worked with some kind of ultrasonic nondestructive testing and claimed that it should be possible to develop an inexpensive method of testing for the typical Rutan type of composite structure. Unfortunately, he died (not aircraft related) before getting any hardware put together and I never followed up on it. Since then it seems that there has been some significant progress on this technology to the point that it may now be something that the home built community might finally find practical and cost effective?
So, if there was an effort to do such non-destructive tests, then is the conventional, "traditionalist" mindset correct in its assumption that there is no thorough, accurate test that can be done on a completed and flying, ambient temperature, hand/wet layup composite kitplane such as the Glasair II and III, Lancair 320 and 360, etc.? Again, I've been assuming that I can hire certain well-known and respected shops known in the composite kit world for a pre-buy and that they can tell me if the plane is built well or not. Part of that was to have them assess the quality of the layups, but if they're only able to look at the surface layups on the interior of the fuselage shell and wing skins and then have to make assumptions about the laminates that lay beneath, I'm not sure how comfortable I am with that.
I'd like to be clear that I'm not asking for judgement to be passed on any make or model of kitplane, here, just for validation or disqualification of my assumptions so I can better assess the risks I'm willing to take - both on my behalf and those of any passengers I may ever take up with me.