Brian, Tom Gleaser built a KR2 in the 80's and had the same problem, I think it's fairly common. Maybe you know this, but here it is. I worked for 5 years in a R&D lab and in that time we tested Urethane foam for structural and thermal properties. We found that with urethane [ and all two component chemicals] : if the foam [epoxy or what have you] did not fully react [ due to varying amb. temperatures , mostly] the foam would finish it's reaction later. The additional reaction produces off gases which will form a bubble under the fiberglass. Post curing after the foam is finished [sanded], is a good idea. Problem is, you don't know until you bird is parked in the summer sun for a while.
KRron ----- Original Message ----- From: "Brian Kraut" <brian.kr...@engalt.com> To: "KRnet" <kr...@mylist.net> Sent: Tuesday, April 27, 2004 8:46 PM Subject: RE: KR> delaminations! > You are correct that it is usually not a big problem if the glass separates > from the foam in some places. Most KRs I have seen have seperation in some > places. My only concern was cosmetic. My last KR had a big bubble near the > trailing edge. It looked O.K. on cold days, but the glass expanded when it > was hot and bubbled. > > Brian Kraut > Engineering Alternatives, Inc. > www.engalt.com > > -----Original Message----- > From: krnet-boun...@mylist.net [mailto:krnet-boun...@mylist.net]On > Behalf Of larry flesner > Sent: Tuesday, April 27, 2004 9:07 AM > To: KRnet > Subject: RE: KR> delaminations! > > > >I have thought of taking something like a thin steel ruler and putting 1/4" > >deep grooves in the foam in a 6" X 6" grid pattern before putting on the > >micro. That would prevent the glass from separating from the foam and also > >give it a little more stiffness while adding very little weight. Has > anyone > >ever tried this? Maybe I will do some test pieces. > >Brian Kraut > +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > The foam will just fail with a "grid" pattern attached. I really don't see > the need for anything more than sealing the foam with whatever method > you chose and glassing it. How many KRs have flown before us using > that method and how many have fallen from the sky because of the > epoxy/fiber delaminating from the foam? > > It's a beautiful morning out and I need to run by the hangar. I think I'll > take my ol' "hard-shelled" bird up for a quick flight! :-) > > Larry Flesner > > > > _______________________________________ > to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net > please see other KRnet info at http://www.krnet.org/info.html > > > > _______________________________________ > to UNsubscribe from KRnet, send a message to krnet-le...@mylist.net > please see other KRnet info at http://www.krnet.org/info.html > >