At 07:59 PM 4/10/2006, you wrote: >In fact, >the micro should always still be wet on any lay up where micro is used. > >Mark Jones (N886MJ) ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
I know we beat this horse to death a few years back but I must respectfully disagree with Mark's statement when he uses the word "always". There is a lay up technique called "hard shelling" that I used on most of my glass over foam lay ups. I used this technique on both wings, top and bottom. The advantage was that I could complete the lay up one step at a time and not be rushed. When covering that much area, as a one person operation, it makes a big difference. The process went something like this. I sanded the foam and then vacuumed off the dust. I made up my micro / epoxy mix and applied to the foam, removing as much as possible after spreading. I allowed this to cure creating a "hard shell" on the top surface of the foam. When cured I brushed the surface once or twice with a sanding block to remove any "prickles" that tend to snag the glass when moving the glass on the foam before wetting out. I then did the glass wet lay up and covered that with one layer of "deck cloth" while the lay up was still wet. The deck cloth draws most of the resin needed for wetting from the glass layer below when dry brushed on the top. Add what little epoxy is needed to wet out the deck cloth in the dry areas. The debate between the two processes is usually over which one gives the best bond between the foam and glass. Consider the following and then do a test of your own. The purpose of using "micro slurry" on the foam is to fill the top surface of the foam with something lighter than the pure epoxy used in the lay up. The failure point of the bond will always be at the bottom edge of the penetration level of whatever method you use, be it pure epoxy, micro slurry still wet, or the hard shell method. The bond between the pure epoxy in the glass lay up and the hard shell is many times stronger than the foam it is bonded to. After 206 hours on my KR, I'm convinced the process works. To convince yourself, try the following. Use three pieces of foam and do a glass lay up using pure epoxy, micro slurry still wet, and third, the hard shell method. After the three lay ups are cured, peel the glass off the foam. You will find the same amount of foam on the bottom side of the glass removed from each of the three pieces. You may even find a bit less on the lay up using pure epoxy depending on just how "wet" you did the glass lay up. I think that is the case because you are getting better penetration when you force the micro mixture into the foam when you squeegee it on than when you just add pure epoxy to the glass overlay. As always , your results may vary. Something tells me the net will be smoking for a couple of days. :-) Larry Flesner
