by Chappy » Tue Mar 16, 2010 10:21 pm
I agree with much of what you're saying Shannon. After messing with flying machines most of my life, the idea that you could put a bag of 6 mil plastic over the wings and heat seal the edges and go fly around w/o immediately getting killed or smashed up is preposterous; and yet, there they are. My report was only that, a report, because I was fortunate enough to see the covering, see it fly (and in a 2 place which I would think would be even more likely to exhibit problems because of higher wing and power loading), and attend Mark's hands-on seminar. I felt the Lazair community deserved to be exposed to the material and process as it stands now, or more accurately last summer, as Mark claims to be upgrading the process as he gets more experience with it.
Fresh material is very, very tough and damage does not propagate, even less so than Tedlar I think. Your point about damage to older, UV exposed material has to be a very real concern as I think it's ability to resist major failure will degrade rapidly over time, but again that will be totally dependant on total UV exposure. Remember, this stuff is three times thicker than Mylar, and it's been demonstrated that Mylar this thick has much more resistance to UV (and just dropping the thickness of Mylar down to 1.5 mil caused it to degrade much quicker than standard 2 mil material). Besides, leave a Lazair tied down outside year round here in Virginia, and UV exposure will be the least of your worries!
With the prospect of a viable covering system (not quite there yet for me, but some obviously feel differently) at a very attractive materials cost, I think we will see this develop. As of right now, you can cover a Lazair in boat wrap for what George wants for a roll of his custom made Tedlar tape and still have enough left over to take the family out for dinner! The economics will drive it. If you can source BW locally w/o shipping, we're talking about an incredibly affordable covering materials cost of maybe one-tenth that of Tedlar/tapes or fabric/glue/uv block/paint coverings. And that's assuming the use of capstrips on all coverings.
Capstrips - there's a topic in itself. No Lazairs kits that came supplied with Mylar were ever fitted with cap strips. None were needed as the rubber based tape adhesives never failed unless roasted during film shrinking. Small sections of the double foam rib tape sometimes failed, but that was generally due to damage to the ribs first. Mylar doesn't hold the continuous spring-like tension on the covering that Tedlar does. Many, many Lazairs using Tedlar have operated for decades without the use of capstrips. Capstrips became a suggested REPAIR when Tedlar tapes and foam tapes separated. Several causes were identified. Gross over shrinking of the covering was the main cause (this is not possible with Mylar!), followed by occasional shipments of Tedlar tape that had inferior adhesive. These tapes were custom made for Ultraflight by small companies and they eventually found out that they couldn't rely on the suppliers to produce top quality tape each time. Finally, residue from solvents seemed to adversely affect tape adhesion. Acetone seemed to be the main one, and unfortunately it had been recommended by the factory for prepping before taping. And the acrylic adhesive was a pressure sensitive type that needed to be rubbed down well within the first couple hours of installation to cure properly. This was not fully realized when the switch to Tedlar was made. With all this going on, and Tedlar really the only alternative to Mylar, the quick fix was capstrips. Fabric was really never seriously considered because it didn't jive with Ultraflight's marketing. A Lazair was sold as an easy and fast to build kit. Adding a contemporary fabric covering job basically ruined that claim, not to mention the effect on kit material costs.
I think 2010 will turn out to be a very interesting year for us with the efforts to develop new affordable covering systems and alternative 4 cycle engines. Let's hope it turns out to be a safe year too for everybody!
Chappy