Wing Bottom Covering Question

[jrevens]

Thanks, Jim and Ross!
I'll try to post some more pictures of the Oratex job sometime soon... it's going good for me, but it sure goes slow when you only work on something about 1 hour every 2 or 3 weeks! It definitely takes longer for the application than Polyfiber before painting, but it's real nice to look at it when it's done and realize that you've got a finished, airworthy part. I'm very pleased with the way it's looking. The stuff is so tough... it's even hard to poke a needle through it!

[jiott]

The Oratex sounds really great except I still have one major concern about it. That is its protection from UV damage to the underlying fabric. I know they say it has built in protection, but the fact that it is somewhat transluscent makes me wonder how good it is. You can get sunscreen for your skin that is very translucent, but mountain climbers who really want total UV protection use zinc oxide which is not transparent.

I have built and flown RC model planes for years and used mostly Monocote covering. It is supposed to be UV resistant, but after about 5 years or so my heavily used models would begin to get weak enough that you could poke your finger thru the covering. I guess I'm a show-me type that will have to wait around for 5-10 years to see how the Oratex airplanes weather the sunlight.

[jrevens]

I understand your concern, Jim. Just a couple of points I'd like to make. First of all, Oratex has been on aircraft for over 10 years now in Europe. It would be nice if we had some longer local experience, but really long term experience isn't available yet. However, the science of these types of materials is is not exactly black magic... it's not like the old days when Ceconite, for instance, was first used on aircraft. The fact that the coated material is slightly translucent does not mean it is more vulnerable to UV rays. It's like comparing apples to oranges. Speaking of that, we can wear sun glasses that are very translucent and block 100% of the UV. You cannot compare Oratex, in many ways, to Polyfiber, or certainly not to Monocote. The Germans who invented this stuff say it is UV resistant (due to the coating), fuel proof, much stronger than Polyfiber & with a much higher temperature rating (482 deg. F.). I wonder if the Polyfiber system is 100% UV proof? I'm not trying to change your mind or sell you Oratex, but I'm just trying to explain some of the reasons I chose to use it. I guess I'm a little bit of a pioneer... so be it.

Anyway, that being said, I hung a sample of Oratex on the back of my house, with a direct Southern exposure, several months ago. We get a lot of sunshine in Colorado - blue, clear skies over 300 days a year on average. We are over a mile above sea level and the sun's rays are less filtered by atmosphere than they are in most of the rest of the country. Our temperature also varies very widely, from occasionally over 100 deg. to 20 deg. below zero or less. This will be a good test, and even after only a year's time the exposure should be equivalent to many years of average use for a hangared airplane.

To the moderators - perhaps this should be transferred to one of the Oratex-specific threads?

[jiott]

Good points John. Your test piece hanging in the sun is a great idea.