UV Question - Rot from the inside ???

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:


New Member
Nov 4, 2007
Hello... I'm planning on covering with a poly-fiber system and have been totally sold on the need to provide UV protection (they recommend 3 costs doubled up - actually 6 layers total of aluminized coating). Without UV protection poly rots quick - no question !!!

... Anyhow... my design has a fairly open cockpit arrangement with a "skylight". What happens with the inside of the fabric. Do I need to aluminize also. Wasn't planning on the extra weight.



Mar 2, 2003
Western Washington
Yes, there could be a source of UV degradation if the light is not filtered in some way. If the cockpit is enclosed and has a canopy or some other type of opening that lets in direct sunlight, your first goal might be finding a material for the skylight that has built-in UV blocking abilities. Failing that, yes, it might be a good idea to provide some basic protection to the inside of the airframe also.


Well-Known Member
Sep 20, 2003
Corona CA
UV treatment for plastic can be a simple dipping process. You could immerse the panels in a shallow tray of the stuff (it has to be heated) and leave it for a few minutes. That's all it takes and there is usually only the slightest discoloration, mostly it comes out as clear as it went in. Try optical suppplies companies, such as BPI for UV solutions. If you have a large, curved windshield, I'm not sure how you would get a vat big enough to immerse it in, but flat panels would be feasible. The ploycarbonate of most windshields is the same stuff as your lenses in your glasses.

Working in an optical lab, I always thought how cool it would be to have a bubble canopy fully coated with the latest anti-reflection coatings. (Which includes a total UV block). Unfortunately, despite the fact that you could just about squeeze the canopy into the coating chamber, the stuff is somewhat delicate and you would have to treat it extremely carefully. You would cover it with a soft cover when not in use and if you do that you already take care of 95% of the UV problem.

But of one did a lot of night flying the difference in visibility would be astounding. And it looks cool!
I wear glasses (or contacts) and the difference between uncoated lenses and those with the latest high-tech coatings is is amazing, especially at night.


Well-Known Member
Mar 31, 2004
southwest TN.
Using the Polyfiber system:

I have noticed on my plane that is covered with Pollyfiber that I sanded a bit too much on the tops of the rib stitching. Looking through an inspection hole toward a bright light, I can see a little light at the bumps where the stitching is.

I haven't added a finish color so before I do the finish paint, I am going to go over everything with another coat of silver!

So be very carefull about wet sanding the silver coats. Stay off the stitching. Or be sure to put a good unsanded coat on last.

After thinking a little about this, I remember a friend had to have his Starduster wings recovered because the stitching was coming loose. He thought mice had eaten the string, but it might have been UV damage through too much sanding when it was covered. He hadn't built the plane.
Best Wishes,


Well-Known Member
Dec 1, 2007
bainbridge ga
one simple thought for inside the cockpit is just cover the inside with something like vinyl like most citabras they just use vinyl baisicaly streached where sunlight can get in and rot it and it dresses the inside up nicely or poly spray the fudge out of it and call it close enough either will work and the ''added weight '' of a little poly spray isnt enough to worry about if your just puting a coat inside the lighted sections of cockpit unless your building a par103 and your at 253.75 lbs lol it wont add enough to worry about