Dark paint

[Flybyjim]

Hello all,

I have not posted anything for a while, another plane project L16A was keeping me away from the Fox but now that plane is finished and flying I'm back on the Fox. The plane is all covered and just about ready to start the painting. A fellow Kitfoxer mentioned that there has been some trouble with (puckering) of fabric on the leading edge of the wings (perhaps over the plastic leading edge) when the paint is a dark color and it gets hot sitting in the sun. I was thinking a very dark cherry red would look good with some light trim colors but with this new information I may need to rethink this. What have others seen with this possibility of the puckering or expanding of the fabric? As always thank you for your input.

[jiott]

I have a very dark navy blue on my leading edges and in 7 years have not had any puckering at all. I live and fly mostly in Oregon & Washington; maybe Arizona would be different.

[efwd]

Interesting. I haven't heard this before as it pertains to Kitfox's. But, I have that issue myself only under the black paint used on my invasion stripes. I have fixed it once as it is Oratex and it seemed to stick down but I guess maybe the adhesion to the plastic has failed. Maybe Im having an entirely different effect. Pucker? I have bubbles.

[JoeRuscito]

I have bubbles under my once smooth leading edge right where the plastic extrusion sits. I have black leading edges. The bubbles appeared after a hot day in the sun. Talked with the factory, they said I should have varnished the extrusion prior to applying polyfiber glues. Oh well.


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[HighWing]

For what it's worth. This was posted years ago and is a repost.

Back in the "Kitfox List" days there was a member flying a Model IV – what else – who was an engineer at the Newport News submarine facility. His primary responsibility there was safety testing on the newly built submarines. Safety was his focus. He once posted some testing he did on his airplane because of something he discovered during one annual. On his annual, he did the strong light in the wing test in a darkened hangar and saw light shining through the fabric adjacent to each of the finish tapes over each rib. He was concerned about two things – the possible fabric degradation because of the loss of the UV protection at the tape edge and the why the shrinkage there. He acquired some testing equipment consisting of a recording temperature measuring device, put it in the wing and put the airplane in the sun during he heat of the day. He found that even with his relatively light-colored paint – mostly white, the temps inside the wing approached the low end of the shrink temperature range. His conclusion was that the typically unshrunk finish tapes were shrinking from the heat generated inside the poorly ventilated wing.

Maybe the bubbles or wrinkles are created by the finish tapes shrinking in the heat?

[Flybyjim]

Hi Joe,

Interesting read from your post::. You said--Talked with the factory, they said I should have varnished the extrusion prior to applying polyfiber glues. Oh well. I looked today in most all sections of the building manual and I could not find any statement from Kitfox to the fact that the leading edge was to be varnished. Can someone tell me where this is in the building manual?

Thanks

[JoeRuscito]

It is not in the build manual. I followed the manual exactly. It’s worth a call to them to discuss.

As far as shrinking tapes goes. I was super concerned about that. I have seen no evidence of shrinking. The bubbles I see are under a finish tape area. If they were shrinking it might help the situation. Instead the bubbles are simply released from the glue. You can push them with your finger slightly. I don’t see them as an issue because they are small less than an inch. But Visually they bug me.


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[jiott]

This is just my thoughts on the reason for these bubbles: When PolyTak glue is applied to the fabric the instructions say that enough must be applied so that you feel a slight wetness on the opposite side of the fabric-this ensures it wets completely thru the fabric. It dries very quickly so this is not always easy to do. If it is not wetted thru properly the glue is just sitting on the surface of the glued side. Then as it dries, the solvents cannot escape thru the fabric and may cause bubbles underneath. This is just my own idea. I remember doing the gluing of the leading edge and it was not easy to keep the large 4" overlap area thoroughly wetted before sticking it down. I had to do only a couple feet at a time. I came to the conclusion that a little too much glue was better than not enough. When I pressed it down into position I used a squeegee (plastic, credit card, etc.) to smooth it out to avoid lumps underneath and to remove excess glue that squeezed thru the fabric. So far, 7 years, no bubbles even though my leading edge is dark navy blue. FWIW

[Flybyjim]

Thank you for all the input on this paint/covering possible issues. I covered this plane with the Superflight system and their E500 glue I believe is a bit more friendly to use compared to polytac. I have covered before with the poly system and it has worked well but once I used superflight I just liked their process better. I use their pre-shrunk tapes so I do not expect to have issues with heat on these. My plane is covered so it is to late to change anything now. I guess I can change the paint layout somewhat to avoid dark on the leading edge or just go for the dark as planned and see if the e500 glue holds to the plastic leading edge.

I believe this site has helped many builders like myself find suggestions and answers when issues do come up. I also think this site has helped Kitfox sell their planes as potential buyers can see the activity and help that is provided here. I do wish that when improvements/changes are made or an issue like this becomes apparent, the folks at Kitfox would share this information with their customers.

[Frontier Fox]

Jim.

I know exactly what you are talking about when you said the Polytac dries fast. I really struggled with putting my first piece of fabric on the wing. It was hard to get it glued on making sure that the glue penetrated the fabric before it dried and that the fabric was not wrinkled and in place. So after a sleepless night I had an epiphany. I applied two smooth thin coats of poly tac and let it completely dry. Then mixed one part poly tac to one part MEK. Hold the fabric exactly where it needs to be and brush on the polytac/MEK mixture. The MEK melts the glue under the fabric and allows it to penetrate the fabric. No lumps of glue to iron out later and the fabric is unwrinkled and smooth. Easy Peasy.

[jiott]

Great idea Joe. That's exactly how they tell you to glue the fabric to the wing ribs, so why not the leading edge.