Pre-shrinking Tapes

[paulnuss]

Re: Pre-shrinking Tapes

I have covered and re-covered several airplanes over the years, and never pre-shrank the tapes. I have glued tapes going around an outside curve in the center of the tape only, and then would shrink the edges with the iron to bring them in close to the curve and lay down snugly around the edges, then glue down the rest of the tape. In all the years, I never had any problem with tapes pulling loose or coming un-glued. My fabric cover jobs have held up well, some over 30 years. And they mostly look nice, as good as any you'll see. I think this is not really necessary, in my experience, and possibly a source for troubles.

[Ragwing nut]

Re: Pre-shrinking Tapes

New SuperSeam is PolyTak. It's the same stuff. In a different tin, with a different STC.

What a PIA that would be. You don't even use polytak for tapes with stits

[Buell Powell]

Re: Pre-shrinking Tapes

Mark,
I talked to someone who had a problem with the paint cracking on the tapes on his Hatz--he found that the reason for this on his plane was that the tapes were shrinking(not that the fabric wasn't tight enough where the leading edges meets on the wings etc. which can happen and not enough that the tapes were coming loose or shrinking enough to distort the shape of the width). The way to prevent this was to pre-shrink the tapes. I don't think the Poly Tone would have this problem but some of the other paints seem to and not sure about Aero thane. I am using Aero thane for the fabric on the Fairchild and wondered about this-not looking forward to running an iron over all those tapes and how best to pre-shrink the tapes if I need to-let us know how shrinking the tapes in a oven works out and how much of a width loss there is.
Thanks,
Buell

[N96337]

Re: Pre-shrinking Tapes

Buell, I think the main causes were mentioned a while ago... people not "quite" applying the tapes as is spelled out in the manual (precoating with polybrush and paying attention to having it encapsulate the tape fibers from the bottom up), and the dark colors over them at that time. I've got a chart that shows the temperature effects of different colors.. I'll try to dig that out today.

[N96337]

Re: Pre-shrinking Tapes

OK...it took a while, but I did stumble across this today, so here's the temperature graph that was supplied by DuPont.

[Hank Jarrett]

Re: Pre-shrinking Tapes

That chart caused some controversy when it came out because it didn't specify that it was the colors under the frequencies of light that generated heat. What your eyes see is NOT the colors that are causing all the heat (some, but not all). There are some paints that are basically white under infrared while looking like a color to the eye. Likewise there are some colors that look white to the eye but get VERY HOT in sunlight. It all has to do with what colors are being reflected from the paint. If you reflect all of the VISIBLE colors from the paint, but do NOT reflect any infrared (that you can't see) the surface will LOOK white to you, but be BLACK in infrared! Ever notice how some white car paints are cool to the touch in a hot parking lot, while others will blister your hands? If you add Titanium Dioxide to paint, it REFLECTS Infrared (and is cool). Some pigments will make white paint but not reflect the infrared and those frequencies of light will absorb the energy and get hot.
Bottom line is, put a sample of the paints you want to use on a piece of metal and set them out in the sun. If they get hot, they are NOT reflecting some frequencies of light. Sometimes you get lucky and can find a fairly dark color that DOES reflect infrared and the visible light frequencies absorbed don't heat it beyond what is acceptable. That's why you sometimes see composite planes with darker colors on them now. They have found pigments that look good, but don't get hot.
Hank

Congratulations, you just got a benefit from all the research at NASA to try and keep the James Webb Space Telescope cool!

[N96337]

Re: Pre-shrinking Tapes

Cool! That makes sense to me Hank. I think DuPont included that graph on the Centari line... probably works for those pigments, but what you're saying makes sense to me.