Pre-shrinking Tapes

[Mark Julicher]

I put a roll of 2" polyfiber tape in the oven at 225 degrees for about 1 1/2 hours.

It tastes terrible,

but it appears to have pre-shrunk rather evenly as compared to direct ironing and the pinking did not get frayed. Anyone else tried this technique?

[Ray36048]

Re: Pre-shrinking Tapes

Why do you want to do that? I don't remember that in the Poly Fiber STC installation manual.

[Mark Julicher]

Re: Pre-shrinking Tapes

Polyfiber manual Revision 18 Page 50 describes why and how.

Tapes will shrink in the hot sun - especially when they are painted dark colors. Tapes can detach themselves and cause all manner of heartburn.

The process manual recommends holding the tapes in tension and then heating to 250 degrees. I was merely trying a different technique to see if it would work.

[barnstmr]

Re: Pre-shrinking Tapes

Mark,
I think you might want to go a little hotter than 225 if you want to shrink them good. The "Ceconite manual 101" says not to set your iron greater than 225 when ironing tape edges, elsewise they will shrink and result in an ugly job. It says "any temp above 250 will shrink the fabric tape." The context is discussion of a technique to get pinked edges to lay down good, saying that ironing will also help soften the dope and smooth out the high spots from brush marks. Obviously the 101 manual does not put any emphasis on pre shrinking tapes... but perhaps they had never had an experience with them shrinking in the sun.

[Pearson]

Re: Pre-shrinking Tapes

Mark, what a great idea! I would like to hear more about how the tapes go on and whether you need to shrink them anymore after glueing them down. I thought tapes were supposed to be shrunk to close to the same temperature as the rest of the fabric. Let us know how it turns out.

[Ragwing nut]

Re: Pre-shrinking Tapes

Never tried that. sounds like a good idea. i do think as well they need to be fully shrunk at final temp

[Mark Julicher]

Re: Pre-shrinking Tapes

Great advice from everybody! Here is the next iteration of the experiment.

I put the roll of tape in the oven at 250 degrees for two hours. I wanted to be sure it was fully heat soaked. The tape shrank in width by about 3/32 to 1/8 inch. The outer two wraps were slightly puckered, but internally everything was almost perfectly smooth. 250 is final shrink temp for Ceconite and Randolph, but 350 is final shrink for Polyfiber. I think 250 shrink is going to be fine. I don't think the wing will ever hit 350 degrees even in Texas sunshine. Maybe I'll put a candy thermometer on my wing and have a look at the temperature next August.

Richard, Unless I have a wrinkle or bubble to smooth out, I don't shrink the tapes after they are doped down. If you touch a 350 iron to a tape it will get a pinched look like a coke bottle. Little pinked edges that stick up can be laid down with a 225 iron - or maybe 250 and use the edge of the iron for stubborn spots.

Pics of the oven shrunk tape:

[Pearson]

Re: Pre-shrinking Tapes

Mark,

Maybe if you wrapped a few layers of paper around the outside of the roll before you baked it the outer layers of tape wouldn't curl up.

[NY86]

Re: Pre-shrinking Tapes

Isn't it also going to try to shrink lengthwise? Problem is, it can't shrink lengthwise when rolled...

[Hank Jarrett]

Re: Pre-shrinking Tapes

Or even a couple of wraps of scrap Ceconite.
Hank

[Mark Julicher]

Re: Pre-shrinking Tapes

I might try wrapping a roll to see if it keeps from puckering the first six inches. The covering manual calls for holding a long length of tape taut and running a 250 degree iron down its length. I think you would lose a few inches at each end that way. The reason to hold it taut is to prevent puckering.

Good question Ray. Yes, it prevents tautening lengthwise, but so does the procedure in the covering manual. I know if a tape gets hot in the sun it shrinks in width but not necessarily in length - probably because the length is, relatively speaking, better secured to the underlying fabric. Does that make any sense? I know it is what I have experienced on three different airplanes when using dark dope on tapes.

[NY86]

Re: Pre-shrinking Tapes

Good question Ray. ...Does that make any sense?

Yes, it does. I am by no means a fabric expert.

And, you can call me Ray but you doesn't even have to call me Mr. John son...

[N96337]

Re: Pre-shrinking Tapes

I'm glad that with Stewarts you don't have to worry about that stuff!

[Pearson]

Re: Pre-shrinking Tapes

Do you not have to shrink the fabric with Stewarts? How does it work? Sounds very interesting!

[N96337]

Re: Pre-shrinking Tapes

Sure you shrink the fabric... it's polyester like the rest. The glue is so strong that you don't need to worry about tapes shrinking. Go over there and check it out...it's a great system! www.stewartsystems.aero