Covering... stabilizing the iron temp?

[mhorowit]

I'm heat shrinking fabric. The iron I"m using fluctuates as I use it. Easily a drop in 20* over just a few minutes use. How do you work around that variation? - Mike

[paulnuss]

Re: Covering... stabilizing the iron temp?

I have never had an iron that keeps a perfect temperature. The shrinkage you get on Dacron (Ceconite, PolyFiber etc.) is a function of temperature plus time. Movement of the iron at a rate that is giving you the right amount of shrinkage is the key. How much is enough shrinkage? How much is too much? That takes a bit of practice and developing a feel. Make up a couple practice panels of 2x4's or something similar, and shrink up a couple pieces of Dacron. It doesn't seem to be as temperature critical as the manuals would lead you to believe, beyond not hot enough to shrink, and way too hot that melts or damages the dacron. The important thing then is not so much shrinkage you'll deform frameworks, yet enough to be as taught as you would like. I have always used non-tautening dope products, so the shrinkage is done primarily on the fabric with the iron, Yet even the non-tautening products will shrink a bit over time, so allow just a wee bit of tolerance for that. Not quite taut fabric, doped with tautening dopes, will have the dope film carrying the tension, and after some time will start to crack the film. I have never used the Polyfiber products, but i believe they are non-tautening.

[N96337]

Re: Covering... stabilizing the iron temp?

Proper shrinking of the fabric is critical, if you want the job to hold up in tempurature variances. Go through the steps of temperatures and follow the instructions carefully. The way to make sure that you get the proper final shrinkage, is to keep that temp setting on the iron and go over your surface multiple times. There is no "feel" that is as accurate as the temperature is. As is said above, irons don't hold temps that well, but with multiple passes, you can assure that you'll have the right tension in the end. The main thing is not to go over the maximum temp, as it will give up some tension without warning, thus ruining the job.
John

[astjp2]

Re: Covering... stabilizing the iron temp?

The iron I use is probably 30-40 years old and made of IRON, not aluminum. Helps hold the heat better. Got it at a thrift store. DO not use an iron with the temp over 350, and think its going to cool, it will losen the fabric and cause it to sag when it gets cold outside. One of our local "experts" did this and his own wings sag an inch when it gets below 40*. He is now lying about it and saying that the stitts put out a bad batch of fabric. Never saw a service bulletin or AD on that, and if bad fabric went out there would be, so I called BS on him. Tim

[flyguy]

Re: Covering... stabilizing the iron temp?

How about; start preferred temperature plus 10 and then it should drop to preferred temperature minus 10. I can't imagine that would have a catastrophic effect on your work. Doing the horizontal stabilizer first was a good move.

I've never had any bad results with ceconite and never even checked the temperature. I just adjusted the iron until it worked, starting low of course. Be careful and practice some. You will get the feel right away. Use what works for conditions, hot day, cool day, sunlight, breeze.

I found that Fabric work, while not easy, is one of the most rewarding parts of working on old airplanes.
Darryl

[mhorowit]

Re: Covering... stabilizing the iron temp?

Well, the first piece certainly is tedious! - Mike

[Ray36048]

Re: Covering... stabilizing the iron temp?

Ceconite and Poly Fiber are 2 different processes that use the "same" fabric type. The major difference is ceconite uses dope and Poly Fiber does not. Dope shrinks, and shrinks a lot. The fabric tension with the ceconite process comes from the dope.

Poly Fiber liquids do not shrink. The fabric tension comes from the heat shrink of the fabric. Critical temperature is 350* for poly fiber to get the correct shrink per the STC. Too hot and the fabric will lose tension, forever. Low tension will cause noticable sag in the fabric with temperature changes. It is also critical with Poly Fiber to not have too much slack before heat shrink. All of this is explained very well in the Poly Fiber manual.

A few years ago I saw a write up on irons. He claimed the ROWENTA DZ1500 is the best iron for temperature control. This iron is rated at 1600 watts. Low wattage irons will lose their heat very quickly when applied to the fabric.

[Guest]

Re: Covering... stabilizing the iron temp?

Mike, have you condsidered using a heat gun?

Dave

[Ray36048]

Re: Covering... stabilizing the iron temp?

Hey guys, read and do what the manual says for whatever process you are doing.

I know for a fact Poly Fiber tells you to NEVER use a heat gun. The temperature control when shrinking the fabric is critical. The 350* is nearing the point where the tension will be released. They is no way to maintane the temperature control with a heat gun. Buy the book and do what the book tells you to do, it cost less than $20.

[Guest]

Re: Covering... stabilizing the iron temp?

Ahh

I see.

Is Mike using Poly Fiber?

I have never used Poly Fiber but I have used a heat gun with other ceconite processes (or maybe I should say a 13 years ago).

Dave

[Guest]

Re: Covering... stabilizing the iron temp?

So here is a thought.

If one really wanted to use a heat gun one could attach thin metal rod to the gun parallel to the airstream and attach a small thermocouple to the end of the rod, tape a multimeter to the gun to read the thermocouple and extend the rod the correct amount so that the thermouple indicated the desired temperature after running the gun long enough such the the temp stopped rising.

Then use the gun with the rod and stuff on it and your fabric temp will be less than the termocouple temp and you will not be able to get the gun closer because the rod will stop you.

Dave

[flybikefarm]

Re: Covering... stabilizing the iron temp?

Just get a good iron, calibrate it then go over the cloth two or three times. When I went to Ron Alexanders school that is what we were taught. If you need to use an extention cord, calibrate the iron useing the same cord, and try to keep the cord as short as posssible. I have never had the fabric loose tension useing this method.

[astjp2]

Re: Covering... stabilizing the iron temp?

The fabric is the same except for the lubricants that are used when making it. You cannot mix processes, Ceconite uses Non-tautening nitrate dope, when the fabric is shrunk with ceconite it continues to shrink a little so most only shrink to 325 with it. Because the nitrate is flammable, they use byuterate for the rest of the coats to reduce the flammability. Ever Seen WILE E Coyote go poof? That used to happen with just straight nitrate. The polyfiber is a polyeurothane that encapsulates the fabric similar to ceconite. The only bond with the fabric is by encapuslation, it does not combine with the fabric! I have never messed with the Stewarts process but it cant be much different process wise. I taught Dope and fabric for a few weeks at King Career Center for Anchorage school District. Best program for aspiring mechanics in the country. Tim

Ceconite and Poly Fiber are 2 different processes that use the "same" fabric type. The major difference is ceconite uses dope and Poly Fiber does not. Dope shrinks, and shrinks a lot. The fabric tension with the ceconite process comes from the dope.

Poly Fiber liquids do not shrink. The fabric tension comes from the heat shrink of the fabric. Critical temperature is 350* for poly fiber to get the correct shrink per the STC. Too hot and the fabric will lose tension, forever. Low tension will cause noticable sag in the fabric with temperature changes. It is also critical with Poly Fiber to not have too much slack before heat shrink. All of this is explained very well in the Poly Fiber manual.

A few years ago I saw a write up on irons. He claimed the ROWENTA DZ1500 is the best iron for temperature control. This iron is rated at 1600 watts. Low wattage irons will lose their heat very quickly when applied to the fabric.

[mhorowit]

Re: Covering... stabilizing the iron temp?

Dave - I'm using Stewart.. They are adamantly against using a gun because of the chances of going above 350* - mike

[Garry Crookham]

Re: Covering... stabilizing the iron temp?

This discussion has now referenced three separate covering systems: Stewarts, Poly Fiber, and Ceconite.

Each system has been approved via STC for use on certificated aircraft per FAA approved model lists (AML).

Each system has an approved procedures manual.

The Poly Fiber Procedures Manual 1 states on page 1 that the Poly Fiber STC SA1008WE allows you to replace the original covering on your aircraft with the Poly Fiber system. “It does not license you to get creative and depart from this manual in any way.”
It also states on page 9 “The only authorized heat source for accurate control of the temperature transferred to fabric is a CALIBRATED CLOTHING IRON. Period. Heat Guns? No! “

The Ceconite Procedure Manual 101 also says that it’s STC, SA4503NM, and corresponding AML provides the approved data to cover a certificated aircraft using the Ceconite covering system. Pages 1 through 3 of the manual discuss using the manual and AC 43.13 for covering procedures. Once again, no variations are allowed and on page 12 the question “Can’t I use my heat gun for tautening the fabric?” is answered with NO!

The Stewarts System Procedures Manual 21, STC SA01734SE states in Section 4, page 2: The use of heat guns to tauten fabric is prohibited by this STC.”

Each procedures manual has a section on calibrating and using the iron for tautening the fabric.


My question, as an A&P/IA, is for those of you covering your Taylorcraft, or any certificated aircraft: Where is your A&P/IA in this process? The person that is going to approve the work performed, and your airplane for return to service, needs to be intimately involved from day 1. The internet is a great tool with lots of information. Unfortunately a lot of that information is bad.

Garry