View Full Version : Dacron sails - how old is too old?
09-28-2009, 11:26 AM
How long does dacron fabric last on an ultralight in Canada
I've read that any significant difference in colour between the top and the bottom indicates that it is too old to be safe. I've also read about "poke tests" and Maule instrument tester.
My basic question is how long can they be safe for.
I see a number of chinooks from the mid 80's in the classified section here with original dacron - how long can they be expected to last?
09-28-2009, 08:50 PM
I only know what I've read - and the figure I've often heard quoted for a decent grade of dacron (untreated) is 1,000 hours of UV exposure. Meaning 1,000 hours of exposure to the sun.
If the plane is left outside and uncovered, that 1,000 hours would mean only about 3 - 4 months. Nobody does that of course - and either covers the sails and tail or hangers the plane. With that being the case, then 1,000 hours of UV exposure is equivalent, more or less, to 1,000 hours of flying. Well . . . probably less, since every flight also involves some pre and post flight stuff which would be outside as well.
Only way to know for sure is to do the punch test thing. I would think an owner would do the punch test annually as part of a routine annual inspection - just to be sure.
Did Chinooks come with dacron? I thought they were all dope and fabric? Dope and fabric covering lasts way longer than just dacron. Some dope and fabric planes are 40+ years old and still fine. Again, depends on the quality of the covering job and the amount of exposure, moisture, etc.
09-28-2009, 10:28 PM
I've seen a couple of different "hours of UV exposure" numbers, but I wonder if after a certain point just normal duration might come into play.
I think the WT11 chinooks came with dacron. The Plus 2 might be different.
03-19-2010, 04:16 PM
The Chinook Plus 2 comes with Ceconite. My A/C has brand new coverings. Anyone know the life expectancy of Ceconite?
Polyfiber, Ceconite or any other fabric has to have a coat of silver paint over it to actually block out the suns rays. The paint has aluminium dust in it. Your final finishing [colour ] coat goes over top of that.
If you google up Polyfiber the method used to cover their fabric is in their website. Ceconite is very similar. Without the silver dope, it's called Polyspray in the case of Polyfiber, there is no UV protection at all.
With Polyfiber you start off with Polybrush as the first layer, then a couple of coats of Polyspray and finaly finish up with Polytone the colour coat.
Done correctly aircraft fabric last for decades.
06-09-2011, 10:21 PM
For regular fabric, a fabric tester is used. Standard aircraft standards are 45psi minimum, between 45 and 85 psi. Not sure about dacron sailcoth, guessing it should be the same. Also check with a boat sail maker, I believe it is the same stuff. Another basic test is to give it a good whack with the flat of your hand. Not the best but better than no test.
06-10-2011, 06:24 AM
I have to disagree with that statement as I went through this debate this winter in regards to my dacaron wings, 10lbs is the magic number best tested with a Quicksilver fabric tester. I researched a load of articals and finally found some that were specific to Dacron Sail cloth and 10lbs was the number that kept being refered to on a double surfce wing.
09-29-2011, 03:46 PM
finally have the answer as to how long fabric lasts. My Beaver was outside from mid August until mid November 2010 and from late May until late September 2011. I used the shade of a building this year but that only lasted for part of the morning and my tail was always exposed and that surface is what failed my knuckle punch test. I also made a quick spur of the moment video on it.
09-29-2011, 10:50 PM
Awesome video Eastcoast . . . thanks for taking the time to make and post this very imformative video. I'm sure it will be helpful for a lot of fabric flyers.
I gotta say, It might be hard to go ahead and just punch your fabric with your fist, but as you said, if you're afraid to do that and cause a tear, then perhaps it isn't safe to fly!
10-12-2011, 06:18 AM
This is a follow up video to my other one. In this I demonstrate how I test sail cloth for strength and safety.
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