# Fabric Testing

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#### sptomh

I recently purchased a light aircraft (maximum gross 550 lbs) the was covered with PolyFiber Light (1.7 oz./sq. Ft.) many years ago. The fabric seems good to me but I’d like to test it. I don't have access to a Maule tester and new ones are over $500. I’ve seen the reasonably priced Quicksilver tester but it is calibrated differently and appears to be intended for testing dacron. I’m wondering it the quicksilver tester would work? Thanks! #### Dan Thomas ##### Well-Known Member I recently purchased a light aircraft (maximum gross 550 lbs) the was covered with PolyFiber Light (1.7 oz./sq. Ft.) many years ago. The fabric seems good to me but I’d like to test it. I don't have access to a Maule tester and new ones are over$500. I’ve seen the reasonably priced Quicksilver tester but it is calibrated differently and appears to be intended for testing dacron. I’m wondering it the quicksilver tester would work? Thanks!
Poly Fiber is polyester. Dacron is polyester.

#### TFF

##### Well-Known Member
What is it painted with? That is going to be the telling story, along with storage.

#### sptomh

##### Member
Ok. I thought the shiny ”sailcloth” that Quicksilvers are covered with was something else. Sounds like I can just use the quicksilver tester with their recommended limits. Airplane was covered many years ago but it has been inside it whole life. Thanks.

#### jedi

##### Well-Known Member
Look for an A&P with a fabric tester and borrow it. Lacking, that do a finger or pencil test. Knowing where to test is important.

#### Dan Thomas

##### Well-Known Member
Ok. I thought the shiny ”sailcloth” that Quicksilvers are covered with was something else. Sounds like I can just use the quicksilver tester with their recommended limits. Airplane was covered many years ago but it has been inside it whole life. Thanks.
The Quicksiver tester, if it's intended for ulatralights, might be calibrated for much lighter fabric and won't give an accurate idea of the stuff on your airplane.

#### sptomh

##### Member
Been looking for someone with a Maule tester but no luck. If the quicksilver tester isn‘t appropriate I’m wondering if I can come up with something on my own. I took a pencil eraser and measured the area. Calculated the force to equal the minimum required tensile strength from 43.13 (about 13 pounds which is equal to 46psi). Put a pretty good dent in the fabric but no holes. Does this sound ok or am I totally off base here? Thanks again.

##### Well-Known Member
Try a Bettsometer.

#### Victor Bravo

##### Well-Known Member
If you can stick your finger through the fabric and tear it, on the top surface of the wings or tail, then the fabric is bad.

If there is a layer of silver or gray primer on the fabric, underneath any paint or final color, chances are you are OK.

Roll the airplane out into moderate sunlight (not scorching fireball light). If you can look from the inside of the structure up through the fabric, and see areas of sunlight or bright light shining through, then your fabric was not protected properly (with the silver or grey primer).

#### sptomh

##### Member
Thanks everyone. That helps a lot.

#### BBerson

##### Light Plane Philosopher
AC 43.13 states fabric should be 70% of original minimum. Figure 3.1 gives methods. Could take a 1" sample and do a tension test and compare with new fabric.

#### TFF

##### Well-Known Member
I know it’s a UL but to the FAA, the only test is to cut a chunk of fabric out and pull on it till it breaks. I guess the Maule tester was invented for Maule airplanes. A factory tool to only be used on your brand of airplane is legal. Now airplane fabric being airplane fabric, you can infer the same information but the FAA does not count it.

When it comes down to it, properly painted Dacron is going to be ok. No mater how properly cotton was prepared it will rot in time. No one but historic restorations are using cotton.

Put a flashlight inside and see how much light you can see from the outside. It’s how you are supposed to gauge when painting the silver if you have enough. Being a UL and weight being a issue, it probably will let a little light through, but how much true direct sun has this thing had? If it’s been in a shed, that is pretty much none. If it’s been outside in the open next to a tractor for ten years, it’s suspect. Without the sun Dacron does not rot.

If the fabric is bad, the Maule tester will go right through too. And if you want to know, an old trick is to put a bunch of paint on suspect fabric and it will pass a Maule tester.

#### cloudopr

##### Member
I recently purchased a light aircraft (maximum gross 550 lbs) the was covered with PolyFiber Light (1.7 oz./sq. Ft.) many years ago. The fabric seems good to me but I’d like to test it. I don't have access to a Maule tester and new ones are over \$500. I’ve seen the reasonably priced Quicksilver tester but it is calibrated differently and appears to be intended for testing dacron. I’m wondering it the quicksilver tester would work? Thanks!
Yes you should be able to use the quicksilver tester. I always use my finger on a part of the airplane that would be exposed to the sun. Just punch pretty hard on fabric if it’s bad your finger will go right out the other side. As long as it’s strong you should be fine.