No punch test required????

[Jr.CubBuilder]

I'm a little hesitant to ask this but I'm going to look at a SuperCub that was covered with ceconite in 1981. When I asked about the fabric passing a punch test the present owner says that ceconite is a "lifetime" fabric and doesn't get punch tested..................I was wondering if I would hear Nanooks favorite line about it being ready for camping and fishing. Ceconite does have to be punch tested doesn't it? I'm thinking that plane will need a recover in the near future, and yes I will certainly have a good mechanic looking the plane over before I even seriously think about buying anything. However, I just thought I'd ask. He also has been using it for glider towing, so I'm thinking that mid-time 320 might be nearing the end of its life as well.

[Steve Pierce]

The FAA doesn't recognize the punch test. They reference a pull test in the 43.13. In my experience Ceconite is a lifetime fabric if you keep the finish on it. It doesn't deteriorate unless the UV gets to it. The problems I see after 20 years on a cover job is the plastisisers in the finish starts to evaporate and the finish starts to crack and if it is nitrate/butyrate it comes off. Look it over real good and figure on recovering in the next 5 or so years.

[FlipFlop]

I'm a little hesitant to ask this but I'm going to look at a SuperCub that was covered with ceconite in 1981. When I asked about the fabric passing a punch test the present owner says that ceconite is a "lifetime" fabric and doesn't get punch tested..................I was wondering if I would hear Nanooks favorite line about it being ready for camping and fishing. Ceconite does have to be punch tested doesn't it? I'm thinking that plane will need a recover in the near future, and yes I will certainly have a good mechanic looking the plane over before I even seriously think about buying anything. However, I just thought I'd ask. He also has been using it for glider towing, so I'm thinking that mid-time 320 might be nearing the end of its life as well.

I'm a little hesitant to answer this, but go to: http://www.faa.gov/avr/afs/300/pdf/1l-ch2_3.pdf for your information... The way I read it, polyester fabric is required to conform to TSO-C14b and TSO-C14b fabric is required to be tested... Interesting that para. 2-34, Fabric Testing, states that the FAA doesn't approve of "punch testers", but accepts them... The only "approved" fabric test is the "pull test"...

[cubdrvr]

What the heck is a pull test?

[FlipFlop]

What the heck is a pull test?

2-34. FABRIC TESTING. Mechanical devices
used to test fabric by pressing against or
piercing the finished fabric are not FAA approved
and are used at the discretion of the
mechanic to base an opinion on the general fabric
condition. Punch test accuracy will depend
on the individual device calibration, total coating
thickness, brittleness, and types of coatings
and fabric. Mechanical devices are not applicable
to glass fiber fabric that will easily shear
and indicate a very low reading regardless of
the true breaking strength. If the fabric tests in
the lower breaking strength range with the mechanical
punch tester or if the overall fabric
cover conditions are poor, then more accurate
field tests may be made. Cut a 1-1/4-inch wide
by 4-inch long sample from a top exposed surface,
remove all coatings and ravel the edges to
a 1-inch width. Clamp each end between suitable
clamps with one clamp anchored to a support
structure while a load is applied (see table
2-1) by adding sand in a suitable container
suspended a few inches above the floor. If the
breaking strength is still in question, a sample
should be sent to a qualified testing laboratory
and breaking strength tests made in accordance
with American Society of Testing Materials
(ASTM) publication D5035.

[Steve Pierce]

Cut those strips out of your plane and if it pulls good your good to go.

[cubdrvr]

I guess I could've read that.......

I have to assume that these FAR's were established for, and not amended, grade A cotton.

[FlipFlop]

I guess I could've read that.......

I have to assume that these FAR's were established for, and not amended, grade A cotton.

Dave, realizing that the mail's pretty slow in South Dakota, I've taken this opportunity to copy and print the pertinent portion of AC 43.13-1B for you so that you can be up-to-date with the rest of the World... -1B came out in 1998...

CHAPTER 2. FABRIC COVERING
SECTION 1. PRACTICES AND PRECAUTIONS
2-1. GENERAL. Cotton and Irish linen fabrics
were the airframe coverings of choice from
WWI through the 1950?s. However, increases
in cost and the short lifespan of natural fabrics
became the driving factors which resulted in
almost 100 percent replacement of original airframe
fabrics by man-made, STC-approved,
polyester, and glass filament fabric.
2-2. PROBLEM AREAS.
a. Deterioration. Polyester fabric deteriorates
only by exposure to ultraviolet radiation
as used in an aircraft covering environment.
When coatings completely protect the fabric its
service life is infinite. Therefore, it is very important
to thoroughly protect the structure
from deterioration before covering and provide
adequate inspection access to all areas of fabric-
covered components to allow inspection for
corrosion, wood rot, and mice infestation.
Multiple drain holes in the lower ends of all
fabric-covered sections also provide needed
ventilation to remove condensation.
b. Tension. Polyester fabric obtains
maximum tension on an airframe at 350 §F,
and will not be excessive on aircraft originally
covered with natural fabric and 12 coats of Nitrate
or Butyrate Dope. However, dope applied
over full heat-tauted fabric can develop
excess tension after aging and damage light aircraft
structures. Coatings other than dope will
not increase fabric tension after aging. The
heat-tauting instructions given in the manual of
each STC-approved covering process should
be followed.
2-3. AIRCRAFT FABRIC-SYNTHETIC.
a. STC-Approved Covering Materials.
There is a wide selection of STC-approved
covering materials available which utilize synthetic
fabric falling within the generic class
?Polyester? and may vary in characteristics.
Difference in the fabric may be denier, tenacity,
thread count, weight, shrink, tension, and
weave style.
b. Polyester Filaments. Polyester Filaments
are manufactured by polymerization of
various select acids and alcohols, then extruding
the resulting molten polymers through
spinnerets to form filaments. The filaments are
heat stretched to reduce to the desired denier
or size. It is the heat stretching that imparts a
memory in the filaments causing them to try
and return to their original shorter length when
reheated at a controlled temperature. Overheating
will cancel the memory and melt the
filaments.
c. Covering Procedures. Coating types,
covering accessories, and covering procedures
also may vary; therefore, the covering procedures
given in the pertinent manuals must be
followed to comply with the STC. The FAA
STC-approved installation takes precedence
over instructions in this advisory circular.
d. Installation. Initial installation of polyester
fabric is similar to natural fabric. The fabric
is installed with as little slack as possible,
considering fittings and other protrusions. It
may be sewn into an envelope, installed as a
blanket, or installed by cementing to the airframe
with a fabric cement. Each STC may
differ in the cement seam overlap, type of sewn
seam, heat shrinking procedures, and temperature.

[cubdrvr]

What the heck is -1B?

What I was wondering is if testing for Ceconite is that same as it reads for cotton........evidently it is??

...........and, BTW, the mail is not slow in SD..........just some of us residents.

[FlipFlop]

What the heck is -1B?

If I ever have a need for it, maybe I can borrow your CAM 18...

[FlipFlop]

What I was wondering is if testing for Ceconite is that same as it reads for cotton........evidently it is??

If you mean the 46# and 56#, the answer's yes...

[fobjob]

It's been my experience that when the fabric fails the Maule fabric tester, then it pull tests at about 65 lbs. per lineal inch......so test with the Maule, then pull test it when it fails the former....

[Bill Ingerson]

This topic is of great interest to me. I hope to own a cub someday so Im looking at alot of older planes. I have always had hot rods and race cars and the outward appearance paint ect. is always important. When it comes to planes, from what I see, the older cottons would only last around 10 years then its time to recover. Thats also when you change some of the wires, pulleys, check for damage, bent or rusted tubes ect. then your good for another 10 or more years. I see alot of planes advertized that its the original paint and fabric, looks like new ect. I guess what Im thinking is whats under the fabric ? I know when I buy a plane thats been covered for 15 years or more, its time to recover and check out the frame ect. I might not have been thinking this way, untill I looked at a PA-18 frame that was powder coated about 10 years ago. The frame has holes in it that you can honestly drop a dime into, along with some bad tubes ect. This frame will come to the Snohomish Wash SuperCub flyin on 26th and 27th of June (this week end ) to be displayed. I sometimes hear comments like The only thing holding the plane together was the fabric. Im starting to believe some of that. A friend rebuilding a PA-12 noticed what looked like a crack where the motor bolts to the motor mount. He pulled the motor off and looked closer to find alot of rust under the powder coating. Its my opinion, that powder coating hides to many problems under the coating. The top fuel funny cars and dragster wont even paint the frames so they can spot cracks early on.

[fobjob]

It helps a LOT to live in the high desert. My wings have original '66 cotton on them, and pull test at 68 pounds. The finish looks bad, but pristine underneath. That's because it's been hangered it's entire life. My fuse has '78 ceconite, and also pulls at 68 pounds, due to inadaquate silver application. In my opinion, the dark blue fungicide applied to cotton goes a long ways towards absorbing uv. But, I have had corrosion on my lower longerons, which resulted in some major surgery, and about 1000 stitches....

So, after the punch test has been failed, the pull test has bit the dust, all the fabric is finally stripped off the airframe and all you have left is a naked plane, what do you use to strip the old glue ? I have been using MEK soaked towels but think there has to be a better way. Suggestions ?

[Cimarron]

sandblast is still the best way but be careful of overheating the tubing with the sand

[bobnall]

My project is at the point where we will start sandblasting the airframe tomorrow morning. To prep it for the sandblaster, we will LIGHTLY heat the tubing with a torch and immediately wire brush it to remove grease, oils and dirt, and this will also help to loosen up the old primer.

We've done this on part of the airframe that needed repair and have not seen any damage. The key here is to not get the tubing hot. I'll be able to give another report on how well the sandblasting removes the old primer tomorrow night.

-Bob

[flyer]

look in the logs. if they dont specifically talk about other things being replaced and the frame inspected, i would consider you have the equivalent of a 40 year old cover job. after twenty years you really shouldnt pay more for a plane with a cover on it over one that was sitting on the field stripped of all fabric. which is what i would prefer as then i could see what i had in store for me.

I took my rudder frame to a place that does soda ash blasting yesterday. The results were pretty decent. After removing the paint and old glue, you could still see marks on the steel where it had been sanded with fine grit paper or scotch brite. Everything came off pretty easy. The blaster said that the process will not remove rust, which will have to be done with sand blasting or other mechanical means, or they could do a combination of sand/soda blasting. They also said to bring in as many pieces at one time as possible to save money overall.

Cheers
Wayne

[CptKelly]

Did you say, "Soda Ash"? Soda ash is a precursor to Sodium Hydroxide, or caustic soda..... That has the potential to be quite corrosive. If you touch a wet hand to your treated part, and it feels slick, some of that chemical is still on your part, and the only real way to treat it is to use some kind of mild acid, like vinegar, and wash this off with water. Caustic soda does not wash off well with plain water.

Mike

[fobjob]

flyer, the longeron corrosion was due to some improper painting after welding the longerons there back in '97 after an unscheduled landing (?) at Mile Hi, Id. So, things don't seem to be too bad, overall. I do some exploratory surgery on it every year or so to keep ahead of any surprises....fob

OOPS "Soda" is what the blaster said. I added the ash. I called for a clarification and they said they use bicarbonate of soda. It will leave a very slight residue that is removed with water. After blasting, they will rinse and then epoxy prime the pieces. I asked if their process would harm or texturize aluminum. Only if it is very thin (like the leading edge) was the response.

[Fortysix12]

What is required by law and recorded in the log book for the annual inspection with regards to testing an airplane that is still covered in Grade A cotton. Looks airworthy, and visually satisfactory but from the annual and AI sign off what must be done at starting at what year to continue airworthyness and be signed off, and where can I read this to document .

[ron]

My advice to anyone is to get a fabric test.I had a supercub,2 years from a full rebuild that failed a Maule test on the fabric.Admittedly it was grade A cotton,but none the less it failed.I ended up paying for a second recover.In aviation trust no one,not even yourself and you might survive.Advice from a professional pilot of 50 years who has been ripped off too many times.

[Fortysix12]

I aggree with your advice but I need to know from from a legal documentation protocol and reference.

[bob turner]

My advice would be to not cover in grade A unless you have a manufacture date on the raw cloth, and it is recent. I do not believe a fabric test is mandatory at annual.

[Wingwrench]

To answer your question, there is no requirement for a specific test for fabric.

From AC 43.13 Apenndix D Scope and Detail of Annual/100 hr inspections,

"(b) Each person performing an annual or 100-hour inspection shall inspect (where applicable) the following components of the fuselage and hull group:

(1) Fabric and skin—for deterioration, distortion, other evidence of failure, and defective or insecure attachment of fittings."

It is either airworthy or it isn't, there are no specific tests required. Methods are discussed in above posts. I have seen 20 year old grade A punch 80 on a Maule tester and I have seen 5 year old punch 15.

Jack

[T.J.]

Yep.
Somewhere in my old brain, I seem to remember fabric tests are not required. Airworthiness of the fabric is up to the AI doing the annual. Judgement call.

[flylowslow]

Legal Documentation and Protocol..........I like that!!..........I'm going to consult my attorney first(do i have one?).........I always thought the AC43.13 was the bible, along with the supplemental STC. We sure know how to make aviation difficult don't we? Your piers will give you the best advice if you have to pull the fabric off..........but then again..........who decides that the fabric should come off? A totally different topic.........
Keep Flying

[Steve Pierce]

AC43.13 Chapter 2 Paragraph 2-33 and 2-34.


2-33. STRENGTH CRITERIA FOR
AIRCRAFT FABRIC. Minimum performance standards for new intermediate-grade fabric are specified in TSO-C14b, which references AMS 3804C. Minimum performance
standards for new Grade A fabric are specified
in TSO-C15d, which references AMS 3806D.
a. The condition of the fabric covering
must be determined on every 100-hour and annual inspection, because the strength of the
fabric is a definite factor in the airworthiness
of an airplane. Fabric is considered to be airworthy until it deteriorates to a breaking
strength less than 70 percent of the strength of
new fabric required for the aircraft. For example, if grade-A cotton is used on an airplane
that requires only intermediate fabric, it can
deteriorate to 46 pounds per inch width
(70 percent of the strength of intermediate fabric) before it must be replaced
b. Fabric installed on aircraft with a
wing loading less than 9 lb. per square foot
(psf), and a Vne less than 160 mph, will be
considered unairworthy when the breaking
strength has deteriorated below 46 lb. per inch
width, regardless of the fabric grade. Fabric
installed on aircraft with a wing loading of
9 lb. per square foot and over, or a Vne of
160 mph and over, will be considered unairworthy when the breaking strength has deteriorated below 56 lb. per inch width.
c. Fabric installed on a glider or sailplane with a wing loading of 8 lb. per square
foot and less, and a Vne of 135 mph or less,
will be considered unairworthy when the fabric
breaking strength has deteriorated below 35 lb.
per inch width, regardless of the fabric grade





2-34. FABRIC TESTING. Mechanical devices used to test fabric by pressing against or
piercing the finished fabric are not FAA approved and are used at the discretion of the
mechanic to base an opinion on the general
fabric condition. Punch test accuracy will depend on the individual device calibration, total
coating thickness, brittleness, and types of
coatings and fabric. Mechanical devices are
not applicable to glass fiber fabric that will
easily shear and indicate a very low reading
regardless of the true breaking strength. If the
fabric tests in the lower breaking strength
range with the mechanical punch tester or if
the overall fabric cover conditions are poor,
then more accurate field tests may be made.
Cut a 1-1/4-inch wide by 4-inch long sample
from a top exposed surface, remove all coatings and ravel the edges to a 1-inch width.
Clamp each end between suitable clamps with
one clamp anchored to a support structure
while a load is applied (see table 2-1) by adding sand in a suitable container suspended a
few inches above the floor. If the breaking
strength is still in question, a sample should be
sent to a qualified testing laboratory and
breaking strength tests made in accordance
with American Society of Testing Materials
(ASTM) publication D5035

http://rgl.faa.gov/Regulatory_and_Gu...Chapter 02.pdf

[fobjob]

If you are 'screening' with the punch tester, beware that it will break through at a false low value if you have not removed all the dope from the test spot. It compares pretty closely with the pull test if the dope has been removed. The pull test, must also be done with the dope removed from the center (break) section. If it's urethane, and/or you can't remove the finish from the weave, then good luck....???...

[bob turner]

If you are an IA and do not want to do Cub annuals, start testing fabric as above. Opinion.

[skywagon8a]

It also makes a difference where you do the test. And with that thought, whether you are buying or selling.

Also, It makes a tremendous difference as to how and who did the job in the first place and where and how it was stored. I have seen grade A and Irish linen fabric that has remained airworthy for more than 30 and 40 years. Those were the exception. Have also seen it only last a couple of years.

[Steve Pierce]

Last batch of cotton around here only lasted a few years. Polyester fabrics last indefinitely if UV blocker is good but what is underneath is the concern.

1971 PA18 original fabric.

[bob turner]

I am with Steve on this. I looked at an Amphib for a buddy- primo on the outside. Went in through the rear fuselage inspection holes, and was able to dig holes in the lower longeron with my fingernail. Asking price was only $ 120 K.