How does a Maule tester work?

[Michael Horowitz]

I have heard folks talk about a Maule fabric tester, but I have never
seen one in action. Apparently it puts a set amount of pressure
against fabric and if the rod goes thru, then the fabric fails.

Can someone please describe the action - especially, how does the
device keep the fabric from being deflected away from the pressure? It
doesn't grip the fabric does it?

Second - anyone built a homemade tester? Is there such a thing as a
calibrated thumb? - Mike

[wmbjk]

On Thu, 20 Oct 2005 17:05:19 -0400, Michael Horowitz
> wrote:

>I have heard folks talk about a Maule fabric tester, but I have never
>seen one in action. Apparently it puts a set amount of pressure
>against fabric and if the rod goes thru, then the fabric fails.
>
>Can someone please describe the action - especially, how does the
>device keep the fabric from being deflected away from the pressure? It
>doesn't grip the fabric does it?
>
>Second - anyone built a homemade tester? Is there such a thing as a
>calibrated thumb? - Mike

http://www.ultralightnews.com/aircrafttroubleshooting/fabtest.htm
Ultralight fabric tester, modified from fan belt tension meter. 2/3 of
the way down the page.

Wayne

[[email protected]]

It's like a fish scale with a tit on the end. (push instead of pull)
The tit is about the size of a small pencil eraser.
It doesn't matter if material moves while pressure is added, it still
puts proper pressure sq/in.

wmbjk wrote:
> On Thu, 20 Oct 2005 17:05:19 -0400, Michael Horowitz
> > wrote:
>
>
>>I have heard folks talk about a Maule fabric tester, but I have never
>>seen one in action. Apparently it puts a set amount of pressure
>>against fabric and if the rod goes thru, then the fabric fails.
>>
>>Can someone please describe the action - especially, how does the
>>device keep the fabric from being deflected away from the pressure? It
>>doesn't grip the fabric does it?
>>
>>Second - anyone built a homemade tester? Is there such a thing as a
>>calibrated thumb? - Mike
>
>
> http://www.ultralightnews.com/aircrafttroubleshooting/fabtest.htm
> Ultralight fabric tester, modified from fan belt tension meter. 2/3 of
> the way down the page.
>
> Wayne

[Carl Ellis]

Mike -

The Maule tester is essentially a spring loaded rod in a tube. The rod has
a rounded end. The rod is placed against the fabric and pressure applied
to the tube which compresses a spring. There is a scale on the side of the
tube with graduations from 10 to 80 lbs in five lbs increments (if I
remember correctly). You might be able to find a picture in Aircraft
Spruce, Wicks, or other catalog.

New fabric will stretch with applied pressure all the way to 80 lbs. A
small dimple will be left in the fabric which will disappear completely
after an hour or so. Older fabric will probably experience cracking of the
dope (you can hear it) way before 80 lbs due to the plasticizer hardening.
On my previous Taylorcraft this happened at 65lbs (1977 covering). These
cracks will appear as ring worm and should be sanded down to silver and
repainted as light may degrade the fabric through the cracks.

If you are testing a prospective airplane the owner will probably be
annoyed if you use the tester and leave ring worm all over his baby.

Before selling my aircraft I had the test done. We did one or two areas to
determine where it cracked, then backed off 10 lbs for the next 30-40 test
locations. We indicated the lower number in the log book.

Hope this helps,

- Carl -

[Michael Horowitz]

What pressure is a coated fabric subjected to to determine if it has
deteriorated? - Mike

[Michael Horowitz]

Carl - is 80 psi the go/no-go point?
How do you work around the seller's understandably irritation at the
tester's hurting the surface? - Mike



Carl Ellis > wrote:

>
>Mike -
>
>The Maule tester is essentially a spring loaded rod in a tube. The rod has
>a rounded end. The rod is placed against the fabric and pressure applied
>to the tube which compresses a spring. There is a scale on the side of the
>tube with graduations from 10 to 80 lbs in five lbs increments (if I
>remember correctly). You might be able to find a picture in Aircraft
>Spruce, Wicks, or other catalog.
>
>New fabric will stretch with applied pressure all the way to 80 lbs. A
>small dimple will be left in the fabric which will disappear completely
>after an hour or so. Older fabric will probably experience cracking of the
>dope (you can hear it) way before 80 lbs due to the plasticizer hardening.
>On my previous Taylorcraft this happened at 65lbs (1977 covering). These
>cracks will appear as ring worm and should be sanded down to silver and
>repainted as light may degrade the fabric through the cracks.
>
>If you are testing a prospective airplane the owner will probably be
>annoyed if you use the tester and leave ring worm all over his baby.
>
>Before selling my aircraft I had the test done. We did one or two areas to
>determine where it cracked, then backed off 10 lbs for the next 30-40 test
>locations. We indicated the lower number in the log book.
>
>Hope this helps,
>
>- Carl -

[Carl Ellis]

Mike -

I believe that if the fabric tears at any pressure it's a no go. The Maule
tester is just one tool to use to determine fabric condition. As far as I
know the tester is not an FAA approved test but is rather a somewhat
subjective evaluation tool.

There is a whole thread on this on the Taylorcraft Forum.

I would ask the seller to have his mechanic do the test and be there while
he does it. Off the cuff I'd say walk away if the dope is cracking below
50 lbs but I'm sure that a more knowledeable person has a better feeling
for this.


- Carl -




On Fri, 21 Oct 2005 05:43:48 -0400, Michael Horowitz wrote:

> Carl - is 80 psi the go/no-go point?
> How do you work around the seller's understandably irritation at the
> tester's hurting the surface? - Mike
>
>
>
> Carl Ellis > wrote:
>
>>
>>Mike -
>>
>>The Maule tester is essentially a spring loaded rod in a tube. The rod has
>>a rounded end. The rod is placed against the fabric and pressure applied
>>to the tube which compresses a spring. There is a scale on the side of the
>>tube with graduations from 10 to 80 lbs in five lbs increments (if I
>>remember correctly). You might be able to find a picture in Aircraft


>>Spruce, Wicks, or other catalog.
>>
>>New fabric will stretch with applied pressure all the way to 80 lbs. A
>>small dimple will be left in the fabric which will disappear completely
>>after an hour or so. Older fabric will probably experience cracking of the
>>dope (you can hear it) way before 80 lbs due to the plasticizer hardening.
>>On my previous Taylorcraft this happened at 65lbs (1977 covering). These
>>cracks will appear as ring worm and should be sanded down to silver and
>>repainted as light may degrade the fabric through the cracks.
>>
>>If you are testing a prospective airplane the owner will probably be
>>annoyed if you use the tester and leave ring worm all over his baby.
>>
>>Before selling my aircraft I had the test done. We did one or two areas to
>>determine where it cracked, then backed off 10 lbs for the next 30-40 test
>>locations. We indicated the lower number in the log book.
>>
>>Hope this helps,
>>
>>- Carl -

[Michael Horowitz]

Carl - the reason I'm asking is that the covering and the engine are
the two biggies when looking to buy. We can get metrics on an engine,
and we know how to evaluate it, but it's not so clear cut with the
fabric.
The purpose of my pre-pre-purchase inspection is to weed out those
candidates I don't even want to get to the pre-inspection stage, so
I'm trying to be as independant of the A&P as I can.
OTOH, asking him to have _his_ A&P do the test certainly has merit.
- Mike


Carl Ellis > wrote:

>Mike -
>
>I believe that if the fabric tears at any pressure it's a no go. The Maule
>tester is just one tool to use to determine fabric condition. As far as I
>know the tester is not an FAA approved test but is rather a somewhat
>subjective evaluation tool.
>
>There is a whole thread on this on the Taylorcraft Forum.
>
>I would ask the seller to have his mechanic do the test and be there while
>he does it. Off the cuff I'd say walk away if the dope is cracking below
>50 lbs but I'm sure that a more knowledeable person has a better feeling
>for this.
>
>
>- Carl -
>
>
>
>
>On Fri, 21 Oct 2005 05:43:48 -0400, Michael Horowitz wrote:
>
>> Carl - is 80 psi the go/no-go point?
>> How do you work around the seller's understandably irritation at the
>> tester's hurting the surface? - Mike
>>
>>
>>
>> Carl Ellis > wrote:
>>
>>>
>>>Mike -
>>>
>>>The Maule tester is essentially a spring loaded rod in a tube. The rod has
>>>a rounded end. The rod is placed against the fabric and pressure applied
>>>to the tube which compresses a spring. There is a scale on the side of the
>>>tube with graduations from 10 to 80 lbs in five lbs increments (if I
>>>remember correctly). You might be able to find a picture in Aircraft
>
>
>>>Spruce, Wicks, or other catalog.
>>>
>>>New fabric will stretch with applied pressure all the way to 80 lbs. A
>>>small dimple will be left in the fabric which will disappear completely
>>>after an hour or so. Older fabric will probably experience cracking of the
>>>dope (you can hear it) way before 80 lbs due to the plasticizer hardening.
>>>On my previous Taylorcraft this happened at 65lbs (1977 covering). These
>>>cracks will appear as ring worm and should be sanded down to silver and
>>>repainted as light may degrade the fabric through the cracks.
>>>
>>>If you are testing a prospective airplane the owner will probably be
>>>annoyed if you use the tester and leave ring worm all over his baby.
>>>
>>>Before selling my aircraft I had the test done. We did one or two areas to
>>>determine where it cracked, then backed off 10 lbs for the next 30-40 test
>>>locations. We indicated the lower number in the log book.
>>>
>>>Hope this helps,
>>>
>>>- Carl -

[[email protected]]

There are different minimum pressures for different MAX airspeeds of the
aircraft.
A Stearman will have a different requirement than a Cub.
i'll try to find that data and post it.



Michael Horowitz wrote:
> Carl - the reason I'm asking is that the covering and the engine are
> the two biggies when looking to buy. We can get metrics on an engine,
> and we know how to evaluate it, but it's not so clear cut with the
> fabric.
> The purpose of my pre-pre-purchase inspection is to weed out those
> candidates I don't even want to get to the pre-inspection stage, so
> I'm trying to be as independant of the A&P as I can.
> OTOH, asking him to have _his_ A&P do the test certainly has merit.
> - Mike
>
>
> Carl Ellis > wrote:
>
>
>>Mike -
>>
>>I believe that if the fabric tears at any pressure it's a no go. The Maule
>>tester is just one tool to use to determine fabric condition. As far as I
>>know the tester is not an FAA approved test but is rather a somewhat
>>subjective evaluation tool.
>>
>>There is a whole thread on this on the Taylorcraft Forum.
>>
>>I would ask the seller to have his mechanic do the test and be there while
>>he does it. Off the cuff I'd say walk away if the dope is cracking below
>>50 lbs but I'm sure that a more knowledeable person has a better feeling
>>for this.
>>
>>
>>- Carl -
>>
>>
>>
>>
>>On Fri, 21 Oct 2005 05:43:48 -0400, Michael Horowitz wrote:
>>
>>
>>>Carl - is 80 psi the go/no-go point?
>>>How do you work around the seller's understandably irritation at the
>>>tester's hurting the surface? - Mike
>>>
>>>
>>>
>>>Carl Ellis > wrote:
>>>
>>>
>>>>Mike -
>>>>
>>>>The Maule tester is essentially a spring loaded rod in a tube. The rod has
>>>>a rounded end. The rod is placed against the fabric and pressure applied
>>>>to the tube which compresses a spring. There is a scale on the side of the
>>>>tube with graduations from 10 to 80 lbs in five lbs increments (if I
>>>>remember correctly). You might be able to find a picture in Aircraft
>>
>>
>>>>Spruce, Wicks, or other catalog.
>>>>
>>>>New fabric will stretch with applied pressure all the way to 80 lbs. A
>>>>small dimple will be left in the fabric which will disappear completely
>>>>after an hour or so. Older fabric will probably experience cracking of the
>>>>dope (you can hear it) way before 80 lbs due to the plasticizer hardening.
>>>>On my previous Taylorcraft this happened at 65lbs (1977 covering). These
>>>>cracks will appear as ring worm and should be sanded down to silver and
>>>>repainted as light may degrade the fabric through the cracks.
>>>>
>>>>If you are testing a prospective airplane the owner will probably be
>>>>annoyed if you use the tester and leave ring worm all over his baby.
>>>>
>>>>Before selling my aircraft I had the test done. We did one or two areas to
>>>>determine where it cracked, then backed off 10 lbs for the next 30-40 test
>>>>locations. We indicated the lower number in the log book.
>>>>
>>>>Hope this helps,
>>>>
>>>>- Carl -
>
>

[Cy Galley]

Look in AC 43.13-1B for fabric testing parameters.

--
Cy Galley - Chair,
AirVenture Emergency Aircraft Repair
A Service Project of Chapter 75
EAA Safety Programs Editor - TC
EAA Sport Pilot

> wrote in message
...
> There are different minimum pressures for different MAX airspeeds of the
> aircraft.
> A Stearman will have a different requirement than a Cub.
> i'll try to find that data and post it.
>
>
>
> Michael Horowitz wrote:
>> Carl - the reason I'm asking is that the covering and the engine are
>> the two biggies when looking to buy. We can get metrics on an engine,
>> and we know how to evaluate it, but it's not so clear cut with the
>> fabric.
>> The purpose of my pre-pre-purchase inspection is to weed out those
>> candidates I don't even want to get to the pre-inspection stage, so
>> I'm trying to be as independant of the A&P as I can.
>> OTOH, asking him to have _his_ A&P do the test certainly has merit. -
>> Mike
>>
>>
>> Carl Ellis > wrote:
>>
>>
>>>Mike -
>>>I believe that if the fabric tears at any pressure it's a no go. The
>>>Maule
>>>tester is just one tool to use to determine fabric condition. As far as
>>>I
>>>know the tester is not an FAA approved test but is rather a somewhat
>>>subjective evaluation tool.
>>>
>>>There is a whole thread on this on the Taylorcraft Forum.
>>>
>>>I would ask the seller to have his mechanic do the test and be there
>>>while
>>>he does it. Off the cuff I'd say walk away if the dope is cracking below
>>>50 lbs but I'm sure that a more knowledeable person has a better feeling
>>>for this.
>>>
>>>
>>>- Carl -
>>>
>>>
>>>
>>>
>>>On Fri, 21 Oct 2005 05:43:48 -0400, Michael Horowitz wrote:
>>>
>>>
>>>>Carl - is 80 psi the go/no-go point?
>>>>How do you work around the seller's understandably irritation at the
>>>>tester's hurting the surface? - Mike
>>>>
>>>>
>>>>
>>>>Carl Ellis > wrote:
>>>>
>>>>
>>>>>Mike -
>>>>>
>>>>>The Maule tester is essentially a spring loaded rod in a tube. The rod
>>>>>has
>>>>>a rounded end. The rod is placed against the fabric and pressure
>>>>>applied
>>>>>to the tube which compresses a spring. There is a scale on the side of
>>>>>the
>>>>>tube with graduations from 10 to 80 lbs in five lbs increments (if I
>>>>>remember correctly). You might be able to find a picture in Aircraft
>>>
>>>
>>>>>Spruce, Wicks, or other catalog.
>>>>>
>>>>>New fabric will stretch with applied pressure all the way to 80 lbs. A
>>>>>small dimple will be left in the fabric which will disappear completely
>>>>>after an hour or so. Older fabric will probably experience cracking of
>>>>>the
>>>>>dope (you can hear it) way before 80 lbs due to the plasticizer
>>>>>hardening.
>>>>>On my previous Taylorcraft this happened at 65lbs (1977 covering).
>>>>>These
>>>>>cracks will appear as ring worm and should be sanded down to silver and
>>>>>repainted as light may degrade the fabric through the cracks.
>>>>>
>>>>>If you are testing a prospective airplane the owner will probably be
>>>>>annoyed if you use the tester and leave ring worm all over his baby.
>>>>>Before selling my aircraft I had the test done. We did one or two
>>>>>areas to
>>>>>determine where it cracked, then backed off 10 lbs for the next 30-40
>>>>>test
>>>>>locations. We indicated the lower number in the log book.
>>>>>
>>>>>Hope this helps,
>>>>>
>>>>>- Carl -
>>

[Stealth Pilot]

On Fri, 21 Oct 2005 05:38:56 -0400, Michael Horowitz
> wrote:

>What pressure is a coated fabric subjected to to determine if it has
>deteriorated? - Mike

mike
I have seen a guy try to repair a wing that his arm went through just
leaning near it.
you gotta stop pussyfooting around with fabric.
make your hand into a "bird" walk down the side of the aircraft and
whang that finger into the fabric as hard as your finger can stand.
if it ever goes through you just saved yourself from a midair
breakup.
aircraft fabric in serviceable nick is pretty damn resilient. there is
a video somewhere of a kid at oshkosh bouncing on a fabric wing like a
trampoline. I'm pretty sure it actually didnt damage the wing.

next time you are in flight you should rest your hand against a
section of fuselage fabric. you'll be truely surprised at how much it
moves around.

fabric safety isnt about "its just 1 pound over the minimum strength
so I'll get another 3 months and 2 days out of it" its about making
sure that in turbulence at VNE in a steep turn nothing even looks like
coming adrift.(thats what you need to be testing for)

if you are buying an aircraft and the owner hasnt the confidence that
it will withstand a robust "birding" then that guy has just admitted
something and you should turn tail and walk away.

I get asked on occasion about fabric testing since I fly a fabric
covered aircraft (among a field which is overwhelmingly aluminium) and
I demonstrate a robust birding to the point that the guy winces at the
possible consequences. I'm actually only testing the Stits fabric to
about half it's strength. If it ever breaks he's just saved my neck.

have a look in AC43-13 at the table on page 2-2.
56psi if vne over 160mph
46psi for slower aircraft.
....but dont kid yourself that those figures may always be safe.
Stealth Pilot

[Michael Horowitz]

Thanks for the pointer; I"ll give her a look.
I don't think I could run from an irate seller, so I'll probably end
up leaving the testing to an A&P - Mike


Stealth Pilot > wrote:

>On Fri, 21 Oct 2005 05:38:56 -0400, Michael Horowitz
> wrote:
>
>>What pressure is a coated fabric subjected to to determine if it has
>>deteriorated? - Mike
>
>mike
> I have seen a guy try to repair a wing that his arm went through just
>leaning near it.
>you gotta stop pussyfooting around with fabric.
>make your hand into a "bird" walk down the side of the aircraft and
>whang that finger into the fabric as hard as your finger can stand.
> if it ever goes through you just saved yourself from a midair
>breakup.
>aircraft fabric in serviceable nick is pretty damn resilient. there is
>a video somewhere of a kid at oshkosh bouncing on a fabric wing like a
>trampoline. I'm pretty sure it actually didnt damage the wing.
>
>next time you are in flight you should rest your hand against a
>section of fuselage fabric. you'll be truely surprised at how much it
>moves around.
>
>fabric safety isnt about "its just 1 pound over the minimum strength
>so I'll get another 3 months and 2 days out of it" its about making
>sure that in turbulence at VNE in a steep turn nothing even looks like
>coming adrift.(thats what you need to be testing for)
>
>if you are buying an aircraft and the owner hasnt the confidence that
>it will withstand a robust "birding" then that guy has just admitted
>something and you should turn tail and walk away.
>
>I get asked on occasion about fabric testing since I fly a fabric
>covered aircraft (among a field which is overwhelmingly aluminium) and
>I demonstrate a robust birding to the point that the guy winces at the
>possible consequences. I'm actually only testing the Stits fabric to
>about half it's strength. If it ever breaks he's just saved my neck.
>
>have a look in AC43-13 at the table on page 2-2.
>56psi if vne over 160mph
>46psi for slower aircraft.
>...but dont kid yourself that those figures may always be safe.
>Stealth Pilot

[Michael Horowitz]

Cy -
When an A&P does a test, does he have to be prepared to repair any
damage he might do i.e. crack the paint or punch a hole? - Mike

"Cy Galley" > wrote:

>Look in AC 43.13-1B for fabric testing parameters.

[Cy Galley]

The beauty of the Maule tester is that there isn't a hole IF the fabric
passes. There can be some very minimal paint damage which is easily fixed.
If the hole punches below the minimum level, then the fabric should be
removed and replaced as it doesn't meet safe strength levels. If one
continues the test to a higher level until it punches a hole, just a drop
of paint to fill the hole can be used.


"Michael Horowitz" > wrote in message
...
> Cy -
> When an A&P does a test, does he have to be prepared to repair any
> damage he might do i.e. crack the paint or punch a hole? - Mike
>
> "Cy Galley" > wrote:
>
>>Look in AC 43.13-1B for fabric testing parameters.
>