Re: [RCSE] "YOU can break Carbon rod for stab axles, following the assignme...

[Wwing]

I had to put a carbon rod into service as a stab axle once. All I had was one 
of insufficient diameter. Luckily, I had a piece of brass tubing that it fit 
into perfectly, and the brass tube fit perfectly into the carriers in the 
stabs. I thought this was a perfect marriage of the stiffness of the carbon and 
the pliable durability of the brass. The brass tube kept the carbon from 
bending 
and the brass tube kept the carbon from getting nicked and precluded the 
eventuality of it breaking. I've probably exposed myself to the risk of being 
called an idiot by the ravaging hordes of engineers that patrol RCSE, armed as 
they are with equations and wielding calculators, and I am probably guilty of 
that, but I can say that I have lived to tell the tale.
 
Bill Wingstedt
 



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[RCSE] "YOU can break Carbon rod for stab axles, following the assignment?"

[GordySoar]

Hi Guys, 

For some reason you are commenting on whether Carbon Rods  are 'good' or 
'bad' for using as stab axles, but my thread had nothing to do  with that 
topic, 
it was about YOU finding out for yourself what kind of force it  takes to break 
a 1/8" carbon rod the length of a stab axle, about at the half  way point.  
Sounds like Brian is going to install some brass tubing over  the ends of the 
carbon rod to add a stress point, more in keeping with using the  rod for stab 
axles...but again, my assignment test is pretty clearly stated if  you should 
accept the assignment.  It won't prove that 1/8" carbon rod is  good or bad 
for stab axles but it will give you ..personally a clear idea of the  amount of 
force it takes to snap a 1/8" carbon rod...by the way it might be very  
little, the only way to find out is to try ityourselfversus talking  
about 
it :-).
 
For those of you who are not builders, understand this, carbon  splinters are 
a bitch.  So proceed at your own risk.

And remember these words, the last words you hear from a guy  from 
Kentucky"Hey watch this!"
Gordy
Please try to pay more attention in the future to what  I write :-)
 
 Sure you can't break the rod with you bare hand,  because you hands 
have soft corners. Put the carbon rod  into two brass  tube and try 
again.

I have seen 1/4"  stab rod snap in a 100"  glider on landing. The 
carbon rod rotates in the brass tubing will forma  stress point. For 
big (5/8" or larger) wing joiners, as long as it has a  carbon carrier 
and not brass , it is fine.

>>At 12:09 PM  4/25/2008, [EMAIL PROTECTED] wrote:
>>>I've seen this topic  for years and so decided to see what it would
>>>take to break a  1/8" carbon rod with my hands which have
>>>considerably higher  bending capability than a stab on one side of 
>>>a  vertical.
>>>
>>>Try it for yourself, try to use your  hands to break a 1/8" carbon
>>>rod, just past half way along its  length.
>>>It will be interesting to hear your findings bout how  easy or hard
>>>it is...and why it might be possible for a stab to  put that kind of
>>>force on the rod, with out it breaking  first.
>>>
>>>Note I didn't say it was hard, I'm asking  you interested parties and
>>>suggesters to 'do' something then  report.
>>>Gordy




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Re: [RCSE] "YOU can break Carbon rod for stab axles"

[B. Chan]

 Sure you can't break the rod with you bare hand, because you hands 
have soft corners. Put the carbon rod  into two brass tube and try 
again.


I have seen 1/4"  stab rod snap in a 100" glider on landing. The 
carbon rod rotates in the brass tubing will forma stress point. For 
big (5/8" or larger) wing joiners, as long as it has a carbon carrier 
and not brass , it is fine.


Brian


At 12:09 PM 4/25/2008, [EMAIL PROTECTED] wrote:

I've seen this topic for years and so decided to see what it would
take to break a 1/8" carbon rod with my hands which have
considerably higher bending capability than a stab on one side of 
a vertical.


Try it for yourself, try to use your hands to break a 1/8" carbon
rod, just past half way along its length.
It will be interesting to hear your findings bout how easy or hard
it is...and why it might be possible for a stab to put that kind of
force on the rod, with out it breaking first.

Note I didn't say it was hard, I'm asking you interested parties and
suggesters to 'do' something then report.
Gordy

In a message dated 4/25/2008 9:55:54 A.M. Eastern Daylight Time,
[EMAIL PROTECTED] writes:
That may be overkill, if the 1/8 was almost strong enough. Assuming that
the wall is pretty thick,  1/4" would be 8X as strong and 16X as stiff,
if I'm not mistaken. I wonder if the problem is that the rod is not very
strong crosswise, so if there's a hint of a sharp edge, maybe it will
crunch. A steel tube might be a good compromise, though the yield
strength, unless you go pretty high tech, will be maybe half or less
that of music wire. Presumably the diameter would make up for that,
given the right wall thickness, etc. (I'm assuming you'd use a little
piece of 4130 or something from Aircraft Spruce)

I wonder if one glued short lengths of brass tubing over the carbon at
the appropriate places if that wouldn't help keep local loads from
messing it up. Especially if you ground the edges to a taper. Or maybe
that's just too much trouble.

The 1/4" carbon might weigh 7 grams or so if it was 4" long.. A 1/8"
steel rod would weigh about the same for the same length. The carbon
would be much stiffer, of course. And if you loaded it carefully, with
only smooth edges, a heck of a lot stronger. However, assuming a 24"
stab with 100 square inches or so, the 1/8" joiner on the tail would
stand up to an airspeed comparable to that of a 1/2" steel rod of the
same yield strength on the wing. However, music wire tends to have a
really high yield strength.  (plus or minus a lot depending on design
details)


 : <[EMAIL PROTECTED]> wrote: Ray, I have used 1/8 cf rod
 for stab axles, and had them break. This was on my Yardbird design,
 130". I went back to steel rather than try to go to a bigger tube. My
 latest will use 1/4 cf tube for stab axles. Jack



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[RCSE] "YOU can break Carbon rod for stab axles"

[Mike Fox]

I have seen even a 1/4" CF joiner fail on the Stab of a Onyx JW.  As stated 
before, the CF has to be protected. The one I seen fail, had marks in it 
which lead to it's failure.  Changes were made to fix that problem. Just 
have to keep a close eye on CF stuff.  Great stuff if it is taken care of.


Mike


Its not so much how hard it is to break the rod when its in good
condition.  It's plenty strong.  Its knowing when the strength has
been compromised with cracking after a few dork landings or an
unfortunate vertical arrival.   They become very easy to break once
they have a crack starting to develop.

Each pilot is going to have to decide the issue for himself.  For me,
if they're not at least 1/4" in diameter I'd rather use steel.  The
nose weight is not a consideration.  I won't use a center wing rod of
carbon in any case.

Rick

At 12:09 PM 4/25/2008, [EMAIL PROTECTED] wrote:

I've seen this topic for years and so decided to see what it would
take to break a 1/8" carbon rod with my hands which have
considerably higher bending capability than a stab on one side of a 
vertical.


Try it for yourself, try to use your hands to break a 1/8" carbon
rod, just past half way along its length.
It will be interesting to hear your findings bout how easy or hard
it is...and why it might be possible for a stab to put that kind of
force on the rod, with out it breaking first.

Note I didn't say it was hard, I'm asking you interested parties and
suggesters to 'do' something then report.
Gordy

In a message dated 4/25/2008 9:55:54 A.M. Eastern Daylight Time,
[EMAIL PROTECTED] writes:
That may be overkill, if the 1/8 was almost strong enough. Assuming that
the wall is pretty thick,  1/4" would be 8X as strong and 16X as stiff,
if I'm not mistaken. I wonder if the problem is that the rod is not very
strong crosswise, so if there's a hint of a sharp edge, maybe it will
crunch. A steel tube might be a good compromise, though the yield
strength, unless you go pretty high tech, will be maybe half or less
that of music wire. Presumably the diameter would make up for that,
given the right wall thickness, etc. (I'm assuming you'd use a little
piece of 4130 or something from Aircraft Spruce)

I wonder if one glued short lengths of brass tubing over the carbon at
the appropriate places if that wouldn't help keep local loads from
messing it up. Especially if you ground the edges to a taper. Or maybe
that's just too much trouble.

The 1/4" carbon might weigh 7 grams or so if it was 4" long.. A 1/8"
steel rod would weigh about the same for the same length. The carbon
would be much stiffer, of course. And if you loaded it carefully, with
only smooth edges, a heck of a lot stronger. However, assuming a 24"
stab with 100 square inches or so, the 1/8" joiner on the tail would
stand up to an airspeed comparable to that of a 1/2" steel rod of the
same yield strength on the wing. However, music wire tends to have a
really high yield strength.  (plus or minus a lot depending on design
details)

> : <[EMAIL PROTECTED]> wrote: Ray, I have used 1/8 cf rod
> for stab axles, and had them break. This was on my Yardbird design,
> 130". I went back to steel rather than try to go to a bigger tube. My
> latest will use 1/4 cf tube for stab axles. Jack



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"unsubscribe" requests to [EMAIL PROTECTED]  Please note that subscribe and unsubscribe 
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RE: [RCSE] "YOU can break Carbon rod for stab axles"

[Kurt Zimmerman]

"Unfortunate vertical arrival" . AKA "DORK"?  Rick you certainly have a way
with words.

 



Kurt

 

From: Rick Eckel [mailto:[EMAIL PROTECTED] 
Sent: Friday, April 25, 2008 1:26 PM
To: [EMAIL PROTECTED]; Soaring@airage.com
Subject: Re: [RCSE] "YOU can break Carbon rod for stab axles"

 

Its not so much how hard it is to break the rod when its in good condition.
It's plenty strong.  Its knowing when the strength has been compromised with
cracking after a few dork landings or an unfortunate vertical arrival.
They become very easy to break once they have a crack starting to develop.  

Each pilot is going to have to decide the issue for himself.  For me, if
they're not at least 1/4" in diameter I'd rather use steel.  The nose weight
is not a consideration.  I won't use a center wing rod of carbon in any
case. 

Rick

Re: [RCSE] "YOU can break Carbon rod for stab axles"

[Rick Eckel]

Its not so much how hard it is to break the rod when its in good 
condition.  It's plenty strong.  Its knowing when the strength has 
been compromised with cracking after a few dork landings or an 
unfortunate vertical arrival.   They become very easy to break once 
they have a crack starting to develop.


Each pilot is going to have to decide the issue for himself.  For me, 
if they're not at least 1/4" in diameter I'd rather use steel.  The 
nose weight is not a consideration.  I won't use a center wing rod of 
carbon in any case.


Rick

At 12:09 PM 4/25/2008, [EMAIL PROTECTED] wrote:
I've seen this topic for years and so decided to see what it would 
take to break a 1/8" carbon rod with my hands which have 
considerably higher bending capability than a stab on one side of a vertical.


Try it for yourself, try to use your hands to break a 1/8" carbon 
rod, just past half way along its length.
It will be interesting to hear your findings bout how easy or hard 
it is...and why it might be possible for a stab to put that kind of 
force on the rod, with out it breaking first.


Note I didn't say it was hard, I'm asking you interested parties and 
suggesters to 'do' something then report.

Gordy

In a message dated 4/25/2008 9:55:54 A.M. Eastern Daylight Time, 
[EMAIL PROTECTED] writes:

That may be overkill, if the 1/8 was almost strong enough. Assuming that
the wall is pretty thick,  1/4" would be 8X as strong and 16X as stiff,
if I'm not mistaken. I wonder if the problem is that the rod is not very
strong crosswise, so if there's a hint of a sharp edge, maybe it will
crunch. A steel tube might be a good compromise, though the yield
strength, unless you go pretty high tech, will be maybe half or less
that of music wire. Presumably the diameter would make up for that,
given the right wall thickness, etc. (I'm assuming you'd use a little
piece of 4130 or something from Aircraft Spruce)

I wonder if one glued short lengths of brass tubing over the carbon at
the appropriate places if that wouldn't help keep local loads from
messing it up. Especially if you ground the edges to a taper. Or maybe
that's just too much trouble.

The 1/4" carbon might weigh 7 grams or so if it was 4" long.. A 1/8"
steel rod would weigh about the same for the same length. The carbon
would be much stiffer, of course. And if you loaded it carefully, with
only smooth edges, a heck of a lot stronger. However, assuming a 24"
stab with 100 square inches or so, the 1/8" joiner on the tail would
stand up to an airspeed comparable to that of a 1/2" steel rod of the
same yield strength on the wing. However, music wire tends to have a
really high yield strength.  (plus or minus a lot depending on design
details)

> : <[EMAIL PROTECTED]> wrote: Ray, I have used 1/8 cf rod
> for stab axles, and had them break. This was on my Yardbird design,
> 130". I went back to steel rather than try to go to a bigger tube. My
> latest will use 1/4 cf tube for stab axles. Jack
> --


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"subscribe" and "unsubscribe" requests to 
[EMAIL PROTECTED]  Please note that subscribe and 
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[RCSE] "YOU can break Carbon rod for stab axles"

[GordySoar]

I've seen this topic for years and so decided to see what it would take to  
break a 1/8" carbon rod with my hands which have considerably higher bending  
capability than a stab on one side of a vertical.
 
Try it for yourself, try to use your hands to break a 1/8" carbon rod, just  
past half way along its length.
It will be interesting to hear your findings bout how easy or hard it  
is...and why it might be possible for a stab to put that kind of force on the  
rod, 
with out it breaking first.
 
Note I didn't say it was hard, I'm asking you interested parties and  
suggesters to 'do' something then report.
Gordy
 
 
In a message dated 4/25/2008 9:55:54 A.M. Eastern Daylight Time,  
[EMAIL PROTECTED] writes:

That may  be overkill, if the 1/8 was almost strong enough. Assuming that 
the wall  is pretty thick,  1/4" would be 8X as strong and 16X as stiff, 
if I'm  not mistaken. I wonder if the problem is that the rod is not very 
strong  crosswise, so if there's a hint of a sharp edge, maybe it will 
crunch. A  steel tube might be a good compromise, though the yield 
strength, unless  you go pretty high tech, will be maybe half or less  
that of music  wire. Presumably the diameter would make up for that, 
given the right wall  thickness, etc. (I'm assuming you'd use a little 
piece of 4130 or  something from Aircraft Spruce)

I wonder if one glued short lengths of  brass tubing over the carbon at 
the appropriate places if that wouldn't  help keep local loads from 
messing it up. Especially if you ground the  edges to a taper. Or maybe 
that's just too much trouble.

The 1/4"  carbon might weigh 7 grams or so if it was 4" long.. A 1/8" 
steel rod  would weigh about the same for the same length. The carbon 
would be much  stiffer, of course. And if you loaded it carefully, with 
only smooth  edges, a heck of a lot stronger. However, assuming a 24" 
stab with 100  square inches or so, the 1/8" joiner on the tail would 
stand up to an  airspeed comparable to that of a 1/2" steel rod of the 
same yield strength  on the wing. However, music wire tends to have a 
really high yield  strength.  (plus or minus a lot depending on design  
details)

> : <[EMAIL PROTECTED]> wrote: Ray,  I have used 1/8 cf rod 
> for stab axles, and had them break. This was  on my Yardbird design, 
> 130". I went back to steel rather than try to  go to a bigger tube. My 
> latest will use 1/4 cf tube for stab axles.  Jack
> -- 


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"unsubscribe" requests to  [EMAIL PROTECTED]  Please note that 
subscribe and unsubscribe  messages must be sent in text only format with MIME 
turned off.  Email  sent from web based email such as Hotmail and AOL are 
generally NOT in text  format





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