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Moose: Elevator Tip Skin cracks

 
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tedwaltman(at)i1ci.com
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PostPosted: Sun May 07, 2006 4:44 pm    Post subject: Moose: Elevator Tip Skin cracks Reply with quote

Guess I'm just lucky to find these things. Hopefully by documenting the issues I find such will help others still in the build process or prompt others that are now flying to double check their planes.
Last year I discovered small cracks in the underside of both elevator tip skins (part # EL-313). I drilled relief holes and kept an eye on them. On the left side, I had to drill a second set of holes later in the year.
Looking at the extent of the cracks, particularly on the left (pilot) side it is evident that a major "redo" of this area is now in order. As such, I've asked a few friends what techniques they might suggest....
[ Please see the rest of my comments and pictures here: http://www.i1ci.com/Flying/Moose/Elevator/Elevator.html ]
Thank you for your input.
Ted Waltman
Moose N142SR


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ScottA



Joined: 05 Jan 2006
Posts: 100
Location: Park City, UT

PostPosted: Sun May 07, 2006 7:01 pm    Post subject: Moose: Elevator Tip Skin cracks Reply with quote

Ted,
Thanks for sharing.  This is the only way we will get all the kinks worked out of our airplanes.  It looks to me like the moment arm of the elevator counter weights is too much for the structure and the bottom skin is just trying to buckle under compression.  You’re only getting cracks on the bottom most likely from the loads imposed on landings (No, I am not saying you are making hard landings <grin>) just thinking it is not a vibration problem like the other cracks.
 
I checked out the pictures and comments on your website.  The sea fin mod and beef up was only on the Stabilizer end rib and rear spar under the outboard elevator hinge, it had nothing to do with the elevator itself – what you have is new, or at least no one else has brought it up yet.
 
I would take the path of least resistance and use your second idea for a fix.  Just add a full length doubler that spans the elevator end rib and the tip counterbalance rib.  I would also add external doubler plates on the top and bottom that span that area, I doubt they would need to go all the way.  You mention about being able to pick up the elevator tip weight – not a problem you can drill right into the soft lead and put rivet right into it.  That is the way your aileron balance weights are held in.
 
The amazing thing, looking at your pictures, is that you do not have the cracks on the stabilizer end ribs and you do not have the reinforcement per the bulletin in there.
 
Scott
Moose 174
 
 

From: owner-murphymoose-list-server(at)matronics.com [mailto:owner-murphymoose-list-server(at)matronics.com] On Behalf Of Ted Waltman
Sent: Sunday, May 07, 2006 6:44 PM
To: murphymoose-list(at)matronics.com
Subject: Moose: Elevator Tip Skin cracks

 
Guess I'm just lucky to find these things. Hopefully by documenting the issues I find such will help others still in the build process or prompt others that are now flying to double check their planes.
Last year I discovered small cracks in the underside of both elevator tip skins (part # EL-313). I drilled relief holes and kept an eye on them. On the left side, I had to drill a second set of holes later in the year.
Looking at the extent of the cracks, particularly on the left (pilot) side it is evident that a major "redo" of this area is now in order. As such, I've asked a few friends what techniques they might suggest....
[ Please see the rest of my comments and pictures here: http://www.i1ci.com/Flying/Moose/Elevator/Elevator.html ]
Thank you for your input.
Ted Waltman
Moose N142SR


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ScottA



Joined: 05 Jan 2006
Posts: 100
Location: Park City, UT

PostPosted: Sun May 07, 2006 7:10 pm    Post subject: Moose: Elevator Tip Skin cracks Reply with quote

Just to add, if you are going to be drilling out the top and bottom skins there anyway it wouldn’t be too hard to add and internal doublers on both sides that pick up the spar too.
 
Scott
 

From: owner-murphymoose-list-server(at)matronics.com [mailto:owner-murphymoose-list-server(at)matronics.com] On Behalf Of Scott Aldrich
Sent: Sunday, May 07, 2006 9:01 PM
To: murphymoose-list(at)matronics.com
Subject: RE: MurphyMoose-List: Moose: Elevator Tip Skin cracks

 
Ted,
Thanks for sharing.  This is the only way we will get all the kinks worked out of our airplanes.  It looks to me like the moment arm of the elevator counter weights is too much for the structure and the bottom skin is just trying to buckle under compression.  You’re only getting cracks on the bottom most likely from the loads imposed on landings (No, I am not saying you are making hard landings <grin>) just thinking it is not a vibration problem like the other cracks.
 
I checked out the pictures and comments on your website.  The sea fin mod and beef up was only on the Stabilizer end rib and rear spar under the outboard elevator hinge, it had nothing to do with the elevator itself – what you have is new, or at least no one else has brought it up yet.
 
I would take the path of least resistance and use your second idea for a fix.  Just add a full length doubler that spans the elevator end rib and the tip counterbalance rib.  I would also add external doubler plates on the top and bottom that span that area, I doubt they would need to go all the way.  You mention about being able to pick up the elevator tip weight – not a problem you can drill right into the soft lead and put rivet right into it.  That is the way your aileron balance weights are held in.
 
The amazing thing, looking at your pictures, is that you do not have the cracks on the stabilizer end ribs and you do not have the reinforcement per the bulletin in there.
 
Scott
Moose 174
 
 


From: owner-murphymoose-list-server(at)matronics.com [mailto:owner-murphymoose-list-server(at)matronics.com] On Behalf Of Ted Waltman
Sent: Sunday, May 07, 2006 6:44 PM
To: murphymoose-list(at)matronics.com
Subject: Moose: Elevator Tip Skin cracks

 
Guess I'm just lucky to find these things. Hopefully by documenting the issues I find such will help others still in the build process or prompt others that are now flying to double check their planes.
Last year I discovered small cracks in the underside of both elevator tip skins (part # EL-313). I drilled relief holes and kept an eye on them. On the left side, I had to drill a second set of holes later in the year.
Looking at the extent of the cracks, particularly on the left (pilot) side it is evident that a major "redo" of this area is now in order. As such, I've asked a few friends what techniques they might suggest....
[ Please see the rest of my comments and pictures here: http://www.i1ci.com/Flying/Moose/Elevator/Elevator.html ]
Thank you for your input.
Ted Waltman
Moose N142SR


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smithbill2(at)gmail.com
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PostPosted: Tue May 09, 2006 6:12 am    Post subject: Moose: Elevator Tip Skin cracks Reply with quote

Did you ask Darryl about a fix? Seems just a thicker skin over the
top and bottom would be enough with maybe the end tie together too.

Thanks for posting this information, most guys would not for fear of
others thinking it was hard landings that caused it, particularly if
no one else reports it. Any chance the builder put "extra" weight in
there trying to completely balance the elevator or does it hang
trailing edge down like most of them do?

Bill

On 5/7/06, Ted Waltman <tedwaltman(at)i1ci.com> wrote:
Quote:

Guess I'm just lucky to find these things. Hopefully by documenting the
issues I find such will help others still in the build process or prompt
others that are now flying to double check their planes.

Last year I discovered small cracks in the underside of both elevator tip
skins (part # EL-313). I drilled relief holes and kept an eye on them. On
the left side, I had to drill a second set of holes later in the year.

Looking at the extent of the cracks, particularly on the left (pilot) side
it is evident that a major "redo" of this area is now in order. As such,
I've asked a few friends what techniques they might suggest....

[ Please see the rest of my comments and pictures here:
http://www.i1ci.com/Flying/Moose/Elevator/Elevator.html ]

Thank you for your input.

Ted Waltman

Moose N142SR


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tedwaltman(at)i1ci.com
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PostPosted: Tue May 09, 2006 6:24 am    Post subject: Moose: Elevator Tip Skin cracks Reply with quote

Darryl replied suggesting a patch plate on top of the cracks extending fore
and aft to pick up sufficient rivets.

I think I'll reskin it with .032 and put a full-length .062 reinforcing
plate along the side (in other words the entire length of the elevator).

No, there is no extra weight in there. The elevator rests trailing-edge
down as one would expect.

The cracks are probably the result of landing force accumulating over lots
and lots of landings over time. Once in a while I do goof up a landing
<grin>, but nothing of sufficient force to cause the cracks due to just one
or two bad landings.

Thank you for your comments Bill.

Ted

--


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dfultz7(at)earthlink.net
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PostPosted: Tue May 09, 2006 6:58 am    Post subject: Moose: Elevator Tip Skin cracks Reply with quote

I am by no means an expert, but I would say it is a result of energy
absorbed from landings when the old style tail spring had no give in
it...... I am not critizing your landings Ted, even taxing on rough terrain
could cause this over time if nothing else to absorb unwanted energy as the
tail spring is to do.... Dale SR-033
---


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