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cracks

 
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wnorth(at)sdccd.edu
Guest
PostPosted: Mon Jan 14, 2008 8:27 am    Post subject: cracks Reply with quote
Well,

I am using the .016 skins on the RV-3, but...

I've run a trailing edge bead of silicon.

I've silicon glued the stiffener trailing tips across to each other.

I've prosealed the stiffeners to the skin to better distribute the load away
from the final rivets.

And this 'model' has 1200 hours of flight time in my -6 w/.016 skins, sans
any cracks.

The RV-3 plans also called for the stiffeners to be too long, and for the
taper to be way too short, as in 2.5 inches where it called for 6 inches in
the -6 plans, all of which was cause for yet another new box of unviolated
aluminum to arrive.

Do archive, subject words: cracks, el sucko, lightweight super-fast,
zoom-zoom, wheeeee

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randy(at)romeolima.com
Guest
PostPosted: Mon Jan 14, 2008 9:54 am    Post subject: cracks Reply with quote
Further info on getting .016 skins to live without cracking here...
http://www.romeolima.com/RV3hq/Airframe/airframe.htm#Empennage

My research among RV-4 and early RV-6 drivers showed that if constructed
using the techniques detailed above that .016 skinned flight surfaces could
have an indefinite life.

Randy Lervold
---

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deanpichon(at)msn.com
Guest
PostPosted: Mon Jan 14, 2008 10:22 am    Post subject: cracks Reply with quote
Some time ago, I called Van's on the issue and was told the cracking is (mostly) limited to those aircraft with larger engines (180HP and up). The cracking was attributed to buffeting on the tail - primarily while on the ground. Unfortunately, I have no data to support or refute this.  It was just an explanation (hypothesis?) given to me a coupe of years ago when my -4 developed a crack in the rudder skin.

Dean Pichon

[quote] From: randy(at)romeolima.com
To: rv-list(at)matronics.com
Subject: Re: cracks
Date: Mon, 14 Jan 2008 09:51:58 -0800

--> RV-List message posted by: "Randy Lervold" <randy(at)romeolima.com>

Further info on getting .016 skins to live without cracking here...
http://www.romeolima.com/RV3hq/Airframe/airframe.htm#Empennage

My research among RV-4 and early RV-6 drivers showed that if constructed
using the techniques detailed above that .016 skinned flight surfaces could
have an indefinite life.

Randy Lervold


---

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randy(at)romeolima.com
Guest
PostPosted: Mon Jan 14, 2008 10:49 am    Post subject: cracks Reply with quote
Larger engines will indeed exacerbate and accelerate the problem, but the fundamentals of proper elevator/rudder construction still apply. Build it right and go light!

Randy
[quote] ---

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pbesing(at)yahoo.com
Guest
PostPosted: Mon Jan 14, 2008 11:32 am    Post subject: cracks Reply with quote
I heard that, too....when I talked with Ken, and asked him a question about the .020 or .016 skin, he asked what engine I had...I told him 200HP IO-360, and he chuckled and said, "Well, there you go." I have finished the rudder now, with the RTV on the stiffeners...I like the idea about proseal..didn't think of it. Also like the idea of adding a stiffener...but I have the .020 skin, so we'll see what happens. I have about 900 hours on the airframe, and it was cracked well before that when I bought it 2 years ago. Stop drilled, but then the cracks started continuing, so I grounded it and built the new one.

Paul Besing
RV-4 N73DD
Arizona
---

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pbesing(at)yahoo.com
Guest
PostPosted: Mon Jan 14, 2008 11:47 am    Post subject: cracks Reply with quote
Well, it's done now with .020...so guess I'll deal with the extra pound..can use the aft CG anyway due to a light prop/starter combination. The elevators, however are fine after 18 years and 900 hours of flying.

Paul Besing
RV-4 N73DD
Arizona
---

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deanpichon(at)msn.com
Guest
PostPosted: Mon Jan 14, 2008 12:07 pm    Post subject: cracks Reply with quote
When I built my rudder (with the 0.016 skin) the use of RTV was just becoming "in vogue" and I built mine that way. So far, I have 5 cracks, all 2-3 years old. None have crack beyond the stop drill holes... yet.  I have completed a new rudder with an 0.020 skin and used Proseal, in addition to rivets, to attach the stiffeners and the spar. As soon as I complete the switchover from hinges to Skybolt fasteners, I will have both the cowl and the rudder painted and test-out the thicker skin.

Dean Pichon
Bolton, MA
[quote] Date: Mon, 14 Jan 2008 11:30:26 -0800
From: pbesing(at)yahoo.com
Subject: Re: cracks
To: rv-list(at)matronics.com

.ExternalClass DIV {;} I heard that, too....when I talked with Ken, and asked him a question about the .020 or .016 skin, he asked what engine I had...I told him 200HP IO-360, and he chuckled and said, "Well, there you go." I have finished the rudder now, with the RTV on the stiffeners...I like the idea about proseal..didn't think of it. Also like the idea of adding a stiffener...but I have the .020 skin, so we'll see what happens. I have about 900 hours on the airframe, and it was cracked well before that when I bought it 2 years ago. Stop drilled, but then the cracks started continuing, so I grounded it and built the new one.

Paul Besing
RV-4 N73DD
Arizona
---

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dasduck(at)comcast.net
Guest
PostPosted: Mon Jan 14, 2008 4:10 pm    Post subject: cracks Reply with quote
Randy is right, built right they will last.
I finished my RV-6 in 94 and I paid special attention to making sure the trailing edges of the tail surfaces were bent enought that it didn't take any pressure to 'close' them on the spars. This required some extra trimming of the siffeners so you could squeeze far enough.
I didn't use ANY type of goop anywhere, just built them carefully, and after 1050 hrs with a 180 and props ranging from wood to Hartzell and back to fixed composite, I don't have a single crack in the .016 skins.
In every case where I've seen cracks at the ends of the stiffeners, you could look down the trailing edge and it was obvious by the tension and bend at the stiffeners that the builder didn't squeeze the trailing edge enough.
Don


From: owner-rv-list-server(at)matronics.com [mailto:owner-rv-list-server(at)matronics.com] On Behalf Of Randy Lervold
Sent: Monday, January 14, 2008 10:48 AM
To: rv-list(at)matronics.com
Subject: Re: RV-List: cracks

Larger engines will indeed exacerbate and accelerate the problem, but the fundamentals of proper elevator/rudder construction still apply. Build it right and go light!

Randy
[quote] ---

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