VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #11  
Old 06-25-2018, 09:39 AM
DaveO DaveO is offline
 
Join Date: Dec 2012
Location: Greenfield, IN
Posts: 275
Default

Mel,
I do not understand your post about attaching the stiffener to the bulkhead. On the 14 the stiffeners are not attached to the bulkhead as per plans. They run through the bulkheads.
Please explain more.
Thanks
__________________
Dave

RV-7A N1243A Sold
#140479 RV-14A N1479B Reserved
Reply With Quote
  #12  
Old 06-25-2018, 11:34 AM
Tom Martin Tom Martin is online now
 
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,423
Default

We have had some issues with the stiffeners in the flying RV14 that I built. Mel is correct that cracks may occur at the end of stiffeners that are not attached to the adjacent bulkhead. I first encountered this years ago when a friend installed stiffeners on the bottom of a RV6 to stop oil canning. After a short while cracks occurred on the bottom of the fuse. The same thing has happened on the RV14



This has occurred in the aft fuselage in ours, in two locations and is not the only aircraft that has experienced this. We passed this information on to Vans a few months ago and have been waiting for the engineers to come up with a fix.

This picture shows where they are on the lower aft fuselage. The cracks were stop drilled and you see safety wire sticking through just for reference as to where they are. The aircraft continues to fly, with no further cracks.

A fix will likely be some sort of bracket that will tie the stiffener to the bulkhead.


__________________
Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger

Fairlea Field
St.Thomas, Ontario Canada, CYQS
fairleafield@gmail.com
Reply With Quote
  #13  
Old 06-25-2018, 11:37 AM
bkervaski's Avatar
bkervaski bkervaski is offline
 
Join Date: Mar 2017
Location: Birmingham, Alabama
Posts: 851
Default

Since itís not structural perhaps just proseal and no rivets?
__________________
#140376 RV-14A QB IO-390 Thunderbolt
Registered: N196
Progress: Flying!
Reply With Quote
  #14  
Old 06-25-2018, 06:46 PM
DaveO DaveO is offline
 
Join Date: Dec 2012
Location: Greenfield, IN
Posts: 275
Default

Thanks for the post about the cracks. I did not understand how I could attach them. But my fix to add stiffeners will be put on hold, maybe as some suggested to Pro Seal them on, may be the way to go.
__________________
Dave

RV-7A N1243A Sold
#140479 RV-14A N1479B Reserved
Reply With Quote
  #15  
Old 06-25-2018, 06:53 PM
Mel's Avatar
Mel Mel is online now
 
Join Date: Mar 2005
Location: Dallas area
Posts: 10,150
Default

Proseal will have the same effect. The problem occurs because the stiffener is bonded to the skin making them vibrate together. That vibration is now concentrated at the end of the stiffener. It vibrates as a unit and the bulkhead holds the skin rigid. If the stiffener is attached to the bulkhead, it forms a single unit.
In cases where the stiffener is continuous "through" the bulkhead, it's not a problem.
Not sure how to put it clearly in words, but I have seen quite a few skin cracks under these circumstances.
__________________
Mel Asberry..DAR since last century
A&P/EAA Tech Counselor/Flight Advisor/Nat'l Test Pilot School
Specializing in Amateur-Built and Light-Sport Aircraft
<rvmel(at)icloud.com>
North Texas (8TA5)
RV-6 Flying since 1993, 172hp O-320, 3-Blade Catto (since 2003)
Legend Cub purchased 12/2017
FRIEND of the RV-1
Eagle's Nest Mentor
Recipient of Wright Brothers "Master Pilot" Award
Reply With Quote
  #16  
Old 06-25-2018, 06:55 PM
Mel's Avatar
Mel Mel is online now
 
Join Date: Mar 2005
Location: Dallas area
Posts: 10,150
Default

Quote:
Originally Posted by bkervaski View Post
Since itís not structural perhaps just proseal and no rivets?
The cracks don't always occur at the rivet. Often the skin cracks at the end of the stiffener. So in that case proseal wouldn't change anything.
__________________
Mel Asberry..DAR since last century
A&P/EAA Tech Counselor/Flight Advisor/Nat'l Test Pilot School
Specializing in Amateur-Built and Light-Sport Aircraft
<rvmel(at)icloud.com>
North Texas (8TA5)
RV-6 Flying since 1993, 172hp O-320, 3-Blade Catto (since 2003)
Legend Cub purchased 12/2017
FRIEND of the RV-1
Eagle's Nest Mentor
Recipient of Wright Brothers "Master Pilot" Award
Reply With Quote
  #17  
Old 06-26-2018, 12:08 AM
czechsix's Avatar
czechsix czechsix is offline
 
Join Date: Mar 2006
Location: Spring Hill, KS
Posts: 336
Default

Oil canning isn't limited to the 14, I had a section in the aft fuselage of my -8A that would go 'thump' after shutdown as it relaxed post-flight. Here's an interesting read for anyone curious or concerned about oil canning in RVs:

http://www.vansairforce.com/communit...ad.php?t=36763

One thing to keep in mind is that the skin distortion in flight is hard to see on a painted airplane, so unless you leave it polished and the lighting is just right, you generally won't need to worry about it ruining that nice air-to-air photo you frame and hang on the wall. Look at the dozens of pics of painted RV-14s online and try to find any other example where the oil canning is visible either on ground or in flight...

Regarding the fix for the cracked rivets at the unsupported ends of the bottom skin stiffeners, I'm keenly interested in a fix from Vans (or I'll come up with something myself). The RV-8 is notorious for cracks in the exhaust ramp area and my -8A was no exception, but I was hoping to avoid cracking issues on the -14 airframe...
__________________
Mark Navratil
Spring Hill, KS
RV-8A N2D #80583 - built/flew/sold
RV-14A #140017 - wings complete, empacone in progress...

Last edited by czechsix : 06-26-2018 at 06:29 PM. Reason: minor wording
Reply With Quote
  #18  
Old 06-26-2018, 12:17 AM
czechsix's Avatar
czechsix czechsix is offline
 
Join Date: Mar 2006
Location: Spring Hill, KS
Posts: 336
Default

Quote:
Originally Posted by Tom Martin View Post
We have had some issues with the stiffeners in the flying RV14 that I built. Mel is correct that cracks may occur at the end of stiffeners that are not attached to the adjacent bulkhead. I first encountered this years ago when a friend installed stiffeners on the bottom of a RV6 to stop oil canning. After a short while cracks occurred on the bottom of the fuse. The same thing has happened on the RV14



This has occurred in the aft fuselage in ours, in two locations and is not the only aircraft that has experienced this. We passed this information on to Vans a few months ago and have been waiting for the engineers to come up with a fix.

This picture shows where they are on the lower aft fuselage. The cracks were stop drilled and you see safety wire sticking through just for reference as to where they are. The aircraft continues to fly, with no further cracks.

A fix will likely be some sort of bracket that will tie the stiffener to the bulkhead.


Tom, you mention knowing of other aircraft that have experienced cracks like those in your -14...are you referring specifically to other -14's or other RV's in general? I'm curious to know if cracks are appearing in other -14s, are they in the exact same location? It looks like yours cracked at the aft-most rivet in two of the stiffeners, but there are half a dozen J-channel stiffeners in the tailcone that are unsupported (no direct connection to a bulkhead) at the forward end...no issues there??
__________________
Mark Navratil
Spring Hill, KS
RV-8A N2D #80583 - built/flew/sold
RV-14A #140017 - wings complete, empacone in progress...
Reply With Quote
  #19  
Old 06-26-2018, 05:30 AM
Tom Martin Tom Martin is online now
 
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,423
Default

Mark, we were told that this had happened on other RV14s, both nose and tail wheel models. That is all the information that was supplied by Vanís.
__________________
Tom Martin RV1 pilot 4.6hours!
CPL & IFR rated
EVO F1 Rocket 1000 hours,
2010 SARL Rocket 100 race, average speed of 238.6 knots/274.6mph
RV4, RV7, RV10, two HRIIs and five F1 Rockets
RV14 Tail dragger

Fairlea Field
St.Thomas, Ontario Canada, CYQS
fairleafield@gmail.com
Reply With Quote
  #20  
Old 06-26-2018, 08:42 AM
shanecfi shanecfi is offline
 
Join Date: Jun 2016
Location: Macedonia, Ohio
Posts: 32
Default Oil Canning

So we just riveted the Aft Side Fuse Skin on this past weekend. I am wondering what direction to take here. We would have very easy access at this point, not having the Top Skins on. Making dimples might be a little challenging though.

My biggest fear is not knowing what I don't know. Therefore we have had strict adherence to the plans. I am not sure what path to take. I would hate to have to climb back inside the completed plane to add stiffeners. Thoughts?

Thanks
__________________
Shane Barker #140351
Commercial/Instrument
EAA/AOPA
RV-14a Emp. completed and stored
Wings Skins Attached
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:33 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.