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  #1  
Old 08-19-2019, 02:43 PM
gjslutz gjslutz is offline
 
Join Date: Dec 2011
Location: Beach City, Ohio
Posts: 30
Exclamation RV-4 firewall issues

I had the motor mount break. Looking for an expert to look at to tell me what other issues I should look at.

I have another mew mount sitting here, it is the newer long gear mount. The center two mount holes do not line up.

Do I need to have the firewall replaced, as it has some issues, have photos.

Early kit number, has been a great A/C for 1,000 hours. Would like to get it back in the air.

I'm in N.E. Ohio.

Gary

33zero-236-5041 or cell / call or text 33zero-704- 5686
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  #2  
Old 08-19-2019, 03:40 PM
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Flyhud Flyhud is offline
 
Join Date: Jul 2018
Location: Burleson, TX
Posts: 28
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Gary,

I had the same issues with mine. I found cracks in the motor mount around the lower clusters on both sides, also had some cracks and deformation on the lower corners of the firewall. It became one of those deals where I decided that since I had already had the engine off and I was replacing the engine mount I might as well replace the lower firewall, and since I had the firewall off I went ahead and added the RV-8 style gussets that will hopefully mitigate future cracks in the lower firewall corners. Although it’s a fair amount of work I am happy that I dug a little deeper, as it allowed me to really get a good look at all of the weldments. Because I had the lower firewall removed, I also found that one of the center mount brackets/angles had cracks radiating from the mount hole and also one of the stringers that goes from the spar to the center mount was slightly bent. I replaced both of the center mount brackets and the stringer which was relatively easy. As a result of this endeavor, I have complete peace of mind that there is no hidden damage in this critical structure. As I recall the lower firewall was around 50 bucks from Vans, it fit well and required very little in the way of trimming and fitting.

With all of that being said, if the only issue you have is a bad mount and some cracking on lower firewall corners you can stop drill and seal/patch the cracks in the firewall. There are some loads on the firewall, however, the cracking is generally considered to be acceptable and shouldn’t affect the load bearing capabilities of the primary structure.

The center mount holes that do not align can be re-drilled to match, Vans has a procedure and the hardware call outs for doing this. This leaves the center mount with two holes.

Tom
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RV-4/160hp/O-320/CS/G3X

Last edited by Flyhud : 08-19-2019 at 03:55 PM.
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  #3  
Old 08-19-2019, 05:54 PM
gjslutz gjslutz is offline
 
Join Date: Dec 2011
Location: Beach City, Ohio
Posts: 30
Default Firewall

Flyhud Thanks,

As I did not build an A/C, my A&P requested that I get someone to look it over. He has not worked on any RV's.

I hope to find some close to look it over. I have several speed mods and work the RV a little harder than most.

Gary
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  #4  
Old 08-19-2019, 06:30 PM
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smokyray smokyray is offline
 
Join Date: Jan 2005
Location: TX32
Posts: 1,828
Default The Cure

Quote:
Originally Posted by gjslutz View Post
Flyhud Thanks,

As I did not build an A/C, my A&P requested that I get someone to look it over. He has not worked on any RV's.

I hope to find some close to look it over. I have several speed mods and work the RV a little harder than most.

Gary
Gary,
I have performed this chore several times on my Four and my HR2.
I built a “low workbench” 3 ft above the shop floor 15’x5’ with 2x6’ legs at each corner and 1 in the center with 1” plywood top and sides. I placed tires across the top and lifted my RV by the engine mount, slid the table under the wing and lowered it gently to the tires until supported. You’ll need to tie down the tailwheel as well. You can now unbolt the mount and remove it. While removed inspect the lower longerons below the rudder pedals, firewall for cracks, (remember it’s not structural but the longerons and fuselage skin are) and general condition.
Install new mount, consider replacing mount bolts.

Email me offline if you get in a pinch!
V/R
Smokey

smokyray@rocketmail.com
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  #5  
Old 08-19-2019, 08:05 PM
gjslutz gjslutz is offline
 
Join Date: Dec 2011
Location: Beach City, Ohio
Posts: 30
Default Firewall

Smokey,

Three years ago I replaced the lord mounts and did a good look at the motor mount then. It all looked good at that point, I could have missed something at that point though. I was not aware of the mount issue then, and due to other things I hardly flew the RV the last few years.

When this broken mount showed up, it came out in parts. The top of the firewall foot wells were broken on the top corners. and around the bottom mount bolts.

I could find no other issues on the air frame. As I said I have worked my lighter A/C, but not like my aerobatic A/C I have had over the years. I even removed the inverted oil system about six years ago, it flew like a pig inverted, and I was trying to lighten it up.

Gary
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  #6  
Old 08-19-2019, 09:15 PM
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Flyhud Flyhud is offline
 
Join Date: Jul 2018
Location: Burleson, TX
Posts: 28
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Gary,

“When this broken mount showed up, it came out in parts. The top of the firewall foot wells were broken on the top corners. and around the bottom mount bolts”

Sounds like your firewall is pretty beat up, if it were me I would start drilling out rivets and ordering parts. The fact that the engine mount came out in chunks is also concerning, I would take a close look at all of the structure behind the firewall as well. This especially if you are doing a lot of acro. This analysis is based solely on your description, I would be happy to take a look at your pics and provide you a more informed opinion.

Tom
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  #7  
Old 08-21-2019, 07:02 AM
gjslutz gjslutz is offline
 
Join Date: Dec 2011
Location: Beach City, Ohio
Posts: 30
Default Firewall issues

When I found the photos of the corner beef-ups, I found out mine has those and all is well there.

I purchased my -4 in Seattle, WA. Oct 16 2003. At times it shared our hanger with our S2S & S1S Pitts then an 10-200 Ultimate.

My Neighbor is an A&P and we have done the inspections. He has requested me to find someone who has experience with RV firewall cracks to look at mine.

I'm just south of KCAK @ 2D7, and would like to find someone to look at my firewall issues.

If repairs are needed, would like to find someone to help with this.

Gary
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  #8  
Old 08-21-2019, 07:21 AM
gjslutz gjslutz is offline
 
Join Date: Dec 2011
Location: Beach City, Ohio
Posts: 30
Default Firewall issues

When I found the photos of the corner beef-ups, I found out mine has those and all is well there.

I purchased my -4 in Seattle, WA. Oct 16 2003. and flew back to: 2D7

My Neighbor is an A&P and we have done the inspections. He has requested me to find someone who has experience with RV firewall cracks to look at mine.

I'm just south of KCAK @ 2D7, and would like to find someone to look at my firewall issues.

If repairs are needed, would like to find someone to help with this.

Gary

I received the new mount and long gear, now just need to get all back together. I'm quite lucky to have some friends that can handle this.

Gary

Last edited by gjslutz : 09-02-2019 at 06:26 PM. Reason: repair in progress
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  #9  
Old 08-21-2019, 10:38 AM
SHIPCHIEF SHIPCHIEF is offline
 
Join Date: Mar 2008
Location: Seattle
Posts: 1,410
Default

I just made a similar repair to my wife's RV-4. The mount was cracked in several places and the gear toed out. The tires had quickly gone bald, leaving black marks on the hangar floor. It took a lot of effort to push the plane on concrete.
The inner two mounts which support the upper end of the landing gear sockets were pulled forward. The large angle aluminum brackets for the mount bolts had sheared the rivets to the deep longerons (keels) and the firewall rivets were pulled through in the toe box. (The 2 vertical rows between the rudder pedals)
The firewall was pretty sad looking, but in order to keep the job on track I elected to keep it and forged ahead. The 4 corner longeron weldaments are the newer type and still good.
Russ McCutcheon makes weldements for VANs, and rebuilt Marilyn's mount in 3 days. Russ was great to work with, and will give you a tour of his shop, plus educate you on the repair process. He is a dedicated craftsman. The rebuilt mount fit perfectly.
All the bad rivets were drilled out #20 and replaced with AN525-832R screws which have un-threaded shanks for the grip area. These are low profile washer head screws which are substantially stronger than a -4 rivet. I was able to re-install the angle brackets and pull the firewall back into place using jet-nuts or lock nuts. The firewall pulled back into place rather well, although cracks remain and are sealed.
While the engine was off, I removed the sump & gearcase for cleaning & inspection. I also replaced the crankshaft bolt. I installed rebuilt mags & plugs, fuel pump & carburetor. Additionally, I welded up a hole in the exhaust caused by rubbing, and replaced the missing exhaust support strut that caused the leak.
The tires and tubes were replaced and the brake calipers rebuilt. The left wheel pant inner mount plate was renewed. The wheel bearings were repacked and the seals inspected.
Once disassembly starts, 'Discovery' begins...and the work piles up!
Marilyn is the 9th owner of this plane, which has about 1500 airframe hours. It took about 3 weeks to get her back in the air.
__________________
Scott Emery
http://gallery.eaa326.org/v/members/semery/
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is nothing-absolute nothing-half so much worth doing as simply messing around with Aeroplanes
(with apologies to Ratty)
2019
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  #10  
Old 08-21-2019, 10:54 AM
SHIPCHIEF SHIPCHIEF is offline
 
Join Date: Mar 2008
Location: Seattle
Posts: 1,410
Default

I should add that I used an engine hoist to remove the engine, then a come-a-long from a rafter attached to the roll-bar to support the airframe off the ground. I made a cradle somewhat like Smokey did.
A good feature of the RV-4 is the removable cowl over the instrument panel.
One can reach in from the top to repair the gear mount/longeron, service the rudder pedals, & brake master cylinders, upgrade the panel or replace the battery with very good access and little discomfort.
This is another one of those features that make an RV-4 such an outstanding aircraft, and I say this as a builder/owner of an RV-8 (which is great in it's own way).
__________________
Scott Emery
http://gallery.eaa326.org/v/members/semery/
EAA 668340, chapter 326 & IAC chapter 67
RV-8 N89SE first flight 12/26/2013
Yak55M, and the wife has an RV-4
There is nothing-absolute nothing-half so much worth doing as simply messing around with Aeroplanes
(with apologies to Ratty)
2019
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