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  #1  
Old 11-13-2012, 09:34 PM
J Twilbeck's Avatar
J Twilbeck J Twilbeck is offline
 
Join Date: Oct 2012
Location: Huntsville AL
Posts: 145
Default Firewall Brackets Edge Distance Fix

I thought I would share this in case anyone else ran into the same problem.
I had some edge distance issues with my upper firewall brackets (WD-1002). They are match drilled through the frames from above and if they are like mine don't line up well enough to leave any reasonable edge distance with the rivets. I even tried using a clamp to pull the tabs into place, but it wasn't enough. So here is how I addressed the problem.


This is the upper left hand firewall bracket (WD-1002). View looking up.
The bracket is made from 0.063" 4130 steel.


Here is a closer view of the holes. View looking forward.
As you can see the edge distance reduces to almost nothing in the aft holes.
Note a total of 9 rivets in the upper tab of the bracket.


I traced the shape of the part using some lexan and marked a cut line just forward of the fourth hole.


Picture of the WD-1002 upper flange after the cut. I used other pieces of steel to shield the existing parts while cutting to prevent any accidental strikes from the cutting wheel.


The new parts. I don't won't to call them repair parts, but I guess that's what they are.
Starting on the left: upper spacer, aft spacer, splice strap.
Upper spacer is 0.125" 6061-T6 shaped to taper down to 0.063" on the outboard side
Aft spacer and splice strap are 0.063" 4130 steel (same material as the WD-1002 Bracket).


The spacers and strap celecoed in place. The upper spacer is sitting under the primer green firewall stiffener and above the cut upper tab of the firewall bracket. The aft spacer is sitting just aft of the cut. and the splice is on the bottom spanning the entire length.


With this view you can see the 4 new holes in the firewall stiffener web inboard from the existing line. These four new holes go through the upper spacer, upper firewall bracket tab, and the splice. These holes are important as they allow the upper firewall bracket tab to have 9 rivets as was originally designed (now with better edge distance), replacing the 4 holes removed. Equally important is that the new holes go into the spice to carry the load into the aft holes as was originally designed.


View looking down with rivets installed.


Ignore the sloppy green primer. View looking up and forward. You can see the new 4 inboard holes making a total of 9 rivets shared by the tab and the splice. The splice strap actually extends beyond what the original tab did picking up 5 additional rivets aft of the original. The splice, being made of the same type of material, can carry the load into the existing structure as intended. The "repair" or "redesign" is actually stronger than the original with the improved edge distance and additional aft rivets.
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Last edited by J Twilbeck : 11-13-2012 at 09:54 PM.
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  #2  
Old 11-13-2012, 10:04 PM
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aturner aturner is offline
 
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Location: Clarion, Pennsylvania
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I had the same problem Justin. I could pull the backet into alignment with the U-channel only by putting a tremendous amount of clamping force on the assembly. Obviously, that amount of preloading isn't acceptable. I contacted Vans and they were kind enough to send me two new upper weldments. The new weldments didn't align well either (actually, I think one did and one did not), and so I played with them for a while and finally figured out that the root problem is that when the weldments are constructed the forward flange tends to warp with a convex front surface. When it is rivited to the firewall, the warp pulls the aft arms out of proper alignment with the U-channel. I don't recall how I flattened the warp (probably involved whacking it with a hammer), but I bent it flat and it fit perfectly. So, this is one "gotcha" item that builders should be careful with. Set the weldment on a table, forward face down, and make sure it doesn't rock back and forth. If it does, fix it. And watch the edge distance when match drilling from the U-channel into the weldment.
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Last edited by aturner : 11-13-2012 at 10:07 PM.
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  #3  
Old 11-13-2012, 10:16 PM
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9GT 9GT is offline
 
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I had no problems with mine.
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  #4  
Old 11-14-2012, 08:49 AM
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J Twilbeck J Twilbeck is offline
 
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Location: Huntsville AL
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Andy,

I'm glad to hear someone else had this problem, not for you but for my sake at least. I did a search on the forum and it came up empty. When I called Van's they acted like it was common, but didn't offer any real answer to fix the problem. So I engineered up a solution.

Thanks,
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  #5  
Old 11-14-2012, 12:43 PM
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aturner aturner is offline
 
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Several threads in the archives of the Matronics RV-10 list pertaining to the issue, here is one:
http://forums.matronics.com/viewtopi...ghlight=wd1002
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  #6  
Old 09-27-2016, 10:08 PM
KatanaPilot KatanaPilot is offline
 
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Location: Locust Grove, GA
Posts: 752
Default Should have checked here first

Today at Synergy we drilled through the U channels (blind) into the firewall brackets with everything in place, aligned and clecoed per the construction manual.

Upon disassembly we found that the aft most holes in both of the left side brackets had come out of the side of the bracket and the upper right side edge distance is less than comfort level.

So I drove to Van's this afternoon and bought three of the four brackets. Tomorrow we will remove the damaged brackets and hope the new ones align better. At least we will know to check edge distance before we drill.

It appears that applying an excessive amount of force to these brackets to get them to align properly is needed - but it seems like a really bad idea.

A strongly worded note in the construction drawings is warranted in my opinion. Too much variability in these weldments not to caution us before drilling.
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Locust Grove, GA
DA20-A1 "Princess Amelia" - gone home to Amelia Island
RV-7A Phase 2 (Honored to be Van's "Miss July" 2021)
RV-10 under construction at Synergy Air South
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  #7  
Old 09-28-2016, 03:02 AM
leok leok is offline
 
Join Date: Apr 2013
Location: Clarkston, MI
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Same problem on the left upper bracket. I ended up purchasing a new bracket as well. The new one didn't fit well, but I was able to make adjustments (read a good whack or two with a hammer ) to get things lined up.

I agree the plans need a strongly worded warning. With everything else fitting so well, it is easy to miss the alignment problem on these until it is too late.
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  #8  
Old 10-02-2016, 01:04 PM
KatanaPilot KatanaPilot is offline
 
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Location: Locust Grove, GA
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Van's suggestion was to clamp and pull the tabs into alignment. My concerns of stressing the brackets and firewall were met with a "we haven't had any problems with it". Not exactly a glowing recommendation of the method but I understand their position.

My suggestion of a note in the construction drawings was met with an equally satisfying "I will suggest that to engineering and see if they want to do it, but don't expect anything".

I am new to homebuilding and to dealing with Van's so I have little experience to be in a position to criticize. I know I'm not the first person to have this issue and a note on the drawings is neither difficult to implement nor an admission of error on Van's part. Sharing of "tribal knowledge" is necessary and appreciated.
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Locust Grove, GA
DA20-A1 "Princess Amelia" - gone home to Amelia Island
RV-7A Phase 2 (Honored to be Van's "Miss July" 2021)
RV-10 under construction at Synergy Air South
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  #9  
Old 10-02-2016, 04:56 PM
David Paule David Paule is offline
 
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Location: Boulder, CO
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On my RV-3B, there's a similar situation. I routed down a wider piece of angle so that I could leave wider bosses where I thought that they'd be useful. Here's a photo of that near the aft end of the fuselage:



I described the process here.

Dave
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