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  #1  
Old 02-24-2012, 10:11 PM
Michael Burbidge Michael Burbidge is offline
 
Join Date: May 2006
Location: Sammamish, WA
Posts: 667
Default Big mistake mounting horizontal stab...

Friends,

If one hole can ruin an airplane, I might have done it. I am so discouraged!

A few nights ago I mounted my horizontal stabilizer. I thought everything went pretty smoothly and was pleased with my work. Well today I got looking at the holes that were drilled through the HS-908 attach angles into the F-714 deck and I discovered a big problem that I didn't know existed.

I noticed a slight notch on one side of one of the holes. When I got looking at it closer it was the entry point of the initial #40 hole I had drilled through the attach angle and into the deck below. But when I looked closer I saw that the #40 hole went off at a pretty sharp angle. I remember that I made that initial hole with a 6 inch bit and that I saw that the tip bent and went in at an angle. But I had no idea it bent that much. When I enlarged the hole to a #12, I made sure to straighten out the angle, and thought everything was fixed at that point. But as can be seen from the photos below the angle was more dramatic than I was aware of at the time. There's a photo from the top and from below.

I have no idea how I would go about fixing this. With some trouble I can remove the deck and replace the bottom angle, but I have no idea what I would need to do about the longeron, which obviously has a somewhat enlarged hole in it.

Thanks for any suggestions you might have,
Michael-



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  #2  
Old 02-24-2012, 10:28 PM
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airguy airguy is offline
 
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,319
Default

Your pictures are really good - I would send them to Vans on Monday and ask their opinion, but I'm betting they will tell you to drill it out to the next AN bolt size and build on. Worse mistakes than this have been made and corrected. The edge distance on the off-angle hole is into the direction of the web of the angle where you have excess material, this is the best of a bad situation.

I'm not a mechanical engineer, and I'm not telling not to panic - I'm just telling you not to panic until Vans says panic. At this stage in the build there are about seventeen hundred other items you can work on for a week until you get an answer.
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Last edited by airguy : 02-24-2012 at 10:32 PM.
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  #3  
Old 02-24-2012, 10:45 PM
alpinelakespilot2000 alpinelakespilot2000 is offline
 
Join Date: Jan 2005
Posts: 3,683
Default

Don't get too discouraged Michael! We've all had those moments when we've wondered if we've really messed something up. Let us know what Van's says.
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  #4  
Old 02-24-2012, 11:12 PM
Rupester Rupester is offline
 
Join Date: Dec 2005
Location: Mahomet, Illinois
Posts: 2,195
Default Also keep in mind ...

... The primary force on the HS is downward. It's not like there will be constant or significant loads pulling upward on that rr deck. I suspect drilling out to the next larger bolt size will work, but Vans can/will confirm or deny that.
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  #5  
Old 02-25-2012, 12:02 AM
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vmirv8bldr vmirv8bldr is offline
 
Join Date: Jun 2005
Location: Eastvale, CA
Posts: 378
Default I did the same thing. Twice.

Don't feel bad about it, I did the same thing only I did it twice. I noticed the mistake before riveting though and opted to replace all the affected parts. It was the most expensive mistake on the whole plane at about $200 +/-. I was later able to use the scrap parts elsewhere in the plane as stiffeners, etc.

I've learned two things building the plane:
1. I'm going to mess things up occasionally.
2. Anything I mess up, I can usually fix.
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  #6  
Old 02-25-2012, 08:07 AM
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jcaplins jcaplins is offline
 
Join Date: Feb 2006
Location: Davis, CA, USA
Posts: 544
Default fill-n-drill?

Would it be considered acceptable to fill the holes with JB-Weld and re-drill?
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  #7  
Old 02-25-2012, 08:26 AM
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flion flion is offline
 
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Location: Flagstaff, AZ
Posts: 2,672
Default

I was thinking along the same lines, though I'd still check with Van's. Since it's so very near the end of the longeron, you could fill the holes, back up the longeron with a 1/16" thick piece of aluminum stock, and redrill. Then use a slightly longer bolt through the redrlled hole and backing piece. I'd probably make the backing piece long enough that both bolt holes pierced it.
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  #8  
Old 02-25-2012, 08:42 AM
Rupester Rupester is offline
 
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Location: Mahomet, Illinois
Posts: 2,195
Default On the wall of my hangar ....

"Any mistake can be fixed. Sometimes with time, sometimes with money - - but usually both."
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  #9  
Old 02-25-2012, 09:39 AM
Tom Martin Tom Martin is offline
 
Join Date: Jan 2005
Location: Ontario, Canada
Posts: 1,564
Default

As suggested, call Van's. If it was my plane I would replace the underlying angle at the very least. I have some concerns that the additional hole in the main longeron weakens that primary structure. JB weld is a great product, and has it's uses, but all it is going to do here is make you feel better. It is not going to remove the stress point.
Van will likely tell you to replace the underlying angle and move on but do get their opinion and follow their advice.
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  #10  
Old 02-25-2012, 09:56 AM
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rocketbob rocketbob is offline
 
Join Date: Jun 2006
Location: 8I3
Posts: 3,647
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I've been around aircraft stuctures a long time and have seen quite a few repairs in the certified world and my opinion here is you really don't have much to worry about. There would have to be a tremendous negative-g force required to fail this joint as-is. For this joint to fail the longeron would have to bend out of the way, and angle attached to the bulkhead would have to be ripped from it. Going the other way (compression), all the bolt is doing is holding the HS in position with virtually no load. You could put a triangular reinforcement, a shim forward of the angle underneath the longeron, and bolt this in to add some more strength to this joint.
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