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  #1  
Old 06-09-2018, 03:06 PM
cdeerinck's Avatar
cdeerinck cdeerinck is offline
 
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Default Hoping

I am hoping this isn't the dreaded post that every builder fears.

I was doing the Horizontal Stabilizer Service Bulletin that Vans issued for the RV-8 about cracking. While it did say not to do it unless cracks were present on a flying plane, I thought it wise to do given that I wasn't flying or painted yet.

while drilling out a rivet in a difficult place, the drill slipped off of the rivet head and made a hold next to the rivet. By the time the rivet was removed, I ended up with a hole that looks like this:



I happen to be doing the Anti-Splat version of this, riveting in a Stainless plate between the two parts.

I used a slightly longer than normal rivet so that it could expand into the hole, and was apple to correctly set the rivet (i.e. it has the correct height and width at the shop end.

The real question to me is this: While it be ok like that? If not, how would I correct it? I am fearing the only solution might be to rebuild the tail, but I am really hoping that isn't the case.

If I drilled it larger to make a single hole, it would be about a -7 rivet, which I doubt I could set, especially in that constrained location.

Advice?
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  #2  
Old 06-09-2018, 03:17 PM
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Pat Hatch Pat Hatch is offline
 
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Location: Vero Beach, FL
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Default

I would look into using a Cherrymax rivet here. These are the structural rivets and they come in many sizes, oversize and under size. Get yourself to a nice rounded hole using a reamer if necessary and then try various sizes of rivets, find the right one, and pull it. As a last resort, and if edge distance allows, you could drill it out to a #8 or #10 structural screw. I would go the Cherrymax route if at all possible, though.
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  #3  
Old 06-09-2018, 03:44 PM
Freemasm Freemasm is offline
 
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Location: Orlando
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Default Another thought

Hi-loks, if you have the room. Stronger than any rivet could possibly be. Let us know what you do.

Edit = (going by memory, here) Hi-loks are essentially close tolerance bolts typically used in critical applications. Titanium studs are used in shear apps (like rivet application) and steel for tension applications where rivets generally shouldn’t be applied. They aren’t “blind” fasteners, per se’ but are torqued from one side which helps. The torque isn’t idiot proof but it’s close. The relief in the female fastener helps prevent “threads in bearing”. If there is sufficient edge distance and adequate spacing remaining after the hole is properly prepared, I wouldn’t have any real concerns. (I believe) An A&P can apply these fasteners to replace rivets at their discretion where riveting can’t be accomplished. A “standard” AN bolt application would not be adequate as the typical application tolerance isn’t tight enough for critical shear apps. All that said, I don’t know the details of this assembly and/or design. I read these posts to gain knowledge. Will certainly be following this to get smarter. As mentioned, let us know. Best of luck.

Last edited by Freemasm : 06-10-2018 at 07:57 AM. Reason: More info added
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  #4  
Old 06-09-2018, 08:14 PM
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az_gila az_gila is offline
 
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Question

Since it's a single hole - perhaps a #8, AN3 or AN4 bolt into a carefully reamed hole.

With Vans engineering concurrence of course.
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  #5  
Old 06-10-2018, 06:44 AM
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Walt Walt is offline
 
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Default

Quote:
Originally Posted by cdeerinck View Post
I am hoping this isn't the dreaded post that every builder fears.

I was doing the Horizontal Stabilizer Service Bulletin that Vans issued for the RV-8 about cracking. While it did say not to do it unless cracks were present on a flying plane, I thought it wise to do given that I wasn't flying or painted yet.

while drilling out a rivet in a difficult place, the drill slipped off of the rivet head and made a hold next to the rivet. By the time the rivet was removed, I ended up with a hole that looks like this:

I happen to be doing the Anti-Splat version of this, riveting in a Stainless plate between the two parts.

I used a slightly longer than normal rivet so that it could expand into the hole, and was apple to correctly set the rivet (i.e. it has the correct height and width at the shop end.

The real question to me is this: While it be ok like that? If not, how would I correct it? I am fearing the only solution might be to rebuild the tail, but I am really hoping that isn't the case.

If I drilled it larger to make a single hole, it would be about a -7 rivet, which I doubt I could set, especially in that constrained location.

Advice?
I would suggest you contact Van's with the details and pictures, they are the only ones that can truly evaluate/suggest a repair in this critical area.
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  #6  
Old 06-10-2018, 07:32 AM
rocketman1988 rocketman1988 is offline
 
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Default Hole

Cherry's are an option as well as a screw or bolt. When using a cherry, you really need to have a round hole as the rivet will not expand like a solid rivet to fill a less than perfect hole.

I would contact Van's and see what they say. Given adequate edge distance, make the hole round and secure with an appropriate sized fastener.
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  #7  
Old 06-10-2018, 10:15 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Default

Lots of advice................................

Just keep in mind that this is a primary structural load baring area which is exactly the reason that it was recommended to not install the modification unless there was evidence of cracks (high risk of doing more damage than the chance of a crack occurring).

Adding a screw as recommended might not be a fix unless it is done properly. A screw that installs as an easy slip in fit in a hole is not ideal because it is not baring the load in the same way that a rivet swelled tight in the hole would.

Cherry rivets are the same issue. The hole must be a precise fit for the rivet.

There is no fastener that will be acceptable unless you can properly convert your figure 8 hole into a round hole (and still have acceptable edge distance).
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  #8  
Old 06-11-2018, 07:41 AM
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JonJay JonJay is offline
 
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Default

Quote:
Originally Posted by Walt View Post
I would suggest you contact Van's with the details and pictures, they are the only ones that can truly evaluate/suggest a repair in this critical area.
Walt is correct. Although we are building an experimental, which you can do what you want in regard to modification, repair, etc.... try to follow an acceptable standard. This would be the airframe manual (plans and instructions for RVís), or AC-43-1b.
AC-43-1b gives many approved techniques for repairs. However, it specifically states the only acceptable repair to a Spar is that approved by the aircraft manufacturer (designer), i.e. Vans.
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  #9  
Old 06-11-2018, 01:12 PM
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cdeerinck cdeerinck is offline
 
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Default I asked

Thanks for the very good advice.

FYI, it was more than one hole, and there are some other issues like edge clearances (too close to an inside radius).

I didn't want to post the picture here, as it was my worst work (being when I first started) and is absolutely not representative of the rest of the plane.

It is absolutely understood how critical this area is. I made the mistake of thinking it was prudent to do this SB even though my plane wasn't flying yet, due to it not being painted yet, and I didn't want to have to repaint the tail if this became an issue down the road. Obviously, not a good decision in hindsight.

I did send the pictures off to Vans today, and asked if I can fix it, or need to build another stabilizer. I am certainly prepared to build another if they say so.

If they say it can be fixed, I will do that cautiously, but if the result is at all borderline, I am inclined to rebuild it anyway, because I think it will always bug me.

I will update this post when I get the reply from Vans.
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  #10  
Old 06-12-2018, 10:05 AM
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cdeerinck cdeerinck is offline
 
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Default Recommendation

FYI, Vans responded to me today that a new stabilizer is called for at this point.

They graciously added the following: "Don't feel bad about this. I've had to tell quite a few builders to build a new stabilizer. That SB is important but has a pretty high degree of difficulty."

I have to admit after having received that news, that I am somewhat relieved, as I would have always wondered if it would be ok.

My only concern now is that the alignment to the fuselage was already done, and will have to be redone on the new one. I hope there are not any steps in doing that which can't be reversed (i.e. the holes on the fuselage are already located).

If anyone has any words of wisdom along those lines, I am all ears.
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