Edge distance dilemma - long post

[lostpilot28]

I sent the following e-mail & accompanying picture to Van's Support guys several months ago:

Hello,
I've begun the section where I mount the Horizontal Stab to the fuselage and I have an "edge distance" question. My QB seemed to have pretty short sections of angle underneath the part of the fuselage where the HS-710/714 gets bolted. Basically, I followed the directions, measure a few times, then drilled the 4 holes. They look great from the top, but as the attached pictures show, the outer bolts are a little close to the edge of the angle.

Is this OK? Should I replace the angle and start over?

I ended up calling them about it the next day since I didn't get a quick reply and they said that they brought it up to their Engineer and showed him the picture. He said that since there isn't much side loading happening back there that this was not a problem...don't worry about it. But, if I really wanted to do something to "feel better" I could either replace the angle (not recommended because of messing up the rivet holes when drilling the first ones out), or I could add a piece of aluminum to the top of the deck plate and rivet it to the longeron in place of the thick aluminum spacer between the deck plate and HS.

Both sides of this angle are short...I'd say about 1 bolt diameter from the center of the hole. This is a Quickbuild and it's apparent they didn't know that the angle needed to go all the way to the inboard edge of the longeron. So, the shortness of the angle is the root cause of the edge distance problem. Again, Van's said that this was OK, and that most loads would be downward anyway and wouldn't pose a problem.

A friend of mine has the same problem on one side with the same piece of angle. I believe the other side is OK. Is there anyone else out there that's seeing this problem on their kits? Particulary the QB?

A suggestion that seemed viable was to use a thin piece of steel (.040") and make a 3 inch long plate that sits under the nut of these 2 bolts. It would provide side-bearing strength to prevent the AN3 bolt from pulling out of the angle with the edge distance problem. It seems to me that for the bolt to pull out of the edge of the angle (even though it's very thin), the other side of the angle would have to push in, which doesn't seem likely.

Any of you structural engineers out there have some constructive feedback? Would the steel plate help? Should I just leave it alone?

Thanks!

[AlexPeterson]

Sonny, fix it in one way or another, or it will just keep bugging you.

I think your idea of a bar on the nut side (the side we see in the photo) is good. I'd use aluminum, .125" like the angle, and maybe drill out the one rivet which is just to the right of the open bolt hole in the picture. Then put a third bolt there, or near that drilled out rivet. That way you would have two solid bolts holding the bar to the existing angle. Then move on!

[TSwezey]

You could also just put an aluminum doubler on there. Just cut a small section of the 1/8" aluminum out of a piece of angle and do what you were going to do with the steel. You could drill out a few of the rivets to hold this doubler in place.

edit:Alex you obviously type faster than me! Same solution!

[SvingenB]

The best advice is to follow Van's advice. There is something fundamentally wrong with "fixing" a problem in an aluminum construction with steel. Steel is a very different metal.

[lostpilot28]

Originally Posted by SvingenB

The best advice is to follow Van's advice. There is something fundamentally wrong with "fixing" a problem in an aluminum construction with steel. Steel is a very different metal.

Well, I would tend to agree with that except the only use that this small piece of steel would be doing is preventing the outer bolt from moving outward to the point of breaking through the edge of the aluminum angle. I suppose I could do the same thing with a thick piece of alumimum and use longer bolts...I don't think overlaying another piece of angle will work because the holes would be too close to the radius and the nut wouldn't sit flush.

[az_gila]

Originally Posted by SvingenB

The best advice is to follow Van's advice. There is something fundamentally wrong with "fixing" a problem in an aluminum construction with steel. Steel is a very different metal.

Yeah... the bolt is steel and the angle is aluminum... it's a mixed bag already! No fundemental defect...

gil A

[whd721]

I had the same issue on the RV9 I am working on. The first owner managed to drill the outside HS bolt hole too close to both edges. The longeron and the angle under (F710B on the RV9) the longeron. After removing the Aft Deck I replaced the F710B, but could not erase the hole in the longeron edge.
The solution I worked out with Vans was to extend the 1/8" shim under the HS attach angle fore and aft two rivets. The shim was roughly a rectangle shape under the HS attach angle, now it is a 5 1/4" long shim on the outside (covering four rivets and both bolts ), the original shim length on the inside with connecting lines for a rough trapezoidal shape.
The 1/8" angle longeron with an extra hole is compensated for by an additional 1/8" shim spanning the hole.

[GAHco]

If the load pattern is to put the bolt in tension put a washer and nut on it and your good.

If it is in shear do what you need to grab more edge distance.

But what I suspect is that it is in mostly a combination load and that is where neither one of us knows the percentage of possible tension vs shear.

Under normal flight loads this would not scare me, but.........

These planes are not built to handle just normal flight loads

Applying an appropriate 2024 aluminum strap of the same thickness, about 4 to 6 inches long and riveted to the same piece using existing rivet holes and then drilling the bolt hole very carefully from the top so the new strap has all the right edge distances is a repair I would believe in.

I have seen many posts on this issue, it seems to be a common problem.
Once my fuselag is done I will take this part slow and careful.

But beware, I aint no engineer, heck I don't even know how to drive a train.

[SvingenB]

Originally Posted by lostpilot28

Well, I would tend to agree with that except the only use that this small piece of steel would be doing is preventing the outer bolt from moving outward to the point of breaking through the edge of the aluminum angle. I suppose I could do the same thing with a thick piece of alumimum and use longer bolts...I don't think overlaying another piece of angle will work because the holes would be too close to the radius and the nut wouldn't sit flush.

The problem is that steel is a much stronger material. It doesn't stretch and flex nearly as much as aluminum. Adding a ad hoc steel member in there makes a discontinuity in the construction regardless of thickness, size etc. Unless you know exactly what you are doing, discontinuities will create stresses rather than releive stresses. On top of this the chemical properties of steel is also very different. In your case it probably will not cause any harm, but...

The engineer at Van's is the one most likely to give you the best answer, since he knows the construction in and out. He has given you 3 options; do nothing, replace the angle, or add another plate as reinforcement (on the other side?). Wouldn't it be best to follow one of these advices?

[SvingenB]

Originally Posted by az_gila

Yeah... the bolt is steel and the angle is aluminum... it's a mixed bag already! No fundemental defect...

gil A

A bolt has a very specific purpose and is a part of the design. An ad hoc "feel good" steel plate is not. That is the difference.