Rats!! Edge distance on HS-710 not met!?

MikeJ 7A · #1 02-02-2007, 11:41 PM

Drilling the last hole through HS-405(rib) to HS-702(forward spar) to HS-710.
I was using the pilot hole in HS-405 rib, but either that was a bit off or my drill was a bit angled or both. In any case, my edge clearance on the HS-710 angle stock is less than 2xDia. This takes a AD4 rivet (dia. 0.125) so the center of the hole at 2D should be at least 0.250 from the edge and the lip of the hole should be at least 0.188 from the edge. This hole is .053 too close, argh!

I'll call Van's on Monday, but probably will need to buy all three parts new for my first "redo".
I'm assuming that the 2D edge clearance is a MUST and does not depend on the thickness of the material? (HS-710 is not sheet metal, does this help me?)
Mike

RV7Factory · #2 02-02-2007, 11:54 PM

Mike,

FWIW, I did a similar thing on the same part. I called Van's and they wouldn't comment on whether or not the edge distance was acceptable, but instead they told me only this... "That part is structural".

It was an easy decision for me, I replaced it.

Good luck!

TJoyner · #3 02-03-2007, 08:26 AM

I did the same thing... I called Van's and the reply was "you can get away with it, barely but safely..." I realized it was still keeping me up at night so I just bought new parts.

MikeJ 7A · #4 02-03-2007, 08:56 AM

Well, I checked Van's site and the cost to replace the three parts was $50 so I just went ahead and ordered them. Small price for peace of mind and a good reminder to me to "Measure Twice, Drill Once".

jcoloccia · #5 02-03-2007, 09:16 AM

I used the "TLAR" method and it comes out perfect every time.

http://www.ballofshame.com/flying/rv...g/20051106.php

osxuser · #6 02-03-2007, 10:32 AM

I thought this part of the plans was horrible, and vague at best as well. I has to "adjust" a little around here, but I think I drilled by eyeing the edge distance from the front to the back, that way, It would end up aligned with good edge distance on the angle... anyway hindsight. In my case it's 20/80. (Bad memory

)

sprucemoose · #7 02-03-2007, 10:49 AM

The 2X edge distance is a good rule of thumb, however it is overly conservative. For those really close situations, you should consult the Mil-Spec on riveting to get the true story.

http://home.earthlink.net/~gilalex/

The minimum edge distance for a 1/8 dimpled or straight hole is .219, not .250. Now, in your case you're still over the limit, and I think you did the right thing in replacing. However, you should print out this Mil-Spec and keep it in your shop. Many thousands of perfectly acceptable rivets have been drilled out over the years because they didn't meet the 2X rule.

MikeJ 7A · #8 02-03-2007, 11:24 AM

Thanks for the insights and great info. John C, wish I'd seen your site before I drilled, lol! That area bugged the heck out of me when I was doing it and I felt there was a "better way". The newbie in me kept saying, "just do it like it says to".

Mike

frankh · #9 02-03-2007, 12:08 PM

I only replaced the angle though, I rivetted a repair plate over the metal underneath and added a couple of extra rivets to make the part stronger than the original.

Like many of us who did this it was keeping me up at night so for $20 it was a no brainer and took very little time.

It was the only mistake like this I made on the whole airframe.

Frank

7a

jmitchell · #10 02-04-2007, 05:57 AM

I also made this same error. (I don't feel so bad now that I see I am not alone.)

I ordered a replacement Angle and rib, but after speaking to Vans tech support, I realized I only really needed to replace the angle piece as it's "structural" and the rib would be fine with an "undocumented lightening hole".

I decided not to replace the rib for the following reasons; this rib is not pre-punched along the flange and my skin is already match drilled and dimpled to the original rib. If I tried to install a brand new rib it would not fit properly for the back drilling process, because of the skin dimples and besides, I would never try to back drill a dimpled hole to an un-drilled rib flange. This would surely ruin the skin and likely result in a poorly fitting rib. So retained the original rib.

I suspect the problem occurred by me using a 12" drill bit which is too long and places the drill on the Aft spar making it impossible to drill the hole at a right angle to the work.

So it had to be placed at a slight angle and resulted in the exit hole being closer to the edge than is acceptable. I ordered the proper tool (a 90 angle drill) and will redo those holes once it arrives.