R

rv8_builder

Active Member
We separated the F-811B-1 Stab Attach Bars as shown on DWG70 and noticed that the hole patterns differ.

The two holes at the top of each bar differ by 1/8" :confused:

F811B_1.JPG


F811B_2.JPG


The two holes at the top of each bar are used to attach the rear spar of the Horizontal Stabilizer so the offset doesn't make any sense.

Are these bars correct and if so what is the reason for the offset?
 
Thoughts.....

At first blush, it appears to me that the inconsistency in the hole pattern is a relative non-issue. After locating and aligning the horizontal stab, it will be drilled IN ASSEMBLY and as long as e.d. requirements are met, I do not see a problem....from my distant vantage point anyway. If you determine that e.d. will be marginal, you do have some latitude to work with. With the proper tooling, you can "pull" those 1/8" (.1250) pilot holes up or down as required before bringing the holes up to final full size 3/16" (.1875) diameter through the stabilizer. To enhance hole quality, it is always good practice to use a reamer for making the final full size pass through bolt holes. Bear in mind, I'm merely engaging in an "eyeball" engineering effort here and it wouldn't hurt a thing to contact Van's with the apparent discrepancy. Let us know what they say.

​
 
Mine were the same as yours but I did not notice until I mounted the stab:(
I ended up mounting the stab lower on the rear deck using thinner spacers...70 thou rings a bell (.063 stock does not work as the heads of the AD4 rivets at the forward end of the rear deck are about that) as I wanted as much edge distance as I could get for the stab rear attach holes.It all worked out but cause some head scratcing;)
 
Van's reply

I e-mailed Van's and received the following reply:

"Since the HS spar is to be matched drilled to the attach bars in assembly, there should be no problem using the bars as is"

So I guess I'll build on and make sure that edge distance requirements are met when I drill those holes.

Rick, what tooling could I use to "pull" those 1/8" pilot holes up or down before final drilling and reaming?
 
rv8_builder said:
.......Rick, what tooling could I use to "pull" those 1/8" pilot holes up or down before final drilling and reaming?
Click to expand...
Andre,

"Pulling" holes is an invaluable technique. Several weeks ago I applied the same principles to relocate a pilot hole on the rudder bottom to slightly improve e.d. for the Silverbullet steering link I was installing. Here is the tip I posted some time ago that gives a broad and general overview of a technique commonly used in aircraft production:

http://www.vansairforce.com/community/showthread.php?t=11769

P.S. In a pinch, you don't need to buy fancy tooling. Just some way to produce a good square hole in a thick piece of stock, preferably steel but aluminum will work, and the security of the "clamp up" is absolutely essential.

Good luck.
 
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Rick6a said:
Andre,

"Pulling" holes is an invaluable technique. Several weeks ago I applied the same principles to relocate a pilot hole on the rudder bottom to slightly improve e.d. for the Silverbullet steering link I was installing. Here is the tip I posted some time ago that gives a broad and general overview of a technique commonly used in aircraft production:

http://www.vansairforce.com/community/showthread.php?t=11769

P.S. In a pinch, you don't need to buy fancy tooling. Just some way to produce a good square hole in a thick piece of stock, preferably steel but aluminum will work, and the security of the "clamp up" is absolutely essential.

Good luck.
Click to expand...

Thanks for the help Rick, I'll definitely use your advice if I need to "pull" those holes. :)
 
Hey Andre,
My dimension 'A' is 1.5625 inches, and the center distance to the next hole is 1.625 inches.

Hope that helps.
Chris
 
Of course...-both- of mine could be wrong. Take care when you drill. I will certainly check, since I dont understand why the holes have been drilled inconsistantly between our two kits.
 
Dimensions

chepburn said:
Hey Andre,
My dimension 'A' is 1.5625 inches, and the center distance to the next hole is 1.625 inches.

Hope that helps.
Chris
Click to expand...

Thanks for the dimensions Chris, I really appreciate your help :D

chepburn said:
Of course...-both- of mine could be wrong. Take care when you drill. I will certainly check, since I dont understand why the holes have been drilled inconsistantly between our two kits.
Click to expand...

Although I doubt that both your bars are wrong, I'll definitely take care when drilling mine.
 
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