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Math problem?

OrenAir

Active Member
In the horizontal stab attach bar, page 10-04, I'm having math trouble.

The top left figure says the piece is 5 and 13/16 wide. The bottom says it's the sum of 1 and 3/16, 1 and 1/4, 1, 1 and 1/4, and 1 and 3/16. I add those up and get 5 and 14/16.

Millimeters don't work for me either. Top view says 147.6 mm. Bottom says sum of 29.8, 31.8, 25.3, 31.8 and 29.8. My calculator says that's 148.5.

What mistake did I make? Is it the difference because the back side is angled, and the top is measuring the back while the bottom is measuring the front?
 
I think your math is correct but it's pretty hard to be that precise when making this part. I started from the center and used the template as drawn as a guide. (comparing my marks on part to drawing as well as the part as I took material away to get to the final version). It came out "close enough".

You're talking about 1/32" on each side of center difference on a hand made part. If you could get it that precise, I'd say err on the side of caution and spot Van's the 1/32" - make the top of the bar 1/32" wider on each side.
 
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It rivets to F-01411E and F-01414 which rivets to the main side longeron (page 10-27 figure 1). The "3-sided notch" or cut out is so that the bolts that hold on the elevator bearing (page 8-03 figure 2) will clear.

If the piece is too long, it will stick out over the F-01414 deck. Not a big deal as you'd never see it. However, the 5 13/16 measurement works perfectly. If you're +/- 1/32", you'll be fine.
 
All the rivet holes are already in the piece. Clearance is not that critical (having already built this part and test fitted the HS) - if within 1/32" no issue at all.
 
Slightly off topic, but still related. I am not a fan of fractional dimensions. It's easier to make math mistakes. I wish Vans would stop using them and go to decimal.

I have a friend who occasionally helps on my build who also happens to be a machinist with his own milling machine. He is going to put the F-01411D on his milling machine and CNC machine it down to final dimensions.
 
To save weight

Is the notch out of F-01411D to save weight or for clearance from some part above?

It is a pain to cut out. I've already messed up one part. Ordering another.
 
The two pieces that are rudder stops should not be cut to final size until the Rudder is attached and rigged.

You will likely find you need to remake them otherwise. This was the case on my 9A and Rocket. Too short and the elevator will hit the rudder (wind damage). Too long and you won't get enough rudder throw. Need to be fine tuned.

V
 
Is the notch out of F-01411D to save weight or for clearance from some part above?

It is a pain to cut out. I've already messed up one part. Ordering another.

It provides clearance for the elevator push pull tube.

When trying the second time cutting out the part, try drilling a number 30 hole in each corner and then make the straight cuts to the tangent point edge of the hole.
 
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