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RV-7A Construction Log
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Date:  11-24-2008
Number of Hours:  1.00
Manual Reference:  
Brief Description:  Tank Assy - Flop Tube Installation 4 (Anti Turn)

When I tightened the nut onto the elbow fitting that attaches to the flop tube, it became obviouse that the elbow fitting was not tight enough in the hole to prevent it from moving and I started thinking about what will happen when I try to tighten a fuel line onto it someday. So I started writing the Vans Airforce and other builders to see if anyone else had considered that an anti-turn bracket is needed for the flop tube. A couple people said yes, and showed me their photos. They also said the Proseal is strong enough to hold it from turning when you put the fuel line on because it is only tightened about 10 ft-lbs because it is a flare fitting. I decided to add the anti-turn brackets just to be safe, because knowing my luck it will turn later when I don't want it to.

I made these two little brackets from T-715 Anti Rotation brackets, by just cutting the tops off and sanding out the insides. I can install it on the right tank rib easily because I haven't installed the rib yet. It was difficult to install it on the left rib which is already on the tank, but nothing had to be removed except a little Proseal.

I used pulled rivets on the rib already installed with flop tube and Universal rivets for the tank that didn't yet have its inboard rib installed. I installed the bracket after the angle bracket but before the flop tube.

Here is email note from Van's on this:
12/01/2008 08:39 AM
To Steve
Subject
Re: flop tube elbow turning

Steven,

If you seal the elbow on the flop tube and then it moves just a little when you
attach the fuel line to the fuselage, the seal will break. So an antirotation
bracket is advisable. When you tighten the nut on the outside make sure
that the elbow is tight against the bracket and there will be no chance of it
moving later.

Bruce Reynolds
brucer@vansaircraft.com
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Anti Turn Bracket for Flop Tube

Anti Turn Bracket for Flop Tube

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Anit Turn Bracket Installed

Anit Turn Bracket Installed

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Outside view of rivets for anti turn bracket

Outside view of rivets for anti turn bracket

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