Fuel Line Interference with Gear Weldments

[Paul Johnson]

I'm getting ready to fit up the fuel lines in the fuselage of my -7A. I found that if they are routed per Vans instructions along the F-704 bulkhead, going through the bottom holes of the F-782 and F-783 cover support ribs, they interfere with the inboard diagonal braces of the landing gear weldments. The obvious solution seems to be to route the fuel lines through the upper holes of the cover support ribs, but it' not clear whether that might lead to other problems later. Has anyone else run into this situation?

Paul

 

[TX7A]

Paul,

I'm almost where you are in assembly. I, too had the same concerns.
Here's some pics from Bobby Hester's site that may be helpful. (Thanks Bobby). About half way down each link....

http://members.hopkinsville.net/bhester/FuseAssyPg2.htm
http://members.hopkinsville.net/bhester/FuseAssyPg3.htm

Here's some more pics from Brian Meyette's site (Thanks Brian)
(On the fuse link, June 4)

http://brian76.mystarband.net/RV-7Ahome.htm

Sam
7A@ABI

 

[brian]

new link

the new URL for the link mentioned above is this:

http://www.meyette.us/June03fuse.htm#jun12

see also:

http://www.meyette.us/FuselageNov03.htm

http://www.meyette.us/FuselageDec03.htm

 

[Bob Axsom]

Routing is not that critical

I don't know how the RV-7 drawings show the routing of the fuel lines but your main concern should be routing the fuel lines for function not conformance to some draftsman's idea of what the installation looks like. My routing is nothing like the pencil concept on the RV-6 drawing/instruction set. Try to keep the fuel flowing down hill, avoid insecure contact where avoidable, install chaffing protection where appropriate, clamp to secure in place, have the auxiliary pump below the full tank level, don't restrict the cross section of the tube/fuel line (3/8" on my plane), install a flexible hose between the airframe (firewall) and the relative vibrating engine installation (engine driven fuel pump) and you should be OK.

Bob Axsom

 

[lostpilot28]

Or, take the easy way out and install stainless braided flexible fuel line from Pegasus Auto Racing! Much easier! And only cost around $50

 

[Rupester]

I ran my 9A fuel lines (same fuse as a 7A) in the bottom holes along the front of the center section. Did not have interference problems with the gear weldments. The problem was bending that $%^& 3/8" tubing around and up and down ...w/o kinking it. I got the left side in, but eventually gave up on the right and went with a nifty SS hose from Brett at Bonaco. The SS hoses really are a more elegant solution.

 

[terrye]

SS fuel lines

You should check the suction rating of the stainless braided hose with the supplier/manufacturer. On a suction line the hose should be rated for a full vacuum (yes I know you'll collapse a tank if you pull a full vacuum). Many hoses will not withstand a full vacuum and the elastomeric core can collapse with obvious results to the fuel supply to the engine.

 

[John Tierney]

Sleeve thru Weldment

I've routed my lines using the bottom hole in the cover support rib and the middle hole in the gear weldment. I did not have the cover bracket attached to the spar while running the tubing, and just left it loose on the tubing. I found some air line hose at the local hardware store to sleeve the AL tube thru the weldment. The hose appears to have a PVC core tube surrounded by a vinyl covering. The core tube is slipery enough to push the AL tube thru with no lubrication needed.