I need to install the custom fuel lines from Tom @ TS Flightlines. In my request for order, I asked for the tubes to be bent to allow the lines to run along the top of the cover support ribs. The reason for this is that the top hole is the largest hole and it will give me enough space to enlarge it if necessary.
The ends of the fuel lines require at least a 3/4" hole to feed the lines through. However the biggest challenge is in getting the grommets for the larger fuel lines. Aircraft spruce's list of available grommets is a bit limited so I have to stick with the following;
- Install AN931-8-13 for inside rib supports (13/16" hole dia. with a 1/2" inside hole dia)
- Install AN931-11-16 for weldments and the fuselage opening. (1" hole dia. with a 11/16" inside hole dia)
I opened up the top-most holes in the cover support ribs to 13/16" by using a unibit. The outside cover support ribs can be simply removed, while the inside support ribs can't. This required me to use a unibit with a wrench and slowly and painfully open up the hole.
Next I can thread the new fuel hoses through, but I can see they don't perfectly line up in the hole on the innermost support ribs. I needed to bend these just a tad by hand so the hose is centered in the new 13/16" hole. With that done, The fuel lines are slid into position and grommets installed. Surprisingly the grommets were easier to put in then I expected.
Now I can start measuring the brake lines that run from the bulkhead fittings in the cover support ribs to the weldment connections. Using a piece of wire I suspect I will need a 12" or longer braided line. I was concerned about how the two braided lines could rub together in such a tight space. So I decided to try bending a short hard line for this space. The bend recipe was fairly easy to figure out;
1. Start with about 12" line straightened.
2. Flair the end with a nut.
3. Bend 90deg as tight as possible (Place the nut tight against the bending tool)
4. Measure 1 1/4", bend 60 deg.
5. Measure 2 1/2", turn about 15deg and then bends up 30deg.
6. Flip 180deg and make an immediate bend of 30deg (The tube should now have a z-bend and be parallel)
7. Check fit, trim if needed. Flair the end with a nut.
Now I'm ready to work on the left brake line. From my previous work I had the initial bend recipe figure out. But I need to keep working on it. Figuring out this line took quite a few tries until I was happy with what I had. Here is the bend recipe for the left line;
Measure out 47" of tubing and straighten it.
1. Align the end of the tube with the outside of the bending tool.
2. Bend 45deg down.
3. Measure 1 1/4"
4. Bend 45deg up.
5. Move the tube so that the 45deg bend now sits outside of the bending tool
6. Bend 45deg down so that the tub sits horizontal in its final position.
7. Measure 1/2"
8. Now make the bend that jogs around the angle - bend the tube aft 45deg.
9. Flip the tube 180deg and make an immediate bend 60deg.
10. Flip the tube 180deg again and bend 45deg. to complete the jog. The tube should be close to parallel with the start. (Bend by hand if necessary to get it all to sit flat on a table).
11. Measure approximately 1 1/2", then bend down 90deg. (This dimension sets the position where the tube sits in the center tunnel area. I need mine to sit close to the angle to clear the nutplates that hold the fuel pump.)
12. Measure approximately 1 1/2", then bend the tube aft 90deg.
13. Measure 24 1/8"
14. Bend 75deg up.
15. Measure 2 1/8" and bend the tube 90deg so the tube runs to the left side of the cockpit.
16. Put a z-bend in the tube to help get the tube up and aligned with the bulkhead fitting on the outer mounting flange. (15deg bend up...then 15deg bend down to get it back parallel)
17. I also put a couple of small 10deg z-bends in the long horizontal line that sits in the center tunnel to help with clearance from ribs.
18. Insert and mark the end for final trim. Cut as required.
19. Slide the tube back into place, install bushings and nut, etc. Rotate the entire tube to allow for the flairing tool to fit. Finish the flair.
I am super happy with how it turned out. I will need to make some spacers by 3D printing them, but will do that later.
