I'm really struggling with what to do for the cabin area brake lines. Originally I was thinking braided nylon brake lines. I also feel pretty confident in making them out of 1/4" 3000 series aluminum. Each has its pros and cons. (Braided lines are easy, but they make the braking feel less firm and they don't bend corners as well. I know I will have space issues with my install. Hard lines are difficult to fit, but are cheap and fit in tight spaces). The disadvantages that I am focusing on right now are the braided line is how to insert the tubes through the cover support ribs on the front of the spar. The holes are not large enough for the fittings so I would need to do some surgery. The difficult part with the aluminum lines is getting the line through the gear weldment and flaring them in place for the fitting through the bottom of the skin.
I finally decided that I will at least attempt to make them out of soft aluminum tubing and if I fail, I'll go with the braided lines. After a couple hours making templates with scrap tubing. I finally figured out my bend recipe. I made the complete right brake line, and fit in into the plane. Getting the tube routed through the gear weldment was interesting (a pain). Turns out that I just struggle too much trying to flare that end near the weldment. Also take into the account if I ever have a leak or need to replace this line...This is likely impossible to re-do when the plane is complete.
It just wasn't working to my liking, so I abandoned the idea. I was deflated. I wasn't fully on board yet with switching to braided lines. Getting the cover support rib issue worked out was not going to be fun, nor easy. After some head scratching..I though back to a suggestion from my buddy mike who mentioned a bulkhead fitting in the cover support rib could be an option. Well that does solve the impossible part of the aluminum tubing option.
I went to work again...this time using a bulkhead fitting in the most outboard cover support rib. Yes, is slightly interferes with the lower hole. But if I shave down that one flat on the fittings...Bingo! We have a solution. I started working away at making a couple of lines again and by the end I have my bend recipe for the right brake line worked out.
Measure out 50" of tubing and straighten it.
1. Start with flare for the firewall fitting.
2. Measure 2 1/2"
3. Bend 45deg aft.
4. Allow short length, bend 60deg fwd.
5. Immediately bend 30deg aft so the tube is back parallel (For and offset S bend....yes the math doesn't checkout but with the consecutive bends in my tool, the original bends relax a little)
6. Measure 3", bend 90deg down.
7. Measure 2", bend 90deg aft
8. Measure 24", bend 75deg up.
9. Measure 1 1/2" (or just a tad more), bend 90deg to the right side of the plane. This gets the line through the large "S" in the fuel supply line
10. Measure 3 1/2", bend up 30deg, Allow about an 1" then down 30deg (For an S bend). This will allow the line to get up and through the first inboard cover support rib.
11. Measure about 2", bend up 30deg, then down 30deg (For another S bend). This gets the tube aligned for the outboard support rib/bulkhead fitting.
12. Trim to final fit (you will remove about 3/4"). Slide on the bushing, the AN collar and nut. Then bend the tub fwd enough to allow a flare to be fabricated. Bend the tube back by hand to the bulkhead fitting.
