Online Community of Zenith Builders and Flyers
Posting in the open forum, as this question is not truly type specific. I am building a 750 Cruzer.
I like the idea of keeping fuel lines out of the cabin, if at all possible. I have seen others route fuel lines inside the stiffener on the bottom of the airplane C75F10-4. I was thinking of running the fuel lines behind the baggage compartment and then through the stiffener towards the firewall, then covering this stiffener to protect the lines. But, this would have the lines routed underneath the main gear.
So to my question, does the main gear flex in middle when landing the airplane??? If so how much??? Is it a bad idea to route lines/wiring underneath the main gear???
Any ideas or suggestion on routing fuel/brake/wiring are most welcome.
I’m not flying yet, but I tend to think that the main gear flexes a bit. Think of it this way: the gear is attached only at the outer ends. If you landed in a crosswind, the pressure on the one wheel will cause some flex/bow in the center section of the gear. Additionally, look for the video of Roger demonstrating how to check for gear tightness by rocking the gear.
The span of the main gear running underneath my Zodiac flexes a bit more than I thought it would, and was enough to crack a rigid fiberglass fairing I'd put there. I've got about a third of an inch of clearance there now which seems ok.
I ran flexible fuel line (5/16 fuel injection hose) underneath the main gear and have not had any problems with that.
Be careful that you don't end up with low areas or "sagging" in your fuel lines where a slug of water can collect.
Your fuel line will be inside the cockpit from the wing root to the floor no matter how you go, unless you somehow run it on the outside of the fuselage sides, which I can’t see happening. Considering that fact, I don’t see any advantage for you to not run it the rest of the way inside the cabin to the firewall. You’re going to need a shut off valve within arm’s reach of the pilot anyway. Just my opinion.
One thing I believe is important is to install disconnects in the fuel lines, pitot/static tubes, and wiring at the wing root. If you ever need to pull a wing off, you will appreciate that. You will need access panels at the underside skin of the wing roots not supplied with the kit, but available at mykitairplane.com.
Here’s a pic of mine. The access panel is obviously removed in this photo.
With regard to brake lines, I ran mine the way the Homebuilt Help video showed and it has worked fine for the past 700 hrs and 7 years of use. Some builders use stainless braided lines, some even use AL tubing, all depends on personal preference.
With regards to the question of does the landing gear flex, yes it does. Right in the middle. On a “firmer than wanted” landing, the legs splay out at the bend point, and the center of the gear flexes downward.
Good luck with your build.
Fuel lines inside the fuselage are better protected and may be less likely to rupture in a crash.