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90 Deg elbows in Fuel supply line.

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N804RV

Well-Known Member
Joined
Jun 9, 2013
Messages
596
Location
Mount Vernon, WA
How many 90 degree elbows can you put into a fuel supply line before fuel flow is affected (boost pump on/boost pump off)?

I went with an Andair fuel selector valve and Airflow Performance inline filter and boost pump on my fuel injected RV-8 build. I bought the TS Flightlines braided fuel line kit. But, for 2 of the lines I am not happy with the amount of effort needed to get these lines into place so that the B-nuts easily thread onto the connections. A good aluminum tubing "hard-line" will fall right into place when properly made. And, I think that's what I'm looking for in this application, since I'll have to periodically remove and clean the inline fuel filter. I can see trying to get a steel braided teflon line threaded onto the filter, located to left of and below the pilot's seat in an RV-8 is going to be a major PITA. And, my goal is to fab up a rigid line that lines up without any effort.

The problem is, I don't have room to make a 90 deg bend on 3/8" tubing, and then get a flare on it (or flare it first then get the ferrule past the bend). I think the easy solution is to put another elbow on the filter inlet. But, with the short sweep of these elbows, I'm worried about compromising fuel flow at low-fuel/climb angle.

What do you guys think? Anyone have any experience with this sort of design consideration?

A little bit harder fix would be to move the filter bracket further forward and make a new hard line between the filter and the pump. But, then that makes the joggle to get the hard line through the landing gear tower more difficult.

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