bach33089

bach33089

Member
Well, I have to express a little frustration, I spent about two hours carefully forming the Right fuel tank line. Finally went to connect it to the selector valve and it was SLIGHTLY out of position. No problem right!? That's why we use soft aluminum tubing anyway! Or so I thought, I went to bend the tubing about 1/4" to get a good fit and sure enough the line buckled slightly at the bend.
sz8e4b


The buckling is not terrible but certainly is noticeable! Is this a "build on" scenario or is it a remove and replace scenario? I am truly torn on this. The engineer in me says all is well, as it does not look like there will be any significant restriction of flow (minor head loss at best). The loving builder side says start over and do it right. What are the thoughts of the forum?

Also another question, what are your thoughts on using flexible braided hoses for internal fuel lines? I am torn on this as well, but I feel that there are certainly some advantages to using the flexible stuff, if it will last!

Sorry for the long post, hopefully it will generate some good feedback for myself and others!
 
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I'd rebend it.

Alot of builder are using stainless braid teflon hoses in the cabin wit much success. Might be an option for you.
Tom
 
Check AC 43.13. They discuss it there. Don't quote me b/c I'm going from memory, but the narrowest diameter of any bend cannot be less that 75% of the original diameter, or something like that. If it's actually kinked, I'd probably replace it. It took me, I think, 2-3 tries to get each side done, so if this is your first one, I'd say you're due a couple more tries anyway! : )
 
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Tubing is cheap.

Been there done that! Buy more and keep practicing! I went through more than I thought I would. I found a local supplier of the tubing, so I bought it as I needed more.
 
When I first did my lines in aluminum tubing I got lucky and got the bends right. I left them long to attach to the wings. When the time came to trim and bend appropriately outside the fueselage, I screwed them up and had to remake one. Could not get it right after WAY too many tries. I finally surrendered and ordered fuel lines from Bonaco. Easy.

Jeremy Constant
 
bach33089 said:
...Is this a "build on" scenario or is it a remove and replace scenario?
Click to expand...

Looks like you have some nicks in the line right above the bend too... I'd replace. I suspect you know that anyway, but at least you have a good template to work from.


bach33089 said:
...Also another question, what are your thoughts on using flexible braided hoses for internal fuel lines...
Click to expand...

My thoughts? Glad you asked. From an engineering perspective, flexible hose is a specialty item used only when hard lines won't work. Compared to hard line, hose is heavy, bulky, expensive and fragile. Hard lines are the default position unless vibration/movement or repeated maintenance issues make it impractical. Hose is easier to install, sure. But the "engineer in you" (as well as the aircraft "manufacturer in you") will have to decide if the ease of one installation offsets the extra weight and bulk you will carry for the life of the aircraft.

Certainly your choice, but when in doubt, ask yourself if you're building an airplane or a bulldozer. :)
 
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I wish I had ordered the fuel lines first. It would have saved me a lot of time and effort. Money well spent. I cut out the tubing and replaced.
 
Thanks!

Thanks for all the feedback! I am gonna work on a second iteration of this fuel line! I am also going to look into using some flexible fuel lines in certain applications in the fuselage, but I will try my best to use rigid lines where possible as from what I've read, Flexible lines have a fairly short life expectancy compared to the rigid aluminum lines.
 
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