Securing fuel lines to fuselage tubing

[svyolo]

Eric Newtons site shows putting rubber/ plastic tubing over the aluminum fuel line and securing it to the fuselage tubing (every 16 inches) with waxed nylon twine. Any other materials? High quality tie raps? I have lots of scrap bits of kevlar. I could take a few strands and tie the fuel line to the tubing (chafe protected), and dab some epoxy on the knot when it is done for sure.

I can't find anything else except double Adel clamps. I will use that in a few places, but not going up the to the wings.

[robcaldwell]

I used this carbon fiber sheath to cover my fuel lines in areas where they are exposed. Specifically along the front window posts. I did it more aesthetics, improved fit and finish. But this product is extremely durable and does provide some protection. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I also talk about the carbon fiber covered fuel lines in this video, at the 5 minute mark:

[robcaldwell]

AP servos are Dynon.

[Archer39J]

Nice vid! I really like the conduit along the side, I'll probably end up doing something similar now. I was thinking though, is the carbon sheath around the fuel lines exposed fiber? If so I'd be concerned about corrosion between it and the AL line, unless I was positive no moisture could get in there.

[robcaldwell]

Dave - You're probably right about the carbon fibers not acting friendly with the aluminum fuel lines. I will probably switch over to a softer material. I've been using these nylon sleeves for my wiring. https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

[Archer39J]

Same boat, will probably end up using the spiral tube covering and wax nylon, or maybe hose cover, we'll see. Kevlar sounds like a good idea if you have some spare lying around.

[Bdflies]

I found Eric's use of waxed lacing cord to be a great solution. I used some DG clamps, but mostly used lacing cord.

Bill

[svyolo]

Thanks. I will probably just use the kevlar threads as I have some scrap.

[Bcone1381]

Know your Knots! Good Lick with Kevlar, Let us know how it works.

Another Data Point to consider.

I used the Nylon Waxed Cord extensively and exclusively to secure joints building wood Skin-on-Frame Kayaks.. The kayak frame has no glue or screws, only lashings that use the waxed nylon cordage. Each kayak has +100 of joints tied with this stuff. You will like it if you know how to use it.

The beauty of the this product is at least two fold.
-Its light.
-When each wrap of the lashing is tightened, the waxed cord bites into the previous wraps, locking it in place. (This makes it very nice to work with. Try getting the same strength tying with low friction cordage. You wont get it tight.)
-It stretches.
-Its strong.
-If the joint is jarred or vibrated, the joint will give and spring back into place.

Choosing this method may require a small amount of knot tying education & practice. I think the Sheer Lashing (boy scout knot) would give be my choice with some modifications.

The video below shows the knots used to lash a kayak and you'll see what I mean.

https://www.youtube.com/watch?v=Zy9JOv3mHgw

I would use the figure eight knot as a stopper knot shown at 0:43 followed by an Eskimo Knot at 1:31. The finishing of the knot at about 4:15 will be real nice when applied to both sides of the Sheer Knot. I would start the joint as I described, then Wrap it & Frap it, then secure using his finishing method.

[svyolo]

I have used waxed twine on lots of fishing lures. It is good stuff. You might have just talked me into it.

[Glenn Patterson]

We did the same as BDFFlies with lacing cord. Slid & tied on some split fuel line where there was any risk of it touching any metal. If the line is secured well along its length it should not move. A person wanted they could fold aluminum trim mouldings to cover the fuel lines and all the brick a brack that runs down the inside corner. Airplane weighs enough w/o adding the vanity weight. We put aluminum covers up the rear door posts to protect the fuel lines from accidental hits loading baggage otherwise the remaining fuel lines are safe from abuse.

[spinningwrench]

I will use a combination of lacing cord and Adel clamps where necessary. I really like using clear heat shrink tubing to protect the fuel line. It shrinks down over bent tubing to form an almost invisible layer of protection. I buy it at 1/2" initial diameter and it will shrink to 1/4" if necessary. This particular tubing is abrasion resistant, solvent resistant, and an anti-corrosion based material. The clear rather than black tubing allows me to do a good inspection of my fuel system when required. In the attached photo it is almost impossible to see. It has a wall thickness of .025" when shrunk and one could put on multiple layers for high impact areas.

[coosbo]

Does anyone have advice or a picture they could share that shows how you‘ve secured your aft fuel lines? I’m trying to determine my best option for securing the section behind the front doors.

[robcaldwell]

That is almost exactly what I did. I also installed a cushioned adele clamp on the tube about 3/4 down on the vertical tube. I enclosed that section with fabric. The adele clamp didn't come out so good with the fabric over it, but I am probably the only one that knows...

[Battson]

Does anyone have advice or a picture they could share that shows how you‘ve secured your aft fuel lines? I’m trying to determine my best option for securing the section behind the front doors.

Mine is exactly like that, nothing more apart from two things:

1. plastic padding on the line to prevent it rubbing on the steel frame at the top.

2. the fabric at the top holding it in place, until the connection to the wing was established.

It has been more than fine, it's been ideal. If you leave it exposed occasionally someone may try and hold onto it, otherwise covered with fabric it will be grand.

[coosbo]

Johnathan, just to confirm I'm on the same page. You didn't use any clamps, lacing, etc. between the bend at the top that goes to towards the wing root and the bend at the bottom that goes under the door. Just covering it with fabric is sufficient? Not that it can go anywhere once fully installed, I just thought I needed a clamp or something to satisfy the every 16" recommendation. If it's not necessary I won't worry about it.

Rob, what did you fasten the fuel line cushioned adel clamp at that location to? Did you use attach it to an all metal adel clamp that you put on the fuselage tubbing? Or did you attach the cushioned clamp on your fuel line to the door former?

Appreciate the help, guys!

[robcaldwell]

Here's my build log for the fuel lines.

https://bearhawk4place.blogspot.com/2018/10/fuel-lines.html#more

I took a piece of AL angle and riveted it to the back of a tab on the door former. Used that as a tab for the adel clamp.

[coosbo]

Thanks, Rob!

[rodsmith]

I used gaffers tape to secure the tube to the doorpost before covering with fabric. I used a thick heat shrink tubing over the fuel line first.

[Battson]

Johnathan, just to confirm I'm on the same page. You didn't use any clamps, lacing, etc. between the bend at the top that goes to towards the wing root and the bend at the bottom that goes under the door.

Yes that is correct. It's more than 16 inches but I haven't found it necessary. I wanted the clean line, as Rob mentions a clamp will show.
A clamp midway along wouldn't hurt if you're concerned about vibration etc. The tube does not vibrate or anything on my install.

Be warned, you need to use white adel clamps on fabric, they are hard to get. If you use black rubber, the black colour will bleed through your fabric over time and you'll have what looks like a cigarette lighter burn mark on your fabric after a few years.

But you do want to have rubber, plastic can eat through the metal if used in an adel clamp. It's rare but not impossible.

[coosbo]

Got it. Thanks!

[spinningwrench]

I didn't like the bulk of an Adel clamp so I just welded small tabs on the fuselage tubes. The fuel line has a double layer of heat shrink tubing for protection. The zip tie shown will be replaced by a small rubberized version at final build.

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