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How far do fuel lines extend out of fuse?

N

N316RV

Well Known Member
Searched the forums but could not find the answer to the below question. I have my fuel and vent lines installed on my -9A. I would like to go ahead and cut to length and make the outside flares. I do not have room to install my wings right now. It would seem that this distance would be consistent from airplane to airplane. Could someone building a -9A that has installed the wings and cut fuel line to length tell me how long these extend outside the fuse?

Thanks
Alan Jackson
 
Alan,

It is difficult to say exactly because they can push in. I left mine long and then trimmed them after the wing was fitted.

the other option is to put a 90 degree bulkhead fitting through the side of the fuselage and then make a short section to fit between that and the wing.
 
Mine are 2 1/2 inch flared. Wings were fitted everything was matched perfect. I remember I researched that subject long time ago but didn't bookmarked. You may want to check Scott Card's website he was documenting the fuel lines very extensively. As Bill said there will be a play of appr 1/8 - 3/16 because lines are long and relatively rigid if you build by the plans.
 
I left my about 6" long out the side. I plan to final cut and flare them once my wings are attached. (same with the vent lines). I also disconnected them inside and left them flush with the sides so that I don't bend them over while working around my very small work space. I installed a straight disconnect just OTBD of the valve. Made it much easier to fab the lines and I was able to plumb the valve now.
 
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0"

I terminated all lines at bulkhead fittings on the wing and fuselage. I selected straight or 90 degree fittings on the lines, fuselage skin, rib or firewall as required to provide the best access for removal and maintenance. There are no floating penetrations of the fuselage skin or firewall by pitot, vent, fuel or brake line tubing. I formed the interface tubing after assembly of the structure.

Bob Axsom
 
Rigid fittings at the BLKD might make the line too rigid? I am not sure how much flex there is with the wing, but I think Van's put the rubber grommets there for a reason?
 
I think Van's design is for simplicity

apkp777 said:
Rigid fittings at the BLKD might make the line too rigid? I am not sure how much flex there is with the wing, but I think Van's put the rubber grommets there for a reason?
Click to expand...

You have to go beyond the mental image of short tubes connected between ridged points on two surfaces with relative operational movement to conceive how this works I guess. You have to say, given the there may be some relative movement betweem the mounting surfaces at high and low frequencies, what form should the tubes take to provide strain relief and allow easy access and removal? ~550 hours of high speed low altitude racing and many log cross country flying trips there are no problems with my installations between the wing and fuselage or the firewall and the engine. The primer lines are also solid and have a full loop in every segment. You cannot do point to point plumbing with no provisions for strain relief and expect the installation to last.

If you believe Van's design is the ultimate for every installation you are going to be disappointed down the road if you have the flapper valve instalation in the throat of the FAB for carb heat.

Bob Axsom
 
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You are right, Van's made it really simple. (and cheap). Still, I thought about a 90 degree fitting at the blkd and just couldn't figure out how I would provide strain relief in the short distance from the fuse to the wing, short of putting in a flexible line. I am not a big fan of the grommet solution either. One thing for sure, there can be NO potential failure points in a fuel supply line.
 
Pictures?

Bob Axsom said:
I terminated all lines at bulkhead fittings on the wing and fuselage. I selected straight or 90 degree fittings on the lines, fuselage skin, rib or firewall as required to provide the best access for removal and maintenance. There are no floating penetrations of the fuselage skin or firewall by pitot, vent, fuel or brake line tubing. I formed the interface tubing after assembly of the structure.

Bob Axsom
Click to expand...
Hi Bob,
Would you have pictures of your installation? I don't like the idea of having anything floating at wing to fuselage junction, be it fuel lines or electric wiring, so I want to put terminations on both sides and make removable links to connect pieces together. Problem is I have no clear idea on how to do that:confused:
Thanks in advance
 
Photos

wingroot1.jpg

The first photo shows the lines on the left side without the left main tank installed. I have four tanks so in the photo you see the tip tank fuel line which is the lower one routing down the spar. It is a long 3/8" tube and it connects to a 90 degree union, then to a short "U" shapped 3/8" tube, then to a 90 degree bulkhead connector. The upper tube on the spar is the pitot line and it connects directly to a 90 degree bulkhead connector. The steel jacketed hose is disconnected in the photo but it loops back and it will connect to the straight bulkhead connector in the main tank with a 90 degree hose connector (expensive). The black sharpie marking on the fuselage shows the location and orientation of the main tank vent and the straight bulkhead connector below and aft of it is where the vent line will attach. You see a rubber chaffing protection strip tied to the tip tank line to protect it from the steel jacketed hose even though they are not in contact in the 1 g state. The line (tube) connected to the 90 degree bulkhead connector below the pitot connection is the brake line. The photo below is the completed installation taken on 11-8-03. I went to my build photo album for these photos and they are scanned

wingroot2.jpg


Bob Axsom
 
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Very helpful

Thanks for the pics, Bob.

I didn't figure out the tank could be installed AFTER the wing so it would ease final plumbing to the bulkhead fittings :eek:
Now that makes perfect sense.
 
No, no, no..........

Daniel, that is not a 9 !! (Bob's plane).

On the 9, those fuel lines will connect straight to the tank, opposite the rubber grommets! If you put another fitting on the fuselage, you will have a piece of tube so short between them, that you will hardly be able to put a flair on both sides! I guess you want a bit more play on the lines (rubber grommet!) also!

I measured the length, from the wing/bolt holes/fuselage/etc. to get the right length, but I have not connected the wings yet, so I can not give you the correct dimensions yet.

Regards, Tonny.
 
Pilottonny said:
Daniel, that is not a 9 !! (Bob's plane).

On the 9, those fuel lines will connect straight to the tank, opposite the rubber grommets! If you put another fitting on the fuselage, you will have a piece of tube so short between them, that you will hardly be able to put a flair on both sides! I guess you want a bit more play on the lines (rubber grommet!) also!

I measured the length, from the wing/bolt holes/fuselage/etc. to get the right length, but I have not connected the wings yet, so I can not give you the correct dimensions yet.

Regards, Tonny.
Click to expand...

Tonny,

Right angle connections and a steel jacketed hose are used to eliminate straight runs of tubing between the fuselage and the tank. You do have to plan the installation to incorporate strain relief bends/loops etc. The RV-6A which I build has the "stick the tube through the grommet" original design as well. It was not acceptable to me. I cannot imagine physical constraints that cannot be dealt with based on fittings/tubing/hoses displayed in catalogs such as Aircraft Spruce. but if in doubt and you cannot resolve the inner conflict with complete confidence then you certainly should not go off on your own as I did.

Bob Axsom
 
I measured that distance at about 2 5/8" when I had my wings on. That matches well the 2 1/2" somebody mentioned earlier.
Since the fuel lines inside the fuse have some "give", just make sure you push them back in the fuse as far as you can before you measure and cut outside the sideskin. Then you've got a bit of extra to play with.
 
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