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RV-8 Fuselage Fuel Line

A

Al RV8

Member
Hello All,

This is my first post. I have been building an RV8 QB for the past 10 months. Tail feathers are complete and I am working on the Fus and am up to the fuel system.

I was wondering if anyone has had a hard time forming the 3/8" fuel line that goes between the Airflow fuel pump and the firewall fitting. The drawing shows a simple "S" bend. I have not been able to get the line bent and leave enough room to get the flare tool on the end to form the flare with AN hardware in place???? I was thinking about making the tube straight with flares and hardware and then bending?

Any thoughts or help would be greatly appreciated.

Thanks,
Al
 
If I remember, that was one of the easier ones. Once you get the 'S' bent so the ends 'mate' with the pump and FW fitting, put fittings one one end and flare it. Then repeat for the other side. I had no problem using the flaring tool on that piece.

That said, I think I am going to get the Bonaco kit for the RV-8. Of all the tubing I have done, the Filter->Pump->Firewall are the only ones I am really happy with. The rest are 'OK' after multiple tries.
 
fuel lines

I also found this very difficult. Here is a pic. I'm actually not happy with the S tube, as it flattened oh so slightly on one of the bends, so I will probably redo it when I get stuck with other parts of the project.

Click on the image for the full article and another picture.

 
try a 360 loop

sort of. a descending one. :D. made it an easier fit for mine.



Al RV8 said:
Hello All,

This is my first post. I have been building an RV8 QB for the past 10 months. Tail feathers are complete and I am working on the Fus and am up to the fuel system.

I was wondering if anyone has had a hard time forming the 3/8" fuel line that goes between the Airflow fuel pump and the firewall fitting. The drawing shows a simple "S" bend. I have not been able to get the line bent and leave enough room to get the flare tool on the end to form the flare with AN hardware in place???? I was thinking about making the tube straight with flares and hardware and then bending?

Any thoughts or help would be greatly appreciated.

Thanks,
Al
Click to expand...
 
Al RV8 said:
...I was wondering if anyone has had a hard time forming the 3/8" fuel line that goes between the Airflow fuel pump and the firewall fitting. ...Any thoughts or help would be greatly appreciated.
Click to expand...


Is the firewall drilled yet? If not, you might consider moving the fitting. I moved mine over to the right side of the firewall which made the pump to fitting run much easier, and also shortened the flex line to the fuel pump quite a bit. I considered it a win/win.
 
Welcome to VAF!!!!

Al RV8 said:
Hello All,

This is my first post.

Thanks,
Al
Click to expand...

Hey Al, welcome to VAF:D

Good to have you aboard.

RV 8-----I want one.....

Have you considered making use of a hose instead of a hard line???

I know a lot of folks here have taken that approach for some of the fuel system challenges.

I do not know if it would be appropriate for this instance, but thought I would float the idea.

Have fun,
 
Thanks All!!

I've got some good ideas from your inputs. I think I need to go with a bigger "S" or loop. I was trying to go almost straight across with two 45 degree bends (what the drawing shows) and was running out of room.

I guess there is no problem with flow through a loop or reversing bend due to trapped air.

Thanks again,
Al Rubin
 
Al RV8 said:
Hello All,

I was wondering if anyone has had a hard time forming the 3/8" fuel line that goes between the Airflow fuel pump and the firewall fitting. Al
Click to expand...

Al,
Short answer yes. I did several of my lines 2 or 3 times to get them right. I think this is one of the those "skill set" issues and that comes with practical experience. Consequently I had to do a lot of repeats before I finally got the knack. Just keep at it.
Don
 
just remember-

To give yourself some flexibility. Mickey's setup looks really good, and allows for some movement. Be careful of your flares, and you'll do great!
Tom
 
You could use an AN833 Bulkhead 90 degree fitting at the firewall. Then all you'd need would be to bend the tube 90 degrees.

Dave
 
Must be a common problem. MY RV8 uses using the high pressure pump does not alloy enough room to make the bends and flares required to the firewall fitting.

Found an easy solution by calling Aeroquip. They make both 45 and 90 degree components called Male AN to Female Swivel Flares (37 degree flares). Essentially, its a premade flare/nut on one end and a male thread on other end. I used a 90 degree one ($13.00). That way, I had a simple 90 degree tube with flare nuts both ends and screwed it all together. Easy, easy lemon squeezy.
Now I just need to figure out what to do with all the pile of bent tube I have.
 
RV-8 fuel lines

Yeah, I had trouble with the bends and repeated them several times. Now my fuel flow sensor (red cube) is between the pump and the firewall fitting and is just about level with the firewall fitting, not really below it. Is this workable? And, slightly off topic, where have you other builders put the red cube (for a fuel injected IO-360)? Thanks in advance for any info.

Bill
 
Bonaco kit ?

I think I am going to get the Bonaco kit for the RV-8.

I am having this exact problem. After I finally got a line made that will fit in that area, I cannot flare it because there is no room at the end. I am considering going with a flexible fuel line. Come to think of it, I don't have great confidence that the other fuel lines I made and flared will not leak once I put fuel in them.

I am curious about the "bonaco kit" for the RV-8. Does it include the small line that the orginal poster referenced? Does it also include the other fuel lines?
 
Al RV8 said:
I was wondering if anyone has had a hard time forming the 3/8" fuel line that goes between the Airflow fuel pump and the firewall fitting. The drawing shows a simple "S" bend. I have not been able to get the line bent and leave enough room to get the flare tool on the end to form the flare with AN hardware in place???? I was thinking about making the tube straight with flares and hardware and then bending? Any thoughts or help would be greatly appreciated.
Click to expand...

Al, you want a Z-bend rather than 90's, the difference being the upper and lower straight legs leading into the fittings can be as long as necessary for flaring.

260ecr9.jpg
 
A picture

All:

I just finished this a few days ago and after a lot of trial and error, I feel it might be useful to share what exactly the finished line CAN look like. This was very simply to due with a 180° tube bender. Note that this is with the Airflow Performance fuel pump that Van's sells. After I finally figured out the shape, it took all of 10 minutes to fab the line and install it!
2usbiue.jpg
 
Fuel lines

What I did when I couldn't get the fitting on a line because of tension. Cut the line in the middle and put the two ends on. Then you can join the line toeghter with a union. makes life much easier.

Dick

RV8A
 
At the moment with the late model Airflow pump I've got about 2 - 3 inches from the outlet to the firewall fitting. I can make a 'Z' or 'S' or 360 similar to what others have done. My question is , all things being equal, will more convoluted lines increase vapor lock chances ( pump off )?
 
Another option. On three RV-8s we mounted one battery (PC-625) where the plans call for the fuel pump (IO-360 engine, parallel valve). We mounted the second battery on the other side in the baggage well. The fuel pump was moved and mounted vertically on the gear tower. The byproduct of this was ample room for tubing fit and bends in the line to the firewall fitting to accommodate some flexing.

More than 12 years on all three planes and all is well.

Carl
 
How much higher is the fuel pump mounted on the gear leg tower? Ideally, you want the fuel pump as low as possible WRT the fuel level.
 
Toobuilder said:
How much higher is the fuel pump mounted on the gear leg tower? Ideally, you want the fuel pump as low as possible WRT the fuel level.
Click to expand...

The fuel pump inlet is about the same height as would be for the floor mount. As I pointed out, the known 36 aircraft operating years with this configuration have been trouble free.

Carl
 
A simple solution to this mounting issue is to reverse the direction of the pump. Turn the pump 180 degrees and the inlet will be facing the firewall and line will come from the aft, go over the pump and 180 into the inlet and the output of the pump will go from the outlet to a 180 and along the pump to the firewall. Make the connections for me quick and simple
 
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