I have a 9A and I'm working on the fuel lines from the valve to the wings. The plans show the lines going through the bottom grommets but when trying that route the gear weldment obstructed the grommet opening on the brackets that hold the covers in place. I opted to use the top grommets which are larger but the route seems much easier. Is this Kosher? Also, I had to make a pretty sharp bend to line up to the fuel valve and I ended up with a very slight flattening of the line. Not enough to affect flow or rigidity (I'm assuming) but ever so slight...is this acceptable? Thanks all!!
Van's Air Force
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Fuel Lines
- Thread starter mchesney
- Start date
Greg Arehart
Well Known Member
Mike,
I'm also putting in the fuel lines. I first did so a couple of weeks ago, hand bending the tubing through the gear leg mounts. I have ultimately decided to pull these tubes, and replace (I prefer to replace them rather than try to rebend - try bending these Al tubes back and forth a couple times and watch them crack!) them, routing the line in front of the gear leg mounts rather than through them. Main reasons are 1) access, in case I ever have to replace them (hope not) and 2) less chance of rubbing a hole in them against the gear leg mount (I think I could deal with a hole in the vent line, brake line or some other part, but not a fuel line!). I also plan to go to my Lowes aircraft section and purchase some plastic tubing (3/8 inch ID, about $ 0.16/foot) which I will split and wrap around the fuel line anywhere it goes near a potential wear spot, also to minimize the possibility of a rubbed hole. The plastic should show wear spots before it wears through to the Al; I plan on including visual inspection in my list of regular inspection stuff.
Your original query was about flattening of the tube - unless you bent it pretty sharp and/or flat, it should not be a fluid flow problem.
greg
I'm also putting in the fuel lines. I first did so a couple of weeks ago, hand bending the tubing through the gear leg mounts. I have ultimately decided to pull these tubes, and replace (I prefer to replace them rather than try to rebend - try bending these Al tubes back and forth a couple times and watch them crack!) them, routing the line in front of the gear leg mounts rather than through them. Main reasons are 1) access, in case I ever have to replace them (hope not) and 2) less chance of rubbing a hole in them against the gear leg mount (I think I could deal with a hole in the vent line, brake line or some other part, but not a fuel line!). I also plan to go to my Lowes aircraft section and purchase some plastic tubing (3/8 inch ID, about $ 0.16/foot) which I will split and wrap around the fuel line anywhere it goes near a potential wear spot, also to minimize the possibility of a rubbed hole. The plastic should show wear spots before it wears through to the Al; I plan on including visual inspection in my list of regular inspection stuff.
Your original query was about flattening of the tube - unless you bent it pretty sharp and/or flat, it should not be a fluid flow problem.
greg
craigvince
Well Known Member
Another option
Another option would be to contact Bonaco; Talk to Brett there. They now make flexible fuel lines (made from stainless braided teflon with a clear chafe coating) to go from the sidewall to the center fuel valve for the 7As and 9As. I spent several hours trying to bend mine like you guys did, and if these new fuel lines had been available, it could have saved me a lot of cussing!
Another option would be to contact Bonaco; Talk to Brett there. They now make flexible fuel lines (made from stainless braided teflon with a clear chafe coating) to go from the sidewall to the center fuel valve for the 7As and 9As. I spent several hours trying to bend mine like you guys did, and if these new fuel lines had been available, it could have saved me a lot of cussing!
After struggling for days trying to put the fuel line in one piece winding through the gear leg and over and up to the selector valve, I changed the approach and installed it in two pieces with a union at the rib closest to the valve. Took me a couple of hours to complete the installation in that manner after struggling for days trying to do it in one piece!
A week later, I saw a post here where someone else had done exactly the same thing (they also posted pictures). Lighter and less expensive than SS lines...
Keith
N355RV
Flying!
A week later, I saw a post here where someone else had done exactly the same thing (they also posted pictures). Lighter and less expensive than SS lines...
Keith
N355RV
Flying!
A guy in my EAA chapter used two pieces and a union for the fuel lines in his 9A. The plane flies just fine.
I installed my fuel lines by keeping the gear mounts loose. It worked OK, but I still wouldn't say it was easy. I decided to use two pieces and a union for my brake lines and that went pretty smoothly. I just hope the extra fittings don't leak.
N941WR
Legacy Member
It is only Kosher if you don't run any wires under it. Should you have a leak, the fuel could drip on the wires and that may not be a good thing.
Any Tech Advisor worth his salt would ask you to move the fuel lines to the bottom holes.
alpinelakespilot2000
Well Known Member
Check AC43.13 or Standard Aircraft Handbook. I think the rule (going from memory) is that the flat part of your bend must be 75-80% of the normal diameter of the tubing. If you've bent it thinner than that it probably needs to be replaced. Those lines are a bear, even for taildraggers, so hang in there. Hope this helps.
Here's s a page I wrote awhile ago to help out. This would be documenting the second time I ran my fuel lines on the same project.
http://www.rvforge7.com/pg3.htm
http://www.rvforge7.com/pg3.htm
Bubblehead
Well Known Member
Bonaco flare angle
craigvince
I looked on their website and I could not find mention of using aircraft fittings with their unique tubing flare angle. I assume you were able to get ones with standard aircraft flare angle?
craigvince
I looked on their website and I could not find mention of using aircraft fittings with their unique tubing flare angle. I assume you were able to get ones with standard aircraft flare angle?
craigvince
Well Known Member
Captain Avgas
Well Known Member
I'm with Bill Repucci....don't run the fuel lines above the wiring....it's not acceptable aviation practice (ie very dangerous).
I saw that most of the fuel lines (and brake lines) on the nose gear models looked like mangled spaghetti so I opted for stainless braided flexible hose between the fuel selector and the wing tanks (which I made myself to the correct length).
I used rubber grommets at every penetration, including the gear mount. The hose is easy to move, even when fully installed....so that should make connecting up the wing tanks easier.
But not a recommended detail for those rushing to get finished....more for those who love building.
I also used the Andair selector.
Left click photo for larger pic.
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Fuel lines above wiring-Danger Will Robinson?
Several folks have posted that running the fuel lines over electrical wiring is not acceptable practice and is very dangerous. Many RV-6/7/9's have their wiring running down the center of the cockpit and under the fuel valve and under the high pressure fuel pump. This too would then be considered an unsafe condition.
I am not saying that I disagree with the comments about running fuel lines above wiring but don't you think that there is a much greater likelihood of a fuel leak from one of the dozen or so connections on the fuel valve or fuel pump system that might leak well before a continuous run of aluminum fuel tubing?
I believe a good rule of thumb in this case is that you shouldn't have electrical connections directly below fuel lines.
Paul
Several folks have posted that running the fuel lines over electrical wiring is not acceptable practice and is very dangerous. Many RV-6/7/9's have their wiring running down the center of the cockpit and under the fuel valve and under the high pressure fuel pump. This too would then be considered an unsafe condition.
I am not saying that I disagree with the comments about running fuel lines above wiring but don't you think that there is a much greater likelihood of a fuel leak from one of the dozen or so connections on the fuel valve or fuel pump system that might leak well before a continuous run of aluminum fuel tubing?
I believe a good rule of thumb in this case is that you shouldn't have electrical connections directly below fuel lines.
Paul
craigvince
Well Known Member
Flexible fuel lines
Bob,
I have decided to go ahead and change out my fuel lines to flexible, since I'm going to change my fuel valve anyway, which probably means re-working my existing fuel lines. What length did find worked best from the valve to the wing?
Bob,
I have decided to go ahead and change out my fuel lines to flexible, since I'm going to change my fuel valve anyway, which probably means re-working my existing fuel lines. What length did find worked best from the valve to the wing?
I'm with Bill Repucci....don't run the fuel lines above the wiring....it's not acceptable aviation practice (ie very dangerous).
I saw that most of the fuel lines (and brake lines) on the nose gear models looked like mangled spaghetti so I opted for stainless braided flexible hose between the fuel selector and the wing tanks (which I made myself to the correct length).
I used rubber grommets at every penetration, including the gear mount. The hose is easy to move, even when fully installed....so that should make connecting up the wing tanks easier.
But not a recommended detail for those rushing to get finished....more for those who love building.
I also used the Andair selector.
Left click photo for larger pic.
Captain Avgas
Well Known Member
Craig, I never measured mine. I made them in situ to fit perfectly. Firstly I installed the fitting on the fuel selector end. Then I connected it and ran the hose along it's path and out through the side of the fuselage. And then I marked it and removed it. Finally I cut it and installed the second fitting.
The length of the hose will vary depending on the type of fuel selector and fuel selector fitting you use....and also depending on the path you choose. In the end you'll probably find that the right hose will be a different length from the left hose....I certainly did.
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Captain Avgas
Well Known Member
When in doubt you can always refer to the bible (AC43.13). Section 8 says: "Where practical, route wires and cables above fluid lines".
Vans RV7 DWG 11 also specifically notes that the bottom snap bushing in the relevant cover support ribs (F-783B and F-783B) is an SB500-6 for the 3/8" fuel line. The top snap bushings are an SB625-7 for the electrical wires.
But as I'm prone to pointing out, this is the Experimental category...we can adopt best practice and follow the designer's drawings, or alternatively we can just plough on and make it up as we go along.
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I just run mine two weeks ago. I had no problems. Actually, I had them in the fuel vent lines (one of them totally remade).
First, I read plans (not so useful; I used a slightly different intersection among brake line and fuel line). Then, I read some websites. Following web suggestions, I decided to put gear mounts in place without bolting them (nevertheless I had no need for disassembling them).
I did as follow.
1) Staighten the fuel tube for a couple of feet or less;
2) Insert the straight end in the first bushing (the one beside fuel valve);
3) Insert the tube untill reaching the second bushing (it may be necessary to make a very gentle slope); once finished the straight part of the tube, straighten more of it;
4) Continue inserting tube one of the gear mount holes (can't remember which; look plans; remember to put the grommet, even if it is not stated on plan...it is much easier BEFORE tube is installed through the hole);
5) Make tube go out from the hole as maximum as possible (untill it reaches fuse skin);
6) Start making a gentle S while entering in the side skin grommet hole; let it go out for at least 5'' ( I did more than 6'') (I read this measure on the web);
7) Adjust the S by hands, adjust line and...finally, make the slope in order to joint the tube (uncutted portion) to the fuel valve;
8) Trial fit fuel valve and check where to cut tube; cut the end with a tube cutting (it makes neat and perpendicular cuts: for good flarings), check with the fuel valve for correct lenght;
9) If lenght is correct, insert nut and sleeve (anyone forgets at least once) and flare;
10) Put tape on both ends to avoid material giung inside tubes (I read an article from Van's which reported a story of 5 fuel starvations at take-off dued to animals inside fuel lines).
I'm very happy with my fuel lines.
First, I read plans (not so useful; I used a slightly different intersection among brake line and fuel line). Then, I read some websites. Following web suggestions, I decided to put gear mounts in place without bolting them (nevertheless I had no need for disassembling them).
I did as follow.
1) Staighten the fuel tube for a couple of feet or less;
2) Insert the straight end in the first bushing (the one beside fuel valve);
3) Insert the tube untill reaching the second bushing (it may be necessary to make a very gentle slope); once finished the straight part of the tube, straighten more of it;
4) Continue inserting tube one of the gear mount holes (can't remember which; look plans; remember to put the grommet, even if it is not stated on plan...it is much easier BEFORE tube is installed through the hole);
5) Make tube go out from the hole as maximum as possible (untill it reaches fuse skin);
6) Start making a gentle S while entering in the side skin grommet hole; let it go out for at least 5'' ( I did more than 6'') (I read this measure on the web);
7) Adjust the S by hands, adjust line and...finally, make the slope in order to joint the tube (uncutted portion) to the fuel valve;
8) Trial fit fuel valve and check where to cut tube; cut the end with a tube cutting (it makes neat and perpendicular cuts: for good flarings), check with the fuel valve for correct lenght;
9) If lenght is correct, insert nut and sleeve (anyone forgets at least once) and flare;
10) Put tape on both ends to avoid material giung inside tubes (I read an article from Van's which reported a story of 5 fuel starvations at take-off dued to animals inside fuel lines).
I'm very happy with my fuel lines.
