Tbone

Tbone

Well Known Member
For those that have fabricated their FWF fuel lines out of stainless tubing, how has it worked in service? I like the simplicity and the compactness of the pictures I have seen on this forum and also have read the "concerns" of such. Any issues? I see that there are different types on Spruce. If I were to "experiment", what tubing should I order and what are the lessons learned on trying this? Thanks.
 
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I have used .035 wall seamless tube from Spruce with great success. This stuff is far stronger than required, but still significantly lighter than the firesleeved braided steel hose normally found.

Lessons learned:

You only get one shot at bending it, so make a model out of welding rod or the 3003 junk provided by Van first.

Wherever possible, keep the bends to cardinal angles such as 45 and 90 degrees. It makes the math much easier and the results look more professional.

Add some lubrication to the tube where the bender "slides" across the surface when bending. The stainless tube is much stiffer than aluminum, but a bunch of the effort is due to surface friction. Lube helps a lot.
 
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My first RV went 2k hours with all stainless behind the firewall. Never had any issues.
 
Stainless is neat looking, very strong. BUT---it does take practice bending. Like Michael said, you only get one shot. Measure 3 times, then bend. Make a pattern in aluminum, then duplicate it.
Tom
 
3003 not junk

or the 3003 junk provided by Van first.
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You are certainly free to make your own choices when it comes to fuel lines
but calling Van's supplied fuel lines "junk" is way off the mark.
It is used in thousands of RVs including Van's fleet and shows no signs of being "junk" unless you make junk of it.

Most of the downsides to Stainless steel fuel lines are in properly fabricating them. 3003 tube provided by Vans is super easy to fabricate and very cheap compared to stainless steel.
 
Thumbs up to this....

N427EF said:
You are certainly free to make your own choices when it comes to fuel lines
but calling Van's supplied fuel lines "junk" is way off the mark.
It is used in thousands of RVs including Van's fleet and shows no signs of being "junk" unless you make junk of it.

Most of the downsides to Stainless steel fuel lines are in properly fabricating them. 3003 tube provided by Vans is super easy to fabricate and very cheap compared to stainless steel.
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The 3003 tubing is a great choice for installation by amateurs, which in reality, most RV's are built by.....
 
Scott,

Will most high duty flairing 37deg tool work flairing the 3003 tubing? I know I would have to purchase a new flairing tool for stainless. Thanks
 
Maxrate said:
Scott,

Will most high duty flairing 37deg tool work flairing the 3003 tubing? I know I would have to purchase a new flairing tool for stainless. Thanks
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I have used 3 different tools over the years with no problem, so I think you probably could use any 37 deg tool. Just make sure the forming die has a nicely polished surface so it puts a nice finish on the inside of the flair.
 
Mark----Ive used the same flaring tool (RFT37 from GAHCO---shameless plug to my friend Tom Brink) for 3003, 5052, 6061T6 aluminum, as well as 304 and 316 Stainless.
Yep, 3003 is perfectly fine for the applications intended. 3003 has been used for years with great results. Its all in the care in which you use it.
Tom
 
OK, I'm confused. Some are saying you use SS FWF, Kahuna says it works great aft of the the firewall. Where are you using SS lines in place of flexible lines, and why?
 
I am contemplating using SS FWF on mechanical fuel pump to the FI servo. Reason being is it will be more compact and......I want to try it. Material is on order and if I don't like it or can't make it look good I'll get Tom to make me a flexible hose. I have used the alum line supplied by Van's aft of the firewall and "try" to do "best practice" on this project. I build aircraft for a living and have made some great contacts and have some of the best equipment and resources around. I just have to satisfy me!:)
 
I replaced hose with SS on the RV-8 several hundred hours ago with zero issues. Also just did the same thing with the Rocket at the last Condition Inspection - no issues there either. The Rocket was quite simple, with only two 90 degree bends off the fuel pump to get the line running along the oil pan rail; a 45 down between the fwd induction tubes; then a 90 to the servo. The RV version required more work to get around the engine mount, but came out very clean.
 
Scott Hersha said:
OK, I'm confused. Some are saying you use SS FWF, Kahuna says it works great aft of the the firewall. Where are you using SS lines in place of flexible lines, and why?
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In my case, the cabin-side Z bend between the electric fuel pump and the steel firewall bulkhead fitting is stainless. On the opposite side, stainless line connects a few components across the firewall.

Compared to aluminum, there are two reasons to select stainless; (1) fire resistance and (2) resistance to high-cycle fatigue.

Compared to hose, it is less bulky and more temperature resistant, but is probably not quite as mechanically reliable as the best hoses and fittings.
 
DanH said:
...but is probably not quite as mechanically reliable as the best hoses and fittings.
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Dan, how do you define mechanical reliability? Are you talking about the flare and sealing surface? If so, I'd agree that the machined hose fittings might have a slight edge, but the comparative fragility of the hose itself brings it way down the list.

Kind of a moot point for this discussion as the requirements for an RV fuel system are so modest that both high quality hose and SS hardline is total overkill.
 
Governor

Would it be safe to say that the prop governor line could be done the same way? Any pictures of that? Factory pre-made? Source?
 
The typical prop governor line is a rigid hard line, though hose is used sometimes. In the early days, Lycoming thought it was acceptable to use aluminum fittings on the stainless hard line, but there were some failures so current practice is to use steel fittings. Keep in mind that the governor puts out hundreds of PSI, so it sees harsher duty than the fuel system does.
 
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