eric_marsh

eric_marsh

Well Known Member
I've riveted the middle ribs into my RV-6 fuel tanks and am now looking at installing the vent lines, fuel sender, pickup and such along with the end ribs. I decided to use a flop tube on the left tank and while eyeballing the parts and the drawings I came up with some questions.

My drawings are pretty old. This kit was originally built in 1992 and has been in storage since that time.

So here's my questions:

Looking at the flop tube it appear likely that it will hit the vent tube if the default location of the vent tube (according to my drawings) is used for the fitting that goes through the rib. Can anyone provide any thoughts on this or perhaps newer drawings?

Reading some of the other threads about related subjects I see that several people have discussed fuel return lines. I don't have any idea what kind of engine I'm going to end up with yet - I'll make that decision when I get closer to completion but it seems like a good idea to build for the option of FI should I chose to use it. Again, are there any drawings available that show the recommended method? Seems like it would be easiest to just go through the baffle.

My drawings show an optional trap door to prevent fuel from running from the first (inside) fuel compartment to the second but this trap door is only shown for the hole near the lower edge of the rib - not the one in the middle of the rib. This makes me think that perhaps that rib should not have been machined with two holes or that both should have a trap door if I choose to use one. Thoughts?

Finally I'm kicking around the idea of providing some sort of access to the first compartment in case I need access to the flop tube. It seems like a huge amount of work to pull the baffle. How many people have done this?

Thanks in advance for any feedback.
 
You're building a 6, and I have a 7, but the plans I have scanned to PDF may help you if the ones for the 6 aren't clear on this installation.

Shoot me a PM w/ an email and I'll send you a PDF of that page from my plans.

They include details on the trap door, and you also need to put in a little anti-hang-up piece forward of the trap door, and seal up the hole mid-rib.

My FI system (Silverhawk FI) did not require a return, so can't answer that question for you...

Steve
 
Vent tube Intake

I may be Nit-Picking but I keep hearing conflicting suggestions about the vent tube intake.. Is it supposed to be "Drafting" behind the Gear Strut or should it be in direct air flow? RV8 Specifically
 
eric_marsh said:
Reading some of the other threads about related subjects I see that several people have discussed fuel return lines. I don't have any idea what kind of engine I'm going to end up with yet - I'll make that decision when I get closer to completion but it seems like a good idea to build for the option of FI should I chose to use it. Again, are there any drawings available that show the recommended method? Seems like it would be easiest to just go through the baffle.
Click to expand...

I would put in an AN-4 bulkhead fitting for a fuel return line, you can always cap it. Some high pressure fuel pumps or servos require them. I have a carb'ed engine and plumbed a return line and valve from the fuel pressure sensor line. This line has an .040" fitting near the carb and will allow me to flush the hot fuel from the circuit when taxiing after a hot start. This helps to aleviate vapor lock type problems. The .040 fitting makes this relatively safe in the event of forgetting to close the valve for take off.

Larry
 
Eric,

If you plan both fuel injection *and* an inverted oil system, *and* intend to do extended inverted flying, then go for it. But if any of the above don't apply, then there's no reason to install one. It weighs more, it's more complicated (euphemism for failure-prone), more expensive, etc etc etc. You can do almost any acro maneuver except extended inverted flight without needing a flop tube. (I doubt that you want to do outside stuff in an RV, anyway; they just aren't made for it.)

My -4 had a flop tube, and I removed it.

FWIW; your mileage may vary, etc.

Charlie
 
I agree with Rv7charlie, unless you plan on inverted maneuvers with negative G's frequently the whole system becomes complex and one more link in the chain that can break. I removed my flop tube after ten years in the RV4 and my concerns were verified when I found the brass fitting scoring the bottom fuel cell skin. Fortunately I found this in time before it was more than a minor surface deviation. Do as I did for extended inverted, get a Pitts S1S, it'll get your heart rate up both for inverted flight and landings :)
 
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