RV-3: F-1 Style Fuel Tank Vents - Page 2

DarylT · #11 10-18-2011, 09:03 AM

The ones from Aircraft Extra are threaded for an AN3 bolt. I am using a remove before flight flag on a drilled headed bolt. Still doesn't solve the wing flange issue that Paul describes though. But they work great on the side by sides.

mfleming · #12 08-04-2019, 03:58 PM

I thought I'd revive this old thread.

I'm getting ready to to make my vent lines for my -7 and I thought the OP may like to update us on how this method worked for him. It looks much simpler to construct and I like the idea of minimizing the fuel lines in the cockpit.

If Paul is busy flying his little jet around

, maybe someone else could lend their experience with the coiled vent method.

Captdf · #13 08-04-2019, 04:49 PM

Four years ago I was rebuilding an already-built RV4, and I needed to replace the vent lines inside the fuselage due to damage. I decided to try the ?F1? vent installation because it was easier to accomplish than replacing the internal lines.

The F1 vent system spits more fuel on the ramp than the original installation did and seems to vent more fuel at high AOA. At my next condition inspection I?m planning to re-do the system and go back to the vent system as shown on the plans.

steve lenne · #14 08-04-2019, 05:08 PM

I used Paul?s vent suggestion and is working just fine on my rv3b.

Steve

Rv3B
100 hours

FinnFlyer · #15 08-04-2019, 07:34 PM

Why carry the vent line all the way through the tank and through the root rib?

Seems the simplest installation would be a 90 degree fitting in the most outboard tank rib at highest point and straight down and out a hole in the tank/wing skin with a 45 degree cut on outside end.

Or a fitting in bottom outboard tank skin with inside tube going to the highest point in the tank (a bit more drag from fitting).

I chickened out and did the conventional RV-4 installation because of these unknowns:

Vent hole could ice over? (no hot engine air passing over vent opening)

RV-4 is a taildragger (is it possible to get inside end of vent line at a point where fuel won't siphon out with full tank tail up and tail down?)

Less drag with inboard vent? (already turbulent air from engine and gear)

I understand the RV-10 has a straight down vent with no loop.

Finn

Larry DeCamp · #16 08-05-2019, 05:12 AM

I have the Rocket/Dye/etc two loop system on 3B. It works very well for me because I normally store the ship with tanks half full. When topped of for travel, I have not noticed anything objectionable ( gas odor). Completely full, sloped ramp or hot sun is ?no win scenario?. That said, Fynnflyer?s idea for outboard vent at the apex of the airfoil would optimize the condition, but only on perfectly level ramp if ?no leakage? is the objective. Just my $0.02.

Mark Dickens · #17 08-05-2019, 05:21 AM

I implemented a slightly different version of this in my -8. Works great. I've never seen a drop of gas in almost 200 hours. I would definitely do it again

mfleming · #18 08-05-2019, 10:09 AM

Quote:

Originally Posted by Mark Dickens

I implemented a slightly different version of this in my -8. Works great. I've never seen a drop of gas in almost 200 hours. I would definitely do it again

Sounds good, what was the slightly different version...Photo??

scsmith · #19 08-05-2019, 05:35 PM

The Lancair folks run the vent line out to the wingtip and then down to an NACA inlet in the bottom of the wingtip to supply some elevated pressure. But also, they put a check valve in the line, so air can get pulled in to replace fuel as it burns, but fuel can not come out the vent.

I don't know if the check valve has a pressure relief function, so that expanding fuel in a full tank in the sun won't overpressure the wing?

If you were to omit the check valve and just run the vent to the tip, as I think FinnFlyer is suggesting, only slight mis-coordinated flight would send a substantial amount of fuel flowing out the vent line. A few moments in a slip with a 5-degree bank and you could lose 1/4 tank!

FinnFlyer · #20 08-05-2019, 07:54 PM

Quote:

Originally Posted by scsmith

The Lancair folks run the vent line out to the wingtip and then down to an NACA inlet in the bottom of the wingtip to supply some elevated pressure. But also, they put a check valve in the line, so air can get pulled in to replace fuel as it burns, but fuel can not come out the vent.

I don't know if the check valve has a pressure relief function, so that expanding fuel in a full tank in the sun won't overpressure the wing?

If you were to omit the check valve and just run the vent to the tip, as I think FinnFlyer is suggesting, only slight mis-coordinated flight would send a substantial amount of fuel flowing out the vent line. A few moments in a slip with a 5-degree bank and you could lose 1/4 tank!

No, no. Just like the newer RVs have a vent line straight down at the tank root rib, I was thinking straight down at the outermost tank rib. Or a 90 degree fitting on the tank bottom facing into the wind, and inside the tank a tube from fitting up to very highest point in the tank. No reason you couldn't coil that tube a few times inside the tank too.

Of course the ultimate in simplicity would be to drill a 1/4" hole in the fuel cap and press a 1/4" tube, bent 90 degrees into the wind, into the cap But that would attract a lot of dirty looks from other RV builders and owners and cost you at least 10 mph top speed.

Finn