George, George, George....We're not as dumb as we look! The vent line is terminated just like Van's design. I used an AN fitting in the bottom of the wing skin that overlaps the end rib.gmcjetpilot said:One thing I would say is a must is you vent to the outside. I am not sure as I said but think the Rocket method (coil in wing root) may not vent out and just terminate in the wing root. Not sure how they do it, but that's a bad idea and could potentially lead into fuel in the cockpit in my opinion. G
Randy, Randy, Randy, no one said you are dumb. You seem to be very sensitive to my post? I am so sorry if I offended you, the Rocket community or who ever else you referred to as "We're". You're smarter, so forgive my ignorance. You seem to be very proud (defensive) of anything "Rocket". For the record if you read what I wrote I did not say this vent would not work acceptably.f1rocket said:George, George, George....We're not as dumb as we look! The vent line is terminated just like Van's design. I used an AN fitting in the bottom of the wing skin that overlaps the end rib.
GGGGGGGGGGf1rocket said:Yikes
yep,ptrotter said:Mike,
I think there might be a problem with that. I think you would drain fuel pretty fast from the low tank when at even a slight angle.
You need the coils and the drain at the opposite ends of the tank from the inside end of the vent tube. By putting the coils at the root end, either the drain is higher than the fuel if the wing is low, or the end of the vent tubing is higher than the fuel in the tnk if the wing is high.
I think the main reason for the coils is to prevent fuel loss due to air expansion in the tank when the tank is full enough that the inside end of the vent tube is below the fuel line.
mlw450802 said:If vertical height is an issue, just make sure all the vertical up portions of the coils add up to the vertical height of VAN's stock vent.
What say you experts?
Actually there are two flow modes here with drastically different results. If the flow is fast enough to fill the tube then your statement is correct but if the flow is slight and the fuel spills over the tops of the coils in a trickle, only the up slopes will fill and they will begin to add in height and, since the down slopes will be full of air minus the small trickle going down the wall, the additive heights will be essentially equivalent to lifting the fuel up a single long lift, requiring more and more pressure to traverse more and more coils.szicree said:I'm no expert, but this doesn't work out. If the pressure is adequate to get the liquid through one loop, it'll push it through as many as you like (assuming the pressure stays constant). On the other hand it'll take more and more pressure to pump liquid higher and higher. The multiple loop thing relies on the fact that as the fuel moves into the loops, it relieves some pressure behind it so that it would rarely get to the end.
mlw450802 said:Actually there are two flow modes here with drastically different results. If the flow is fast enough to fill the tube then your statement is correct but if the flow is slight and the fuel spills over the tops of the coils in a trickle, only the up slopes will fill and they will begin to add in height and, since the down slopes will be full of air minus the small trickle going down the wall, the additive heights will be essentially equivalent to lifting the fuel up a single long lift, requiring more and more pressure to traverse more and more coils.
As unlikely as it sounds, it is true.
mlw450802 said:Actually there are two flow modes here with drastically different results. If the flow is fast enough to fill the tube then your statement is correct but if the flow is slight and the fuel spills over the tops of the coils in a trickle, only the up slopes will fill and they will begin to add in height and, since the down slopes will be full of air minus the small trickle going down the wall, the additive heights will be essentially equivalent to lifting the fuel up a single long lift, requiring more and more pressure to traverse more and more coils.
As unlikely as it sounds, it is true.
I said it seems unlikely but it's an easy experiment. Attach a pressure gage to the source and start with a transparent tube large enough in diameter to allow unfilled flow. Start trickling the water into the coiled tube and pressure will increase to 6 inches WC (in your example) it will then spill over the top of the first coil and will fill the bottom of the second, trapping air in the down going section. As the water continues to flow, the upslope will fill on the second coil increasing pressure to ~ 12 inches WC this will continue as you add coils. The amount is not exactly additive because each section of coil with the trapped air will compress slightly proportional to the number of down stream coils that are filled on their upslopes. The caveats are that you have to start with an empty tube and the flow rate has to be slow enough to not create filled flow. Kind of like the flow you might expect due to thermal expansion of the fuel in your tanks.szicree said:I ain't buyin' this. Let's suppose there's enough pressure to lift the fuel a distance equal to the diameter of the loop. As soon as the fuel reaches the top of the loop, a little spills over the top and settles in the bottom of the next. This spilling will continue since the pressure is still adequate to keep the first loop full (1 diameter's worth of pressure). The fuel that is settling in the bottom of the loop will continue to fill symmetrically on both the downward and upward sides of this loop until it reaches the top, at which time it will begin spilling into the next one. This will continue until the pressure drops below the 1 diameter level. You suggest that the liquid will fill only the upward sides of each loop. This might sound right on paper, but having just tried it in my kitchen sink with vinyl tubing I can tell you that it just doesn't work. What I can say is that the same amount of pressure that sends water through one loop, sends it through 5. On the other hand this same amount of pressure is completely inadequate to push the water straight up the equivalent sum of even 2 diameters. Try it yourself. If the loops really do add up then I could take a couple hundred feet of garden hose all coiled up on a hose reel, hook it up to the faucet, turn it on and get nothing. I've never tried it, but my gut says if I wait a few seconds I'd get water. I'm not itching for an argument, but my kitchen sink science experiment tells me that 5 six-inch diameter loops is not the same as a 30 inch climb.