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Offline ROLLERMAN  
#1 Posted : Tuesday, March 12, 2019 5:47:06 PM(UTC)
ROLLERMAN

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OK, I wish I could take credit for this idea but I can’t. I was told about this from out Miami IMAC friends, this set up would eliminate any fuel from being dumped out in any attitude your plane may be in. I am sure you all have seen the trail of vapor when doing inverted maneuvers; with this set up any fuel exiting the main tank will be capture by the small one, here is the trick, due to the straight brass tubing on the small tank the fuel cannot escape, Just genius. I got an extra 5 minutes of flight time by doing this AND the bottom of the plane stays cleaner.

Here is a diagram of the set up.

Tank Set up.JPG (69kb) downloaded 9 time(s).
thanks 2 users thanked ROLLERMAN for this useful post.
Krzy4rc on 3/12/2019(UTC), RVC on 3/12/2019(UTC)
Offline Brad  
#2 Posted : Tuesday, March 12, 2019 7:29:48 PM(UTC)
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Put the vent line out the bottom and add a loop to the vent line on top of the fuel tank. It will form a loop seal that allows air in, prevents fuel dumping when inverted, and then sucks the fuel back into the tank when upright. Same effect, fewer components, less weight.

Brad
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Gil R. Major on 3/14/2019(UTC)
Offline Dangerous Dan  
#3 Posted : Wednesday, March 13, 2019 5:42:40 AM(UTC)
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5D04DDA4-986A-4443-B7E3-626AA11C940A.jpeg (1,936kb) downloaded 4 time(s). 5143C2B7-A1B7-4938-868B-9E430A9FA62D.png (2,120kb) downloaded 3 time(s).


I’m setup. Nothing of those methods 2 1L tanks directly over CG
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The answer to all questions lies in the bottom of your fuel can, and in your plane setup
Offline Doug Pilcher  
#4 Posted : Wednesday, March 13, 2019 5:47:13 AM(UTC)
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Originally Posted by: Brad Go to Quoted Post
Put the vent line out the bottom and add a loop to the vent line on top of the fuel tank. It will form a loop seal that allows air in, prevents fuel dumping when inverted, and then sucks the fuel back into the tank when upright. Same effect, fewer components, less weight.

Brad


Have to agree with Brad. "KISS"
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thanks 1 user thanked Doug Pilcher for this useful post.
Gil R. Major on 3/14/2019(UTC)
Offline Tim Hughes  
#5 Posted : Wednesday, March 13, 2019 7:05:06 AM(UTC)
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Originally Posted by: Brad Go to Quoted Post
Put the vent line out the bottom and add a loop to the vent line on top of the fuel tank. It will form a loop seal that allows air in, prevents fuel dumping when inverted, and then sucks the fuel back into the tank when upright. Same effect, fewer components, less weight.

Brad

Some photos please. If the fill and vent are on the same side, could you just turn it to the bottom and get the same results?

Tim
Offline Brad  
#6 Posted : Wednesday, March 13, 2019 7:33:07 AM(UTC)
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Here’s a quick sketch. Sorry about the orientation, but limited ability to edit on my phone.

When upright, normal vacuum from the engine pulls air in through the vent line.

When rolling to inverted, if fuel enters the vent line, it is captured by the loop seal. When fully inverted the vent exit is above the fuel tank, this prevents fuel dumping out. When rolling back to upright any fuel in the loop seal is drawn back into the fuel tank. On knife edge the loop seal captures fuel in the loop just like when rolling to inverted.

Although not clear in the drawing, the loop just lays flat on top of the fuel tank. That's what allows it to work properly in knife edge and when rolling to inverted. If you put it on the side of the tank with a vertical orientation, you risk reducing fuel draw slightly if fuel is caught in the loop in an upright or inverted orientation.

Brad
Offline Doug Pilcher  
#7 Posted : Wednesday, March 13, 2019 8:18:21 AM(UTC)
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Offline ROLLERMAN  
#8 Posted : Wednesday, March 13, 2019 8:20:34 AM(UTC)
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I used a 4oz Dubro tank, 1,52 oz. Weight is not an issue. The system I had was very close to what Brad is showing, only difference was I had a separate line to fill, I had two full loops and still had fuel coming out. The issue I have had and seen is that if you have a leak on the fill line, it will pull air in causing dead sticks, (ASK ME HOW I KNOW) LOL!

Many ways to skin a cat, The set up I have now seems to be working great, just find one that you feel comfortable with and go with it.

Wheels down on landing boys,

IMAC ART IN THE SKY!

Primo

Offline skipm  
#9 Posted : Wednesday, March 13, 2019 10:04:39 AM(UTC)
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I have tried multiple configurations of vent line loops and always had fuel getting out. I've been using a 2oz catch tank and loop with good success for a couple of seasons now and I like it. It's surprising how much fuel gets past the loop into the tank by the end of the flight and it is sequence dependent. If the maneuvers are in phase with the rotation of the loop it will transport the fuel thru the line and out. It will auto drain as the plane cools down after the flight.

Skip
Offline Steve Sides  
#10 Posted : Wednesday, March 13, 2019 11:23:22 AM(UTC)
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I've also tried the loop thing and never was successful. Went to a 2 oz vent tank on the vent line of the main tank and have not had a problem. The bottom of my aircraft has absolutely no oil on it. I always had an oil residue with the loop setup.
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