fuel tank set up for gas - Page 2 - RC Groups
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Jan 15, 2013, 11:50 PM
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Hot drawing!
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Jan 16, 2013, 04:39 AM
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Reginald's Avatar
Originally Posted by DarZeelon

I believe this is the main justification for using a felt clunk.
It prevents anything but liquid fuel, from going into the fuel-line, until the tank is virtually empty and there's no fuel to soak-up into the felt.
Jan 16, 2013, 06:42 AM
Illegitimi non carborundum
grosbeak's Avatar
Originally Posted by wuest3141
Hot drawing!
Aw, shucks. Thanks.

Originally Posted by pilotpete2
The loop of fuel line on top of the tank goes a long, long way to eliminating the problem, BUT the loop should extend a little beyond the rear of the tank, so the loop will be the highest point in the vent line on downlines.
Makes sense - I'm plumbing a new tank for a new-to-me 50cc plane using a Fiji water bottle and a two-line system. Here's the diagram:

I've heard from a couple of different sources that fibres from the felt clunk may work their way loose and into the supply line. That's what the inline filter is for - insurance. I also have a filter inside my fuel jug.

I have photos of the installation and will post them if there's any interest.
Jan 17, 2013, 05:00 PM
KV4PL, FAA 107 Certified
FloridaFlyBob's Avatar
I did mine with 3 lines

Jan 17, 2013, 06:07 PM

3 lines

What is the benefit of the 3rd line instead of a T in the main line? Brian

Originally Posted by rstekeur
I did mine with 3 lines

Last edited by BrianSmith; Jan 17, 2013 at 06:39 PM.
Jan 17, 2013, 06:33 PM
probro 2567
kwj48's Avatar
Originally Posted by BrianSmith
What is the benefit of the 3rd line instead of a T main line? Brian
Basicly less points of failure.

Personally I like the two line setup better, because while filling your tank you also prime the line to the carb. Less flipping to get the engine choked/started.
Jan 17, 2013, 06:47 PM
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pilotpete2's Avatar
The advantage with the 3 line setup is that it minimizes the connections where air can be drawn into the line to the carb. While I do drain my fuel tanks at the end of the flying session, the fuel in the line between the clunk and carb remains filled with fuel. With gas engines, most folks do not run them dry after the last flight of the day to keep the gaskets in the carb wet and to eliminate the need to prime the engine.
One other note. The fill/drain line on a 3 line setup should be mounted higher than the top of the tank, never on the bottom of the plane
Jan 18, 2013, 08:37 AM
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Pete has a valid point with the Fill / Drain assessment.

A) It would be a point of failure if that were to open during flight or if it were leaking due to any reason; bad line, maybe someone forgets to cap it after fueling, vibrating loose, etc.

B) Also for ease of access: Easier to see and connect / dis-connect for service if mounted on the side or top of plane .... still higher elevation than the tank though.
Feb 25, 2013, 09:13 PM
Team PAS
purcilas's Avatar
Even cheaper Viton: http://www.zorotools.com/g/00057078/...azonProductAds
Feb 28, 2013, 02:12 PM
KV4PL, FAA 107 Certified
FloridaFlyBob's Avatar
Don't forget to use fuel barbs on all your lines as the tygon expands with age and can come off.

Mar 01, 2013, 12:44 AM
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kerwin50's Avatar
I like a 3 line set up with a felt clunk mainly because of the flitering
Mar 01, 2013, 01:44 AM
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I use neoprene tubing, it works with gas and you can get it at any auto parts store. I have some on my plane for 3 years no problem.
Mar 01, 2013, 02:04 AM
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DarZeelon's Avatar
Originally Posted by kerwin50
I like a 3 line set up with a felt clunk mainly because of the filtering.

Actually, Kerwin, filtering is only the fringe benefit...

The leading virtue of the felt clunk, is its ability to soak the tank dry and to perform bubble free fuel delivery, to the last cc in the tank.
Mar 04, 2013, 05:46 AM
Registered User
Watch out with an 11 oz fuel tank (20cc engine). The gas Tygon tubing is stiff, and so with the clunk falling in the bottom rear of the tank, the last of the gas will run to the FRONT of the tank when you stick your nose DOWN to come in to land. I sucked air coming in to land, and bushed a plane, even though the tank was not empty.

I have gone to 16oz tanks for a 20cc gas engine.

I like the drawing above. This is a good setup for tubing. The T going to the clunk and engine is vital, so that you do not have to hink around pulling off tubing to refuel.
Mar 07, 2013, 01:32 AM
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DarZeelon's Avatar

They say here Viton® tubing does a much better job of following the fuel in the tank.

It is significantly more flexible.
Last edited by DarZeelon; Mar 07, 2013 at 06:38 AM. Reason: Typo...

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