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Old Jan 06, 2013, 08:12 AM
SWAMPER is offline
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fuel tank set up for gas


ok this is my first gas set up so have a question i got a 20cc engine and fit a 16oz tank and my question is do gas set ups run a pressure line to the muffler ? the muffler has no pressure tap so do i need to add one if not what do i do with the vent line ?

thanks for the help
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Old Jan 06, 2013, 08:19 AM
earlwb is offline
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Normally one does not use muffler pressure with a gasoline engine setup. I suggest using a three line setup for the fuel tank, one line is the fuel line, one line is for the vent and the third line is for refueling and defueling the fuel tank. I use a large loop or two for the vent line so that the fuel doesn't siphon out if the plane is inverted.

The gasoline engines use a pump carburetor so they do not need muffler pressure. You can pretty much place the fuel tank any place inside of the airplane as the pump in the carb draws the fuel for the engine and provides the fuel at a constant pressure via the fuel regulator to the engine.
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Old Jan 06, 2013, 08:21 AM
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Muffler pressure


No.. No muffler pressure needed. Gas carbs have pumps in them and no help needed to draw the gas.. A lot of folks have their way of doing it, but I put a T in the line from the tank to the carb to fill and empty the tank with and a vent line out the bottom of the model. Brian


Quote:
Originally Posted by SWAMPER View Post
ok this is my first gas set up so have a question i got a 20cc engine and fit a 16oz tank and my question is do gas set ups run a pressure line to the muffler ? the muffler has no pressure tap so do i need to add one if not what do i do with the vent line ?

thanks for the help
Last edited by BrianSmith; Jan 16, 2013 at 07:40 AM.
Old Jan 10, 2013, 08:11 AM
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Don't foget the fuel line and rubber stopper in the tank. They need to be gas safe. Dubro makes a red rubber stopper that is gas safe and saleTygon tubing for the fuel lines. With gas engines you will need to change your internal tank line about every 6 months to year. Buna fuel line inside the tank probabaly works better than Tygon.
Old Jan 10, 2013, 09:07 AM
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As a side note on vents.... Many if not most of the new trimmers, leaf blowers etc. use a one way valve to control vapor coming from the fuel tank. It lets air in but nothing coming out. It might be something to explore???

Ken
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Old Jan 10, 2013, 09:18 AM
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when we first ran smoke,we used an empty metal fuel filter with a BB in it..The filter is the type that opens for cleaning...We removed the screen and added the BB (or ball bearing).When the tank pressure became negative while running , it lifted the ball enough to allow the tank to vent..
It was our way of preventing leakage when at rest. The filter must be mounted vertically,and it seals when inverted also.
The newer 'check valves' prevent gas odor and spillage inside storage areas.
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Old Jan 10, 2013, 10:59 AM
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Viton is the stuff to use inside the tank. Tygon is good for the rest of the system but it does harden and will require periodic replacement.

You can use a three line system as described, or a two-line system where the fuel fill joins the engine supply line with a T fitting, like so:



Looping the vent line over the top of the tank and down the side will prevent gas from leaking out the vent line when you don't want it to.
Old Jan 10, 2013, 11:59 AM
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The idea of using a one way valve to prevent fuel draining on downlines sounds good, BUT, it can make for problems filling the tank.
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.

SWAMPER,
A 16 oz. tank is an awful lot of fuel for a 20cc gas engine. This another thing about gas engines you'll really get to like!
My last gas conversion of a glow bird to 20cc gas could only take a 10 oz. tank when I relocated the tank to make room for the ignition module. I flew 12 minute flights with that setup and had plenty of fuel left at the end of a flight
Best of luck with your first gasser!
Pete
Old Jan 10, 2013, 12:09 PM
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I like using the third line to avoid introducing air bubbles into the fuel inlet line going to the carb. Sometimes those pesky air bubbles can cause a lot of hassle getting them out of the carb. You know holding the airplane at different attitudes with the engine running to work them out. Having an air bubble stall the engine on take off is a bummer.
But I do have a couple of planes setup with just a two line fuel tank along with a Tee for refueling or draining the tank.
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Old Jan 10, 2013, 12:32 PM
DarZeelon is offline
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Quote:
Originally Posted by earlwb View Post
I like using the third line to avoid introducing air bubbles into the fuel inlet line going to the carb. Sometimes those pesky air bubbles can cause a lot of hassle getting them out of the carb. You know holding the airplane at different attitudes with the engine running to work them out. Having an air bubble stall the engine on take off is a bummer.
But I do have a couple of planes setup with just a two line fuel tank along with a Tee for refueling or draining the tank.
Earl,


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.
Old Jan 10, 2013, 12:57 PM
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Viton


Where are you seeing/getting Viton? Thanks Brian


Quote:
Originally Posted by grosbeak View Post
Viton is the stuff to use inside the tank. Tygon is good for the rest of the system but it does harden and will require periodic replacement.

You can use a three line system as described, or a two-line system where the fuel fill joins the engine supply line with a T fitting, like so:



Looping the vent line over the top of the tank and down the side will prevent gas from leaking out the vent line when you don't want it to.
Old Jan 10, 2013, 03:01 PM
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I get my Viton from Thunderbolt RC here in Canada - I highly recommend them. I bet they'd even ship to the States if you asked them nicely.

In the US, I found some for sale at Red Aero RC.
Old Jan 10, 2013, 06:44 PM
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i always use a check-valve in the vent line along with a T to open it up while fueling.
Old Jan 10, 2013, 09:02 PM
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Quote:
Originally Posted by BrianSmith View Post
Where are you seeing/getting Viton? Thanks Brian
Several more sources for Viton. BTW a 16oz. fuel tank should give you a lot of flight time. I have a 12oz. tank for my dle 20 and can get almost 20 min.

http://www.pspmfg.com/

http://www.shop.kavarootusa.com/prod...&categoryId=19
Old Jan 13, 2013, 01:19 AM
Fokker DII is offline
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I buy my Viton here. They have really good prices and size selection.

http://www.mcmaster.com/#viton-fluor...tubing/=l0gwv6


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