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-   -   Fuel tank Air vent. (http://www.vansairforce.com/community/showthread.php?t=151418)

LUKLA 07-14-2017 07:42 PM

Fuel tank Air vent.
 
Just curious.
Is any one has done your air vent differently than just making #30 hole in the fuel cap on RV12 gas tank.
I have heard there is new way ppl are doing but haven't seen any picture or schematic or instruction.
input will be appreciate as always.

LUKLA

Slane 07-14-2017 08:10 PM

Fuel tank air vent
 
See section 37: http://www.vansaircraft.com/pdf/revi...Section_37.pdf

2johns 07-14-2017 08:30 PM

I think it is a very good idea to change the fuel vent location as Van's has suggested in 37-01 Rev 5 due the possibility of the hole in the cap being plugged or a new owner being unaware of the hole in the cap, losing the cap, replacing it with a new one without drilling the the vent hole. A possible cause of a disaster. I made the revision moving the vent to the top of the tank. Only problem was that I have an automatic shut off and when it shuts off, a small amount of gasoline would spew out the new vent onto the floor. Why, I do not know. I then moved the vent an inch or so below the top of filler neck and plugged the fitting on the top of the tank using the same vent outlet location on the bottom of the fuselage to solve this problem.

scottmillhouse 07-15-2017 10:28 AM

I recommend having both vents, the new tank and the cap. I initially built mine without the cap vent and was having variable fuel pressure when the tank was filled. Put a vent hole per instructions in cap and no problem the last 100 hours.

Phantom30 07-15-2017 11:51 AM

Quote:

Originally Posted by scottmillhouse (Post 1188061)
I recommend having both vents, the new tank and the cap. I initially built mine without the cap vent and was having variable fuel pressure when the tank was filled. Put a vent hole per instructions in cap and no problem the last 100 hours.

Very interesting....me thinks I'll try that as I've seen changing (lowering) fuel pressure as fuel is consumed (and I know my vent works as fuel runs out if I overfill tank)...

Scott...where would find instructions on how to drill vent hole in cap?

Piper J3 07-15-2017 03:45 PM

Actually I subscribe to the vented cap all by itself. I use 93E10 auto fuel exclusively and donít want a lot of air exchange in the tank. Alcohol is very hydroscopic and will absorb moisture in the air. Also, octane rating for auto fuel will diminish if not stored in a sealed container.

So I run a cap with the small vent hole and have had zero problems in 258 hours. When I did the fuel tank SB I elected to not install the new vent system. Fuel pressure and fuel flow are rock steady regardless of fuel quantity.

LUKLA 07-15-2017 04:43 PM

Quote:

Originally Posted by Piper J3 (Post 1188114)
Actually I subscribe to the vented cap all by itself. I use 93E10 auto fuel exclusively and donít want a lot of air exchange in the tank. Alcohol is very hydroscopic and will absorb moisture in the air. Also, octane rating for auto fuel will diminish if not stored in a sealed container.

So I run a cap with the small vent hole and have had zero problems in 258 hours. When I did the fuel tank SB I elected to not install the new vent system. Fuel pressure and fuel flow are rock steady regardless of fuel quantity.

So verdict is Just make # 30 hole in fuel cap and it will do perfect !!!

Thanks a lot Folks.
Lukla

DHeal 07-15-2017 05:04 PM

I have the Van's early plan's holes in the fuel cap. It seems to be working fine for me over 500+ hours. Just be sure that as part of your pre-flight that you remove the cap and blow air (breath) through the holes to ensure that they are free and clear of debris, bugs, etc. Also, during outside exposure to rain, I tape a piece of plastic sheeting over the cap that is positioned to keep rain out of the cap area yet would blow away in the prop wash if I were to forget to remove it before flight.

RFSchaller 07-15-2017 06:35 PM

I do the same as David. 600 hours and 5 years later the vented cap still works great.

DBRuth 07-15-2017 06:42 PM

Double vent
 
I also have the new style vent system and the vented cap. I drilled mine to the tap size for 4-40 and then tapped both the cap and the lower plate 4-40, just in case I didn't like the results. I had a couple of flights when I smelled fuel on climb out before I vented the cap, and none since vented. Needless to say I have not had to block off the cap vent. 117 hours total, approximately 100 hours with both vents,no problems.


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