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  #11  
Old 12-29-2018, 02:18 PM
NinerBikes NinerBikes is offline
 
Join Date: Dec 2018
Location: Granada Hills
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Bob, this is something we need to verify in your 2015 RV-12. Very valuable thread, thanks to all that have contributed.
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  #12  
Old 12-31-2018, 10:41 AM
AirHound AirHound is offline
 
Join Date: Oct 2006
Location: OFallon IL now, everywhere before
Posts: 275
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Quote:
Originally Posted by Piper J3 View Post
I have four ways to determine fuel quantity before flight: Moeller, sight-gage on side of tank, Dynon D-180, and dip stick.

The only one I completely trust is the dip stick Ė very accurate / never liesÖ
Jim,
Did you make your dip stick? If so, any specs you can share?

Thanks and Happy New Year!
Doug
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  #13  
Old 12-31-2018, 10:47 AM
AirHound AirHound is offline
 
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Quote:
Originally Posted by rvbuilder2002 View Post
This is not a problem with the RV-12 (and not exclusive to the RV-12 either... all of the other RV models have gauges that can't read the upper 4 gallons or so because of wing dihedral). When is it that important to have a absolute gauge indication of the first 3 or 4 gallons that get used. The important thing is for accuracy at that last 3 or 4 gallons. The RV-12 tank does well with this.

A long / full span skinny tank in the wing with the dihedral tilt will be effected even worse than any of the other RV's are.
Scott,
I didnít build my 2012 RV-12. Was wondering if the occasional strong fuel pump gas stream can neg impact fuel tank floats/innards/accuracy?

Thanks and Happy Flying New Year!
Doug
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  #14  
Old 12-31-2018, 11:51 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by AirHound View Post
Scott,
I didnít build my 2012 RV-12. Was wondering if the occasional strong fuel pump gas stream can neg impact fuel tank floats/innards/accuracy?

Thanks and Happy Flying New Year!
Doug
I don't know if I understand your question correctly, but if you mean a high velocity stream from a fuel nozzle having a neg. effect on the fuel tank and sender? No, I am not aware of any problem caused by that. I don't see how it would be possible since the filler tube makes the fuel enter the tank pretty much straight down at the back of the tank but both of the fuel level floats are well fwd in the tank.
A change in fuel gauge accuracy is usually caused by an increase in resistance between airframe ground and the mounting flange (ground path) of the fuel level sender.
The RV-12iS redesign included adding a ground wire between the airframe and one of the sender mounting screws, to help mitigate this problem.
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RV-6A (aka "Junkyard Special ")
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  #15  
Old 12-31-2018, 12:57 PM
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Piper J3 Piper J3 is offline
 
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Location: Hinckley, Ohio
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Quote:
Originally Posted by AirHound View Post
Jim,
Did you make your dip stick? If so, any specs you can share?
The stick is wood approx 1/8" x 3/8" x 36". The end that gets inserted into the tank is pointed so it can sneak around the fuel return tube at the base of the filler neck. Start with empty tank and fill with 2 gallon increments each time inserting the stick and marking the level with a graphite pencil. Dead nuts...
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Hinckley, Ohio
EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N68203
1130 hrs Flying 46 Piper J-3 Cub N6841H
RV-12 E-LSA #120058 AWC July 2012 N633CM
RV-12 Bought Flying Oct 2015 with 48TT - Hobbs now 409

LSRM-A Certificate 2016
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  #16  
Old 12-31-2018, 08:00 PM
RFSchaller RFSchaller is offline
 
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Location: Phoenix, AZ
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I did what Jim did and used flexible translucent tubing. Although the shape of the tank isnít a uniform cube I found that once youíre past the sloped tank floor it was pretty much one gallon to the inch. I got 20 gal into my tank, but that filled most of the filler neck so as soon as the fuel started filling the neck the linearity shifted. Iíll check my dimensions on the marks when Iím at the hangar on Wednesday and post them.
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  #17  
Old 02-03-2019, 03:45 AM
VHRV12 VHRV12 is offline
 
Join Date: Apr 2009
Location: Melbourne, Australia
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Quote:
Originally Posted by rvbuilder2002 View Post
I don't know if I understand your question correctly, but if you mean a high velocity stream from a fuel nozzle having a neg. effect on the fuel tank and sender? No, I am not aware of any problem caused by that. I don't see how it would be possible since the filler tube makes the fuel enter the tank pretty much straight down at the back of the tank but both of the fuel level floats are well fwd in the tank.
A change in fuel gauge accuracy is usually caused by an increase in resistance between airframe ground and the mounting flange (ground path) of the fuel level sender.
The RV-12iS redesign included adding a ground wire between the airframe and one of the sender mounting screws, to help mitigate this problem.
Hmmm that,s interesting Scott, I have just calibrated the fuel tank sender in my 12 with Skyview and a standard 19.8 US Gal tank and had trouble getting good figures with nice voltage "steps". Next time I turned the power on the fuel quantity was blank. Turn out to be a poorly grounded sender. Made a 12" jumper with a couple of ring lugs, grounded to sender mounting screw with an MS35338-38 star washer and plenty of goop and the other end to the conduit P Clamp on the spar carry thru... Perfect!
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  #18  
Old 02-03-2019, 11:00 AM
NinerBikes NinerBikes is offline
 
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Some observations here in Southern California, where we fly the RV-12 year round.

Moeller doesn't start registering off of full until 4 to 5 gallons are burned off. That leaved the Moeller having a range of your last 15 or 16 gallons. Last 2 fillups, the Moeller was showing smack dab a half a tank left. Fillups were 12.2 and 11.7 gallons, brimmed to maybe 2 inches short of the top of the fillup neck. So ABOUT 8 gallons left, when the Moeller shows half a tank.

The prop on this plane is tuned not for climbing but for cruising. At 1300 # with both of us 5000 ASL, throttle to the wall, we see 5250 to 5300 rpm, level flight, max. LL100, will burn just over 5 gallons an hour at 112 kt IAS. For some reason, Mogas seems to give another 60 to 80 more rpms at full throttle? Just observations.

Any ideas why more rpm on the Mogas, greatly appreciated. Perhaps the Rotax, being designed for Mogas and the lower octane, makes more torque due to the burn characteristics of the flame front of Mogas?

Just a FYI.... as always YMMV, trust, but verify, this is but one data point of many.

Last edited by NinerBikes : 02-03-2019 at 11:02 AM.
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  #19  
Old 02-03-2019, 11:38 AM
pilotyoung pilotyoung is offline
 
Join Date: Jan 2018
Location: Birmingham, AL
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Jim,

Is there any reason a dowel rod could not be used to measure and mark the fuel quantity in the tank?
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Serial Number 120022, N6812Y
Bought it as a flying airplane in Feb. 2018
Just passed 100 hours flight time in RV-12, and 10,000 hours mostly in corporate jets. I am a CFI; CFII; MEI; and a advancd Ground Instructor, CFIG; and hoping to be able to help new RV-12 owners by doing some transition training for new builders and owners in RV-12's.
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  #20  
Old 02-03-2019, 12:46 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by NinerBikes View Post

The prop on this plane is tuned not for climbing but for cruising. At 1300 # with both of us 5000 ASL, throttle to the wall, we see 5250 to 5300 rpm, level flight, max. LL100, will burn just over 5 gallons an hour at 112 kt IAS. For some reason, Mogas seems to give another 60 to 80 more rpms at full throttle? Just observations.

Any ideas why more rpm on the Mogas, greatly appreciated. Perhaps the Rotax, being designed for Mogas and the lower octane, makes more torque due to the burn characteristics of the flame front of Mogas?
Your prop isn't pitched for cruising.... it is over pitched.
This will have a negative effect on oil temp in hot weather and can cause other problems (besides giving up climb performance that you don't have to).

I have no comment on the RPM difference. I have never seen any indication of a change with fuel type. My guess is that you are seeing differences with different weather conditions (density altitude).
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RV-6A (aka "Junkyard Special ")
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