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  #1  
Old 06-30-2015, 08:23 AM
cwharris cwharris is offline
 
Join Date: Jul 2014
Location: Meridian, MS
Posts: 75
Default Float/Capacitance fuel sending units

I?m about to start on my tanks and so I was wondering if I can install BOTH the Float Style Sending Units that come with the Wing Kit and also install a Princeton Capacitance fuel probe sending unit. I would use the Probe units as my primary sending units that would get wired into my EFIS System and then I would wire the Float Style Units that come with the kit to a stand-alone back up fuel Gauge. Has anybody tried to install both types of sending units? Is this something that I should do or not do?
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RV-14A Kit S/N 140175
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  #2  
Old 06-30-2015, 08:33 AM
Tom023 Tom023 is offline
 
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Check E's blog:

http://rv-14a.blogspot.com/search/la...l%20Probes?m=0
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  #3  
Old 06-30-2015, 09:00 AM
Mike H Mike H is offline
 
Join Date: May 2014
Location: Savannah
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What advantage do the capacitive fuel probes give you over the standard float senders?
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  #4  
Old 06-30-2015, 09:31 AM
Icarus Icarus is offline
 
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Location: D.C.
Posts: 306
Default ...

In theory? Less susceptible to variance due to disturbance of the fuel in flight. No moving mechanism.

In practice? Having flown a mix of aircraft with both, I still seem to ignore gages and stick the tanks. If you're building now, why not. I would much rather prefer a good fuel totalizer. [Which reminds me...the D-10EMS is on the way ! ]

Now...if you could build in a cork sight gauge a la stearman/cub...
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Last edited by Icarus : 06-30-2015 at 10:20 AM.
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  #5  
Old 06-30-2015, 01:32 PM
Mike H Mike H is offline
 
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Location: Savannah
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I know the capacitive senders sound good in theory, and I know lots of builders go this route, I am just not sure if it is a better way of doing things in our application. Capacitive systems are the onLy way to go due to the design characteristics of some aircraft fuel cells, but not so much our small tanks. Capacitive fuel quantity systems require maintenance eventually. Even though there are no moving parts all it takes is some oxidation on the electrical connections to cause some wildly erratic or inaccurate indications. Capacative systems are not tolerant of imperfect connections, crimps, soldering of coax center conductor pins, shielding, FOD and many other variables. Eventually you will have to clean and re-tourque, or reterminate connections, and to be able to accomplish this you will need access to the inside of the tank. Access inside of the -14 and -10 tanks requires cutting and installing access panels in the rear tank wall.
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Last edited by Mike H : 06-30-2015 at 01:52 PM.
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  #6  
Old 06-30-2015, 04:34 PM
rightrudder rightrudder is offline
 
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Location: Laguna Hills, CA
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Quote:
Originally Posted by Icarus View Post

In practice? Having flown a mix of aircraft with both, I still seem to ignore gages and stick the tanks.
Smart move. I have a healthy mistrust of fuel gauges too. Sticks don't lie!
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  #7  
Old 06-30-2015, 09:10 PM
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N941WR N941WR is offline
 
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Go with the capacitance senders and use your fuel flow and watch as your backups.

I have the Dynon SkyView with their capacitance senders and am always amazed at how accurate they are!
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  #8  
Old 06-30-2015, 10:10 PM
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rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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With the current technology we have in EFIS with the calibrated/mapped fuel levels, all the systems are very accurate when they are working.
Any of the different system types can fail.
Once we got rid of the wire wound resistor fuel level sensors the reliability seemed to go up.
I have maintained a large # of RV's for many years (currently 8 airplanes) and in that time I have replaced one mechanical fuel level sensor.
Of the problems I have heard of that others have had probably half of them are self induced (damaged during installation, etc.).
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  #9  
Old 06-30-2015, 11:44 PM
cwharris cwharris is offline
 
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Location: Meridian, MS
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Thanks for all the input. Looks like I'm sticking with the Float Sending Unit that comes with the kit. Thanks again.
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  #10  
Old 07-01-2015, 12:01 AM
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Snowflake Snowflake is offline
 
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Having now flown with a red cube measuring fuel flow, and having seen how accurate flow measurement can be, I don't think i'd put level senders in tanks at all if I could avoid it. One red cube in each wing root, dip the tanks before each flight, and you'll know fuel level more than accurately enough for VFR operations. The only downside is that it requires remembering to set the totals when you fill or top up the tanks.
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