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  #21  
Old 04-08-2021, 02:52 PM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
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Quote:
Originally Posted by Piper J3 View Post
I would guess there is plenty of cool air ingested during flight. It's the ground ops that cause elevated carb body temp and elevated temp of the fuel in both hoses feeding the carbs and the fuel in the float bowls themselves.
I don't disagree.
And like I said that is a problem to some degree with just about every 912 powered airplane that has a full / at least somewhat aerodynamic cowl.

If proper fuel and ground procedures (the aircraft documentation recommends the oil door be left open in hot temperatures when parked on the ground to vent the engine compartment) are used, it is generally not a problem.
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Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

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Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #22  
Old 04-08-2021, 02:56 PM
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A quick question then… Are the louvers in the 12iS top cowl for add’l cooling? Or are they there to make it look like a Buick Electra 225 (Deuce & ¼)?
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #23  
Old 04-09-2021, 08:12 AM
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Piper J3 Piper J3 is online now
 
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Speaking about engine failures… Paul Bertorelli (AVweb) mentions Rotax leads Lyc and Cont in this category. The comparison is done in overall failures per 1000 engines produced.

See video at 19:30

https://youtu.be/mwpzTnLC8BY
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #24  
Old 04-09-2021, 09:37 AM
rvbuilder2002's Avatar
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by Piper J3 View Post
A quick question then… Are the louvers in the 12iS top cowl for add’l cooling? Or are they there to make it look like a Buick Electra 225 (Deuce & ¼)?
Both

Style sells

Seriously, they are for cooling but not in the same context as you are questioning.

Rotax has some very specific specification requirements for the design of a 912iS engine installation. Many of them are requirements for max. temp of electrical components.
That is the purpose of the louvers on a 12iS. Ground cooling of the ignition coils (they are located directly under the louvers).

BTW, we are very proud of the design of the engine installation on the 12iS.
It 100% meets all of Rotax's requirements (I am not sure that all manufacturers can truthfully say that).
We put a LOT of effort into that and the higher ups in Rotax were quite impressed with the design when it was introduced at OSH 2017, and they requested the opportunity to do a photo shoot with the cowl removed.

There are also design requirements for the 912ULSl, and we put an equal amount of effort into meeting all of those as well.
__________________
Opinions, information and comments are my own unless stated otherwise. They do not necessarily represent the direction/opinions of my employer.

Scott McDaniels
Van's Aircraft Engineering Prototype Shop Manager
Hubbard, Oregon
RV-6A (aka "Junkyard Special ")
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  #25  
Old 04-09-2021, 10:26 AM
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Quote:
Originally Posted by rvbuilder2002 View Post
Style sells
Scott –

Thanks for response. Glad I could add some levity to your day.

You’re probably too young to have experienced the real heavy iron out of Detroit... ’59 was a big year (read: big fins) for Cadillac (vertical) and Chevrolet (horizontal). The North American F-86 Sabre was a huge influence on US automotive design in that era.

Good to see Van’s Aircraft prescribes to Form follows Function.

Have a great weekend…
__________________
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H

Last edited by Piper J3 : 04-09-2021 at 10:32 AM.
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  #26  
Old 04-12-2021, 12:06 PM
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Default Carb Temp Sensing...

I bought a two-channel temperature sensor with 1-meter thermocouples on Amazon for $13.99 (obviously, non-certified at this price point). I intend to temporarily install using 3M double-sided tape to bottom of instrument shelf and operate with 9V alkaline battery. Thermocouples will press against carb float bowl and be pinched between bail wire that fastens float bowl in place. I’ll use some thermal paste to get good thermal conductivity. If unit looks durable, I may install in the instrument panel and upgrade thermocouple leads to Type-K with fiberglass encased wire.

Since experiencing vapor lock power loss/severe vibration last week on climb-out, I’m a little anxious about flying in Spring weather conditions when OAT is warm. This is an attempt to get real-world fuel temperatures during ground ops to see if vapor lock can be foreseen before it becomes imminent.

I get the idea of using 100LL or mixing avgas/mogas to raise vapor pressure. I fly from a private strip so I’d have to fly to local airport to fuel. While fueling, the engine will heat-soak even with oil door open combined with add'l taxing to runway which I want to avoid. My plan is to continue using 93E10, fly mornings when OAT is cooler, and avoid all ground ops. So, no intermediate stops – fly and return to base. No landings with ground taxi until refineries and fueling stations switch over to Summer vapor pressure blend.

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1
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__________________
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #27  
Old 04-12-2021, 12:53 PM
seagull seagull is offline
 
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This is interesting, I’ll be following you.
I would start a new thread specifically dealing with the vapor lock.

It is my understanding the vapor lock occurs in the fuel lines not in the bowl. Maybe find the hottest fuel line location and monitor it?
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  #28  
Old 04-12-2021, 01:21 PM
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Piper J3 Piper J3 is online now
 
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If vapor lock occurs in the fuel lines, then perhaps add’l insulation on top of the existing Fire Sleave is warranted.

Amazon Aircraft Dept again to the rescue with both 1” ID x 36” L and 5/8” ID x 36” L Vapor Block Fuel Line Sleeve @ ~$16.

Just like Ross Perot used to say... "We'll raise the hood and try to figure out what's going on".

https://www.amazon.com/Design-Engine...8254374&sr=8-3
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__________________
-
Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H

Last edited by Piper J3 : 04-12-2021 at 01:28 PM.
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  #29  
Old 04-13-2021, 12:53 PM
Piper J3's Avatar
Piper J3 Piper J3 is online now
 
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Two-channel temperature sensor is temporarily installed. Thermocouples pinch nicely between float bowl and bail wire. Total install time was 15 minutes. Runway too wet for flying today. Flight test tomorrow. News @ 11…
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__________________
-
Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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  #30  
Old 04-14-2021, 01:41 PM
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Piper J3 Piper J3 is online now
 
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I have asked moderators to start a new thread RV-12/RV-12iS > Vapor Lock. I also asked that post #255 and up from this thread be transferred to the new Vapor Lock thread. So, hopefully that will be done. I think this topic should have its own thread to make it searchable in the future.

So, yesterday I temporarily installed a two-channel temperature sensor with thermocouple probes pinched against both carburetor float bowls. I flew this morning to two outlying airports with a landing to a full stop and long taxi back to departure runway at each. Flight time was 60 minutes.

Observations from this morning’s flight:

• OAT – 45F

• All temperatures reported below at right carb - right carb is consistently 5F higher than left carb on ground and in the air. I believe the proximity of the oil tank is causing additional heat on right side.

• Temp during climb – 96F

• Temp during cruise @5500 RPM – 84F

• Ground ops taxing – 98F


Now, here is the eye opener… At completion of the flight, I pushed airplane into hanger and opened oil door to see how quickly engine compartment cooled down – it didn’t. Temperatures continued to climb for 5 minutes until max temp of 116F was reached. My oil door opens to near vertical and lots of heat spills out.

So far, I don’t like what I see… 45 OAT, 98F ground ops, and oil door not spilling off enough heat. Weather in Ohio is forecast for cool temps for next two weeks so not much more to learn for a while. My concern is - what’s going to happen during summer temps?

Next steps… with left carb consistently 5F less than right carb, there is no need to measure both carb temps and only the higher right carb sensor will remain. I’m contemplating using the left thermocouple to measure temperature of one of the fuel hoses. Perhaps measure temp of a fuel hose near the “T” junction fastened to the manifold crossover tube. I suspect fuel hoses routed above the engine run pretty warm.
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__________________
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Jim Stricker - EAA #499867
PPL/ASEL 1970 - Sport Pilot since 2007
80 hrs Flying Aeronca Chief 11AC N86203
1130 hrs Flying 46 Piper J-3 Cub N6841H
Bought Flying RV-12 #120058 Oct 2015 with 48TT - Hobbs now 670

LSRM-A Certificate 2016 for RV-12 N633CM
Special Thanks... EJ Trucks - USN Crew Chief A-4 Skyhawk
MJ Stricker (Father & CFI) - USAAF 1st Lt. Captain B-17H
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