VansAirForceForums  
Home > VansAirForceForums

- POSTING RULES
- Donate yearly (please).
- Advertise in here!

- Today's Posts | Insert Pics

  #1  
Old 06-12-2018, 10:34 PM
crabandy crabandy is offline
 
Join Date: Jan 2010
Location: Ottawa, Ks
Posts: 1,903
Default Cowl flap thoughts

I think Iíve seen/googled most of the ideas out there when it comes to cooling the lycoming in the summertime. Iím sure there are many more out there that I havenít seen. Iíve done a decent amount of work with inlets/plenum/sealing and lastly ignition timing for temp control. Most people seem to be concerned with climb out CHTís. I currently have no issues climbing out on a hot day, I have issues taxiing after a quick turn on a hot day and Iím carbureted. CHTís and oil temps are fine but fuel seems to be boiling, erratic chugging during taxi. Idle mixture is correct and an excessively lean mixture and RPMís above 1000 help.

With my stock cowling I used to see heat radiating out of the upper inlets while fueling. I donít see it with my sealed inlet boots. During ground operations the pressure diff between the upper cowl and lower cowl is very small. How many people pop the oil door open after they land in hot temps?

Most cowl flaps are installed in conjunction with the lower outlet, Iíve stared at this space on my cowling for months trying to come up with ideas. Iíve shrunk and contoured my exit to approximately 35 sq inches, not a lot of room for a cowl flap with a vertical induction carb and 2 exhaust pipes.

Iíve also been staring at the rear of my upper cowling, what about an upper cowl flap, similar to the old 30ís cars/trucks had in front of the windshield? With the low pressure diffs on the ground it would take advantage of convection in addition to a larger exit area during climb out. I kept hoping for an easy test without months of work and downtime.

Iím currently finishing an oil change and making room behind the upper engine mount to possibly add an upper cowl flap when it dawned on me, why donít I spend 2 minutes and remove the oil door and go fly several quick turns? On 4 cylinder lycomings the oil door is behind the upper plenum and part of the lower cowling volume/pressure. Roughly 5x5 (25 sq in) in the upper cowling that is convection friendly on the ground, also pretty easy for anyone else to test fly and and see what kind of cooling the extra exit area gives them.
__________________
RV 7 300 hours and counting
12/17 donation
Reply With Quote
  #2  
Old 06-13-2018, 04:33 AM
Plummit's Avatar
Plummit Plummit is offline
 
Join Date: Apr 2010
Location: SoCal
Posts: 697
Default

Just removing the door may not work. I'm pretty sure that part of what makes a cowl flap work is the flap only allowing exit air, which you won't have with just a hole. But by all means try it and let us know what happens!

-Marc
__________________
RV-10
N814RV
2018 Donation made!
Reply With Quote
  #3  
Old 06-13-2018, 06:16 AM
Taltruda Taltruda is offline
 
Join Date: Oct 2017
Location: Las Vegas, NV
Posts: 84
Default

I used to fly a friends glasair 2rg that had two slots on the upper cowl with a spring loaded door. It souls open and vent off the heat when on the ground but would close itself when ramair in the upper cowl would build up.
__________________
Tom
Las Vegas
2018 Dues Paid
Reply With Quote
  #4  
Old 06-13-2018, 06:31 AM
MikeyDale's Avatar
MikeyDale MikeyDale is offline
 
Join Date: Aug 2012
Location: Garden City Texas
Posts: 807
Default

When I started flying my 7, I always thought something was wrong with my engine. After landing on taxi it would pop and chug! I kept thinking my plugs were fouling! I even bought a set of fine wire plugs to solve the problem (well worth the money by the way but didn't help my problem). I was at 52F one day where Walt was inspecting my Transponder having lunch outside the diner and lo and behold, every RV that came taxiing by was popping and chugging just like mine! Boost pump helps but she's gonna pop when that fuel boils in those injector lines!
__________________
Mike Hillger
RV 7 FLYING SINCE 4/2015!
Garden City, Texas
First Flight https://www.youtube.com/watch?v=QqgxhWH3pqA
Build Blog http://mikesrv7.blogspot.com/
Dues Paid
Reply With Quote
  #5  
Old 06-13-2018, 09:14 AM
rocketman1988 rocketman1988 is offline
 
Join Date: Jun 2010
Location: Sunman, IN
Posts: 1,022
Default An idea...

Many years ago, in one of the experimental aircraft magazine (can't remember which one), there was an article on automatic shutters for the top side of a cowl.

The basis of the design was quite elegant. A set of shutters with moveable doors was installed in the top of the cowl. The activation of the shutter doors was accomplished using the charge cylinder from an automotive thermostat. The plug inside of the charge cylinder expands as it is heated past it's critical temperature and moved the shutter doors to the open position. As the charge cylinder cools, it contracts and closes the shutter doors...

Of course, with modern tech, you could accomplish the same thing using a linear actuator and a temp sensor connected to a small arduino unit...and it would be programmable for any given temperature or time...

These shutters are remade and would do the trick:

https://antisplataero.com/products/o...er-air-shutter
__________________
Bob
Aerospace Engineer '88

RV-10
Structure - 90% Done
Cabin Top - Aaarrghhh...
Doors - Done
On Gear
290 HP Barrett Hung
ShowPlanes Cowl with Skybolts Fitted - Beautiful

Dues Paid 2017,...Thanks DR+
Reply With Quote
  #6  
Old 06-13-2018, 12:12 PM
PerfTech's Avatar
PerfTech PerfTech is offline
 
Join Date: Sep 2010
Location: Yucaipa, Ca.
Posts: 1,311
Default

Quote:
Originally Posted by crabandy View Post
I think Iíve seen/googled most of the ideas out there when it comes to cooling the lycoming in the summertime. Iím sure there are many more out there that I havenít seen. Iíve done a decent amount of work with inlets/plenum/sealing and lastly ignition timing for temp control. Most people seem to be concerned with climb out CHTís. I currently have no issues climbing out on a hot day, I have issues taxiing after a quick turn on a hot day and Iím carbureted. CHTís and oil temps are fine but fuel seems to be boiling, erratic chugging during taxi. Idle mixture is correct and an excessively lean mixture and RPMís above 1000 help.

With my stock cowling I used to see heat radiating out of the upper inlets while fueling. I donít see it with my sealed inlet boots. During ground operations the pressure diff between the upper cowl and lower cowl is very small. How many people pop the oil door open after they land in hot temps?

Most cowl flaps are installed in conjunction with the lower outlet, Iíve stared at this space on my cowling for months trying to come up with ideas. Iíve shrunk and contoured my exit to approximately 35 sq inches, not a lot of room for a cowl flap with a vertical induction carb and 2 exhaust pipes.

Iíve also been staring at the rear of my upper cowling, what about an upper cowl flap, similar to the old 30ís cars/trucks had in front of the windshield? With the low pressure diffs on the ground it would take advantage of convection in addition to a larger exit area during climb out. I kept hoping for an easy test without months of work and downtime.

Iím currently finishing an oil change and making room behind the upper engine mount to possibly add an upper cowl flap when it dawned on me, why donít I spend 2 minutes and remove the oil door and go fly several quick turns? On 4 cylinder lycomings the oil door is behind the upper plenum and part of the lower cowling volume/pressure. Roughly 5x5 (25 sq in) in the upper cowling that is convection friendly on the ground, also pretty easy for anyone else to test fly and and see what kind of cooling the extra exit area gives them.
Ö.We have had many customers mount our cowl flaps on the sides of the lower cowl as well as on the top. They report back many advantages, Lower ground operations temperature being one. Another is even lower climb out temperatures, due to the fact that the pressure in this configuration is much lower on top than on the bottom. We have seen most everything possible with flaps on top, sides, bottom and all of the above in one installation. The top mounted location is very popular in Brazil on the RV-10s. Its all good!
Thanks, Allan..
__________________
Allan Nimmo
AntiSplatAero.com
Innovative Aircraft Safety
Products, Tools & Services
Info@AntiSplatAero.com
Southern California (KREI)
RV-9A / Edge-540
(909) 824-1020
Reply With Quote
  #7  
Old 06-13-2018, 12:43 PM
Mike S's Avatar
Mike S Mike S is online now
Senior Curmudgeon
 
Join Date: Sep 2005
Location: Dayton Airpark, NV A34
Posts: 14,245
Default

Quote:
Originally Posted by rocketman1988 View Post
Many years ago, in one of the experimental aircraft magazine (can't remember which one), there was an article on automatic shutters for the top side of a cowl.

The basis of the design was quite elegant. A set of shutters with moveable doors was installed in the top of the cowl. The activation of the shutter doors was accomplished using the charge cylinder from an automotive thermostat. The plug inside of the charge cylinder expands as it is heated past it's critical temperature and moved the shutter doors to the open position. As the charge cylinder cools, it contracts and closes the shutter doors...
Yep, remember that one.

A simpler setup is to use a magnet to hold the door in the up/closed position, and you just give the door a push down to open it when you land. Air pressure will close it when you take off.
__________________
Mike Starkey
VAF 909

Rv-10, N210LM.

Flying as of 12/4/2010

Phase 1 done, 2/4/2011

Sold after 240+ wonderful hours of flight.

"Flying the airplane is more important than radioing your plight to a person on the ground incapable of understanding or doing anything about it."

Last edited by Mike S : 06-14-2018 at 07:27 AM.
Reply With Quote
  #8  
Old 06-13-2018, 02:40 PM
krw5927 krw5927 is offline
 
Join Date: Aug 2010
Location: Wichita, KS
Posts: 1,858
Default

Andy, are you using 100LL? Its vapor pressure is lower than most (all?) mogas blends, especially if you happen to get some winter blend mogas at the pump and use it on a hot day.

Disregard if you're already using 100% 100LL.
__________________
Kurt W.
RV9A
FLYING!!!
Reply With Quote
  #9  
Old 06-14-2018, 12:21 AM
crabandy crabandy is offline
 
Join Date: Jan 2010
Location: Ottawa, Ks
Posts: 1,903
Default

Quote:
Originally Posted by krw5927 View Post
Andy, are you using 100LL? Its vapor pressure is lower than most (all?) mogas blends, especially if you happen to get some winter blend mogas at the pump and use it on a hot day.

Disregard if you're already using 100% 100LL.
Not 100% 100LL, but I keep 1 tank strictly 100LL for takeoff and landing. I use 91 ethanol free mogas in the other tank at lower/cooler power settings mostly in cruise. I switch to my 100LL tank with my BCGumps landing checklist, I might not have burned all the mogas out of the system as Iím taxiing in. Iím not convinced itís a mogas Problem, but easy to eliminate the possibility with 100% 100LL usage.
__________________
RV 7 300 hours and counting
12/17 donation
Reply With Quote
  #10  
Old 06-14-2018, 12:27 AM
crabandy crabandy is offline
 
Join Date: Jan 2010
Location: Ottawa, Ks
Posts: 1,903
Default

Quote:
Originally Posted by MikeyDale View Post
When I started flying my 7, I always thought something was wrong with my engine. After landing on taxi it would pop and chug! I kept thinking my plugs were fouling! I even bought a set of fine wire plugs to solve the problem (well worth the money by the way but didn't help my problem). I was at 52F one day where Walt was inspecting my Transponder having lunch outside the diner and lo and behold, every RV that came taxiing by was popping and chugging just like mine! Boost pump helps but she's gonna pop when that fuel boils in those injector lines!
Mikey,
Iím carbureted with dual electronic ignition and auto plugs, I think the fuel is boiling in my carb bowl....
__________________
RV 7 300 hours and counting
12/17 donation
Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump


All times are GMT -6. The time now is 02:30 PM.


The VAFForums come to you courtesy Delta Romeo, LLC. By viewing and participating in them you agree to build your plane using standardized methods and practices and to fly it safely and in accordance with the laws governing the country you are located in.