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Automatic upper cowl flap
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trigo(at)mail.telepac.pt
Guest

Posted: Sun Jul 01, 2007 9:21 am Post subject: Automatic upper cowl flap

Since I'm using a Subaru engine, I need to have some kind of ventilation 

exit on the upper cowling, to dissipate heat after engine shutdown. Most 

builders just make a row of 3/4" holes, and others put side louvers that 

look like shark guills.

I intend to make the upper row of holes, but don't want to let them always 

open, due to the possibility of rain penetration and also because they can 

have a bad influence in the cooling air flow inside the cowling.

Therefore I thought of a small (some 15" x 1 1/2") moving flap, which covers 

the holes, and is normally closed in flight.



Now the electrical challenge, that I put here to the smart guys of this 

list:

The ideal solution to manouver this flap would be to automatically open it 

when the engine is turned off. How can it be done?



Carlos

RV-9A



P.S. - I know this is not a KIS solution...

trigo(at)mail.telepac.pt
Guest

Posted: Sun Jul 01, 2007 9:22 am Post subject: Automatic upper cowl flap

Since I'm using a Subaru engine, I need to have some kind of ventilation

exit on the upper cowling, to dissipate heat after engine shutdown. Most

builders just make a row of 3/4" holes, and others put side louvers that

look like shark guilds.

I intend to make the upper row of holes, but don't want to let them always

open, due to the possibility of rain penetration and also because they can

have a bad influence in the cooling air flow inside the cowling.

Therefore I thought of a small (some 15" x 1 1/2") moving flap, which covers

the holes, and is normally closed in flight.



Now the electrical challenge, that I put here to the smart guys of this

list:

The ideal solution to maneuver this flap would be to automatically open it

when the engine is turned off, which in this engine's case is to turn Off an 

electrical switch.

How can it be done?



Carlos

RV-9A



P.S. - I know this is not a KIS solution...

ronburnett(at)charter.net
Guest

Posted: Sun Jul 01, 2007 10:01 am Post subject: Automatic upper cowl flap

Carlos,

Perhaps just making the oil cooler door to open in a manner that YOU can leave it open for awhile after shutdown would be the simplest solution.

Ron Burnett--

For a relaxing vacation at the Gulf, rent our condo directly from us and 

save! 

See http://vrbo.com/126328 

Do not archive



---- Carlos Trigo <trigo(at)mail.telepac.pt> wrote: 

 	  Quote: 	
		   

 

 Since I'm using a Subaru engine, I need to have some kind of ventilation 

 exit on the upper cowling, to dissipate heat after engine shutdown. Most 

 builders just make a row of 3/4" holes, and others put side louvers that 

 look like shark guills.

 I intend to make the upper row of holes, but don't want to let them always 

 open, due to the possibility of rain penetration and also because they can 

 have a bad influence in the cooling air flow inside the cowling.

 Therefore I thought of a small (some 15" x 1 1/2") moving flap, which covers 

 the holes, and is normally closed in flight.

 

 Now the electrical challenge, that I put here to the smart guys of this 

 list:

 The ideal solution to manouver this flap would be to automatically open it 

 when the engine is turned off. How can it be done?

 

 Carlos

 RV-9A

 

 P.S. - I know this is not a KIS solution...

N1DeltaWhiskey(at)comcast
Guest

Posted: Sun Jul 01, 2007 12:01 pm Post subject: Automatic upper cowl flap

Ron,



Without knowing what you plan to use to open/close the flap, the electrical 

seems like putting the cart before the horse.



The simplest system might have a device that incorporates a coil to 

contract/extend a control rod.  Arrange it is such a manner that the 

unpowered position maintains the flap open, the energized position closes 

the flap.



You also need to consider pressures inside/outside the cowling with the 

design to determine whether the device would operate as expected under the 

anticipated pressures if not using center pivoting on the flap.



I use a Sube and my solution will be the oil fill hatch, at least in the 

near term.



Doug



---

fvalarm(at)rapidnet.net
Guest

Posted: Sun Jul 01, 2007 12:14 pm Post subject: Automatic upper cowl flap

Why not just open the oil dip-stick door.



Bevan 

RV7A

--

larry(at)macsmachine.com
Guest

Posted: Sun Jul 01, 2007 1:26 pm Post subject: Automatic upper cowl flap

Hi Carlos,

I'd not recommend you add ventilation for a Subaru engine.  The heat 

from this water-cooled engine never approaches

temps seen in an air cooled engine.  I read 210 degrees on a very hot 

day and by the time I've taxied back to the hangar, the temps settle 

back to 180 degrees F.



Larry McFarland 601HDS at www.macsmachine.com



Carlos Trigo wrote:

 	  Quote: 	
		   

 <trigo(at)mail.telepac.pt>



 Since I'm using a Subaru engine, I need to have some kind of 

 ventilation exit on the upper cowling, to dissipate heat after engine 

 shutdown.

 Carlos

 RV-9A



 P.S. - I know this is not a KIS solution...

trigo(at)mail.telepac.pt
Guest

Posted: Sun Jul 01, 2007 3:05 pm Post subject: Automatic upper cowl flap

---

trigo(at)mail.telepac.pt
Guest

Posted: Sun Jul 01, 2007 3:10 pm Post subject: Automatic upper cowl flap

---

trigo(at)mail.telepac.pt
Guest

Posted: Sun Jul 01, 2007 3:14 pm Post subject: Automatic upper cowl flap

Hi Larry



But that is still what the Eggenfellner factory recommends, especially when 

you shut down the engine shortly after landing. They say every car has that 

ventilation exit



Carlos

---

larry(at)macsmachine.com
Guest

Posted: Sun Jul 01, 2007 4:36 pm Post subject: Automatic upper cowl flap

Carlos,

It may be that a car needs this for idling around town at stoplights and 

for lugging up a hill in the summer, but with a good cooling

system in the plane, Subaru temps drop off from 180 to ambient rather 

quickly.  The heat from an air cooled engine and its exhaust pipes would 

be much higher, but I'd get a recorded temperature reading in the upper 

rear cowl before putting any work into a vent.

Realizing Eggenfellner is a purest and has good product, exceeding the 

requirements is what they do best.  Hard to argue that. I'd

still put a temp sensor there for run up and get a reading on peak temps 

after shut down. We'd really be interested in what you find.



Larry McFarland 

Carlos Trigo wrote:

 	  Quote: 	
		   

 <trigo(at)mail.telepac.pt>



 Hi Larry



 But that is still what the Eggenfellner factory recommends, especially 

 when you shut down the engine shortly after landing. They say every 

 car has that ventilation exit

ceengland(at)bellsouth.ne
Guest

Posted: Sun Jul 01, 2007 5:22 pm Post subject: Automatic upper cowl flap

Carlos Trigo wrote:

 	  Quote: 	
		   

 <trigo(at)mail.telepac.pt>

 

 Since I'm using a Subaru engine, I need to have some kind of ventilation 

 exit on the upper cowling, to dissipate heat after engine shutdown. Most 

 builders just make a row of 3/4" holes, and others put side louvers that 

 look like shark guills.

 I intend to make the upper row of holes, but don't want to let them 

 always open, due to the possibility of rain penetration and also because 

 they can have a bad influence in the cooling air flow inside the cowling.

 Therefore I thought of a small (some 15" x 1 1/2") moving flap, which 

 covers the holes, and is normally closed in flight.

 

 Now the electrical challenge, that I put here to the smart guys of this 

 list:

 The ideal solution to manouver this flap would be to automatically open 

 it when the engine is turned off. How can it be done?

 

 Carlos

 RV-9A

 

 P.S. - I know this is not a KIS solution...



I didn't see what airframe the Sube is powering, but if the cowl is 
	


typical you can just add holes in a flat area & add a hinged door under 

them. If you limit the door's travel to less than 90 degrees, air 

pressure during flight will push it closed. When you shut down, it will 

drop open. It's been done by others to achieve what you're after. (KIS?)



Charlie

john(at)ballofshame.com
Guest

Posted: Sun Jul 01, 2007 5:41 pm Post subject: Automatic upper cowl flap

EXACTLY my thoughts on the matter.



-John

www.ballofshame.com

Charlie England wrote:

 	  Quote: 	
		   

 <ceengland(at)bellsouth.net>



 Carlos Trigo wrote:

> 

> <trigo(at)mail.telepac.pt>

>

> Since I'm using a Subaru engine, I need to have some kind of 

> ventilation exit on the upper cowling, to dissipate heat after engine 

> shutdown. Most builders just make a row of 3/4" holes, and others put 

> side louvers that look like shark guills.

> I intend to make the upper row of holes, but don't want to let them 

> always open, due to the possibility of rain penetration and also 

> because they can have a bad influence in the cooling air flow inside 

> the cowling.

> Therefore I thought of a small (some 15" x 1 1/2") moving flap, which 

> covers the holes, and is normally closed in flight.

>

> Now the electrical challenge, that I put here to the smart guys of 

> this list:

> The ideal solution to manouver this flap would be to automatically 

> open it when the engine is turned off. How can it be done?

>

> Carlos

> RV-9A

>

> P.S. - I know this is not a KIS solution...

>

 I didn't see what airframe the Sube is powering, but if the cowl is 

 typical you can just add holes in a flat area & add a hinged door 

 under them. If you limit the door's travel to less than 90 degrees, 

 air pressure during flight will push it closed. When you shut down, it 

 will drop open. It's been done by others to achieve what you're after. 

 (KIS?)



 Charlie

N1DeltaWhiskey(at)comcast
Guest

Posted: Sun Jul 01, 2007 9:52 pm Post subject: Automatic upper cowl flap

Carlos,



Not sure why one would be concerned about doing that from the cockpit.  If I 

wanted something to open right away when the engine was shut down, and 

before I could exit the cockpit, a gravity flap would be my preference - it 

should close once the cowling is pressurized (but that begs the question of 

why it would be pressurized - doesn't that mean there is more airflow into 

the cowling than wants to escape, i.e., drag?).  If that didn't work, I 

would next consider a simple push-pull mechanical lever that would push the 

flap closed when pushed full forward, back to open.  Last option would be an 

electrical one.



Doug



---

N1DeltaWhiskey(at)comcast
Guest

Posted: Sun Jul 01, 2007 9:54 pm Post subject: Automatic upper cowl flap

Larry,



Would generally agree with you, but in my case, there is a header tank in 

the engine compartment and getting the heat out helps to keep from heat 

soaking the fuel which could cause vapor lock problems. Eggenfelner's 

reasoning may be similar even if there is no such tank. Carlos did not 

mention that he had one, so assume it would be to limit heating of the fuel 

in the fuel lines.



Doug

---

trigo(at)mail.telepac.pt
Guest

Posted: Mon Jul 02, 2007 1:24 am Post subject: Automatic upper cowl flap

Thanks Charlie



It's really a smart idea, with only one inconvenient. It will not prevent 

rain water entrance when the aircraft is parked outside.

I'll put it in my solutions list. If it doesn't work properly, I still need 

the electrical automation ...



Carlos

---

klehman(at)albedo.net
Guest

Posted: Mon Jul 02, 2007 5:12 am Post subject: Automatic upper cowl flap

Hello Carlos



I use a reverse scoop (facing rearwards) just over an inch high and 

maybe 6" wide about 6" ahead of the windshield.  What is interesting is 

that on the ground air exits the scoop however since that is a fairly 

high pressure area, air enters the scoop in flight.  Even more air would 

enter if one had a radiator in the cowl ahead of the scoop as the 

pressure inside the cowl would be lower than my installation.



Ken

echristley(at)nc.rr.com
Guest

Posted: Mon Jul 02, 2007 5:23 am Post subject: Automatic upper cowl flap

Carlos Trigo wrote:

[quote] 

 <trigo(at)mail.telepac.pt>



 Thanks Charlie



 It's really a smart idea, with only one inconvenient. It will not 

 prevent rain water entrance when the aircraft is parked outside.

 I'll put it in my solutions list. If it doesn't work properly, I still 

 need the electrical automation ...



 Carlos

 ---

flydad57(at)neo.rr.com
Guest

Posted: Mon Jul 02, 2007 6:17 am Post subject: Automatic upper cowl flap

You might try using the bi-metal coil from a thermometer.



Bob Taylor

Wadsworth, Ohio

N657RT, Res.

---

aerobubba(at)earthlink.ne
Guest

Posted: Mon Jul 02, 2007 9:12 am Post subject: Automatic upper cowl flap

Hi Carlos-



 	  Quote: 	
		  The ideal solution to maneuver this flap would be to automatically open it

when the engine is turned off, which in this engine's case is to turn Off

an 
	


 	  Quote: 	
		  electrical switch.

How can it be done?

 
	


I once saw a Glasair III that had a clever solution to his vapor lock

problems.  A series of oval holes were cut into the cowling / plenum top. 

They were perhaps 1" long and 1/2" wide, lined up in a lateral row perhaps

1" by 1'.  Underneath the top skin was a hinged flap that was pressed

against the skin by a bimetal spring.  Once the engine was shut down and

the cowling temps rose to a high enough level, the bimetal spring opened

the vent.  Once temps dropped, the vent would close itself.  It was pretty

neat as it was autonomous and didn't require power.  



glen matejcek

aerobubba(at)earthlink.net

trigo(at)mail.telepac.pt
Guest

Posted: Mon Jul 02, 2007 10:45 am Post subject: Automatic upper cowl flap

Thanks Glenn



That is really a very clever solution.



And where do you think I can get that "miraculous" bimetal spring?

Are those "calibrated" for the temperature we want it to actuate?



Carlos

---

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