Quantcast

A good control for cowl flaps?

HomeBuiltAirplanes.com

Help Support HomeBuiltAirplanes.com:

Battson

Well-Known Member
Joined
Jan 30, 2012
Messages
610
Location
New Zealand
Hey all,

Does anyone know of a good cowl flap control you can get? I'm thinking similar to a Cessna etc which gives you some locking force against the air pressure of the flap and vibration.

I've looked at some push-button locking controls, but I think their "10lb" locking force is insufficient. The one I have already installed moves if you push it.

Or even a way of fabricating / assembling a good control design from easily available parts, without needing special tools?


Also, thoughts on this idea - I'm thinking I'll secure the control cable to the engine mount rather than the firewall. I dont want to transfer undue stress and vibration to a small point on the firewall (although I could install a doubler, but a fatigue cracked firewall = death by rebuild).

Cheers
 

Head in the clouds

Well-Known Member
Joined
Mar 11, 2012
Messages
1,983
Location
Gold Coast, East Coast of Australia
Am I right that in your case the air pressure wants to hold it closed but you need a default (in case of failed mechanism) position of open? And do you need varying positions between open and closed or just one or the other? If you need variable then the linear actuator would probably be ideal because they are generally worm drive which prevents feedback and for an over-ride if it failed you could have the flap sprung to open and a rip-cord to pull a cotter pin out of the actuator's trunnion to release it and allow the flap to be sprung open. If you just need open and closed then an over-center toggle sprung to open and pull-cable to closed might be lighter.
 

Battson

Well-Known Member
Joined
Jan 30, 2012
Messages
610
Location
New Zealand
...for an over-ride if it failed you could have the flap sprung to open and a rip-cord to pull a cotter pin out of the actuator's trunnion to release it and allow the flap to be sprung open.
Cool thought, but IMHO stuff like that seldom works in real life, certainly not reliably.

But the electic actuator idea isn't a bad thought. Probably more than is required in this case, you'd need position feedback, a panel display, CB's, and all manner of equipment in front of the firewall etc.

The simplest, lightest solution is probably just a push/pull or lever control with in-position locking or engagement tabs etc., connected to a control cable. Just like on most light aircraft. I just can't find where to buy the suitable (former) parts!
Might be a salvage job off a Cessna.
 

Battson

Well-Known Member
Joined
Jan 30, 2012
Messages
610
Location
New Zealand
So short of paying $645 US for a OEM parts Cessna control, I've noticed these detented-locking controls which are cheap and would fit the bill:
A-740 RACHET CONTROL from Aircraft Spruce

I had really wanted to have two cowl flaps though, and would prefer a threaded control rod end to bare wire.
I noticed this control also:
A1600 SERIES POSITIVE LOCK CONTROLS - DUAL END from Aircraft Spruce

Does anyone know how a positive lock "dual ended control" works??
It sounds ideal, but I want to know what the dual ends look like. Has anyone on this forum installed this control before?

I want to make sure I end up with dual threaded rod ends, not dual push/pull dashboard knobs....
 
Last edited:

Marc Bourget

Well-Known Member
Joined
Feb 28, 2011
Messages
378
Location
Stockton, California
Well, to really throw a curve ball into this discussion, why not develop a means of "throttling" the exit air that doesn't require resistance against the pressure imposed on the Cessna style cowl flaps?

Such as, an adjustable internal ramp, ala Peter Garrison's Melmoth2

FWIW

mjb
 

Kristoffon

Well-Known Member
Joined
Sep 4, 2009
Messages
348
Location
Brazil
For adjusting my future radiator's output flap I intend to use beefy rc-type servos. They're cheap, strong and most important of all: light. Considering that a failure might mean overheated engine on the ground, or increased drag on the air, I'm not too worried about them.
 

Head in the clouds

Well-Known Member
Joined
Mar 11, 2012
Messages
1,983
Location
Gold Coast, East Coast of Australia
For adjusting my future radiator's output flap I intend to use beefy rc-type servos. They're cheap, strong and most important of all: light. Considering that a failure might mean overheated engine on the ground, or increased drag on the air, I'm not too worried about them.
That's unusual. Why do you need flaps for the radiator? Doesn't the engine's thermostat perform the same function automatically?
 

Kristoffon

Well-Known Member
Joined
Sep 4, 2009
Messages
348
Location
Brazil
That's unusual. Why do you need flaps for the radiator? Doesn't the engine's thermostat perform the same function automatically?
It's definitely not unusual, every liquid cooled piston aircraft I know of (those up to WW2, not modern experimentals) had variable geometry outlets. As I hinted above, it's about drag not temperature control.
 

Jan Carlsson

Well-Known Member
Joined
Jan 11, 2009
Messages
1,860
Location
Sweden
I've always thought an electrically actuated, electronically controlled cowl flap system would be nice.
Yes a computer controled cooling flap, it can also lit the tail light ay sun set. or the smart internal computer controled VW bellow that Joe said.
 
Top