SonexBuilders.net

Hey All

Has any one on here ever used Cowl Flaps instead of the Stock Outlets?? I am planning on making these for my Jab 3300, I am looking in to how the mechanism has to be made and what kind of cables are used to actuate the flaps..

Thanks
Mike

Hi Mike. My first attempt to reply to this thread disappeared into cyberspace so if it returns, sorry. Thank you for bringing this idea forward. I'm planning to install cowl flaps for the usual reasons of improved cooling in the climb and reduced drag at cruise. Have you seen the brilliant work of Mr. Dan Horton at vansairforce.com? His thread is labelled, "The Shrinking Exit" and discusses his experimentation with "...large, low velocity inlets with a throttled exit" (external pressure recovery).

In our quest for cruse speeds, cooling drag probably represents the lowest hanging fruit.

Gunther

Hi Mike,
I think adjustable cowling flaps would be useful. My engine runs too cool on long descents. It's hard to fit them with the standard arrangement, but an Australian builder, Brian Ham, did build a horizontally split cowling with adjustable outlets. I'll try to find out how he did it and how effective it was. I know he had some trouble with the engine running hot when he first started test flying.

Peter
Sonex 894

Hello again Mike, just had a talk to Brian. The problem he had with his adjustable outlet was that his push/pull cable arrangement was not strong enough to overcome air loads, so it wouldn't stay fully open. He eventually just locked it fully open. I suspect that you do need to horizontally split cowling, easy to do now. Maybe a small electric screw jack would be better than a cable arrangement.

Peter
Sonex 894

peter anson wrote:Hello again Mike, just had a talk to Brian. The problem he had with his adjustable outlet was that his push/pull cable arrangement was not strong enough to overcome air loads, so it wouldn't stay fully open. He eventually just locked it fully open. I suspect that you do need to horizontally split cowling, easy to do now. Maybe a small electric screw jack would be better than a cable arrangement.

Peter
Sonex 894

Hey Peter

My cowl is not horizontally split, which isn't going to be a problem..

I figured that the air pressure on the flap would be a lot, so I am going to come up with some thing that will fix that problem.. Not ready to give out my secret just yet, but if it works, then I will post how I made it.. The first flight is problably 3-4 months out..

Mike

Check this cowl flap... Popular with the RV gang.

http://antisplataero.com/products/ez-cool-cowl-flap

Lance