Nick
Well Known Member
A few of you have inquired about my cowl flaps. I thought it best to start a new thread, so here we are!
Background: As we all know, the 10 has had a problem with cooling. The solution for almost everyone was to add Louvers. The idea of Louvers isn't a bad one, but I thought I would try something different. The problem with Louvers (IMO) is they work great for cooling in climb, but in cruise when you don't need the extra cooling they are still there dumping air (drag) in all phases of flight.
Compounding this, are the reports at the time stating that the James cowl ran even hotter than the stock Vans cowl. We had elected early on to go with the James, and now I wanted to make sure that wasn't a mistake!
Anyone contemplating doing this has probably figured out the same thing I did. There simply isn't any room to do a proper cowl flap. The exhaust gets in the way! Our wonderful Muffler/Heat box is simply so large that it fills the bottom cowl. I know of one gentleman that his workaround was to make his cowl flaps open all the time. This works great for cooling, but the drag is simply too high.
I designed up a cowl flap that the inside edge moves clear of the Muffler. I was hoping for the best of both worlds, great cooling in climb, without the drag penalty in cruise.
The end result has been very positive. With no additional Louvers, stock James exit and cowl flaps: Climb temps CHT's @ 115-120 knts 400-418. Our #1 is the hottest and will get to 420 first at which point I'll lower the nose a tad. We are still able to climb in the 1000-1500 FPM range. Oil temps in climb are stable in the 218-222 range.
Once leveled off, I'll leave the CF open until all CHT's are under 400. Close everything up and CHT's get stable between 375-395, oil temp 200-205. In the middle of the Texas summer those will be a little higher, but still manageable. CHT's 402-385, Oil Temp 205-210.
In nearly 200 Hrs of flying I've not found to be temperature limited in any normal operations. What I can NOT do is climb to 15000ft @ 2000 fpm. I can make it to 10,000 but by that time the oil temps are in the 225 range and CHT's are all pushing just over 420. We set our personal CHT limit to 420 in hopes of extending cylinder life.
I am currently prepping for paint, and with that included some cowl make overs. I'm re-doing the Plenum in hopes of getting a better seal, and a more even CHT spread. I'm re-doing the cowl flaps (external portion only) to achieve a better seal when closed. I've also done some other "stuff" under the cowl in the attempt to clean up the exit air. I'll know in a few months if it was successful.
I'll apologize in advance. The pictures are terrible. I took those months ago with my old phone... If enough interest is expresses I can probably be talked into getting some higher quality shots.
Also included is a short movie I made with Solidworks to show the full operation. It?s a little large (3.5M) so give it a min when loading.
Enjoy!
How they work: Solidworks Animation
Background: As we all know, the 10 has had a problem with cooling. The solution for almost everyone was to add Louvers. The idea of Louvers isn't a bad one, but I thought I would try something different. The problem with Louvers (IMO) is they work great for cooling in climb, but in cruise when you don't need the extra cooling they are still there dumping air (drag) in all phases of flight.
Compounding this, are the reports at the time stating that the James cowl ran even hotter than the stock Vans cowl. We had elected early on to go with the James, and now I wanted to make sure that wasn't a mistake!
Anyone contemplating doing this has probably figured out the same thing I did. There simply isn't any room to do a proper cowl flap. The exhaust gets in the way! Our wonderful Muffler/Heat box is simply so large that it fills the bottom cowl. I know of one gentleman that his workaround was to make his cowl flaps open all the time. This works great for cooling, but the drag is simply too high.
I designed up a cowl flap that the inside edge moves clear of the Muffler. I was hoping for the best of both worlds, great cooling in climb, without the drag penalty in cruise.
The end result has been very positive. With no additional Louvers, stock James exit and cowl flaps: Climb temps CHT's @ 115-120 knts 400-418. Our #1 is the hottest and will get to 420 first at which point I'll lower the nose a tad. We are still able to climb in the 1000-1500 FPM range. Oil temps in climb are stable in the 218-222 range.
Once leveled off, I'll leave the CF open until all CHT's are under 400. Close everything up and CHT's get stable between 375-395, oil temp 200-205. In the middle of the Texas summer those will be a little higher, but still manageable. CHT's 402-385, Oil Temp 205-210.
In nearly 200 Hrs of flying I've not found to be temperature limited in any normal operations. What I can NOT do is climb to 15000ft @ 2000 fpm. I can make it to 10,000 but by that time the oil temps are in the 225 range and CHT's are all pushing just over 420. We set our personal CHT limit to 420 in hopes of extending cylinder life.
I am currently prepping for paint, and with that included some cowl make overs. I'm re-doing the Plenum in hopes of getting a better seal, and a more even CHT spread. I'm re-doing the cowl flaps (external portion only) to achieve a better seal when closed. I've also done some other "stuff" under the cowl in the attempt to clean up the exit air. I'll know in a few months if it was successful.
I'll apologize in advance. The pictures are terrible. I took those months ago with my old phone... If enough interest is expresses I can probably be talked into getting some higher quality shots.
Also included is a short movie I made with Solidworks to show the full operation. It?s a little large (3.5M) so give it a min when loading.
Enjoy!
How they work: Solidworks Animation
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