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Given the cooling issues of both the VW conversions and the Jabiru engines, has anybody looked into adding cowl flaps to a Sonex/Waiex/Xenos? I'm not sure if with the exhaust location there is room on the bottom rear of the cowl, but the slab sides at the lower rear should have plenty of room. I'm not an airplane engineer, so there may be good reasons this is a terrible idea. I'm just looking for any advantage in keeping these things cool and happy.

That's an interesting idea Andy. I can't help but wonder if cowl flaps are pushing the "too complex to be worth it" category. I've read a few reports indicating one big problem is having too small an exit area, so I tried to make sure that on my cowling it won't be an issue. Hopefully enough exit area and a good job on the cooling baffles will keep things from being an issue for everyone.

On our other homebuilt, we took a lesson from the Vans RV-10 guys and added cooling louvers to our lower cowling. They did a great job lowering oil and CHT temps. They may also be an easy option to add to a lower cowling. Just a thought...

MichaelFarley56 wrote:That's an interesting idea Andy. I can't help but wonder if cowl flaps are pushing the "too complex to be worth it" category. I've read a few reports indicating one big problem is having too small an exit area, so I tried to make sure that on my cowling it won't be an issue. Hopefully enough exit area and a good job on the cooling baffles will keep things from being an issue for everyone.

On our other homebuilt, we took a lesson from the Vans RV-10 guys and added cooling louvers to our lower cowling. They did a great job lowering oil and CHT temps. They may also be an easy option to add to a lower cowling. Just a thought...

I agree that simpler is better. I just don't like how how the Jabiru 3300 runs on the ground and in climb, so I'm looking for ways to mitigate that (short of spending $4K on Rotec liquid-cooled heads!). Simpler is only better if simpler does the job. ;)

I like the louver idea, maybe I'll do some research in that direction. One less knob or lever is always a good thing.

Jeff Schultz has some good info on cooling here: http://www.sonex604.com/cooling.html