SonexBuilders.net

Hi Everyone,

I'm on my on my third Sonex, having recently purchased a 99% kit with a spanking new, really old Jabiru 3300 engine.

There's not much to be done before its ready to fly, but I'm wondering if the original builder knew what he was doing relative to cooling.

I'm attaching a pic of the cooling baffle over the 3300 engine. Will this work, or is there a better example for how to re-do the baffling?

Or for that matter, should I consider the LCH head option?

Thanks,

James Wiebe

Hi James,
Can't really tell from a pic and until you fly it I think...hopefully you have some temp instrumentation? Ideally on all 6.
Looks like an early Gen with that exhaust. I'm interested to hear how that heat muff works out..
I also notice no baffling material around the shroud to the oil cooler. That might be an issue (affecting the flow pressure differential).
What does the cowling have? Stock plan Sonex exit holes design?. I ended up making mine larger than plans which helped to give me better cooling.

Also on the LCH - suggest reading rbarber's report on installing those. There is some good firsthand info there.
The Sonex engine compartment is pretty tight...not a lot of room for extras, at least in mine.
Keeping the heads cool is obviously important, but also the cylinders, especially on the bottom. There also is some good info from DAmsler on cooling on the JabCamit groups.io list (Files section).

This is a very early version of our Jabiru baffles. You will have better cooling with higher-volume baffles we've been providing for many years now: https://www.sonexaircraft.com/eshop/car ... ory_id=335

James Wiebe wrote:I'm attaching a pic of the cooling baffle over the 3300 engine. Will this work, or is there a better example for how to re-do the baffling?

Definitely use a baffle with larger volume. I have tried 3 different types over the years.
The small Jabiru baffle with external plug leads. I dont think they had enough volume.
The Sonex metal ones they worked but tended to crack between the cylinders.
I then modified the old jabiru fibreglass ones to a similar dimension as the sonex metal ones. I did cut a small slot in the upper part of the baffles internal deflectors to allow more air through to the rear cylinders. I think that alone made the biggest improvement to equalling the temperatures

James Wiebe wrote:Hi Everyone,
Or for that matter, should I consider the LCH head option?

I wouldn't bother. The engine can be set up to cool properly without the added weight and complexity. There is also barely enough room in the engine bay as it is.