SonexBuilders.net

Hello,

I've found a couple of examples on the net, but I think they're all A models and even a Onex. I'm curious if anyone is building a ULPower Sonex B? Strangely (I know), I'm interested in the aesthetics of the cowl. I like the look of the stock cowl, but not so much with a huge oil cooler intake on the front that I've seen in the couple UL Power planes I've found online. I'm curious whether there's alternate oil cooler mounting locations that can be used to force fresh air (like behind the baffles in a few RV's, or on fire wall for Cherokees, etc.).

Thanks!

Hi,

I'm building a ULPower 350i Sonex. The oil cooler location, like everything else, is a compromise. It is easy to mount it below the prop on the center-line, but the cowl needs modification. I'm not particularly pleased with the result of my efforts, but if you send an email to ketcherd@yahoo.com, I'll reply with a couple of pictures.

In addition to the oil cooler being somewhat problematic, the location of the inlets is, in my opinion, wrong for the ULPower. I moved the inlets outboard and up, so the air now has a straight path into the cylinder heads. This modification I do like. Also, ULPower provided their recommended inlet area, which was smaller (about 40% smaller) than the Sonex inlet.

Duncan

Hi Duncan,
I'm installing an UL350i in my Waiex-B but am not so far advanced as you are. I'm about to buy a secondhand UL350i, and have the proper engine mount and cowling supplied by Sonex.
My plan is to mount the oil cooler behind the engine, or just behind one of the rear cilinders or on the firewall so not to have mods to the underside of the cowling and also not to create an airflow under the cilinders that obstructs the cooling air from doing it's thing.
I'm interested in your pics, they might make life easier for me when installing the cowlings.

I'm following this with interest. I'm doing a 350i(S) as well. I spoke to the UL Power guys at length about oil coolers. Some have done SCAT tubing from the baffles to a remote mount oil cooler behind the engine. From what I gathered, oil temps were still problematic and they now recommend a bigger cooler if going with this option.

Interesting about the reduction in inlet size. I guess this makes sense as the UL Power derives a significantly higher percentage of cooling from the oil than from airflow through the cylinder head fins. I'm also planning on a plenum to hopefully reduce cooling drag even further. I'm expecting to need to do a fair amount of cowl modification to make it all work.

I'd also love to hear thoughts on induction air. I'm not at all enthusiastic about drawing intake air from the hot air surrounding the engine. I'd like to a do an intake from the top cowl for a "cold air" if not "ram air" induction. Still wrapping my head around the best way to implement this.

If anyone has any pics of their installation--even if a work in progress, I'd love to see it.

I've now flown my Sonex with a UL350i. My oil cooler is mounted on the center-line below the prop, angled (roughly) with the cowl and exposed to ram air. This required quite a lot of modification to the cowl but one advantage is short and simple oil lines to and from the cooler (its not a UL cooler).
I previously stated that I reduced the area and relocated the Sonex cowl inlets. Also, in addition to the standard Sonex side exits, I added two louver exits on the underside of the cowl. The resulting exit to inlet area ratio is about 3.
Oil Temps:
The oil temperatures in flight (based on a few spring time flights) are good. On the ground at full power, the oilT rises quite quickly and the oilT limit is reached after a couple of minutes or so. Taxing, run-up checks, and waiting a few minutes for takeoff does not cause an oilT problem.
CHTs:
I have CHTs on my left and right rear cylinders. On the ground these climb slowly (or quickly at full power) but a left to right difference is evident. After a longish taxi and run-up, the difference left to right can approach 100 degrees F (the higher temperature is still below the CHT limit). Good news, once airborne the temperature difference quickly decreases and the left and right are equal after a few minutes.
In summary, I am pleased with the results from my oil cooler location and the cowl cooling mods.

DuncanK wrote:I've now flown my Sonex with a UL350i. My oil cooler is mounted on the center-line below the prop, angled (roughly) with the cowl and exposed to ram air. This required quite a lot of modification to the cowl but one advantage is short and simple oil lines to and from the cooler (its not a UL cooler).
I previously stated that I reduced the area and relocated the Sonex cowl inlets. Also, in addition to the standard Sonex side exits, I added two louver exits on the underside of the cowl. The resulting exit to inlet area ratio is about 3.
Oil Temps:
The oil temperatures in flight (based on a few spring time flights) are good. On the ground at full power, the oilT rises quite quickly and the oilT limit is reached after a couple of minutes or so. Taxing, run-up checks, and waiting a few minutes for takeoff does not cause an oilT problem.
CHTs:
I have CHTs on my left and right rear cylinders. On the ground these climb slowly (or quickly at full power) but a left to right difference is evident. After a longish taxi and run-up, the difference left to right can approach 100 degrees F (the higher temperature is still below the CHT limit). Good news, once airborne the temperature difference quickly decreases and the left and right are equal after a few minutes.
In summary, I am pleased with the results from my oil cooler location and the cowl cooling mods.

How does it fly? I am interested in a UL powered sonex. Any videos, pics, or posts you've made or have?

I have about 20 hrs on my Sonex B with UL 350i.
attached is a picture showing how I made the air intake ducts work.The one the right has a lot less clearance but works.

Not a UL however my last aircraft, ATEC Zephyr/Rotax 912ULS, had its small oil cooler mounted on the lower firewall, just above the exit air. Didn't look like it got much airflow BUT worked remarkably well.

My new Sonex Legacy/Rotax 912ULS has had coolant cooling issues on the ground and oil cooling issues in the air - have just complete revised cooling system placement - now have Rotax Extra Large oil cooler (previous Large Cooler) mounted in the exit air flow and the coolant radiator up front, getting fresh air/prop blast.

First ground run yesterday - 35C ambient (Sydney Basin), oil & coolant only got to 75C after extended running ( various checks including carb balance). Have high hopes that my cooling issues will be in the past - will find out next week when we commit aviation.