Aeroovee to Rotax mount conversion???

[Zack]

From Sonex's webinar, they chose a similar setup but used a Toucan exhaust without a final merge, so it's really two 2-1 exhausts with a center line exit.

Here's the video I was referring to: https://www.youtube.com/watch?v=OzNc-DfczJw&t=1s

However, I noticed when the one week wonder flew they chose a more direct approach out of the cowling. I wonder why they made the change.

[xeriotti]

From Sonex's webinar, they chose a similar setup but used a Toucan exhaust without a final merge, so it's really two 2-1 exhausts with a center line exit.

Here's the video I was referring to: https://www.youtube.com/watch?v=OzNc-DfczJw&t=1s

However, I noticed when the one week wonder flew they chose a more direct approach out of the cowling. I wonder why they made the change.

Easier and much faster to do.... Gets the work done. All other exhaust configurations are oriented either to quietness, interior comfort and respect for other peoples hearing.....or... Just performance at expense of extra cabin noise and guaranteed neighbors complaints XD


My aproach on the cowling will be a little bit off plans... Im going for a more streamlined version, using the original cowling is out of the table.... has nothing to do with the 912 shape and lenght from firewall to the prop hub...

[Skippydiesel]

Hi Xeriotti - On cowling matters;

You may be surprised & frustrated by how much time you may spend on getting your cowling to perform correctly - its not just about looks & speed its also about temperature/ventilation performance

Pretty much had my Sonex finished by about Match this year - still hasn't taken to the air .
Why?
Cowling issues. Have designed and installed my own cowling. Looks great BUT I am not happy with the engine temperatures.
Have been cutting extra holes in my cowling & have fitted an electrically operated cowl flap. All this has taken months months of (unexpected addition) work.
May now have the temperatures sufficiently under control to contemplate test flying - we will see

[xeriotti]

Yes I know!!! Ive been working lowering temperatures in other types of aircraft and i know the problems i may be facing... My idea is to streamline the fron as much as possible... And adding a big naca vent on the left side of the plane, ducted directly into the water radiator... positive pressure on the front and vacuum from the cowling flap on the back...cant go wrong with that recipe... My oil cooler is already installed its bigger in area than reccommended. I will monitor the oil temperature... If i need to lower it i will cover partially with aluminum sheet....if i need to lower i can duct direct airflow from the side of the cowling intake.

There are guidelines to follow, but in the end to get it perfectly dialed...its trial and error.

[Zack]

I wish Sonex would be more public about their efforts to develop the Rotax firewall forward package. I think they made the decision to work within the current cowling early on and are constrained further by the tri gear option with the nose wheel firewall forward. Drawing air through a pair of stacked oil and coolant coolers using the two side vents doesn't seem adequate based on my poor analysis of other flying Rotax powered aircraft. Maybe Sonex thinks this will work due to the higher airspeeds this airframe has versus many other Rotax powered aircraft? This split design does avoid the space constraints of placing oil, coolant and nose wheel on the centerline, plus developing cowling "blisters" to accommodate the cooling. Perhaps running the exhaust to a single central exit by the firewall raises temps in the cowling too much? Easier and faster is also another good reason for the change!

Skippy, I worry if my cooling solution will work as well. I have a separate radiator duct that should be adequate. If it isn't, wow that's a major change to enlarge. I have two Sonex side vents to depressurize the cowling that had to be further opened to match the curvature of my cowling. The air moving through these vents will cool the oil cooler, air cooled parts of the engine, and remove exhaust waste heat. If Sonex is successful, then I will have more cooling drag than necessary.

Xeriotti, another reason the original cowling is out of the picture appears to be your spinner size! Are you doing a constant speed or ground adjustable propeller that needs the extra size? Regarding your exhaust exit, will you do a streamlined exhaust tunnel with the bottom of your cowling, or will the cowling be flush with the belly and the exhaust angled into the airflow?

[Kai]

My aproach on the cowling will be a little bit off plans... Im going for a more streamlined version, using the original cowling is out of the table.... has nothing to do with the 912 shape and lenght from firewall to the prop hub...

[/quote][/quote]

Yup!

The Sonex cowling for the 912 is a puzzle. What shot me down was making room for the fairly bulky R912 muffler in combination with equal length exhaust piping from the cylinders. With my aversion for composite work I elected to go the aluminium way. Some less diplomatic soul labeled the end product´function over form´: I can´t say I totally disagree!

I started out with just the side outlets as suggested by Sonex- this did not work for me. I then rebuilt the cowling with bottom outlets as well- with these outlets flush with the cockpiten floor: success!!

[13brv3]

Until there's a factory tested FWF solution, there will never be any two alike. You guys should be glad you have all that extra width to work with. For the Onex, I used the brute force single scoop on the bottom method that directly feeds the radiator and oil cooler behind it. No cooling issues yet, but more HP is coming soon...

Rusty

[xeriotti]

I wish Sonex would be more public about their efforts to develop the Rotax firewall forward package. I think they made the decision to work within the current cowling early on and are constrained further by the tri gear option with the nose wheel firewall forward. Drawing air through a pair of stacked oil and coolant coolers using the two side vents doesn't seem adequate based on my poor analysis of other flying Rotax powered aircraft. Maybe Sonex thinks this will work due to the higher airspeeds this airframe has versus many other Rotax powered aircraft? This split design does avoid the space constraints of placing oil, coolant and nose wheel on the centerline, plus developing cowling "blisters" to accommodate the cooling. Perhaps running the exhaust to a single central exit by the firewall raises temps in the cowling too much? Easier and faster is also another good reason for the change!

Skippy, I worry if my cooling solution will work as well. I have a separate radiator duct that should be adequate. If it isn't, wow that's a major change to enlarge. I have two Sonex side vents to depressurize the cowling that had to be further opened to match the curvature of my cowling. The air moving through these vents will cool the oil cooler, air cooled parts of the engine, and remove exhaust waste heat. If Sonex is successful, then I will have more cooling drag than necessary.

Xeriotti, another reason the original cowling is out of the picture appears to be your spinner size! Are you doing a constant speed or ground adjustable propeller that needs the extra size? Regarding your exhaust exit, will you do a streamlined exhaust tunnel with the bottom of your cowling, or will the cowling be flush with the belly and the exhaust angled into the airflow?

I love everything about the Sonex/Waiex...but always fantasized about putting a big prop cone to make it more... pointy XD Its for pure looks, and thats something people may like or not. I think i will like it. Im going for a fixed pitch propeller right now.

My idea is to protrude the exhaust tube a couple inches, cut is slanted to match the airflow.

Stacking radiator is not a good idea.... I will try to mount them so one of the side faces towards a low pressure area and i will either direct airflow into it....or for more efficiency duct directly into the radiators.

[xeriotti]

Been off the forum for a couple weeks!!! Sorry.... The Rotax install is almost done!!!

Im using a radiator from a Volkswagen Gol... Its a supplementary radiator that i changed the inlets to fits rotax size and orientatio nof my setup... I custom made a radiator mount...here it is



I already got all my wiring done... And my instrument panel is complete and ready to ribet in place once i check theres no anything wrong uner normal operation.



An this is how the install looks now... :) Im happy bout the outcome of this project

[Bryan Cotton]

That looks awesome!