Chucker's Sonerai II (minus)

[Raceair]

LOOKS GREAT !!!!!

 

[Chucker]

Found homes for all my cockpit gear. The photo shows my cross country configuration. Check out the mileage to my destination.

 

[Chucker]

Been a long time since my last update...

I'm installing an 1835cc engine and working on the cooling.

As you may remember from my last project, I don't like hot air inside the cowl. On that project I used updraft cooling and ported the hot air out the top of the cowl. It worked well. Without blast tubes, the housing temperature of my magneto never exceeded 110 F when the OAT was 90 F. However, there are disadvantages to updraft cooling...not the least of which is the ugly ducts or fences on the top of the cowl and the open holes for water intrusion on a rainy ramp.

I decided to use downdraft cooling on this project. However, I still wanted to port the hot air overboard immediately. As with the previous design, the entire cowl is pressurized. I built boxes around the bottom of the cylinders and heads. Below each box is a 4" aluminum tube passing down through the cowl.

I intend to route my exhaust through these ducts as well. The exhaust will assist with exit airflow and there should be no additional drag from exposed pipes and exhaust plumes. These will be the only two exits on the cowling.

I'll post a link to this post in the engine forum to allow comments. I believe that only administrators can comment in this forum.

 

[airforcemike53]

Very awesome.

 

[John B]

One concern I have is that during climb for instance, the outlet will be an area of high pressure and may result in not enough flow to cool. May need a lip in front of the outlet to lower the pressure at the outlet to get the flow you need..

 

[Chucker]

One concern I have is that during climb for instance, the outlet will be an area of high pressure and may result in not enough flow to cool. May need a lip in front of the outlet to lower the pressure at the outlet to get the flow you need..

I am definitely planning on a lip.... a Gurney Flap.

I'm thinking about making it controllable from the cockpit....but probably not. I'd rather keep things light and simple. As "Pops" says on the Homebuilt Aircraft forum, "If it is not here, it costs nothing, weighs nothing, and is 100% reliable."

 

[Chucker]

And here is the ugly, draggy part! However, the entire bottom side of the cowl will be closed and smooth and there will be no exhaust pipes hanging in the breeze. Overall, I am expecting lower drag. The Gurney Flaps are fairly large to start. I don't want cooling problems out of the gate. As I see where the head temps settle out, I will trim them down as much as possible. With my last project I made the mistake of believing that the location of the exits (top of cowl) was enough to suck out the hot air and keep the heads cool. The first flight was very short and I went home to design exit ducts. In the end, I replaced the ducts with Gurney flaps and everything ran cool. This time I want to start cool and work backwards toward just right.

 

[Chucker]

Changed my mind. The gurney flap is too ugly. I'm going to build faired ramps in front of the exits to provide the necessary low pressure around the opening. Pictures soon!

 

[bmcj]

All right gentlemen(Do we have any ladies in the group?), well, ladies and gentlemen,

Please step away from the pronouns… no good can come if it.

(I know… it’s an old post. But as long as I’m replying to an old post, I’ll throw in that Dan Gurney was a long time family friend).

 

[Chucker]

My last Sonerai had Gurney flaps on the exits. I tip my hat to Dan's ingenuity,

Even though they look draggy....they really are not. The air backs up on the front side and creates a fairing all by itself....just like running without a spinner.