SonexBuilders.net

Bryan beat me to the suggestion. John, I would love to use anything you can write up!


Robbie Culver
Sonex 1517
Chicagoland
Tails and Wings complete - finishing fuselage.
N1517S reserved

fastj22 wrote:Here's an update. We wrapped the cowl in 3M vinyl, the spinner in carbon to match the P-tip and I couldn't resist the Ruby Tip.

Test flying the new cowl with another Jabiru Sonex shows a slight speed advantage. Same prop. Oh, and cooling, its better.

Comments?

Awesome, awesome, awesome, job John!
Love the cowling!

fastj22 wrote:...
I knew my family would not support me building a Panther, so what a quandary.
...

Weren't you building a Pietenpol?

The nose looks great John! Do you have a picture of the whole airplane with the new cowling in place? I'm glad to hear it's working well for you!

Looks good and I am guessing it minimizes the tendency for the spiraling air from the prop to pass up and over cylinder #2 which makes that hottest on most installations with standard cowl.

David A.

David,
Do you think that is because the cowl is tighter or because the bends stop the spiraling? If it was one of those the standard cowl could be improved with fences and so on.

John, how does the weight of the old vs new compare?

DCASonex wrote:Looks good and I am guessing it minimizes the tendency for the spiraling air from the prop to pass up and over cylinder #2 which makes that hottest on most installations with standard cowl.

David A.

That's strange? Cylinder #2, according to the Aerovee manual, is the left front one. This was my coolest cylinder...it normally was at least 40 degrees cooler than the right rear cylinder. Both my front cylinders ran cooler than the rear ones.

DCASonex wrote:Looks good and I am guessing it minimizes the tendency for the spiraling air from the prop to pass up and over cylinder #2 which makes that hottest on most installations with standard cowl.

David A.

Yes its seems so. I pulled out the Sonex baffle boxes and replaced with an open top box that seals against the top the cowl. I needed to replace them anyways as the new cowl sits 2 inches forward of the old one. Initially, I had no inter-cylinder fences and 2,3, and 4 got hot pretty quick. 5 and 6 were very cool. Seems the air just piled up in the back then down. I then put in fences between each head to direct some flow down between them. That helped tremendously. In the process of fine tuning it now. Another benefit of the open top box.

Now #2 is my coolest and #4 my hottest, the rest are pretty well balanced. I'll trim down the fence between 2 and 4 to get a little more flow to 4. When I get back down to the hangar I'll get some pixs and try a write up for the association.

As for weight, its a few pounds lighter. Its mostly .025 aluminum, and the Vans spinner weighs less than the Sonex billet one.

My comments about #2 running hottest seem to be unique the the Jabiru (and CAMit) 3300 installations in Sonex, not the Aerovee.

I like the new design for its extended round Lopresti style intakes which are what I think may help minimize the effect of spiraling airflow.

Those inter-cylinder baffles are definitely needed. Be sure to put them under the cylinders as Sonex recommends and as Camit supplies them on their engines, not on top sop that air is forced to follow around the cylinders. Any cooling air that passes through the system without picking up heat just makes for more air trying to exit from the cowl adding to problems there that compromise the entire system.

I have a slightly extended standard Sonex cowl (using a prop spacer) and modified Sonex air ducts that prevent air from up and flowing up and over #2 which do give good cooling, most days can climb at full power from take-off to 8,500 or so at about 110- 120 MPH without getting close to overheating, but suspect could do better yet.

Glad to see some serious effort at improvement, (that does not compromise safety) not because it is required, but because there is always room for improvement and we are building experimental aircraft.

Behold the turtle, he makes no progress until he sticks his neck out.

David A.

The inter-cylinder baffles (bat wings) under the barrels are in place. No change from the stock configuration. I was referring to inter-cylinder fences which are above heads and direct some flow down on the forward cylinders. These are the ones I'm tweaking to get the temps balanced. Seems to be more art than science.