Cowling Side-Exit Holes

[NWade]

Would anyone out there with a B-model Sonex/Waiex be willing to post a couple of close-up pics of your cowling exits, and maybe provide some dimensions on them (height, width, distance from the rear edge of the cowl, and depth of the scoop on the interior)?

Thanks a bunch,

--Noel
Sonex #1339

[Bryan Cotton]

Noel,
Are you doing this because it looks cool, or is there another benefit you see? I am just curious. My cowl is coming soon.

[mike20sm]

My guess is that when climbing out it allows the cowl exits to vent better?

[NWade]

Bryan -

Mike's on the right track... With a lifting-body fuselage shape, the underside of the Sonex cowling is essentially the underside of a wing - near the leading edge. On a wing, this is an area of relatively high pressure. This is why most Sonex cowlings have a "lip" or "ramp" at the leading edge of the cooling openings - they're being used to deflect that boundary layer of air away from the fuselage (separating the flow) so that a low-pressure eddy is formed behind the lip to pull the air out of the cowling.

That all works fine and there's nothing wrong with doing it that way - as hundreds of flying Sonex & Waiex planes prove. Unless you want to tinker a bunch, it's probably the easiest and fastest way to get your airplane in the air reliably.

However, to my mind it's not the most-efficient solution. Additionally, I am building an Aerovee Turbo and want to provide the best passive convection I can (when taxiing & after shutdown), while still keeping the cowling simple. Side exits should allow for better heat dissipation in this situation, and may also provide improved cooling drag by being in an area with less high pressure than the underside of the fuselage (requiring smaller - or even no - lip at the leading edge of the opening).

The B Model clearly has adopted this cooling system, and a brief email exchange with the factory has convinced me that it should work on my original Sonex as well (despite the slightly different fuselage shape) - but I'm on my own to experiment with it and come up with something that works. I'm hoping to understand the exact dimensions of the B Model's cowling openings so that I can use them as a baseline.

--Noel
Sonex #1339

[drPete]

On a B-model Xenos, the optional cowl vents are parallel 2" from the aft edge of the cowl for a vertical opening of approximately 9-1/2" and 3-1/2" wide. The vents are part numbers SNB-P16-06L & R.

The drawing incorrectly calls for part numbers -P13-05L and -05R in detail P "Locating Optional Cowling Vents".

[bvolcko38]

I am building a Xenos A model and I've always thought that the side cowling vent were a better idea along with moveable side cowl flaps that can be closed for soaring with engine off. That would eliminate a lot of cooling drag IMHO.

[n502pd]

Would anyone out there with a B-model Sonex/Waiex be willing to post a couple of close-up pics of your cowling exits, and maybe provide some dimensions on them (height, width, distance from the rear edge of the cowl, and depth of the scoop on the interior)?

Thanks a bunch,

--Noel
Sonex #1339

I too am interested in the side vents. Are they not simple louvers? I have not heard of scoops on the interior, but maybe so! I do have a 25% larger belly opening with the appropriate seaplane lip installed per plans. I have taken a picture of a Sonex at Osh 16 with the louvers, but did not investigate the interior for scoops.

Joe

[WaiexN143NM]

Hi all,
I purchased a pair of the b vents from sonex. I think they were about $122 for the pair. Fiberglass and gel coated. L & R. They have a flange to mount on cowl. Either glass them in, or i riveted mine on. Yes there is a big scoop on the inside.

WaiexN143NM
Michael

[drPete]

The plans call for "... bonding with polyester compativle [sic] resin".

LOL - The first of several spelling errors.

[n502pd]

Thanks for the replys, gentlemen! maybe in the future after first series of flight tests. And dont worry about spelling...I was never hired as a speller, or writer for that matter!!