SonexBuilders.net

Hi Paul

I have enough rubber wing root seal material for your Sonex. I didn’t put any on mine. PM me and we can arrange getting it to you if you want it.

I also have a rubber handle cover (black) for the brake/flap handle if you need one. Both priced the same ;-)

Happy Landings
John
N50NX

Sealing Exhaust Leaks

Jake.....N76ET......your point on my "auto muffler" clamp is well taken........you may be right......but I don't know how the expansion issue is much of a concern with such a short pipe.....in my case, the Onex pipe isn't much more than a "stub"....it is only 8 1/2" long. I don't know how long yours are on the Sonex......on the Xenos they are twice that length.

I may change out this clamp.....it makes for a very tight fit/seal however it is heavy and sure is ugly to look at. Of course the cowl covers it up but when I remove the cowl the FIRST thing my eye goes to.....is that ugly clamp.

Gordon......Onex.....Hummel 2400

I have changed to the CAMit 3300 engine and have no evidence of exhaust leakage with this engine. With the former Jabiru, the leakage was significant. However, when flying with the Camit, I still have the exhaust smell in the cabin. If I open the standard sidewall vents, I do not have the problem. I know, this should be obvious....BUT I believe that it is a matter of PRESSURE DIFFERENTIAL, not leakage. The fuselage is an airfoil! Therefore, it stands to reason that the interior of the fuselage is going to have a lower pressure than the exterior. If the interior is of lower pressure than the outside, the exhaust, being released right at the front of the fuselage, is going to go to the area of lower pressure....the inside! I doubt that we could seal all the "holes" in the Sonex!
I have added canopy vents and find that when they are open, everything is fine....and I'm using a sensitive CO digital meter. Yes, it's cold in the winter!
Ray Krause
Waiex N51YX, Camit 3300 # 0099, 50 hrs, total aircraft hours: 550.

Here is a thread on the wing root seal:
viewtopic.php?f=21&t=2799&p=24501&hilit=Wing+root+tape#p24501
I still can't see your picture.

One more thing on getting exhaust fumes in your cockpit, make sure your exhaust pipes have not been trimmed too short. If they are too short exhaust will get in the cockpit. Also, do put on the stainless steel plate at the lower lip of the firewall shown in the manual to help route the exhaust away from the airframe and to protect the airframe from exhaust residue.

Jake

Hi Paul,

Not sure you'd want to go as far as redesigning the cowling and exhaust system but something I think worth considering is the shape of the cowling and the area where the exhaust exits.

On the Cleanex aircraft we use a much different cowling. The bottom opening is only for the exit of engine heat. Of course the oil breather tube and fuel tank vent is there also. By design the exhaust are separated to each side and the bottom cowling cover pan sits between the dual exhaust pipes.

This set up (I believe) tends to push the exhaust away from the center of the aircraft and thus keeps it from going beneath the aircraft and entering through the rear of the tail cone. I haven't heard of any Cleanex type aircraft having any issues with exhaust fumes in the cockpit.

Not sure if this helps at all but just wanted to pass it along as food for thought ...

Dale Williams
N319WF @ 6J2
Myunn - "daughter of Cleanex"
120 HP - 3.0 Corvair
Tail Wheel - Center Stick
Signature Finish 2200 Paint Job
168.7 hours / Status - Flying
Member # 109 - Florida Sonex Association
https://www.youtube.com/watch?v=1VP7UYEqQ-g

Thanks for the suggestions everyone.

One of the first things I tried was taping aluminum plates, that fit tightly around the exhaust pipes, to the cowl. This was to prevent exhaust gas from going up inside the cowl. The exhaust pipe on the right side is definitely too short. However, I temporarily clamped on exhaust extensions that extended approx 5 inches below the cowl. To my surprise, neither of these changes made a difference.

The change that made the biggest difference was adding a fuel drip pan, and sealing the upper firewall flutes - which I had missed. This keeps spilled fuel from dripping into the cabin, plus blocks fumes. Before I made those changes, the fumes were so strong they would burn my eyes, and change the chemical CO detector black. This was before I ever flew, and wouldn't have flown the plane in that condition.

Next time I get to the airport, I'm going to tape the wing roots, and try sealing the tail better.

BTW, one of the reasons I think that the Bead Roller will work is that when I first wrapped the slip fit with fiberglass exhaust wrap my CO peaked at around 15 PPM on the ground. I thought I had the problem solved. Unfortunately, I think the exhaust wrap may have loosened, and the CO has risen again.

It seems I've just managed to solve the monoxide issue on my aircraft.(Jab 3300). My firewall wasn't well sealed around the top and not in the flutes so I was hoping that I could solve it that way bit it made no difference. Then I realised that there was no seal where the top flange of the fuel filler box (at low cabin pressure) meets the underside of the top cowl ((at high, cowl pressure). I added an adhesive D-seal around the three sides of the flange and had to go to a slightly longer fuel hatch fastener. This seems to have done the trick completely.