Lightweight Ducting

[Thruster88]

2 hours ago, skippydiesel said:

 

 

My last aircraft ATEC Zephyr, used the two conical  Rotax filters - worked well. (Maxed out at about 125 Kt - Normal /Eco Cruise 100-110 Kt Indicated)

 

The Sonex is a significant step up in performance - outside/cool air supply to the engine, is part of this. (Max Cruise 152 Kt True - Normal/Eco Cruise 130 Kt True)😈

I don't see the down side with ditching the cold air intake and going pod filters. Very slight loss of power at full throttle but how often is that used. For any part throttle operation the throttle just has to be a little more open to compensate for the less dense warmer air. I see coolant carburetor heaters so carb ice should not be a problem. 

[skippydiesel]

1 hour ago, Thruster88 said:

I don't see the down side with ditching the cold air intake and going pod filters. Very slight loss of power at full throttle but how often is that used. For any part throttle operation the throttle just has to be a little more open to compensate for the less dense warmer air. I see coolant carburetor heaters so carb ice should not be a problem. 

If anything the airbox arrangement makes carby ice more likly, than conical filters sucking warmed air.  As you noted, the manifold heaters (claimed to prevent icing) are part of the existing system. My last 912 with just conical filters, never even hinted carby icing. (This is not a claim that Rotax 912's do not experince carby ice)

 

When I was trying to isolate the cause of my leaking carby bowl breathers, I ran the Rotax conical (pod?) filters - no leak.

 

Hot inlet air, will have some (?) performance loss implications. I agree, likly small, however this is not the only consideration. A lot of work & cost, went into the existing air box. One of my flying objectives - economical (fuel used for NM covered) touring, so no unnecessary fuel consumed (throttle setting).  Together ,this means that it would take a genuine safety or performance issue, for me to ditch the airbox.

 

The photo I posted was of the unfinished item - now looks a lot more professional,  sporting a black satin look, heat resistant, ceramic, finish.

 

I have no complaints about the airbox performance -  now that it's not using the carbys for part of its support system. The clearances, due to limited space, is a minor problem that only impacts on my choice of airbox to carby duct, the topic of this thread /discussion😈

[Thruster88]

Thin wall, 2mm, silicon 50mm tube could be an option. Possibly it may only need to be clamped on the carburetor allowing more movement. 

 

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Also it would be wise to plumb the carburetor breather tubes, bearing in mind they need to sense air pressure near the carburetor, so that any discharge of fuel exits the bottom of the cowling to reduce fire risk.