FAB compensation for offset carb and engine...

[Michael Burbidge]

For my first fitting of the FAB to the cowl I had the FAB top plate squared up with the carb so that it was pointing straight forward. When I put the cowl on I found that the FAB inlet was way to the left of the cowl inlet. So I put a plumb on the center of the FAB inlet on top plate and found that it was about 1 inch to the left of the nose wheel leg, which I assume is centered. Here's a picture.



So I then removed the FAB top plated and dropped a plumb from the center of the carb, and it was off to the left of the nose wheel leg by 1 1/4 inch. Here's a picture.



I knew the engine was offset, and it looks like the carb is offset on the sump (O-320 D3G), but I didn't know it was by 1 1/4 inch.

So my question is, in fitting the FAB to the cowl inlet, do I just rotate the FAB top plate on the carb mounting plate until the FAB inlet is centered on the cowl inlet? 1 1/4 inches is enough that the front of the FAB will have to be trimmed at an angle since the centerline will be at an angle.

Is this sounding strange, or normal? Maybe the approach here is to just make that darn thing fit. Do whatever it takes.

Thanks for any insight.
Michael-

[erich weaver]

All normal. Point the the FAB at the cowl inlet, and get the rubber baffle material to seal reasonably well around the inlet lips and you should be good to go.
erich

[plehrke]

Originally Posted by Michael Burbidge

Is this sounding strange, or normal? Maybe the approach here is to just make that darn thing fit. Do whatever it takes.

Same on mine. Rotated mine so front of [trimmed] FAB was centered then used baffle material to fill in transition. I also needed to shim it nose down a bit by making a tapered plate to mount on top of FAB

[crabandy]

Same as mine.

I had to make a new mounting plate on the carb so I could slide the FAB to the right. I origially had about 1/4 inch between the side of the FAB and the cowl, after I made the new mounting plate I had 3/4 inch. I moved it as far right as the airfilter would allow.

[WingsOnWheels]

Originally Posted by crabandy

Same as mine.

I had to make a new mounting plate on the carb so I could slide the FAB to the right. I origially had about 1/4 inch between the side of the FAB and the cowl, after I made the new mounting plate I had 3/4 inch. I moved it as far right as the airfilter would allow.

I had this same issue and also made a new top plate to correct. Just dont assume you have sufficient clearance to the cowl. Double check before making anything permanent.

[plehrke]

Originally Posted by WingsOnWheels

I had this same issue and also made a new top plate to correct. Just dont assume you have sufficient clearance to the cowl. Double check before making anything permanent.

I also needed to redo the mixture linkage to fit within the cowl (and have plenty of clearance for engine movement.)

[jdeas]

I had the same unexpected results. I was told by someone on this list that mounting the FAB off-center was not a problem. To get the clearance on the mix I had to both offset from center and rotate the nose!