Help: FAB top plate edge distance

alpinelakespilot2000 · #1 01-21-2010, 10:32 PM

Kind of hard to describe but I'll do my best...

Per instructions: the FAB top plate (VA-131B) is to be drilled to the 6 holes in FAB carb plate (VA-131A). The carb plate aligns itself straight forward and aft. Then the top plate must be rotated in order to align the forward portion of the top plate with the cowl air scoop.

When I prepare to do this, however, it is impossible to get good edge distance for the six 3/16 holes that attached the top plate to the carb plate because Van's has already cut a filter shaped oval in the top plate. Two of the six holes that I would have to drill in the top plate would have 9/32 or 10/32 edge distance respectively from the precut oval opening.

Two main questions:

1. Is this edge distance issue on the top plate around the precut oval common and, if so, is it OK? Or am I am I incorrectly understanding how the FAB is put together? (With all the FAB failures I've read here recently, this edge distance seems of extra concern.)

2. Since the filter is centered on the oval carb plate (and since the top plate does not align with carb plate) I assume I will have to cut out more of the oval opening Van's provides on the top plate--but in a different orientation--in order to allow the top plate to sit AROUND the circumference of the filter?

It seems like both of these would really be a non issue if Van's would refrain from cutting any oval out of the top plate in the first place, thus letting the builder cut the oval per his/her installation. But again maybe I'm missing something.

I know this probably is hard to follow, but any help on these two questions would be GREATLY appreciated.

Thanks.

flyinmonque · #2 01-21-2010, 11:01 PM

Steve,
Ck your PM.

Brian Vickers · #3 01-21-2010, 11:43 PM

If I understand you correctly...

On my airplane the initial fit up of the FAB was too close to the cowl on one side (inside the cowl scoop). It didn't touch but very close and obviously a potential problem. I remedied this by fabricating a new top plate (the oval plate that bolts to the carb). I moved the whole assembly over 3/8" to the left by relocating the holes. In the process I used heavier gauge aluminum for the new top plate. It is now centered perfectly inside the cowl scoop, on the FAB oval hole, and the inlet. The whole assembly is positioned 3/8" to the left of center on the carb. Unless I told you it is not noticeable. I used the OEM top plate as a pattern so it didn't take long to produce a new one.

Hope this helps

N208ET · #4 01-23-2010, 06:31 AM

I think I used .090 or something overkill, maybe it wasn't that big. Anyway, I moved it over a little too far and the bolt heads that attach the FAB to the Carb would then touch the filter, so I put 2 notches in the inner part of the filter seal to accomodate the bolts, worked out great and gave me a lot more clearance.

Randy