FAB ulous Ideas??

crabandy · #1 12-11-2012, 08:13 PM

Working on the FAB on my RV7 O-360, the large precut hole in the VA-131B top plate is in the wrong spot! If I center the top plate on the VA-131C (carb mount plate) it is too far left and is touching the cowl and doesn't line up with the snorkel.
Here's a couple of pics of the top plate as far right as it will go, this gives about 1/2 inch between the left side of the cowl and lines up with the snorkel realitively well.

Problem is I don't have enough edge distance on at least 2 of the holes to screw the carb mount plate to the FAB top plate.

I have a couple of ideas, but they usually aren't the easiest....

erich weaver · #2 12-11-2012, 08:41 PM

Seems odd I know, but I believe it is normal that the carb is not quite centered relative to the longitudinal axis of the plane. The FAB must therefore be installed slightly skewed to point it into the air inlet snout on the lower cowling. Others can chime in to confirm/refute this and provide more guidance.
Erich

Ironflight · #3 12-11-2012, 08:57 PM

Definitely slide things around as required to get the FAB to point nicely at the cowl inlet - and if that means making a new plate, then make a new plate. One of the liberating things about building the -3, which had no detailed components or FWF kit - was that we were never confined by having to try and make pre-made parts fit!

There was no top plate to begin with, we just made what we needed that would fit. Having built before made it easier of course, since I new what we needed to end up with.

One good investment for builders are the 2'x2' aluminum stock "squares" from ACS - they are inexpensive enough to order a couple sheets of each thickness at one time, and then when you have them in stock, you are less inclined to use something that isn't quite right - you just make a new piece that fits.

Paul

kevinh · #4 12-11-2012, 09:00 PM

Good advice here. Also, I had to cut a small portion out of the left bottom of the fa b and glass in an inset area to clear the cowl. 500ish hours now and no rubbing or cracked plates...

aturner · #5 12-11-2012, 09:30 PM

It looks like perhaps you are sliding the entire air box laterally while keep it pointed forward? The usual solution is to rotate the axis of the airbox around the vertical axis of the carb so it points at a point in space behind the snorkel, where the fiberglass extension you will build terminates.

N208ET · #6 12-12-2012, 06:08 AM

I remember I used thicker material too, like .052 or something like that. I didn't want it to crack. Furthermore, I centered it in the cowl so far that I had to notch the filter seal to fit 2 bolt heads. I didn't have to notch across the whole top of the seal but about half way into it. Only down side is my filter will only go in one way now, no big deal. 300 hours, no cracks.

Randy
8A

Pat Hatch · #7 12-12-2012, 06:28 AM

Quote:

Originally Posted by N208ET

I remember I used thicker material too, like .052 or something like that. I didn't want it to crack. Furthermore, I centered it in the cowl so far that I had to notch the filter seal to fit 2 bolt heads. I didn't have to notch across the whole top of the seal but about half way into it. Only down side is my filter will only go in one way now, no big deal. 300 hours, no cracks.

Randy
8A

I believe the part comes 0.063 and I made mine out of .090 after the original cracked. Also, adding this little strut is a good idea and it might save you having to replace the plate later.

crabandy · #8 12-12-2012, 08:26 AM

I was originally going to remake the curvy top piece, but may be easier to remake the mount on the carb. I new it was a good time to walk away from the project and wait till morning! Pat, definitely making a brace like yours.
Thanks again!

N208ET · #9 12-12-2012, 10:22 AM

I know it was thicker than the original, I must have used .090 too.

Quote:

Originally Posted by Pat Hatch

I believe the part comes 0.063 and I made mine out of .090 after the original cracked. Also, adding this little strut is a good idea and it might save you having to replace the plate later.

crabandy · #10 12-12-2012, 04:18 PM

I had some spare .063 (it's for the "modular" panel I hope to start soon) so I made an over sized carb mount plate and offset it 7/8 inch. I also made a gasket.

Lots of cowl on and off to get it where i wanted it.

From the bottom, I will cut the hole for the carb last. I wanted to move it more right (left in pic), but didn't want the filter any closer to the bolts.

Finally got it horizontally aligned with the snorkel, now to figure out where the carb heat goes so I can cut/bend to align with the top of the snorkel.

I have about 3/4 inch between the left side of the FAB and the cowl, Is that enough? If it is marginal I can trim/square off the curve and gain 1/2 inch, but I'll have to make another flange and reglass.

What material are you using for the tube brace?