circular area in lower cowl

prkaye · #1 03-04-2009, 01:50 PM

There is a circular area in the front of my lower cowl, right side, that is about 4 inches in diameter, where it appears they have cut away the honeycomb and just epoxied. This looks intentional, like it's a cutout for something (landing light maybe?). See the photo below.
What is this?

Mike S · #2 03-04-2009, 01:52 PM

On my 10, this area gives a little bit more clearance for the alt pulley.

YMMV, however, I suspect it is the same on your plane.

pierre smith · #3 03-04-2009, 02:41 PM

......what Mike said

JonJay · #4 03-04-2009, 02:57 PM

...most have plenty of clearance for the alt. pulley, so leave it alone.

noelf · #5 03-04-2009, 03:27 PM

...if when you attach the alternator, belt , and pulley...and then tighten up the belt tension (forces the alternator away from the flywheel)...the pulley, or alternator "might" contact the cowling in this area.

If this happens in your particular installation, then you can cut away some of the cowling and fiberglass-in a "blister" that provides the clearance needed. The lack of honeycomb in this area makes this task somewhat more robust.

It may be that your choice of engine, flywheel, and alternator results in not needing to do anything special in this area. For those builders that need to alter the cowling, Van provided an area that can be modified.

erich weaver · #6 03-04-2009, 03:52 PM

In my particular instance, using a B&C 40 amp alternator and an IO-360B1B engine from Aerosport Power, I thought there was not going to be a problem with intereference with the cowling after everything got installed since I had appx 1/2 inch clearance. I was wrong though - even though there is clearance when the engine is not running, the alternator pulley is making contact with the cowling during operation and/or start up, as can be seen by the abrasion marks. In this case, it is occuring right at the lip of the circular area where there is no honeycomb in the cowl. I have ground down the lip in hopes of eliminating the contact, but it looks like it is still happening. My remaining choices seem to either be to remove the prop and install a slightly shorter alternator belt, or to cut out a ping pong ball size area in my cowl and fabricate a blister patch with fiberglass to make adequate space for the pulley. The first choice is a total pain in the ***, at least for my Whilwind prop, and the second choice is going to screw up my paint job. Sucks.

Bottom line: check your clearance - its not enough to just be not touching.

erich

pierre smith · #7 03-05-2009, 07:08 AM

...is what we borrowed from the NAPA store and returned the other two after we used the shortest one we could...no rubs.

Regards,

Sid Lambert · #8 03-05-2009, 07:13 AM

Quote:

Originally Posted by erich weaver

In my particular instance, using a B&C 40 amp alternator and an IO-360B1B engine from Aerosport Power, I thought there was not going to be a problem with intereference with the cowling after everything got installed since I had appx 1/2 inch clearance. I was wrong though - even though there is clearance when the engine is not running, the alternator pulley is making contact with the cowling during operation and/or start up, as can be seen by the abrasion marks. In this case, it is occuring right at the lip of the circular area where there is no honeycomb in the cowl. I have ground down the lip in hopes of eliminating the contact, but it looks like it is still happening. My remaining choices seem to either be to remove the prop and install a slightly shorter alternator belt, or to cut out a ping pong ball size area in my cowl and fabricate a blister patch with fiberglass to make adequate space for the pulley. The first choice is a total pain in the ***, at least for my Whilwind prop, and the second choice is going to screw up my paint job. Sucks.

Bottom line: check your clearance - its not enough to just be not touching.

erich

You may want to put a snubber on the alternator bracket. The RV-4 guys know all about it. If it's not there you will surely grind a hole in you cowl.

erich weaver · #9 03-05-2009, 09:14 AM

Its not the alternator bracket that is rubbing, its the pulley. Dont see any way of "snubbing" that.

erich

osxuser · #10 03-05-2009, 10:29 AM

The snubber keeps the cowl away from the pully.