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circular area in lower cowl

P

prkaye

Well Known Member
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?
 
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.
 
Leave it alone...

...most have plenty of clearance for the alt. pulley, so leave it alone.
 
Yes, it is for the Alternator if...

...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.
 
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
 
Three belts...

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

Regards,
 
erich weaver said:
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
Click to expand...

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

erich
 
Ohhhhhhhhhhh.....Guess my brain got locked into seeing things only one way.

Gonna have to check this out - perhaps I can snub this issue yet.

erich
 
First I have heard the term as well, but by context, my guess is that its a highly technical term developed by NASA rocket scientists for a protruding structure whose primary purpose is to absorb impacts from other objects, thereby preventing them from coming into contact with the more sensitive components - like alternator pulleys.

Hence the phrase, "you've been snubbed":)

erich
 
noelf said:
...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.
Click to expand...

I'm in the process , cowl off in shop, of trying to fix this cosmetic bugger. Do you have any advice as for the best way to achieve this? It's just not very aesthetically pleasing but I don't really see another option short of experimenting with numerous replacement belts and prop removal which is something I want to avoid since in the end it may not solve the problem anyway. Thinking or building a nice clean little hood type bump out that looks like it is supposed to be there.
 
Alternator pulley rubbing cowl

I changed my belt after cowl rubbing to a 3L350W and you'll probably need to lengthen the slot for the alternator belt tension bolt. Mine is a B&C alternator and a 0-320 d2a in an Rv-7. Lots of room now.

Keith Rhea
RV7- 60 hours
 
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