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Alternator Hole repair Cowl

Jr Hampton

Active Member
Dreaded Alt hole in cowl. Very small hole through cowl 1/8 on the outside. I'm OK with that cosmetically.
Have replaced belt with shorter and alt is at top of adjustment arm now.
want to "fix" inner hole. Thinkin cutting spare aluminum stock maybe 2"x2" square , sanding hole area down, applying Gorilla Epoxy ( as I have some already) and bonding aluminum to the cowl. 1) to fix hole , 2) to have aluminum as rub stop in case alt rubs again. Do you think good idea/work ? Or use a diff epoxy ?
 
Fuberglass repair

I wouldn't. Read Dan Horton's fiberglass posts. He details a repair very well. If you want to add a rub patch, add it after the repair. Scuff the aluminum patch with 80 grit and epoxy it in place then add a layer of fiberglass over it to seal. If it does rub, it won't go through and only require an epoxy flox touch up. I usually drill holes and use clekos to hold aluminum in place. Holes are filled with micro after it cures.
Edit...
I have no experience with Gorilla Epoxy and standard epoxy fiberglass. I would fix it with West Systems 105 fiberglass layup and bond the aluminum patch with G-Flex epoxy.
 
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Fix the adjustment arm length and get a shorter belt….. again. Remove the adjustment arm and drill a new hole at the upper end of the arm for the adjustment arm anchor point below the current bolt hole and cut off the part where the old bolt was. Make sure you leave proper edge distance minimums (5/8” from the center of the new hole) before you make the cut on the arm.

I’m doing the same thing on my ‘new’ RV6 build. I have a B&C alternator and the pulley on the alternator rubs the cowling. I’ve gouged out the inner layer on the honeycomb, but it’s still really close, so I bought a 1” shorter belt. I think it will work, but time will tell. Moving the upper attach point a little shorter leaves a more comfortable adjustment range.
 
I have an O320 fixed pitch RV6-A and got a 14184 alternator with the fan on it . It was barely touching the cowling when I put it on. So, I ground off a majority of the fan blades at a steep angle and left about 1/2 in between cowling and blades. What I did not take into account is how much flex 170 mph puts on that particular piece of fiberglass. The hole in my fiberglass is about 1/2”x2”. I am preparing for that repair now.
 
I have an O320 fixed pitch RV6-A and got a 14184 alternator with the fan on it . It was barely touching the cowling when I put it on. So, I ground off a majority of the fan blades at a steep angle and left about 1/2 in between cowling and blades. What I did not take into account is how much flex 170 mph puts on that particular piece of fiberglass. The hole in my fiberglass is about 1/2”x2”. I am preparing for that repair now.
It is actually positive G load that has the biggest influence on how much change there is in the clearance between the cowl and the alternator pulley.
Since the engine is cantilevered from the back, positive G load causes the from of the engine to sag down.
There has been quite a few RV's that flew for long periods of time with now issue. Then someone started doing aerobatics...

One preventative measure is to use the shortest belt that can be installed. The way to do this is to not get one that can be stretched over the pulley when installing, but get one that must be on the alternator and the ring gear pulley, and then put the ring gear in place on to the crank shaft. This will get you the shortest belt possible.

BTW, at least one of the popular (2 letters) alternator supply companies used to supply a belt that would guaranty a hole in the cowling. That was the case for decades. Not sure if it still is today.
For the best insurance protection from this problem, make sure you are using the shortest belt that is possible to get installed while fitting the ring gear support onto the crankshaft flange as the last step.
 
I noticed today that not only the blades, but the pulley itself has worn a hole through. The pulley seems to be the same size as the old one. A shorter belt seems to be the only option, but there is not room to shorten it much. Then the Fiberglas repair will commence.
 
After flying my RV-4 for a while, I noticed slight contact on my cowl, long before it got into the honeycomb. It came about after I started flying some formation (throttle jockying) and pulling some G's, so typically in normal operation contact was minimal. I made a recess in the honeycomb and layed a few plies to seal it up, then adhered a 1/8" ish piece of red silicone high temperature matting about 2" in diameter to the contact point as a "bumper" Been that way for several years now, and allows the periodic contact without any damage to the cowling. Lots of movement going on with G's and rapid power changes.
 
Make a bubble, graft to the cowl with a scarf joint. Permanent clearance.

Easy to lay up a dome on a smooth plastic ball.
 
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