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Issues with PA12 cowling

daedgerton

daedgerton

PATRON
Arlington, VA
My cowl on the 12 moves a bit when you push on it. It also appears to be rubbing pretty bad between the top cowl and boot cowl. Are there supposed to be screws that attach the top cowl to the boot cowl? It looks like there are pilot holes... see picture. It seems like if there were screws between the top cowl and boot cowl this would fix my movement issue...

Thanks for any insight!

top-bootcowl.jpg
 

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Mine does not have any screws between the top sheet and the boot. It has a 1" wide strip of that braided cloth anti-chafe material that the top sheet sits against, and there is no undue movement. Whether you screw it or not, you need a chafe strip in there. FWIW, I would NOT use rivnuts. The first time one of them spins (and it will) you'll be hating yourself.
 
What Perry and Mike said. No screws into boot cowl.

Be sure the angle braces between engine mount and lower cowl channels are in place and tight. Also that the cowl channel attachments to the boot cowl are tight, and the cowl channel attachments to the nose bowl are tight.

With all those attachments secure, the cowl shouldn't move at all.
 
Thanks all... I do have a thick piece of chafing tape but the chafing is taking place behind it.

Does anyone have a picture of the "angle braces between the engine mount and lower cowl channels" as stated by Mr. Misch above? I seem to think that the only things in place are the cowl channel attachments at the boot cowl and at the nose bowl....
 
daedgerton said:
Thanks all... I do have a thick piece of chafing tape but the chafing is taking place behind it.

Does anyone have a picture of the "angle braces between the engine mount and lower cowl channels" as stated by Mr. Misch above? I seem to think that the only things in place are the cowl channel attachments at the boot cowl and at the nose bowl....
Click to expand...

3/8” tubes clamped to engine mount, heading down to lower cowl rails


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I remember having a J shaped piece of sheetmetal that was attached to the nose bowl and rested on top of the case halves. I believe that was to help prevent the cowl from sagging. No tellin' where that thing is now, was thinking of building a new one to keep the nosebowl centered on the ring gear.

Perhaps this item aids in keeping the shaking down as well?
 
Same on both sides. At the bottom, where it attaches to the channel, the tube is flattened and bent. You can just barely see the end of the #10 screw in the pic.

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Here are a couple of pics to illustrate the brace tubes coming off the engine mount to support the lower channel. Not the best details but they’re what I have. They’re the blue tubes with the “right” labels on them. With those supporting the channels on both sides the lower cowl and nose bowl are very solid, as are the top channels. If the top cowl and side cowls are moving your top channel sockets and fasteners must be wallowed out. Or the channels move at the firewall attach angles.

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Last edited:
PerryB said:
Mine does not have any screws between the top sheet and the boot. It has a 1" wide strip of that braided cloth anti-chafe material that the top sheet sits against, and there is no undue movement. Whether you screw it or not, you need a chafe strip in there. FWIW, I would NOT use rivnuts. The first time one of them spins (and it will) you'll be hating yourself.
Click to expand...

I totally agree that there are no bolts at this connecting point, certainly on my (very original) PA12 and it also has the (rather tatty and tired now) braided anti-chafe material. When a passing Cub expert said that removing the hinged cowlings bolts and the nose bowl bolts would allow the top cowling to come off, I was incredulous (and a bit disbelieving), as the rear joint (the one you're asking about) was soooooooooooooooo solid, but he was totally right!!!!

On the RivNuts, these have become a great and trusted friend and indispensable for easy to install fixed/captive/lock nuts whatever you prefer to call them :) Just drill a hole, use the RivNut insertion tool and the job's done!! Sure they CAN spin, but if the installation is done correctly and the bolts are tightened up WITH SYMPATHY AND SENSITIVITY spinning can be avoided in my experience-for some reason, RivNuts seem to be prone to a kind of false cross threading, so the minute the bolt feels tight and still has some way to go, back it out completely and try again until it feels easy all the way in, works for me :) If the RivNut DOES spin, just drill it out and put in another one-5 minute job!!!!
 
stewartb said:
Here are a couple of pics to illustrate the brace tubes coming off the engine mount to support the lower channel. Not the best details but they’re what I have. They’re the blue tubes with the “right” labels on them. With those supporting the channels on both sides the lower cowl and nose bowl are very solid, as are the top channels. If the top cowl and side cowls are moving your top channel sockets and fasteners must be wallowed out. Or the channels move at the firewall attach angles.

View attachment 38291




Sent from my iPad using SuperCub.Org mobile appView attachment 38293View attachment 38294
Click to expand...

Awesome. Thanks for posting pictures. I'm about 90% sure that mine does not have the brace tube coming off the engine mount... If that is the case, I need to get those on ASAP. Is there a Univair P/N for the braces?
 
I don’t know about catalog parts. It seems like the best way is to make your own to fit your cowl, your engine mount, and your exhaust routing. You can see how mine land at a different place on the channel on the left and right.
 
It’s just 3/8” tube you beat ends flat and cut to length you need. Label them for left or right.


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My cowl made by Clyde Smith and my original Piper cowl do not have a rolled trailing edge like yours, and did have the one inch chafe tape glued to the bottom of the rear top cowl, I’ve also had some very nice attach brackets welded up that machine screw to the upper and lower firewall that secure the cowl channels, if I where inclined to my cowl fells like I could sit on it and it would hold my 190 lb butt!


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Gents,
That's why this is one of the best forums out there... Annual is due at the end of the month so this is a great time to get this fixed! Thanks again.
 
Philly5G said:
If the RivNut DOES spin, just drill it out and put in another one-5 minute job!!!!
Click to expand...
Not when the screw is stuck in the rivnut with the part which the screw is holding between the head of the screw and the rivnut. And there are also a gazillion other screws and rivnuts already holding the parts together. :bang
 
skywagon8a said:
Not when the screw is stuck in the rivnut with the part which the screw is holding between the head of the screw and the rivnut. And there are also a gazillion other screws and rivnuts already holding the parts together. :bang
Click to expand...

Yes, that's a REALLY good point :) When I've had a spinner, I've been able to access the back of the Rivnut and hold it still with Mole Grips or similar and wind the bolt/screw out and then drill it out. But, I've only had a couple of spinners.

On the same tack, what happens if you're using a more conventional riveted in lock/stiff nut and it cross threads etc? Sounds like another world of pain!!!!
 
algonquin said:
Philly, if you like RivNuts that much try rivet in nut plates,lol.
Click to expand...

Does this question (from the RivNut spinning reply in this thread) apply in this scenario?!! On the same tack, what happens if you're using a more conventional riveted in lock/stiff nut and it cross threads etc? Sounds like another world of pain!!!!
 
Philly5G said:
Does this question (from the RivNut spinning reply in this thread) apply in this scenario?!! On the same tack, what happens if you're using a more conventional riveted in lock/stiff nut and it cross threads etc? Sounds like another world of pain!!!!
Click to expand...

you pray, and tap it partway ... not all the way through, so it still locks.... depending on it purpose, some things you wouldn't want to try that for....
 
So just following back up on this... Looks like after all I did have the angle braces in place. Need to put some better clamps on them. I think the root of my problem is actually how the cowl channels are attached to the firewall. My angle brackets are very flimsy. The previous owner did not use the correct ones I believe. I think by getting a stiffer brackett in there it might help me out a ton...

Is there an A&P near DC area (plane at KHEF) with solid PA12 / 18 knowledge that could help me get this fixed? Plane is due for Annual as well! Thanks!
 
daedgerton said:
So just following back up on this... Looks like after all I did have the angle braces in place. Need to put some better clamps on them. I think the root of my problem is actually how the cowl channels are attached to the firewall. My angle brackets are very flimsy. The previous owner did not use the correct ones I believe. I think by getting a stiffer brackett in there it might help me out a ton...

Is there an A&P near DC area (plane at KHEF) with solid PA12 / 18 knowledge that could help me get this fixed? Plane is due for Annual as well! Thanks!
Click to expand...

Here are pictures of the channel brackets I had my welder make up for me, they’re rock sold! Tim. I can’t get my photos to upload in this message, if you’ll send me a regular email address, I’ll forward these pictures.


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