PA12 Boot Cowl Cracking

[Steve Pierce]

I have found the boot cowl cracked where the cowl rails angles attach on both this 150 hp PA12 and a 180 HP Crosswinds STOL PA12. The Super Cub has angles riveted into the boot cowl to reinforce this area. Doing it after the airplane is assembled isn't a terrible job but something to think about when rebuilding one as well.

Cracked boot cowl at the cowl rail attach angles.




Inside the boot cowl at cowl rail channel angle.



Fabricated angle installed to reinforce the area. Installed longer screws after picture was taken.


Angle attachment from the outside, only see the three scew heads.

 

[Steve Pierce]

Hoped this would someone else either identify the problem or avoid it.

 

[aviationinfo]

Thanks for these Steve. The same thing happened with my 12 in approximately the same spot. We fabricated doublers that (hopefully) accomplish the same thing. I like your method. Will take some photos of mine and post when I can.

 

[Charlie Longley]

The last 12 I built I used a PA-14 firewall. It has a forward facing flange with heavier brackets. Piper must have known about this problem.

 

[wingnut]

Steve Pierce ,
On a totally different subject matter, What is typically the spacing on screwing the leading edges on a 12 with the wrap around leading edges?

 

[Steve Pierce]

Steve Pierce ,
On a totally different subject matter, What is typically the spacing on screwing the leading edges on a 12 with the wrap around leading edges?

I am not sure, I have not rebuilt a PA12 wing. A Super Cub has 2 screws on bottom and 3 on top.

 

[Beaverpilot]

So I am building my boot cowl at this time. I have a stainless firewall and was contemplating using some 20 gauge stainless doubler plates rather than the .015ish(1/64) stainless ones as called for. Is there an issue with this that anyone can think of?


Sent from my iPhone using SuperCub.Org

 

[wingnut]

I am not sure, I have not rebuilt a PA12 wing. A Super Cub has 2 screws on bottom and 3 on top.

Thanks Steve, I was needing to know about screwing the leading edge to the spar cap on the back side of the spar. Most of the wings I took apart look like Swiss cheese.

 

[Steve Pierce]

I use a hole finder to pick up the old holes. One screw on each side of the rib.

 

[wingnut]

Oh okay. Mine are all new spars and ribs. I looked at a pair yesterday and they were screwed about every 4" seemed like overkill to me

 

[Steve Pierce]

So I am building my boot cowl at this time. I have a stainless firewall and was contemplating using some 20 gauge stainless doubler plates rather than the .015ish(1/64) stainless ones as called for. Is there an issue with this that anyone can think of?


Sent from my iPhone using SuperCub.Org

I can't think of any and haven't seen any issues in this area.

 

[Yentnacruiser]

if you are making a new cowling i would suggest mounting the top rails closer together and narrowing the top cowl so you have access to the top spark plugs without taking apart the whole cowling. Also makes it easier to access the dipstick. it seems like a lot of work but if you plan on keeping it for a while you'll appreciate it in the long run. One of the downfalls of the PA-12/14.