Corrosion of the Rear Spar Carry Through

[c170b53]

Sorry David I just read your signature. Your' working on a 52

[bagarre]

Maybe I'm not crazy after all.
The IPC shows two different part numbers. This might be the difference between them.

[Ryan Smith]

David,

S/N 20408 has the cutouts/recesses in the skin you show. I won't guarantee the airplane has never had the wings off, but I'd put a large sum of money that they haven't before 1986 and I can guarantee they have not been off since 1986.

[bagarre]

I wonder if it was only the 170A's that had the straight sides.
After seeing Aryana's photo, the purpose of the cut outs are pretty obvious - to avoid the fuel tank cover screws.
Without my wings on, that was not obvious.

wing.jpg

[gfeher]

David, once you clean out the insides of the spar channels, what, if anything, are you going to use to protect them for the future? Primer I assume. Anything else? Just curious in case I need to do this some time.

Here's a handy summary that I found on the Internet identifying common corrosion prevention compounds in aviation use. It's missing a few other common ones, like ACF-50, but you may still find it useful.

Corrosion prevention compounds.pdf

Note that the Dinol (Dinitrol) products are now Ardrox (e.g. Dinol AV 30 is now Ardrox Dinitrol AV 30).
It can be found here on the Internet: http://www.corrosion-doctors.org/Inhibitors/CPCs.htm

[bagarre]

I plan to use an epoxy primer and top coat with a single stage urethane on the insides of the channels...the same stuff the whole interior, bottoms of control surfaces and other difficult bits to polish will be painted with. that should make them good for another 60 to 100 years

[gfeher]

I like that! Great idea.

[hilltop170]

I wonder if it was only the 170A's that had the straight sides.
After seeing Aryana's photo, the purpose of the cut outs are pretty obvious - to avoid the fuel tank cover screws..........

I'm working from memory here but I think my 170A has clearance holes in the cabin top skin which is straight sided and does not have the cut-outs. The gas tank cover screws go thru those clearance holes.

[GAHorn]

There were FOUR DIFFERENT part no's used for top cabin skins over the years. The 170 used 0511114-2, the 170-A used 0511114-3, and the 170-B thru SN 20435 used 0511114-4, and subsequent SN's used 0511114-5. The B-models have the cut-out. The other differences were more minor apparently.

It is NOT GOOD PRACTICE to use the IPC for identification or assembly of the airplane, as there are numerous inaccuracies and errors. The IPC is NOT A MANUAL.

The IPC (Illustrated Parts Catalog) is a CATALOG.... purely for ordering parts.

[Ryan Smith]

[/size]
The IPC (Illustrated Parts Catalog) is a CATALOG.... purely for ordering parts.

[bagarre]

[/size]
The IPC (Illustrated Parts Catalog) is a CATALOG.... purely for ordering parts.

jiFfM.jpg

[GAHorn]

I know it guys. But you guys come here often and read my pontifications regularly. New-comers come here, read one post. Sometimes that post is by an experienced aircraft-repairman ...who states is wrong, and they believe every word. Then, if everyone's lucky... I'll get a phone call wanting to know why their fuel valve won't shut off or why their elevator cables don't fit like the illustrations, etc etc. and I have to say it again.

In short, I'd rather repeat myself here where it'll be read more frequently than to have someone get hurt because they picked up a tidbit here and don't see the whole picture. If the Assoc'n has a Mx discussion forum, then it also has an obligation to not allow folks to put out dangerous stuff. (If they don't read all the topics, that means they also didn't read the disclaimers.)

Example: HERE is what was posted in THIS thread, which implies the document is accurate and useful for illustration and assembly:

I have never seen a 170 cabin top like you have pictured. I have done two, and both had right angles on all four corners. Not sure why yours looks the way it does. If you look in your parts manual for the year of your model you'll have a picture which will verify what your's should like. I am not comfortable telling you until you verify it in the parts manual. If you don't have a parts manual, I am sure there is probably a PDF copy on the internet. Both times I took the cabin top off I was happy with the access to the carry through spars. I was able to clean, epoxy prime, and seal with Dinol. Hope this helps. Take care and Merry Christmas. Mike

Therefore, I felt that THIS thread deserved another caveat about the IPC.

[Ryan Smith]

My post was a joke about using the IPC as it was originally intended - to buy parts from Cessna. Rarely does one do that these days. I've found the IPC to be an invaluable document.

[GAHorn]

Yah... I get it. Both of the responses were funny. It's just difficult on the I-net to know when folks are jesting and when they are jousting.

[bagarre]

Is there an easy way to buck the three or four rivets right above the aileron pulleys?
It's really tight in there...maybe a long bar sideways? Or do I need to remove the pulley brackets to get at them.