The International Cessna 170 Association

Our “new” 1955 170B has some typical cracks on the forward part of the upper cowling. Before risking further damage, we decided to undertake a repair that we hope will be a permanent solution to the problem. We’ve built a doubler using a 2-bid carbon fiber layup and plan on attaching it to the cowling using everyone’s favorite cold weld epoxy. Any thoughts or insights before making this a permanent addition to our airplane?

Oh I like it, nice idea.

Ryan, interesting! How are you going to bond the parts together? You probably know already, prop balancing does a lot to prevent cracks like you have.

When you finish it, can you paint it in ‘53 B-model scheme in Insignia Red and ship it to me? I’ll send my “core” via return freight. (Like this)


(Nice idea!)

Lay up a fiberglass insulator layer on there...can be 3/4 oz glass. If you don’t, you’ll get some bad corrosion, particularly because that place can get wet.

That nose bowl should be able to be welded, if need be.

MGS or West Systems both make good stuff. Pick your poison.

Carbon fibre used against aluminium has corrosion issues plus carbon fibre while light and strong and easy to mould to the shape you want ,it does have issues with cracking also due to vibration. I have found using Kevlar is a very good fabric to work with . However you will need special scissors to cut it . I use the “West System” epoxy resins .

Thanks for all the thoughtful replies. We’ve worked extensively with composite materials, but haven’t done much work with aluminum. The corrosion issues are something we will address.

Ryan, I’m not the know-it-all I pretend to be but I’ve never heard of anyone successfully welding these or this particular alloy. 2024 is not generally considered to be repairable by welding. If anyone can do this I’d like to meet/talk to them.

I like the look of that. I have only applied JB Aluminum Weld in a couple of areas on the inside as a rub through barrier, and it has worked very well.

gahorn wrote:Ryan, I’m not the know-it-all I pretend to be but I’ve never heard of anyone successfully welding these or this particular alloy. 2024 is not generally considered to be repairable by welding. If anyone can do this I’d like to meet/talk to them.

You’ve met Jay Baeten, talk to him about it. I didn’t believe it possible either until Jay showed me where he had welded up cracks in his cowling.

Are we all assuming that the nose cowl is made of 2024 T3 aluminium. I would be surprised if it was but saying that I have no idea what it is made of . How ever there is a STC for a carbon fibre cowl for a 170 series aircraft . Again I know nothing about it only seen it in the FAA list of STC,s .
My nose cowl is not a standard cowl but a PMA cowl made out of fibre glass but due to a couple of birds wanting to test its strength ,I have repaired it using Kevlar .its not the easiest Fabric to work with but extremely strong .

I can pretty much bet that the later model nosebowls are a softer alloy given the sharp bends.

Guido Perla welded up his stationary panel with great results. I’ve heard the same about 2024-T3.

Sounds like reaching out to Jay might be a good opportunity for a 170 News article?

ghostflyer wrote:Are we all assuming that the nose cowl is made of 2024 T3 aluminium. I would be surprised if it was but saying that I have no idea what it is made of . How ever there is a STC for a carbon fibre cowl for a 170 series aircraft . Again I know nothing about it only seen it in the FAA list of STC,s .
My nose cowl is not a standard cowl but a PMA cowl made out of fibre glass but due to a couple of birds wanting to test its strength ,I have repaired it using Kevlar .its not the easiest Fabric to work with but extremely strong .

That cowling is also $11K, and is designed for the Lycoming conversions. Sounds cool until the sticker shock!

Choke, cough,cough , $11,000 for a carbon fibre cowl, where is my heart pills ??

I would guess that there is a high probability that Cessna was able to form 2024-O, and then heat treat to T3.

It would not surprise me at all if the original nose bowls are 2024T3.
The Univair PMA nose bowls sure seem to be a lot softer (at least the one I examined a few years back).

But I am just speculating....