The International Cessna^® 170 Association

Jim, Pics and a write-up on cowl door replacement would be great! Dave

Ok , careful what you wish for
Previously posted Here’s my LH door. For anyone new to these machines if you don’t restrain the latches when opening the door, the latch will break out the metal on the side of the door. My door had a crack (Ron Massicot pointed out this while judging my plane) quite a few years ago. I just stop drilled it and applied speed tape to the inside. This last year the speed tape cracked and the hinge was worn plus the aft edge of the door wore away, so it’s time to do something.

Looking at the inside of the door you can see a doubler which is spot welded to the door outer skin. the skins are .025. The outer skin rests against the doubler on the cowl that surrounds the door cutout. When the door vibrates those two surfaces suffer. The arrow points to the latch cut-out which broke away because I was negligent in not restraining the latch when I had been releasing it. Notice on the right side latch how little material remains on the doubler because of the latch position. Here's the hole to fill

Here's the new door. It has been fabricated out of 2024-t6 ( a bit stiffer than T-3) and put through a roller to obtain the cowl curvature. The skin thickness I used was .032 for both pieces and it is a bit heavier than a stock door. The doubler has been attached with countersunk rivets I bought new latches at Aircraft spruce P/N H-5000-2 There're advertised as surplus at $46 ea. one of hardest parts of this job is making the cut-outs and making them pretty. New latches ( non surplus are $117 ea.)
Surplus are looking like the deal. Here's the inside doubler riveted on. The original doubler inside is spot welded to the outer skin and after drilling out those welds to save it you'd have Swiss cheese.

I think it might pay for owners to have a look at the condition of their cowl door latches. I thought mine were fine but now I'm thinking they likely have been causing the fretting of the surfaces between the door and cowl. I found when latched, I could press against the body of the latch and the tongue would move about 3/32. Doesn't seem like much but over time and with vibration likely the whole door surround and outer door skin will slowly wear away where the two come in contact. Might be some thing worth checking. The hinge point pin is what wallows out in the latch and can be checked by opening the door, then latching the latch in its closed position and then pressing at the latch hinge point.
Here's a close up of the pin
Also the hinge tongue comes up against the doubler inside the cowl when the door is closed and latched. Might also help to have a look or feel inside and see how much the doubler has worn away. Likely RTV can used to fill the gap if its becoming excessive.

Finished product.. well almost its a bit to cool for the paint. And I might try a test flight to see if the door creeps a bit

Beautiful craftsmanship Jim! Thanks for sharing. Any tricks on making the latch cutouts so nice? Die grinder? Nibbler?

Thanks Gary, truth is the boys at hockey dubbed me "Mac da Hack" and my work well its something like that. Yes, I use a die grinder with a very fine, very pointy cone bit and lots of files. I use a 3m scotch pads to smooth and buff the surfaces and edges.

Lovely work, and I'm sure you have peace of mind knowing that the new door is in excellent shape. Thank you for sharing!

Great work Jim, thanks for sharing. Spruce has the following note for the surplus latches -
" The model numbers may be the same but the depth range may be different from piece to piece. To Insure that customer gets exact sizes, they must order the non surplus version."
Were you able to get the correct depth or did you just install a shim on the back of the cowling? (The parts catalog calls for a H-5000 .032"-.064")

The ones I received appear to be the same as (what I believe) the originals I removed. I’ll take a close-up and add it to this post. The area inside the cowls where the tongue rests will likely be worn away as metal to metal contact over 60 plus years might do just that. Restoring the land area in the cowl with Dow Corning 3145 to take up the gap might suffice in many cases.

Beautiful work, Jim! Using .032 is a good idea, considering how much chafing and flexing the doors experience.

Did you shape the new door by flattening and tracing off the old one, or did you make a transfer pattern?

Did you re-use the original doubler or make a new one? Flush rivet, I assume, not spot weld?

Nice work Jim!
A man of many talents for sure.

Dave I added (by edit) two pics to the thread, one showing the inside showing the rivets, one show the pin that wears out on the latch. Skin placed on top of old skin, (its fairly straight from the bottom up to the latches) picked up the holes at the bottom and the latches for location and for rough dimension then a bit extra (1/8) added everywhere for trimming to fit. I used tape as guidelines when removing metal with files and 3M fine sanding discs on an angle grinder. Only difficult spot to trim is the top of the door where the doubler is longer than the outer skin. The doubler top end location and dimension does not need to be precise.
As for using .032, the added material wouldn't hurt for the countersinking rather than dimpling all the holes and I thought it wouldn't be noticeable but I think it is up close so maybe I'll be doing this all over again
I'm sure real sheet metal types are giggling at all of this.
Sorry for the long post I guess the real message is check your latches and don't let them wear out your cowl.

Thanks, Jim. You've seen my cowl doors -- they're way beyond just broken out at the latches!

The upper cowl I found for ‘98C’s rebuild was from a ‘56 with no right cowl door. Mountain Airframe fabricated this one. (‘98C came to me in 1982 with 4 latches per door. I thought they were all that way until someone asked me why I added the extras). As a possible source of latches, when I stopped in to Mena on my way to the New Mexico convention in 2017, Del had just bought a whole pallet of surplus parts and hardware, including several large bags of new Hartwell latches. He might make an Association member a deal.