Cracked aluminum cowling

Snowmass said:
An external patch could be made very strong when riveted on. Use about any soft alloy so you can form it to the compound curve. Use thickness to offset softness for strength. Extend rearward and simply cut a hole to clear the camlock OD. BTW when you find out the price of a new cowling you will think they misplaced the decimal point.
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Last I heard, a new cowling from Cessna for a 180 was something like $30K.
 
Snowmass said:
Typical for Cessna. And in 1963 you could buy an entire C-210 brand new (Cuz we bought one) for about $25,000.
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Which at the time, considering inflation, equals about $200k in today’s dollar.
 
Daleandee said:
Selling cowlings at 30K a pop likely helps too ... :D
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I wonder what GM would want for a new hood for a 1968 Pontiac.

When Cessna gets an order for a new cowling for an ancient airplane, they have to pull the drawings and find someone who knows how to form the thing out of 2024-O material, then have it heat-treated, then drill it for all the fasteners. Forming it would involve either locating the dies for it, or a whole lot of English-wheel work. They're not going to make six of them just in case. Just one, and it will be expensive.
 
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Dan Thomas said:
I wonder what GM would want for a new hood for a 1968 Pontiac.

When Cessna gets an order for a new cowling for an ancient airplane, they have to pull the drawings and find someone who knows how to form the thing out of 2024-O material, then have it heat-treated, then drill it for all the fasteners. Forming it would either locating the dies for it, or a whole lot of English-wheel work. They're not going to make six of them just in case. Just one, and it will be expensive.
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Oh I'm sure it costs to make them ... but there's a bit of profit in there too!
 
Cessna never expected these planes to still be flying almost 60 years later. To expect any manufacturer to perpetually provide parts for a product up tp 20 years is one thing, but 50, 60 or 70 years later?
 
Doc Holliday said:
Cessna never expected these planes to still be flying almost 60 years later. To expect any manufacturer to perpetually provide parts for a product up tp 20 years is one thing, but 50, 60 or 70 years later?
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True, but with the volume of older aircraft out there, you'd think there would be a real market for wear items like cowls, which vibrate, crack, get taken on and off, etc. Cessna (or someone) could put together group buys where "First X people to put a $2K deposit down can buy a $6K new cowling that fits the C-XXX.X." Or, you can pay $30K if you need one when we're not producing 15 of 'em at once.
 
kyleb said:
True, but with the volume of older aircraft out there, you'd think there would be a real market for wear items like cowls, which vibrate, crack, get taken on and off, etc. Cessna (or someone) could put together group buys where "First X people to put a $2K deposit down can buy a $6K new cowling that fits the C-XXX.X." Or, you can pay $30K if you need one when we're not producing 15 of 'em at once.
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Market is just too small and not profitable. There have been after market cowls in the past, but due to low demand and the high cost to manufacture I'm not sure they are still offering.
 
kyleb said:
you'd think there would be a real market for wear items like cowls,
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Define "real market." Regardless, you do realize most compound parts, like this ancient cowling assembly, are still basically hand made and require many man hours to produce. Hence the high price tag. Plus each cowling assy only fits a certain S/N spread. No one cowling for every Cessna 172. Same goes for wings, flaps, rudders, etc. and is the same reason there is such a good market for used cowling.
 
Doc Holliday said:
Market is just too small and not profitable. There have been after market cowls in the past, but due to low demand and the high cost to manufacture I'm not sure they are still offering.
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Selkirk makes full aftermarket fiberglass cowlings for Cessnas. About $9k not including cowl flaps.
 
They make Cub cowls, too. They need to move into the current century and use carbon fiber instead of fiberglass. They’d sell cowls based on weight savings alone.
 
Bell206 said:
Define "real market." Regardless, you do realize most compound parts, like this ancient cowling assembly, are still basically hand made and require many man hours to produce. Hence the high price tag. Plus each cowling assy only fits a certain S/N spread. No one cowling for every Cessna 172. Same goes for wings, flaps, rudders, etc. and is the same reason there is such a good market for used cowling.
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My assumption is/was they had stamping or draw dies for the cowlings and would need to recreate those for new ones. But how many C-XXX cowl designs are there? I'm sure Cessna (Beechcraft, Piper, Mooney...) didn't build new cowl tooling every year or two. Maybe when they went from the 0-300 to the 0-320 on the 172, and in similar cases, but that probably wasn't a part that was changed out for S&G's, like say wheel pants.
 
kyleb said:
My assumption is/was they had stamping or draw dies for the cowlings
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On average there are 30+ individual parts to a Cessna engine cowling. All which are hand riveted together over a setup jig. Few items are stamped out. As to how many different cowl variations... who knows. Just look through several Cessna 100 series IPCs to get an idea. One of the hardest things when repairing S/M on a Cessna is to figure which parts can go on what S/N airframe and whether to order them with pilot holes drilled or not. In the end, one usually would fabric the repair parts from stock materials when ever possible.
 
Bell206 said:
On average there are 30+ individual parts to a Cessna engine cowling. All which are hand riveted together over a setup jig.
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I get that part of it, but I was thinking the big bowl shaped upper and lower cowls would be stamped using hard dies or drawn over hard dies. The smaller pieces of the assembly shouldn't require nearly that level of tooling. And yeah, Cessna didn't seem too worried about parts count when they designed the C-xxx's back in the '40's and 50's.
 
kyleb said:
I get that part of it, but I was thinking the big bowl shaped upper and lower cowls would be stamped using hard dies or drawn over hard dies. The smaller pieces of the assembly shouldn't require nearly that level of tooling.
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The part your missing is that the manufacture of the individual parts is the cheap part. A lot of them are standard off the shelf extruded angles, etc. The bulk of the expense/cost is the assembly of all those individual parts by hand which requires quite a few man-hours to layout, trim, rivet, etc to complete.
kyleb said:
Cessna didn't seem too worried about parts count when they designed the C-xxx's back in the '40's and 50's.
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It's not about the year designed or "parts count" as it is the type of construction and structural requirements. Just look at a J-3 or Ercoupe engine cowling vs a 182. Certain types of construction, e.g. monocoque, require a certain number/type of parts to build which still is valid to current designs of that type today.
 
Stewartb said:
They make Cub cowls, too. They need to move into the current century and use carbon fiber instead of fiberglass. They’d sell cowls based on weight savings alone.
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Carbon fiber is a pain to work with AND creates massive corrosion issues. Most cowlings are 6061 because 2024 is not conducive to the forming process for cowlings. The inflight vibrations cause it to become hardened and crack. I have had some success heating the area and reworking it and then patching. Not a good enough welder. Using damaged cowls from salvage yards for preformed multiple curve pieces.
 
Carbon cowls and nose bowls are becoming common for exp Cubs. Isolating for corrosion is simple. A friend up the road about 5 minutes has a carbon fiber airplane parts business and he’s busy. My own Cub has lots of carbon in it.
 
BoButt said:
Carbon fiber is a pain to work with
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I hear this all the time but haven't found that to be true unless you're using the carbon fiber as the final finish. Then every blemish will be seen. Ironically, many of the "carbon fiber" parts aren't 100% carbon fiber anyway, often the carbon is just a top dressing for fiberglass. But it looks cool.

Regarding the corrosion concerns, they are real but I feel they are often overstated.
 
Mtns2Skies said:
Selkirk makes full aftermarket fiberglass cowlings for Cessnas. About $9k not including cowl flaps.
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And there goes any incentive for Cessna to make new aluminum cowls.

Here's another example:

SA62_grande.jpg

The tailcone for the 180/185. Cessna used to make them of aluminum, then switched to ABS plastic. The plastic ages and cracks and falls apart. A new one from Cessna, last time I checked maybe 5 years ago, was around $3900. (Canadian. Maybe $3300 US.) For a plastic fairing. Stene makes them of much stronger fiberglass and sells them for $375 US.

That's where the stuff will come from to keep old airplanes flying. From aftermarket people who get innovative and make a mold for a tailcone, which is basic boatbuilding technology. An ABS tailcone needs an injection mold. An aluminum tailcone involves a lot of skilled forming and heat-treating. Stene makes a lot of PMA'd parts to replace those ABS wingtip, tail and strut fairings. Selkirk makes fiberglass interior parts. Vantage makes ABS interior stuff that's thicker and stronger and much cheaper than Cessna's stuff. McFarlane has a huge array of aftermarket parts. In fact, Cessna resells some McFarlane stuff; it's cheaper for them to buy it than to make it themselves.
 
kyleb said:
I get that part of it, but I was thinking the big bowl shaped upper and lower cowls would be stamped using hard dies or drawn over hard dies. The smaller pieces of the assembly shouldn't require nearly that level of tooling. And yeah, Cessna didn't seem too worried about parts count when they designed the C-xxx's back in the '40's and 50's.
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Big stamping dies can cost millions. Just ask the big automakers. I once talked to a fellow who had made them; it took a lot of machining of huge chunks of steel, then finer machining, then grinding, then dressing with die grinders, all of it forming a die that will produce the part needed after the part springs back somewhat after coming out of the press. That sort of thing involves a lot more than just shaping a die; one has to be able to calculate springback, and if you get it wrong you start making a new die.

For millions of cars, it pays. For a few hundred airplanes, not so much. One cowl per airplane. Many wing ribs per airplane, so dies work OK there.
 
Hand layup and vacuum bag with epoxy resin and fire glass cloth can get very near the efficiency of aluminum. Again someone has to make the molds, but the result will last a lot longer than trying to weld aluminum.

Someone ambitious could create replacement left and right front corner parts only of aluminum cowls so they can be riveted to an existing main cowl sheet. Those areas seem to be the location of most cowl cracks. Small parts could be formed from 2024-T0 sheet aluminum and heat treated to a T42 to get a part that is stronger than the OEM cowl in that region.
 
...An ABS tailcone needs an injection mold.

I think most ABS stuff in airplanes is made from raw ABS sheet material and vacuum or stretch bagged over a wood form. It only needs a kitchen oven to soften and a couple of guys with gloves to do the forming.
 
BoButt said:
Carbon fiber is a pain to work with AND creates massive corrosion issues. Most cowlings are 6061 because 2024 is not conducive to the forming process for cowlings. The inflight vibrations cause it to become hardened and crack. I have had some success heating the area and reworking it and then patching. Not a good enough welder. Using damaged cowls from salvage yards for preformed multiple curve pieces.
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From the Cessna Structural Repair Manual:

upload_2021-3-13_10-37-11.png

The 2024-O (soft) sheet is formed, then heat-treated to 2024-T3, -T4 or -T42 as per service manuals.
 
nrpetersen said:
Someone ambitious could create replacement left and right front corner parts only of aluminum cowls so they can be riveted to an existing main cowl sheet.
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The parts fabrication is the easy part. It's the PMA process you need to complete so you can sell them. Regardless, a lot of parts needed for a cowl repair are either fabricated by the APIA during the repair or are an owner produced part which don't require any of the PMA requirements. It would be hard to create a PMA market when your potential clientele can fabric them on site at a discount to your price.
 
Would they actually heat treat a non-structural part like the nose portion of a cowling? Seems like overkill.
 
Snowmass said:
Would they actually heat treat a non-structural part like the nose portion of a cowling? Seems like overkill.
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That nose bowl takes a beating. Without the heat treating they would wear out much quicker.
 
Snowmass said:
Would they actually heat treat a non-structural part like the nose portion of a cowling? Seems like overkill.
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Yes. Without treatment one good rain storm would leave the cowling permanently marked.
 
RyanB said:
Which at the time, considering inflation, equals about $200k in today’s dollar.
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The scuttlebutt surrounding the price escalation is the cost of product liability insurance accounts for 65% of the OEM price. There was legislation from a long time back that limited the exposure the airframe manufacturer would have, eliminating the ‘cradle to grave’ liability but that was never passed and now we are paying for it even in the used market. As always, the companies don’t pay it, the consumer pays for everything. Hence we pay and pay


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Polarisguy said:
but that was never passed and now we are paying for it even in the used market.
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As mentioned above GARA was passed and works quite well if it covers you. But you are correct about product liability. It is also the reason there are very limited ventures to put a new aircraft model into production in the US. It is what it is.
 
Yet experimentals are very popular and that segment is growing. Some would say the FAA is the problem.
 
Stewartb said:
Yet experimentals are very popular and that segment is growing. Some would say the FAA is the problem.
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No deep pockets in the E/AB segment. And the FAA has tried to jump start things with the Part 23 rewrite. Unfortunately most aviation producers cite, some publically, the US product liability/tort system keep them from putting out new products in the US market.
 
Cubcrafters is a good study. Kicking ass in the E-AB world. They got their start in the certificated world. They sold off their part 23 airplane cert. It’s about making a good product and a profit.
 
Stewartb said:
They sold off their part 23 airplane cert. It’s about making a good product and a profit.
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So if it was so good, why sell the Part 23 side? Probably because of the same reason Piper never cranked up the Super Cub line again. As I said, attorneys don't get rich in the E/AB world.;)
 
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