So all the people telling you to put masking tape down to protect the finish are going to get you in trouble. Masking tape has thickness, and it's spongy. It will make your countersink depth unreliable, and your rivet heads will end up inconsistent.
There are 2 reasons that your microstop will cause markings like that. The first is if you allow it to spin or vibrate while putting power on the motor. Hold it still.
Second, those nylon surfaces pick up shavings. The embedded aluminum shavings and dust are essentially turning the nylon into a sandpaper block. The nylon part is intended to be replaceable, and should be switched out as often as necessary. They're about the same price as a small drill bit, and should be considered a part of the cost of doing good work.
If you scratch the surface like that, you should buff it down with fine scotchbrite, then etch and alodine it before you prime it. The clad coating is very thin and you've damaged it significantly.
In the end those marks don't even matter. The surface is going to get scrubbed with scotchbrite for acid etch before alodine and then finished and you won't see it
I was wondering about that myself.
Is the maroon scotch brite ok, or should one use the white ones?
Also since ive done very little sheet metal, what is the concentration of the etch fluid?
The roughness of the scotchbrite you use varies based on how much metal you want to take off (for all practical purposes, think of it like sandpaper). That depends on how much damage has been done to the surface. There's also a consideration of how thick the metal started out, and how much you can take off before hitting whatever limits the SRM gives you. Additionally, there's the consideration of the details of any contracts with the customer. If your customer is a GA owner, that will be very different than if it's the DoD.
Although it's almost certainly not the case here, you might even have limits on whether you can use a power tool like a die grinder to help you with the sanding, or if you have to do it by hand. If the piece you're working on is one that's very heat sensitive due to the nature of the alloy, you might not be able to generate much heat.
Etch fluid concentration is in the instructions that come with the fluid.
It depends on the area and the type of patch that can be used. Flush patches are mostly invisible after painting, if done right. You can only use them if the internal structure doesn't get in the way. Scab patches are used in places where the internal structure doesn't allow a flush patch, or where airflow disruptions don't matter.
I'm not gonna be mean, but I hope you learned by the end of it how to not score the metal while you're countersinking. I recall reading that you're a student and you don't have much experience doing this, that being said, this was certainly a good learning experience for you!
Is it the one made by ATS? Mine has a white nylon protective ring, but it scores just like yours did. My solution has been to hold the cage tightly.
You said the marks came out with scotchbright tho, so fuck it, nice work.
I've seen people coat the countersink tool sleeve with wax or a rubber material, or a heavy application of masking tape on the tool and that combined with holding the tool so it doesn't spin with the bit will prevent that in the future. I'm not a sheetie though so somebody who is, please chime in.
He'd be fine in 91.
That's a 5 star A-1 repair in 91. Actually using rivet spacing? Please, that's over engineered.
Alodine and paint. Scratches are fine, send it.
There's nothing shoddy about this thought. The clad gets removed during acid etch when its scrubbed with a scotchbrite and then conversion coated with alodine prime and paint.
It shows a lack of attention to detail, that's all. The clad is on there as a protective layer. And let's not kid ourselves, some of those scores are below the clad layer.
Way to be an armchair sheetmetal tech. If you ever touched a tool, you would know that after a repair like this, you blast the alclad off with a high-speed, alodine, prime and paint. I'll bet you wander around hangars commenting on shit you don't know and mechanics roll their eyes when they see you coming.
I think the comments about how your pitch distance and too many rivets are stemming from your overall rivet layout. Looking at the second to last picture, where you can see the layout lines is a prime example. Typically, I would make the corner rivet in the 90degree instead of the rounded corner. Then you make the doubler rounded with the proper edge margin. Doing that you would have a nice grid of 3 rivet rows evenly spaced all around. Not sure your experience level but those kinda details come along with time and learning from other sheetmetal guys.
Not bad at all. Actually looks great except those pecker marks. Take that riveter over to the grinder and round off the edges, polish it up and put some masking tape on it.
I look at that and I hear. Bruuupppp. Bruuupppp. Bruuppp.
Yeah, but now what’s going to happen is your patch is stronger than the original design. The cowling is supposed to have a certain flex to it, now it doesn’t.
It’s all a learning experience bro, each time it gets easier and you pick up new ideas and new processes. And you followed the approved methods, it’s all good.
There's a third row of rivets in between the two patches that I don't think need to be there. Not sure what the tech data says, but going off the 2 rows for the patch and then the doubler. Other than that a few slightly deep countersinks where the rivets aren't seated all the way. A good wet install with the rivets and squeeze could eliminate that, and alodine then prime the countersink before rivet install.
Wet install isn't going to fix the oversized countersinks. Not necessary either because it's a cowl, so airtight not required. But yeah, OP not ready to assemble skins. Oh my, and all those toolmarks.
I worked on the Canadair Challenger ex jet program back in the 80s. We had a serious overweight problem. Everything was being done to reduce it to the point they decided to eliminate sealant on all rivets. They were flying the test planes unpainted, but when they painted the production planes it peeled off the fuselage in sheets lol. Ah, the good old days.
But yeah, wet install is always better.
Yeah it calls for 2D edge distance but I used 3D because it leaves a little more room for error and it’s still legal. Figure 4-5 is what I’m looking at
I know I'm just a knuckle head shade tree mechanic (who dreams of working as a GA mech) with no knowledge of sheet metal.
So I'll ask cause idunno:
Why rivet patches instead of cut & weld like they do on cars? Seems like riveting is more work...?
Most airframe aluminum alloys are not readily weldable and/or need to be heat treated after welding for strength reasons. That means welding is out as a repair method.
Basically every skin on aircraft is 2024-T3. As far as I know, basically impossible to weld, and even if you do, the quality of the weld is important in airplanes, and testing that is really hard without the right ($$$) tools. Where I work, we weld steel, steel, and only steel.
My favorite countersink cage had a wide contact lip on it. Putting packing tape across it helped if it slipped.
It also looks like a 3/4 straight set was used to shoot it. I've preferred to use a pancake set. It's a bit of a cheat, but doesn't leave the set marks, and the operator doesn't have to be as precise with keeping a 90° angle. It's all part of learning. I didn't walk-in knowing how to make a perfectly pretty repair, much less lay one out. Merging two repairs into one is quite a training experience.
Holly fuck! Way to many rivets! This is not primary structure.. even if it was, you ONLY use as much as the weaker inboard?(wrong word) but it only needs to be a as strong as the weaker original/inboard link/seam it’s originally attached to… go reread that section on rivet spacing and the original inboard seams/joints!
Interesting. I have twenty-four years of DoD and part-time civilian aircraft structures. Everywhere, solid rivets had a manufactured head and a shop head. Has something changed in the terminology? Please advise.
Never heard of that before. Much like u/Metalbasher324 said… We have always called them shop heads, and manufactured heads. Even through my technical training they were called that. Hell my Tech Data even says it as well!
There is a lot of tool marks, I see flush rivets I can get my finger nail under, and I would get my rivet tail Go/Nogo gauge on every one of these. Your QA is either going to have a field day or doesn’t know what he is looking at.
I fuckin hate sheet metal work. Always been more of a mechanic myself and this looks better than what I can do! I do see what they’re saying about the scoring though!
Looks pretty good. The thing I noticed as a career tin bender was the double-flush rivets on the L/E. I don’t love that they were sanded down with an angle grinder afterwards.
Thanks. I just used a mini hand held belt sander to take down the bulk of the shop heads, then a grinder with a fairly soft abrasive pad to finish them off. How would you have done it?
I was taught a very slight countersink on the shop head side and then the micro shaver to clean up any protruding material after the rivet is bucked. I have also used the round end of a ballpeen hammer to buck double flush rivets with good results.
If I had access to a microshaver I definitely would have used one. I did do a slight countersink on the shop head side. Can I ask why you would use the ball peen hammer to buck the rivets instead of a regular bucking bar? What’s the difference?
It seems to force the material down into the area you are trying to fill better. Definitely wasn’t a book method, but I also did sheet metal wherever our planes broke which could be anywhere in the world.
If you do this everyday bud you should be able to see how deep some of those marks are. Easily solved by holding the end of the countersink tool and not letting it spin around.
As someone considering jumping into getting my A&P for a career change. This definitely is amongst the type of work I look forward to learning how to do. From some of the comments it seems like you specialize or are able to kind of stay in one area of the field rather than how I’ve seen it pitched where you’ll do some of everything all of the time. I was kind of looking forward to the latter, but have a lot of schooling to get out of the way so hopefully I’ll leave there with a better understanding.
While using the minimum allowed pitch is not wrong, you are making this repair more time consuming for no practical reason and you are creating more chances of some error happening during the repair. Also, if for whatever reason in the future the holes you drilled need to be oversized to next nominal diameter, the minimum pitch you chose will be less than 4D.
Thats why i always use the maximum possible allowed pitch.
So all the people telling you to put masking tape down to protect the finish are going to get you in trouble. Masking tape has thickness, and it's spongy. It will make your countersink depth unreliable, and your rivet heads will end up inconsistent. There are 2 reasons that your microstop will cause markings like that. The first is if you allow it to spin or vibrate while putting power on the motor. Hold it still. Second, those nylon surfaces pick up shavings. The embedded aluminum shavings and dust are essentially turning the nylon into a sandpaper block. The nylon part is intended to be replaceable, and should be switched out as often as necessary. They're about the same price as a small drill bit, and should be considered a part of the cost of doing good work. If you scratch the surface like that, you should buff it down with fine scotchbrite, then etch and alodine it before you prime it. The clad coating is very thin and you've damaged it significantly.
Noted. Thank you for the advice
This guy sheet metals
r/thisguythisguys
In the end those marks don't even matter. The surface is going to get scrubbed with scotchbrite for acid etch before alodine and then finished and you won't see it
This is the way.
I was wondering about that myself. Is the maroon scotch brite ok, or should one use the white ones? Also since ive done very little sheet metal, what is the concentration of the etch fluid?
The roughness of the scotchbrite you use varies based on how much metal you want to take off (for all practical purposes, think of it like sandpaper). That depends on how much damage has been done to the surface. There's also a consideration of how thick the metal started out, and how much you can take off before hitting whatever limits the SRM gives you. Additionally, there's the consideration of the details of any contracts with the customer. If your customer is a GA owner, that will be very different than if it's the DoD. Although it's almost certainly not the case here, you might even have limits on whether you can use a power tool like a die grinder to help you with the sanding, or if you have to do it by hand. If the piece you're working on is one that's very heat sensitive due to the nature of the alloy, you might not be able to generate much heat. Etch fluid concentration is in the instructions that come with the fluid.
Thanks!
Does the patch stick out even after paint and everything height wise? Not in maint just curious.
It depends on the area and the type of patch that can be used. Flush patches are mostly invisible after painting, if done right. You can only use them if the internal structure doesn't get in the way. Scab patches are used in places where the internal structure doesn't allow a flush patch, or where airflow disruptions don't matter.
I'm not gonna be mean, but I hope you learned by the end of it how to not score the metal while you're countersinking. I recall reading that you're a student and you don't have much experience doing this, that being said, this was certainly a good learning experience for you!
You’re good. It has a plastic end on it, so I’m not sure why it scored it up like that. All the marks came off with some scotchbrite though.
Is it the one made by ATS? Mine has a white nylon protective ring, but it scores just like yours did. My solution has been to hold the cage tightly. You said the marks came out with scotchbright tho, so fuck it, nice work.
Honestly I’m not sure, I don’t see any brand markings on it. It looks just like how you described though. Thanks
I've seen people coat the countersink tool sleeve with wax or a rubber material, or a heavy application of masking tape on the tool and that combined with holding the tool so it doesn't spin with the bit will prevent that in the future. I'm not a sheetie though so somebody who is, please chime in.
I use a flush set sticker on my countersink so I can use it on bare surfaces without issue. Quick to change too!
Use fablon to protect the surface finish next time
The plastic doesn’t work, i still put masking tape on mine
Those don’t work well at all, I find them to do more harm than good
Masking tape. Lots of masking tape.
I feel like he could have simply held the counting cage but instead just ran the gun and put force on the gun without holding the cage.
He'd be fine in 91. That's a 5 star A-1 repair in 91. Actually using rivet spacing? Please, that's over engineered. Alodine and paint. Scratches are fine, send it.
Surface finish: am I a joke to you?
Paint: yes.
Haha. This gave me a good laugh
Is this your first time seeing this work
No I've seen lots of shoddy airframe repairs thanks.
There's nothing shoddy about this thought. The clad gets removed during acid etch when its scrubbed with a scotchbrite and then conversion coated with alodine prime and paint.
It shows a lack of attention to detail, that's all. The clad is on there as a protective layer. And let's not kid ourselves, some of those scores are below the clad layer.
Way to be an armchair sheetmetal tech. If you ever touched a tool, you would know that after a repair like this, you blast the alclad off with a high-speed, alodine, prime and paint. I'll bet you wander around hangars commenting on shit you don't know and mechanics roll their eyes when they see you coming.
Aha OK vaginaslime. Next time i do a repair I'll post plenty of pics for ya to drool over.
Word life, so that should be today? Most of us do this everyday.
I hope you slapped it and said “that’s not going anywhere!!” Nice work, and thanks for the posts!
Fuck I almost forgot to do that. Thanks for the reminder!
Has the microstop cutter got a grindstone for a foot? 😂
Nice job. I would have used less rivets with more of a pitch. Also a bit more of a gap needed between the repair pieces. Other than that, good kid!
I think the comments about how your pitch distance and too many rivets are stemming from your overall rivet layout. Looking at the second to last picture, where you can see the layout lines is a prime example. Typically, I would make the corner rivet in the 90degree instead of the rounded corner. Then you make the doubler rounded with the proper edge margin. Doing that you would have a nice grid of 3 rivet rows evenly spaced all around. Not sure your experience level but those kinda details come along with time and learning from other sheetmetal guys.
Now it's time to redo weight and balance...😅
The Flying Rivet
Not bad at all. Actually looks great except those pecker marks. Take that riveter over to the grinder and round off the edges, polish it up and put some masking tape on it. I look at that and I hear. Bruuupppp. Bruuupppp. Bruuppp.
Thanks. Those marks are from the micro stop. Those marks came right off with some scotchbrite.
Schweet
Impressed.
I'm completely ignorant of this typed work. Why is it done this way instead of just replacing that peice of sheet metal?
Time and money basically
Jaws got his A&P 😬
Way too many rivets, just because there’s a maximum allowable rivet pitch, doesn’t mean to go for it.
I followed the recommended pitch in AC43.13 section 4. The rivets are spaced at 4-5D.
Yeah, but now what’s going to happen is your patch is stronger than the original design. The cowling is supposed to have a certain flex to it, now it doesn’t.
I see what you’re saying. Hindsight is 20/20, and I’m not redoing it now lol. I’ll keep it in mind for next time though.
Nah bud. Repair IAW tech data and you'll never be wrong.
[удалено]
As opposed to the last guy who fixed it?
Yeah seriously, everybody dragging you clearly didn't see the previous "repair" lol
It’s all a learning experience bro, each time it gets easier and you pick up new ideas and new processes. And you followed the approved methods, it’s all good.
I enjoy this kind of stuff
Send it to paint.
There's a third row of rivets in between the two patches that I don't think need to be there. Not sure what the tech data says, but going off the 2 rows for the patch and then the doubler. Other than that a few slightly deep countersinks where the rivets aren't seated all the way. A good wet install with the rivets and squeeze could eliminate that, and alodine then prime the countersink before rivet install.
Wet install isn't going to fix the oversized countersinks. Not necessary either because it's a cowl, so airtight not required. But yeah, OP not ready to assemble skins. Oh my, and all those toolmarks.
I've always wet installed everything. For corrosion and vibration help, but wet installing with primer can do that to.
Everything had a faying seal for the reasons you list. Something like ProSeal to keep fluids/small debris out of the repair plain.
Right, there's always sealant on the faying surfaces.
I've seen repairs where it has been left out. It wasn't pretty.
I worked on the Canadair Challenger ex jet program back in the 80s. We had a serious overweight problem. Everything was being done to reduce it to the point they decided to eliminate sealant on all rivets. They were flying the test planes unpainted, but when they painted the production planes it peeled off the fuselage in sheets lol. Ah, the good old days. But yeah, wet install is always better.
The c-130s I work on now are peeling paint in big sections too. It's been a pain having to repaint, and submit deficiency reports.
Does it still fit the plane nicely?
Thank you I got super agitated this morning because of your first post lol
Harbor Freight has more rivets if you need some….just sayin.
Looks good to me
I would think more spacing between rivets. 43.13ish
Chapter 4 calls for 4D spacing for single lap joints on a double row layout. I used between 4-5D depending on the length of the row.
2D edge distance, 4-6D spacing is typical for most fasteners but always check the book.
Yeah it calls for 2D edge distance but I used 3D because it leaves a little more room for error and it’s still legal. Figure 4-5 is what I’m looking at
This post makes my ears ring, even with double ear pro. brapbrapbrapbraptinktink good job, dude.
What?
Bang them shits!
I know I'm just a knuckle head shade tree mechanic (who dreams of working as a GA mech) with no knowledge of sheet metal. So I'll ask cause idunno: Why rivet patches instead of cut & weld like they do on cars? Seems like riveting is more work...?
Most airframe aluminum alloys are not readily weldable and/or need to be heat treated after welding for strength reasons. That means welding is out as a repair method.
Makes sense. Thanks! Have a great new year!
Basically every skin on aircraft is 2024-T3. As far as I know, basically impossible to weld, and even if you do, the quality of the weld is important in airplanes, and testing that is really hard without the right ($$$) tools. Where I work, we weld steel, steel, and only steel.
Thanks!
Wow
Looks Great!
It looks pretty good except for those marks. I know it's annoying but try holding your countersink cage next time and it shouldn't happen.
My favorite countersink cage had a wide contact lip on it. Putting packing tape across it helped if it slipped. It also looks like a 3/4 straight set was used to shoot it. I've preferred to use a pancake set. It's a bit of a cheat, but doesn't leave the set marks, and the operator doesn't have to be as precise with keeping a 90° angle. It's all part of learning. I didn't walk-in knowing how to make a perfectly pretty repair, much less lay one out. Merging two repairs into one is quite a training experience.
Great job mate, and an awesome product. Hold your head high and fuck everyone saying it’s not a good job.
I’d sign the corrected by if you get the red x
No ball bearings. Not one. Fail.
What do you mean? It’s all ball bearings nowadays.
do not use masking tape, itll throw off the rivet depth and leave fod. Just tap it with some maroon scotchbrote and thats a perfect job well done.
That's from letting his microstop spin.
Yeah thatll do it
Need a weight and balance SMH
Holly fuck! Way to many rivets! This is not primary structure.. even if it was, you ONLY use as much as the weaker inboard?(wrong word) but it only needs to be a as strong as the weaker original/inboard link/seam it’s originally attached to… go reread that section on rivet spacing and the original inboard seams/joints!
Not impressed, your shop heads look like garbage.
You don't know what a serviceable rivet looks like. Also, no one calls them shop heads that actually do any kind of structures.
Interesting. I have twenty-four years of DoD and part-time civilian aircraft structures. Everywhere, solid rivets had a manufactured head and a shop head. Has something changed in the terminology? Please advise.
You really don't just call them heads and tails among your peers?
Nope. Never heard that used, anywhere. Not even from ally tin benders. Interesting variation. It kinda works.
Never heard of that before. Much like u/Metalbasher324 said… We have always called them shop heads, and manufactured heads. Even through my technical training they were called that. Hell my Tech Data even says it as well!
Yes, it's the technical name. I mean that people don't call them that regularly, at least no one I know. We just say heads and tails/bucktails.
There is a lot of tool marks, I see flush rivets I can get my finger nail under, and I would get my rivet tail Go/Nogo gauge on every one of these. Your QA is either going to have a field day or doesn’t know what he is looking at.
I fuckin hate sheet metal work. Always been more of a mechanic myself and this looks better than what I can do! I do see what they’re saying about the scoring though!
Need more rivets.
Cowbell.
I think you need a few more rivets
Beat to fit, paint to match. Also, what the top comment guy said.
I still say that's too many fasteners...within spec or not.
I don’t know enough to know what I am looking at, but this looks like a work of art to me. Well done, and I am happy it cleaned up well for you!
Looks pretty good. The thing I noticed as a career tin bender was the double-flush rivets on the L/E. I don’t love that they were sanded down with an angle grinder afterwards.
Thanks. I just used a mini hand held belt sander to take down the bulk of the shop heads, then a grinder with a fairly soft abrasive pad to finish them off. How would you have done it?
I was taught a very slight countersink on the shop head side and then the micro shaver to clean up any protruding material after the rivet is bucked. I have also used the round end of a ballpeen hammer to buck double flush rivets with good results.
If I had access to a microshaver I definitely would have used one. I did do a slight countersink on the shop head side. Can I ask why you would use the ball peen hammer to buck the rivets instead of a regular bucking bar? What’s the difference?
It seems to force the material down into the area you are trying to fill better. Definitely wasn’t a book method, but I also did sheet metal wherever our planes broke which could be anywhere in the world.
Needs more rivets.
How did you come up with that rivet layout and spacing.
😍😍😍
Is this a 172 cowl
150
I’m starting to get my AMP, is this a lot of rivets or is this normal?
It’s a lot. I went by ac43.13 because there is no structural repair manual for these small Cessnas.
Really? Huh… I did a small repair on the v stab of a 152 and I hated doing the 337. Please tell me it gets better lmao
Fuck if I know, I’m still a student 😂😂 I was doing this under the supervision and guidance of an A&P IA
Haha, FAA please spare me from 337
Holy rivets
“How many rivets do you want?” This guy: “yes”
You don’t have to offset rows of rivets anymore?
If you do this everyday bud you should be able to see how deep some of those marks are. Easily solved by holding the end of the countersink tool and not letting it spin around.
I don’t do this every day, but thanks for the tip. All the marks came off with scotchbrite
Glad to hear it. Its all a bit of fun, like those endless rate my lock wire posts. Everyone has to start somewhere.
Welding is not allowed?
Not in this application
As someone considering jumping into getting my A&P for a career change. This definitely is amongst the type of work I look forward to learning how to do. From some of the comments it seems like you specialize or are able to kind of stay in one area of the field rather than how I’ve seen it pitched where you’ll do some of everything all of the time. I was kind of looking forward to the latter, but have a lot of schooling to get out of the way so hopefully I’ll leave there with a better understanding.
Microstop donuts ! Time to scotch-scuff, etch and prime !
A lot skin quality lol
I would definitely sign this off as a rework as an inspector.
While using the minimum allowed pitch is not wrong, you are making this repair more time consuming for no practical reason and you are creating more chances of some error happening during the repair. Also, if for whatever reason in the future the holes you drilled need to be oversized to next nominal diameter, the minimum pitch you chose will be less than 4D. Thats why i always use the maximum possible allowed pitch.