Thanks: 
Likes: No skill, just hours of YouTube University study and a phone consultation with Ted Waltman.
No skill, just hours of YouTube University study and a phone consultation with Ted Waltman.
Finished the cargo area floor. The hole is an access panel for elevator cable pulleys. It now has a CF cover plate. On the list for interior CF is the under seat storage bin, fuel selector cover plate, cargo and cockpit door sill cover, pulley covers and maybe the instrument panel. Rear seat back and bottom and the front seat bottom is already CF.
That is astounding. I'm over here marking out plywood.Originally Posted by Mr. Ed
Finished the cargo area floor. The hole is an access panel for elevator cable pulleys. It now has a CF cover plate. On the list for interior CF is the under seat storage bin, fuel selector cover plate, cargo and cockpit door sill cover, pulley covers and maybe the instrument panel. Rear seat back and bottom and the front seat bottom is already CF.
I've done quite a bit of fiberglass/composite work on boats, but carbon fiber just seemed one step too far. Maybe I'll rethink that.
Still working on the carbon fiber floor. I made carbon fiber 3/4”x3/4” angle, 13’ of it, cut it into smaller pieces and bonded those to the floor sections using West Systems Six-10 epoxy. The sidewall panels were trimmed to final fit and screw holes were match drilled to the carbon fiber angles. I used Click Bond floating 8-32 nut plates bonded to the angles. You can see those being bonded in one of the photos (pink rubber clamping piece sticking out).
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I tried my first three dimensional carbon fiber piece. It snaps over the cargo door sill and covers the rudder cable and a pulley below the door. Fabric will wrap over the sill so I put 8 layers of masking tape down to simulate the thickness of the fabric. The CF is five layers which results in 1/16” total thickness and quite stiff. There’s a CF angle bonded to the floor that will have a couple Click Bond nut plates in it to secure the sill cover to.
Pulled the under seat storage box off the mold today. Didn’t turn out great but it’s acceptable. I used 2” pink foam board to make the mold. Under vacuum the ends of the foam board compressed a little so the left and right sides are a little wavy. Four layers of CF resulted in the box weighing 1.678 pounds.
panel layout......just stickers at this point but components are being ordered. Dynon 10” HDX, radio & intercom, AV-30, Avidyne 410 GPS navigator. Switches will be located on the angled section on the bottom of the panel. CB’s are electronic through Advanced Panel’s ACM.
made a carbon fiber flange that bonds to the floor around the aft control stick. Snaps are pop riveted to the lip, a leather boot was stitched to fit and snaps into place. Hopefully it will keep everything you drop from making it into the belly.
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New toys came via UPS. So I built a new instrument panel out of carbon fiber and fiberglass. The bottom of the panel that angles out at 45* was too narrow for the switch panels on the aluminum one I built. Where things will fit isn’t optimal but tubing behind the panel drives location. Center screen is a Dynon HDX 10”. Left of the HDX from top down are radio, intercom and autopilot. Right of the HDX is an Avidyne GPS navigator and AV-30E. The hole cover is where the amphibious gear switch goes. Ignition switch upper right. Still have a few small holes to cut/drill. No CB’s because I’m using Advanced Panels ACM.
Most of the summer did not include working on the cub although I did work on some small parts. I spent three weeks up in AK working on the cabin we are building. Off grid, on an island, access only by boat, grueling work. Fished a couple days and pulled some nice shrimp close to the island.
Back to the project now. Running wires, crimping pins, drilling mounting holes, bonding nut plates & trying to wedge 5 gallons of stuff into a two gallon space.
sweet build! did you decide to go with the traditional floor mounted flap, or overhead flaps? After flying both, I think the overhead flap is a very important mod that I would want. It's WAY more functional than reaching down on the floor. I don't quite follow the objections about it being something you would bang your head on in a crash - everything in the cub is 4130 steel and will take your head off in a crash. That overhead flap handle will keep your head up so your eyes can see out. Only way to go in my book if you have the option.
Jay at Javron will build fuselages with the overhead flap - I'm sure you can get parts from him for the flap handle. Since you ordered your wings from him - ask him about it.
Got all the big stuff mounted today. Still a couple small things to go. Screwing around with small stuff like nut plates and making things fit right is a huge time suck. 30 nut plates plus tweaking and trimming ate 6.5 hours today.
Yes, I have the overhead flap handle. I bought the handle that Jay (Javron) makes.
Photo on top is the new carbon fiber throttle tunnel. On the bottom is the aluminum one I built previously. I thought it would look better and match the carbon fiber instrument panel. Not much weight savings. Old tunnel was 13.9 oz. New one is 12.6 oz. The bumped out sections are to accommodate the headset jacks and a double USB charging port at each location.
Fuselage is all wired. I used Deutsch connectors at the wing roots for wiring that powers all wing stuff. I should be mating the wings to the fuselage late December/early January so I can build flap and aileron cables, check routing/clearance.
Last edited by Mr. Ed; 12-10-2021 at 08:34 PM. Reason: Photo position
I would lower the hight of the front interior panels and minimize the overlap with the 2nd panel on both sides. They look good but once you get the dash and everything in they can be a major pain to remove!! Almost a sure thing that left side on will have to come out early because you have a fuel line fitting behind it that will leak Also that big aluminum flat panel behind the dash can make it a pain getting to stuff. I take it you built dash with boot cowl off. Make sure you can reach stuff with it on, primer and primer lines for example. Take note of fuel line behind throttle cover not uncommon to have one of the attaching screw try to find the fuel line. Excellent work just some stuff to extend your build time. DENNY
Thanks Denny. I’m into it at 2200+ hours now. It’s become more of a lifestyle than a project.
The forward kick panels remove with three screws and some minor flexing. The left one also requires the fuel selector handle to be removed. The boot cowl is in three parts, allowing access to the fuel lines and electric pump from both sides. It also allows some access to avionics. If I grow an additional elbow I should be able to access the remainder by removing the 10” Dynon screen from the panel. I’ve tried to consider maintenance access but am certain once covered I’ll find plenty only accessible through black magic.
That comment is a keeper, and a fair warning to anyone who's considering taking on their first big project.
Cessna Skywagon-- accept no substitute!
Question about mixing fittings:
I need to weld or braze a fitting to the fuselage for a fuel drain. The drain is brass and the “T” above is aluminum. I was thinking about putting a 304 stainless coupling between those two fittings and welding that to the airframe. I could also braze it. The reason to weld it in is to allow removal/replacement of the drain valve without pulling floor boards to put a wrench on the coupling. I’m a bit concerned about corrosion between the aluminum T and stainless coupling. Is this something to be concerned about? Should I use a brass fitting and braze it in?
Thanks.
Brazing isn’t a good idea if it is on 4130. May look good on the outside, but likely all cracked on the inside. Not sure if it is the filler metal or the heat, but I’ve seen lots of 4130 that was brazed and you flip it over and it is nothing but cracks!
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43.13 sez don't braze to structure. Waiting for a good day to come down with Steve F. for a progress check.
Gordon
N4328M KTDO
This is what I found on it in 43.13BNOTE: Never weld over a previously brazed joint.a. Brazing requires less heat than welding and can be used to join metals that are dam* aged by high heat. However, because the strength of brazed joints is not as great as welded joints, brazing is not used for structural repairs on aircraft. In deciding whether braz* ing of a joint is justified, it should be remem* bered that a metal, which will be subjected to a sustained high temperature in use, should not be brazed.
The way I read it is don't brazing for structural parts. Is a tab for a fuel drain considered structural?
DENNY
My opinion would be 'yes', if it's brazed to something structural. In the past I've been advised that it's ok to braze 1020 stuff like the bird cage, but not longerons, etc.Is a tab for a fuel drain considered structural?
edit: I'm not positive, but it seems like there is some sort of metallurgical problem, aside from the lower strength issue. Maybe a galvanic issue? Somebody here probably knows.
Last edited by Gordon Misch; 01-15-2022 at 10:10 PM.
Gordon
N4328M KTDO
Without looking it up, from A&P school memory the rule was not to braze on primary structure. Meaning if it failed it could cause serious failure of the structure. But it was alright to braze secondary structure such as the so called "birdcage" fairing stringers. The reason being that it is not possible to determine the strength of the brazed joint by visual inspection since it flows like solder looking nice but may not have completely attached to the base materiel. Brazing can be very strong or very weak while visually both joints appear the same. Since the inspection process is not definitive, brazing is just not used. Though I think some have used it on "birdcage" type structures.
N1PA
I couldn't find that reference. Can you give the para number please? I'm curious because I would have thought there would be a distinction between brazing primary structure and brazing a non-structural component to primary structure.
4-88. a. Page 4-59
a. Brazing requires less heat than welding and can be used to join metals that are damaged by high heat. However, because the strength of brazed joints is not as great as welded joints, brazing is not used for structural repairs on aircraft. In deciding whether brazing of a joint is justified, it should be remembered that a metal, which will be subjected to a sustained high temperature in use, should not be brazed.
N1PA
Under what circumstances would adding a non structural support tab be considered to be a structural repair? I don't see that the quoted para is equivalent to "43.13 sez don't braze to structure."
Clarification: The tab is already welded to the structure. I would be welding or brazing the coupling to the tab. Nothing structural about the tab.
What I was most concerned with is the dissimilar metals; aluminum T, stainless coupling, brass fuel drain. Corrosion potential? Or does the fuel lube provide a barrier? Or not a concern.
I will suggest getting a piece of 4130 sheet and braze something to it. Look at the back side to see if you have any cracks. If they are there, they will be ugly and very visible. If you don’t get cracks, then go ahead and braze it.
If you do weld it, I would suggest using some 309 rod if you are welding 304 to 4130. Purge the fitting with argon in the inside as well as using argon as your shielding gas. Stainless will get sugary deposits if you don’t purge when TIG welding.
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My only experience with brazing anything on an aircraft was the repair of the air box of an Aeronca 11-BC Chief. The spindle and the bearing doublers were totally shot. I unbrazed the flap valve and actuating lever from the spindle, fabricated new bearing doublers from 4130 sheet, brazed the flap valve onto a new piece of 4130 tube and put it all back together.
If brazing was good enough for Aeronca then it was good enough for me and my IA signed it off. No sign of cracking anywhere. The flap was steel and I assume 4130 but I can't be sure of that.
Brazing mild steel is never an issue. I’ve only seen the cracking with brazing 4130. Could be an issue with the type brazing rod, don’t know.
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Remember that you can braze using TIG at a lower amperage with silicon bronze filler rod. You don't need to bust out the torch and heat the whole area up. TIG has much more accurate heat and could prevent the cracking that others have seen with traditional brazing.
I looked at a Dakota cub fuselage a couple years ago. They had tig brazed the cargo door frames and D window channels to the fuselage. I tig brazed the window channel to the window frame for my left shooters window. I tried it out on some scrap sections of the same pieces and then beat on it with a dead blow hammer. The square tube turned into a trapezoid from the beating but the brazed joint held fast.
dgapilot…Thanks for the heads up about purging the stainless.
Early J3s have the 3/8" channels brazed for the turtle deck brazed on. Real pain in the butt to repair if welding because you have to get all that bronze off the tubing.
But all of that was brazed to 1020 tubing, not 4130.
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Why would the lesser heat of brazing damage 4130 but the higher heat of welding not affect it negatively?
I don't have an answer to that, just seen a lot of 4130 that someone tried to braze and it looked great on the front. Turn it over and it was really ugly! As I stated before, jet a piece of 4130 and braze something to it, then turn it over. If it looks OK, go ahead and braze your tabs. If it looks ugly, weld them on. All that said, welding rod is a lot less expensive than brazing rod.
Would it be possible to just get a steel bulkhead T fitting to attach the drain to and weld that to your tab? I'm thinking something like this:https://www.airframesalaska.com/Fuse...gs-p/fm-bf.htm
And if you went with a bulkhead fitting, why even weld it, just have the tab big enough that you can drill for the bulkhead fitting to go into and screw the nut on to hold in place, after all, that's what bulkhead fittings are for.
There we have it! Simple is good!
Web
Life's tough . . . wear a cup.
A bulkhead fitting was the original intent and I am set up like the Airframes link for my brake lines. However, I haven’t found a bulkhead fitting that works with drain valves. One of the cub clone kit manufacturers (their kit has two drain valves in the belly) specifies a T for the valve. I bought the specified T, which isn’t a bulkhead fitting, but it didn’t work for me. The concern I have is if it isn’t a bulkhead fitting or a welded in fitting then there is potential for the drain valve (brass) to wear against the edge of the hole it protrudes through (4130 sheet like the Airframes brake fitting mounting pad) due to vibration. Maybe I’m overthinking this and it isn’t an issue. But if it is…bad stuff happens and I’m trying to avoid bad stuff.
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