PA-12 restoration started

[Sturgill]

So I bought a Cruiser project a few years ago. I’m helping my youngest son work towards his A&P while he is living at home and going to college. We decided to get started on the fuselage. The last annual was in 1965. About 1300 hours ttaf by the logbooks. It had been owned by a DAL mechanic in Atlanta for years, and was in his basement when he died. He had recovered and painted it many years prior. No engine, but everything else is there.

We had a stock Cruiser for a few years and it was a great airplane. With this I just want to make it a little more comfortable and sporty. Univair 150hp STC, x-brace, cathedral ceiling. I ordered new PA-14 gear legs, new balanced tail surfaces, and the skylight, x-brace, and cathedral STCs. Will also weld in shoulder harness mounts.

We have started stripping it down and it looks pretty good. Its got that darn red oxide primer on everything. 1st question: are these brackets at the lower front corners stock, or were they added for skis?


Next question: Does the little “fence” behind the baggage compartment get removed when you put the cathedral ceiling in? It looks like it needs to go so that a new upper baggage floor can be installed.
That’s all for now!

[DENNY]

I would strongly recommend the gross weight upgrade while you have the fuselage exposed. DENNY

[n180tf]

Who offers that upgrade?

[AZinAK]

I'd do a 150 or 160 hp engine on a short mount, flaps, -18 tail feathers, max gross upgrade, -18 landing gear and the Sensenich ground adjustable prop. Upgrading the fuel system using Dakota Cubs kit would be a hard one to pass up during a rebuild as well.

[Sturgill]

I don’t want or need flaps or pa-18 gear. I will put the DC fuel system in and remove the header tank. I forgot to mention that I also got the Crosswinds skylight STC as well.

[Utah 12 Driver]

I would say you may want to rethink the flaps, they are a major change that adds value to the project not to mention performance. The PA-18 gear well that's up to you but at least put the mounting ears just in case you change your mind later. PA-12 are awesome machines but at some point you will want to sell your plane (I know you think you never will but things change....) Flaps, extended baggage, Gross weight increase are all the things that most people will be looking for in a PA-12. For the most part PA-12 don't bring the same rate of return verses a PA-18. So aim to get the best bang for your buck, even though you aren't thinking resale at all. These aircraft have increased in value so much in the last 10 years it's difficult to believe, even for those of us who have witness it. The future is unknown, but protect your investment and the hard work it takes to bring these marvelous airplanes back to life.

I wish you the best and please forgive the wandering of an old man

[DENNY]

You may also want to sandblast the fuselage, inspect and repaint. Primer paint need a topcoat to prevent rust.
DENNY

[TurboBeaver]

If you have ANY intentions of ever flying skis, or flying off airports with big tires, for gosh sakes don't forget to "box the tail" (or X brace) it won't stand much side loading without that mod. The left side needs a vertical tube welded in for float operations, from top longeron to bottom directly below one that's there under front wing attach fitting. That's the weak link on a 12. These two simple mods weigh nothing, but add tremendous strength to the airframe. Give special attention to the tubing around the gear fittings with a prick punch; now is the time to fix it! 76 year old tubing gets punky........ The removable crossbar mod, is very handy with extended baggage, makes loading so much easier. It does use the "fence" you are referring to removing? Mine has the cathedral brace and the fence........... But lots of 12 don't so there must be a work around? ( Charley)
Good Luck. They are a wonderful airplane.
E.
Here is a non flapped Cruiser landing in 75 degrees with no wind, on standard 12 gear. The Jeep is parked 250 feet from end of the runway. This plane could easily land and take off from that space all day long. 150 HP with Borer prop, weighed 1070 empty.

https://youtu.be/05_-TkCSbFE

[Trimcable]

To your first question, the brackets are for attaching the lower cowl rail angles to.


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[Sturgill]

Thanks!

To your first question, the brackets are for attaching the lower cowl rail angles to.


Sent from my iPhone using SuperCub.Org

[dirthog4]

For structure above baggage headliner was glued to top channel and aluminum trim band below. Removal depends on baggage configuration and type of headliner used.

[Gordon Misch]

My thoughts, as an owner of a single PA-12 for nearly 50 years. I bought it stock, and it was good that way. Since then I've done all the usual off-airport "stuff" and a more capable panel. For back-country and off-airport flying all those mods are very good. For the grass strip scene I'd think keep it stock, or maybe add bigger engine, flaps, and extended baggage. I REALLY like the Crosswinds "cargo door". And so do pax. Gross weight upgrade is one thing I didn't do, and wish I had.

[Sturgill]

We got started on the fuselage work. Removed the old diagonal brace and fabricated and tacked in the new cathedral framework per the STC. It does open it up a lot. I haven't yet received the STC for the overhead x-brace. Once we put those tubes in I will flip the fuselage and finish weld it all. Also the front and rear mounts for the skylight, as well as the shoulder harness mounts.

Also removed the old "fence" just above the original baggage compartment. I removed the battery box/tray assembly, as well as the long cables. We will go with a firewall mounted battery eventually.

Questions for the day: 1) Who sells the mount for the Dakota Cub fuel valve? I emailed DC, but haven't heard back yet. 2) With the DC fuel system approval, will I still have the vent crosstube going across the face of the front carry-through? Can I remove the little original mounting tabs?

Going to work for a week. Gotta pay for all this stuff. All done for now.

[Steve Pierce]

I would look at the door frames IAW this Piper Service Bulletin. https://resources.univair.com/docs/s...tube-corrosion Found lots of bad tubing complying with it.

[KJC]

It’s sounds like a really great project and your definitely on the right website. There are a lot of people here willing to offer good advise and tips. I’ve rebuild a -12 from the ground up and owned a -14 and -18. I’m no expert but please consider the everything that was mentioned above. It’s all sold logic from years of experience. Before anymore welding, there are a few things you need to inspect.

Door channels- glad Steve mentioned it. Underneath the entry door channels, the tubs get pretty rotten. I suggest you remove them and check. Univair sells new to replace them after removal.

D-windows- check the bottom of each window for corrosion. Water sits in there and they are likely shot. Take a good look.

Lower Longerons and tail area- check the bottoms of the tubes near the tail for corrosion and pitting especially on the bottom sides. Also, take a really good look to make sure the tail area isn’t twisted. As was mentioned above you need a brace back there during rebuild. Don’t worry, it’s easy to weld in. You get it from Atlee or make your own. X brace or H shaped you choose. It’s a minor modification, no STC.

Once you’ve done inspecting, please consider the following mods and STCs. I know you think you won’t use or won’t need many of these but they will be a 10-1 return on investment going forward. I think your on the right track with some of these already.

Overhead x brace (think safety in a crash on this one)

Cathedral Brace ( you’re already on it-good job)

Reverse Dogleg- it opens up the lower baggage

Vertical Tube from the left gear attach fitting up to the left wing spar fitting. This is a big one and you need to do this while it’s apart. The left forward gear fitting is a very weak point and this should be addressed. I can’t stress this one enough.

1950# Up gross weight STC. 200# is a huge increase. It’s a lot of fitting tubes and time consuming but not really very difficult.

Extended baggage- PA-12 are already roomy but this really makes it a hauler combined with the gross weight increase.

Tailbrace- X or H style you choose

PA-18 Gear tabs- the almost 80 year old gear you have there is junk. Yes, throw it right in the scrap pile. Too high a chance of internal corrosion. A beautiful restoration ruined buy a gear collapse. No way. -18 gear is stronger and give you a lot of options for shocks be it Hydrosorbs, AOSS, etc. My suggestion would be 3” extended Airframes gear with entry steps, mid steps and fueling step on the left. Have them do the powder coat. Atlee used to have the weld on tabs premade. You save some weight by removing the bungee truss under the front seat

Front seat- use an -18 sliding/fold down front seat

Flaps- you have a a couple of lugs to weld on for this. I know you said you don’t want them (but I think you really do). Biggest dollar wise return on investment in a -12.

Seatbelt tabs welded to the floor (think safety here). Atlee has the tabs.

Float Fittings- call Atlee

Lower battery door- remove this small useless door and put it up higher for an upper baggage door. Your moving the battery anyway under the front or rear seat, not the firewall. -12s are nose heavy with only one person so let’s keep a little weight aft.

Tabs for an Airglass cargo or fuel pod even if you never need them.

Removable Rear Seat Crossbar

Im sure there is more but this will give you something to research. Most of the above have associated STCs. Reach out with more questions and people here will be glad to help.

[MT12]

the dakota web site has a mounting diagram for the fuel valve assembly, no separate paper work needed. I left my cross vent line in, I don't know if I needed to but with the DC valve shut off you don't get any cross feeding even with the vent line.
don't forget to weld a tab on thee cathedral 'X'for a rear seat shoulder harness.

I agree on firewall mounted battery, I mounted an odyssey bat under rear sear with a field approval.

I agree with advise from KJC, except gross weight increase only gets you to 1935#, and the addional tube make a lower baggage door so tiny it's hardly worth it.

I suggest building a platform right in front of the jack screw for your 406 ELT.

for pics of my baggage door and elt set up check out:

https://www.supercub.org/forum/showt...-Phoenix-story

[Sturgill]

Thanks for the link to your previous thread. Very nice. Did you have a STC for the swing-up door?

[MT12]

I don't remember if it was done via stc or field approval, it was in the log books from long ago and so univair was willing to add it to the new fuselage without further documentation

[MT12]

oh yea don't forget to turn your trim system into the pa-18 double pulley system. all the parts are PMA'd from Dakota Cub, and all it takes is welding on 2 tabs fir the idler pulleys. there's no paperwork available but it is done in accordance to piper pa18 drawings. an absolute must mod.

[Sturgill]

Ok. I talked with Charley Center today and we decided that the seaplane door isn’t a good idea for what I want to do. I will get the DC trim parts.

[Flyin S]

As a -12 owner/builder for 40 years, I endorse everything already suggested and included almost all of them while restoring mine (twice). My biggest regret is not completing the gross wt mod (I boxed the tail and nearly everything required except replacing the upper formers with tubing). Several folks talked about the lower extended baggage mod but did not mention that it requires switching to the PA-18 style elevator control system, which
gets rid of the -12 torque tube below the original gym-bag-size storage compartment. This is a great mod, easy to do, and opens up the entire bottom fuselage. The biggest advantage of -18 gear is if you intend to operate on floats part of the year---makes bungee removal a piece of cake. Otherwise, -12 gear is more than adequate and you can now buy heavy duty/extended -12 gear if you want to "run with the big boys". I have 3" -18 gear on mine with 31" bushwheels---that's the ticket for me! Depends on your mission and pocketbook!

[skywagon8a]

As was mentioned above you need a brace back there during rebuild. Don’t worry, it’s easy to weld in. You get it from Atlee or make your own. X brace or H shaped you choose. It’s a minor modification, no STC.

Ask yourself if welding on an aircraft can be done without any special training? Welding on an airframe is considered major whether it is a repair or an alteration. So a 337 would be required and the alteration does need some type of FAA approval.

https://www.law.cornell.edu/cfr/text/14/1.1
Major alteration means an alteration not listed in the aircraft, aircraft engine, or propeller specifications -
(1) That might appreciably affect weight, balance, structural strength, performance, powerplant operation, flight characteristics, or other qualities affecting airworthiness; or
(2) That is not done according to accepted practices or cannot be done by elementary operations

https://arsa.org/regulatory/faa/maintenance/majorminor/
"What is elementary for one mechanic or repair station may not be elementary for another. To determine whether the operation is elementary, make sure it is in writing and repeatable, and whether it requires special education or training to accomplish in a standard (repeatable) manner. Even if it is in writing and repeatable, the action could be considered major if the technician performing the required methods, techniques and practices needs special training."

[KJC]

I don’t want to get this thread off on a tangent but I just went through this welding question with a PMI when asking for a field approval. We went through the flow chart in in AC 43-210a. In the end he said I didn’t need a field approval. According to him the old thought of welding and riveting constituting major v minor is incorrect.

Again, a lot of people smarter than me.

[dgapilot]

Ask yourself the following questions: If welding is "Elementary", why is half of Chapter 4 in AC43.13-1B all about welding? Can anyone off the street weld proficiently without extensive training and practice? Why was welding removed from the Part 147 curriculum about the same time that the AWS D17 (Aerospace Welding) standard was approved? Why does a 145 Repair Station that has Welding on it's Capability List have to have employees certified to AWS D17 for the type of welding performed at the repair station? Hate to say it, but your PMI is dead wrong on this one. Going through the flow chart in AC43-210A how do you answer the question Could the repair or alteration have an appreciable impact on Structural Strength? If a weld is improperly done (easy to do) it will most certainly have an impact on structural strength!

The section in AC43.13-1B Change 1 has a paragraph about welding certification. While not required, if it was an elementary operation why would it need a special certification?

The issue of Field Approval or not is independent of Major Repair or Major Alteration and data required. You can do lots of welding with the Approved data in AC43.13-1B and not need a field approval, but it still requires a 337. The next issue would be for alterations where you are adding structure and does that need a Field Approval? Adding structure will impact Structural strength, but typically for the better. On the other hand, where will it transfer stresses to? That gets into the "other factors affecting airworthiness. If it isn't on the Piper drawing, and you are adding it, it is likely a Major Alteration (possibly a Major Change in Type Design) and that requires approved DATA. A Field Approval is but one way to get Approved Data. You would not be looking for the approved data for the welding (you already have the approved data for the process), but rather for the altered structure.

Rant over
David Schober
A&P, IA, DART, DARF, DER

[dirthog4]

If you don't need a certified aircraft certificate experimental looks better every day.

[buckeye]

All good ideas, may I suggest keeping electrical stuff out of the wing roots.

[Steve Pierce]

I add the "X" in the tail and list it on my 337 with all the other welding I did on the fuselage per AC 43.13 as repairs and per the STC's.

[wireweinie]

I don’t want to get this thread off on a tangent but I just went through this welding question with a PMI when asking for a field approval. We went through the flow chart in in AC 43-210a. In the end he said I didn’t need a field approval. According to him the old thought of welding and riveting constituting major v minor is incorrect.

Again, a lot of people smarter than me.

Guys like dga can take you much deeper on subjects such as this but it doesn't need the depth here. Read FAR43, appendix A for the descriptions of major repairs and major alterations.

(a) Major alterations -
(1) Airframe major alterations. Alterations of the following parts and alterations of the following types, when not listed in the aircraft specifications issued by the FAA, are airframe major alterations:
(i) Wings.
(ii) Tail surfaces.
(iii) Fuselage.
(iv) Engine mounts.
(v) Control system.
(vi) Landing gear.
(vii) Hull or floats.
(viii) Elements of an airframe including spars, ribs, fittings, shock absorbers, bracing, cowling, fairings, and balance weights.



(b) Major repairs -
(1) Airframe major repairs. Repairs to the following parts of an airframe and repairs of the following types, involving the strengthening, reinforcing, splicing, and manufacturing of primary structural members or their replacement, when replacement is by fabrication such as riveting or welding, are airframe major repairs.

Notice that major alterations are changes to structure not listed in FAA specs. I.e., if you CHANGE structure from what 'the book' shows, that makes it a major alteration. I know, an STC may tell you to weld something in, but an STC is an official specification and you need to fill out a 337 when you install an STC anyways.

Major repairs are described as changes to structure (primary structural) components when the replacement is by riveting or welding.

So, as per FAR43 (not AC43) any time you have to weld or rivet or add to/remove from, structure it will always be either a major repair or major alteration.

Web

[Sturgill]

I add the "X" in the tail and list it on my 337 with all the other welding I did on the fuselage per AC 43.13 as repairs and per the STC's.

Does anybody have a photo or drawing for the rear x-brace?

[jrussl]

On a Super Cub


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[fishhook]

Another option instead of the x brace is to do the "U" brace that goes in the same spot and carries all the way up to the top longeron, and has another horizontal tube set further back to clear the elevator cable. Also while its apart check the horizontal attach fitting at the longeron very well, they can crack at the front side in the longeron.

[stewartb]

Both of my PA-12 airframes had a box reinforcement, similar to the Atlee clamp-in box, but welded in.

[flybynite]

The x brace won't interfere with the stringers if a stock appearance is important to you.

[KJC]

Here is the Atlee Dodge version: Either this or the X works fine.

[Sturgill]

Could someone please post the distance from the tailpost to the fuselage cross brace? Does it coincide with one of the horizontal crossmembers?

[flybynite]

The most effective location for the X brace in the tail section will be half way along the unsupported longeron and half way on the diagonal. The box in this pic should probably coincide with the cross tube in my opinion.

[TurboBeaver]

Just for reference, one time a friend had recently added 31" Bush wheels to his new to him Super Cub, he wanted
me to fly it and give him an honest idea how it compared to lots of other Cubs I had flown. So I jumped in it and ran up to hunting camp and threw in a front shoulder and hind quarter of a big Moose, then the headskin on top of the meat. Back taxied on a 600' tundra strip and swung the tail out around in the virgin tundra ( where we always turned) unbeknown to me the tail was NOT boxed in......(or X braced )
When I landed back at lodge, he rushed out to greet me and get the appraisal on how she compared. Then we both noticed the fabric was sagging badly on one side of fuselage!!!!! ONE turn in " rough stuff" can tweak your fuselage. So if you don't think this is one hell of a critical mod: better think again.
E

[Sturgill]

The most effective location for the X brace in the tail section will be half way along the unsupported longeron and half way on the diagonal. The box in this pic should probably coincide with the cross tube in my opinion.

Thanks! Just what I needed!

[fishhook]

Not shown in that pic is the longeron support from the jackscrew tower cluster area, my U brace is 16 3/4 from tailpost OC on bottom longeron, tilted back. Horizontal piece (not required in an X brace), is 13 3/8 from tailpost OC. With an x brace you dont need to worry about elevator cables hitting it as much but if you do go half way up the bay I would double check.

[flybynite]

I should have added that the tail section shown has been replaced with a Univair short section that included an X brace. I couldn't find a pic of it that illustrated the location as well as this one did.