PA12 Cruiser rebuild/upgrade project

[rv8drvr]

Quick thread start. I have had a nice 0290D2 PA12 for more than 10 years. It has been a great plane until I put it on its nose. The crank was bent and the fuselage tweaked when the left wing hit the ground. Luckily I had just installed shoulder harnesses and was doing 5 mph.

The plane was bought back from the insurance company and is now a major project.

1. Have a new Univair fuselage
2. Wings are stripped and being rebuilt with stock ribs, with one almost ready to cover.
3. Dakota tanks, old ones were patched up
4. Adding flaps, have the parts
5. Have an O320B2A to rebuild and convert to 150 HP (Univair STC)
6. Have skylight and extended baggage STCs
7. Have a Goodyear 26" STC
8. Have new PA12 gear and keeping stock
9. Will keep as light as possible

Much more to come and will figure out posting pictures.

George Meketa

 

[pa12drvr]

Nothing not to like about this, particularly #9.

No true basis of comparison, but if you're building the engine can you go to 160 hp? I went from the 0-290D2 to 160hp (bought an engine)...quite the jump.

Will you need or want the -18 tailfeathers under the Univair STC?

Probably already thinking about it, but would suggest VG's on the wings / underside of tail....gives one much more control at the low end of flight speeds

 

[daedgerton]

Love it! I have a 12 that is in parts / pieces from a ground loop last year... In process of getting fixed as well!

 

[rv8drvr]

Already had the PA18 tail feathers and short mount, which I like, on the plane so staying with the Univair STC. The STC only allows 150HP engines, but Lycon ported cylinders and Sutton exhaust should wake things up. Do not know of an avenue to allow 8.5/1 compression.

Heres a pre-Incident pic. More to come.

GM

 

[Paul Heinrich]

Installing flaps on a PA 12 wing is a lot harder than it looks.

Routing the flap cables so they don’t interfere with the aileron control cables when the flaps are retracted is the easy part. But it is near impossible to maintain clearance when the flaps are extended. I would be willing to bet that the flap/aileron cables rub when extended in the majority of 12s with 18 flaps.

I wonder how many mechanics on here have seen evidence of flap/aileron cable abrasion in the area around the flap bellcrank in 12s with PA18 flaps installed.

PA12 owners: on your next preflight extend the flaps, open the flap bellcrank access/inspection panels, and move the ailerons full range. Do the cables ever touch? Does the flap bellcrank touch the aileron cables? Now have someone cycle the flaps. Do the cables rub at any point in the cycle? It would be interesting and helpful to know.

 

[Philly5G]

Already had the PA18 tail feathers and short mount, which I like, on the plane so staying with the Univair STC. The STC only allows 150HP engines, but Lycon ported cylinders and Sutton exhaust should wake things up. Do not know of an avenue to allow 8.5/1 compression.

Heres a pre-Incident pic. More to come.

GM

Wow!!! I think that's the most original PA-12 I've seen pictured on supercub.org!!

 

[mike mcs repair]

Installing flaps on a PA 12 wing is a lot harder than it looks.

Routing the flap cables so they don’t interfere with the aileron control cables when the flaps are retracted is the easy part. But it is near impossible to maintain clearance when the flaps are extended. I would be willing to bet that the flap/aileron cables rub when extended in the majority of 12s with 18 flaps.

I wonder how many mechanics on here have seen evidence of flap/aileron cable abrasion in the area around the flap bellcrank in 12s with PA18 flaps installed.

PA12 owners: on your next preflight extend the flaps, open the flap bellcrank access/inspection panels, and move the ailerons full range. Do the cables ever touch? Does the flap bellcrank touch the aileron cables? Now have someone cycle the flaps. Do the cables rub at any point in the cycle? It would be interesting and helpful to know.

did you flap actuator mount get put in upside down?

I make rub fairleads that mount in the flap hangers to avoid/minimize that..... I actually put fairleads all the way out to the aileron since we now use the 7X19 cable which sags more...

 

[Paul Heinrich]

MCS: I solved the problem by purchasing new PA14 wings from Univair. The flap system is different than an 18 aftermarket STC installation. The flap control cable in a 14 is routed differently and includes a stand-off bracket. 14 flaps are bigger, too.

Fairleads might help, but the PA12 flap STC drawings and instructions say nothing about that or any other practical tips. For me it was easier to use 14 wings in part because they were designed for flaps by Piper.

 

[mike mcs repair]

MCS: I solved the problem by purchasing new PA14 wings from Univair. The flap system is different than an 18 aftermarket STC installation. The flap control cable in a 14 is routed differently and includes a stand-off bracket. 14 flaps are bigger, too.

Fairleads might help, but the PA12 flap STC drawings and instructions say nothing about that or any other practical tips. For me it was easier to use 14 wings in part because they were designed for flaps by Piper.

I do the 14 installation on -12 wings.


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[rv8drvr]

We have the flap hinges mounted and am going to wait on the bell crank and false spar install until the wings are test fitted, with aileron and flap cable routing verified. Also the Dakota tank straps around the bell crank area are being left out until all things that can not be moved around there are installed, drilled and done. Trying to do all that has no option first then go from there. Have read about the flap mechanism interference problems in the wing and trying to stay ahead of it.

Looked at a nice O-235 PA12 this weekend. Had a McCauley metal prop with a McCauley extension that was bolted to the crank then the prop bolted to it. Have not researched yet, but is that stock?? Pictures soon.

GM

 

[mike mcs repair]

-12 & -14 flap hanger need to be 5/16” shorter than-18 ones. Univair screwed up the last set I ordered. I usually shorten-18 ones by cutting off end and putting new hinge blocks in. Also the attach for false spar needs to be closer to spar by same distance. I like Dakota cub ones because that part is not welded on. I leave them off and just use the AD external ones


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[mike mcs repair]

I think I have the -14 wing blueprint at shop. Remind me tomorrow to look. I can take a picture. I also saved a -14 rear spar I use for reference of where the holes go.


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[Paul Heinrich]

Little left to wonder why Mike is at the top of everyone’s list for go-to guys. I mostly speculate when I pontificate about airplanes. Hence, I’m frequently wrong.

Mike doesn’t have to because he REALLY KNOWS CUBS and BONUS: he knows and/or designed the tips and tricks to make them even better.

Thanks Mike MCS repairs. The knowledge you share freely on this site is invaluable to us all. Live long and prosper.

 

[Philly5G]

Little left to wonder why Mike is at the top of everyone’s list for go-to guys. I mostly speculate when I pontificate about airplanes. Hence, I’m frequently wrong.

Mike doesn’t have to because he REALLY KNOWS CUBS and BONUS: he knows and/or designed the tips and tricks to make them even better.

Thanks Mike MCS repairs. The knowledge you share freely on this site is invaluable to us all. Live long and prosper.

A big +1 for this. Thank you Mike, you've really helped me and all of us

 

[Paul Heinrich]

By the way, I hope that all the other Cub specialists that have contributed to this website over the years know that they were intended to be included when I referenced and thanked MikeMCS. I hope none of them feel slighted because I named only one. Mea Culpa.

 

[PerryB]

Already had the PA18 tail feathers and short mount, which I like, on the plane so staying with the Univair STC. The STC only allows 150HP engines, but Lycon ported cylinders and Sutton exhaust should wake things up. Do not know of an avenue to allow 8.5/1 compression.

Heres a pre-Incident pic. More to come.

GM

If the compression ratio isn't specified in the STC, I think you can just dummy-redline the tach. Kinda of like what's done on the LSA Carbon Cubs.

 

[skywagon8a]

If the compression ratio isn't specified in the STC, I think you can just dummy-redline the tach. Kinda of like what's done on the LSA Carbon Cubs.

I did just that with a Field Approval to derate a 160 to 150. Paint a new red line on the tack at the 150 hp rpm. It was because of a 150 hp limitation to install floats.

The engine was originally uprated by way of the parts manual as a minor alteration by a repair station.

 

[PerryB]

When it's time to OH my 320, it's going to Lycon and coming back with 8.5:1 and probably 170-ish HP and a new redline.

 

[rv8drvr]

The Stoddard/Univair STC is Only for 150HP A and C series O320 engines. The C series engines are 160HP, B series engines with 150HP piston and rings installed and the data-tag stamped or replaced, all other parts are the same. I am building up the engine and have ordered new ported cylinders and a new crankshaft from Lycon. Sending out the crankcase, accessory case and rods this week. Lycon claims 5 extra H.P. per ported cylinder which is accurate on the IO360 in my RV8. I had to go through the engine with the only change being porting of my Lycoming Angle Valve cylinders. Fuel flow to keep EGT below 1300 on climb out increased by 10%, meaning H.P. went up 10%. I asked about the parallel valve, carbureted engines and they claim the same. Hoping for a few extra ponies from porting and Sutton Exhaust.

GM

 

[rv8drvr]

Aftermath. Did not even turn one blade.

GM

 

[Philly5G]

By the way, I hope that all the other Cub specialists that have contributed to this website over the years know that they were intended to be included when I referenced and thanked MikeMCS. I hope none of them feel slighted because I named only one. Mea Culpa.

And another VERY BIG +1 to this post too 8) these forums and the knowledgeable folks that take the time to share their knowledge are a big part of the reason I love having a Cub and am able to keep it going, THANK YOU to everyone, you know who you are, who's helped me over the last 3 years of PA-12 ownership!!!!

Every time I meet someone with a Cub here in UK, I ask if they've subscribed to supercub.org, as for me, it's an absolute essential

 

[Philly5G]

The Stoddard/Univair STC is Only for 150HP A and C series O320 engines. The C series engines are 160HP, B series engines with 150HP piston and rings installed and the data-tag stamped or replaced, all other parts are the same. I am building up the engine and have ordered new ported cylinders and a new crankshaft from Lycon. Sending out the crankcase, accessory case and rods this week. Lycon claims 5 extra H.P. per ported cylinder which is accurate on the IO360 in my RV8. I had to go through the engine with the only change being porting of my Lycoming Angle Valve cylinders. Fuel flow to keep EGT below 1300 on climb out increased by 10%, meaning H.P. went up 10%. I asked about the parallel valve, carbureted engines and they claim the same. Hoping for a few extra ponies from porting and Sutton Exhaust.

GM

I'm test flying and closely monitoring the new O235-C2C I've just fitted to my PA-12 in accordance with the Lycoming Break in Procedures. I've got the oil T&P and CHT temp target numbers from the Lycoming documentation, but I couldn't find definitive/target and RedLine EGT numbers other than under the leaning instructions:

C. LEANING TO EXHAUST GAS TEMPERATURE GAGE.(1) Above 75% power – Never lean beyond 150°F on rich side of peak EGT unless aircraft operator’smanual shows otherwise. Monitor cylinder head temperature.(2) 75% power and below – Operate at peak EGT.

but there's no reference to what "Peak" EGT is.

The closest I've got to a definitive EGT "RedLine" is in this article by Paul McBride https://generalaviationnews.com/2007/02/02/egt-whats-normal/ when he notes the max EGT temp is as for a turbo aviation engine at 1650 (F) / 889.9 (C) and this is what I've set as my EGT redline. I'm wondering where you found the 1300 (F) number that you mentioned to keep below in your climb out?

 

[skywagon8a]

.. but I couldn't find definitive/target and RedLine EGT numbers other than under the leaning instructions:

C. LEANING TO EXHAUST GAS TEMPERATURE GAGE.(1) Above 75% power – Never lean beyond 150°F on rich side of peak EGT unless aircraft operator’smanual shows otherwise. Monitor cylinder head temperature.(2) 75% power and below – Operate at peak EGT.

but there's no reference to what "Peak" EGT is.

The closest I've got to a definitive EGT "RedLine" is in this article by Paul McBride https://generalaviationnews.com/2007/02/02/egt-whats-normal/ when he notes the max EGT temp is as for a turbo aviation engine at 1650 (F) / 889.9 (C) and this is what I've set as my EGT redline. I'm wondering where you found the 1300 (F) number that you mentioned to keep below in your climb out?

Philly,
There is no such thing as an EGT limit temperature. When used on a turbocharged engine there is a TIT (turbine inlet temperature) limit. Not applicable to your engine.

People would be better off if the EGT instrument had no numbers at all on it as you only want to know what the relationship to peak (maximum) EGT may happen to be. It is solely an indication of the fuel/air mixture ratios presented to the pilot in the form of a temperature.

 

[Philly5G]

Philly,
There is no such thing as an EGT limit temperature. When used on a turbocharged engine there is a TIT (turbine inlet temperature) limit. Not applicable to your engine.

People would be better off if the EGT instrument had no numbers at all on it as you only want to know what the relationship to peak (maximum) EGT may happen to be. It is solely an indication of the fuel/air mixture ratios presented to the pilot in the form of a temperature.

Yes and that's what the bulk of the EGT stuff I found when researching this online said and Paul puts it like this "The main thing to keep in mind is that the only temperature that must not be exceeded is the one set for basically turbocharged engines. The maximum temperature for most, but not all, is 1,650° F. On a normally aspirated engine I don’t believe you can get there regardless of what you do. Anything less than that is fine and is of no concern." 8) so how do we/I find out what peak (maximum) EGT is? Is it the highest value I see on my EGT gauges? They're on #1 and #4 cylinders btw.

Is 1300 in the original post the peak EGT and if so, I'm very keen to know how it was arrived at

Thanks!

P

 

[skywagon8a]

8) so how do we/I find out what peak (maximum) EGT is? Is it the highest value I see on my EGT gauges? They're on #1 and #4 cylinders btw.

Is 1300 in the original post the peak EGT and if so, I'm very keen to know how it was arrived at

Thanks!

P

Slowly lean the mixture while monitoring the EGT. Watch for the maximum temperature achieved just prior to the temperature cooling down as you continue leaning. That maximum temperature is the maximum EGT for that cylinder. Do this for all your cylinders, record that maximum number (whatever it is), those are your maximum numbers at that particular power setting. They are not considered limits.

That 1300 in the original post is a number that person chose out of thin air for his purpose. It means nothing as far as you are concerned.

 

[Philly5G]

Slowly lean the mixture while monitoring the EGT. Watch for the maximum temperature achieved just prior to the temperature cooling down as you continue leaning. That maximum temperature is the maximum EGT for that cylinder. Do this for all your cylinders, record that maximum number (whatever it is), those are your maximum numbers at that particular power setting. They are not considered limits.

That 1300 in the original post is a number that person chose out of thin air for his purpose. It means nothing as far as you are concerned.

Thank you SW!! So peak IS the max reading on the EGT gauge (at different settings) aha!!!! Sounds like 1300 May be the peak at the OP’s climb power then?


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[rv8drvr]

EGT control

I started a PA12 build thread and we on to EGT readings. My 12 had a single CHT/EGT gauge that had little use except to help keep the CHT on one cylinder in check when leaning in cruise.

View attachment 50994

My RV8 has a 200+ H.P. Angle valve IO360 engine. Mixture control is important in almost all flight conditions. On initial climb to cruise altitude the EGT is kept just below 1300 degrees, 250 degrees rich of peak, through 4,500 feet, then below 1400 degrees through 7,500. Much above that altitude it does not matter what you do. It just depends if you want to go 185+ knots TAS rich of peak or 175 knots lean of peak. If hauling the mail down low, it will do 200 knots indicated burning 16-18 gph, keeping EGTs below 1300 and monitoring CHTs, which stay around 360 degrees. EGTs are important for knowing where the mixture is, providing quick mixture settings to obtain adequate cooling and horse power efficiency. One does not have to wait for CHT temperatures to catch up to what is going on in the engine.

This is not really important the way a cub is flown, but my example is important to show that the ported cylinders do make the horsepower Lycon claims. I talked to them about the carbureted O320 I am building and they say it will provide similar performance gains. I believe them. Fuel flow does not lie. No fuel equals no horsepower.



Notice the indicated airspeed at 6,500 feet. This is in level flight.

GM

 

[stewartb]

16-18 gph in a 360? EGTs under 1300? You’re sure burning a lot of gas. Why not use that instrument for best power?

 

[rv8drvr]

That's the point. When making 220 horse power in an IO360 you will have to burn fuel. It takes 200-250 degrees ROP to keep the CHT's down and the engine protected from detonation. EGT is the quickest way to know where you are. Best power at high power settings is bad for the engine.

This is not relevant to cubs, but was used to show the power gains from ported cylinders. Staying certified limits what can be done.

George

16-18 gph in a 360? EGTs under 1300? You’re sure burning a lot of gas. Why not use that instrument for best power?

 

[rv8drvr]

Back to building. We are assembling the right wing and fitting the flaps. What a pain.

This has been mentioned here on other threads and we are trying to figure out what direction to go. These are stock wings and we are adding Dakota Cub flaps with a Sullivan STC.

The STC calls for two different flap hangers (10703-03 and 04) and in additional notes that one can use two of the same hangers, which would be two 10703-04's. The Dakota kit provides a matched pair, DC10612-F, which should be the same as the Piper 10703-04 outboard hanger.

Everyone mentions aileron cable interference problems and it is obvious things will get very tight, if not near impossible, if the matched pair of hangars is used. It would appear that purchasing the 10703-03 inboard board hanger as per the plans would lower the hanger attach point one inch on the spar, lower the flap bellcrank away from the forward aileron cable, and allow the flap actuator rod to completely clear the aileron cable when the flaps are in the down position.

What have others here done.

George Meketa