Pa12 Rebuild Project

Hey all-

I'm pretty new to this site and all but I am rebuilding a PA 12 and need some opinions. This plane is going to be used primarily for some bush fun and tight strips. What are some good options and mods that I should look at. If I put it into the experimental catagory, than what could I do that I couldn't do just leaving in normal catagory. Also what have some of you done(or are planning to do) to your aircraft.

Any info would be appriciated and thanks so much, this really is a great web site.

Dan

Flaps - PA14 style preferred- balanced tailfeathers- 150 or 160 hp engine-Borer Prop- larger tires and clevelands- pnuematic tailwheel. Thats a minimum. Keep it certified.

PA-12

In addition to the above, Keep it light! The lighter the better for performance, especially if you are planning on tight strips. Don't load it down full of instruments and heavy interior panels. Other than the PA-14 or 18 style flaps, keep the wing stock and light with maybe the VG's.

Put in a light weight starter and Niagra oil cooler. Copper starter cables.

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Cub gear, seaplane door, 150 or 160 hp on a short mount, flaps, reinforced tail bay, extended baggage, cub tailfeathers, extended leading edges, big tires, brake boosters, skylight, top deck X brace, better tanks, metal inspection panels at the tail, inertial reel restraints, and if it's certified, increased gross weight. That'll keep you occupied for awhile. After that you can start the big mods like a second door and lowering the rear spar attach point along with revising the tail geometry. Mission vs. economics. The ultimate upset stomach.
SB

Did anyone say extended wings with long ailerons.

If you're going experimental contact Jerry Burr about a droop aileron system. You can vary the droop, or even turn it off.

If you're gonna be working a -12 short, you'll want a long wing and big gear and/or tires to get the angle of attack high.

If you need the ultimate STOL -12, make sure you attempt to keep it light. That means fewer mods, and only the ones that will increase lift.

Who's next?

Dave Calkins.

I'm doing a 12 rebuild. Hoping to get it in the air by the first of the year. No flaps. AM using fiberglass fabric, landing and nav lights, 8.50x6 tires and Clevelands (am considering widening the rims to give a more 'cub-like' look), O-320 on standard length mount, Pawnee tailfeathers. Am thinking about light weight starter and small alternator, or perhaps removing the starter entirely -- any recommendations in that regard? Other thoughts and advice are welcomed, though money is an issue, as it is for many of us.

Jim

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You probably don't really mean the old fiberglass (razerback) cover, but poly right? Fiberglass hasn't been used for years, (heavy, and the polys are much easier to work with).

Tight strips in a PA12, I'd recomend tall main gear and tires to get the angle of attack higher when 3 pt., 150-160 HP. And of cource keep it light.

If you are on a budget and want to save weight, the lightest, cheapest starter you can get is the appendage hanging from your right shoulder. I would put in a split, or seaplane door so you can prop it from behind like a PA18.

I must be weak! I tried prop'n my 0320 from behind and couldn't do it. No problem prop'n from the front using left mag only or even both mags. Is there a secret to prop'n from behind. I'd like to be able to achieve this technique.

prop from behind

Stan...Use your whole body during the throw from behind. Make sure your prop normally stops with a blade angled to the right so that it's an easy grab for your hand. Then when you throw it through, bend your knees during the stroke and use your upper body mass to help send it through the cycle.

(The split door on the PA-18 allows you to get at the throttle and climb in pretty easy as opposed to running around the lift strut with other types)

Thanks, I'll try it again.

Look in the tips and tricks section under "empty weight", the proper method of bleeding off the compression when hand proping is discussed there.

Mark,
I had read your procedure before, but thought bleeding off compression was an error. Are you relying on momentum of prop carrying over to next cylinder firing or what ? I will try your method tomorrow. Thanks

To Jim:

Why no flaps?...and I hope you're not using "razorback", unless you know something that all the rest of us never learned.

To Stan: (Sorry, I posted this while Mark was responding, this is an edit in these parentheses)

Propping from the back....Make sure your prop is indexed to TDC (impulse snaps, plugs fire, etc.) with a blade at 7:30 o'clock when viewed from the front....that's below level and to the right , 4:30 o'clock, when viewed from behind.

Know what it takes fuel and air-wise to get YOUR engine started. Try different combinations of prime and throttle settings. Try these with your elec. starter.

.....Now you have established when the impulse/plugs will fire, and at what settings the engine starts most easily.

...with a high-compression engine that would normally be hard for a "weak" arm to fling, you CAN get it going....get the proper prime and throttle setting, with the mags "OFF" (verified by each time you shut down using the switch instead of the mixture control)...pull the blade thru just shy of impulse firing....hold it there until the compression bleeds down....NOW, just push that blade past the impulse fire spot (4:30 viewed from behind)....If the fuel is right, your mag switch is set to"LEFT" and the "P" leads are wired to properly ground the right mag when "Left" is selected, and the bottom plugs aren't fouled, you'll have 4 spark plugs doing the job of swinging the blade that your "weak" arm wouldn't. If the bottom plugs are fouled, you'll only have 2 plugs doing the job, the upper ones on one side.

It is good to have a Cub-style or top-hinged door so that you can easily get at the controls in the cabin.

It is good to tie the tail to ensure that your a/c won't lurch forward...don't trust your parking brakes, unless you already know the hand-prop routine and didn't need to read this anyway. It's just not worth the chance of destruction, for the time it takes to tie the tail. Once you have it running and idling well, then go untie the tail.

Razorback? Jim, what are you thinking?

Dave Calkins.

stewartb-- Clue me in on the lowering the rear spar attach point mod. is the a certified Mod and what does it do the the flight charicteristics

Surely I do mean Razorback. Unfortunately, Sam went broke during the period when he was doing my plane, and it eventually came home in unattached pieces and with some pieces missing. About that time, I had two daughters in college with a somewhat higher priority, and was busy starting a new business, so after returning home, it sat for quite a while as did all my planes. Although, except for this one plane, I've always recovered with Grade A cotton, Razorback isn't actually as heavy as many folks think, and it is quite durable and gives a smooth finish. A close friend in the hanger next door has a J-3 his dad covered in Razorback years ago, and he hopes to take it to Oshkosh later this decade, to celebrate the 50th anniversary of its last recovering. His plane still looks fine, and gets off the ground in about 170 feet with him in it, and about 190 to 200 with me (I wish I were skinny too), even though it has a cruise prop and is about 10 mph faster than my J-3 with grade A (both with C-85-12F's). I tend to like working with fiberglass, so I have more good things to say about the process than bad, and no one could ever complain about the quality of Sam's work (for example, he has a tendency to align the slots in all screw heads, which really looks nice). The reason I'm not considering flaps is that the covering is complete, and I'd rather spend money on the engine and get the plane into the air rather than spend it on taking the wings apart again with still another recover and increased downtime. Immediately before Sam recovered it, I blew $3500 having another guy recover it (with Ceconite if I remember correctly) -- after he finished, he called and said, "I think we have a problem". We did. You could see sporadic hot iron marks in the fabric left from overheating, and you could actually poke your finger right through the fabric at those spots. As I was stripping that new fabric off, it felt a lot like standing in a cold shower while chunking $100 bills down the drain. A problem you don't have with Razorback. At my age, if I do go on and get the 12 into the air, there is a good chance I won't have to recover it again in my lifetime, and when I recover the J-3 and 11, I'm very likely to use the fiberglass fabric on them as well, hoping for those to be my last recovers as well The next time will be my 4th recover on the J-3. As another aside, I can't begin to express my appreciation for all the good advice I've received since finding this website.

Re propping from behind, that's the way I've always propped my J-3, and I thought it was the way everybody propped. You just reach forward, put your fingertips on top of the blade and push down, then grab the top braces and swing into the plane from the front side of the struts (easier to do than describe when I was young -- easier to describe than to do now). For some reason, the prop position on my J-3 was at 2:30 when seen from behind, not at 4:30. But it started fine, usually on the first flip, so I'm not going to complain. Re tying the tail down while starting, for about 17 years I did search and rescue flying, operating off airports. When away from airports, what should one tie the tail to? And where are the parking brakes on a J-3? If they have them, I never found the ones on mine....
Cheers,
Jim

S2D,
12's have less angle of incidence than cubs. You can get the cub angle by lowering the rear spar attach 7/8" on the 12, but the tail has to be realigned to the same plane. I know of guys that have done it (quietly) and like it, but I have been told that the amount of work it takes isn't worth the gain. Even after the tail is reworked, it sits in a different position relative to the wing than a cub tail. I don't know of a legal version of this mod, and I can't imagine a field approval would ever happen. I'm convinced that my 12 will perform adequately for what I intend to use it for, so I'll just stick big tires on it and practice carrier landings.
SB

I'm missing something on hand propping ! Tried the "technique" this past weekend and never got a pop. Had to rely on the starter again. Maybe it is the autofuel and high flashpoint. I am able to hand prop from the front, pulling against the compression. Bleeding off from the rear and then turning on #2 mag and pushing through at 4:30 gets me nothing. Don't give up on us as it seems sereral of us are interested in hand propping.

Stan,

I have never been to TN but I would love to come, if you find a really good airfare I will personally come and work the technique with you. I suspect that your prop is still not positioned correctly? Also I concur that for most it is much safer to prop from the rear. I would encourage anyone to "practice" in a tiedown till you "master" the technique for "your" plane! Trust me they are all a little different. Usually I have found that it has to do with what the temperature is, is it a cold start, restart, and is the Mag timing 'nuts' on/?

I am ready to come to TN really!!

Tim

Tim,
Until you get here, I'll keep trying to figure out what I'm doing wrong. The hills and lakes of E. Tennessee would welcome your plane, it would just take a couple of days to make the trip. Thanks for the feedback.

Stan, what position is your prop in when you shut down? Look at the little picture of my Cub, and the pictures of most other Cubs, that is where it should stop. If you are standing behind, by the door, the blade you pull down on should be about 2:00. When you pull it through, the impulse should snap about 4:30. If your prop is installed incorrectly, you will have a hard time starting it.

Mark,
My prop is exactly positioned like you show and describe. I'll work with it some more this week. Obviously, I'm missing something.

Just be careful, I don't want to hear next week that what you are missing is a arm, or your head.

This may sound coy but, I have even been caught being complacent about whether or not the "mags are on"??

Especially if you start 'barely repositioning the prop, and or "bleeding off compression"

ALWAYS TREAT THE PROP AS HOT AND DON'T LET ANYONE YAK AT YOU WHILE PROPPING YOUR PLANE!

Also I am aware of several cities that have passed ordinances that "require a "licensed pilot" at the controls when "hand propping an Airplane".

Tim

A tied tail is better than a licensed pilot any day, and for more things than just propping. But a body at the controls is a good thing.

Hot prop, Cold prop, KILLER PROP. Loaded Gun, unloaded Gun, Killer...if pointed in the wrong direction and discharged.

Treat this whole process as carefully as if you were removing a mosquito from your shin with a chainsaw......VERY carefully.

With care, a proper fuel charge condition, and a good spark plug (not oil, lead, carbon, or 100LL-fouled), propping is EASY.

Maybe an experienced teacher directly supervising the process is the way to go about learning it.

YEAH, that's definitely the way to go about learning it.

Dave Calkins.

hey thanks all for the grat input. Can anybody tell me if atlee dodge has a web site or a phone # that i can contact him at?(or a catalog) Also what is the difference between 14 and 18 flaps?

thanks so much
dan