J-3 mods

[JimC]

Now that the 0-200 is approved on the J-3C, I'm thinking about further mods, mostly but not necessarily with the goal of shortening the takeoff run. The 337 limits me to a maximum of 2640 rpm, so I want to work within that limitation. Some things that have come to mind are:

1) 75x35 prop (Cessna 150 seaplane prop for O-200 -- gives max static of 2600 rpm)

2) vg's on wing & tail

3) wickerbill flaps (gurney's)

4) extended gear

5) taller tires

6) convert ailerons to flaperons

7) upper half left clamshell door (don't want lower half because I don't want to relocate the throttles)

8) move front seat aft 1 inch

I'd appreciate any input or comment about ranking these in order of priority, and also any addtional ideas for other useful mods. Feel free to snicker or poke fun

My goal is to keep the weight increase minimal.

Thanks,
JimC

 

[Roger Peterson]

Try a Sensenich 76AK2-40. It is the aproved prop for a PA11S - 90. Works great on a 0-200.

 

[willyb]

J-3 Mods

Hi Jim I have the 75-35[1A90CF] on my 0-200 Legend.It will turn 2600 static.I'm not sure if it is the right pitch for an airplane this light and a J-3 is 200lbs lighter.I am leaning toward 38 pitch I think it will pull better.It sometimes feels as if it's doing a lot of spinning but not pulling much like running a machine in low gear for too long.The 1B90CF[square tip] is also certified on the the 0-200 in 74-40.If I am going somewhere I run at 2550 at 88 mph @ 5gph leaned.I'll let you know if I get a chance to test a different prop. Bill

 

[CptKelly]

Prop?

Hey, why not install a Aeromatic prop on that cub? Both ends of the performance spectrum would improve.

Mike

 

[JimC]

The Sensenich 76AK2-40 sounds intriguing. I hadn't thought of it.

I've recently run a 1B90 CM 74-41 on the O-200. It gives about 2470-2510 static and cruises at about 80-81 mph at 2200 rpm. Takeoff roll is good. I think the 1B90 CM 74-40 would be a slightly better match.

I'm presently running a 1B90 CM 70-42, which is the prop approved on the 337. It statics about 2500-2550 and turns about 2600 during climbout. Cruise is about 2 to 3 mph faster than with the 74-41. Takeoff roll is similar with both props, but I tend to lean toward larger diameter, flatter props because of their increased propeller efficiency.

I've previously run a 1A90 CF 75-38 on a C-85, and I too, think it might be a slightly better match for the O-200 than the 75-35 is.

I note in passing that on the C-85, the 74-41 gave much better takeoff and climb performance than the 74-43 did, and I preferred it, but cruise dropped a couple of mph.

As an aside, we tend to cruise at 2150 to 2250 rpm and let the cruise speed fall where it will -- a J-3 ain't going nowhere in a hurry anyway.

Any thoughts about the other stuff?

Thanks,
JimC

 

[behindpropellers]

The Sensenich 76AK2-40 sounds intriguing. I hadn't thought of it.



Any thoughts about the other stuff?

Thanks,
JimC

Sounds like a bunch of extra crap that is going to add weight.

Here is what I would do:

PA-11 windsheild.
-18 tank in the wing, remove 12 gallon tank.
original wheels and brakes.
VGS
0-200 with no electric.

Tim

 

[JimC]

Re the Aeromatic prop, only the high end performance would improve because we pitch flat for takeoff anyway, and aren't concerned with high-end cruse. And, iIf I remember correctly, the Aeromatic adds some weight. Don't hesitate to correct me, if your opinion differs...
JimC

 

[gcgilpin]

I'm running a 1B90CM7140 on a C85.

I noticed some takeoff improvement compared to the 1B90CM7142.

I'd like to try the Sensenich 76-AK-2-38. I've heard that it's a great match for the C85.

 

[Roger Peterson]

On a PA11 spray plane the Sensenich 76 will carry 20 gal more than a McCauley. Any McCauley.

 

[JimC]

Tim, I agree with a good bit of what you say and disagree with a few bits.

Specifically:

O-200 --Total agreement; it's already non-electric and will remain so.

Tall tires --Pretty strong agreement. They add a minimum of 30 pounds, and don't give any benefit for our mission except ground AOA (which can be alternatively provided by extended gear with far less weight increment).

Original brakes -- Strongly agree.

extended gear -- Disagree. They have good effect on ground roll without adding significant weight (perhaps a couple of pounds? ) They also increase resistance to nose-over moment during short landings.

Wckerbills -- Disagree. They increase the lift of the inner wing about 10-15% (max up to 20%) without a significant increase in drag. And they only weigh a few ounces while including the ability to remove or reinstall them in approximately 4 to 5 minutes. This is by far the easiest mod to install, but might be one of the most difficult to get approved.

VG's -- Agree. But point out that they won't significantly shorten the takeoff roll unless we also increase the ground AOA, which means that they must be installed in conjuction with either extended gear or tall tires to effectively assist our mission.

Conversion of allerons to flaperons -- Mixed emotions. They increase lift of the outer wing by about 10% with some drag penalty and will slightly shorten takeoff roll, but add complexity and increase weight by perhaps 8 pounds or so.

PA-11 windshield -- Strongly disagree. Will not reduce drag enough to have substantial impact on ground roll.

Replace 12 gallon nose tank with 15 gallon wing tank. -- Strongly disagree. Adds weight and complexity for no purpose that affects our mission. Will not significantly shorten ground roll. Increases safety due to moving fuel out of the cabin, while reducing safety during the refueling process due to more ladder work while refueling. Seems to be a wash on safety. I'd rather put 15 gallons in the nose tank -- but prefer to go the simple route and just stick with the original 12 gallon nose tank. More fuel = more weight = longer takeoff roll.

Upper half left clamshell -- Disagree. This particular J-3 does not have a sliding left window, and ventilation suffers during the summer. It's easier to retrofit an upper left clamshell than a sliding mechanism and the weight difference is insignificant.

Moving front seat aft an inch -- Disagree. One of us has to sit in the front seat, and it's a bit like putting two sardines in a one-sardine can. Weight change is zero and the cg envelope can easily accomodate the 1 inch aftward relocation of the front seat occupant. It actually helps during short landings.

Again, I'd welcome any comments or disagreement (disagreement forces me to think things through, so is most welcome). Note that I'm deliberately and temporarily ignoring the probable difficulty in getting a 337 approved for some of this stuff.

All the best,
JimC

 

[JimC]

Thanks for the heads up on the 76 Sensenich, Roger. Are they difficult to find used?

JimC

 

[JimC]

Two negatives about the Sensenich AK76-2-40 prop.

The -2 means that the prop is only 74 inches in diameter.

And this message from Sensenich..........
The 76AK series propeller is not approved for use on the O-200 series engine. For future reference, you can see this type of information on our FAA TC data sheets. If you look at Note #9 you will see the engine approvals. I have linked the 76A TC data sheet here:

http://www.sensenich.com/tc_1p2.htm

Oh well......
JimC

 

[Snert]

Shoulder harnesses and weld on front seat attach points. Then go fly it. Nothing increases performance like bugs on a windshield.

 

[gcgilpin]

On a PA11 spray plane the Sensenich 76 will carry 20 gal more than a McCauley. Any McCauley.

How sure are you on this? What engine? A C90? What was the pitch of the props?

 

[Lippy]

I had the engineering data done to make a removable front seat for the J-3. 4 pins and the whole thing comes right out. I ALWAYS fly from the back. Now there is so much room in there it’s not even funny. Yeah, a J-3 with a copious amount of room! A person could do a polka in there. Also we just put on AWB 1500 hydraulic wheel skis. Fueling steps are helpful, heavy duty SC gear I’m happy with, and Cleveland brakes I wouldn’t be without. Installed two 12 gallon wing tanks during restoration and put in a fresh C90-8. I’d prefer the 90 over the 100. When not on skis or floats it has 29” Gar Aero wheels/tires. I prefer these as the brake calipers are protected in the wheel versus exposed with a standard Cleveland wheel with bush wheels or good years. The weight of the tundra tires makes a very negligible difference but aerodynamically, it is a much dirtier airplane. Wouldn’t be without the big ol’ rubbers though. I’ve got a new extended gear hanging in the hanger but haven’t justified the goofy appearance yet…

Lippy

 

[Roger Peterson]

76AK2-40. Makes a great spray plane prop. If you want a few more revs, change it to 38. What is the difference in a c90-16 and a 0-200, through bolts. Same cam, crank, etc. I know it works with no bad harmonnics or other problems. Maybe you can't get it approved, but a lot of the other things sound like they could have a problem also.

 

[Roger Peterson]

"The 337 limits me to a maximum of 2640 rpm"

But I don't think it tells you what it has to be timed at does it. If you time it at 30 deg, not 24 deg, you will pick up another 200 rpm. If that runs you over 2640, repitch the prop.

Just a idea. What you need is a expermental J3 or PA11. Then everything is possible. Even a 1320 GW

 

[JimC]

Lippy, the main reason for preferring the O-200 over the C-90 is that the O-200 and prop were lying around the hanger gathering dust, and Rick would have had to purchase a C-90.

Re the large tires, around here the only thing they would help is takeoff AOA. Our terrain doesn't require a larger footprint than the 8.00x4. Extended gear seems a lighter weight and cheaper mechansism for achieving greater takeoff AOA

Your removable front seat sounds really neat. Did you also move it aft so the front seat passenger would have more room?

JimC

 

[Jerry Burr]

Mods

Hi Jim C. Flapperons on a -3 without flaps are a very bad idea. The weight is 5.3lbs and there is no drag unless they are deployed. But you know that. I enjoy the thread. Jerry.

 

[behindpropellers]

Jerry-

How would you do it....if you had to do it again? Certified....Experimental?

Tim

 

[R. JOHNSON]

Jim, I don't know how involved you want to get but a PA-18 head deck would really open the cabin up for increased visability and would accomodate the taller PA-18 that would give you adjustment in either direction. Again thiough this mod would be a lot of work for no STOL performance gain, just a thought.

Also maybe balanced tail?

Ryan

 

[Lippy]

Jim- The engineering for the front seat has/will cost a BUNCH of favors but it is worth every cent. I’ve got bad knees and the vertical application of my feet in-between the front seat and the fuselage is too ortho for what I can tolerate. Twenty minutes of flight with the front seat in and I’m in excruciating pain. We didn’t move the front seat back as I always fly from there anyways and I like my space. Dad thought we should move it back as his intent was to make room for a “plus size” girlfriend he thinks I *need.* My response was portly women are just fine so-long-as the financial statement in commensurate with her magnitude.

If she doesn’t fit in the front seat of the Cub the way it is, you’ll see my flying a Helio Stallion.

Lippy

 

[JimC]

JerryB, I fully agree with you about installation of flaperons without flaps ( I figure you already knew I'd share that opinion). However, I'm really curious about how they would do in conjunction with wickerbills (gurney flaps). I figure there is a better than middlin chance that you've already tried that combination -- if so, what was your impression ? BTW, I initiated this thread mostly because I thought it would lead to an entertaining discussion, and it has. Tim brought up a good question -- if doing over, would you go certified or experimental ? -- I'd go experimental (if I had the money). But then, as we all know; if toady frogs had wings, their little butts wouldn't go bumpety-bump along the ground.....
At the moment, a new experimental is out of the question for me.

Ryan, the pilots of this particular J-3 are all short, and all learned in a J-3 and each have over a thousand hours in -3's (I'm the low time -3 pilot, with maybe 1200 hours of my time in one). So we all got used to the crappy visibility decades ago, and it no longer bothers us. Also, its been 36 years since this plane has been recovered, and we're kind of hoping it will make 4 decades before recover (so far, the chances are looking good -- it's covered in fiberglass). So, maybe an -18 birdcage later.

Lippy, one of my friends has a -3 that is in the final stages of restoration (the 85 and prop that came off this -3 are going on his), and he is also the survivor of a parachute failure --neither main nor reserve opened fully, so he streamered in and landed in a tangle. He can fully identify with your bad knees. Because of his legs and ankles, he could greatly benfit from your front seat design -- is an STC available? My wife and I are both portly (and both broke), so I'm going to keep my mouth shut about portly wives. She hasn't flown in a -3 with me since the days when we were young and skinny. We still pretend to be young but have given up on skinny.

Roger -- can't time it to 30 (or 28) because it doesn't have the late cylinders. Eventually, when we replace the cylinders we'll go 28 (30 isn't allowed). I agree about repitching at that time.

All the best to all,
JimC

 

[jgerard]

I run the 1B90 74-42 on my 0-200 (F19 Taylorcraft) and climb out at 2500 indicating about 55-60mph. I cruise at about 98-103 @2500rpm. Hard to get exact speeds here in Tx cuz the dam wind blows too much :x Sure gets off short with the 15-20mph headwinds!

I heard the PA11 windshield will increase cruise about 3-5 mph. I also thought the pressure cowl was supposed to increase cruise speed.

If you take the nose tank out of a J3 can you remove the bolted in v-tubes, or dose that require welding the front up like the PA11?

Jason
N3673T

 

[JimC]

Jason, I have a 1B90 CM 7441 that I had to remove from the O-200 because it wasn't approved. I really liked the way the 74-41 performed on the O-200. Could I get a copy of your 337 ?

The 11 windshield will increase speeds, but conflicts with the nose tank. The pressure cowl will also help. The 65hp 11 that I flew was about 10 mph faster than the 85hp J-3.

If you remove the v-tubes from the -3, you do have to modify the fuselage to resemble the -11. It should also be possible to engineer a mod that removes the v-tubes without requiring removal of the nose tank, but approvals would probably be difficult.

I have a recent rotator cuff injury and don't have the $20,000 required to repair it, so moving fuel from the nose to the wing is out of the question for me. I can't lift jerry cans overhead to refuel a wing tank, and we don't have a gas pump at our airstrip.
JimC

 

[jgerard]

The 1B90 is on the Type Cert for the F19 Taylorcraft and there is no RPM restrictions. You may be able to use that data to get a 337 for your CUB. The 1B90 looks like a baby Borer prop for the small continentals.

Jason
N3673T

 

[JimC]

Thanks, Jason.
Several 1B90's are approved on the J-3 & PA-11 Type Certificate. That doesn't help. The problem as I understand it, is that the 74 series is not approved on the O-200. Is it specifically approved for O-200's in the F-19 Taylorcraft Type Certificate?
All the best,
JimC

 

[JimC]

The F-19 Type Certificate 1A9, allows a 1B90 7443 prop, but the associated static rpm limitations preclude use of a 7441 and do not allow decent takeoff power to be developed. To get good takeoff performance with this prop, you'd need to static about 2470-2520 rpm, which is way over the limit set by the F-19 TC.
JimC

 

[Frenchy]

Can someone tell me why we have to reduce timing from 28 to 24 degrees on those older style 0-200 cylinders. Is it because of head separation problem ,detonation or ???

Claude

 

[Longwinglover]

Cause the FAA said so. Cracking cylinders.

John Scott