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Jbone
05-05-2020, 05:47 PM
I've got a question for any J-3 owner who's flown their Cub out of high elevation airports. 35 years ago, I had a 1946 model, and am looking at getting back in. Back then, my 65hp Cub was operated at sea level, and performance wasn't a huge deal (though the new owner promptly flew it into a tree trying to take off with his buddy on a wet grass strip one hot humid morning. . . but that's another story). Today, I'd be looking at basing the airplane at 7,600' MSL. I'd mostly be flying in the cool morning air, but, for example, today's late afternoon temp. is 70 F, and the density altitude is 9,700'. The runway is a paved 8,100', and obstacles aren't an issue. Is operating a 65 hp J-3 in this environment going to be feasible? Would holding out for a 90hp model be advised, or can the original do the job? Along the same line, how does the 65 hp's fixed carb do up high. Seems like the mixture would be overly rich. I understand that the 90 has mixture control.

I really appreciate the input.

Thanks!

mvivion
05-05-2020, 09:18 PM
I’d find a 90 hp plane if possible. I also liked the Marvel carburetor on my 90 hp PA-11. I had the mixture control connected, and it really helped. The Stromberg carbs mixture doesn’t do much.

I had that 11 at 4500 msl base, and landed a few 7000 plus airports, but minded the DA, and rarely heavy.

MTV

bob turner
05-05-2020, 10:51 PM
I remember leaving Flagstaff in a 65 HP Cub on a 90 degree day. You just need a lot more obstacle-free space. Happily, the ground falls off about five miles south of the airport and you find yourself at cruising altitude.

I did go through Butte & Bozeman during the summer in that Cub. Easier than I expected. But I vote with MTV.

bodumatau
05-06-2020, 05:49 AM
All the cubs thermal beautifully, so all you need to do is clear the trees till you pick up a thermal then up up up you go
I was being bashed around at 4000ftMSL (500ft AGL and 95ºF) a couple of months back, had enough of seeing the trees, pulled into a nice thermal and in less than 5 minutes I was at FL135 at a wonderful 46ºF enjoying being cold, climbed so fast I was needing to clear my ears every 10 seconds or so, saw 2500ft/min for a bit when the thermal was pulling really strongly.
ATC asked me to confirm my Altitude 3 times when I asked to enter the TMA :lol:

Penguin
05-06-2020, 06:50 AM
Im based at 7000’M, and usual spring-summer DA is 9000+. I just sold my ‘44 L-4 w a C90, Stromberg, no mixture, wood Sensenich. I would fly 2 people in the winter but even with that beast of a motor I was mostly single place in the summer. I’d take 2 people in the summer early morning - and even then just lighter people. Im 195lbs, the L-4 was 729 empty. The new owner is @ sea level & reports space shuttle climb performance.

astjp2
05-06-2020, 08:52 AM
I took off in a 65 Taylorcraft from Afton WY, almost didnt make it over the pass, same with Smiley Creek, both were summer and warm days, I now have an O-200-8 with a seaplane prop. Tim

Mot
05-06-2020, 09:21 AM
"On April 12, 1951, Lieutenant John W. Hodgkin, age 42, a pilot stationed at McChord Air Force Base, flies his ski-equipped Piper J-3 Cub from Spanaway Air Strip to the top of Mount Rainier (14,410 feet), establishing a new world record for a high-altitude landing. However, when Hodgkin prepares to leave, the engine will not start in the rarefied air and he is forced to spend the night on top of the mountain, huddled in the Cub’s cockpit."

Read the rest of the story here https://www.historylink.org/File/8469

soyAnarchisto
05-06-2020, 04:03 PM
C90 in the J3 is rpm limited to 85hp on the TCDS - keep that in mind - so don't pay a premium for that over a C85. The legal prop options are better (more thrust) on the C85. I owned a C85 J3C for several years based here in Colorado at 5300' and flew it often over the big rocks up to 14K. I wouldn't consider a C65 for density altitude operations.

Jbone
05-06-2020, 08:10 PM
C90 in the J3 is rpm limited to 85hp on the TCDS - keep that in mind - so don't pay a premium for that over a C85. The legal prop options are better (more thrust) on the C85. I owned at C85 J3C for several years based here in Colorado at 5300' and flew it often over the big rocks up to 14K. I wouldn't consider a C65 for density altitude operations.

WOW! 14k in a Cub! Impressive! Thanks everyone for the input. I’m pretty well convinced that a C-85 is in order. Now to find one.

Cub Builder
05-06-2020, 11:13 PM
I had an A-65 powered J-4 based at KLAM (7172' MSL). Flying by myself was never a problem. Flying passengers in the summer was challenging if I had the added wing tank full of fuel as well. Also had a C-85 powered Champ based at the same place. Never had a problem with 2 people even with the optional wing tank full in the summer. Good friend had an 65-HP Taylorcraft based there as well. Never had any issues. But, it does take some patience with climb, especially if you don't watch the weight and get it a bit over gross. Summer afternoons the DA was typically over 10,000' and often times reached 11,000' on the hotter days. None of them flew like the 160 hp SuperCub Clone I built later, but I never really ran into any issues flying in the high country with low HP. I was based there for 32 years.

-Cub Builder

Jbone
05-07-2020, 10:55 AM
I had an A-65 powered J-4 based at KLAM (7172' MSL). Flying by myself was never a problem. Flying passengers in the summer was challenging if I had the added wing tank full of fuel as well. Also had a C-85 powered Champ based at the same place. Never had a problem with 2 people even with the optional wing tank full in the summer. Good friend had an 65-HP Taylorcraft based there as well. Never had any issues. But, it does take some patience with climb, especially if you don't watch the weight and get it a bit over gross. Summer afternoons the DA was typically over 10,000' and often times reached 11,000' on the hotter days. None of them flew like the 160 hp SuperCub Clone I built later, but I never really ran into any issues flying in the high country with low HP. I was based there for 32 years.

-Cub Builder
Weight and temp are key. I was just looking at a J-3 on Trade-a-Plane. Beautiful Cub. 85 hp conversion, along with a host of upgrades, including electric starter and its battery, two 12 gal wing tanks, and a 2 gal header tank replacing the fuselage tank. This airplane had an empty weight of 811! With a max gross weight of 1170, that leaves a 359 lb useful load. Not very useful. Fill the tanks and you can carry 215 lbs. This airplane needed an 85 hp just to carry itself and all the extras, and probably often flew above max gross. I wonder what the weight difference is between a 65 and 85? Are most 85 hp electric start? That option alone is a lot of added weight. Is it really necessary? Is an 85 any harder to hand prop?

The kind of flying I have in mind would mostly be early morning solo. The cool air is almost always dead calm then. Around here (the Rocky Mountains of Colorado), few pilots do much pleasure flying in the afternoon. Based on your experience “Cub Builder”, having a simple, lightweight 65 may be the answer after all.

arnold bronson
05-07-2020, 12:54 PM
I had an A-65 powered J-4 based at KLAM (7172' MSL). Flying by myself was never a problem. Flying passengers in the summer was challenging if I had the added wing tank full of fuel as well. Also had a C-85 powered Champ based at the same place. Never had a problem with 2 people even with the optional wing tank full in the summer. Good friend had an 65-HP Taylorcraft based there as well. Never had any issues. But, it does take some patience with climb, especially if you don't watch the weight and get it a bit over gross. Summer afternoons the DA was typically over 10,000' and often times reached 11,000' on the hotter days. None of them flew like the 160 hp SuperCub Clone I built later, but I never really ran into any issues flying in the high country with low HP. I was based there for 32 years.

-Cub Builder


And with your new body it would never be an issue.

soyAnarchisto
05-07-2020, 03:14 PM
Very few 85s have electric start. I would never put one on. The 85 is just as easy to start by hand as a 65 - so no problem there. Keep also in mind that you will never make rated horsepower here at altitude because of DA. So 30% less power on a 65 makes a big difference. The 85 is the one you want. And you will want a wing tank. I bought mine with just the standard 12g header and flew it all over the Frank Church with a couple of spare ABW fuel bags - very exciting - maybe too exciting. I came home and had a wing tank installed post-haste.

It is a 1 up plane though except for maybe a few circles around the patch on cool mornings. They are awesome planes and fit like a glove. A champ is an equally good option - but I prefer tandem arrangement. I'm a skinny lightweight person - comfortable with lightweight backpacking gear and adventure. It's a fantastic plane. Hard pass on a 65 for me.

The J3 was my first plane. First taildragger. First hand propped plane. First bushweel-equipped plane. I flew the **** out of it - coast to coast. Learned to find orographic lift all over the high rockies. Learned when to stay my little ass on the ground. Learned to land on taxiways. If I could've afforded two planes, I'd have kept it. But 180s were calling me...

Good luck.


Weight and temp are key. I was just looking at a J-3 on Trade-a-Plane. Beautiful Cub. 85 hp conversion, along with a host of upgrades, including electric starter and its battery, two 12 gal wing tanks, and a 2 gal header tank replacing the fuselage tank. This airplane had an empty weight of 811! With a max gross weight of 1170, that leaves a 359 lb useful load. Not very useful. Fill the tanks and you can carry 215 lbs. This airplane needed an 85 hp just to carry itself and all the extras, and probably often flew above max gross. I wonder what the weight difference is between a 65 and 85? Are most 85 hp electric start? That option alone is a lot of added weight. Is it really necessary? Is an 85 any harder to hand prop?

The kind of flying I have in mind would mostly be early morning solo. The cool air is almost always dead calm then. Around here (the Rocky Mountains of Colorado), few pilots do much pleasure flying in the afternoon. Based on your experience “Cub Builder”, having a simple, lightweight 65 may be the answer after all.

cubdriver2
05-07-2020, 03:56 PM
My first plane was a Pa15 Vagabond with the Lyc 0145, maybe 55hp going downhill. Even based it on my 900' strip for a few years, on skis too. You learn to fly in that and everything ( even 65hp Cub ) seems like a hotrod

Glenn

Jbone
05-07-2020, 05:34 PM
Very few 85s have electric start. I would never put one on. The 85 is just as easy to start by hand as a 65 - so no problem there. Keep also in mind that you will never make rated horsepower here at altitude because of DA. So 30% less power on a 65 makes a big difference. The 85 is the one you want. And you will want a wing tank. I bought mine with just the standard 12g header and flew it all over the Frank Church with a couple of spare ABW fuel bags - very exciting - maybe too exciting. I came home and had a wing tank installed post-haste.

It is a 1 up plane though except for maybe a few circles around the patch on cool mornings. They are awesome planes and fit like a glove. A champ is an equally good option - but I prefer tandem arrangement. I'm a skinny lightweight person - comfortable with lightweight backpacking gear and adventure. It's a fantastic plane. Hard pass on a 65 for me.

The J3 was my first plane. First taildragger. First hand propped plane. First bushweel-equipped plane. I flew the **** out of it - coast to coast. Learned to find orographic lift all over the high rockies. Learned when to stay my little ass on the ground. Learned to land on taxiways. If I could've afforded two planes, I'd have kept it. But 180s were calling me...

Good luck.
Okay! Good to know that not too many 85's come with electric start. By the time you add a starter and its associated hardware, plus a heavy battery and its contractor, wiring etc. you're really subtracting from the useful load. I want to keep the empty weight down. Even an aux wing tank is something I may be able to live without. What's the fuel burn of an 85? 5 gph? I don't remember what the 65 burned, but I'm thinking an 85 w/ a mixture control might do as well at high elevation than a "permanent rich" 65. Another thing. . . the max gross of that TAP Cub was 1170. I understand that some Cubs are 1220. When did that occur, and is it associated with the metal spar?

As I said, I owned a Cub back in the 80's, so I know how much fun they can be. My favorite thing was giving rides. Everyone loves the Cub! I already have an RV-6 for when I need to be somewhere, but I'd really like a "low-and-slow" fun flyer, and I'm hoping I can make one work in (around) the mountains.

bob turner
05-08-2020, 09:42 PM
I have two J3s and a J4. All have 85s with electric start. There is another 85 Cub here with starter and a C90 Cub with a starter. And yet another Cub with A-65, no starter. Sea level; we all do just fine.

I agree - easy to hand start. I did a half century propping from behind, and at 79 am still plenty agile enough to still do it solo. But at this point it is much safer to push the button. We use very small batteries and get 50-75 starts per charge. Weight penalty -about five lbs for the engine; maybe 17 for the starter, battery, and cables.

If you buy a C-85 and plan to fly behind it until you are 90, I recommend the Dash 12. That way you have the option.

BC12D-4-85
05-08-2020, 10:24 PM
The higher the engine's effective compression ratio the better the high altitude (or high density altitude) performance and ease of starting. Not a new concept and one reason power decreases with altitude in normal engines.

Gary

soyAnarchisto
05-13-2020, 02:55 PM
One more common misconception about "permanent rich" since you mention it - the stromberg carb is an altitude compensating design - which means it automatically leans to compensate for DA unlike the marvel carb which will require mixture control. The stromberg design works great - you can get some cruise fuel economy by wiring in mixture but it won't help you climb out because you will be full rich anyway. What you will do is make your landings really exciting the first time you try to go around, push in full throttle when you forgot to go full rich beforehand. The engine will die on you and you'll be landing soon enough. Do more research if you think you need to add mixture control to the Stromberg - or spend unnecessary money to swap a stromberg out for a Marvel. It wont get you any better climb performance all other things being the same.

For an understanding of the gross weight - you should read the type certificate (A-691 rev 34) . It's available from the FAA. It explains the various gross weight ratings based on year, serial number, installation of floats, and the modifications to the landing gear to get it to 1220. It explains all your engine and prop combinations. If you are flying a J3 it's the closest thing you will get to a POH anyway so you need to understand how to read it - and probably have a copy in the a/c in case you get ramp checked and your friendly FAA person doesn't know what the fricc a CAR 4 aeroplane is. See here: https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/EC36F12E6E139C5B8625785C006C09C8?OpenDocument

Farmboy
05-15-2020, 07:56 AM
"

Read the rest of the story here https://www.historylink.org/File/8469

I love this part...part BS and all pure pilot.

“In a statement before the court, Hodgkin declared that private aircraft should not be banned from national parks; the mountains were his religion and the flight was his crusade against the injustice.”

...”Commissioner Clifford found Hodgkin guilty of the offense and then fined him $350 and gave him a six-month suspended jail sentence. In closing, Clifford told Hodgkin that he was obviously not a criminal, but he needed to reevaluate his thinking.”


Transmitted from my FlightPhone on fingers...

mvivion
05-15-2020, 08:26 AM
To me, the best argument for a Marvel carb with mixture control is not the ability to lean so much, though it helps, but rather the ability to shut the engine down with idle cutoff mixture control. This permits hand propping from behind with mixture in idle cutoff. When engine catches, mixture to rich. If anything untoward happens on the start, the engine will die before it can do much damage.

Frankly, every time one of these airplanes gets away on a prop start, we’re one step closer to “regulation” regarding hand propping. And, believe me, we do NOT want to go there.

MTV

bob turner
05-16-2020, 01:20 AM
I don't solo hand start Champs, T-carts, or J4s for exactly those reasons. A buddy with a Chief invented a rope trick that is almost as good as a Schweitzer tow hook. Makes it a little safer.

With starters on everything, I no longer routinely prop from behind. 55 accident-free years, and time to act slightly more responsibly. So, agree with MTV.

AKjurnees
05-16-2020, 05:35 AM
If you are that inexperienced in hand propping a J-3 from behind, get a -12 engine with starter. The Stromberg carb gives me zero issues, it’s the mag switch you need to be concerned about with proper grounding.

If anything turn the fuel valve ON for a minute to fill the carb bowl, then turn the fuel valve OFF. Prime and start the cub like normal. That will give you enough time to adjust RPM if needed and turn the fuel back on.

If some how the tied down cub runs away from you at full throttle, it will run for just a few seconds then quit.

Just treat the prop like a loaded gun when it’s in the hangar.