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Light Cub/Heavy Cub

drew

Registered User
Fort Leavenworth, or KTNU, Iowa
My wife and I are advance planning our next project (within the next 2-3 years) and I've seen several comments on this forums of the benefits of the "Light Cubs" i.e. PA-18-95, or "flap-less wonders".

We want to go experimental, and my gut tells me to build an O-320 powered PA-18 replica as the way to go, but I'm wondering what advantages an O-200 powered "light cub" might be. We won't be doing a lot of really rough off-airport work, though we'd like to do a little mountain flying. We'd like 100 kts cruise or thereabouts and the most payload will probably be a 50 pound suitcase.

It seems to me that for the builders' dollar, you'd get more value with an O-320 powered machine, with flaps. I look forward to any and all comments relevant to this.
 
Check out the new Legend Kit. Only thing its missing are flaps which you could add yourself. When building a cub "light" care must be taken to make compromises. A seamless high gloss finish most likely will way up to twice what a minimum cover and paint weighs. The 180 hp weighs more than the 150 hp. A radio stack with a six pack weighs more than basic flight instrument group. And so on. I'm going to a lot of trouble adding flaps to a set of Wag Aero wings because I think its important. I want to get the most out my Super cub and flaps are a must. An original 150 hp 18 with electric weighs around 1100 give or take. That's you goal. Building a wide body will weigh more finished than a narrow body. Tundra tires add weight. I suggest you go fly a good original 150 hp super cub and by yourself for an our than load your wife and all your baggage and fly it some more. You will see the difference. Still a good performer. I would recommend the 12 or a wide body. Take a look at the 2+2 by Wag Aero. The Bear Hawk is another neat airplane. Good luck. The airplanes mentioned would be a little more roomy for cross country flying but still have the mountain performance you are looking for. In Europe I can see where staying away from the gas guzzlers would be important. A 150 hp can sip the gas however, trying to make a hundred knots day in and day out will obviously result in higher fuel bills. 115 mph is at the top of the performance curve for the cub series. The think Bear Hawk is a bit faster on the same HP.
 
Although you may never plan on selling the airplane (we don't plan on divorces, job changes and lots of other things that happen in life) you will have just about as much money in the light cub as you will have in the heavy cub but you will not have anywhere near the resale value.

Just another consideration.

Bill
 
I fly an L18C a lot, in fact I got to play with it last night for several hours. It is a sweet flying airplane but two people and some bags and you are challenged. You have to figure your mission. Fuel, performance, payload all have to be considered.
 
Good responses. My wife keeps asking to take one of those mountain flying courses and self-guided tours and seems to me that you need 150 horses or there's no reason for going.

It seems the cost of an experimental O-320 is about the same as an experimental O-200 engine. I was initially thinking about doing a stretched Pacer, but realized that my wife likes "looking down" when she flies, and side-by-side seating gets in the way of that.

Drew
 
I doubt if you will get 100Kt. cruise from any cub with 100hp or 150 hp. If the mountain flying you want to do involves take-offs at more than 5000 ft density altitude, then performance from a 100hp machine will be marginal at best. Many places you can land, but can't take-off from!!!
 
If you decide on the 150, then go the extra mile to a 160. Difference is dramatic, both in power and in fuel burn. We have seven Cubs here that I fly, and the 160/Borer Cubs are hands down the best. The ones with cruise props are a lot faster - maybe because they don't have extensive heavy mods on them. The stock 160 Cub seems to be the best all-around, but the Borer seems to make a significant difference in ground roll on takeoff.
 
I fly an O-200 powered J-3 (about 80 pounds lighter than some of the kit cubs). With one person on board, I get off about 110 feet shorter than a 150hp SuperCub with VG's. I can probably beat it to 1000 feet AGL and can certainly beat it to 500. BUT, with two on board, takeoff and climb deteriorate so they are about the same as the SuperCub. Though I can do 103 kts wide open, cruise is more like 75 kts. Building a light PA-11 clone would give about the same takeoff roll, would climb better, and would be 8-10 kts faster. In my opinion, if you will be by yourself most of the time, then the O-200 would be fine (particularly if you use 9.5 pistons). If you fly two and baggage most of the time, go a lightweight 160hp plane that is similar to the early PA-18. If experimental, go 9.5 pistons for roughly 165 hp.
JimC
 
I like the idea of nine and half pistons. Good idea. Think I will change mine.
 
9.5 is pretty high to burn autogas. If you plan to use auto then 8 or 8.5 may be a limiting factor.

Bill
 
JimC said:
I fly an O-200 powered J-3 (about 80 pounds lighter than some of the kit cubs). With one person on board, I get off about 110 feet shorter than a 150hp SuperCub with VG's. I can probably beat it to 1000 feet AGL and can certainly beat it to 500.
JimC

Well, not sure what configuration the 150 18's you are comparing your J3 to, but 110' shorter and beating them in Climb.....Not sure if I should pull on the hip boots, or just go for the chest waders, this is getting deep....

For what it's worth, I've owned and flown Cubs in ever different configuration. The Continental powered Cubs are fun little toys, but to work the airplane you want the Lycoming. Also, my 90 hp Cub burned close to 6 GPH. My current 160 burns a little over 7 and goes a lot faster, so fuel economy is about the same, I just get there faster, can carry more comfortably, and will take off and land just as short. My 150 Cubs did burn more gas, definitely go to the 160.

If you are building from scratch, start with a straight mount 160, and build a basically stock PA18 behind it keeping everything as light as possible. Don't get caught in the heavy duty this, and heavy duty that trap that most do or you end up with a pig. If you don't need it, don't put it in.
 
11.2:1 is usually taken as the compression limit for automobile engines being run on auto gas. I don't think I'd trust an aircraft engine at anything like that compression ratio though. For an experimental aircraft engine, 9.5 might likely work fine on premium auto fuel.

We've run the J-3 against two SuperCubs. One was a 150 with vg's, the other a 160 without. The -3 gets off about 110 feet shorter than either of the SC's when all three are lightly loaded, and can beat them to somewhere between 500 and 1000 feet AGL. It isn't exactly outclimbing them, its just that it is already something like 25-30 feet AGL and accelerating when they break ground, and it takes them a while to catch up. For the -3 with a 220 pound pilot and half fuel, time from a standing start to 1000 AGL is just under a minute, so ROC is a little over 1000 fpm even with the takeoff delay reducing the average rate of climb. With the same wing, the -3's lighter weight is a substantial asset and less power is required for similar performance.

Re landing, I'd expect the -18 to outperform the -3. In no wind conditions, about the best I can do on grass is a full stop 195 feet from the threshold. Usually I screw up my energy control during short final and take more like 240 feet. Most any -18 should beat those numbers substantially. Re working cubs -- for about 17 years on and off, I did search and rescue flying off the sandbars and islands of the Mississippi and White Rivers. For that mission, I never found any plane that served better than a light -3 with a very flat prop. If you're gonna haul moose, mooses, (meece ? ) though, the -18 will serve your needs better. We had very few moose around home. That said, if you're going anywhere, the SC will get there a whole lot sooner.


Re the hip boots, I wear suspenders on mine so they won't sag -- I don't trust much of anything I read on the internet, and don't recommend that anyone else should either......... :)
 
My J-3 has a cruise prop, so it takes almost as much runway as a 160 Borer to get off the pavement. But I can usually beat them in landing distance, threshold to full stop. On a nice day with breeze right down the runway of about ten knots, we routinely stop before the 150 foot mark in the J-3, or the VG-equipped Super Cubs with flaps "slightly" more than 50 degrees. Stop and goes Sunday, with that ten knots in the J-3, were total 220 feet. No obstacles on this approach, though.
 
I guess it's the take off in 110 ft less and climb better thing I just don't get. I owned a J3-90 and a 18-150 at the same time and flew them both a lot. The 18-150 would take off in around 110' with no wind light, and the 90 did OK, but it didn't levitate....and the 18-150 would smoke the 3 in climb. This is just my personal experience, they are both great airplanes, take it for what typical innernet BS is worth.....

To give a better answer to drews original question, these are the published performance numbers from Piper for the 18-95 and the 18-150.

PA18-150 @1750 lbs.
Take off run 200 ft.
Rate of climb 960 ft per min.

Pa18-95 @1500 lbs.
Take off run 452 ft. wood prop, 390 ft. metal prop
Rate of climb 624 ft per min. wood prop, 710 ft per min. metal prop.
 
2nd Johnny McMahan 1957 Piper PA-18 58'-6"
that was 2nd place last year with a stock cub so my j-3 should take off in negative 68-6 right?? :D :D

you are wrong mark your 3 does levitate!
 
As an aside, my wife and I are working on our "pilot weight" as we speak. I'm down 60# from my gross, and she is down 20#. By the time we get our next Cub, we want to have a combined weight of around 300#.

I'm starting to get an image in my mind of an "ultra-light" 160 Super Cub and what we could do with it.... I think what I'll do is build a fuselage and then see what kind of deal I can get on an engine.
 
We were getting takeoff runs between 180 to 195 feet with the -18's, and 75 feet with the -3. As I mentioned earlier, time from a standing start to 1000 feet AGL was slightly less than a minute, so the rate of climb is better than 960 fpm (but not by much). Sounds like the O-200 powered -3 will beat the book numbers for the 150hp -18 when they are lightly loaded.

BTW, on another topic, why does Piper use the -18-95 designation for the 90? Piper doesn't allow the 90 to turn 95 on takeoff like some other manufacturer's did. Was it marketing hype?

Bob, I need to take some landing lessons from you. When I'm not using power on the approach, I can't consistently set down right on the threshold, and it makes my landing rollout distances sort of erratic.

JimC
 
One thing I've noted with Super Cubs is tremendous variability in performance from airplane to airplane. There are lots of things that may account for this, but I don't know of another aircraft type that exhibits this much variability in performance.

I suspect that a lot of this difference in performance is in rigging and in engines. For some reason there seems to be a lot of difference in torque in O-320's, and that has a large influence on takeoff performance.

Also, re-pitching these long propellers with thin blades, particularly the Borer prop, is a very imprecise process, and I think that installs a bit of variability as well.

I've flown ostensibly identical Super Cubs, built by the same guys with the same mods and equipment, that exhibited fairly different performance. I also flew an old beater for a long time that was not a particularly light airplane, and it would outperform and outclimb most Cubs.

Go figure.

Nevertheless, if I were even considering two people and a little gear AND especially if you are contemplating any DA takeoffs above a few thousand feet with that weight, I wouldn't even consider anything but the 160 hp Cubs.

MTV
 
Jim: You and I can swap techniques. It is rare for me to get a loaded Super Cub off before the 200' mark. Empty is another question.

On landings, I hook the tailwheel right on that white stripe. We have a well-marked overrun with distances fixed by FAA specifications. Stopping before the first set of white stripes on our instrument runway is by definition a stop within 150'. We do it all the time. We have no obstacles, we are at sea level, it is always 70 degrees here, and it really does require a ten knot breeze. We normally use power, and come across the stripe at stall speed.
 
Bob, when I have no wind, or a steady wind, I can fairly consistently touch down at the threshold. Even so, no wind on grass -- stopping in 195 feet is about the best I can do without adding throttle to keep the tail from lifting as I run out of elevator authority. What gets me though, are those all too common approaches where I am within inches of touching down and I get a gust that lifts me back up a foot or so. And presto, my touchdown point moves another 10 or 20 feet or more down the runway. What's the best way to respond to gusts quickly enough that they don't lift you at the last minute? At idle power I'm really not controlling my touchdown point accurately enough.

Re the 180-195 foot 150hp SC takeoffs, it was light, like the -3 was. The wind that day was pretty steady at about 8 kts right down the strip.

JimC
 
since you are going exp. get a h290 profile grind on your cam and reindex your crank gear this will bring your torque curve to max out at 2500 rpm. and port polish and flow a new set of cylinders along with some 10:1 piston which you can run auto fuel, high test only depending on who you talk to. and thermal barrier all internal engine parts. put that in a light super cub then you got something. dont forget about firewall forwards new cam oiler mod as well.
 
dlg said:
2nd Johnny McMahan 1957 Piper PA-18 58'-6"
that was 2nd place last year with a stock cub so my j-3 should take off in negative 68-6 right?? :D :D

you are wrong mark your 3 does levitate!

Darnit, there you go catching me in a innernet lie. Yes that 3 will levitate and even fly backwards, I've seen it first hand. It did take a little headwind though.... You can take money from 18 pilots with that 3 in a short field contest when light. Great flying Cub, hope it is being used and abused a lot. That 90 will also beat a Oh-200 powered 3 by exactly 111 feet, so you can take their money also. Just in case this innernet BS is true, you might want to tie it down even if it's in a hanger. Hate to see it levitate up to the ceiling and smash the top of the wing ribs.
 
I just couldn't take it anymore, so I had to go get some numbers for Bob and Jim. 1240 lbs. empty - 20gal gas - 190 lb pilot, so roughly 1550 lbs. gross. It was 65 degrees and about a 2mph wind 90 degrees off my right wing so not a factor, 1500 ft MSL.

Take off = 145 ft
Take off - 1000 AGL = 51 seconds
Landing = 250 ft

Never done the T/O - 1000 agl before so I could probably better that.
I'm wearing a spare prop while my performance prop is getting touched up, so I might be able to better T/O a little, I'll see when I get it back.

Next set of numbers will be checked with - 61 gal gas, me, 200 lbs in rear seat, 100 lbs in baggage = 2096 gross and see where I'm at.
Give me 10kts on the nose and I'll suck the fabric right off a J-3 :D
I forgot to ask, were 180 horse Widebody Cubs allowed :wink:

Brad
 
You will sure suck it off of my J-3. Best I have done so far in a heavy Cub, borer/160, full flaps at liftoff, 2 guys 3/4 fuel, was 160 feet, and I think we were hit with a gust, because 200' was a really good number for those conditions. ( 9 kts reported- see my data)
 
Hey, Brad. 'Course a 180 is allowed, and many thanks for the numbers. Both Bob and I are much interested in actual numbers for all cub variants. Your 'light' takeoff is similar to the O-200 J-3 with a similar wind (with a 10 knot wind on the nose, you'd have to get off in less than 70 feet to beat it there -- which you might well be able to do). You're about 5 to 7 seconds faster to 1000 AGL than the J-3, but the -3 pilot was 35 pounds heavier (we've only done that twice, so we probably both oughta practice some before taking those numbers much to heart (what was your field elevation -- we were at 310 MSL). I've no doubt that you'd improve with practice. We'd improve with a lighter pilot.......
Stopping distances were similar (stopping short ain't one of my talents) -- my best was 195 on grass from the threshold with about a 2 knot wind on the nose, typically I manage about 230-250 if I'm trying pretty hard, but am not attempting to slide the tires (I'm for sure not interested enough in maximum stops to risk shearing the stem off an 8.00x4 tube :)

In my dreams, I'd like to try to get about another 25% off the -3's takeoff roll (harder to do than to say.....)

You'd beat the stew out of us at 2000 pounds ---
JimC
 
Thanks Jim, field elev. was 1500 MSL. I've never gone out to get actual numbers before, but it was kinda fun. Had a couple of pilots out checking distances for me and time. My Cub is light in the tail, so it's hard for me to shorten my landing much more. I have Dakota Cub brakes which are great, but I think I could land shorter with a passenger keeping the tail down. I also don't like hanging on the prop and plunking it in, which would be shorter, but I can't see where I'm going or the spot. I prefer wheel landings with a blast of power to arrest the sink just prior to the spot, then to idle with braking and being able to maintain directional control.
That's me though and I always know if I can land there, I can get out of there. I'll see about the 10 kts on the nose and 70 feet sometime (might need some VIAGRA in the gas for that).
I'll get some loaded up numbers for you when I get my prop back.
I'm curious myself now :D

Brad
 
Jim - you are in the back seat? I plunk down in a full stall at the threshold. If I am sloppy, I miss by ten feet or so, but with the ten knots, I can still stop on the white paint. Tires are screeching the whole way, but I keep them at around 25psi to avoid the old stem shear. 8:00x4s with Grove brakes and stock masters. Did it with Hayes brakes just the same.

The Super Cubs with double-puck Clevelands will screech too, but they will lift the tail, which I handle by easing off on the brakes a bit. I never let it get beyond about a foot off the ground. We adjust the Super Cubs for the good side of 50 degrees flaps, which at least lets us carry a bit more power. Touchdown, for me, is always 3-point, power off. Unless I am just playing . . .
 
Brad, glad to get somebody else interested -- welcome to the club. After 42 years in a J-3, I don't much care about visibility out the front......

Bob, I do fly from the back seat. I too, land 3 point at idle power except when playing. I can control the touchdown point closer if I come in slow with a lot of power and plunk it down by chopping the throttle, but that allows me to get away with my somewhat sloppy piloting techniques. I need to practise more on precise, quick, speed and aoa control during gusts. I'm too loosey goosey with that.
JimC
 
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