I have a J-3 "Ellis" Cub (C-90 12 with 2 18 gallon wing tanks and no fuselage tank) and am looking at giving it some backcountry mods. Any mods that I would do would be function first, rather than just to give it a backcountry look. Would you recommend a climb propeller, or the new 26" Experimental ABW, or maybe something else? Thanks!

J-3 doesn't really need anything to be a very capable backcountry machine just a bunch of 100LL big tires and big props are really just gravy IMHO.

That being said, I am a partner in a PA-11 c-85 stroker with 29" Airstreaks and a climb prop, its probably the most fun airplane I've ever flown. If your going to go with Airstreaks I would go 29", every once and a while I find myself wishing I had bigger tires than the 29s, If they made an ultra light weight 35" I would probably get them. As far as props go, the PA-11 had Metal Sensenich 74/42, and it was a really good prop. Perfect combination of climb and cruise, however I really wanted to get some more pull, so I went with a Wood climb prop. Item 101 on the J-3/PA-11 TCDS is "Propeller- Wood (Fixed or adjustable pitch)", no other guidelines or stipulations, so you really can go with as ridiculous of a prop as you want.

In her natural habitat..

Lots of us BCP'ers also participate on the SC.org site, so you're likely to get the same sort of responses here as you got there. I'd say just add a lot of gas & fly the hell out of that J3. After a while you'll have a pretty good idea what (if anything) you need to change.

If you've got 6" wheels, Desser now makes a lightweight 4-ply 850x6 smoothie. While not a bushwheel, it's big enough for a lot of stuff...and pretty inexpensive at $450 a pair.
http://www.desser.com/aircraft-tires-an ... -4-ply.asp

RKTX didn't say which wooden prop he has, but I've seen some 80" woodies that might be a pretty good fit for STOL op's in a Cub. Pretty inexpensive too.

I agree with the advice that has been given and would add the following. Weight is a huge performance penalty for our high drag / low horsepower airplanes. My dad would always say that the best performance enhancement for a Cub is taking 10 lbs off the pilot! So, less is truly more in the J-3 world.

To me the key question is: where do you gain important capabilities with justifiable weight penalty?

Airstreaks - The off airport benefits are undeniable. Not to mention they turn the fun up to 11! I had 26" tires and upgraded to 29's a few months back. To me the 26" tires are the nicest balance between weight, drag, and off-airport capabilities. If you fly to go somewhere I would stick with 26" tires. For playing in the backyard the 29's are loads of fun and worth a try.

Scott 3200 tailwheel - in my opinion, this was a needed upgrade to keep up with the Airstreaks. On some of the surfaces I was landing my old tailwheel was digging in like a tail hook. The 3200 gives better flotation and beefier construction for the come-what-may.

Prop - I have a Mac 71/44 on a C-85. Not the most aggressive pitch, and I am tempted to go down the "wood prop" rabbit hole left open by the type cert. That will probably be left until after the I rebuild the engine with the O-200 stroker, though.

VGs - I don't have them, and am tempted as they weigh "nothing" and have solid pireps. However, I don't know what my stall speed is currently (doesn't register on the ASI), so I don't know that I can measure the payoff.

Other equipment - I always dress like I am going to need to walk out from wherever I fly. Basic survival gear for the season and Hammer's tiedowns along with fly ties are on board in the event I get caught out. Energy bars and water get refreshed frequently. Otherwise, my mod money goes towards avgas!

To that point, I burned a few gallons to get to this spot this morning:




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VGs were very noticeable on my J3-ish bird and worth the $ in my humble opinion.

I like the T3 tailwheel better, but that is just personal preference (as well as being experimental so I can do whatevertheheckIwant within reason)

Is that Chaparral Alex?

I used to use a J3 for search and rescue flying in the Missssippi Delta, so over the last 50 years, most of my landings have been off field, mostly on sand, some mud. No rock around here, so big tires are not needed since the 8.00x4's are ideal on soft sand. I prefer the small Lang D-501 tailwheel so I can dig it into the sand for braking

With an 85, I prefer the Mac 7438 (not legal, but a good performer on the 85). Running an O-200 now, so prefer the Mac 7440 and the Mac 7535 for climb. Nothing compares with a lighly loaded 55 mph climbout turning 2800 rpm with that 7535. For a cruise/climb compromise, I like the Mac 7142. Top speed level flight wide open throttle with it is 118 mph compared to 110 mph with the 7535. With the 7142, 80-81 mph cruise is at 2250-2350 rpm burning 4.3-4.7 gph of mogas (my O-200 burns 4.3, my buddy's 4.7).

Only change I would make to either the C90 or O-200 J3 would be NFS 9.5:1 pistons (they run fine on 93 octane mogas with alcohol).

I don't care for the wood props because of the roughly 5% loss of thrust horsepower due to their lower efficiency). Haven't found a wood prop yet with decent efficiency. Any suggestions in that regard?

JimC wrote:

I don't care for the wood props because of the roughly 5% loss of thrust horsepower due to their lower efficiency). Haven't found a wood prop yet with decent efficiency. Any suggestions in that regard?

How about a Catto Propeller?



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Be careful to check the TC for engine/prop combinations. The C 90 is approved for 71 inch metal prop. Word prop can be 76.

Less is more on these airplanes. If you want to improve performance, consider removing the electrical system, or at least parts of it.

From your description, I'd guess the airplane is pretty heavy in fact, if not on paper. Losing weight will do more for performance than anything you add.

MTV

I owned a C90-8 powered Cub with a 71/46 Mac and a wing tank It performed very well.
On takeoff it hit the redline which if I recall was 2450 and would cruise at 80 mph at 2200 burning about 4.75 GPH.
Really liked the plane, had it for 10 years. Moved up to a 185 which is a whole different ballgame.

Tom

MTV is spot on.

One of the things I like about the O-200 for the J3 is that the Mac 7440 and 7535 are allowed on that engine (which isn't on the TCDS, so is best mounted by 337). That said, the 7142 also performs quite well on it. Max rpm for the 90 on the J3 is 2475. I usually prop the O-200 to climb at about 2640 at 55 mph. Fuel burn for the O-200 will average 4.3 to 4.7 gph for roughly 80 mph cruise.

Tradecraft, what's the prop map look like for the Catto? Typical range of efficiency at climb speeds?