Could you suggest for your Curtiss Jr. any possible configuration or hardware changes before I build?

I plan on using Li-poly batteries...

From : Don Stackhouse

Oh, I guess I'm reasonably familiar with this kit, and can add a few comments...

The kit offers the option of either coupled ailerons + rudder (both on one servo) or just rudder, with extra dihedral. The text for the ailerons version is color-coded red, while the no-ailerons with extra dihedral version's text is blue. Unless you have a specific reason, such as maybe the scale appearance for competition purposes, I'd recommend the no-ailerons, extra dihedral (blue) version. The Roadkill Series models in general tend to carry some of their full-scale counterparts' personality traits to some extent. The full-scale Junior was notorious for having very ineffective ailerons. The ones on the RK Series model do work, but the roll rate is no better than the no-ailerons version with the extra dihedral. Therefore, other than for appearance, the ailerons are just extra weight and complexity.

At the end of Step 16, before you put the main wheels on the axle (so you don't accidentally glue the wheel bearings to the axle!), wick some thin cyano-acrylate into the shrink tube that binds the .032 wire main wheel axle to the aft legs of the .020 wire main gear struts. In a hard landing, it's possible for the .032 wire to turn over in the shrink tubing if it isn't glued, so the wheels angle upwards instead of downwards, resulting in the model sliding to a stop on its belly. Gluing the axle into the shrink tube prevents this.

The wing struts are optional. They look nice and they don't seem to make much difference on performance. In a hard impact, it's not unusual to knock the bottom end of one loose, which a drop of C/A will fix. A piece of dental floss about an inch long across the bottoms of the wing struts will add quite a bit of reinforcement. Just feed the piece halfway through the slot in the fuselage before you glue the wing struts in place, and then glue 1/2" of dental floss to the underside of the strut on each side of the fuselage.

The windshield frame is also easy to knock off in regular handling. A strip of Kevlar thread or dental floss along the front and back legs of it will make it much more durable. Titebond or Elmer's glue works very well for this. The same trick helps on the Curtiss Jenny's wingtip skids and king posts, which also tend to take a beating.

The Junior is very efficient, and I typically get a little more than half an hour of flying time using the stock motor and a 2-cell 250 mah Li-poly pack. I have flown it more-or-less successfully with a 2-cell 700 mah pack, but I don't recommend it, unless you're planning to do a lot of AULD contests with it. I DO recommend using the "Quick-Change Battery Mounting Kit" to mount the battery. It makes it easy to take the battery off for charging, and to switch batteries quickly during a flying session. Loosen two screws a quarter turn each, slip the old battery off, slip the new battery on, snug the screws and go fly some more!

Power is fine for general sport flying including in a moderate breeze. In anything up to about 5-8 knots it should be able to cruise on about 25% to 40% throttle. In my experience, with 10-12 knots of wind it needs more like about 3/4 throttle, which will drop the flight time to a little more than 20 minutes on that battery. It will do hammerheads, wingovers, loops and barrel rolls, although it will generally need to use some altitude to gain speed for each maneuver. It doesn't have enough power with that undercambered airfoil for good inverted performance, so axial rolls are not really an option with the stock power system.

I've tried to make it spin, but the most I've gotten it to do is a spiral, which it flies itself out of as soon as you center the controls.

If you want to do lots of wildly non-scale aerobatics or anticipate having to deal with a lot of wind, consider upgrading to the MPS-2B twin-motor system (there isn't enough fuselage clearance for the bigger prop on the -2A system) and a 3-cell 250 mah battery. Note, you will need to be careful with the throttle on takeoff. The extra power can shove it over on its nose if you give it too much power at the beginning of takeoff roll, before you have enough speed and elevator authority to control that much power.

Taking off from rougher surfaces can also cause this. Bending the main gear struts downwards in the middle to hold the nose up at a higher angle can help. Also, try to open the throttle more gradually, getting it to taxi first, then accelerating into a takeoff. The result looks very scale-like, and still does not take very much room.

The model has a tail skid instead of a tail wheel, but steering on the ground with just rudder works fine.

One other building option is to cover the underside of the wing with something light like Litespan, converting the airfoil to flat-bottomed instead of undercambered. This will help the inverted performance and penetration at the expense of a little bit of low speed performance.

OTOH, if you really want to do wild aerobatics, you might consider one of the other models in the series, like the Triplane or Camel with a -2A and a 3-cell pack. The Junior is very good at being a simple, fun, easy-going powered glider, just like the full-scale one was.

Don Stackhouse
DJ Aerotech