Introducing the XB-4C. The ultimate in walkalong glider contra-rotating propeller technology!

Let the fun begin! Here's the XB-4C early in construction. 

All the pieces are laid out here. Some assembly required :)

 These are the prop hubs and spacers, rolled from standard printer paper. The black strips above are the raw propeller blades, also from standard printer paper.

  here are the twist-tie wire shafts they will turn on. I use scissors to strip most of the plastic off the wire

 The twist-ties are colored black with permanent marker, then scotch-taped to the nacelles.

 I glued the hubs to the blades using Elmer's wood glue. This glue works well because it's thicker and tackier than regular school glue, thus holding items in place better.

 The fins are all ready to go. Note bandsaw cut "grain" direction. Just like wood, these pieces are stiffer along the grain.

 Progress! The blades are bent and separated into clockwise and counter-clockwise groups.

 Of note, these prop hubs are rolled slightly looser than those on the earlier XB-6 to allow easier turning.

 When assembling the propellers, it's important to orient the spacers correctly. The spiral direction of each paper roll must match the rotation direction of the propeller immediately in front of it. Failure to do so makes it much more likely for the prop hub to jam against the bit of paper sticking out at the end of the spiral tube.

 I angled the wire ends up to keep the props and spacers on. Each propeller has its own spacer

 It's done! The XB-4C  will continue the legacy of long range and high performance established by the earlier XB-6 behind it. Of note, both gliders use the exact same wing design, albeit distorted by the camera here.

 Two pieces of solder wire balance this glider. Due to the extra props and their more forward location, I used less noseweight on this plane than the earlier model.

 The fins are larger on this model versus the XB-6 since there are only four to share yaw stability duties

 The interlocking half-slots and finger joints of this design work well enough-I had to tweak the slots later on due to excessively loose fit.

 Black never goes out of style. The 16-inch span and generous 3.5" root chord give the model plenty of wing area and good lift/drag ratio given all those propellers

The mighty contra-rotating propellers are ready to propel...er, drag, this model into battle!

And here it is, on its primary mission of entertaining kids and kids-at-heart at Discovery World Museum, Milwaukee, Wisconsin.

Multiple missions are sometimes needed to accomplish the objective. People don't always notice these planes on their first fly-bys!