RC Rocket Glider
I have three flights on it now, and it is awesome that I can launch a rocket and then glide it back to the launch site rather than go chase it down after drifting in the wind under parachute.
Being the engineer that I am, I can’t just build something without “improvements.” Not wanting to land on my servos, I put them on top of the wing instead of on the bottom. The main modification, in this case, I included provisions for including an 18mm rocket motor for inflight air start.
The auxiliary motor mount for air start can be seen in the top photo above. It is the smaller diameter tube below the main motor mount tube. To ignite the motor, I need a 2S LiPo battery to get enough voltage for the igniter, rather than just a 1S that is recommended. I also need a battery eliminator circuit (BEC) to provide 5 volts for the receiver. To command the airstart ignition, I will have an electronic switch (not pictured).
To accommodate these four items, I fashioned a tray from foamboard with velcro on one side (second photo). The tray slides into the rocket body tube and rests on the motor mount at the bottom. The tray makes it easy to adjust the center of gravity by moving the battery up and down.
I haven’t yet tried the airstart option because I am just getting used to flying it stock.
The receiver is an Admiral gyro receiver from MotionRC. I have used these with success in other airplanes, and thought that it could be useful for minimizing any wild pitch rate coming off the launcher or when trying the air start. The first flight, I had the roll rate also controlled by the gyro. However, there were some wild roll oscillations during boost, so I turned off the roll gain for the second and third flights, which worked well. The boost was quite straight without having to do any trimming!
The depron foam wings are fairly flexible, even with the carbon fiber stiffeners that came installed. Thinking that some wing flex may have been aggravating the roll oscillations, I covered the wings top and bottom with packing tape. They are somewhat stiffer now, and we will see how it works. The ready-to-fly weight, as pictured without the switch and without the motor is 11.5 oz.
On his web site, Frank provides instructions for building a launch tower. Rather than ordering the rail that he uses, I got some 6′ aluminum 3/4 inch on a side and 1/16 inch thick rails from a local home improvement store. Using that plus some scrap 2x4s, Gorilla Glue, and miscellaneous hardware, I built the launch pad pictured.
I did use Franks suggestion for a radio controlled remote ignition system. I use the bind button on my Spektrum DX9 for ignition, and a three position switch for flight modes for safety, launch, and, glide.
When I try the airstart, I will need to use a wired ignition system on the ground, and use the RC system in the air.
I hope to get some video. If my wife can’t come out, I will try my “hat cam,” which is a GoPro on the bill of my hat.
I may try flying with the gyro off to see what happens. Also, I want to see if the wing stiffening with packing tape improves the flight characteristics at all. Ultimately, of course, I will try the airstart.