milleratad

We used to pull banners with Duraplanes, Citabria’s, and a Cutlass model years ago. Only the Citabria was without a tow release. We did learn a few tricks to doing this with models.

First, the tow hitch: This can be as simple as running a pushrod through two pieces of ply (I’ll leave the rest of the build to your imagination) with a space to allow a ring to be secured with the pushrod extended. It’s important to slant the plywood so that when the line is under tension for the banner that it will release and not wedge against horizontal walls. We had a number of problems where the pushrod would retract but the ring would simply get stuck. Our hitches were located at the tail boom with the servo located forward to maintain CG. This meant that the pushrod runs parallel to the tailboom. Another hitch option would be to use a steal rod bent in a “U” shape with the pushrod intersecting the center of the ring, looking like the symbol “ψ”. This is a lower friction mechanism and should be more reliable as long as the ring is shaped correctly to minimize jamming. A paper clip shaped ring with a 45 degree bend half way should do.

Second, the banners: My brothers and I grew up doing real banners and we all fly commercially these days. So, when we were building these banners years ago we wanted to make them as real looking as possible. This was a lot of labor for something that gets beat-up pretty fast. Putting each letter on 8 strings and connecting to a rod between each letter is a little too much work. Taking a sheet or panel of rip-stop nylon is a bit faster and you can paint what you want on it. Any model banner needs several key features to keep it from twirling. A lead-pole with washers or other weights that protrude about 15-20 percent lower then the height of the banner. Caution: this can become a spear if dropped from very high. We attached the tow rope to the banner with 4 lead ropes. These attach to the lead pole at the top, 1/3, 2/3, and bottom of the banner. The leads are brought to a point and attached to the tow rope a little above the center of the banner, again to help keep it from twirling. The final feature is a sock. This is a split panel that keeps the banner from flapping like a flag in the wind. Sizing will depend on the size of your banner and model but the basics are the same. At the end of your banner sow or make a loop with your strings or straps. Attach 2 strips of fabric on either side at the end of the loop with a small space between them to allow the wind to inflate the sock and pass between the two panels.

Lastly, The pickup: A true test of your skill is a banner pickup! It’s hard enough to do a real pickup while seated in a Supper Cub or Citabria, it’s quite another to do this from 20 feet away without perspective. Not only do you have to do precision flying but you have a hook that will swing wildly and exacerbate your every twitch. We used large cutoff treble hooks with lead weight at the end of nylon string (again these can be dangerous). This was very flexible and difficult to control. On one occasion with a Duraplane I was a little unsteady and the hook caught the pole. The pole was well planted in the ground and ripped the plane from the sky. If this would have been anything other then a Duraplane it would have been pretty severely damaged. You might experiment with using real cable or something a little stiffer then nylon string to solve this or just practice a smooth approach. Also, make sure your banner is laid out down wind of you pickup. You should be pealing the banner up. If using a larger panel or billboard type then you can bundle it under the lead pole. If you stretch it out, a sudden pickup can rip it from the vacuum created as it tries to suck it off the ground. This is only a problem with really light material. Also, you can practice the “pull-up” followed by a heavy nose over at the top just as your tow rope gets to the banner. This is the smoothest on the banner and prevents you from stalling the model. If your banner is just too big then you have some altitude to try and release the banner and recover.

Enjoy!