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S8E-P Cuda-based Variants

Ryan's Cuda-Ray

Cuda-Flap by George Gassaway

For the 2001 US Team Flyoffs, I needed to come up with a model with some type of glide path control, for the S8E-P event. The 2002 WSMC would be the first time that the "Precision Landing" (or Precision Crash) version of S8E would be held. The new version of the event was a 6 minute target time, with every second over or under 6 minutes deducted. Also, a 50 meter long "runway tape" on the ground. Landing within 1/2 meter of the runway line, 100 points. 1/2 to 1 meter, 50 points. 1 to 5 meters, 25 points.

After considering various ways to go, I decided on a model with one big flap. It was not possible to do this with the original Stingray models due to the curved dihedral in the wigs. So, I decided to start with a Cuda wing and tail planform.

 

 

 

 

The wing layup was modified in several ways. It had to be reinforced to make it strong enough for a 14" span (7" half-span) by 7/8" chord Flap to be cut out of it after the wing was completed. This required, for each wingskin, adding some .005" graphite strip in place of the normal fiberglass "spar", and some fiberglass cloth for the last 2" of the wing chord (to Trailing Edge), from Root out past the Trihedral joint. Also, a solid balsa spar insert, laid up during the skinning and bagging process, to give solid support where the hinge line would be cut later. For more info on how the Cuda-Flap wing was prepared, go to the Wing Assembly Page.

To increase the span a bit, the tip was not trimmed diagonally as for a normal Cuda. It was left square, then a 1" wide tip block was carved, rough shaped, and glued to the tip. Then sanded to final shape.

 

The fuselage was totally redone. Even the original boom was replaced by a lighter graphite boom (Avia G-Force). I wanted to have a "High Wing" mount for the wing, so the flap would not be likely to ever hit the ground in a bad landing. So the fuselage would be a built-up balsa teardrop, much as I had built for R/C B/G's and R/G's before. I thought about whether to put the engine pod on a pylon up front, or put it under the wing as I had done for Big-Bird-3. I decided to put the engine under the wing. It made for some challenging construction to do it that way, and have everything strong enough and for the blind nut for the wing bolt to not rip out easily. It did all work out, but I would not recommend that engine mount method unless the fuselage was somewhat taller than I had used.


Balsa fuselage before pinching nose to glue front bulkhead
 
Top View

Completed, with Flap Servo

The Cuda-Flap model worked out nicely. The Flap was very effective. It required a few flights to work out the correct amount of down elevator compensation so that the model did not balloon up and stall when the flap came down, or dive from too much over-compensation.

The Flap deployed nearly 90 degrees. That was so much as to make it act like an airbrake. I could put the model into a 30 degree dive with little increase in airspeed, and it could even dive into the ground at 30 degrees without damage. It also could dive more steeply than that, I sometimes dived it at 45 degrees, though it did increase the airspeed a bit, but still nothing like would happen with flaps only deployed at 45 degrees or so. One drawback was with so much drag, when I leveled it out for landing to try to do a final steering correction for the runway tape line, there was very little "hang time" before it would stall and land. In theory I could have been adjusting the throttle stick to vary the flap angle, but I found that it was more practical to go with either all down or retracted. For the flyoffs, the model itself worked well. I made a mistake on one flight and let it land off the end of the runway, caught by the wind. Came in 4th. But months later, George Riebesehl, who had won using a normal Stingray (no flap, no spoiler, no 3rd channel), dropped off the team and I moved up.

For the 2002 WSMC, the S8EP Team members used Stingray-Flap models, so I had no pressing use for flying the old Cuda-Flap models. In 2004, when I got a BoosterVision onboard video camera, that changed. I modified one of the Cudas to carry the BoosterVision camera. Eventually, adding a camera pod that rotated 180 degrees after triggered by the flap servo, so it could look aft for boost, and look forward for glide. For more info see the Airborne Video Pages.

Cuda Ray by Ryan Woebkenberg

Ryan built a flapped model for the very same reason. The S8E-P event, for the 2001 US Team Flyoffs. Ryan also chose to use a Cuda wing, but to modify it. For the fuselage, Ryan chose to use a "Stingray" type of layout. To mount the servos inside of the wings, like a Stingray. And to mount the receiver and battery pack in a pod attached to the front end of the graphite fuselage. As with the Stingray, the wing was permanently glued to the boom. Unlike the Stingray, there are no removable wing panels, so the model has to be transported fully assembled.

The Stingray Kits used a molded pod, made of fiberglass, or Kevlar, or even Kevlar/Graphite. Ryan simply used a piece of 24mm tubing, making it long enough not only to hold the engine, but also to hold the receiver and battery (Kevin McKiou's prototype Stingray was made the same way). Running the wiring for inside the graphite boom, thru the pylon.

For the wing, Ryan chose to just make it as a simple "Vee" dihedral. With a flap on each side of the wing. He simply used one servo with a "Y" yoke to allow that one servo to move both flaps equally.

His model flies well and is a reliable performer.

Ryan flying Cuda Ray

at NARAM-50


Flap Down

Flap Down

Yellow Runway Tape