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Cuda Video Flights - Feb 19, 2005

Photo by Ron Witherspoon

Gearcam mount on Cuda wing

Flights at the February Birmingham Rocket Boys Launch, at the Phoenix Turf Sod Farm.

A Cuda-Flap model made in 2001 for the FAI S8-P event, for "Precision Landings", was brought out of mothballs (It had been superseded by the Stingray-Flap models Phil Barnes made with Dave O'Bryan in 2002). The Cuda Flap model was flown at the January launch on staged C6's, to see how well it worked out. It was OK, at least C6's are available, but Aerotech may be making the R/C reloads again this year.

To use the Gearcam aboard the Cuda-Flap model, a special mount assembly was made out of 1/32" plywood. It was made to mount the camera looking "up" as seen in glide. A pivoting mirror set up above the lens at nearly 45 degrees to look to the back for boost, and then rotate to nearly 45 degrees forward for glide (Biased to look a bit down). The assembly was made to be temporarily attached to the glider by using vinyl tape at front and the wing bolt at the rear.

The Cuda fuselage was modified a bit to allow for a short pushrod to extend a bit out of the side of the fuselage, so it would retract when the flap was briefly deployed. When it retracted, it would release a thread that holds the mirror looking to the rear, allowing a rubber band to flip the mirror to the front.

I had wanted to use the 9 volt battery to power both the camera and the R/C gear (by using a 7805 regulator). But it turned out that when sharing the same power source, the camera picture was affected very badly any time a servo was moved. So, the model had to fly using its normal 50 mAh Nicad pack for R/c, plus the 9v battery externally.

The battery was 37 grams, camera mount/mirror/wiring assembly 15 grams, and the camera 10 grams. So, 62 more grams for a model that has a 204 gram glide weight with a burned out E6 reload in it (266 gram glide weight with the Gearcam stuff aboard).

At the launch, Ron Witherspoon manned my high-gain 14db receiver antenna assembly for some of the flights. Steward Jones used his own Gearcam receiving equipment, hi-gain antenna, and digital video camera to record some of my Gearcam flights, for others he used his digital video camera to get ground-based footage of the flights. Steward & I made our own versions of hi-gain antenna pointers using 1/2" PVC pipe and PVC fittings, as seen below.

Cuda-Flap model as-built in 2001

Flight #1 was made on staged C6's, with the tower set to 45 degrees (the Cuda-Flap model does not pitch down at liftoff, actually tends to pitch up a bit). It yawed a little bit as it left the tower but otherwise was a good boost that did not require much correction. But it was somewhat underpowered with the 62 extra grams aboard, compared to the non-camera staged C6 flights in January. In transitioning to glide, the elevator trim was off as the model was nose-heavy. I briefly lowered the flap and then adjusted the elevator trim. But it turned out I didn't move the flap far enough to trigger the mirror to flip, so it had a tail view all the way. As it turned out, that was a good thing. It was more interesting to see the V-tail control surface movement during glide than I thought it would be, so on that flight the failure to flip the mirror wasn't a bug, it was a feature.

I was surprised to see how much the inverted V tail rocked in flight, during the boosts of all the flights and even during the glide all the way down on that first flight. Don't know how much of that to attribute to the graphite tailboom twisting and how much to the 1/8" balsa tail surfaces (The tailboom was not the stock Cuda tailboom, it was a lighter spiral-wrapped one). If I put the Gearcam aboard a Stingray, just mount it to look to the rear the whole flight, it might be possible to determine since the Stingrays have the same boom but their composite tails are very stiff structurally and some are attached to the boom in a more direct manner. Also, my Big Bird-3 model suffered some obvious tail flutter on boost in 2003 when it was flown in F Dual Eggloft on two C6's and an E9, with an air-started E9. I might want to put the Gearcam aboard that once, on a gentler G12 (or F13) boost, to document that before I do the planned rebuilding of the tail (would be nice to see how much of that is flexing of the tail and how much is the tailboom twisting/bending).

I had suspected that the staged C6's might be too marginal to fly it at that weight. Fortunately I had some 24mm RC reloads to use for the rest of the day.



Quicktime Movie

Flight #2 was on a D7, and some clay was added underneath the root of the V-tail to move the CG back a bit (never did get the glide CG right though). The D7 took off just fine, D7's and E6's have a greater thrust spike than C6's have. It was a nice boost, just it didn't go as high as a normal D7 boost would due to the weight and the extra drag.

All the reload flights were about 30-40% of the durations they normally would get on those engines (combination of the extra weight and the drag of the camera mount/mirror/9v battery, which reduced the boost altitude and affected the glide).

The mirror rotated on that flight. But it didn't rotate 100%. It looked a bit more down than was intended.


Flight #3 was on an E7 reload (like an E6 but with a shorter burn, at 30 n sec).

Another good boost, and more altitude.

This flight had the best footage of the boost itself. For that reason I made a Quicktime movie of that one at a higher quality and pixel size than for the other movies. It's only about 22 seconds long but shows the boost well. It also shows the tail rocking a bit during the boost.

Quicktime Movie
(1.6 meg)

 Flight #4 was on an E6 reload. Full power, 8 second burn. Shortly after liftoff, the camera cut out for a brief period, either the picture or the signal, so a lot of the E6 boost was lost. The mirror didn't rotate completely at first, but later during the glide it did move some more.


Flight #5 was another E6. Another good boost. Another video drop-out on boost, but not for as long as on flight #4. The last part of the boost, gave it some rudder to make it roll, the model response can be seen as well as the V-tail control surface movement of course. The mirror rotated OK on that flight. The movie clip for flight #5 includes placing the model into the tower and getting it ready for flight, then it was edited to shortly before countdown, to show the whole flight.

Quicktime Movie
(3.2 meg)

One more flight for the day was made, but not aboard the Cuda. The Gearcam was put onto my "VeeT" electric sailplane, and flown up to try to get airborne footage of a rocket taking off.

Climbed up to get into position, turned the electric motor off to glide, and work out the countdown and model position (Steward Jones was watching his monitor and said that the plane was too high up during a first attempt so the countdown was delayed while the glider burned off some altitude). Ron Witherspoon launched his rebuilt "Horizon" on a G64, which provided a nice smoky trail. The camera even caught the sound of the launch.

Quicktime Movie

The results of the Gearcam from the day's flying was pretty good. The mirror method works, but needs some fine tuning. Actually I'm going to try to work out a method to rotate the camera 180 degrees and not use a mirror (Something Steward had suggested but I thought the mirror would be a better way). That would solve the mirror image problems that had to be fixed in iMovie, not just left-right but on boost everything is upside down. Also it can probably be done by putting the camera into a double ended nose cone pod assembly so it would have far less drag, just held 2" or so above the wing by a 1/8" pivot rod or something like that.

Weight can be drastically reduced too. I have gotten some 145 mAh Li-Poly cells. Two cells in series produce 7.4 volts. I can use that to power the Gearcam, adding in a 5V voltage regulator. I can also power the R/C gear on another 2-cell 7.4V pack, using a 5V regulator. The two separate packs (4 total Li-Poly cells) will weigh about the same as a 50 mAh Nicad pack (not including the 5V regulator mass, maybe 2 grams per), so the weight added by the 9v battery will be eliminated. I can remove the flap servo in the fuselage under the wing, to save some mass and allow room to move the receiver from the nose to where the flap servo is currently located. Then add a servo to the nose section, about an inch or so ahead of the wing (the V-tail servos are located side by side right ahead of the wing), for a servo to drive a pushrod to rotate the camera pod assembly 180 degrees. The Li-Poly battery packs would go into the remaining space in the nose, moved around as needed to hopefully get the right glide CG without needing to add tailweight. The model would still weigh more than without the Gearcam, but not nearly so much extra weight and with a lot less extra drag. Actually, if all I wanted was to just get a fixed view of the tail, or view forward, without changing the view in flight, the weight could be just a few grams more since the two Li-Poly packs will almost equal the 50 mAh Nicad pack, and removing the flap servo would almost equal the weight of the Gearcam.


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