Jeff's Rocketry Postal Contest Entry

August 2011 -- NAR A Streamer Duration

Jeff with one of his Super Sprints.

August 2011 -- NAR A Streamer Duration

This month's event was A Streamer Duration (SD.) I have been in a postal slump this summer -- missing a couple of contests for various reasons. But I really wanted to get back into it and this was an event that I had some models that I wanted to fly.

I actually had two sets of models. First, I wanted to try the 25mm paper models that I built in the spring. Second, I had some older, more-conventional, 13mm A SD models laying around.

The paper models were the ones I built for 1/4A PD. The paper bodies, light 1/32" balsa fins and light Kevlar shock cord were all a questions mark for A SD, but the only way to find out for sure would be to fly them. I equipped the models with a 5x50" 1 mil mylar streamer from my FAI S6A models and carefully checked the CG-CP relationship (with the heavier A3-4T motor in the tail.) A rod launcher (versus a piston or tower) was used to minimize stress on the model.

I chose to fly them Friday, August 26, a few days before tropical storm Irene hit. The weather was beautiful with sunshine, temps in the upper 70s, and little wind. I set the model up on the 1/8" rod launcher, was ready to fly, and took a photo. I then noted a slight breeze and decided to move the launcher a hundred yards or so to take better advantage of the field I was in. At ignition the model moved about an inch and stopped, lifting the launcher enough to topple over on its side.

I had used a masking tape flag to keep the model above the blast deflector. The lower launch lug, on the straight part of the body, was about two inches above the fins. When I had first set up the model to fly, I had been careful to make sure that the masking tape was between the fins and would not interfere with the model. But, when I moved the launcher, I did not re-check the postition of the model and it must have rotated enough to align a fin with the tape flag. An unofficial flight, a wasted motor, and a damaged model (ejection damage that burned through the paper body) were the price for this little lesson. :)

I set up a second paper model identically, but I used a smaller piece of tape that could not foul the fins. The launch and boost were perfect, but right around burnout the model shredded -- it lost two fins and the nose and streamer were ejected prematurely. Duration of 21 seconds, but a DQ for separation.

So I picked up the wreckage and headed home, not the best day on the range.

(Click on an image to view a larger version)

The model ready for flight on the rod launcher.

Note masking tape flag. After moving the launcher to a better launch area, the model apparently rotated enough to catch its fin on the tape on ascent and failed to leave the launcher.

The second model on the launcher (with a much smaller piece of masking tape to hold it up.)

The results of flight two -- two fins shredding at burnout and a premature deployment summarizied by this (posed) post-flight shot.

We had tropical storm Irene pass through that weekend, not something we usually experience in upstate New York. In Albany we got about five inches of rain and 50 mph winds, but some nearby areas saw more than double the precipitation, so many waterways and low-lying areas experienced major, if not historical, flooding. (And, unfortunately, after week of drying out, the Schoharie valley to the west of us got another five inches of rain, and many of the same people experienced flood damage a second time.) :(

After the storm, the last few days of the month were nice weather, but soggy ground. I ended up deciding to make a single A SD flight with my 13mm model just to get something qualified and entered.

This model is relatively conventional. The motor mount is a 2" piece of BT-5. The main body tube is a single layer of paper, which slip-fits over the BT-5 and is taped in place. The nose is an old CMR NC-50P (to better fit the slightly-oversized paper tube.) Fins are airfoiled, unfinished balsa. The streamer was a 4x40" 1 mil mylar streamer. The model is rod launched.

There was a moderate wind on on Tuesday, August 30, so I tried to select my launch area for optimal recovery. I flew from a paved area in my local park (so at least half the flight operations would be dry. :)

The model boosted well and deployed perfectly, but the wind was stronger than expected. The model ended up drifting about 1700 feet. Luckily it landed on one of the soccer fields in the park and was easily recovered. (Ironically, it pretty much followed the path of the FAI S6A model that was lost there in the spring, but was able to carry over the brush this time.) The flight time was 79 seconds. Not a great time, but respectable considering the circumstances.

The 13mm model sits on the rod launcher.

Recovery! - the end of a successful flight.

Future postal contests include:

September 2011NAR Set Duration - 50 seconds

See Rocketry_Postal_Contests Yahoo Group for more details.

Back to Jeff's Rocketry Postal Contests page


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