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TCC NAR Competition Primer: USMRSC Rule 39, Precision Duration Competition (PRD, RDD, STD)

 

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This primer presents, in one place, all the information you need to succeed in NAR model rocket competition in this event.

TCC has provided a link to the official rules whenever we discuss a rule.

 

All Entries

Your entry must:

* Comply with the NAR Model Rocket Safety Code: http://www.nar.org/NARmrsc.html USMRSC 2.2

* Be a model rocket as described by the United States Model Rocket Sporting Code. USMRSC 3.1-3.9

* Use NAR Contest Approved motors:  http://www.nar.org/SandT/NARenglist.shtml USMRSC 4.1, 4.4

* NOT eject its motor casing(s) without a recovery system. USMRSC 9.2

* Have your NAR number or your name on the outside, large and clear enough that the contest officials can easily read it. Teams must use the Team number or name. USMRSC 9.4

* Have been constructed by yourself or by one or more members of your Team. You may not enter Ready-To-Fly rockets (no construction required) in NAR sanctioned competition. USMRSC 9.9

 

Know the rules

Your having a grasp of the bigger picture can increase your enjoyment of NAR competition. You can read the Pink Book Lite to see only the rules for competitors, not for Contest Directors or other contest officials. Read the full USMRSC (Pink Book) to see all the rules.

* Pink Book Lite:  http://ojames3.tripod.com/tccnarcontesttips/USMRSCLight.html

* Full USMRSC:  http://www.nar.org/pinkbook/

 

General Competition Tips:

TCC NAR Competition 101

TCC NAR Competition Strategy and Tactics

Contest Etiquette by Kevin Paul Wickart, NAR 59720, cr 1998, the author

Beginning Competition -- The RSVP Principle by Kevin Paul Wickart, NAR 59720, cr 1998, the author

Guide to NAR Contest Rocketry Information for Beginners by Jeff Vincent, NAR 27910, Northeast Regional Contest Chair

 

Which are the Main USMRSC Rules for This Event?

* The main rules are 9, 15, and 39.

http://www.nar.org/pinkbook/9_Entries.html

http://www.nar.org/pinkbook/15_Timing_Data.html

http://www.nar.org/pinkbook/39_PRD.html

 

What is the Goal?

* The goal of Precision Duration Competition (PRD) is to accurately predict the duration (flight time from first motion on the pad to landing) that a model will attain. USMRSC 39.1

 

Are There Any Special Considerations?

* Precision Duration Competition is divided into three event classes:  USMRSC 39.2

            Predicted Duration (PRD) weighting factor 8 – You will state your target duration before you launch. The minimum duration is 30 seconds. USMRSC 39.2.1

            Set Duration (STD) weighting factor 10 - The Contest Director shall set the target duration when the meet is sanctioned. This value shall appear in the sanction form and all appropriate contest information. The target duration shall be a multiple of 5 seconds between 30 and 120 seconds. All contestants will attempt to achieve the same Set Duration. USMRSC 39.2.2

Random Duration (RDD) weighting factor 8 – The Contest Director will randomly select the target duration just prior to when the event is flown, by draw, dice, or other random device. The target duration shall be a multiple of 5 seconds between 30 and 120 seconds. All contestants will attempt to achieve the same Random Duration. USMRSC 39.2.3

* Your entry must be single stage. USMRSC 39.1

* You MUST make your Predicted Duration flight BEFORE you attempt any other Duration event in the contest. USMRSC 39.3

 

Do I Have to Return My Entry?

* NO. However, the Contest Director can require that you return your entry. USMRSC 9.10

* Multi-Round has different return considerations.

 

How Many Flights Can I Make?

* You can only make one official flight. USMRSC 39.4

 

How is the Competition Scored?

* Short answer: The contestant whose entry comes closest to the target duration (time) is the winner.

* Long answer: The duration your entry actually achieves will be divided by the target duration, and the result multiplied by 100. This figure shall then be rounded to the nearest 0.1%. If the result is greater than or equal to 100, subtract 100 from it; otherwise, subtract it from 100. The contestant whose score comes closest to zero shall be declared the winner.  USMRSC 39.6

 

What Will Disqualify My Entry?

* Your entry will be disqualified if it spins or loops under power. USMRSC 9.3

* Your entry may be disqualified if, in the opinion of the contest officials, it does not comply with the competition rules or is unsafe in operation. USMRSC 11.1, 11.2

 

How About Some Suggestions for New Competitors?

Almost any model rocket kit and contest approved motor will work. Your only motor limits are listed in USMRSC 9.1.

Powered by a single motor containing no more than 62.5 grams of propellant.

Powered by a combination of motors not exceeding 125 grams of propellant in total.

The combined Total Impulse of all motors, in accordance with the Model Rocket Safety Code, shall not exceed 320 Newton-Seconds.

 

Use computer simulations to determine altitude and sink rate for various rocket/motor/parachute combinations.

* Free altitude simulations: 

wRASP - http://www.wrasp.com/

wRASP 32 - http://tccnar.tripod.com/sims/082_wRASP32_221.zip

* Free sink rate simulation:

http://www.onlinetesting.net/cgi-bin/descent3.3.cgi

 

Make multiple timed flights with various models and motors using NAR to determine the duration your model achieves. Add weight, such as tracking powder, and/or use a different motor to reach the altitude that results in the duration you want. Use various recovery systems to determine the durations your model will achieve.

 

Generally speaking, streamer recovery will give you a more repeatable duration than parachute recovery.

 

Consider using one of Art Applewhite’s saucer kits.

 

What Else & What Next?

Using a Designed Experiment to Determine Flight Duration of a Model Rocket, a NAR R&D project by Edward Giugliano NAR 46086 SR, June 25, 1999

http://www.narhams.org/library/rnd/PredictedDuration.pdf

 

Although it’s not as important for this event, you can reduce drag by eliminating the launch lug. Use a tower or piston launcher instead:

Simple Tower: by Bob Supak, NAR 65523

Take 3 1/4" aluminum rods, each about 24" long. Depending on what size model you want to launch, take an 18" piece of same body tube and put a few wraps of tape at each end. Place the 3 rods in a triangle around the body tube and secure with rubber bands, leaving 6" of the ends of the rods exposed. Now place the rods into a coffee can full of wet cement or plaster and let set. Voila - launch tower

 

Complex Tower:

http://www.narhams.org/old/library/zog-43/19-06/launcher.html

 

Piston Launchers Explained – Apogee Components:

http://www.apogeerockets.com/Education/downloads/newsletter47.pdf

 

Floating Head Piston Launcher – The Odd Couple Team T-085, Jeff Vincent NAR 27910 and Chuck Weiss NAR 35775:

http://mysite.verizon.net/wjvincent/RandD/fhp1/fhp1.html

 

TCC NAR Competition Bibliography

http://ojames3.tripod.com/tccnarcontesttips/TCCNARCompArticleBib.html

 

Yahoo group for discussing model rocket competition:

http://groups.yahoo.com/group/contestRoc/messages

 

Use computer simulations to determine altitude and sink rate for various rocket/motor/parachute combinations.

* Free altitude simulations: 

wRASP - http://www.wrasp.com/

wRASP 32 - http://tccnar.tripod.com/sims/082_wRASP32_221.zip

* Free sink rate simulation:

http://www.onlinetesting.net/cgi-bin/descent3.3.cgi

 

US Spacemodeling (International Competition Tips):

http://www.spacemodeling.org/new/how_to/construction.html

 

US Spacemodeling Home Page (International Competition):

http://www.spacemodeling.org/new/home.html

 

Aerospace Specialty Products Streamer and Parachute Tips:

http://www.asp-rocketry.com/model-rocket-tips.cfm

 

George Gassaway’s Competition Tips – Take No Prisoners!

http://tccnar.tripod.com/tcctnp/

 

rmr Frequently Asked Questions – Part 9: Competition and Records:

http://www.ninfinger.org/rockets/rmrfaq.9.html

 

 

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