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event by event tips:

 

 

 

Set Duration

B Streamer Duration Multi-Round

B Helicopter Duration

C Payload Altitude

D Boost Glide Duration

D Egg Lofting Altitude

Research & Development

Scale

 

 

 

 


C Payload Altitude

 For NARAM-50, the Payload event is for C engine class.

 
Payload Altitude combines the challenge of flying a standard size and weight payload while trying to fly to the highest possible altitude.

The payload needs to be completely enclosed in the model, and remain inside the model from launch to return. Nothing can be permanently attached (i.e. glued) to the payload.

Payload Altitude models can be staged, though this does not seem to be beneficial for B class based on the current choice of engines.

Payload models MUST use a PARACHUTE for recovery. The chute needs only to be large enough for a safe recovery.

For the full rules for this event, please see the Payload Altitude Rules on the NAR web page.

Scoring - For Payload Altitude, the scoring is best SINGLE qualified flight altitude of two flight allowed. The model must be returned on each flight, in order to confirm the payload was not altered or lost any mass.

Design considerations - Designing and building a low-drag model that must hold a one ounce payload that is the same diameter as most body tubes used for 18mm engines, to fly as high as possible

Payload specifications - To quote the Pink Book rules, from 25.2:

"The standard NAR model rocket payload is a non-metallic cylinder containing fine sand, with a mass of no less than 28.0 grams. This cylinder shall be 19.1 +/- 0.5 millimeters in diameter, and 70.0 +/- 10.0 millimeters in length. The payload may be permanently sealed to prevent the loss of the sand. No holes may be drilled into it, no changes made in its shape, and no other material may be affixed to it."


No need to grab any calipers, here's what this effectively means: The payload diameter happens to be about the same external diameter as an Estes BT-20 body tube. Payload models need to have a payload section that is larger in diameter than the payload in order to house the BT-20 diameter payload inside. The payload length can vary from 60mm (2.362") to 80mm (3.15").

NARAM-50 Payload Official Information:

 

Payloads will be available for all contestants, and may be kept afterwards as souvenirs. The provided payloads will be made from standard BT-20 tubing, 2.75 inches (70 mm) long, and weigh 28.2 grams. Contestants may use their own payloads if they choose.

 

 

Scales will be available at check-in for contestants to use to verify the mass of their payload, but pre-flight weigh-ins are not required.

 

ALL payloads will be weighed and measured at returns.

Building and flying this event - There are not many good plans available for this event. Before July 1979, the NAR standard payload was a very short (1/2" long by 19.1mm diameter) lead cylinder. This is why earlier payload designs had short payload sections as they were designed to loft 1/2" lead payloads. Payload is not flown as often today, so there are not many published designs for the longer (sand-containing) payloads. The list of plans is somewhat limited and some of the old lead payload plans would need for the payload sections to be lengthened quite a bit.

Fortunately, ASP and QCR have contest-quality payload rocket kits available, as listed further down this page.

If the old Apogee B7 motors (13mm diameter) were still contest certified, the optimal designs for this event would look much different with the rear half of the models tapering down to 13mm tubing. As staging 13mm A's is not a good choice this narrows the practical options to a single 18mm B engine.

A key to any altitude event is building the model to fly straight and true. Work towards attaching all of the fins so they are straight and parallel to the body. This should translate to a straight boost, with minimal wobbling that would hurt the altitude. A good finish is important for altitude models. Don't overdo it though, it helps to keep the model as light as possible, even though it is carrying a one ounce payload. As weight goes up, peak altitude goes down. Try to focus on light weight designs and not build too heavy.

Sources for 20mm tubes and noses - If you want to build from a plan, or design from scratch (instead of using the ASP or QCR kits), here are sources for the body tubes that slip fit over BT-20 tubes and nose cones to go with them:

  • ASP (Aerospace Specialty Products) - Nose Cone: #BNC20TT  TT - 20 Wood Nose Cone
  • ASP (Aerospace Specialty Products) - Tube: #TT - 20 Telescoping Tube (.745" ID, .785" OD, 30" L, wt 22 gm)
  • BMS (Balsa Machining Service) - Nose Cone: (order a custom made parabolic nose cone to order to match the tube diameter)
  • BMS (Balsa Machining Service) - Tube: #T20Q-34   .787x.748x.039x34 MPC/Quest T20 (this tube is a bit thick and heavy)
  • Apogee Components - Nose Cone:  #19091 Wood Nose Cone 19mm, .765" O.D.
  • Totally Tubular - Tube: #T-20+  (slips-over T-20) 0.770 O.D. x 0.744 I.D (thinner & lighter than BMS' tube)
  • Quest - Tube: #T-20  This tube is not sold separately from their kits, and it is hard to suggest buying a kit just to cannibalize. However, the Quest "Sprint" kit can be modified to be a payload model (see plan/kit list below). The Quest T-20 plastic nose cones are somewhat heavy compared to other nose cones..

Tracking Powder - It is highly recommended to use tracking powder in your model. This produces a small "cloud" at ejection which the tracking crew looks for. Without tracking powder, it is not likely your model will get tracked.

Dry Tempera paint, or a fine powdered Fluorescent Dye, are often used for tracking powder. Some contestants used to rely on powdered chalk, but it is clumpy and does not really produce much of a tracking cloud for the volume/weight of the powder. Red is a good color choice for tracking powder, though some like to use black if there is a high overcast or hazy "white" sky. Fellow competitors are often willing to share tracking powder.

Here's a good way to install tracking powder. After installing wadding, pack the parachute and shock cord into the model, and push them down into the tube to leave room for the tracking powder in the upper part of the tube. Use a piece of wadding or plain paper to make up a long narrow "cup" than will easily slide inside the body tube. Press that cup into the tube, then pour in the tracking powder to fill the cup. About 1" or so depth of powder is a good ballpark. Using tracking powder can require greater forces to expel everything out of the body, which sometimes results in the engine kicking out instead (however, the cup method reduces this problem a bit compared to just dumping powder into the tube). Make sure the engine is secured in the rocket extra-tight. Some people like to attach the fins a bit above the bottom of the body tube so they can apply a "collar" wrap of tape to the bottom of the tube and the engine. This helps prevent the engine from ejecting.


click on thumbnail

 

Above: Example of a tracking powder cloud, having ejected from a model that was stuck in its launcher.

 

 

Engine recommendations for C Payload Altitude:

C6-3 (abnormally heavy or draggy model, like an Alpha with payload section added)

or

C6-5 (typical contest payload models)

or

C6-7 (low drag light contest payload models, pistoned models)

 

 

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Model Plans & Kits

Designer

Notes

ASP - "Versi - Loader 18" payload rocket kit
         #KVL - 18

ASP (Aerospace Specialty Products), Andy Jackson

Good competitive kit for 18mm engines.

QCR - No-Part II kit - Payload A, B, or C

QCR - Qualified Competition Rockets, Ken Brown

Good competitive kit for 18mm engines

AWN-22 C Payloader plan (from NAR website)

Plan by Dave Cook

This record-setting FAI model from 1980 used the old phased-out 1/2" tall lead payload. This design needs its payload section be modified to contain the long paper tube and sand type payloads.

Quest "Sprint" Sport rocket kit
Dealers who carry the Sprint: Red Arrow Hobbies, Ehobbies , Google search listing

Quest Aerospace      

 Tip from Kevin Wickart >>

A sport kit that can be converted for Payload. Cut off about 4" of the forward part of the body tube as a payload section, and add a nose block bulkhead.

ASP - NAR sand payload kit, #PAY - 28

ASP (Aerospace Specialty Products), Andy Jackson

NOT a rocket, this is a sand PAYLOAD in kit form.

 

 

 


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 Last Updated  5/26/2008