How to Build a TARC Rocket

Sample

The best advice for someone new to model rocketry is to buy a kit to gain hands-on experience learning how to build and fly rockets. The kit will have detailed instructions, is a great way to see how a basic model rocket is constructed and it will get you out to a launch site so you can begin to network and forge relationships with potential NAR mentors.

We hope that the information below is useful for building a TARC rocket.

The Tool Box

Make sure you have all the right tools before you start building! Here is what’s in our tool box:
Wood glue – to glue fins and launch lugs onto the body tube, to assemble the motor mount
15 minute epoxy – to glue the shock cord to the body tube
5 minute epoxy – for quick repairs in the field
CA glue (super glue) – for quick repairs in the field
1 inch masking tape – to secure the motor
Utility knife
Needle-nose pliers
Ruler
Scissors
Plastic rivets (to hold components together)
Igniters – supply of extra ones
Pencils/Pens
Extra launch lugs
Rubber bands (we use small hair bands) - to secure the igniter and to bundle the shock cord
Motor adaptor (29mm to 24 mm)
Quick Links (¼ inch)
Wire cutter/stripper
Disposable gloves and coffee stir sticks (for the epoxy)


Sample Construction Using the Estes TARC Small Parts Assortment
Consider starting with the Estes Small Parts Assortment. You can build a light weight rocket (350 g) that may meet TARC criteria depending upon the challenge. Make sure you read the TARC rules first!

There are multiple ways to construct the rocket using these parts; here is what we used and why:

Egg Capsule Plastic Nose Cone. Cut this piece to form a nose cone and an altimeter bay.

10 inches of 2.08 inch diameter body tube. This can hold two eggs. It fits between the nose cone and the altimeter bay and can be attached to each with plastic rivets (you will need to drill holes).


8 inches of BT 20 to hold the altimeter. A window must be cut in the tube to allow the pressure sensor to freely be in contact with the air.The tube can be epoxied to the inside wall of the altimeter bay. Small vent holes must be drilled through the wall of the altimeter bay following the manufacturer's instructions for the altimeter.


18 inches of BT 56. Attach fins to one end and friction fit the other end onto the tapered portion of the altimeter bay, which is where the rocket separates at apogee.

12 inches of BT 50. This is the engine mount tube, which is glued inside the BT 56 once the following 4 components are assembled:

1. E Engine Hook. Install a sample motor to determine placement of the hook on the engine mount tube. See photo below.

2. Engine Hook Retainer Ring. The black ring slides over the hook to hold it in place.

3. BT 50 to BT 56 green centering rings. Glue in position to secure the engine mount tube inside the body tube.

4. BT 50 Engine Block. Glue inside the engine mount tube (above the top end of the hook) to prevent the motor from traveling up inside the rocket!

Items we added:

2.08 inch diameter wood bulk head to separate the egg compartment from the altimeter compartment. (In general, the altimeter should be put in its own compartment sealed from hot ejection gases.)
















2--¼ x 1 inch launch lugs to stand-off the first pair (Because of the large shape of the upper section of the rocket, the launch rod does not clear the egg capsule.)

1/8 x 4 x 12 inch balsa sheets for fins. Cut each out with a utility knife such that the grain is parallel with the leading edge of the fin (see section below on making fins).

15 feet of Kevlar shock cord (see section on shock cords below).

24 inches of ¼ inch elastic shock cord. Splice this into the Kevlar shock cord to absorb some shock.


Orange Engine Spacer - if you build for an F motor, you can use the spacer to make an E motor fit.

Plastic rivets to secure the nosecone and the altimeter bay to the body tube

Quick Links (¼ inch) for attaching the parachute

Ripstop nylon parachute

Cellulose wadding - protection against ejection charge

6 inch Nomex square - extra protection!
Fins

It's very important to pay attention to the direction of the grain balsa wood and make sure it is as parallel to the leading edge of the fin as possible. After the fins are glued on, add a thin bead of glue (fillet) to fill in the space between the fin and the body tube.


Choosing Motors
First look at the most current list of TARC approved motors, which is posted in the Files of the TARC Yahoo Group.

Considerations:
24mm versus 29mm diameter. We built for a 24mm diameter motor. You can build for a 29mm diameter and use adaptors for a 24mm motor, but not the other way around.

Single use versus reloadable. Reloads are less expensive than single use, but unless you have someone helping you with experience assembling reloads and you have lots of time at the launch to assemble them, stick with single use. Reloads are designated by an “R” on the TARC Motor List. Our best advice is to comparison shop for total impulse and price per motor.

The photo below shows the length difference between the F and E motors, which can be compensated for by the orange spacers.






Shock Cords and Parachutes

You'll find that everyone has an opinion on shock cords! Lots of ideas about on what they should be made of, how long they should be, and how they should be attached. Kevlar is flame resistant and folds up nicely. Consider using a length of Kevlar that is 3-5 times the length of the rocket.

We use hexagonal parachutes made out of ripstop nylon from RocketChutes who offers lots of different colors at great prices and inexpensive shipping.

Rocket Reviews has a nice tool for calculating the size of the parachute.






Altimeter
You'll need to check with the TARC Handbook for approved altimeters. We chose a PerfectFlight Pnut because of its data storage and retrieval capabilities. Below is a screen shot of the altimeter data you'll receive. The sharp downward spike is typical and shows up when the ejection charge goes off.

This data is from a previous practice flight. We wish we had called it a qualifying launch!



Aerodynamics




We learned a lot about aerodynamics when we modified our fins one year in order to reduce our rocket’s altitude. Our "brakes" were constructed from tongue depressors. We trimmed them with a Dremel until we consistantly reached 750 feet, which was the target altitude for that year's contest.

Tube fins

We've also tried another method to increase aerodynamic drag, which is to add layers of tubes to the surface of the rocket. These decreased the altitude by 20-30 feet.

Rockets of Oz


We were insipired to make theme rockets one year! Here are: Dorothy, Glinda, Tin Man, and Emerald City.