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Greg’s Tubular Crayon

The Tubular Crayon is based on the Crayon Bank that was on sale at Toys R Us for $5.99. Our club is having a Tube Fin Delight event in September 2005.  So I decided to try tube fins instead of the usual clear fins.

 

The crayon is 35 inches long and 4 inches in diameter. The total length of the rocket is 36 including the retainer. The body tube uses one crayon and the six tube fins are made from two extra crayons. The tube fins are 4.25 inches long and are offset three inches from the bottom. The offset is to have the fins on the stiff tube instead of the plastic base. The tube fins are bolted to the body tube and bolted to each other with #8 hardware.

The tube fins are very well secured with the screws and nuts. I used no epoxy on them. I sawed off the excess length of the screws on the tube fins.

The motor tube is 54mm with a Slimline retainer. There are three CRs. The chute will be a Rocketman R7C in a deployment bag.

Through some approximation with rocksim I believe a conservative estimate of the CP is 24.5 in from the nose or just aft of the R on the body tube. Therefore the CG will need to be at least 20.5 or forward of the Y on the body tube.

To get the CG forward am adding weight to the nose. I sunk some 1/4 inch all thread into 2 oz of plumbers epoxy clay at the tip of the nose. The all thread extends through a bulkhead I slipped into the nose. I have weights that will thread onto the all thread. I expect to use one pound of weight in the nose. The chute and deployment bag weigh 3/4 pound so it helps with the CG somewhat. The weight of the rocket about 4.5 lbs without the motor.

I have chosen a H242 for the first flight. I will need to adjust the delay to 7 seconds. I will use a 54/38mm adapter. The expected altitude is 1000 feet.

I consider this a “Funny Car” version of the crayon rocket. We will see how the flight at the September 10th SEARS launch turns out.

I launched the Tubular Crayon at the Southeast Alabama Rocketry Society September 10th Launch. The motor was a H242. I modified the delay from a medium to a short. Which was a good match.

Flight Pics Slideshow:


Thanks,

Greg

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