Project: Full-Scale Arcas

Specs:

Length: 90.6 inches

Diameter: 4.6 inches

Weight: approx. 12-15 lbs.

Motor mount: 54mm

Recovery: 72" white nylon mil-spec parachute

Electronics: dual MissileWorks RRC2 altimeters

Background: This project originated from my desire to do a "big" scale rocket. After thumbing through Pete Alway's Rockets of the World, I came upon the Atlantic Research Arcas. This was a tiny sounding rocket used during the 1950s and '60s. Even at full scale, this rocket would be small enough to fly on 54mm motors. In addition, the boat tail and fin detail make the rocket interesting and challenging.

Tubes: I ordered the tubes from Jim Fackert of Totally Tubular, which is the only source I know of for 4.5" tubing. The tubes were wrapped with two layers of 3.2 oz fiberglass cloth, which added substantial strength to the original, thin-walled tubing. However, the thickness of the cloth added to the diameter of the tubes, and the tubes ended up being 4.6" in diameter, just slightly over-scale.

Me, sanding out the tubes	Glassed and gelled on the left, sanded and primered on the right

Nosecone: Obviously none of the regular HPR suppliers make 4.5" diameter nosecones. So I asked Jim Amos of MissileWorks to turn me a custom nose. Since Jim had already made an Arcas nosecone for a previous customer, all he had to do was some slight modifications to the jig to make a slightly larger nosecone at 4.6" diameter. First he made a block of wood out of heart redwood 2x6-es laminated together. This was trimmed into a block approximately 5x5 inches to fit into the lathe. He made several passes using his duplicator, and the nosecone slowly took shape. The finished nosecone was coated with epoxy and sanded smooth. This was repeated until a smooth finish was achieved.

The nosecone as a block.	Jim at work...
Starting to take shape!	Finished.

Fins: The Arcas's complex fins presented a unique engineering challenge. Obviously I can't make them out of aluminum and bolt them to the airframe as in the original. So I decided to enlist the aid of my buddy Steve. I pretty much showed him the plans from RotW and said "Here's the fins; do them any way you want." His idea called for making the internal structure out of 1/16" G-10, to be covered with 1/32" G-10. The finished fins would be covered with ultra-light fiberglass cloth. The boat tail was formed out of heavy paper and laminated with 3.2 oz. fiberglass cloth. The fins were then bolted to the boat-tail. This resulted in a strong, integrated fin/boat-tail unit.

Laying out the fins	Cutting out the skins
Internal structure detail	Two finished fins
Sanded and primered	Glassed

Coming next:

Booster section assembly and fin detailing

Payload/electronics bay construction.

Recovery system installation

Finishing

Estimated date of completion: Spring 2001