Saturday, January 22, 2011

Review: Deanston Marauder

This is a ducted, stubby, 24mm-powered rocket that sports replaceable foamcore fins. It flew nicely, but recovery was less than optimal. The name Deanston came from the source of the larger tube--a bottle of single malt scotch.

The rocket used a central BT-60 centered in a larger tube. The larger tube was 3 11/16 OD and 10.375" long. I found that the difference between the BT-60's OD and the outer tube's ID was exactly twice the diameter of BT-50 tubing, so the BT-60 was centered using just that. There were three pieces of BT-50 on the base and another three near the top. The leading edge of the larger tube was outfitted with a short transition to a smaller diameter tube and the forward BT-50 tubes abutted that.

I was thinking that this would resemble some bulbous version of a Mig jet fighter so I procured a ram-jet cone from Semroc.

I began playing around with large fins in RockSim, both for stability and because the outer body was so fat. For a long time, I had been thinking about building a rocket that used replaceable foamboard fins, so that's how I proceeded. I built three plywood frames with the dorsal frame being different from the other two. The attached photo shows some prototype fins installed. The fins were snug, but I added a nylon pop-rivet on each just to be sure they stay in place. Replacing the fins would involve removing the rivet and sliding them out. The new fins would be slid into place and the rivet reinserted.

I made a cockpit section from a chunk of scrap tubing and a clear plastic doohickey provided by Don Brown [Who's Who Page]. The pilot was a piece of a monkey-faced plastic skeleton. (Yeah, it was chopped up before I realized that it could be used as a paratrooper in my Boot Hill rocket.)

The white fins were quickly cut just as a concept and I had bought a piece of black foamcore. However, after several iterations in RockSim, I was convinced that they would make the rocket stable and decided to use them for the maiden flight. The whole idea of the removable fins was to allow multiple designs and not to worry about crunches.

The inner body and most of the cone was painted with Painter's Touch red and the body was painted with Rustoleum flat black. I added a few skull-and-crossbones stickers to complete the pirate marauder theme.

Flight and Recovery:
I loaded up an E18-4 and an 18" nylon chute. The boost was nice but the delay was short. The rocket flew into the chute which stayed there for the duration of the flight. This resulted in a core sample. The cone and replaceable fin frames survived and were recycled.