Brief:
The Scram Jet along with the Nomad (and the Jayhawk in a lesser sense,) were Centuri Corporation's versions of pseudo-scale missiles. Produced from 1973-80, the original Scram Jet was powered by an 18mm engine. Switching to 13mm power was one of several mods I made in an attempt to clean up the looks of the rocket while sacrificing as little performance as possible.

Construction:

• 15" length BT-20 body tube
• 2 - 5" BT-5 ram tubes
• PNC-20N nose cone
• 13mm engine mount kit
• 3/32" basswood fin stock
• 12" parachute
• 12" Kevlarcord
• 18" sewing elastic
• 3" launch lug
• small screw eye
• small snap swivel

The Scram Jet is a project simple enough to begin and complete over the course of a weekend, starting the build on Friday and flying on Sunday. The original Centuri instructions aren't overly detailed as far as tube lengths and part numbers, but serve well enough in construction. (Keep in mind that the instructions were originally intended as just that; instructions. They weren't intended to supply information to an army of middle aged BAR's almost 20 years after the Centuri Corporation ceased to exist.)

Had I built this according to the instructions, the 15" BT-20 would have been divided into 3" and 12" pieces, but since I was making wholesale changes I decided to go with a single 15" body tube. The instructions also called for 18mm power with the engine hook and hold down strap mounted externally between the ram tubes. I built my first one this way, but hated the way that this marred the otherwise clean look of the rocket. For this version I opted for 13mm power, partly to clean up the external surfaces of the rocket and partly because my original SCREAMED on 18mm power and I felt that it would probably fly almost as well on the mini engines. Not quite. 3/32" basswood was used in place of balsa for both strength and finishing considerations and Elmer's wood glue was used in all phases of constructions. There isn't much more to say. Like I said earlier, this is an easy project.

Finishing:
Thinned Elmer's Fill & Finish was used as a sanding sealer. Since this method has been detailed in countless reviews on EMRR, I'll simply say that the F&F and basswood combine to greatly simplify the process of producing glass smooth, decal ready fins and the F&F makes body tube lines virtually disappear. Cheap thrills in the monkey house. Try it.

Since my first clone was such a great flier before it's untimely demise, I decided that this version would get the paint and decal finish befitting it's performance potential. After primering and sanding, I painted the body gloss white, then followed the paint guide on the instruction sheet for the nose cone. After painting the entire cone silver, I placed the tip of the cone inside a scrap piece of BT-5, then repainted the exposed portion gloss black. I downloaded the decal scan from JimZ and printed a set onto Bel Decal's special inkjet printer decal paper. They turned out great, the best of several that I experimented with in my initial foray into this interesting sidelight of the hobby. After printing, the decals are sprayed with a clear coat and can then be cut out and used like normal waterslide decals from the good old days. They went on easily and turned out great, a perfect finishing touch. Very cool, and the fact that I made them myself makes the whole project ! that much more satisfying.

Construction Rating: 5 out of 5

Flight:
As I noted earlier, my original Scram Jet clone was powered by 18mm engines (and streamer recovered) and while the extra oomph provided by the larger engine made for some impressive flights, the grotesque exposed engine hook and hold down strap took something away from the finished model. Even with an A8-3 on it's first flight, the original flew to an impressive height and at ejection displayed the odd characteristic of flying backwards, allowing the fins to catch the wind and guide it's descent. While cool to watch, this quirk eventually led to the rocket parking itself atop a huge tree on the border of our field on only it's second flight, this time on a B4-4. It was with this in mind that I decided to switch to 13mm engine and parachute recovery for version #2.

Flying on the smaller engines, version #2 wasn't quite the performer that I had hoped it would be. The first flight was on an A3-4T and was obviously underpowered as evidenced by the altitude that it failed to achieve. Low altitude I can live with, but the flight characteristics exhibited on this flight are another story. The rocket wobbled noticeably as it flew, almost to the point of instability. I chalked this up to the poor engine choice and chose an A10-3T for the second flight. Flight #2 was higher, but still wobbled and on recovery blew the nose cone across the field. (Luckily I managed to track it down as with it's paint and decals it adds greatly to the overall look of the rocket.) I figure that the extra weight added by the basswood affected the rocket's stability for the worse. Hopefully this is a condition that a little added nose weight will clear up.

Recovery:
I mounted the shock cord by tying a knotted strand of Kevlar behind the forward centering ring of the engine mount and tying the sewing elastic to the Kevlar. This greatly reduces the chance of shock cord burn through and I've adopted it for use in all of my rockets. I used a vintage Centuri parachute in my clone, but I'd recommend this for use with 13mm engines only. A streamer would seem to be a better choice when using 18mm engines as the rocket tends to achieve prodigious heights and would be likely to drift into adjacent counties on a parachute.

Flight Rating: 2 out of 5

Summary:
While building this rocket for use with 13mm engines cleans up the looks immensely, the performance suffers to the point that I'd recommend building it as an 18mm and friction fitting the engines. This rocket looks great and isn't often seen at launches but truly isn't worth the effort to build for mini engine flying.

Overall Rating: 3 out of 5