Scratch - Mini Classics {Scratch} Original Design / Scratch Built

Contributed by Ted Phipps

Manufacturer: Scratch
(Contributed - by Ted Phipps - 05/20/03)

Here’s a rocket project perfect for a weekend too windy or rainy to fly rockets. All you need is a package of Estes BT-5 tubing and a pack (or two) of PNC-5 nosecones. From these simple beginnings, plus balsa stock and various odds and ends you probably already have around, you can build downscales of the following all-time greats:

Estes Alpha Centuri Groove Tube
Der Red Max
Big Bertha
Cherokee-D
Goblin

Click the image below for full size fin templates (in .JPG format).

Obviously, the plastic nosecones that Estes sells are not perfect scale. In fact, for the Alpha, Goblin, and Der Red Max they’re not even close, so you may want to turn your own from balsa or hardwood. They’re small enough to do fairly quickly.

JimZ’s web site has pictures and plans for each of these rockets, at the following URL’s:

Alpha: http://www.dars.org/jimz/est1225.htm
Big Bertha: http://www.dars.org/jimz/est1948.htm
Cherokee-D: http://www.dars.org/jimz/k-47.htm
Der Red Max: http://www.dars.org/jimz/est0651.htm
Goblin: http://www.dars.org/jimz/k-55.htm
Groove Tube: http://www.dars.org/jimz/ka-11.htm

If you minimize waste when you cut the body tubes, you’ll have extra as well as a Mosquito nosecone left over. You could build another mini-Bertha, set it aside for a Centuri Mach-10 clone, or cut six Mosquito fins, attach them to a 4-inch length of body tube, and you’ve got the Ahnold Schwarzen-Skeeter. The Mosquito fin template is included with the others, just for fun.

Three tables for tube lengths are provided below. The first table shows the original dimensions. The second table shows the true scale lengths (based on table 1), and should be used if you are turning your own nosecones. The third table assumes you are using the standard Estes nosecones, and the tube lengths are adjusted to better match the original proportions. Please note that the Cherokee-D was available in two lengths, so both are listed. Der Red Max was also available as Der Big Red Max, and those dimensions are given as well.

Also in table 2 is a column called ‘% of Full Size.’ This is the scale of the rocket, and is the number that each dimension of the full sized plan was multiplied by. For example, the Big Bertha downscale is 33% as large as the full sized version. This number was found by dividing the diameter of the BT-5 (13.8mm) by the diameter of the larger tube, and rounding off to two decimal places. I used 1/16-inch balsa for all of the fins.

Paint to match the originals, and don’t forget the decals! Tango Papa Decals can do downscaled decal sets for the Goblin, Cherokee-D, and Der Red Max. Believe me, these decals are works of art! Tom Prestia did a page for me that included complete sets for all three. Contact him at:

Tango Papa Decals
1901 Mitman Road
Easton, PA 18040

Phone: 1 – 484 – 767 – TPD1 (8731) from 10am – 7pm EST
You can see the Tango Papa web page here: http://www.tangopapadecals.com/index.html

These little screamers fly great, and give you another reason to buy 1/4A’s or Micro Maxx’s!

Table 1. Original Dimensions.
Name Body
Tube
Length
(inches)
NC (w/o shoulder)
(inches)
Alpha BT-50 7.75 2.75
Big Bertha BT-60 18 2.5
Cherokee-D (1) BT-55 16.2 5.5
Cherokee-D (2) BT-55 18 5.5
Der Red Max BT-60 9.125 6.75
Der Big Red Max BT-60 18 6.75
Goblin BT-55 9 5.125
Groove Tube BT-50 16 4.125
- tube fins BT-50 3.25 ---

Table 2. True Downscale Dimensions (based on table 1).
Name BT-5 Length
(inches)
NC (w/o shoulder)
(inches)
% of Full Size
Alpha 4.2 1.48 .54
Big Bertha 6 .825 .33
Cherokee-D (1) 6.48 2.2 .40
Cherokee-D (2) 7.2 2.2 .40
Der Red Max 3.1 2.2 .33
Der Big Red Max 6 2.2 .33
Goblin 3.6 2.05 .40
Groove Tube 8.6 2.2 .54
- tube fins 1.75 --- ---

Table 3. Downscale Dimensions using Estes PNC-5
Name BT-5 Length
(inches)
NC (w/o shoulder)
(inches)
Shape
Alpha 4.2 no good approximation ---
Big Bertha 6.125 .75 Mosquito
Cherokee-D (1) 6.5 2.125 Quark
Cherokee-D (2) 7.25 2.125 Quark
Der Red Max 3.25 2.125 Quark
Der Big Red Max 6.25 2.125 Quark
Goblin 3.6 2.125 Quark
Groove Tube 8.75 2.125 Quark
- tube fins 1.75 --- ---

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