Down Scaling a model to a card stock version takes some time.
You pick out a model then do some web searches for the instructions.
This time I went to the JimZ website and loaded the Centuri Instructions #5341
The original Centuri Hornet kit was BT-55 based. It came out at a time when Estes had pretty much absorbed the Centuri line. New Centuri branded kits were using BT tubes instead of the Centuri ST tubing.
The above picture is the Estes reissue. This downscale will display the Centuri logo.
The Estes version has the fins glued flush with the bottom of the tube. Centuri's Hornet had the fins set above the rear.
Semroc also has a Hornet kit but it doesn't have the Hornet (bug) drawing in the decal.
This downscale will be from the original BT-55 to a BT-20 diameter.
To get the Scale Factor, the BT-55 diameter of 1.325" was divided by the BT-20 diameter of .736"
The result was 1.8. Every measurement would be divided by the scale factor of 1.8 to get the smaller downscale sizes.
The online Hornet kit instructions told me the BT-55 tube was #30383. Not much help, I couldn't find the length in any catalog.
The Centuri kit nose cone was #71070 which looked to be a 4 to 1 ogive shape.
Here my preliminary figures:
Centuri HORNET Kit # 5341
Carded Downscale Information
Original Model is BT-55 based at 19.8” tall
Allow ½” off low end for engine mount extension = 19.3” tall with NC
Original Height 19.8” divided / by 1.8 scale factor =
10.72” tall BT-20 based downscale with the nose cone in place.
Semroc Nose Cone BNC-20G4 is closest profile at 3” tall
10.72” overall downscale length - 3.0” tall NC = Downscale BT-20 body tube length of 7.72” long
The other available measurements when divided by 1.8 -
Down Scale Launch Lug is 2.22” from rear of BT-20 tube
Down Scale 1/8” diam. Lug is approx. 1.15” long
Down Scale Trailing edge of fin is .41” from rear of BT-20 tube.
Down Scale Fin Root Edge is 1.25” long.
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