This past weekend I flew my first rack rocket. All four stages sent the rocket heavenly. I have been planning to build one for 3 years….Ever since I read fellow blogger Dick Stafford’s wonderful post on rack rockets back in 2006.
Please read that post for an interesting history and loads of information. I have been studying the designs and wanted a strong rocket with my own design touch. I decided to go with a triangular 3 rail method with added truss for strength. I have read of issues with motors getting caught and sticking so I wanted my system to be simple a strong.
BT-20 – 8 inches
PNC or BNC 20 nose cone
3 – 3/16th hardwood wooden dowels – 10 inches each
1/16th basswood stock for fins (2.5 x 1 inch each)
3 craft sticks for truss
Thrust ring (insert so that about a 1/4 of an inch of sustainer motor is below tube)
kevlar cord (attach kevlar to thrust ring and to shock cord)
Streamer (I used orange construction tape)
First I started with a basic frame of 18mm tube and wood dowels. Tube length was 8 inches.
I reinforced the dowel connections by wrapping thread around them and applying CA. Nothing could break it apart after that.
This is one of my design twist. I used a 3 piece basswood fin design that also acts to create a triangular structure for the rack/rails.
lastly I added additional truss to strengthen the lower rack/rail area from the motors being shot back.
Finished prior to painting.
Flight prep includes laying out the motors and taping them together with Scotch style tape. Insert the connected motors through the rail/rack and so that the sustainer goes into the motor tube up to the thrust ring. I then put masking tape around the rail and tube so that it holds the sustainer in.
The first flight occured on March 21st, 2009 at the monthly R.O.C.C. launch. The launch was flawless and amazingly I recovered the rocket about 50 yards from the pad. I launched it on a C6-0 to B6-0 to B6-0 to C6-7.