Modeled by: Stuart Lenz
This design occurred to my while I was cloning some old Estes and Centuri Designs from JimZ site, a forward trust triple ring fin. A next generation, ion powered, solor orbit telescope. I started by cutting 1" from Estes BT 60, BT 80 and LOC 4" tubes for the Ring fins. Next, I assembled the engine mount from the BT 20 engine tube, the engine clip, the 2 centering rings and the Kevlar@ string, with the Kevlar tied around the tube and the upper centering ring slipped over the string. This was then glued into one end of the main body tube, flush with the end of the body tube while the Kevlar string was coiled inside the engine mount. Once the engine mount was dry, the loose end of the Kevlar string was pulled through the body tube and a mark was made on the string even with the end of the body tube. The Kevlar string was then pulled back out though the engine mount and a loop tied into the end of the string so that the mark on the string was at the end of the loop. The elastic shock cord was then attached to this loop and all of this was pulled back though the body tube.
Next I laid out the fins on the balsa, cut out 3 fins and surface mounted then to the body tube. Once they were dry, the BT 60 ring fin was glued into the slots in the balsa fins and this was repeated for the BT 80 ring fin and the 4" ring fin. The launch lugs were attached to one of the balsa fins and the other at the center of gravity (~9.5")
The eye hook was attached to the balsa transition and the remaining parts assembled into the payload and nose code assembly. The loose end of the elastic shock cord was tied to the eye hook and the parachute attached.
The CP/CG stability was verified with a swing test and the model was launch at the MASA January launch in White Bear Minnesota, Good flight.
I have now launchedhe Persius Galactic Explorer 3 times at MASA events. I would probably use plywood for the support fins if/when I build another one. Next, upscale for a 29mm engine mount or Hummm 38mm.