Mach Diamond. Baffle Shock Cord Pod model

[BABAR]

[video=youtube;1axaqpc2gOg]https://www.youtube.com/watch?v=1axaqpc2gOg&feature=youtu.be[/video]

Yeah, I know, just 4 fins and a nose cone, but for some reason I can't seem to get the fins on right.

Couple of different things about this bird.

Flight Profile was interesting. I was expecting a certain amount of corkscrewing (previous experiments with Asymmetric Fin Designs have shown pronounced corkscrewing although the flight TRAJECTORY is straight, so "corkscrewing" should not IMO be considered an UNSTABLE flight characteristic-- these I think are great sport flyers.) In this case, however, had a relatively straight flight with minimal if any corkscrewing (or rolling) around the longitudinal axis UNTIL the propellant charge (thrust) burned out and the delay charge (coast) starting burning, at which point it did start corkscrewing (which was a good time to start the roll, as it gave a cool helical smoke trail.) Perhaps some of the more aerodynamically brain endowed TRFers could chime in with a reason for this.

Second thing is the baffle/shock cord mount"pod" I built into this bird, which I will outline in the next post.

 

[BABAR]

I have been having a problem with my Kevlar shock cord mounts, which I have been attaching to my thrust rings. Even though it is Kevlar, it has been burning through in just a few flights. I don't like the trifold mounts, as I don't like anything that interrupts the smooth internal surface of the rocket and therefore can snag the cords and laundry.

For the Mach Diamond and the Devil's Triangle I have created a "tube-within-a-tube". I use three 1/2 moon (actually just a bit wider than 1/2) balsa plates (each is 2 pieces of 1/8" balsa, each cut in opposite/orthogonal grain directions, then laminated and coated with wood glue on the aft/firey end), inserted into a tube which just barely fits into the outer diameter. Basically I just cut a big out of a BT-20 so it slides into place. The shock cord is wrapped around the inner tube and then threaded through a hole to the inside the inner tube.

The laminated and covered plates are allowed to dry, then inserted into the pod tube.
Cord is wrapped around the front of the pod tube and a needle is used to pass it to the interior.
Entire pod is then inserted from the front of the main rocket body tube, and the nose cone is used to push it in just far enough to clear the nose cone shoulder.

It cuts down a bit on the internal space for the parachute, but given I need no wadding and the tube interior is smooth, so far I am two for two on successful deployments, with no shock cord or chute burns.