Like many fiberglass rocket kits, the Darkstar Extreme has an aluminum-tipped nose cone. The aluminum tip is for more than just show: it has a couple of structural purposes.

One is the manufacturing method of the nose cone itself. The process uses “filament wound fiberglass,” which involves placing resin-impregnated fibers around a mandrel (a gently tapered cylinder). It is difficult to make this come to a point, and instead the manufacturer just shortens the nose cone and puts an aluminum tip on.

Another purpose is that during flight, the tip of the nose cone absorbs the most heat, and aluminum is a better material to use for this specific part of the rocket.

So, the question for me now is: how to connect the nose cone to the rest of the airframe?

You might be asking: how hard can that be? And you’d be right; it isn’t particularly difficult. But some nose cones have a portion that can fit inside the rocket body, as though there’s a built-in coupler. This nose cone, though, is the same diameter as the rocket body and will not fit inside it.

The good news is, the rocket comes with a 6 inch long coupler. Half goes inside the nose cone, half inside the airframe (payload section). On the nose cone side, I just epoxied them together to create a permanent bond. On the other side, I drilled three small holes through the airframe (and coupler) and inserted nylon screws (shear pins). This allows everything to stay together until a large force is applied mid-flight and the airframe separates from the nose cone, deploying a parachute.

The bad news, however, is that I need to attach a kevlar cord to the nose cone somehow, and the best way to do this is to put a bulk plate with a forged eye bolt on one side of the coupler. Either side will do, but it makes sense to put it on the side that goes a few inches into the nose cone, rather than the side that comes a few inches out, since that increases the available storage space inside the rocket for things like the parachute and 25 feet of kevlar cord.

The kit came with a fiberglass bulk plate with no edge or lip (see above picture). It will fit inside the coupler, but I don’t feel too confident that epoxy alone will hold it in place. Instead, I ordered another aluminum bulk plate with an edge or lip – the inner part fits inside the coupler, but there is an outer lip that sits above the coupler so it cannot be pulled through, no matter how hard the cord is yanked.

I epoxied the aluminum bulk plate to the coupler, and then used more epoxy to attach the forged eye bolt (with a long screw attached) and two nuts to the bulk plate itself. There’s no way this setup is coming loose during flight regardless of the forced applied.

Above is a view of the inside of the coupler. I added some masking tape in an attempt to create a very crude barrier or dam, keeping the additional epoxy a bit closer to the edges to seal them.

That’s it! The coupler and nose cone are in good shape, and I’m ready to move on to the next section: my old friend, the e-bay.

With the airframe of the rocket nearly complete, I just needed to prep the area where fins will eventually go. The rocket is pre-slotted (i.e., it comes with slots already punched out to insert the edge of the fins), but the slots are all too narrow and needed to be sanded quite a bit to widen them.

In addition, I drilled 12 individual holes (one for each side of all 6 fins). Later in this assembly, I’m going to insert the fins into these slots, where their edges will be up against the motor mount tube inside this airframe. I’ll then inject epoxy with a syringe into each hole, and tilt the rocket back and forth to spread it around, ensuring that the fins are strongly secured in place both internally and externally. But I’m getting ahead of myself.

On to the motor mount tube!

This 75mm fiberglass tube has a slightly smaller diameter than the 4″ rocket airframe. (To be clear, I have no idea why the motor mount tubes are almost universally measured in metric units – 54mm, 75mm, and 98 mm being fairly common in high power rocketry – while the airframe itself is measured in inches. It’s a mystery for the ages.)

There are 4 beige colored fiberglass centering rings: the inner diameter of each ring fits snugly around the motor mount, and the outer diameter of each ring fits inside the larger airframe. The purpose of these rings, as the name implies, is to center the motor mount inside the airframe.

The primary goal here is to secure the yellow kevlar recovery harness to the motor mount. Later, I’ll attach a much longer kevlar cord to this one, and the other end of that cord will attach to one end of the e-bay (with a parachute attached as well).

This basically makes sure that the bottom part of the rocket, including the motor, stays linked to the e-bay in the middle of the rocket – and also makes sure that a parachute can deploy, when these parts separate after apogee. Since there’s nothing obvious to hook or attach this cord to on the motor mount, the solution is to simply epoxy it directly to the motor mount.

I measured the width of the cord (1 inch) and marked it on the top centering ring, and then sanded down a 1 inch width on both sides of the inner part of the ring, to allow just enough space for the cord to fit between the ring and the fiberglass tube. About 6 inches of cord are on each side of the tube.

After that, I created some very crude “dams” with masking tape since the epoxy is a bit runny before it cures. I put a generous amount of epoxy underneath the cord to bond it to the tube, and then even more on top of the cord, in order to totally encapsulate it.

Here you can see a “before” and “after” picture. I couldn’t quite get all the masking tape off afterwards because some was sealed and bonded (somehow I did not foresee this). But the cord is totally encapsulated. When the epoxy cures, it becomes incredibly hard and is similar to plastic.

The recovery harness here is now thoroughly secured to the motor mount.

A few notes on epoxy, as this was my first time ever using it. It’s pretty straightforward, but there’s a slight learning curve. I used West System 105 resin and 205 hardener: these are two separate products that come in separate containers with pumps. You add them together (in a ratio of one pump each) into a mixing cup, and then mix them together (I used a popsicle stick) very thoroughly, for several minutes.

Once mixed, the epoxy begins to harden and cure much faster than I initially realized. It also gets very hot, from the chemical reaction – to the point where it’s literally giving off visible steam, and the heat from touching the outside of the plastic mixing cup will burn your fingers.

It’s also a bit runny when spreading, so it really helps to create a barrier or dam with masking tape to keep the epoxy where you want it, as it cures. The tape can easily be removed later.

I was previously used to working with wood glue for cardboard rocket sections and plywood fins, but fiberglass is a whole new experience. Wherever fiberglass pieces need to be permanently attached (e.g., the fins to the rocket body), this two-part epoxy is used, and it’s amazingly strong.

Next up: the nosecone.