Of the changes, most notably will be the use of polyester resin instead of epoxy for the lay up of the body tubes. I was out of epoxy and had enough polyester resin to finish the job, so that's what I used. The polyester resin is definitely harder to use, it doesn't wet out the fiberglass cloth as well, and is much stickier and harder to work with in general. The polyester resin (when cured) is a little stiffer than epoxy, but also a little more brittle.
I lengthened the lower body tube by one inch, allowing for a slightly longer motor.
I also used a third centering ring at the top of the motor mount tube, the first rocket used only two.
I also added another layer of fiberglass to the fins, so the fins now have two layers tip to tip. I also rounded the leading edge of the fins, the previous rocket had tapered leading edges. I doubt if I'll be able to install a motor that will bring this rocket above mach 1, so rounded leading edges should perform better.
The last change was I made the motor tube slightly larger in diameter. The first rocket was such a tight fit it would compress the air in the tube and eject itself if you pushed it in too quickly. That wasn't really a problem, but I wanted a little extra room for the motors' upper bulkhead retaining pins. That way I wouldn't have to grind them to such close tolerances. So this motor tube is about 2.35" in diameter, .1" larger than the previous. A few wraps of masking tape will bring the motor to a snug fit.
Here is the lower body tube, slotted for the fins and the fin and motor mount package. The fins received a layer of fiberglass cloth at the motor mount tube for reinforcement. That's not shown in this picture but was done prior to assembling the lower body tube.
Here is a look at the lower body tube after the fin fillets were done and sanding started.
Here is the upper bulkhead installed in the lower body tube, it has yet to be epoxied in place. The coupler can be seen to the right, and was epoxied in place at the same time as the bulkhead.
Here is the rocket pretty much done. Once again I used 1/4" wood dowels, drilled into the bulkheads and epoxied in place to help hold in all the bulkheads. The nose cone cracks were epoxied from both inside and out, and should work fine. I'm going to make a removable bulkhead in the nose cone. The bulkhead will hold an electronics package including a transmitter and a sonic beacon.
The body tubes and nose cone were primed, sanded, then spot putty was applied to any low spots and sanded. Then a second coat of primer was applied. That's where I sit now, trying to decide on a finish color.
Here is the repaired nose cone with a bulkhead to allow an electronics package to be installed in the nose.
Here is the nose cone opened up.
Here is the FRS radio installed.
Here is the aft end of the rocket.
Here is the completed rocket, short a motor it's ready to launch. Nice bright yellow paint isn't it? I had the paint on hand so I thought I'd give it a try. I'm sure it'll be easy to find on the ground, I'm just not sure how well it will show up in the sky. Finished weight of the rocket is 6.8 pounds.