Brief:
This is the PML two-stage Thunder & Lightning kit. It comes with the CPR3000 electronics bay and the interstage coupler to house the timer.

Construction:

• Quantum tubing airframes – one for the booster and three for the sustainer. The fin can sections came pre-slotted.
• Three sets of piston systems
• Two 38mm mmt tubes
• The parts for the interstage coupler
• The parts for the CPR3000 system
• Numerous centering rings
• Two sets of fins
• Recovery harnesses for both sections
• Parachutes for both sections

I began construction of the sustainer first following the enclosed instructions. The motor mount assembly and installation of the fins are straightforward following the booklet instructions.

The next section was not as difficult as I’d thought it might be – constructing the CPR3000 housing. The altimeter tube is fiberglass so scuff that up well with 60 grit sandpaper for better adhesion of the epoxy. There is also the aluminum coupler and threaded sleeve that require roughing up. Just pay extra attention when making the hole for the switch that it’s on the same side as the slot.

The construction of the booster is also relatively straightforward in building the motor mount and attaching the fins. If you plan to use a commercially made motor retainer such as PML’s Hammer, or another similar retainer, leave 3/8” of the mmt sticking out of the boat tail. I did leave this bit showing for eventually adding such a retainer.

There are three piston assemblies to be made all being begun with the assembly of the booster mmt and the top and bottom CPR sections. I would recommend using the straps attached to the mmt and CPR sections as part of the recovery system.

The last section to be built was the inter-stage coupler for the timer. It also is a straightforward build of a central tube centered inside the coupler with a piece of airframe around its middle.

A problem I encountered as I built the inter-stage coupler was realizing there were two coupler cr’s to be used. I mistakenly used one with the lower end of the CPR unit thinking an error in parts had been made but just gluing in the small coupler that goes between the sustainer payload sections when the CPR unit is screwed together.

Finishing:
Being a high power rocket kit, it doesn't come with decals so choice of finishing is up to the builder. I opted to go for a 'flame' look at the bottom of the booster and painted the rest of the rocket dark red with black fins and nose cone.

Construction Rating: 4 out of 5

Flight:
First attempt at flying as a two-stage on a Pro38 I287SS to a Pro38 H125 didn’t go too well. The sustainer motor didn’t light, but due to the dual deploy electronics, the rocket survived and the attempt will be made again some day.

Recovery:
Recovery went as planned due to the electronics working as they should to deploy the parachutes.

Flight Rating: 4 out of 5

Summary:
Pros are good quality parts and very detailed instructions for build and prep.

Cons are that the sustainer can only be flown dual deploy as the CPR3000 unit is part of the rocket and cannot be used in other rockets. I would not use this system in a scratch-build as I like the option of using the same avionics bay in various rockets.

Overall Rating: 4 out of 5

Other:
Modifications I made were to cut and use longer wires for the switches and to swap out the included lugs for rail buttons.