The PML Explorer is available with a 29 or 38 mm motor mount. The kit used for this review has a 38 mm motor mount. This version was selected as it allows for the greatest selection of motors to be used with this rocket. This was the first high power rocket kit I built and was also to be used for a Level 1 certification flight. This certainly added to the excitement of building the PML Explorer. This HPR kit is pretty easy to build. Some experience in working with epoxy is probably a good thing before attempting this kit. Other than that, there's nothing too difficult in building this kit. The Explorer was selected in part due to the advice of a friend. For certification flights you're not looking for too much altitude as that tends to translate to a landing further from the pad/rail. Keeping it close should make recovery easier.

Parts List

This PML rocket kit includes the items listed below. The kit comes in a clear plastic bag, there is no face card.

- nose cone
- pre-slotted Quantum tubing airframe
- phenolic motor tube
- 2 plywood centering rings
- 3 G10 fiberglass fins
- piston ejection kit
- shock cord
- 30" parachute
- 2 brass launch lugs (1/4")
- decal
- instructions

To build this high power rocket, you'll need epoxy, sandpaper in various grit, a pencil and painting supplies.

Construction

One of the centering rings has a gap in it, this is the forward centering ring. Start by attaching it to the motor mount tube and don't get any epoxy in the gap. Next, epoxy the shock cord to the motor mount. The supplied shock cord was replaced with a 15' tubular Kevlar one.

Slide the aft centering ring onto the motor mount tube, but do not glue it in place. Epoxy the motor mount assembly into the Quantum tubing airframe. Once the epoxy is fully cured, remove the aft centering ring. The instructions said to put tape strips on the ring and use that to pull it out. I used a small kitchen knife instead. You can slide a knife through the fin slots and gently push out the aft centering ring.

Each fin will have three epoxy fillets. One where the fins and the motor mount meet, the other on the inside of the airframe and the fins. The final fillet is where the fins meet the outside of the airframe. The internal fillets can be a little tricky. With a 66mm (2.6") airframe and a 38mm motor mount tube, there isn't much room to play with. For the external fillets, some colloidal silica (West Systems) was mixed with the epoxy for added strength.

At this point, the piston would usually be assembled. At the advice of an experienced high power rocketeer, I went with a Kevlar heat sheet and a 15' long Kevlar shock cord instead.

There nose cone's eyelets were not used to attach the shock cord. Instead, an eye bolt was epoxied into the nose cone and a quick-link used to attach the cord to the nose cone.

The launch lugs were also not used, they were replaced with rail buttons. Brass inserts were epoxied into the airframe tube to hold the rail button screws. One button was place by the aft centering ring, the other at the CG location (before primer and paint). To add positive motor retention, a 38mm Aero Pack motor retainer was added. It was attached using JB Weld to withstand the heat of the motor.

Finishing

The primer used was gray automotive primer (Rust-Oleum). The nose cone was painted Rust-Oleum black enamel spray and the airframe gloss orange.

Measurements

The Explorer has a 2.6" diameter and is 48" height. The weight listed in the PML spec sheet is 32 oz.

Flight Data

Public Missiles, Ltd. recommends a wide selection of single use and mostly reload rocket engines for use with this rocket : F50T, G38BM, G40W, G80T, H55W, H70W, G75J, H128W, H238T, H97J, H180W, H220T, I200W, G54W, G104T, G64W, H73J, H123W, H242T, H112J, I161W, I357T, I154J, I195J. For Explorer kits that are built "top-notch", an I211W or I300T rocket engine can also be used.

The first flight was on a H128W. The rocket shot straight up and all looked fine, until it hit a couple of hundred feet... The nose cone popped out and the parachute deployed (very) early. The ejection charge could be heard a few seconds later, this was not a motor failure. Turns out this high power rocket needed a vent hole. Don't remember seeing anything about this in the PML instructions and never having flown a high power rocket before, I didn't know about the need for a pressure relief hole. Video : Explorer - Failed Level 1 on H128 (PG13 For Language)

To make matters worse, it landed on a road and suffered some road rash on one of the fins. Nothing that can't be fixed quickly and nothing that would keep it from flying again without immediate repairs. Merely some cosmetic damage. While the prefect played with the idea of considering this flight a successful level 1 certification flight, we opted to try it again that same day. I didn't want to certify on a flight like this.

After drilling a vent hole, it was launched again on an H128W and went straight up without any trouble. Lots of white flame and noise, just like the first launch. It look a long time to find the rocket, it drifted quite a bit farther than I thought. The high visibility gloss orange didn't help either. Finally saw the parachute in some high grass. Missed a road by only a few feet. No damage at all this flight. This was a successful level 1 certification flight.

The Explorer has since been flown on an H165R which is also a great motor for this rocket, if you want to keep it low.