Rocketry Planet

This Tech Series article covers building a beefed-up EZI-65, capable of use for level 1 and level 2 certification. We're going to start with a LOC/Precision EZI-65 kit and make it level-2 worthy by using stronger building techniques and adding a retro-fitted electronics bay for dual-deployment designed by Darrell Mobley. Join us and build a super-strong rocket and certify in style with advanced high-power construction techniques and recovery electronics!

The things we will add to the standard EZI-65 kit are:

• lengthened motor mount tube

"Save yourself the embarrassment and do it right the first time!"

• extra centering ring
• tubular nylon recovery harnesses
• replacement parachutes
• fiberglassed body tube and fins
• Aero Pack motor retainers
• removable electronics bay for dual deployment

The EZI-65 is a good rocket with which to certify, but building the kit stock is almost a sure way to have a shred. (See the story of my first level 2 attempt.) Save yourself the embarrassment and do it right the first time!

The Electronics Bay

Picture the original EZI, payload section is 12" long, coupler is ~6" long. When installed, the coupler sticks out say 3.5", making total area inside 15.5". Take an additional 5" section of airframe, and another coupler, inserting the coupler 1.5" into the 5" section, leaving 6" inside this aft coupler for the electronics. Depending on the altimeter dimensions, the length needed will dictate the length of the additional airframe section needed or how far the coupler goes into this section.

I added new body tubing, so I lengthened the rocket about 5 inches. Because this was a retrofit, the payload section was built stock. I then took it, drilled a hole to mount a 3" length of 1/2" launch lug in it for an ejection charge holder. I took the eye bolt that was in the payload section, and turned it around, coming in from the other end, so the eye was in the payload tube. On the other end, I used a threaded coupler and screwed it to the eyebolt. To this, I inserted a short length of 1/4 all thread that would go up through the middle of the electronics area and secure the compartment cover. The altimeter mounts to a piece of 1/8" plywood with a 1/4" launch lug epoxied to it which slips over the central threaded rod.

This allows people to retrofit it after the fact, which is important, and it provides extra space in the already small payload area.

Assembling the Parts

What you get with the EZI-65 kit:

When you open your EZI-65 kit, there are some parts you can put straight into your junk box:

• the 10" motor mount tube
• the shock cord mount
• the shock cord
• the parachute

Option 1: If you're planning to build the rocket with the altimeter bay, in addition to what comes with the kit you'll need:

• 5 1/2" airframe tube section for electronics bay (LOC BT-3.90, cut to 5 1/2")
• additional bulkhead assembly (LOC BA-3.90)
• 20" motor mount tube (LOC MMT-2.14, cut to 20")
• extra centering ring (LOC CR-3.90-2.14)
• 1/4" launch lug for altimeter mount (LOC LL-25)
• motor retention system (Aero Pack retainer shown¹)
• launch guide system (Black Sky ProRail mounts shown²)
• parachute harnesses 10' & 20' (tubular nylon shown)
• additional 1/4-20 eyebolt with nut and washers
• 4 quick links
• 2 1/4-20 rod couplers
• 6 1/2" 1/4-20 threaded rod ("All Thread")
• 1/8" plywood altimeter mount (not shown)
• altimeter³ (not shown)
• 2 parachutes (TBD)

Option 2: If you're going to build the rocket without the altimeter bay (using motor ejection), in addition to what comes with the kit you'll need:

• 20" motor mount tube (LOC MMT-2.14, cut to 20")
• extra centering ring (LOC CR-3.90-2.14)
• motor retention system (Aero Pack retainer shown¹)
• launch guide system (Black Sky ProRail mounts shown²)
• parachute harnesses 20' (tubular nylon shown)
• additional 1/4-20 eyebolt with nut and washers
• 2 quick links
• replacement parachute (TBD)

¹ You need some sort of positive motor retention. The Aero Pack retainers are the nicest I've seen for this purpose. You can also use a cheaper system made with T-nuts, bolts and washers.

² I've chosen to use Black Sky Research ProRail mounts for my EZI, but you can use 1/2" launch lugs if you have a rod, or nothing at all if you have a tower. All three rocketry clubs I belong to have ProRails at their launches so this is the most convenient, high-quality solution. If you decide to use the kit's launch lug as a launch lug, you will need to buy another one to make the ejection charge holders (LOC LL-50).

³ I'm going to use the Missile Works RRC² altimeter because of its low price, but of course any reasonably sized unit will work. The Missile Works altimeter is 5.7" long, longer than all other units (except the Transolve T2), so the bay should be able to accommodate any altimeter you choose.

You can buy the rocket parts from Magnum Rockets or directly from LOC/Precision. The motor retainers must be purchased from Aero Pack. Missile Works also only sells its altimeters direct. Tubular nylon can be purchased at well-stocked sporting goods stores (REI has 1/2" tubular nylon in many colors). You can also use tubular Kevlar, sold by Pratt Hobbies (TKL-20).