What is the EZ-DD Rocket/Altimeter Package?
We created the EZ-DD to fill what we think is a hole in the hobby rocketry market. Over the years, we’ve had a lot of people ask us what altimeter to buy (of course…), along with “which rocket” and all of the other bits that they need to complete their first dual-deploy rocket. Almost every dual-deploy rocket is unique… so that’s a really hard question to answer. What we felt was needed was an easy way for hobbyists who have successfully flown larger model rocket motors (F-G) and smaller HPR motors (H-I) to get into dual deployments while building on the building and launching skills that they have already learned. This will also help them advance in their journey to HPR Level 2 or Level 3.
What is different about the EZ-DD from other dual-deploy rockets?
The EZ-DD is a 100% complete package. For $100, you get the rocket including the dual-deploy AV bay with ALL hardware and wiring, and a specially-designed dual-deploy altimeter. It includes the parachute, too. (Only a main parachute… the apogee deployment is drogueless, which is fine for a rocket of this size and weight). Other rockets that are “dual-deploy capable” generally do not include all of the hardware that you need, don’t include the altimeter, and also don’t include wiring or the small specialized bits like terminal blocks and charge wells. All of this is included in the EZ-DD package… you will not need to go hunting around for them. The only things we don’t include are the expendables: a 9V battery (see below), your motor, and some recovery wadding. You will also need to get ematches and some kind of pyrotechnic powder for the deployments…more on that below.
How hard is it to build the rocket?
If you have built any “builder’s kit” type rockets, i.e any rockets with separate fins and centering rings/motor mount, you shouldn’t have any trouble with the EZ-DD rocket. It’s a very straightforward design, based on the Balsa Machining Service 3” School Rocket kit. There is no cutting or drilling necessary… all of the parts are laser-cut and laser-drilled. You can build it with either a good quality wood glue or a hardware-store quality 5-minute epoxy such as Bob Smith or Devcon. (All of our prototypes were built with Bob Smith 5-minute epoxy).
How hard is it to build the altimeter?
The EZ-DD altimeter uses almost all through-hole construction, if you have any soldering experience at all you shouldn’t have any trouble with it. We even include the solder. All you need is a small soldering iron (12W-15W) or a temperature-controlled soldering station, and the usual soldering supplies… a brass mesh “sponge” and a tip cleaner block. We also recommend using a lighted magnifier, although there are no itty-bitty surface mount parts it does make things easier. If you take your time and follow the illustrated instructions you won’t have any problems.
What are the specs for the EZ-DD rocket?
The EZ-DD rocket is 3” in diameter, and about 40” long. Built but without motor, it weighs about 24 oz. It’s designed for 29mm motors, in the upper-F to lower-I range. We recommend using motors with an average impulse of 40-200 N-s, and a total impulse of 60-400 N. There are a LOT of motors to choose from within this range.
How high can I expect it to go?
It’s going to depend on your motor, of course, but you can expect about 750’ with a large F such as an Aerotech F50, about 1700’ with a G such as an Aerotech G80, 2700′ with a motor like an Aerotech H135W, and nearly 5,000′ with a big motor such as an Aerotech I205W. Your altitude will depend on a lot of things, of course… your launch site ASL altitude, temperature, wind, etc. The Aerotech “EconoMax” G74 motor is an ideal “first flight” motor… you can expect around 900’-1100’ from it. Note that we did not design the EZ-DD to be a mach-busting screamer… it’s for learning how to properly and safely do dual-deployments. Save the crazy stuff for your next build.
Can I buy just the EZ-DD Altimeter, or just the EZ-DD Rocket?
We are currently not selling them separately. They were designed together as a system… for example, the pre-drilled holes in the EZ-DD sled match the hole pattern for the EZ-DD altimeter, and the pre-drilled holes in the main parachute payload bay and coupler match the position of the push button on the altimeter.
If I break something can I get replacement parts if I crash my rocket?
Yes, we will offer replacement parts, for the components that we had custom designed. If you damage something that’s part of the bottom half (the standard BMS 3” School Rocket kit), we’ll refer you to BMS since they stock those parts.
What kind of tubing do you use?
The airframe components are supplied to us by Balsa Machining Services (balsamachining.com), in fact the bottom half of the rocket and the nose cone are BMS’ standard 3” School Rocket it. We worked with them on the design of the AV bay and the main parachute tube. The tubing is .035” thick… about the same as on the Estes PS II kits.
What settings are used on the altimeter?
The EZ-DD altimeter fires the drogue charge at nose-over, which is one second past your detected apogee. The main charge fires at 600’ AGL. These are the most popular settings based on 12 years of selling dual-deployment altimeters… and they work fine for just about any flight. There is no provision for changing them… simplicity is the keyword here, and not having to touch anything is as simple as it gets.
What kind of battery does the EZ-DD altimeter use?
We designed it to be used with a 9V alkaline battery, we strongly recommend that you get one with a type “6LR61” designation. Those batteries are made with six AAA cells welded together, and compared to 9V batteries built with six stacked rectangular cells can put out more current and are more shock resistant. You can also use a 9V Energizer Ultimate Lithium battery or a 2S/7.4V Lipo battery, however those are more expensive and you will have to get a charger in the case of the Lipo battery. We’ve tried to make the cost of entry as low as possible.
What ematches and pyrotechnics do I need for the deployments?
Just about any standard ematch will work fine, we’ve tested with a number of them and had no problems at all. If we had to pick one by name, we’d recommend the MJG FireWire ematches, they’re readily available and highly reliable, plus they do not require any special shipping fees (other ematches may require special hazmat shipping).
For the pyrotechnics, the industry standard is FFFFG black powder, such as that made by Goex (which is now owned by Estes). You can get it at a local gun shop, or from a rocketry vendor at a local launch. Most rocket motors also use this, so you can simply use the vial of powder that came with your motor (since you don’t need it in the motor anymore), or for CTI motors you can remove it from the forward “cap” and save it. You will need about 1 to 1.5 grams per charge well… that fills the charge well up about ¾ of the way, after you’ve inserted the ematch head (see the instructions for the EZ-DD flight preparations).
You can also use black powder substitutes such as Hodgdon Triple Seven FFFG, we’ve been using it for several years with great success. It’s a little different than black powder, we recommend that you fill the charge wells completely, and tightly contain the powder with several “X’s” of masking tape over the top of the charge well plus one full wrap around the perimeter. It is also available at gun shops and large outdoor retailers such as Bass Pro Shop and Cabelas.
Will it work with the Eggtimer Telemetry System?
Yes, the EZ-DD altimeter is fully compatible with the Eggtimer Telemetry System. It transmits data similar to the Eggtimer Quark… real-time altitude, deployment channel status, apogee, and velocity.