In my case, I'm going to modify it so it takes a larger motor - in this case, an E-sized motor.
|A selection of motors. The second and third from the left are standard 18mm motors, the size that normally go|
into this kit. The one on the far right is the 24mm E motor which will go in this rocket when it's done.
The standard motor for most kits of this size is 18mm in diameter and 2.75 inches long. An E is 24mm in diameter and 3.75 inches long. The rocket body is about 1.33 inch in diameter, just big enough to accommodate the larger motor size and still have a little space on the sides.
This going back and forth between metric measurements and English measurements may seem confusing, but it's pretty common in American rocketry. Everything would be easier if it were all metric, I know, but most kits are sold with parts in fractions of inches. Motor diameter, however, is almost always stated in millimeters.
Edit: It has been pointed out to me that what I'm doing here is not, technically, regarded as kitbashing. This is one of those things you won't really find in a dictionary, but depending on whom you ask, a kitbash can be simply modifying the model to perform differently than intended by the manufacturer (this is the definition you'll find on Urban Dictionary). But in model rocketry, kit bashing (it can be one word or two) is generally regarded as taking the parts of one kit and modifying them so that the result is a rocket which looks like a different, existing kit (the Wikipedia definition).
Regardless, I want you to see how you can modify a kit to suit your needs, and that modification can be major or minor.
Part 1 - Parts, and Assembling the Motor Mount
The fins have fin tabs on them. If you look at the aft body tube, it has slots in the base. This rocket has what's known as through-the-wall or TTW fins. They go through the wall of the airframe and are glued directly to the motor tube inside. You find this a lot in larger rockets, and it adds strength to the connection between the airframe and the fins - they're not likely to snap off on landing if they're TTW fins.
The blue motor tube will be set aside and saved for another rocket. I'll replace that with a larger diameter tube. Because of this, of course, I'll need to trim those tabs on the fins - they're long enough to reach that narrower tube that comes with the kit, but too long if you have a wider tube inside - they'd stick outside the rocket!
From the bag of stuff, I'll only use the parachute, shock cord and decals. The centering rings and motor hook are for a smaller motor, so I'll save those for something else.
|A closer look at the fins|
|The new motor mount parts|
When I built the Quest Quadrunner, this came in handy - it was missing two thrust rings! These go inside the motor tube to keep the motors from shooting out the top of the rocket! Fortunately, I'd purchased a twenty-pack of BT-20 thrust rings from JonRocket.com.
|The blue rings came with the kit - but I needed four! The brown rings came from JonRocket.com.|
Thankfully, many things in model rocketry are of a standard size.
I needed to cut the BT-50 to size - 3.75 inches long. When cutting a tube, it's a good idea to have something sturdy inside to support it, so you get a cleaner cut. I have a 4-inch long BT-50 coupler, so I slipped that inside.
Tube couplers are quite useful things. Not only can they be used to join tubes to make longer rockets and support tubes as you cut them, I have used them to join scrap tube to rockets while painting them, to avoid getting overspray inside the tube. This turned out to be really important when building my two-stage rockets, because you join those temporarily together for flight - again, with a tube coupler - and having paint or primer inside makes the stages stick together. You can buy an assortment of tube couplers - and centering rings, tubes - all kinds of parts - on websites like JonRocket.com and balsamachining.com - another well-reputed rocketry supplier (but one I haven't used myself as yet). I like having a box of spare parts - then I can fix something, or spontaneously take on a project like this one.
|One of the few Estes accessories I really like - the tube cutting guide. These come in a number of standard tube sizes, and they go onto the tube and lock in place. They help you cut tubes cleanly, or mark a line around the circumference.|
|The cut has been made - not perfect, but much cleaner than I'd have gotten doing it freehand.|
I need to get better at this, I admit...
Because of this, I always use the blank side for cutting, and the side that says "Estes" and the BT-number for tracing lines around the tube.
Next, I mark a line for the motor hook to be inserted, 1/4 inch from the end. Since the tube and motor are both 3.75 inches long, this means the motor will overhang the rocket by 1/4 inch. You use your hobby knife to cut a tiny slot there to insert the motor hook, just like we did in Part 3 of the Skill Level 1 series, Building the Big Bertha.
|Thrust ring - again, from JonRocket.|
In many Estes kits, as in the Big Bertha, there is a Mylar ring which holds the hook in place. If you look at the fin tabs above, you'll see they have a little indentation to accommodate that Mylar ring.
Since I'm using my own tube, I don't have a ring of that size. But tape works quite well - and it's thinner, so I don't need to worry about cutting an indentation into the fin tabs when I trim those down.
Put a ring of glue just inside the end of the tube where the hook was inserted, and place the ring inside. Press it down on a piece of wax paper on the table or cutting mat - this will make sure it goes in straight and evenly, and the wax paper prevents your getting glue on your work surface.
To make up for that, and to add strength and make sure I got the motor tube well centered, I added a third ring. With a longer motor mount like this, and such narrow rings, it's probably not a bad idea. It's very common in high power rocketry - it adds strength to the whole mounting system. So I did it here.
This kit will take me a while. I'm also starting my first mid power rocket - the Quest Big Dog. And I have a few longer, technical posts I'm working at for this blog. So this project won't be completed on this blog for a little bit. But I'll keep you updated, and of course I'll share the launch video with you!
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