April 03, 2005

Building a simple but unusual rocket

Iím going to show you how to turn an ordinary badminton birdie into a real launchable rocket. These are easy to make and bigtime fun to fly, plus they don't go so high that you'll lose it.

Best of all, they fly on Estes "mini" motors. You can find these in the toy department at WalMart, and a pack of four will cost around five bucks. You're going to need one to help you construct the rocket, so pick up a pack before you start. Look for motors labeled A10-3T or A3-4T, they'll be a little less than 3" long and about one half inch in diameter (pinky sized).

If you need more information about rocketry, check out my Rocketry archives, there's lots there, plus links to even more.

I'm going to assume that you have a launch pad and controller. The ones that come with Estes or Quest starter kits work fine. Starter sets are cheap, include everything you need and the value is very good.

And finally, just to prove I'm not a complete loon, here's the original plans for the birdie rocket as it originally appeared as an Estes rocket kit.

(in the extended entry)


Click on the pictures for Saturn V size
.

tools and materials

Tools
Scissors
X-acto knife or razor blade
Pencil
Circle template Ė I used an empty spice jar

Materials
Badminton Birdie (aka shuttlecock)
Thin cardboard (from a cereal box or soda 12-pack is perfect)
Cardboard tube (Estes BT-5, or make your own)
Soda straw
Yellow or white glue
Hot melt glue

Instructions

Motor Mount Tube
The only real complicated step is right up front, and that's only if you have to make your own motor mount tube. I'll explain how, and then suggest a couple of super easy alternatives.

Cut a strip of thin cardboard (manilla file folder is ideal) 2.75" wide and about 4 or 5 inches long. Pre-curl it by running it over the edge of a table. Wrap it around one of the mini-motors, it should wrap two or three times. On the last wrap, squirt a little glue under the layer and use the rubber bands to hold things together while the glue dries. Be careful not to glue the motor inside the tube permanently, it has to be able to slide out. What you'll wind up with is a cardboard tube 2.75" long. Let it dry.

That's the hard way (and it's not all that hard to do). There are some easier ways to do it though. First off, you can buy that size tube from hobby shops and cut it to length, but a package contains 3 18" lengths, which is seriously oversupply for what you need (unless you're making a lot of these). If you go this route, look for Estes BT-5.

You can also buy a rocket kit and salvage the parts from it. Current Estes kits that use BT-5's are the Mosquito, Quark, and Swift. There are probably others, look for a rocket kit that uses the mini-motors (A10-3T, A3-4T, etc. - look for the "T" at the end of the motor designation).

Centering Ring
birdie2sm.jpg

Using a template (I used a small empty jar), mark a circle on the cardboard. See the picture farther down to judge about how big a circle you need. Take your motor mount tube and use it to mark another circle centered inside the first.

birdie3sm.jpg

Carefully cut out the inner circle with the X-acto knife, and then cut out the outer circle using scissors or the knife. Be careful, that knife is sharp! Take your time and make multiple light passes instead of trying to cut through the cardboard in one stroke.

Save that inner circle. We're going to use it in a moment.

Assemble the motor mount
Glue that inner circle into the very top of the motor mount. This makes a bulkhead that protects the birdie from the ejection charge of the motor.

When that has dried a bit, fit the centering ring into the bottom of the birdie and then slide the motor tube into place until the top end (with the bulkhead) touches the front of the birdie. Glue the motor tube to the centering ring with a bead of glue where they meet. Remove the centering ring from the birdie and do both sides of the centering ring/motor tube joint. Let it dry.

birdie5sm.jpg

Aligning the launch lug
Next you need to place a hole in the centering ring that the launch rod will go through when it's on the pad. Line it up by using the rod and either punch the hole with a hole punch or drill it with the x-acto blade. If it looks like the rod won't pass through the cardboard and birdie smoothly (important!), take a short length of soda straw and glue it into place as a conduit for the rod to pass through.

birdie4sm.jpg

Gluing it together
Run a bead of hot melt glue around the perimeter of the cardboard ring where it meets the birdie to join the two pieces together. That's it!

Launch Instructions
Put a motor into the motor tube and insert the igniter normally. Slide the rocket onto the pad by passing the launch rod through the straw or holes you made for that. Hook up the igniter to the controller wires, count down and launch.

When the ejection charge goes off, it will eject the motor out the back of the tube, which lightens the birdie enough to recover safely via drag or "featherweight" recovery.

To fly it again, just insert another motor and you're good to go.

Why it works
A badminton birdie stays stable because the rubber nose is heavily weighted compared to the rest of the body and the many holes (feathers) create enormous amounts of drag. These two factors combines keep the birdie flying nose first, but it also decelerates quickly when the thrust ends (either by striking with the racquet or by our rocket engine).

On recovery, the extreme amount of surface area compared to the light weight combine to keep the speeds low. It's the same principle as a whiffle ball, no matter how hard you throw it, the area/mass ratio means it'll slow almost instantly.

Posted by Ted at 10:31 AM | Comments (2) | TrackBack

Building a simple but unusual rocket

Iím going to show you how to turn an ordinary badminton birdie into a real launchable rocket. These are easy to make and bigtime fun to fly, plus they don't go so high that you'll lose it.

Best of all, they fly on Estes "mini" motors. You can find these in the toy department at WalMart, and a pack of four will cost around five bucks. You're going to need one to help you construct the rocket, so pick up a pack before you start. Look for motors labeled A10-3T or A3-4T, they'll be a little less than 3" long and about one half inch in diameter (pinky sized).

If you need more information about rocketry, check out my Rocketry archives, there's lots there, plus links to even more.

I'm going to assume that you have a launch pad and controller. The ones that come with Estes or Quest starter kits work fine. Starter sets are cheap, include everything you need and the value is very good.

And finally, just to prove I'm not a complete loon, here's the original plans for the birdie rocket as it originally appeared as an Estes rocket kit.

(in the extended entry)


Click on the pictures for Saturn V size
.

tools and materials

Tools
Scissors
X-acto knife or razor blade
Pencil
Circle template Ė I used an empty spice jar

Materials
Badminton Birdie (aka shuttlecock)
Thin cardboard (from a cereal box or soda 12-pack is perfect)
Cardboard tube (Estes BT-5, or make your own)
Soda straw
Yellow or white glue
Hot melt glue

Instructions

Motor Mount Tube
The only real complicated step is right up front, and that's only if you have to make your own motor mount tube. I'll explain how, and then suggest a couple of super easy alternatives.

Cut a strip of thin cardboard (manilla file folder is ideal) 2.75" wide and about 4 or 5 inches long. Pre-curl it by running it over the edge of a table. Wrap it around one of the mini-motors, it should wrap two or three times. On the last wrap, squirt a little glue under the layer and use the rubber bands to hold things together while the glue dries. Be careful not to glue the motor inside the tube permanently, it has to be able to slide out. What you'll wind up with is a cardboard tube 2.75" long. Let it dry.

That's the hard way (and it's not all that hard to do). There are some easier ways to do it though. First off, you can buy that size tube from hobby shops and cut it to length, but a package contains 3 18" lengths, which is seriously oversupply for what you need (unless you're making a lot of these). If you go this route, look for Estes BT-5.

You can also buy a rocket kit and salvage the parts from it. Current Estes kits that use BT-5's are the Mosquito, Quark, and Swift. There are probably others, look for a rocket kit that uses the mini-motors (A10-3T, A3-4T, etc. - look for the "T" at the end of the motor designation).

Centering Ring
birdie2sm.jpg

Using a template (I used a small empty jar), mark a circle on the cardboard. See the picture farther down to judge about how big a circle you need. Take your motor mount tube and use it to mark another circle centered inside the first.

birdie3sm.jpg

Carefully cut out the inner circle with the X-acto knife, and then cut out the outer circle using scissors or the knife. Be careful, that knife is sharp! Take your time and make multiple light passes instead of trying to cut through the cardboard in one stroke.

Save that inner circle. We're going to use it in a moment.

Assemble the motor mount
Glue that inner circle into the very top of the motor mount. This makes a bulkhead that protects the birdie from the ejection charge of the motor.

When that has dried a bit, fit the centering ring into the bottom of the birdie and then slide the motor tube into place until the top end (with the bulkhead) touches the front of the birdie. Glue the motor tube to the centering ring with a bead of glue where they meet. Remove the centering ring from the birdie and do both sides of the centering ring/motor tube joint. Let it dry.

birdie5sm.jpg

Aligning the launch lug
Next you need to place a hole in the centering ring that the launch rod will go through when it's on the pad. Line it up by using the rod and either punch the hole with a hole punch or drill it with the x-acto blade. If it looks like the rod won't pass through the cardboard and birdie smoothly (important!), take a short length of soda straw and glue it into place as a conduit for the rod to pass through.

birdie4sm.jpg

Gluing it together
Run a bead of hot melt glue around the perimeter of the cardboard ring where it meets the birdie to join the two pieces together. That's it!

Launch Instructions
Put a motor into the motor tube and insert the igniter normally. Slide the rocket onto the pad by passing the launch rod through the straw or holes you made for that. Hook up the igniter to the controller wires, count down and launch.

When the ejection charge goes off, it will eject the motor out the back of the tube, which lightens the birdie enough to recover safely via drag or "featherweight" recovery.

To fly it again, just insert another motor and you're good to go.

Why it works
A badminton birdie stays stable because the rubber nose is heavily weighted compared to the rest of the body and the many holes (feathers) create enormous amounts of drag. These two factors combines keep the birdie flying nose first, but it also decelerates quickly when the thrust ends (either by striking with the racquet or by our rocket engine).

On recovery, the extreme amount of surface area compared to the light weight combine to keep the speeds low. It's the same principle as a whiffle ball, no matter how hard you throw it, the area/mass ratio means it'll slow almost instantly.

Posted by Ted at 10:31 AM | Comments (2) | TrackBack

February 27, 2005

Box Hockey - Part 4 (final)

Here's the final part of our series to build your own box hockey game. If you have any questions, feel free to leave 'em in the comments and I'll answer them as soon as I can.

Previous Box Hockey posts are linked to from here.

(in the extended entry)

Finishing touches

Ok, in the first three parts we built the main part of the box hockey table, and all that's left is a few little finishing details and some rules to play.

Using the leftover scrap hardboard, cut out two paddles and six triangles. Sand the edges lightly to smooth them out.

box hockey plans4.JPG

The paddles are what you use to hit the checker puck with. The triangles are a later addition because sometimes the puck slid directly into a goal, often hitting the back wall and then popping back out. When the puck is moving fast enough, it's hard to tell if a goal was scored or not, so the triangles deflect the moving puck and prevent arguments. Use white glue or hot glue to fasten them into place against the back wall behind each goal slot.

box hockey plans5.JPG

Use a yardstick or tape measure to figure out the center line of the board, and mark it with a sharpie or other permanent marker.

That's it! If you want, you can flip the board over and mark or paint a checkerboard onto the bottom, we usually add a simple backgammon board too.

Box Hockey rules

These are all suggestions based on what works for us. House rules are common, and on the playground it's not unusual for the winner to call special rules for the next game. The terms puck and checker are used interchangably.

The two side goals (bigger) are worth 1 point each, the middle, smaller goal is 3 points. The puck doesn't have to completely go through the slot for it to be a goal. We score the point if it breaks the plane of the back of the slot (slide the paddle along the back of the slot board, and if the checker moves, then scoooooore!

Game ends when one player scores 11 or 15 or 21 (decide at the start). Skunks are 7-0 or 11-1 scores.

Decide who goes first by flipping the checker (heads or tails) or by putting the puck on the center line and both players trying to hit it on the count of 3. Or just let the younger player have it first.

You can only hit the puck if it's on your side of the center line.

You can't touch the puck with anything but your paddle.

Have fun. No getting mad.

That's it!

I'd really love to hear if you make a box hockey for yourself, drop me a line if you do.

Posted by Ted at 01:59 PM | Comments (1) | TrackBack

December 14, 2004

Simple Rubberband Gun

As kids, we used to make these as needed every summer, although occasionally someone would fashion a more elaborate one and keep it from year to year.

And no, none of us ever put an eye out with one of these. Then again, we were bright enough not to intentionally aim at the face. We also did a lot of target shooting with 'em. That's what I recommend: target shooting at cans or flies or plastic army men. Don't be dumb, and I'm not responsible if you are.

Materials
Wood - length of broomstick or dowel, or a 1"x2" or even a 2"x4". Whatever you use, you need a piece about 12" long (more for a 2"x4" rifle).

Clothespins - tradition says use the wooden spring type, but the plastic ones will work just fine. The simplest gun uses one, we usually used at least two. They come in bags of 100 or more, so borrow from a neighbor if you don't have your own. Or make lots of guns, you politically incorrect brute.

Rubberbands - in our house, we kept rubberbands around the doorknob on the furnace closet, and had plenty because you got one with every newspaper delivered. They're cheap, so don't go mugging the paperboy for his.

How To
Take sandpaper and round off any sharp edges to eliminate splinters.
Use a file to cut a shallow "V" notch in the end of the wood.
Use one rubber band to fasten a clothespin to the wood on the opposite end of the wood from the notch.
That's it!

Here's a picture of a fancy store-bought model that works exactly this way. It's a good view of the clothespin and notch setup.

To Use
Hook a rubber band around the end of the wood so it's in the notch.
Stretch it back with one hand, use the other to open the clothespin and catch the rubberband.
When ready to shoot, press on the clothespin and zing!

You can cut out pistol or rifle shapes from the wood, mount multiple clothespins (and make extra notches), and do all kinds of custom coolness with the basic design. Often we'd grab a piece of scrap wood, use a rock to gouge out the notch, grab a clothespin from the clothesline out back and a handfull of rubberbands from the doorknob. Within minutes you had something that worked, and sometimes the ugliest thing was the straightest shooter (my best was from an old yellow broomstick with two clothespins attached). Showing up with a store-bought rubberband gun was tolerated - barely - mainly because we'd closely examine it to see how they managed multiple shots if it worked that way.

Posted by Ted at 05:49 AM | Comments (1) | TrackBack

October 11, 2004

Half-baked Halloweeny Idea

Let's build a Haunted House!

In the comments, leave a description of a room or area in our haunted house. What does it look like? What kind of eerie stuff is there?

Two starters:

Butler's Pantry: a small narrow room dominated by a huge desk built in along one wall. There are two oil lamps on the back wall, and a dusty, decrepit wooden chair before the desktop. On shelves above the desk are the old volumes of ledgers used by the butler as he managed household affairs, and dozens of small drawers and cubbyholes. One drawer is conspicuous by the large padlock holding it closed. The hasp looks hastily added and was clumsily installed.

Root Cellar: only accessable from outside the house, just by the kitchen door, opening the door reveals narrow stone steps leading down into darkness. The air inside is damp and cool.

So come on, put on your imagination caps and join in the fun.

Posted by Ted at 05:03 PM | Comments (9) | TrackBack

June 20, 2004

Box Hockey redux

The memory is the first thing to go. I completely forgot about our half-finished box hockey set until this evening, when I got a comment from this place. It's not the same game, but it still looks pretty cool. I'll finish up our series this week sometime, although judging from the lack of feedback I don't think anyone was paying all that much attention. :)

Posted by Ted at 07:28 PM | Comments (4) | TrackBack

May 30, 2004

Box Hockey - 3

The previous post about our project to build an old fashioned box hockey table can be found here.

As usual, the main part is in the extended entry, and y'all are invited to ask questions and leave comments.

Constructing the frame
Cut out the end and side pieces Ė two of each Ė and square up the ends. Test fit the pieces together and do a measurement from one corner to the opposite corner on the other side. Each diagonal measurement should be the same or nearly so. If they are, then your frame will be squared up correctly.

Hereís where a drill will come in handy and save you some blisters, you should drill pilot holes for the screws that hold these bits together. Countersink the holes too if you want, itíll look neater and you can use a little wood putty to fill the holes once the screws are in place. The picture shows what I mean, those two light colored dots on the end are where the screws and putty are. In it we're looking up from below and can see where the bottom will be nailed into place.

BoxHockey1.jpg

When you drive the screws, put a thin smear of the glue on the wood where it joins together, then finish tightening the screws. Use a damp rag to wipe up any glue that squeezes out.

You can also (barely) see in the picture that I used finishing nails to attach the goal boards into place (right side, three light dots). The goal board is positioned 3Ĺ inches in front of the end boards. Countersink the nails and use a little wood putty again to fill the holes. Let the wood putty dry.

This is what the finished frame looks like, looking from one end to the other.

BoxHockey2.jpg

Lay the assembled frame on top of the hardboard and, using a pencil, trace along the outside of the frame to mark the cuts needed for the bottom of the box hockey game. Make sure you use the corner of the hardboard as one reference point, because thatíll make sure you get two straight edges Ė one end and one side. Set the hardboard aside for now, weíll get to that in a little bit.

Cut a length of leftover wood about four inches long, wrap a piece of medium grit sandpaper around it, and use it to sand the frame smooth. Lightly round the edges and corners too. Always sand with the grain of the wood (long ways along the boards). Once everything is sanded, do it again with a piece of fine sandpaper. Sanding by hand is a pain in the butt, I suggest getting zen with it, grasshopper.

Before you attach the bottom, go ahead and apply the finish of your choice to the frame. You can paint it, use varnish or tung oil, or for maximum protection use polyurethane. You can apply the polyurethane with those disposable foam brushes, just keep the coats thin to avoid big runs in the finish. If you want, you can sand the frame between dried coats with fine steel wool, that will really smooth out the finish. Follow the directions on the can for timing between coats and cleanup. Let everything dry thoroughly.

Cut out the rectangular hardboard bottom. Save the leftover hardboard, we'll be using it for the rest of the pieces. Flip the frame upside down, then place the hardboard with the smoothest side down on top of the frame. Starting in one corner, fasten the hardboard bottom to the frame using the small nails (panelling nails work well for this), spacing them every four inches or so.

Next time, we'll finish up the game board, cut out the paddles, and I'll talk about the rules we used to use.

Posted by Ted at 07:36 PM | Comments (3) | TrackBack

May 27, 2004

Box Hockey - 2

I talked about Box Hockey back in March, but things got hectic and that became low priority. Now is a good time, so let's get started.

If you've never followed the Rocket Jones Build It series, I do some project online over a series of posts and hopefully by following my directions you can complete the same project. Our first project was a model rocket.

As usual, the meat of the post is in the extended entry, and y'all are invited to ask questions and leave comments.

Building a Box Hockey game is about as simple as it gets. As I said in the original post, the woodworking skills are basic and power tools are helpful but not necessary.

Here's what you'll need from the hardware store:
(3) 1"x4"x6' pine -or- (2) 1"x4"x8' pine
(1) 2'x4' hardboard (1 smooth side)
(16) 1.5"x#6 flathead wood screws
(1) pkg mixed grit sandpaper (we'll use medium and fine)
(1) box small flathead brads (~5/8" long)
(1) small can of polyurethane
(1) 1" paintbrush

Tools and supplies needed:
Saw
Screwdriver
Drill and 1/16" or 3/32" bit (this will make things so much easier)
Elmers white or yellow glue or equivalent (optional but recommended)
Hammer
Straightedge
Ruler, yardstick or measuring tape
Pencil

Buying wood
Look for straight pieces without splits or chewed up edges. A few knots are ok, as long as they're tight and won't readily fall out. It's ok to pick through the rack of lumber to find just the right pieces, so be picky.

When you're looking at a piece, rest one end on the ground and sight down the length of it as if you were aiming a rifle. This will make obvious any warping, bowing, or twisting in the wood. You don't want that, get the straightest pieces possible. Look at it on edge, then swap the board end-for-end and look again. It may be necessary to buy an extra piece or two in order to get enough straight wood, since some boards might be perfect for half or two-thirds their length and then get funky. Since the boards should only be a few bucks each, it's worth the money to get good wood right up front.

Measurements - Frame
The frame of the Box Hockey game is made of 1"x4" pine. You'll need to cut 2 sides (42.5" long), 2 ends (22" long), and 2 goal boards (20.5" long). Cutting rabbets and dados will make the frame stronger, and if you know what that means then you can adjust the measurements on your own.
box hockey plans3.JPG
The goal boards have three goal openings cut into them. The outer two are 3" wide and start 3" from the ends, the middle one is 2.5" wide and sits 3" from the side goals. Make them tall enough to let a checker slide through (at least 1/2"), ours are 1" tall. You can see what I'm talking about on the diagram above (it's not to scale).

In the next day or two I'll talk about constructing the frame and what to do with the hardboard.

Posted by Ted at 12:01 PM | Comments (8) | TrackBack

March 05, 2004

Box Hockey - 1

When I was a youngster, one way we filled our summer days was by going to the local elementary school for Ďrecí. Rec was shortspeak for ďRecreation ServicesĒ and it was a program sponsored by our school district. Basically, for a few hours a day, someone (usually a college kid earning some pocket money) would sign out kickballs and jump ropes and games. There would be organized activities like bike races and weenie roasts and marble tournaments. I fondly recall heading up to the school to find out who was there and what was going on. It was one of the Ďmixing bowlsí of the area, because otherwise groups of kids mostly hung around together based on what street they lived on.

Some days it was just too darn hot to do anything. Even marbles sucked, because the best dirt beds for that were in full sun, and nobody felt like frying their brains.

Thatís when the board games would come out. Alongside the playgrougd were several fixed benches, shaded by the buildings and close to the cool bricks of the school wall. Looking like birds lined up on a telephone wire, we were grouped up in various ways as we played the games. Parcheesi (ick), Sorry and Chinese Checkers, Mandala (we called it something else though), and my personal favorite Ė Box Hockey.

Box Hockey was the low-tech version of Air Hockey. In fact, to that point we had never heard of Air Hockey. Play is similar, and so is the speed of it, if only because the Ďrinkí is smaller.

The puck was a regular olí checker, and the paddles were wedge-shaped pieces of hardboard. Each end had three goals, larger ones on each side worth one point, and a smaller one smack in the middle worth three points. Games went to 11 or 15 or 21, and there was usually someone hovering nearby with dibs on the next game.

When my kids were that age, I built our own Box Hockey game. It proved to be a hit, and I built several more over the years to give away as gifts. On the underside we put a checkerboard and backgammon board, and just flipped the hockey rink to play those. We'd usually include a set of checkers, some dice, and if the child was old enough a set of chess pieces.

So thatís what weíre going to do this go-round of "Build It", weíre going to build a Box Hockey set. It makes a great birthday gift, or save it as a surprise for those heat-wave days coming up. It's also a great family project, simple enough to have the little ones pitch in. It makes it more special when they help.

If youíve never done any woodworking, no worries. The skills are basic, the materials are readily available and inexpensive. Power tools will speed things along, but arenít at all necessary.

Update: While out running errands tonight, I made a quick stop at the hardware store to price the lumber needed. I'm estimating right up front that you can do this project for around $30.00. Not bad for a from-the-heart gift.

Next time (probably this weekend), a detailed parts and measurement list, and pictures!

Posted by Ted at 05:00 AM | Comments (9) | TrackBack

February 23, 2004

Flight Report (lack thereof)

Our rocket was scheduled to make her maiden flight this weekend, but high winds prevented it. I could've launched, but probably would not have gotten it back from the drift under parachute.

Posted by Ted at 07:24 AM | Comments (2) | TrackBack

February 15, 2004

Build It - the finished rocket

We've had a nice stretch of weather, which allowed me to get outside to paint our rocket. You can do painting like this in the winter, but the secret is to bring the rocket into a warm place immediately after the final coat.

The picture, and the rest of this post is in the extended entry.

What is all this about? "Build It" is a series of posts where weíre building a basic model rocket online. Each post shows part of the process step by step, including pictures and passing along tips and tricks Iíve learned along the way. You can find the rest of the series here.

fatboypaint.jpg

I used Rustoleum sandable primer, and Krylon gloss white, gloss banner red and gloss regal blue, all in spray cans. Step one was applying four light coats of primer, sanding with 320 grit sandpaper between coats. Then I let it sit for several days.

Next up, an all-over coat of blue, applied in 4-5 light coats, followed by one fairly heavy 'finish' coat. I let the rocket sit in the sun for about ten minutes between coats. The nice thing about Krylon is you can recoat anytime.

If I were going to be masking this rocket off to paint different colors, then I would have let it sit for several days for the blue paint to fully dry. Instead, I decided to 'fade' the colors together.

Starting at the top, I sprayed several coats of white over the blue, making sure I never went as far down as the joint where the nose cone meets the body tube. I concentrated more paint towards the top of the rocket to completely cover the tip of the nose. The nice thing about this 'fade' technique is that you can just do it by eye and stop when it looks good to you.

I also did a light fade of white in a band near the top of the fins so that the red and blue would contrast better and to brighten up the red a little.

Once that had dried a few minutes, I sprayed the red in the same manner as the white. Concentrate the color more towards the ends of the fins and bottom of the rocket to create the 'fade' into blue. I was careful to not completely cover the white band.

The best tool for painting a rocket like this is a 5/8" dowel about 18" long. Slide it up into the motor mount and you have a wand to hold and manipulate the positioning of the rocket while you spray.

Several hours later (I got impatient, you should wait a day or two), I cut out the decal and put it on the side of the rocket. I didn't use the fin decals. I normally don't like the newer self-adhesive kind, but this worked ok. I also thought about cutting out the "FAT BOY" letters to write something like "OY BATF", but it's been done before, so I stuck with the original.

So that's it! We now have a completed rocket. Maiden flight will be next weekend. Saturday we have a club launch in The Plains, Virginia, at Great Meadows Equestrian Center, and on Sunday is the first Culpeper launch of the year. A Launch Report will be posted, and as always everyone is invited to attend. Email me for more information or leave it in the comments.

Posted by Ted at 07:43 AM | Comments (2) | TrackBack

February 03, 2004

Build It (quickie update)

I know there hasn't been an update in a while (find previous posts here). I've been dodging weather, trying to get the rocket primed and painted. It's not ready to go yet, but getting there. The plan is to make the maiden flight on the 21st of February, at the NOVAAR club launch.

Sometime in the next week or so, I'll try to get a post up about the stuff you need to launch a model rocket safely and inexpensively.

Posted by Ted at 07:54 AM | Comments (0) | TrackBack

January 19, 2004

Build It - 8

This is a series of posts where weíre building a basic model rocket online. Each post shows part of the process step by step, including pictures and passing along tips and tricks Iíve learned along the way. You can find the rest of the series here. To learn more about what model rocketry is about, see this Q&A.

The main part of the post is in the extended entry so you donít have to deal with it if you donít want to, but I hope you follow along because when we get done youíll have built and flown your first model rocket. Questions asked from before are answered too.

We're ready to play with paint!

If you want to, you can spend a little time with some extra-fine sandpaper to smooth the glue fillets we applied along the fins. Like anything other paint job, prep is 90% of the way to getting a great finish.

First step is the primer. Use Krylon or Rustoleum, grey, white, or ruddy brown, whatever you can find as long as it's sandable.

You'll need to make a simple tool to hold the rocket while spraying paint. The easiest way is to roll up a sheet of newspaper into a tight cone, and then slip it into the motor mount. You can use a couple strips of masking tape to hold it together. Then you hold the 'wand' with one hand while spraying paint with the other.

The key to getting a nice finish using spray paint is to use light coats. By light, I mean you should still be able to see through the paint until after your third coat. The primer dries quickly, so this doesn't take a long time. You want to spray many light coats instead of one or two heavy ones.

Once you've got complete coverage (up to 4 or 5 coats), let it dry - read the can, it's usually less than an hour - and then lightly sand the entire rocket with that extra-fine sandpaper. Let the rocket sit and dry for at least 24 hours.

It's possible to get near-professional results with this method, but you're going to put in plenty of sandpaper time and effort. If you wanted to, you can repeat the entire priming/sanding process two or more times, and running a tack cloth over the surface in between each sanding session.

Next comes the color coat. Once again, I tend to stay with Krylon or Rustoleum. Since the Fat Boy has white decals, I'm going to use a dark color so they show up well. If I were going to paint the rocket a lighter color and I'd used a dark gray or brown primer, I'd then spray a couple of light coats of white first, just to lighten up the final finish coats.

The same spray techniques apply with the color coat. Spray multiple light coats to prevent runs and drips. Read the can carefully and follow their directions for drying times. Sometimes you have to wait a minimum of time between coats, or put the next coat on within a certain time frame.

I suppose I should mention that you should always paint outside. Even if it's cold out, you can go out, spray the coat of paint, and then bring the rocket inside until it's time for the next coat of paint.

Once you get the rocket completely painted with the color coat, let it dry. Because of the many coats used (or if you got impatiant, the thick cover coat), the rocket needs to sit for at least 24-48 hours, and longer is better.

Next time, we'll mask the fins and paint them a different color for contrast.

Posted by Ted at 10:26 AM | Comments (0) | TrackBack

January 14, 2004

Build It - 7

This is a series of posts where weíre building a basic model rocket online. Each post shows part of the process step by step, including pictures and passing along tips and tricks Iíve learned along the way. You can find the rest of the series here. To learn more about what model rocketry is about, see this Q&A.

The main part of the post is in the extended entry so you donít have to deal with it if you donít want to, but I hope you follow along because when we get done youíll have built and flown your first model rocket. Questions asked from before are answered too.

Parachutes. Technically, these are parasheets, and real parachutes arenít measured in diameter, but in square inches (or feet) of canopy. Model rockets have been doing things their own way since the beginning, and it works just fine. The Fat Boy has a purple and white chute, which is 18Ē across. Estes 12Ē chutes are orange and white, and 24Ē chutes are red and white.

Lately, Estes has been including pre-assembled parachutes in its kits. If you have one, all you really need to do is make sure that the knots are tight. If you want to make the parachute better, follow along as I explain the steps to construct one of the Estes chutes, and re-do a couple of simple things.

Lay out the plastic sheet and using an x-acto knife and metal straightedge, cut it out on the outside lines. Itís a hexagonal shape, and the parachute shrouds will be tied into each corner.

At this point I always stick a binder reinforcement onto each corner. These little self-adhesive paper rings are available in the stationery section of most stores, and keep the strings from tearing through the plastic. Alternatively, you can use a small square of duct tape (about ľĒ square). Whatever you use Ė if you use anything Ė make sure it lays flat so the strings canít catch on it.

Stretch the string out and fold it back on itself twice. Youíre going to cut it into three equal lengths. While weíre at it, weíll start calling them Ďshroud linesí too instead of the Ďstringsí.

Using a sharp pencil point or thick needle, punch a hole in each corner of the chute, inside the reinforcement ring or tape square. Thread an end of a shroud line through, then tie a double knot and pull it tight. Tie the other end of the shroud line to the corner immediately to either side. Do all three shroud lines in the same way, so that each corner has one line attached and you have three loops of line coming off of the chute.

While itís flat, decide whether youíd like to cut a spill hole. This is a hole in the apex of the canopy that lets the air out from underneath. The reason for it is that without it, a chute will tend to oscillate in the air as the air spills out from the edges of the canopy. If you remove enough, itís also a good way to increase the speed that the rocket comes down, since youíre removing a part of the canopy. On real chutes, adding a spill hole can actually increase the efficiency of a canopy, which will increase its descent rate.

Estes chutes have the optional spill hole already marked. Just use your xacto knife to cut out the dotted lines around the center logo. I do recommend doing this for the Fat Boy, because that 18Ē chute is awfully big for the weight of the rocket.

If you ever want to make your own model rocket parachute, itís easy to do. Any plastic bag material will work, or you can use the heavier plastic from those rolls of picnic tablecovers. Whatever you use, add some color if needed with permanent markers or hilighter marker because a clear plastic chute will be invisible at altitude.

For shroud lines, you can use heavy carpet thread, braided nylon, dacron or kevlar, or a brand of dental floss called Glide. The Glide is made of teflon and is fire resistant, which is a good thing for our purposes.

To attach the parachute, gather all of the shroud lines and thread them through the plastic loop on the nosecone. Pull the lines through and open them enough to slip the canopy through. Keep tightening the lines by lightly pulling on the canopy until the shroud lines snug up against the nosecone loop.

Alternately, you can attach the chute to a fishing swivel using the same steps. This way, you can move the chute from one rocket to another just by opening the swivel and reattaching it to another nosecone loop. You might need to use needlenose pliers for this. There's a picture of fishing swivels here. The shroud lines go through the small loop at one end, and the big end opens like a safety pin so you can attach it to the nose cone.

Now a little bit about aerodynamics and what makes these rockets safe to fly. For the Fat Boy kit, it should be perfectly stable as built, assuming you didn't add a bunch of weight at the aft end. Not all kits are naturally stable, so if it comes with a chunk of clay in the kit, you'll need to put it inside the nosecone as the kit instructions direct. In any event, you should at least do a quick check on a completed kit. The following tells how and why.

On standard rockets - fins at one end, nose cone at the other, nothing really odd going on in between - there are two places on the rocket that are critical to stability. First is the Center of Gravity (CG) and it's the point where the rocket weighs the same in either direction, like a fulcrum of a teeter-totter, or perfectly balanced scales. In the exact same way as a teeter-totter, you determine the CG by balancing the rocket on a pencil or some such (I use my finger - it's close enough). The point where it balances is the CG. Put a little pencil mark there.

I talked a little bit about the CG here without naming it (the bit about the hand out the window). The CG is the point that the rocket will rotate around as the fins correct the flight path.

The second place is called the Center of Pressure (CP). This one is a little harder to explain, but just like the Center of Gravity is where all the weight of a rocket balances, the CP is where all the various aerodynamic forces balance. These forces include thrust, drag and gravity, as well as the roll, pitch and yaw of the flying rocket.

To determine the CP, the easiest way is to make a cardboard cutout of the rocket outline, then balance it on something like you did for the CG. The difference here being that the cardboard is only two dimensional. It also represents the rocket flying through the air sideways (90 degree angle of attack), since it's presenting the largest possible cross-section to view. What this does is give the most conservative CP of the airframe. This CP will be farther forward - toward the nose - than any other angle of attack.

Your rocket will be stable if the Center of Gravity (CG) is in front of the Center of Pressure (CP) by at least one diameter of the main body (caliber). So if the CG is twice as far in front of the CP as the body diameter, then the rocket has two calibers of stability.

All this is great for regular rockets, but the Fat Boy is rather short and squatty, so the margin for stability is shortened a bit, and you'll find you probably have around 3/4 of a caliber stability, which is fine for that kit.

To move the CG forward, you can add weight to the front of the rocket, or add length. To move the CP backwards, you can either add length to the rocket, or increase the size of the fins, or the number of fins, or sweep them backwards.

Having the CG too far ahead of the CP is called 'overstable', and can cause the rocket to be overly sensitive to wind gusts. It can behave like a weathervane and cock sharply into a breeze, just like a, uh, weathervane.

One last thing, you should measure the CG when the rocket is prepared to fly - motor, chute and the works, because that's how the rocket will actually fly. Sounds dumb, but it's not. The motor can shift the CG significantly backwards.

A simple test for stability is called the 'swing test'. Find the rocket's CG (remember, ready to fly configuration), and tie a long piece of string around it at that point - use a spot of tape to hold it in place. Then take the string and swing the rocket around your head like you were using a rope lasso. The rocket should settle into place and look like it's flying horizontally around you. Sometimes it will settle in tail first, that's ok. And for certain weird cases, a rocket will tumble as unstable, even though in actual flight it'll be fine. But for 99% of the time, this is a good test, and even scale models of real rockets have been checked this way by engineers in informal testing.

Or you can trust the kit. :) Where the CP and CG become important is when you design your own rockets.

The math to determine the CP isn't that difficult, and was worked out in general form by Jim Barrowman in 1966. Known as the 'Barrowman Equations' (duh - and the link is a .pdf document), they simplify the process by making several assumptions about the rocket and aerodynamic environment. They're still a useful approximation and are still frequently used.

So what kinds of practical use is all this CG and CP hocus-pocus?

Well, for our rockets, we want them to be stable so that they fly straight and safe, especially since model rockets are unguided, and rely on fins to keep it going straight up.

In general, an airplane (real or model), wants the CG and CP to be closer together, so that they're neutrally stable. That way, the plane is easy to steer because the airframe isn't fighting to keep itself pointing in the same direction. A military fighter is going to be closer to unstable, and thus more nimble, than a passenger jet.

Military missiles, especially air-to-air versions like the Sidewinder, are purposely designed to be unstable. They can turn-on-a-dime, figuratively speaking, and the only thing that allows them to fly straight at all is the onboard guidance computer, and controls like fins that rotate, tiny steering rockets along the sides, or thrust deflection. Larger missiles without fins steer by changing the direction that the engine bell is pointing, using the rocket thrust itself to steer.

Posted by Ted at 06:24 AM | Comments (0) | TrackBack

January 12, 2004

Build It - 6

This is a series where we build a model rocket step-by-step. You can find the rest of the series here.

The main part of the post is in the extended entry so you donít have to deal with it if you donít want to, but I hope you follow along because when we get done youíll have built and flown your first model rocket. Questions asked from before are answered too.

If you have questions, please leave them in the comments or email me.

This time weíre going to do the last of the glue work, and itís quick and easy.

For each side of each fin, run a small bead of glue along the edge where the fin meets the body tube. Then take your finger and smooth the glue into the crease. Donít wipe too much glue away, just try to leave a smooth rounded fillet. If youíre using brown carpenters glue, the gel formula will keep the glue from running and you can do all the fin fillets at one time. Otherwise, just do one or two at a time and let it dry before moving on to the next. These glue fillets add lots of strength to the fin joint and you should always do them.

We didnít glue in the motor mount before attaching the fins, so lets do that now as well. Apply the glue fillet to the seam where the centering rings meet the body tube, just like you did with the fins. Smooth it with your finger, and since weíre using wood glue I recommend putting a second coat on after the first is dry. Do this for both ends of the motor mount Ė top and bottom. The top fillet is deep inside the body tube, so what you can do is take a long scrap of the balsa that the fins came from, and use that to apply the glue. Donít worry about being perfectly neat, the important thing is getting the joint glued.

Buildit6-1.jpg

The instructions tell you to mark a line between the fins to help you align the launch lug. Instead of that, I usually install the lug in the corner where the fin meets the body tube. This way the lug is automatically lined up vertically (the pre-cut fin slots help), plus itís stronger for the extra surface to glue against.

Finally, itís time to glue the shock cord mount into place. You should have a Ďpaper sandwichí which has the elastic coming out of one end. Use a good bit of glue, and attach the mount to the inside of the top of the body tube, with the elastic pointing up towards the nose cone. Make sure you get it far enough down inside the body so that it doesnít interfere with the shoulder of the nose cone.

buildit6-2.jpg

You can trim the elastic to a length of about 24Ē or so before or after gluing the mount into place.

The reason for making the shock cord longer is a phenomenon known as the 'estes dent'. What happens is that during the flight, the nose cone is Ďfiredí forward by the ejection charge. If the shock cord is too short, then the nose cone stretches the elastic until it zings right back at the rocket, crunching the top of the body tube. Using a longer shock cord prevents this from happening. A good rule of thumb is to make the shock cord 2-3 times the length of the body tube.

Once the shock cord mount is dry, use more glue to make sure itís firmly glued into place. This part is going to keep your rocket attached to the parachute and nose cone, so use some care here. You also want to make sure it's as flat as possible, so that there's nothing to snag the parachute on it's way out.

When everything is dry, tie the end of the elastic shock cord to the plastic loop of the nose cone. Use a double knot and make sure itís tight.

At this point, the rocket is ready to fly except for the parachute. In the next day or so Iíll put up the next part talking about the parachute and some information about flight stability. Weíll also get ready to paint the rocket.

Posted by Ted at 05:16 AM | Comments (3) | TrackBack

January 04, 2004

Build It - 5

This is a series where we build a model rocket step-by-step. You can find the rest of the series here.

The main part of the post is in the extended entry so you donít have to deal with it if you donít want to, but I hope you follow along because when we get done youíll have built and flown your first model rocket. Questions asked from before are answered too.

Cardboard tubes, balsa, paper and plywood all fall into the category of wood products, and the best adhesive is wood glue. A well-fit joint will be stronger with wood glue than even epoxy or industrial grade cyano-acrylate (CA) - AKA 'superglue'. The technique to make these indestructable glue joins is called the 'double-glue method'.

That 'indestructable' claim isn't exageration either, because the materials being joined will break before the glue bond fails. It's not unheard of to have a fin break just beyond the glue.

So what's this secret way to glue rockets together? It's simple.

1. Lay a light bead of glue along the root of the fin.
2. Put the fin into place so the glue gets onto both parts to be joined. In this case, the fin root and the body tube.
3. Pull the pieces apart. There should be a light coat of glue on both pieces. Let it dry almost completely.
4. Put another bead of glue on the fin root, then press the two pieces together for good.

The reason this works is because the first coat of glue penetrates the materials to be joined, and the second coat chemically bonds with the first, locking eveything together. This makes for an incredibly strong joint.

For the Fat Boy, I suggest just sliding the motor mount assembly into position without glue (the metal motor hook will be sticking out the bottom), then gluing the fins into position. Use plenty of glue on the fin tabs which go into the slots of the body, and less on the parts of the fin root that don't fit into the slots.

It's fairly important to get the fins straight, but vertical alignment is more important that being perfectly spaced or perpendicular to the body tube. Since the Fat Boy has slots that the fins fit into, this is taken care of for you. When gluing the fins into place, take the nose cone off and set the rocket body upside down on your work surface so that you can look down at it and better gauge alignment. Looking from above, all three fins should point to an imaginary spot directly in the middle of the motor mount tube. Wipe excess glue away with your finger, smoothing it into the joint where the fin meets the body tube.

finsdry.jpg

Tip: If you've already bought motors, put one in the motor mount because it's easier to 'aim' the fins at the small nozzle than it is at the imaginary point in the empty tube.

Leave that be and let's assemble the shock cord mount. Hopefully you've taken my suggestion and picked up a package of 1/8" sewing elastic, because the length supplied with the kit is just too short.

In the instructions is a diagram for the standard Estes shock cord mount, sometimes called a 'paper sandwich'. If you're building a different kit then follow whatever directions you've got, or use the following diagram to make one like ours. At the end, you should have a truncated pyramid shape folded twice with one end of the elastic embedded inside. Here, you should be generous with the glue, yet squeeze it out so that it's as flat as possible.

shockcordmount.jpg

Let everything dry. Be patient, give it a couple of hours.

Next up we'll do the last of the glue work when we put on fin fillets, reinforce the engine mount, attach the launch lug and install the shock cord mount.

Posted by Ted at 08:02 AM | Comments (0) | TrackBack

December 31, 2003

Our Rocket

I haven't forgotten our rocket that we're building. In fact, it's sitting right beside my monitor, looking phallic and making me feel slightly inadaquate for not moving along to the next construction step. I promise we'll get to it in the next day or so. In the meantime:

Wal-Mart is having their after-holiday sales, and I noticed they have an Estes rocket starter set called the 'Stars & Stripes' for $17.00. The kids got this one for me last year for Christmas and it's one heckuva deal. The rocket is a little easier to build than the Fat Boy we're currently doing (and the Fat Boy is not at all difficult). Plus you get a couple of motors, the launch pad and rod, and the launch controller to ignite the rocket motors. All you'll need besides this starter set is some glue and AA batteries.

If you're building along, or thinking about it, now is the time to look for a pack of rocket motors. Each rocket kit will give a list of recommended motors, to start out I'd recommend 'B' motors. For the Fat Boy, get B4-4's or B6-4's if possible, they come in 3-packs and the igniters are included. Look here for an explanation of rocket motors and their designations.

Check back in the next couple of days for the next bit as we attach the fins to our rocket.

Posted by Ted at 07:59 AM | Comments (0) | TrackBack

December 10, 2003

Build It - 4

This is a series where we build a model rocket step-by-step. You can find the rest of the series here.

The main part of the post is in the extended entry so you donít have to deal with it if you donít want to, but I hope you follow along because when we get done youíll have built and flown your first model rocket. Questions asked from before are answered too.

This time we're going to put together the motor mount. It's a simple process. If you're building the Fat Boy, then the motor mount consists of the motor tube, two cardboard centering rings, a metal engine hook, and the black engine holder ring. Every model rocket has this setup, with minor variations. I'll talk about that after assembly.

Test fit the centering rings on the motor tube first. I had to widen the inner holes a little bit by reaming it out with a pair of scissors. The rings should slide on easily, don't force it.

Mark the motor tube (it's not quite 3" long) according to the instructions. Carefully push the tip of your x-acto knife into the tube at the proper mark to make a small slit. The slit only has to be wide enough to accept the width of the motor hook.

Push the "L" shaped end of the motor hook into that slit, so that the motor hook lays flat along the length of the tube. Then slide the black engine holder ring onto the tube and over the motor hook. Don't glue anything yet.

Now slide the rings onto the tube. If one ring has a notch in the inner cutout, then that notch fits over the squiggly end of the motor hook. The idea here is to allow you to lift the overhanging end of the motor hook out of the way to insert and remove the rocket motors.

I recommend putting a couple of wraps of masking tape around the motor tube and hook right where the hook goes into that slit you cut. It's not strictly necessary, but it's simple insurance to prevent a potential problem later.

Now it all looks like this. Nothing is glued yet, but we're ready to go.

buildit4-1.jpg

Put a bead of glue all the way around the place where the motor tube goes through the centering ring. If you're using the gelled stuff that won't run, do both sides of both rings all at once, otherwise just set the motor mount on end and do the 'top' surfaces. When dry, flip it over and do the other sides.

You don't need a ton of glue here, but use enough to completely circle the tube. Use your finger to lightly smooth it into the corner of the joint and then straighten out the centering ring again if needed.

Set it aside to dry.

Here's how this whole assembly works. The rocket motor goes into the motor tube and rests against the hook (the one through the slit). When the motor ignites it pushes against that hook, which is secured to the motor tube, which is glued to the centering rings, which will be glued to the airframe. Simply put, the motor takes off, and everything else goes along for the ride. That's the reason for the wraps of masking tape I recommended earlier - to keep the hook end in place. If the hook slips out of the slot, then the motor will just thrust straight up through the rocket and blast off by itself, knocking the nosecone out of the way on it's way through. Entertaining, but not in any way a successful flight.

Some kits use a 'thrust ring' to prevent this instead of, or in addition to the motor hook. It's just a cardboard ring that is glued inside the motor tube where the hook enters, to give the motor something substantial to push against.

The other end of the motor hook (the squiggly bit), has an important function as well. Besides letting you move the hook out of the way to extract an expended motor, it also keeps the motor in place when the ejection charge goes off, which deploys the parachute.

Newton's third law states that for each action there is an equal and opposite reaction. The ejection charge of a model rocket motor fires forward (towards the nose, which means that the body of the motor is forced backwards. Without the motor hook in the way, the motor would eject out the back of the rocket and the nosecone would stay in place (meaning no chute). Lawn dart.

If your rocket doesn't have a motor hook, then you can do a couple of things. First off is what they call friction fit. This is simple and wonderfully effective. Use pieces of masking tape (I use enough for about a half-wrap) around the end of the motor case closest to the nozzle end, until the motor is a very snug fit in the motor mount. The idea is to make it easier for the nosecone to come off than it is to expel the motor, 'path of least resistance' style. Another method that I've used is to put the motor into place, and then use a couple wraps of masking tape around the motor and motor mount tube. You can also do both, but that's usually overkill.

Next up will be the shock cord mount, and putting the motor mount into the body tube. Maybe a little bit about the chute too.

Posted by Ted at 11:09 AM | Comments (0) | TrackBack

December 08, 2003

Build It - 3

This is a series where we build a model rocket step-by-step. You can find the rest of the series here.

The main part of the post is in the extended entry so you donít have to deal with it if you donít want to, but I hope you follow along because when we get done youíll have built and flown your first model rocket. Questions asked from before are answered too.

If you have questions, please leave them in the comments or email me.

This is my rocket so far, after sanding the nosecone seams smooth and filling the spiral grooves on the body tube. Total sanding time was maybe 20 minutes. If you did those steps, you'll notice that the tube is a little fuzzy. Don't worry about that, because we'll smooth it out when we spray primer. I also had to spend a few minutes sanding the tabs on the fins so that they would slide easily into the slots. Nothing is glued together yet.

buildit3-1.jpg

You may have noticed that the fin tabs have a small slice trimmed out at the bottom. This shallow notch fits over the black ring of the motor mount. This particular rocket boasts a nice bit of engineering because everything fits together and reinforces itself, making for robust construction. In fact, although we'll be flying this bird stock on B and C motors, I've seen the same kit strengthened and modified to fly on I motors (128 times more powerful)!

I said I'd be building the motor mount this time around, but I'll save that for the next one. Instead, I'd like to talk about what actually happens during the flight, and some of the basic aerodynamics involved.

Model rockets are set up on a 'launch rod', which ensures that the rocket stays straight until the rocket is moving fast enough for the fins to keep it stable. A good way to picture how the fins work is to compare it to a weathervane, and how it always points into the wind. When a rocket is moving through the air, its flight through the air provides the 'wind' that the fins work with.

Everyone has stuck their hand outside a car window at speed and felt the rush of air. When you keep your hand flat to the ground, the air moves smoothly past it, but if you try to cup your hand against the wind, then the wind pushes against it. The fins work in the exact same way, and it's this push that causes the rocket to stay straight.

The main effect of this is that the straighter the flight, the less drag the rocket has to overcome and the higher it will go. I'll go into other aspects of this as we go.

Posted by Ted at 06:41 AM | Comments (0) | TrackBack

December 01, 2003

Build It - 2

This is a series of posts where weíre building a basic model rocket online. Each post shows part of the process step by step, including pictures and passing along tips and tricks Iíve learned along the way. To learn more about what model rocketry is about, see this Q&A.

The main part of the post is in the extended entry so you donít have to deal with it if you donít want to, but I hope you follow along because when we get done youíll have built and flown your first model rocket. Questions asked from before are answered too.

If you have questions, please leave them in the comments or email me.

The instructions for most model rocket kits are wonderful. Estes has been doing this for years, and their experience shows. Let me stress one point right up front: always, Always, ALWAYS follow their suggestions for glues to use. You can sometimes use an alternate (I have almost 20 different kinds of adhesives for various situations), but their recommended glue will give you the strongest bond.

Looking at the parts

Almost everything that needs assembly tells you to lay out the parts and make sure you have everything, and also to read through the directions first to understand things. This is a simple kit, so do it if youíd like, but it wonít be a problem if you donít. For more complicated kits, I do recommend doing it.

Lets look at the various parts, most of which are obvious. The biggest tube with the slots cut in one end is the body tube. In a simple rocket like this, itís main purpose is to hold all of the important bits in their correct places. The nose cone is straightforward, as are the fins. The parachute is the plastic sheet with the strings attached. So much for the obvious bits.

The tiniest tube (it looks like a drinking straw) is the launch lug and itís used to steady the rocket on the launch rod. The length of elastic is the shock cord, remember I recommended replacing it with a longer piece bought at the store. The two cardboard disks, the medium sized tube and black ring will be put together with that little metal strip and become the motor mount.

Pre-assembly

Using your x-acto knife, carefully cut the fins out of the balsa sheet. Theyíre die cut, and held in by just a few short bits of wood. If you want to, you can gently sand the fins (with the grain) with the fine sandpaper before freeing them. Make the same kinds of cuts to remove the smaller middle circles from the cardboard disks. Finally, you may need to open the inside of the squared-off loop at the bottom of the nose cone (see the picture). Do all of these carefully, and watch for the sharp knife.

buildit2-1.jpg

Make sure the fins fit the slots in the body tube. Sand them lightly if needed to ensure a smooth fit.

The following steps are completely optional.

Using the sandpaper, sand the seam on the plastic nose cone until it disappears. This isnít a quick process, but it does make for a much nicer looking end result.

Lightly sand the entire body tube until youíve scuffed the shine off. Donít sand too much, the purpose here is to remove the glassine layer, which will make for a stronger bond between the glue and the paper tube underneath.

Take some of the FillíníFinish and thin it with water until itís about the consistency of pancake batter. Slather it on the body tube (I use my finger) and work it into the spiral groove. You wonít need much, and most of what you use will be sanded away. Let it dry Ė itís fairly quick Ė and then lightly sand. The FillíníFinish sands easily, and when you get done there should be no spiral groove left. Repeat if you need to.

Use the same thinned FillíníFinish to fill the grain of the balsa fins. Keep the coats very very light, and sand between coats when dry. When you do the fins, do both sides at once, because the balsa will warp slightly and this will help even it out. The warp will straighten out when both sides are dry.

The reason for all this filling and sanding is because the smoother the surface, the less drag which makes for a higher flying rocket. I donít do it for every rocket, but I do take the time for most of them. The paint job looks much nicer on the smooth finished surface too.

Questions Answered

What is a Ďfishing swivelí? Also known as snap swivels, theyíre used to prevent the fishing line from twisting. They have a small loop on one end and a large loop on the other end that opens like an old fashioned safety pin. Hereís a (crappy) picture of a few, and like I said, youíll only need one, and itís optional. Also in the picture you can see the package of sewing elastic, the glue and FillíníFinish, and an x-acto knife.

buildit2-2.jpg

Next time, weíll build the motor mount and attach the fins.

Posted by Ted at 05:18 AM | Comments (1) | TrackBack

November 28, 2003

Build It - 1

Iím going to start a series of posts where Iíll build a basic model rocket kit online. The idea is to show the process step by step, including pictures and passing along tips and tricks Iíve learned along the way, while you follow along and build your own rocket.

Iíve asked a few people about this idea, and there seems to be some interest in it. Please feel free to ask questions as we progress, and hopefully we'll see some pictures as folks build and launch their rockets.

Once again, there will be a separate category just for these, called ďBuild ItĒ, and the main part of the post will be in the extended entry so you donít have to deal with it if you donít want to.

Introduction

The rocket Iím going to build is the Estes Fat Boy (see below). You can get this rocket in the toy section of WalMart for less than $9, look for 'Launchables' near the car model kits. You can also find it in some craft stores and hobby shops, sometimes in other packaging like a bag or box instead of the plastic bubble-package pictured, but it will probably cost a little more. If youíd like to build along and canít find the Fat Boy, you can get something similar because the basic steps will be the same. The Baby Bertha or Alpha would also be good choices, although most any Estes rocket kit will do.

FatBoy1.jpg

Materials

Now is also the time to gather building materials. If I mention a specific brand, itís because Iíve used it and know it works. There are all kinds of products out there thatíll work just as well.

Youíre going to need an x-acto knife (or equivalent, you could get by with a single-edge razor blade). Youíll also need some yellow or white glue. I recommend Elmerís carpenters glue, if you get the exterior stuff itís gelled and doesnít run and drip nearly as much (it's also brownish). You can also use Eileenís Tacky Glue, TiteBond, white school glue, or anything similar.

The only other must-have will be a pencil.

The following things arenít strictly necessary, but if you use any or all of them youíll have a nicer looking and better flying rocket. Theyíre completely optional, and Iíll note when to use them if you want to.

I highly recommend that you get a pack of sewing elastic. You want to get the flat 1/8" wide stuff, and it'll probably be 3 yards long. WalMart sells it for about a dollar, back in the sewing department.

Super-fine sandpaper, at least 220 grit (the higher the number, the finer the grit). You can find this in the hardware department in sheets, or small pads of it in the craft section. WalMart sells an assortment from 3M called 'wet or dry' sanding pack that contains two sheets of 220, two of 320 and a sheet of 400 grit.

Elmerís Fill Ďní Finish. Also found in the hardware department, get the smallest tub of this. If they have more than one kind with similar names, hold a tub of each in either hand and pick the lightest weight one. Weíll use this to fill the grain in the balsa wood fins and the spirals in the rocket body. You could use a lightweight spackle too.

Fishing swivel. This makes attaching the parachute easier. Donít buy a package of these, but use one if you can borrow it or already have one in your tackle box.

You can wait to get primer and paint, and I'll talk more about it later. Here's a little about it up front though.

Spray primer. I use Rustoleum sandable primer, it comes in white, gray, or even black. Get whatever they have.

Spray paint. Rustoleum or Krylon is what I use. Get whatever colors you want to use. The little cans of Testors paint near the models are cool colors, but very expensive for their size.

Masking tape. Youíll need a roll of ĹĒ tape if you want to paint your rocket with more than one color.

Posted by Ted at 06:11 AM | Comments (2) | TrackBack
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