Model Rocketry for the Frugal and Worse.
Copyright 1995 by William E Westfield.
All rights reserved. This article is redistributable under terms similar to
the gnu copyleft agreement (eg not for profit.) The redistributed article
must retain this copyright notice.
Modification history:
951211 - Add section on finishing supplies
951208 - Add "tube peeling"
Frequently asked question #N:
Estes charges like $10 for what amounts to some paper tubes, a nose cone,
and balsa. When I try to design my own rockets using parts from Estes,
it ends up costing even more! Surely there are cheaper alternatives!?
Yes, it is possible to build model rockets without spending as much as
Estes would like you to. Exactly how much you can save depends on how
much effort you are willing to exert, and how much performance you are
willing to give up by using materials that are heavier or less ideal.
Level one:
Sales, Specials, Kit-bashing, and Discount Distributers.
The easiest way to save money is not to pay list price for your rocketry
supplies. Local retailers like Toys R Us and Michael's have occasional
sales (eg, "anything you can fit in this bag, 40% off"), and this could be a
good time to stock up on whatever rocketry supplies you need. Discontinued
models are frequently reduced in price to clear them off the shelves, even
at "full price" hobby shops, or from Estes themselves. Some hobby shops
will offer a discount if you belong to a local club, or perhaps even
non-local clubs like the NAR. Hobby shop owners are not unknown to haggle -
if you're willing to buy a hundred dollars worth of engines at one time, you
might be able to negotiate a small discount. Get to know the people who own
and run your local hobby shop. They'll probably to tell you about specials
a little ahead of time, especially if you buy stuff as a result!
"Kit Bashing" refers to using the parts from complete kits to build OTHER
models. A model like the Estes ARV Condor has three nosecones, several
different sized body tubes, and assorted other components. If the sizes
meet your needs, or inspire your muse, this can be a cheaper source of
parts than buying them separately, especially if the kits you start from
happen to be on sale.
I should also mention "Bulk Packaging". Estes sells certain kits and
engines in "Bulk packs" (intended for school classes and scout troops and
such.) While the discount on Engines is not large when you look at just the
cost per engine, the bulk-pack price also includes wadding and some extra
ignitors. The discounts on bulk packs of rocket kits is more substantial,
but the kits available in this form aren't the most easilly "bashable".
Finally, there are a number of distributers that offer Estes parts at
a discount ALL of the time. Keep in mind a number of things when you
order by mail from a discount distributer:
1) You'll be paying postage. On the other hand, you might not
be paying sales tax...
2) Some things may be delayed. While it's obvious that it takes
longer for things to arrive by mail than getting them at the
local store, what isn't always obvious is that the discount
distributer may not have everything you want in stock, and
since they probably order in bulk from Estes (or whereever),
it can take a while before it IS in stock. A phone call to
the distributer may or may not tell you if things are in stock.
3) If you buy a kit from "Bob Hobby Shop", "Bob" can probably give
you advice on how to put it together, where it should be launched,
and so on. Discount distributers might not be so nice. If
everyone orders discount mail order, "Bob" will stop carrying
rocket supplies, and then where will you be when you discover
on Saturday afternoon that you need another launch lug for the
Sunday club launch.
Many of the discount distributers carry rocket lines other than Estes, so
this may be a good lead-in to expanding your horizons. Here are some
distributers that have been recommended in rec.models.rockets (rmr) over the
past few year, or that I have dealt with personally, or that have a
significant presence in hobby magazines.
1) Countdown Hobbies Model and high power rocket kits,
3 P.T. Barnum Square parts. motors,, and supplies;
Bethel, CT 06801-1838 discontinued kits; space and
(203) 790-9010 (voice/fax) science items; collectors items
CompuServe: 74640,3112 Catalog: $2.50
Internet: COUNTDOWNHOB@delphi.com
10% of an order is returned as a credit for your next order. Old kits,
many manufacturers, and a helpful owner. Countdown isn't usually thought
of as a discounter, but 10% is something...
2) Belleville Wholesale Hobby Estes, MRC, and Custom
1827 North Charles Street model rocket kits,
Belleville, IL 62221-4025 supplies, etc., at discount
(618) 234-5989 from retail.
(618) 234-9202 (fax) Catalog: $2
30% off Estes (full line), 35% off Custom, 40% MRC. $30 minimum order.
Also has things like "retailer's parts assortment" that may be appropriate
for clubs.
3) Magnum Rockets, Hobbies and More, Inc. High power kits, motors
P.O. Box 124 and supplies; also
Mechanicsburg, Ohio 43044 Aerotech Class C
(513) 834-3306 (voice and fax) composite motors
Catalog: $2
Approx 33% off Estes. A major player in the HPR lite and full HPR
arena, Magnum also carries the Estes line. In addition, they sometimes
have "Estes equivilent" parts at very low prices (eg tube connectors
in various sizes for $0.20)
4) America's Hobby Center 800-989-3989
These guys have a big add in every issue of Sprocketry. In addition
to substantially discounted (40% or so) "Specials" every month, they
have signficant quantity discounts as well ($10-50: 10%, $50-100: 20%,
$100-$400: 30%, over $400: 40%.) However, the word on rmr is that at
least the people at the other end of the order phone number are pretty
clueless when it comes to model rockets.
Level 2:
Alternate Sources, Group Buys
I mentioned above that Magnum sometimes has "Estes Equivilent" parts. Estes
is not the only company in the model rocketry business. While Estes may be
forced into relatively high prices by a multi-tiered distribution scheme (if
you want Toys R Us to sell your kits, you have to give them a big discount
off "list" price, and then they'll get annoyed if you undersell them by
mail), Many of the other companies in model rocketry are not so
blessed/constrained. The "2nd Biggest" (?) model rocket dealer, Quest, has
prices that are quite a bit cheaper than Estes, ESPECIALLY when it comes to
parts. The Quest parts aren't the same sizes as the Estes parts, but if you
are starting from scratch, it might not matter. As an example, a Quest
T-2018 body tube is $1.50, while an Estes BT-20 (about the same size) is
$2.70. The Quest body tubes also have a nice white finish, which helps when
it comes time to paint your model. Quest nosecones, adaptors, and motor
mounts are similarly less exspensive. A similar example is LOC MMT.95,
which has the same ID as Estes BT-50, but is slightly heavier, white, nearly
twice as long, and cheaper.
Quest also offers bulk packaging of ALL their engines and kits. Their
engine prices tend to start off lower than Estes, and get even lower with
the quantity discounts.
"Balsa Machining Service" will turn out balsa nosecones in a number of
shapes, including fully custom shapes and also including shapes equivilent
to most of the Estes line. Prices are lower than Estes, even without the
quantity discounts that BMS has available.
Apogee Components is apparently going out of the parts and kits business,
but until they stop selling, their body tubes and nose cones are also lower
in price than Estes, even for the "exotic" phenolic body tubes ABS
nosecones, and Kevlar shock cords.
Even a "full priced" hobby or craft shop will have balsa sheets at prices
lower than Estes "BFS-xx" sheets.
For even lower prices, various (uh, dedicated, I guess), hobbyists
occasionally take out several middlemen, and decide to buy body tubes
directly from the paper company that makes them for Estes, or an equivilent.
In order for this to work, they have to order a hundred tubes or more of a
given size, but, they figure, there will be other people around happy to buy
36inch white BT-60s at $1 each. Seek out such people and keep in touch, and
you too can benefit from their thriftyness (or perhaps insanity?). If they
happen to be mailing distance away, you would probably have to buy 20 or
more tubes to cancel out the cost of postage, but then you can sell extras
to YOUR friends. Such a purchase might be ideal for larger clubs...
A lot of the "Small" components of model rockets have identical but less
expensive equivalents available from quite mundane sources. The most
obvious example is that "snap swivels" used for detachable and
tangle-resistant parachutes, are available in the fishing section of
any sporting goods store. Here are some others:
Elastic Shock cord: Elastic band material (sewing store)
Rubber shock cord: Airplane rubber (hobby store)
Shroud lines: Coat or carpet thread (sewing store)
Streamers: (1") Surveyors flagging tape (hardwarestore)
Screw eyes: Screw eyes (Hardware) store
Dowels: Dowels (Hardware or craft store)
Microclips: aligator clips (electronics store eg Radioshack)
Level 3:
Creative Substitution.
(or, "You built a rocket out of WHAT!!!???")
Ahh. Here is where life gets interesting. By being somewhat creative, you
can build a model rocket, and maybe even a high power model rocket, for
ridiculously little money (indeed, even for $0.00 if you hang around the
right trash bins.) In addition, this is your chance to experiment with all
sorts of interesting materials. Some may turn out to have significant
advantages over more traditional rocketry materials, others will be
interesting only because they are less expensive. Let's go over the
different parts of a rocket, starting with the "major" components, and see
what sort of alternative materials are available.
A) Body tubes.
Unfortunately, it is difficult to come up with alternative tubes that are as
smooth, tough, and lightweight as the ones Estes uses (but, see above for
suggestions on where to get the same tubes at lower prices.) Still, by
trading off one thing or another, there ARE alternatives.
Existing tubes: Rumor has it that the fact that BT60 is the same
diameter as the core tube of a roll of paper towels is no accident... We're
all familiar with paper tubes from wrapping paper and so on that might be
usable for building model rockets. Aside from being harder to paint than
the coated tubes from most Model Rocket manufacturers, such tubes tend to be
a little on the weak side. It has been suggested that both these problem
can be improved by painting the tubes with sodium silicate solution ("Water
glass".) Various paints and varnishes may have similar effects. Mailing
tubes are available in several sizes, and are heavy enough for HPR-lite
models (in fact, "Sport Rocketry" has published plans that specifically call
for mailing tubes.) Fabric stores may be willing to give you the long cores
from rolls of fabric. A high-tech friend may have access to cores from
plotter or fax machine paper (typically VERY thick and strong.) At least
one surplus store in the bay area has nice (if short) paper tubes designed
to hold batteries (3 "C" cells, in this case.) $0.10 each. Heavy,
large-diameter (six inches and up) paper tubes are used as concrete molds,
and should be available at building supply stores. The cores for the
plastic produce bags from Safeway supermarkets are 12 inches long, have a
1/8 inch wall, and a perfect inside diameter for 38mm HPR woosh generators.
Some spiral wound "found tubes" that might otherwise be TOO heavy can be
"peeled" to remove the outer layers, and wind up with a thinner wall. Since
each layer is actually separate, it's pretty easy to remove an integral
number of layers so that the tube retains an even thickness along its
length, and you can tell when to stop. The secret is simply to get the
outer layer of paper wet. The glue used is usually both water soluble and
somewhat water resistant. So the water soaks into the outer layer,
softening the paper and starting to soften the glue. Then you find a corner
along one of the seams (that you'd normally fill with putty of some kind to
get a nice finish?) and simply unwrap the strip of paper. Usually some
shreds will get left behind, but they're easy enough to go back and peel
off, or attack with sandpaper.
Clear plastic tubes of about BT60 diameter can be found in 4 and 8 foot
lengths at hardware stores - they're designed for protecting fluorescent
lamp bulbs. PVC and similar plastic pipe is commonly available for
irrigations and such - rhm@fc.hp.com (Bob Miller) says that 3/4" thin wall
(sched 120?) PVC tubing is a good fit for 18mm engines.
--------------------
Roll your own: A few layers of average quality (eg copier) paper and
some ordinary glue will make an "OK" body tube if wrapped around a hard form
(like some wood doweling or a piece of pipe) of appropriate size. Higher
quality paper (eg "vellum") or higher quality glue (eg epoxy) will make even
better tubes. (Some competition fliers swear by BT5 sized tubes that are a
single layer of vellum sealed with a 1/8" seam held together with
double-sides scotch tape.) It may take some practice to make tubes this way
without ending up with the tube glued to the form, wrinkles and buldges, and
excess glue all over everything. One hint is that white glue can be applied
to flat paper, let dry, and then reactivated with a hot iron to form the
actual joint. Another hint is to use some waxed paper or plastic wrap
around your form. Heavier weight paper may also be used. The body of many
a competition egg-lofter is little more than an extra-long "shroud" made
from relatively thin carboard (or thick paper.) Mylar (copier
transparencies) "glued" with double-sided tape, is interesting for smaller
diameter tubes. A material with a lot of promise that I haven't seen used
much is corrogated carboard - the corrogations lend great strength to weight
ratios. You can remove one "flat" side of the cardboard by dampening it with
a wet sponge, and then peeling it off after the (water soluble) glue has
softened. "One-sided" corrogated board is available some places as a
packing material. The one-sided board is much easier to roll, of course!
You'll end up noticing that corrogated carboard comes in quite a variety of
thicknesses!
Body tubes may also be rolled from more exotic materials. Fiberglass is
probably the easiest to get a hold of (and forming a simple tube might be a
good intro to fiberglassing techniques.) Kevlar, carbon fiber, and stiff
polyester are reasonable fabrics, and polyester, epoxy, and CA, are
interesting resins to use. (Of course, with some of these materials,
you are no longer in the "low price" arena, except in comparison with
purchased tubes of similar composition.)
--------------------
Why is everyone hung up on TUBES, anyway? There is no particular reason
that a model rocket airframe has to be tubular. Conical airframes are
relatively popular, and have some structural advantages to pure tubes as
well as being a little easier to form than exactly round tubes. (The Apogee
Egglofters use a long cone formed from a piece of relatively lightweight
card stock.) In fact, there is no reason that the airframe of a rocket even
has to be round. Triangular or square airframes can be constructed easily
from any flat and suitably strong material (cardboard, balsa, foam-core
board, etc.) Be somewhat careful to join the seams strongly enough to
withstand the engine's ejection charge.
B) Fin materials
Balsa sheet is relatively inexpensive, and even more so if you get one of
the "grab bags" of various pieces that are frequently available (and usually
the pieces are big enough to be used for model rockets.) Similar grab-bags
of low-quality thin plywood are available, and for that matter, a 4by8 FOOT
sheet of 1/8inch harwood (furniture quality) plywood from a lumber store
will probably keep a whole club supplied for a long time. Stiff carboard
can be used to make fins, especially if several pieces are glued together
"ply-carboard" wise. Material as thin as index cards can be used on small
models.
*WARNING* Some of the following materials are significantly heavier than the
materials usually used for model rocket fins, and may shift the center of
gavity of the model far enough back to make the model unstable. CG/CP
calculations or "swing" tests are advisable when creating designs using
improvised materials.
Pieces of plexiglass large enough for HPR-lite fins can frequently be found
in plastics stores as "scrap" at low prices. Other plastic scrap usable for
fins might be found in unexpected places. For example, Old CDROMs can be
cut into pieces to provide nice shiny fins. Any printing you don't like can
be carefully removed with paint remover (be careful not to get the paint
remover on the plastic parts, though. They'll start to disolve and get
smudged. The part protected by the aluminum film can be cleaned without
problems.) Large fins made from CDroms tend to be on the brittle side.
G-10 (fiberglass) sheet is available from surplus electronics dealers in the
form of "printed circuit board material" and in smaller pieces as
"insulators". Usually, the circuit board material will have a thin coating
of copper on one or both sides.
C) Nose Cones
The same grab bag of balsa that gives you cheap fin material will probably
yield some "large" blocks of balsa that can be shaped into nose cones using
a lathe, or electric drill. Peter Alway's "The Art of Scale Model Rocketry"
contains the best description of how to do this that I've seen, even if you
aren't doing it for a scale model. If you have a real lathe, you can
probably make nose cones from harder wood as well. If too heavy, perhaps
they can be hollowed out to reduce the weight. Other materials like
styrofoam or florist's foam might be usable in a similar manner, altough the
resulting surface is likely to be rather un-pretty without coating it with
something else or with extensive filling.
Of course, purely conical noses can be rolled from paper in a manner similar
to rolling body tubes. For added strength and rigidity, these can be filled
in with expanding polyurethane "insulating foam" from a building supply
store. Such paper cones tend to be lighter than either balsa or plastic
nose cones provided by rocket manufacturers, so be sure to check the
stability of the resulting rockets. Coins can be coated with glue and
pushed into the foam to adjust the weight.
Given an existing nosecone, slightly larger copies can be made by oiling the
cone, and then covering with a sort of paper mache' made from paper toweling
(which has good wet strength) and white glue. As with paper cones, these
can be filled with foam to improve their strength. If paper toweling
doesn't have enough wet strength to make it easy to deal with for you, try
pop-up or even tub-style baby-wipes (rinse off the cleaning solution first.)
More exotic materials than paper mache' can be used, of course. But for a
nose cone big enough to justify fiberglass construction, finding a suitable
form to use as a mold may be a major part of the problem. In theory, you
ought to be able to make a mold of an existing nosecone in plaster of paris
or something similar, and apply the paper mache'/whatever onthe inside to
achieve an exact match for the external dimensions, but I haven't been able
to get this to work. These techniques tend to work better on somewhat
larger nosecones (BT55 and up) where you can use pieces of material that
are big enough to hold onto.
Lightweight modelling compounds like "Model Magic" have potential to be used
in making nosecones. Small (BT-5) cones can even be made from much heavier
materials like "Friendly Plastic" without their weight becoming excessive.
A sawed of piece of expended engine casing can be used to anchor the
material and simultaneously provide a correctly sized shoulder, and some
useful mass.
The little plastic cases that grocery-store "gumball" machines dispense
their wares in aren't bad if you are looking for hemispherical noses.
Plastic Easter eggs give you a choice of several shapes, and tend to go on
sale at substantial discounts just after Easter...
D) Miscellaneous parts
Engine blocks can be made from cut off pieces of an expended engine
casing (works for any size motor, too!)
Drinking straws can be used for launch lugs, especially if you can find
paper drinking straws. Plastic straws can be tough to glue - hotmelt
glueguns are said to work. You can also simply tape the launch lug to the
rocket body with masking tape - the forces on it aren't all that high. Or
use a flyway launch lug carrier as described by Paul Gennrich in the June,
1994 issue of "High Power Rocketry" magazine. Finally, small loops of wire
at the nose and base of a rocket can serve for launch lugs as well.
Parachutes can be made from all sorts of plastic sheeting that is readilly
available. Trash bags, dry cleaning bags, grocery bags, "space emergency
blankets" (which are aluminized mylar), "pizzaz wrap" giftwrap (more mylar),
plastic tarps, the list goes on and on. One rmr writer likes the orange
trash bags that become available around Halloween so you can make your bags
of leaves look like giant pumpkins. I really like the way clear plastic
looks on the way down (giant jellyfish), but it won't help locate your
rocket if it lands in tall brush or a tree. Shroud lines can be made from
carpet or coat thread (a heavy thread available in sewing stores), dacron
fishing line (which is usually braided - Monofilimant is not recommended),
or kite string (braided dacron or nylon is especially nice.) The shroud
lines can be attached with any number of sticky things, but brown polyester
packing tape seems to combine light weight, stickiness, and tear resistance
better than some other choices. Of course, you can also make parachutes
from fabric. Some sewing stores will carry ripstop nylon for making
raincoats, but a good kite supply store will have materials that are
thinner, lighter, tougher, less porous, and available in a wider range of
colors.
Sewing elastic has already been mentioned for shock cords. Nylon and
polyester braided ribbon is another possibility if you're one of the people
who believe in non-elastic shock cords. Kevlar cord for heat resistant
shock cord mounts can be found at kite stores, and sometimes as fishing
line. Watch out for newer materials like "Spectra", however. While these
are stronger than Kevlar, and may have other advantages for the kite flier
or fisherman, they aren't heat resistant like Kevlar! Another heat
resistant shock-cord mount material is braided wire leader material, also
available in fishing supply stores (although some claim that this is more
likely to cause "zippering" of your body tubes.) While you are in the
fishing section or kite store, check for snap swivels and/or quick connect
links. Snap swivels are often used to allow parachutes to be disconneted
from models when not in use (and hopefully, prevent some tangling of the
shroud lines.) They can also be used to make your nosecones
interchangeable. Fishing stores will have have a wide variety of small
snap-swivels that are both better and cheaper than the ones sold by rocket
vendors, and kite stores are likely to have even largers swivels carefully
selected from somewhere or other and rated up to several hundred pounds.
Good quality cellophane makes nice streamers, sort of like the ones that
Apogee sold.
Self-adhesive fiberglass tape designed for drywall seams is useful for
reinforcing motor tubes and the like (coat with epoxy.)
Fireproof crepe paper, or fireproofed cellulose "insulation" can be
substituted for recovery wadding.
E) Paint and Finsishing supplies
Model rocket manufacturers can't be blamed for the high cost of finishing
supplies, but it's still annoying. There are alternatives.
Paint: Despite it's outrageous price, many people agree that some of the
best paints around are the small-cans of spray paints sold in hobby and
modeling stores (Testors, Model Master.) A lot of this seems to be that the
colors available are more varied and more appropriate to model rockets than
cheaper spray paints. These are the same people that will put ten or more
coats of paint on a rocket, though, and certainly not all of the coats need
to be extra expensive. In fact I've seen Kmart's white primer (about $1)
recomended ("better than Krylon") in internet messages in the same paragraph.
Another tip is that black and white are easier to find in a wide variety of
brands and prices (again, WalMart and Kmart are cheap and often recomended.)
Any hardware store that "matches" paint colors probably has a large shelf
of canned paint that didn't come out quite right at very low prices. While
these colors probably aren't what you want on a rocket, there are usually
lot of shades of "almost white" that work fine as primer.
(A word of warning - sometimes paints are imcompatible with one another,
and will produce disasters (or "interesting effects") when you try to use
one over another. Unless you are using a proven combination, it would be
a good idea to test your planned paint scheme before starting painting of
a major project.)
F) Motors/Engines
I suppose that an ariticle on cheap model rocketry would not be complete
without at least some comment on the sorts of advertisements that read
"build your own rocket engines for only pennies apiece." While I personally
am not the sort of person who would catagorically condemn those people
interested in making their own rocket motors, I do feel that model rocket
motors are one of the places where you do get your money's worth. While it
may be possible to build your own motors using only a few cents worth of
chemicals, there is a lot left unsaid. Some of these unvoiced gotchas
include:
1) In order to get to the pennies each price range, you have to buy your
chemicals in large amounts, so your out-of-pocket expenses are high.
2) You have to make or buy various special tools for making the motors.
3) You'll need assorted amounts of safety equipment and test fixtures,
beyond the actual construction tools.
4) You'll need a relatively large land area for your testing.
5) You'll probably be engaging in what the local police will consider
illegal activities, both in making your motors, and in using them.
It doesn't take much of a lawyers time to cancel out your savings!
6) The finished "cheap" motors are unlikely to have delay or ejection
charges, and will vary a great deal from motor to motor in performance.
I'm also interested in amateur pyrotechnics, and recently bought a copy of
"The Best of American Fireworks News, Volume 2." There are a couple of
excerpts in there that are particularly telling. One article mentions using
commercial A8-3 rocket engines as a "quick and easy way" to make skyrockets.
This is followed up by another comment that includes:
I have made rocket engines from scratch for years, but
have just recently discovered that the time savings,
reliability, and better performance of commercial engines
make them a viable alternative.
These are discouraging remarks for the would-be motor maker, but the most
important reason NOT to make your own motors is implied in item (5) above -
"Model Rocketry" enjoys certain legal exemptions because it has shown itself
to be an exceptionally safe hobby over the years. If you make your own
motors, you are no longer protected under those exemptions - you are no
longer participating in "Model Rocketry". If you happen to have or cause a
major accident, the press won't be clued in to this distinction, so aside
from the people who actually got hurt, the reputation of the hobby will be
damaged, and we'll be another step closer to having model rocketry outlawed.
(
geocities.com/westfw)