NetNews Usenet Archive 1992 #27/NN_1992_27.iso/spool/rec/models/rockets/3062

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From: [e-mail] (Buzz McDermott)
Subject: Frequently Asked Questions - Part 3 of 5
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Rec.Models.Rockets FAQ (Frequently Asked Questions): Part 3 of 5

Last Modified: 20 Nov 1992

*** PART 3: HIGH POWER ROCKETRY

Section 3.1: On To High Power

Review:  A High Power rocket is a model weighing more than 1500 grams (3.3 lb)
         or containing more than 125 grams of propellant (or any motor
         with more than 62.5 grams of propellant).  The NFPA has
         recently ruled that any motor with more than 80.00NS of total
         impulse is a high power motor.  This last ruling is under
         review by the NFPA and CPSC.

         Medium power rockets (E, F, and G) are, technically, model
         rockets according to the NAR definition, but any of these weighing
         more than 1 pound fall under the same FAA restrictions as high
         power models.  Many cities still limit 'model rockets' to those
         weighing less than one pound, as well.

         Advanced rockets are high power rockets weighing more than 3.3
         pounds and/or containing more than 160NS of total impulse.

3.1.1 I'm a successful model rocketeer.  What do I need to get into HPR?

    When this question was posted to r.m.r a while back, these were the pre-
    dominant suggestions and tips:

    - Start with E/F/G kits with 29mm motor mounts from LOC or Aerotech.
      These should be the easiest to build.
    - Get familiar with and use expendable motors before jumping into
      reloadable technology.
    - Join a high power club if possible (local NAR section or Tripoli
      prefect).
    - Be very careful of the construction differences between model and high
      power rockets.  You HAVE to build higher power rockets to be more sturdy
      than model rockets (see the next question).
    - If not already a member, join both the NAR and Tripoli (if you can
      afford high power rocketry, you can afford to join and support both
      these organizations).

3.1.2 What are the major differences between model and high power rockets,
    besides size and engines?  Are they built differently?

    Above and beyond all else, high power rockets are built much stronger
    than standard model rockets.  This is due to the higher speeds and
    acceleration achieved by these models.  Some of the construction
    differences are:

    - High power rockets have stronger, thicker body tubes
    - They have MUCH stronger engine mounts, bonded using epoxy rather
      than white or yellow glue
    - Engine mount rings, adapter rings, etc., are typically made from
      1/8" or thicker aircraft plywood, rather than paper or balsa
    - Fins are typically made from plywood or waferglass, not balsa;  (thick)
      balsa fins have been used on E and F powered models, but they have to
      be heavily reinforced
    - Fins are often mounted directly to the engine mounts through slots
      in the body tube (TTW mounting)
    - Parachutes are larger and typically made from some type of fabric
      (plastic chutes are not strong enough, usually)
    - Heavy elastic shock cords with steel braid or Kevlar shock line
      are used rather than rubber for shock cords, and these are typically
      epoxied to the motor mount or a bulkhead

3.1.3 Are there any national organizations to which I could join?

    There are two national organizations associated with high power rocketry.
    The first is the NAR.  It supports both model and high power rocketry.
    The second is the Tripoli Rocketry Association, which was formed by NAR
    members who felt the NAR was taking too much time getting a high power
    program together.  Tripoli is oriented more towards high power
    rocketry.  Both organizations offer certification programs for individuals
    wishing to purchase high power engines.  Anyone wanting to get involved
    with HPR is encouraged to join one or both organizations.   The addresses
    for both are in the section 'Some Commonly Sought Addresses'.

      National Association of Rocketry
        -sanctions contests
        -insurance for rocket flying activities
        -American Spacemodeling magazine
        -high power certification
        -engine certification
        -sanctions high power rocket launches
        -dues: $25/year (senior)

      Tripoli Rocketry Association
        -High Power Rocketry magazine
        -sanctions high power rocket launches
        -high power certification
        -dues: $40/year

3.1.4 What is a 'reloadable' motor.  Are they worth the price?  Are they legal?

    A reloadable rocket motor is a metal cylinder with screw-on end pieces.
    Solid propellant and time delay are purchased separately from the motor
    casing, in 'reload kits'.  These kits contain all of the expendable,
    non-reusable materials for a single flight.  The cost of the reload is
    significantly less than the cost of an expendable motor (when talking
    about F sizes and up).  Reloadable rocket motors are not currently
    banned by the NAR.  They are prohibited from competition at this time,
    though.  Use of reloadable technology is currently restricted by the
    NFPA to individuals belonging to qualified organizations.  The NAR and
    Tripoli are qualified organizations.

    Reloadable motors' status is under review by DOT and CPSC. Shipping
    propellant slugs is currently illegal per DOT.  Purchase of reloads
    is legal, however, given that the purchaser is properly certified to
    purchase and use the motors.  Aerotech its parent company, ISP, have
    stopped shipping all reloads until the DOT matter is cleared up.

    Reloadable motor kits and reloads are now predominantly available at
    high power launches, via distributors selling on the launch site.
    The recent DOT ruling has dried up the discount mail order sources for
    reloads, but even when purchased at launches (even if bought at near
    suggested list price) reloads are very cost effective compared to the
    cost of Class B expendable motors.

    YOU MUST BE A CERTIFIED MEMBER OF A QUALIFIED ORGANIZATION TO PURCHASE OR
    USE RELOADABLE HIGH POWER MOTORS.  See section 8.9, below, for information
    on becoming certified to use high power reloadable motors.

    WARNING: IT IS HIGHLY RECOMMENDED BY r.m.r CONSENSUS THAT YOU DO NOT
             ASSEMBLE AND/OR PREP A RELOADABLE-TYPE MOTOR UNTIL JUST PRIOR
             TO ITS USE (I.E., ON THE FLYING FIELD). *** UNDER NO
             CIRCUMSTANCES SHOULD ASSEMBLED RELOADABLE MOTORS BE STORED WITH
             IGNITERS INSTALLED ***

3.1.5 What is the current legal status of HPR motors?  I've heard the DOT has
    banned them.  Is that true?

    FIRST, YOU MUST BE A CERTIFIED MEMBER OF A QUALIFIED ORGANIZATION TO
    PURCHASE OR USE CLASS B EXPENDABLE MOTORS.  See section 8.9, below, for
    information on becoming certified to use Class B motors.

    The DOT has not banned high power motors.  Disposable high power motors
    have been classified as Class B explosives for some time and are available
    for purchase and shipment.  Class B explosives do have severe shipping
    restrictions, though, and high power motors are subject to these same
    restrictions.

    Reloadable motors, or rather, their fuel reloads, are another matter.
    The DOT has recently banned them from interstate commerce.  This means
    that NO reload (of any power, B - O) may be shipped to hobby stores
    or from mail order houses to individuals.  Currently, purchase of these
    reloads is limited to purchase at the launch site by Class B certified
    individuals.  The NAR and Tripoli are both working hard to reverse the
    current DOT position.  Both organizations request modelers patience
    and support.

3.1.6 What are these different 'types' of composite motors I hear about (White
    Lightning, Black Jack, Smokey Sam, etc.)?

    These are all manufacturers' names for various formulations of 'stuff'
    they have added to the propellants to get specific pyrotechnic effects.

    White Lightning (Aerotech): medium average thrust engine producing a
      bright white flame and distinctive roar.
    Black Jack (Aerotech): low(er) average thrust engine which produces a
      dense, dark exhaust to aid in tracking.  Also has a distinctive roar.
    Blue Thunder (Aerotech):  high level average thrust engines with a bright
      violet-blue flame and very little visible exhaust.  Designed for high
      thrust, high acceleration lift-offs.
    Smokey Sam (Vulcan): produces a dark exhaust to aid in tracking.
    Silver Streak (Rocketflite): produces a fine shower of white sparks during
      boost (I understand that these are actually black powder motors).
    Hellfire (Rocketflite?): a high thrust motor which produces a bright red
      flame (also a black powder formulation?).

3.1.7 What's an FAA waiver? Which rocket flights require one?

    An FAA waiver is official permission by the Federal Aviation Administra-
    tion allowing the launching of rockets exceeding a certain size.
    A waiver is required for all rockets weighing more than one pound,
    containing more than 160NS total impulse in its engines, having more than
    4 total ounces of fuel, having any motor with more than 2.2 ounces of
    fuel, or using reloadable engines, into FAA controlled airspace.
    This airspace begins at 1200 feet for many metropolitan areas, but can
    be as low as 600 feet around airports.  It is NOT legal to fly high
    power rockets without this waiver.  You do not need a waiver for 'model
    rocket' (i.e., under 1 pound) launches.

    The Tripoli Rocketry Association publishes information on obtaining an
    FAA waiver in their `Members Handbook'.  Several high power manufacturers
    also publish this information.

    The FAA is currently considering a proposal by the NAR to exempt all
    models meeting the NAR definition of a model rocket (i.e., 1500 grams...)
    from requiring a waiver.  This is still just under consideration.

3.1.8 Is high power rocketry legal in every state, if the proper forms are
    obtained?

    No.  Even with an FAA waiver, HPR is NOT legal in every state.  Check
    with your local fire marshal for requirements/restrictions in your area.
    The NAR is actively working to get state restrictions on model and HPR
    removed.

3.1.9 I've heard that NAR and Tripoli both have a certification process for
    using/launching HPR.  How do I get certified?  Am I required to be
    certified if I want to fly HPR?

    First, you have to join either the NAR or Tripoli.  In the NAR program,
    you first successfully fly a G powered rocket in the presence of two
    NAR HPR certified members who witness your flight.  You fill in and
    mail a certificate (along with $5) to the NAR, which places your name
    in its computerized list and mails you a new license stating your new
    certification level.  You are then qualified to fly H rockets.  By
    doing the same thing with an H rocket you may qualify to fly I motors,
    and so forth.  You need to be certified for each new engine type.
    If you wish, you can qualify for several motor types prior to sending
    in your forms.  You may then send them in together and pay only a
    single $5 processing fee.  Also, as of August, 1992, you may use
    clusters of motors to qualify for a particular impulse level (for
    example, you might cluster 2 'F' motors for your 'G' flight, or
    cluster 4 G42 motors (400NS total impulse) to get your 'J' certification.

    With Tripoli's 'Consumer Confirmation Program', you must successfully
    launch and deploy the recovery system (you don't actually have to
    recover) an H powered rocket in the presence of an Authorized
    Person (who these are is spelled out in the Members Handbook).  This is
    your 'confirmation flight'.  Your consumer card is filled out at the
    launch and one part of it is returned to Tripoli.  You are then said to
    have been 'confirmed'.

    Both organizations have 'grandfather' clauses to allow 'known HPR flyers'
    or members certified by the other organization to be certified without
    a confirmation or certification flight.  If you are Tripoli certified,
    (and an NAR member) you may send in your Consumer Confirmation card to
    the NAR (along with $5) and you would become NAR 'J' certified.

    Finally, both organizations are continually reviewing their respective
    certification processes.  The description listed here might differ from
    the actual certification process at the time you attempt to certify.

3.1.10 Where do I find out the proper way to use HPR rockets and motors?  I'm
     familiar with the NAR Model Rocketry Sporting Code.  Is there an HPR
     equivalent?

    Both the NAR and Tripoli have HPR safety codes.  The two organizations
    are working together to produce a consistent safety code to be presented
    to the NFPA.  These codes specify minimum launch field sizes, minimum
    distance to keep from launchers, etc.  The NAR Interim High Power Rocket
    Safety Code has been published in AmSpac.  The Tripoli safety code is
    published in their Members handbook, which is sent to all new Tripoli
    members.  Everyone wanting to get involved in HPR is strongly urged to
    join one or both of these organizations.  In the near future, it may
    be a requirement before you can buy motors.

3.1.11 What are some good kits to build when first getting into high power
     rocketry (assuming I have all of the basic model rocketry skills)?

    From [e-mail] (C. D. Tavares):
    From [e-mail] ((Rusty Whitman):
      NCR Big Brute

    From [e-mail] (C. D. Tavares):
      AAA Penn. Crude

    From [e-mail]:
      I REALLY like the Aerotech line.  Easy to build, well constructed,
      (Great nylon chutes, through-the-wall-construction, all that good stuff)
      and pretty reasonably prices.  They're all E-G.  ISP has a similar line
      (the parent company).
      [NOTE: See Aerotech modification suggestions in 'Hints' section of FAQ]

    From: [e-mail] (Jim Cook):
      LOC kits are a good introduction into high power - they are strong
      (banging it several times for emphasis on the table).

3.1.12 Are there any (discount) mail order houses where I can get high power
     motors, kits and supplies from several manufactures, as well as save
     some money?

    The following high power mail order houses were recommended by readers of
    r.m.r as a result of a request to recommend their favorites:

      High Sierra Rocketry
      P.O. Box 343
      Orem, UT 84059
      [phone]
      Catalog: $1.00

      Magnum Rockets, Hobbies and More, Inc.
      P.O. Box 124
      Mechanicsburg, Ohio 43044
      [phone] (voice and FAX)
      Catalog: $2.00

      Rocket Research & Distribution
      8901 Milbrae Court
      Richmond, VA 23236
      [phone] (voice and FAX)
      Catalog: $2.00

    Additional sources may be found in R. Michael Jungclas' list of
    manufacturers and sources (which is posted periodically to r.m.r, see
    section 1.3.3 for more details).

----------------------------------------

Section 3.2: High Power Construction and Finishing Tips

    This section includes tips and suggestions on various topics having to do
    with construction and finishing techniques.  These have been posted to
    r.m.r or mailed to the moderator by way of r.m.r request.  Refer to this
    same section in Part 2 of the FAQ (Model Rockets) for additional tips,
    oriented towards model rocketry requirements.

    Cutting, Sealing, Attaching Fins
    --------------------------------

    From: [e-mail] (David M.V. Utidjian):
      To fill the grain in balsa fins and fill in the spirals in body tubes
      use epoxy. I use HOBBYPOXY "Smooth 'n' Easy" Epoxy finishing resin.
      For fins it does the trick in one coat... and sands easily... and
      adds strength to the fins.  I use those disposable brushes with the
      metal handles and brush on a single coat after a preliminary sanding.
      I then use auto body primer filler in gray and red-brown from spray
      cans for the entire model.  This gives very thin and even coats. I
      alternate the colors of the coats to show where the low and high spots
      are.  My last sanding before paint is done with 400 grit wet/dry paper
      and I do this wet... being careful not to get any inside the body tube.
      [Another good coating-type epoxy is PIC 'Coating Poxy'...Buzz]
      [NOTE:  This is not for kids or the inexperienced!! This technique is
      used in HPR where the added weight is not a penalty: Buzz]

    From Bob Turner (NAR member, not on net):
      Bob Turner (the DARS NAR section advisor) suggests using alcohol in
      smoothing 'coating' type epoxies.  The PIC 'Coating Poxy' instructions
      suggest using your fingers to 'burnish' any surfaces (i.e., fins) filled
      with the coating poxy.  Bob suggests using a VERY soft cloth which has
      been dipped in alcohol to rub the fins after about 30 minutes (or
      whenever the expoxy starts to set and is just slightly sticky to the
      touch). [I followed Bob's suggestion and got MUCH smoother fins over
      the hand/finger burnishing method...Buzz]

    From: [e-mail] (Jack Hagerty):
      When sanding fins, or any other balsa part that you want to be all
      uniform, stack the parts together, even them up the best you can
      (you'll be surprised at how uneven those die-cut pieces are!) on
      the root edge and drive a couple of straight pins through them to
      hold the stack in registration while sanding. For larger fins,
      anything over about 2 sq in, use three pins. I find that the pins
      that come in shirts are just about the right size. The small holes
      that are left when you remove the pins are easily filled during the
      sealing/filling step.

    From: [e-mail] (Bob Kaplow)
      I've found two handy tools for sanding big rockets. 3M makes these
      sponge-like sanding pads. They are great for conforming to the
      curves of tubes, nose cones, fillets, etc., and make quick work of
      fillers. The second is a palm sander, just like Norm uses on TV. Big
      rockets call for heavy duty solutions. Save the belt sander for
      airfoiling the fins during construction.

    Condensed thread on filleting fins; many contributors:
      First, ALWAYS fillet high power fin joints, even fins mounted TTW to
      the motor mount.  This will add strength and improve the aerodynamics
      of the model.  The suggestions for filletting material include:
        * 5 - 30 minute thick epoxies
        * 30 minute (or longer) thin epoxy mixed with micro-balloons
          until it has athick, paste-like consistency; let it thicken
          some prior to using it
        * SIG Epoxilite (warning: this got very mixed reviews)

      Always keep a bottle of rubbing alcohol handy when working with epoxy.
      Dip your finger in the alcohol and run it along the fillet to smooth
      out the bumps.  It was mentioned that a pure epoxy 'topcoat' was
      necessary on top of the epoxy/micro balloon mixture, although using
      an alcohol-soaked finger to smooth the micro-balloons might eliminate
      the topcoat requirement.

      Use 30 minute epoxy with microballoons added. Let it sit for a few
      minutes in the pot so it thickens, and then apply it. The microballoons
      make it much less runny, so you don't have to keep watching the fillet
      to make sure it's not dripping or running around the edges. Also do one
      side of two fins at a time:
              \          /
               \        /     f = fillet, ^ = really bad version of body tube
                \f    f/      / and \ = fins
                 ^^^^^^

    High Power Motor Hooks
    ----------------------

    [e-mail] (bill nelson)
      I make a clip similar to the ones used on model rockets - however, I do
      not pierce the motor mount tube - I place the front end of the retainer
      over the front of the tube. It is epoxied/taped in place, just like with
      a model rocket.  I do not rely on spring pressure to hold the clip over
      the end of the engine. I use several turns of strapping tape - wrapped
      around the engine or motor mount and the retainer clip. So far, I have
      never had a problem with an ejected engine.

    From: Jim Cook <[e-mail]>
      Some folks at NARAM 33 suggested drilling a small hole in the side of
      the flange of the rear nozzle retaining ring [of an ISP reloadable motor
      casing] to tie the casing to the model.  Some might claim this to be
      "modification of rocket motors not approved by the mfg."  I had though I
      heard Aerotech was going to start doing this themselves, but I haven't
      seen anything yet.

    From: [e-mail] (Neil Pyke)
      I've built #8-32 "t-nuts" into my last couple of rockets and then made
      sheet metal brackets to hold the motor in.  I drill two holes, 180
      degrees apart, in the aft centering ring and then press and glue the
      t-nut into the hole.  The screw holds the bracket to the centering ring
      and I bend the bracket so it hooks over the end of the motor.  The t-nut
      works great but I've made my brackets too wimpy.  Those that saw
      me wandering  around just past the flight line at LDRS a couple weeks
      ago, looking for my ejected motor, will know that I have not perfected
      my application of this design.

    From: [e-mail] (A. Roger Wilfong)
      I've used a similar technique with t-nuts and had no problems - yet.
      I've also tried a coarse thread sheet metal type screw (I'm not sure
      what they're really called - the threading is about twice as coarse as
      a regular sheet metal screw) screwed into the rear centering ring at
      three locations.  The centering ring needs to be plywood and you need to
      carefully drill the correct sized pilot hole for the screw.  After
      'tapping' the screw into the hole, I took it out and ran a small amount
      of thin CA into the hole for reinforcement - let the CA set before you
      put the screw back in the hole or you won't get it out again.  This has
      worked on RMS-29 and while it is not as strong as the T-nuts, so far it
      has been more reliable than masking tape.

    From: [e-mail] (robert.e.wiersbe)
      [Bob] Kaplow uses special metal hooks that he bolts to the bottom
      centering ring.  The hooks look like this:

                |\
                | \
                |  \
                |   \
                |
                |
                |
                |
         _______|

      He epoxies the nut to the inside of the centering ring, and the bolts
      need an allen wrench to tighten (you could use any kind). He also has
      different length hooks for different size motors. I think the hooks are
      made out of brass.

    Custom Decals for High Power Rockets
    ------------------------------------

    The techniques described here could also be used for model rockets.  The
    decals made this way tend to be large and `thick', so this info has been
    included in the High Power section.

    From [e-mail] (Tim Harincar):
      As a computer graphics person, I have done quite a bit of experimenting
      with laser printers and making my own rocket art. I mostly stick with
      clear sticky-back type stocks, they are the cheapest and most available.

      I use Fasson brand, and I think its 1.5 or 2 mil. thick. It works good for
      large models but is a little thick for small scale stuff. It curls right
      out of the laser while it cools. Don't worry, though. It doesn't distort.
      This stuff is typically available at most quick print shops.  Typically
      its called Crack 'N Peel.

      Toner chips very easily off of the smooth finish, so be careful and as
      soon as you can, spray on an over coat of clear flat enamel or laquer.
      I tape the sheet down to cardboard then spray, Leave it for a day or so.
      This also makes it lie flat.

      I know that blank water transfer stock is available, but its about $3 for
      an 8.5 x 11 sheet. Use same method as above to preserve the image. This
      is usually available at model railroad shops.

      I have never seen the dry-transfer stuff, but I know its pretty popular
      with the railroad folks. (that is, the pre-printed stuff).

      One other option that I have wanted to try is the heat-transfer colors.
      Once you have a laser image, you lay a piece of special colored film
      over the image and heat either with an iron or re-run the sheet through
      the laser and let the fuser do the work. The color then attaches to the
      toner.

      Most of these colors are metallic, but there are some standard, non-
      metallic colors as well. Letraset was the first company to market
      the color transfer stuff.

    Other Tips
    ----------

    From: [e-mail] (David M.V. Utidjian):
      A better way to glue parts together than water based glues (such as
      Elmer's white glue) is to use 5 minute epoxy. You have to be fast and
      organized, if you are too late just swizzle up another batch.

    From: ixhwd1![e-mail] (Robert E. Wiersbe):
      I have found (through unfortunate experience) that all 5 minute epoxies
      are not equal, I now use 30 minute epoxy in all my construction. When
      attaching fins I put epoxy on the root but leave about 3/8" open at
      each end, then put CA on the exposed area an align the fin. The CA will
      hold the fin in place while the epoxy cures.


----------------------------------------

Section 3.3: Ignition and Launch System Tips

3.3.1 How do those 'Copperhead' igniters work?  They only have one wire?

    Copperhead igniters are actually two strips of copper wire with a
    thin mylar insulating layer between them.  To use these with regular
    alligator clips you need to use masking tape to insulate opposite sides
    of the igniter from each clip.

           'Thin' (side) view of copperhead igniter:
                       |    |
                       |____| < Motor with Copperhead inserted
             Masking   > ||
             tape      > ||
                         ||
                         ||<  Masking
                         ||<  tape

    Attach one alligator clip at each masking tape point, so that each clip
    only makes contact with one (opposite) side of the igniter.

    The Quest 'Tiger Tail' igniters are the same type of ignitors as
    Copperheads.  They come with a special 'wrapper' with openings for
    alligator clips.

3.3.2 Do you have any specific suggestions or tips for an ignition power
    sources? Can I use my old Estes ignition system with composite models?

    The Estes, Quest and other model rocket launch systems are fine for most
    model rockets.  If you do a lot of flying there have been some suggestions
    posted to the net.  If you are trying to launch cluster models with solar
    igniters you will need more 'juice' than 4 AA batteries can provide.  This
    is also true of clustered Copperhead type igniters.

    From: [e-mail] (C. D. Tavares)
      A motorcycle gel cell, however, will last a long, long time.
      Our club uses a gel-cell the size of three VHS tapes to launch 120
      rockets over six hours, and it comes home at about 80% charge.

    From: [e-mail] (Bill Nelson)
      I bought a 12 volt motorcycle battery for about $20. I only need to
      recharge it 3 or 4 times a year. I have adapted all my launch
      controllers to allow usage of the battery.

3.3.3 WARNING:  BE VERY CAREFUL USING ANY IGNITION SYSTEM WITH 'FLASHBULB' TYPE
               IGNITERS.

    Many (most?) launch ignition systems are not 'flashbulb safe'.  Just
    arming the circuit (i.e., doing a continuity check) will fire the
    flashbulbs and ignite the motor.  If you plan to use flashbulb ignition
    often, you might consider investing in a 'flashbulb safe' ignition system.

    From [e-mail] (Jim Cook):
      A lot of launch systems use a light bulb to do a continuity check.
      The current through the light bulb is enough to set off flash bulbs
      (They require only milliamps to fire).

3.3.4 THE IGNITION OF ROCKETS BY OTHER THAN ELECTRICAL MEANS IS BANNED BY BOTH
     THE NAR AND TRIPOLI SAFETY CODES AND SHOULD NOT BE USED.

    There was a fairly lengthy discussion in r.m.r about the use of hand-lit
    fuse to launch rockets.  Although there was an advocate of this method the
    consensus opinion of the net was that the NAR and Tripoli safety codes
    made good sense, hand-lit fuse igniters were unsafe, and electrical
    ignition (even if igniting fuse by electrical means) should be used for
    all activities.  Hand-lit fuses are also against most state laws.

3.3.5 How do you ignite second stage composite motors?  Can I use a black
     powder booster for the first stage to ignite the second (as I do
     with multi-state A-D rockets)?

    Upper stages of composite powered models may be ignited by
    electrical means or thermalite fuse.  North Coast Rocketry has
    a Technical Report covering this subject.  Excellent articles have
    also appeared in AmSpac and the Tripolitan.

    You cannot use a black powder booster to ignite a composite upper
    stage.

3.3.6 Other ignition tips:

    From: [e-mail] (Doug Wade)
      [concerning adapting launch controllers to 12V car batteries ...]
      Speaking of which, I took my Aerotech launch setup, lopped off the
      ignitor attachment, and the place where it attaches to the battery, put
      amp plugs on either end, put a plug on the battery, and made some
      alligator clips in various configurations for launching Estes stuff.
      This means that I can switch batteries and ignitor style in basically
      no time at all.  It's not a lot of work, and it makes life easier.  If
      you have the urge to do this kind of thing, make sure that you get
      plugs that can handle it.  A 12V motorcycle battery (Mine was about
      $40 but it's pretty nice) can put out something like 15A for a short
      period of time...


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Section 3.4: R/C Rocket Glider Construction Tips

The D-G powered R/C rocket gliders now available are presenting some new
problems to ModRoc'ers, who are more used to making balsa wings, fins, etc.,
then built-up wings.  Here is a set of tips submitted by Iskandar Taib, a long
time model plane enthusiast, and others.  There is an excellent FAQ in the
rec.models,rc news group.  It includes very good information on how to get
started into R/C flying, tips on where to buy equipment, etc.

3.4.1 Construction Reviews

     Aerotech Phoenix:     August, 1992, "Model Builder Magazine"
     Estes Atroblaster:    September, 1992, "Model Builder Magazine"

     Both articles are written from the perspective of experienced R/C
     aircraft modelers.  They both contain good construction and flying
     tips.

3.4.2 I'm building the 'XXX' R/C Rocket Glider and it uses foam core wings.
     Are there any  things I should know about working with foam?

     The first thing to know is that certain paints and glues dissolve
     foam. Both the stuff made out of white beads (referred to as "bead-
     board") and the blue (Dow Styrofoam (tm) ) or pink (DuPont Foamular)
     extruded foam will behave in the same way. Once sheeted a foam wing
     can sometimes be finished in a paint that ordinarily dissolves foam
     if one is careful about not putting too much on at a time. Here is
     a list of what will dissolve styrofoam and what won't:

     Will dissolve foam:

        Nitrate and butyrate dope
        Ambroid
        "Model Airplane Cement" (you know what I mean)
        Polyester resin (sold as "fiberglass resin" at K-Mart)
        Thick and thin cyanoacrylates (excepting UFO)
        Paints from spraycans
        Dope and paint thinners
        Gasoline
        Dope thinner, acetone
        Solvent-based contact cements

     Won't dissolve foam:

        Polyurethane paints and varnishes (inc. Rustoleum)
        White or aliphatic glues (Elmer's, Titebond)
        Epoxies
        Ethanol or methanol (sometimes used to thin epoxies)
        UFO superglues
        Water-based contact cements (eg. Southern Sorghum)

     Follow the instructions provided and you won't go wrong. Most struc-
     tural building is done with white glue and epoxy is used for sheeting
     the wing and/or putting down fiberglass, graphite or kevlar cloth.

3.4.3 Any tips for sheeting the wings on my Aerotech Phoenix?

     The Phoenix kit requires that you sheet the wing with balsa using epoxy
     as the glue. Aerotech also recommends that you vacuum-bag the wing for
     the lightest wings possible. Vacuum bagging is a fairly new technique
     that I will describe later.

     The process involves preparing the wing skins, mixing the epoxy (need-
     less to say, the 24 hour laminating variety, spreading it on the skins
     with a squeegee, scraping most of it off, applying the skins to the
     core, then assembling everything together in the core beds (the pieces
     left over after the core is cut), and putting lots of weight on top
     of the whole thing. Oh yeah.. the wing has to be kept straight so
     you'd have to do this on a very flat surface. The more pressure you
     can put on this, the better glue joint you'll have, and the less glue
     you'll have to use, which makes for a lighter wing.

     VACUUM BAGGING

     This is where the vacuum bagging comes in. The core bed/sheeting/core
     assembly is put into a large bag which is sealed on all sides. Then the
     air is pumped out of the bag. This is supposedly the equivalent of pi-
     ling hundreds of pounds of weights on the core. In fact they tell you
     to limit the vacuum to so many inches Hg otherwise the cores will crush.

     Vacuum bagging is also useful if you are going to lay up fiberglass
     on top of the balsa wing skins. Fiberglass cloth is now available in
     very light weights and people often use it in lieu of a covering film
     or fabric.

     The way it used to be done was that the cloth was laid down and a thin-
     ned (with alcohol) epoxy brushed into it. Then excess epoxy was removed
     using rolls of toilet paper (discarding layers as they became saturated).

     With vacuum bagging one lays down a sheet of drafting mylar on top of
     the wet glass cloth, then puts the assembly in core beds. The assembly
     is then vacuum-bagged. After curing the mylar sheets are removed and
     you end up with a glass-like finish that is extremely light since all
     excess epoxy has been squeezed out. This also obviates the need for
     lots of the filling and sanding usually necessary before painting.

3.4.4 How about help with my Estes Astroblaster wings?

     The Astro Blaster kit uses contact cement for sheeting the wings. The
     cement is of the water based variety. Itis applied to both skin and core
     and is allowed to dry. After this has occurred, the skins and core can
     then be brought together. This is a little trickier, since you don't get
     a second chance.. Once the core touches the skin you can't separate them
     without breaking something. The skins are just 1/32" thick so one
     has to be gentle with them.

3.4.5 How do you repair damaged foam wings?

     Repairing foam is fairly easy. One simply hacks out the damaged piece,
     glues in a block of foam and carves and sands to shape. Carving is best
     done with a brand new utility knife (the kind that has break-off points)
     and sanding can be done with a sanding block. Sheeting is replaced in
     the same manner - cut out the damaged piece and glue on a replacement.
     A little glass cloth or carbon fiber matte over the break helps too.

3.4.6 Some more uses of foam in rocketry...

     Foam is interesting stuff to play with. You can cut wing cores using a
     hot wire and 1/16" ply or formica templates. Parts for rockets can be
     made by simple carving and sanding.

     Even more interesting is making lightweight wings and other parts using
     foam, silkspan and thinned white glue. Someone called Ron St. Jean built
     lots of competition free flight models in this manner. The silkspan is
     applied wet over the foam, and thinned white glue is brushed on. When
     the silkspan dries it shrinks, and the result is an incredibly strong and
     stiff structures. One could conceivably use this method for nose cones
     or complex scale models. In England, foam and brown wrapping paper is
     used for complex ducted fan models (someone actually flies a seven foot
     long scale Concorde constructed like this).

     If one uses heavier paper (eg. grocery sacks) perhaps one can dissolve
     the foam once the white glue is set (use acetone or dope thinner for
     this).  For rockets imagine something shaped like a V2 made like this.
     Once the foam was dissolved you'd end up with a light weight craft paper
     tube of the proper shape, boat tail and all.

3.4.7 I need to cut the piano wire control rods.  Bolt cutters don't work well,
     as the metal is too hard.  Any ideas?

     From: [e-mail] (Iskandar Taib)
     What you want to do is get your hands on a reinforced cutting wheel
     like the House of Balsa Tuf-Grind. The Dremel ones tend to shatter and
     throw pieces at high speed. If you use them harden them with thin
     superglue.