From: buzz@rsd.dl.nec.com (Buzz McDermott)
Subject: Frequently Asked Questions, Part 2
Keywords: FAQ
Organization: NEC America, Radio Software Dept
Date: Fri, 11 Sep 1992 15:13:33 GMT
Expires: Sat, 10 Oct 1992 15:00:00 GMT


Rec.Models.Rockets FAQ (Frequently Asked Questions): Part 2 of 2

[last modified: 10 Sep 1992]

This is the second of two parts of the rec.models.rockets FAQ.  Comments,
corrections, and suggestions are encouraged and may be sent to Buzz McDermott
at buzz@rsd.dl.nec.com.

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

Section 7: Scale Modeling

7.1 I would like to make a scale model of the <??> rocket.  Where do I start 
    looking for technical data, dimensions, flight substantiation data, etc.?

    Two places to start looking would be Peter Alway's book of scale data.
    Another source is the list of scale data sources maintained by Kevin 
    McKiou and posted periodically to this newsgroup.  Refer to the section 
    'Other Sources of Information' in this FAQ for more details on these.
    
7.2 I've never built any scale models.  Are there any recommended kits for 
    first timers?

    The following recommendations have been made by posters to r.m.r:

    For A-D powered rockets:
      Estes IRIS (A-C power, semi/sport scale)
      Estes Black Brandt II (D power, sport/semi scale)

    Larger models:
      North Coast Rocketry Patriot (E/F/G power, sport scale)
      Aerotech ISQY Tomahawk (E-G power, scale)

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

Section 8: On To High Power

Review:  A High Power rocket is a model weighing more than 1500 grams 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.

8.1 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).

8.2 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

8.3 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
        -Tripolitan High Power Rocketry magazine
        -sanctions high power rocket launches
        -high power certification
        -dues: $40/year

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

    Type G rocket motors (80-160NS) are currently classed as 'banned
    hazardous substances' by the Consumer Product Safety Commission.
    H and larger motors do not fall under CPSC jurisdiction and may be
    purchased and shipped as Class B explosive devices, with restrictions
    on method of shipment, etc.  These motors must be used in compliance
    with the NAR and Tripoli high power safety codes.
 
    Reloadable motors' status is under review by DOT and CPSC. Shipping 
    propellant slugs is currently illegal per CPSC, but Aerotech has a 
    stay of enforcement applying only to their products. Unless it's changed
    [recently], no other manufacturer's reloads can be shipped except as 
    Class B explosive devices.

    [NOTE:  A recent ruling by the DOT has placed the status of shipping high
            power reload kits in limbo.  The exact ramifications of the
            ruling are not clear to the editor of this document at this
            time...Buzz]

    The NAR is actively pursuing relaxed regulations.  Pat Miller, the
    president of the NAR, recently met with NFPA and CPSC representatives
    and offered the suggestion that CPSC should alter its classification
    of G rocket motors to place them in the same class as accepted earlier
    by the NFPA (i.e., Class C Toy Propellant Devices).  The NAR and
    Tripoli are both working to insure that reloadable engine technology
    remains available to the hobby.

8.5 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.

    The exact status of the reload kits is under review by the NFPA.  It is 
    conceivable that they might be banned from consumer use in the future.  
    Both the NAR and Tripoli are working to prevent that.

    It is also not clear who is actually allowed to sell reloadable motors
    and reload kits or who is allowed to purchase them.  This is also under
    current review by the NFPA.

    The use of reloadable technology in high power (H and up) motors is 
    especially cost effective if you do your shopping via mail order.  
    Although casings, reloads, and expendable engines are all available at 
    discount from retail, H and up expendable engines must be shipped as 
    Class B explosives, which adds considerably to their shipping cost.  
    Reloads (currently) are being shipped as Class C flammable substances 
    and may be shipped via UPS for only a $5-10 surcharge.

    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 ***

8.6 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?).

8.7 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.

8.8 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.

8.9 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 now qualified to fly H rockets.  By 
    doing the same thing with an H rocket you can become qualified to fly
    I, and so forth.  You need to be certified for each new engine type.

    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.

    Again, the regulations surrounding the purchase and use of HPR motors is
    currently under review.  It is possible that a recognized certification, 
    such as those provided by the NAR and Tripoli, will be required to 
    buy HPR motors in the near future.

8.10 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.

8.11 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 cdt@pdp.sw.stratus.com (C. D. Tavares):
    From WHITMAN@ISTP1.GSFC.NASA.GOV ((Rusty Whitman):
      NCR Big Brute

    From cdt@pdp.sw.stratus.com (C. D. Tavares):
      AAA Penn. Crude

    From dwade@jarthur.Claremont.EDU:
      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: J.Cook@ens.prime.com (Jim Cook):
      LOC kits are a good introduction into high power - they are strong 
      (banging it several times for emphasis on the table).

8.12 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
      (801) 224-2276
      Catalog: $1.00

      Magnum Rockets, Hobbies and More, Inc.
      P.O. Box 124
      Mechanicsburg, Ohio 43044
      (513) 834-3306 (voice and FAX)
      Catalog: $2.00

      Rocket Research & Distribution
      8901 Milbrae Court
      Richmond, VA 23236
      (804) 330-4373 (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).

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

Section 9: Some Model and High Power Rocketry Records

[Note: This section will contain summaries of current national and international 
       records for model and high power rocketry.  I will add to it as I can
       determine what the records are...Buzz]

The high power records come by way of a posting from Chip Wuertz 
(dlw@engr.ucf.edu).  Chip is part of the University of Central Florida's high 
altitude rocktry project.  This information is believed accurate and up to
date as of 20 July 1992.

    Records and Altitude Project Ideas

    (To set the records straight and answer some recient questions)


    * * Some current records for NON-METALLIC NON-PROFESSIONAL Rockets: * *

    Top two altitude holders:

    1) Altitude -  24,771 feet 
       Percent Error on Track - 11.7%
       Set by   - Chuck Rogers and Corey Kline
       Location - Lucerne Dry Lake Bed, Lucerne, Ca.
       Date     - June 1989, USXRL-89

    2) Altitude - 22,211 feet
       Percent Error on Track - 5.3%
       Set by   - University of Central Florida
       Location - BlackRock Dry Lake Bed, Gerlach, Nv.
       Date    - August 1991, LDRS X

    Highest Tracked Flight at Lucerne

       Kline/Rogers Team - 24,771 feet, 1989

    Highest Tracked Flight at BlackRock

       University of Central Florida - 22,211 feet, Aug. 1991     

    Highest Tracked Staged Rocket

       University of Central Florida - 22,211 feet, L750 to L750

    * Published notes on Chuck Rogers / Corey Kline Flight:
    (Lucerne Test Range Tracking Results, November 1988 - May 1989) -

    New unofficial altitude record for nonmetallic high power/experimental 
    type rockets.  Possibly highest tracked flight of an amature rocket
    (metal or fiberglass construction) yet in the United States.  Korey 
    Kline and Charles Rogers became the first recipients of the Rocket
    Newsletter perpetual altitude trophy for the first flight to exceed
    the previous record of 22,080 feet set with a metal rocket by the Fort
    Team in May 1984.  The trophy will be awarded to the next team to 
    exceed the current record.  Record is unoffical because of some 
    uncertainty on the exact track.  The cloud of red carpenters chalk
    ejected by the rocket was barely visible (because of a background of
    white clouds at higher altitudes) and high wind speeds at 25,000 feet
    dispersed the tracking cloud in only 3 - 4 seconds.  Trackers only
    got a track on the general vicinity of the red carpenters chalk
    in front of a cloud.  Before they could zero in the track, the red
    cloud had disappeared.  The angles from the last position of the tracker
    heads was used for the track, the error was only 11.7%.  The tracked 
    altitude was within 3.2% of the postflight prediction (25,567 feet)
    using the Rogers Alt4 altitude prediction program with the actual
    liftoff weight of the rocket, and a preflight CD estimation from
    program CD2.  Undoubtedly a valid track, but because of circumstances
    considered an unofficial record only.  The Rocket Newsletter considers
    this track an official record.  This rocket used a single, custom-manufac-
    tured L500-25, made by the Rogers/Kline team.
    
    *** Note: unofficial means Tripoli unofficial.  Tripoli only recognizes
       tracks with less than 10% error.  (Chip Wuerz) *************
    

    * Published notes on University of Central Florida's Flight:
    (The TRIPOLITAN ... AMERICAS HIGH POWER ROCKETRY MAGAZINE,
       OCTOBER/NOVEMBER 1991) -
    
    Highest tracked flight at LDRS-X / BALLS.
    Second all-time highest track of a non-metallic high power rocket.
    University of Central Florida's research project and altitude attempt
    to break the current high-power rocketry altitude record of 24,771 feet
    set by the KLINE/ROGERS team in 1989.  Altitude attempt had been based on
    3850 NS L-engine, new Vulcan L-750 engines deliver 3,000 (now known to be
    less from motor testing results) newton seconds.  In an attempt to make
    up power loss and to provide margin on the goal altitude of 25,000 feet,
    the upper stage was delay-staged by several seconds.  Altitude predictions
    computer simulation program predicted 28,500 feet.  Upper stage flew 
    substantial trajectory, reaching apogee nearly 2 miles downrange.
    Rocket used microprocessors / timer-controlled staging and ejection,
    on-board flight data measurement package, and a radio beacon system to locate
    upper stage.  Track was accomplished using red carpenters chalk.  Both
    stages were recovered.
    
    * Tracking High Power Altitude Attempts -

    High altitude rockets are hard to track.  One of the most prevalent ways
    used in our hobby is carpenters chalk.  The UCF project used one pound of
    red chalk.  It looked about marble size from the ground (at 22,211 feet).
    The parachute wasn't even visable through high power binoculars.

    The University of Central Florida also uses a telemetry transmiter to
    send information on the altitude.  We transmit information on temperature
    and pressure.  By having this information for ground level and apogee,
    the altitude can be accuratly determined.  The signal is also used
    to point out the location of the substainer.  The reciever antenna is
    a six element crossed polarized yagi array, designed for maximum gain and
    directivity.
    
    My case and point is, if you can't see it how can you find it?
    In our case we use telemetry.
    For the trackers to see it, use pounds of chalk!
    
    One of the most important aspects of tracking is to have the chalk ejected
    at apogee.  In order to do this we use a plugged substainer motor (the
    delay columns are not that accurate, and are even less so for long delays).
    A timer circuit is used for precision staging and ejection.
    
    As far as breaking the record goes -  I feel it will be broken at the BALLs
    launch, unless LDRS rules change.  
 
    Rocket altitude varification - the method which is currently being
    used is RAS simulations.  Up to this point the only valid tracks 
    have to be taken optically by trackers.  I don't think they (Tripoli)
    will except electronic tracks (yet). 

    * Design considerations for high altitude -
    
    Their is a trade off in the rocket designs.  A single stage rocket
    has a much better chance to get the record because it is not as complex.
    But, the two or more stage rockets have an advantage in that they can
    drop off a lot of weight.  Now looking back on professional 
    history, has any rocket made it to orbit using a single stage configuration?
    
    Designing single and multistage supersonic rockets are a little tricker
    than that of subsonic rockets.  For example, it has already been pointed 
    out that the center of pressure changes. 
    To make sure the rocket will still be stable when supersonic you need a 
    more stable rocket to account for CP and CG migration.
    Also, it is important note that most flight simulation programs use
    subsonic formulas for various parameters and calculations.
    
    Another major consideration is the additional recovery requirements 
    for parachutes.  Randy Thomas from Paratech Parachutes has done a lot
    of work on researching parachutes and made the comment that parachutes
    behave differently above about 40,000 feet (air at 40,000+ feet?).  One 
    also has to consider the drift from a rocket at such a high altitude 
    (unless you want to recover your rocket in the next state).

    I guess for a future analysis, I see more high tech electronics being used
    like gyros.  Right now the altitude attempts are at the point of exceeding
    the high power limits of Tripoli.  In the future either Tripoli will have
    to up the motor limit or the altitude buffs will be in the realm of
    amature rocketry (if they arn't already there)! 
    
    
----------------------------------------

Section 10: 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 me (by way of r.m.r request).

    From J.Cook@ENS.Prime.COM (Jim Cook):
      Skip using glue W/ balsa dust, dope, or any other junk for filling the 
      grain in balsa fins or nose cones.  Use Elmer's "Fill 'n Finish" diluted
      with water to a thick paint (like white glue is) and paint it on.  
      Non-toxic and a coat or two will do.  Use Elmer's "Carpenter's Wood 
      Filler" thinned similarly to fill the spiral in body tube.  Both come 
      in a white plastic tub with an orange lid.  Note - the latter is 
      harder to sand, so don't make the mistake of using it on balsa as it 
      will require a lot of sanding.

    From cdt@pdp.sw.stratus.com (C. D. Tavares):
      Fill your fins BEFORE attaching them.  (Don't fill the root edge).

    From jim@doink.b23b.ingr.com (James B. Reed):
      To make spray painting a model easier, insert a spent engine nozzle
      end first.  Insert a dowel (or stick) in the engine and hold the dowel
      while painting the model.

    From: whitman@nssdca.gsfc.nasa.gov (Rusty Whitman)
      I've tried about everything to keep shroud lines from pulling off of
      plastic or mylar parachutes.  Those little tape disks are just about
      worthless.  Tying knots and cyano'ing the ends helps but you still
      have problems.  I don't know why I never thought of this before but I
      ran across a roll of duct tape in my closet and knew immediately that
      that was the answer.  I cut out some little squares of duct tape and
      attached some lines to a parachute and they won't pull free without
      ripping the plastic.  I don't know who invented duct tape but they
      deserve some kind of statue, its got more uses than a paper clip.

    From: utidjian@remarque.berkeley.edu (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.
      [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: utidjian@remarque.berkeley.edu (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: utidjian@remarque.berkeley.edu (David M.V. Utidjian):
      [To hold fins in place and aligned while drying I bought an Estes
      fin alignment kit].  At 15-16 bucks it seems a bit
      expensive but is well worth the aggravation and time it saves.  You
      can even make your own if you are handy.  I just set up my body tube
      in the jig and then check the alignment of all of the fins to the body
      tube. Then I use a thin bead of 5-min. epoxy. and in ten minutes I am
      done.  When I do the fillets I can do them all at once but don't have
      to worry about the softening the glued on fins so they droop.  You
      still have to lay the model on its side though but only for 5 minutes.

    Source unknown [but sounds like good advice to me: Buzz]:
      Make a jig for anything you do more than once (align fins, 
      join body tubes, etc.).

    From Jim Bandy (NAR member not on net):
      Use a piece of aluminum 'angle iron' for joining body tubes.  Place one
      tube in the angle, insert and glue the joiner, then insert and glue the
      other tube.  It give very straight joins.  The angle can also be used
      for marking fin lines on body tubes, etc.

    From: kaplow@pobox.enet.dec.com (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. 

    From: ixhwd1!hrbob@ixstar.att.com (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. 

    From: jack@rml.com (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 cdt@pdp.sw.stratus.com (C. D. Tavares):
      [On cutting Estes-style body tubes]
      The simplest and best I ever used was Howard Kuhn's jig from the old CMR.
      It's a simple piece of wood L-angle moulding, with a notch for a razor
      blade cut into one side (from the wing toward the elbow) at one end.
      The only other parts are a wood block and a large black spring clip (the
      kind you hold really thick reports together with).  If you want, say, a
      6" piece of tubing, you set the block 6" away from the razor notch and
      clamp it there with the spring clip.  Now lay the tube down the L-angle,
      butting it up against the wood block.  Insert the razor blade, press
      lightly, and turn the tube.  (Put a dead engine into it if the tube is
      the right size to fit one.)  Three to six turns, and you have an edge
      that looks factory-cut.

                       ----
                      (    )  <- spring clip            | <- razor (edge on,
                       /  \                             |    sharp edge down)
        ____________---------___________________________|_______
       |          /_|       |__/|                       |       |
       |          | |_______|  ||  angle moulding       |       |
       |          | wood block ||                               |
       |----------|____________|/-------------------------------j
      /                           lay tube here and spin it    /
     /________________________________________________________/

    From: umn.edu!ux.acs.umn.edu!vx.acs.umn.edu!soc1070 (Tim Harincar)
      When I cut tubes, I always wrap the tube with about two
      layers of drafting tape with the edge of the tape along
      the cut line. This accomplishes two things: First the
      thick tape edge providing a excellent knife guide. Second,
      you can assure a straight cut. If the tape wrinckles when
      you wrap the tube, you know it is not on straight; simply
      remove the tape and try again until you know its down flat.

      Drafting tape is better than regular masking tape because it
      has almost the same thickness but is made to be removed.

      This method is in addition to reinforcing the inside with
      a stage coupler or spent motor. Also, always use a new
      x-acto blade for the best cut.


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

Section 11: Ignition and Launch System Tips

11.1 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:
             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.

11.2 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: cdt@sw.stratus.com (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 buzz@rsd.dl.nec.com (Buzz McDermott):
      I've tried a couple of time to launch composite powered models using
      my old Estes 'Solar Launch Control', with 4 AA nicads.  It never worked.
      I switched to small 12V car battery (I took it out of an old Honda
      Accord I've been slowly destroying in my garage...).  It works great.

    From: billn@hpcvaac.cv.hp.com (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.

11.3 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 J.COOK@ens.prime.com (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).

11.4 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.

11.5 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.

11.6 Other ignition tips:

    From: dwade@jarthur.claremont.edu (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...

    From msjohnson@daisy.wichitaks.NCR.COM (Mark Johnson):
      The new Estes plug system is reputed to be extremely reliable.  I
      haven't yet talked to anyone who's actually tried it. [Note:  I've
      used the plugs several times, now.  No failures in my small sampling,
      and the plugs are faster than using wadding...Buzz]

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Newsgroups: rec.models.rockets