Rec.Models.Rockets FAQ
(Frequently Asked Questions)

Part 9: Competition and Records

Posted: November 16, 2001

Last modified: November 16, 2001

9.0 Introduction

Short of actually flying and friendly spying, there is a surprising amount that can be learned about the competition game from the usenet. While doing the research on Deja/Google, it became apparent to me that there are really no FAQs in the game of competition. Instead, there is the occasional question followed by some pretty good answers.

My thanks to Buzz McDermott for getting this started and to Wolfram von Kiparski who maintained the FAQs before me. Best wishes to the person who will be making the next update. Most importantly, thanks to all those who are unafraid to ask.

9.1 Are there any manufacturers making kits specifically designed for competition?

Some of the competition kit OEMs and component manufacturers include:

Apogee Components
Balsa Machining Service
Edmonds Aerospace
Pratt Hobbies
Qualified Competition Rockets
Totally Tubular

In addition is a *wide* listing of competition kit resellers and scale kit OEM's, too many to properly include here.

9.2 What are the major categories of competition model rocketry?

The NAR sanctions model rocketry contests throughout the USA, and throughout the year. The contest year runs from July 1 - June 30. The final contest for a given contest year is NARAM, usually held in August, after the end of the contest year. The complete list of event and rules for model rocketry may be found in the NAR "United States Model Rocket Sporting Code," also known as the 'Pink Book.' It is available free to NAR members, and may be ordered from NARTS. Some of the event types are:

Altitude (1/4A - G) - The purpose is to get the maximum altitude from a model using a specified class of engine.

Streamer Duration (1/4A - G) - The purpose is to get the maximum flight duration from a model with a specified engine type using streamer recovery.

Parachute Duration (1/4A - C) - The purpose is to get the maximum flight duration from a model using a specified motor type.

Eggloft Altitude/Duration (B - G) - In this event the competitor must launch either one to two large raw hen's eggs, depending on engine type and specific event, and recover it/them, intact, crack-free. The goal is either to reach the highest altitude or have the longest duration flight, depending on the event.

Rocket Glider and Boost Glider Duration (1/4A - G) - In these events the competitor launches a glider using a rocket engine and tries to achieve the longest flight duration of the glider. In boost glider the pod containing the motor may be ejected and recovered separately. In rocket glider all parts, including the expended engine, must stay with the model. Rocket glider is considered to be the more difficult event because the model must be both a rocket and a glider without loosing any parts. The CG and CP requirements for the two phases of flight are very different. See Part 08 of this FAQ.

Helicopter Duration (1/4A - G) - In these events the model ascends as a rocket. Rotor arms then extend by some mechanism and the rocket slowly descends like a helicopter which has lost power.

Payload Altitude (A - G) - In these events the competitor must launch one or more standard NAR payloads (1 ounce each of fine sand) and recover the model. The number of payloads increases with larger engine sizes.

SuperRoc Altitude/Duration (1/4A - G) - These events are for rockets that have a minimum and maximum length requirement based on engine class (0.25 - 4.5 meters). There are both altitude and duration variations. The trick to these events is that the model may not bend or crimp during flight.

Scale Events (also see - These are craftsmanship events where competitors build scale models of real military or commercial rockets. Fine craftsmanship is emphasized.

* Scale: exact replicas of rockets, with major scale dimensions verified by judges.

* Sport Scale: adherence to scale is judged from a distance of 1 meter.

* Peanut Scale: Sport Scale for small models (<30cm long or <2cm dia.)

* Giant Scale: Sport Scale for large models (>100cm long or >10cm dia.)

* Super Scale: must include a scale launcher as well as model of rocket; judged same as scale

* Space Systems: Sport Scale model and optional launch complex. Model must complete a predetermined mission with the purpose of duplicating in miniature the full-scale operation of the prototype.

Plastic Model Conversion (PMC) - This event is either loved or hated. Competitors enter plastic models of rockets or other aero-vehicles that have been converted to fly as model rockets.

Precision Events - These include spot landing, random duration, predicted duration, precision duration, and predicted altitude.

Drag Race - Multi-round, elimination tournament where contestants gets points for:
* FIRST lift off
* LOWEST altitude
* LAST to land

Research and Development - A non-flying event where contestants enter results of research projects. Entries are judged for completeness, contribution to rocketry knowledge, degree of difficulty, etc.

The Tripoli "Member's Handbook" currently lists competitive events for high power models. These events are basically altitude record setting events within a given motor power range (F through O).

9.3 Strategy & Tactics - What are some good events to try when first getting into competition? Any 'sage' advice?

9.3.a From Buzz McDermott

I just started competition this year. I must have asked 30 experienced competitors where to start. I got 30 COMPLETELY DIFFERENT ANSWERS!! They ranged from 'keep it REAL simple' to 'try everything'. Here is a summary of the most prevalent advice. It seems to have worked for me.

- Competition requires a large stable of rockets, given all the possible events and engine categories; start with some of the simpler ones where a single model might be competitive in more than one event (for example, the same model might be used for 1/2A-A streamer or parachute duration, another model might be competitive in any of A - C streamer or chute duration)

- Try single eggloft (B-C, duration or altitude) before trying the multi-egg categories (such as D or E dual egg).

- Go for a good, qualified flight first; then decide if 'going for broke' is appropriate on your second flight (this is for multi-flight events).

- Get a teammate and enter as a team. There are too many models you need to compete to be able to build all of them your first year. Entering as a team let's you pool time, talent, experience, and models.

- Don't get discouraged if you aren't immediately competitive. Remember, the main goal is to enjoy yourself and HAVE SOME FUN. If you are new at this, you're going to learn A LOT about rocketry by doing it the fun way.

- KEEP A LOG OF ALL FLIGHTS. RECORD WHAT WORKS AND WHAT DOESN'T. NOTE YOUR FLIGHT TIMES, ALTITUDES, ETC. Your biggest weapon in many events is in being able to predict how your models will perform.

- Make a model preparation checklist for each event (i.e., a detailed, step-by-step list of everything necessary to prep the model). Use this list for your first few competitions. Comp models are often prepared a little differently from sport models. The difference between winning and losing is often just attention to detail, or lack of it, in the heat of competition.

9.3.b From Mark Bundick

Note: This is a condensed version of some competition strategies for individual and team competitors, written by Mark 'Bunny' Bundick and posted to r.m.r. Check the r.m.r archive server for the complete posting. The full posting points out that there are many ways to win, and the following is just what has worked for some individuals.

Some Individual Competition Strategies:

(a) Read the Pink Book. If you don't know the rules for the event, you can't know how to win and how to improve. Figure out the scoring for each event, how many flights are allowed, required number of returned flights, the reasons for disqualification, etc. Reading the rules will also give you some insights into how the contest will be run. Start with the general rules then review the event-specific rules.

(b) Practice for all events where your experience is low. If you already know how to fly parachute duration (PD), don't waste time practicing that at your club's sport launch. Instead, suppose you don't do well in streamer duration (SD). Build a couple different SD models with different streamers, and fly each of them at least a couple of times BEFORE the contest. Take a notebook to the field and write down what happened, or at least write it down after you get back home. Such notebooks can be the lifeblood of your competition model and strategy development.

(c) Improve one event a year. At the start of the season, it helps if you pick one of your weak events for special attention during the year. Review the existing models and strategies for the event, look over the competition carefully during the contest year, and practice this key event each and every sport launch or test flying session you attend.

(d) Strive for consistent flights. Rob Justis, my old teammate from the 70's, always reviewed our DQ's after the meet and separated them into "DQ's for the right reason" i.e no return, and "DQ's for the wrong reason", i.e. separation. We strove to avoid the latter obviously. This made us terribly consistent, and with today's "two flights count" rule, this is even more important.

(e) Fly all the events. Sounds simple, but many people don't do this. You don't have to win the event, but if you don't fly it, you're sure to get behind because you're conceding flight points right off the bat to your competition. Over the course of a contest year, you can concede 10% of your yearly total this way.

(f) Concentrate on events with high individual event weighing factors (WF). If you have to choose events to fly, or are short of preparation time for some of the scheduled events, prepare for and fly the highest WF events first. Simple again right? But how many people go to a contest and fly PD first thing in the AM cause the wind is calm, and ignore BG which has a WF two to three times that of PD?

(g) Refine, don't abandon, your models and strategies. Rarely do you get super performance improvements from forgetting all you know to adopt a totally different strategy. I've seen so many people hop onto a design when it didn't fit their flying style and then get burned. They switch because some guy had a super performance at a contest, so he must have the "Holy Grail" of models. Right after Tom Beach placed highly at a NARAM with a flexie RG, I saw lots of folks try them, and crash. Tom had lots of flexie experience that helped, and when regular BG flyers tried to adopt his style without the background, BOOM! If you're serious about switching to a completely different model, say from swing wings to slide wing rocket gliders, then take the time to practice, practice, practice and build up the background in the new method. There are no quick fixes to the winner's circle.

(h) Pick your contests carefully. If you can't fly helicopter duration (HD) all that well, and the next regional you plan to attend has two HD events, find another contest! Sometimes, this isn't possible. But if two contests compete for your participation at the same time, take the one that has more of your "strong" events.

(i) Casting Your Bread: Share what you've learned with others. A three time national champion who shall remain nameless positively stomped every challenger in his sight. But his desire for keeping secrets and his unwillingness to share left him with few friends, and after a brief time, he left our hobby, poorer himself and leaving our hobby poorer for failing to let us learn from him. The benefits of making new friends and sharing far outweigh any short term competitive advantage you might think you have from being secretive. As a quotation I once read went "We have all drunk from wells we did not dig and been warmed by fires we did not build." So go ahead. Cast your bread on the waters. You won't be sorry.

Hope this provides you competition types some food for thought. I'd love to hear from anyone with comments, questions, brickbats, etc.

9.3.c From Dan Wolf

...I am amazed at the number of people who attend a NARAM as their FIRST contest and expect to have any kind of chance of placing. NARAM is, after all, the National Championships. It would be like an expansion team in football winning the Super Bowl or at least making the playoffs. It isn't going to happen and unless the person has done some other kind of preparation, it shouldn't. That's one of the reasons there are NAR sanctioned contests held all over the country within a reasonable drive of most people. Novices should start out competing at the local, open and then regional meet levels. Chances are if they do, two things will happen. First, they will win something. The meets are smaller and the competition not nearly as tough as at NARAM. Second, they will learn a lot about competition strategy, what works, what doesn't, etc. I attended probably about a dozen contests before I attended a NARAM. I recall years ago asking people at contests if they were going to go to NARAM and hearing, "No, I'm not ready yet." We all knew that we had to pay our dues before working ourselves up to the majors.

Today, more and more, people don't want to toil away at the local, open and regional levels to work themselves up into NARAM quality competitors. For many, NARAM IS there introduction to competition. I think the idea of a novice division, at least at NARAM, thus has some merit, if that's what it takes to bring NARAMs back to the 300 competitor attendance level.

9.4 Specifics

9.4.a Getting Jump Started

From Jeff Vincent:

>I need a set of competition rocket plans Altitude, Streamer, Parachute can
>anyone suggest a site or a rocket for these events

Generally speaking, these events are fairly simple, and thus you don't see as many plans published. Many simple kits ("3FNC" - 3 fins and a nose cone) can be adapted to these events.

In general, you want a minimum diameter model (same tube diameter as engine), at least 10:1 length:diameter (more if necessary to hold your recovery device). Rounded nose cone. Three trapezoidal fins with approximate dimensions: root - 1.5 dia, tip - 0.75 dia, span - 2 dia (dia equals tube diameter). Checking stability before flying (finding the CP with VCP for instance) is a good idea.

The duration models will have a thin shock cord (squid line or kevlar) attached to one fin root (aka external shock cord). Launch guidance can be provided by a tower or launch rod, piston launching optional. Finishing should be minimal to give a smooth surface with minimal added weight. Streamer will be a mylar streamer, ranging from 3x30" to 8x80" (or more). Thicker, stiffer mylar is usually better, pleats ironed into the unattached end of the streamer help. Parachute will be thin dry-cleaners bag or painter's drop cloth (0.25 mil or so), with 8-16 light shroud lines, colored with magic marker, and dusted with talcum powder. 'Chute sizes range from 12" to maybe 30" (chosen as much for maximum duration as for feasability of recovery).

The altitude models will have a very slick finish (I use an automotive primer polished with fine steel wool on a drill-lathe). Definitely an internal shock cord as conventional models. Launch guidance should be a tower, and a piston launcher is recommended for black powder motors. Recovery by a small (for fast descent) but visible mylar streamer (go more for length than width). Use powdered chalk or dry tempera paint as tracking powder (provides a "mark" for the trackers at ejection). In small diameter models, placing the TP in a paper pouch aids deployment.

If you want to specify engine class, I can be more specific on model and recovery device sizes. Also, some companies (QCR comes to mind) offer good kits (provides plans and saves you the trouble of chasing down parts from diverse sources).

9.4.b What is a 'piston' launcher? Does it really help?

From Roger Wilfong:

Pistons offer several advantages and a couple of hassles.

+ 1) They eliminate the need for launch lugs and therefore reduce drag.

+ 2) They keep ignition leads from fouling in glider wings.

+ 3) They can increase lift off velocity (see below).

+ 4) They recover an otherwise lost portion of the whoosh generator's impulse.

- 1) They require additional maintenance.

- 2) Ignition can be a hassle.

A launch piston is usually made of cylinder of 12-18" of BT-5 or PT-13 and a fixed piston made of an old 13mm motor casing or brass tubing. In practice, the support shaft is attached to a tripod or other launcher, an igniter is inserted into the tubing on the top of the piston. The bottom 1/4" of the motor in the model is friction fitted to the top of the piston tube and lowered onto the igniter (I use 2-3 short pieces of thin 1/4" masking tape across the joint of the piston/body tube to reinforce the friction fit - actually I've found it easier to use a looser fit and the masking tape than to get just the right friction fit). The micro clips of a launch controller are attached to the bare ends of the zip cord. When the motor ignites, exhaust gas pressurizes the cylinder and pushes the piston down. Since the piston is fixed, the effect is that the cylinder is pushed up. When the stop ring at the bottom of the cylinder hits the bottom of the head, the cylinder stops and the model pops off the cylinder.

In effect the piston has acted as the launch lug for the fist 12-18" of motion.

Roger's Piston Theory (developed through observation and tinkering, it is not based on a mathematical analysis):

For performance events, pistons offer an advantage over launch lugs or towers primarily because they convert an otherwise unusable portion of motors total impulse into motion. There is a startup time at the beginning of the burn where the motor is not producing enough thrust to lift the rocket - it is this portion of the burn that the piston is making use of.

Since the piston gets the model moving before the motor generates enough thrust to lift the model, it is possible that at the instant of separation, the motor may no be developing sufficient thrust to keep accelerating the model and the model may decelerate for the next few feet after leaving the launcher. This is not a problem for PD/SD models and most gliders - they are typically light enough that the piston has accelerated them to a high enough speed for the fins to work properly; however, it can be a real problem for payloaders and egglofters (I have seen egglofters almost come to a stand still after leaving a short piston). So for heavier models, a piston/tower combination provides additional guidance and helps prevent tip off.

The tower is of only small advantage with SD/PD models; however, it can help if there are other disturbing forces at separation that could cause the model to tip.

Because they affect the gas flow during the ignition of the motor, pistons don't work well with composite motors. My experience has been that composites either cato or chuff when used with a piston. (If someone has worked out using a composite on a piston, how did you get it to work?)

Pistons are a real advantage in any performance event. For eggloft and payload, they typically allow you to use the next longest delay. For instance, a B6-2 is needed for a conventional eggloft model. On an 18" piston, a B6-4 ejects at apogee. Earlier I referred to using a piston on a Big Bertha - an A8-3 gives a marginal flight without the piston; with the piston, ejection is at apogee.

There are a couple of variations and modifications to conventional pistons that can further enhance their performance. The diameter of the head (6, 13, 18 and 24mm) is one parameter to play with. Jeff Vincent and Chuck Weiss presented a floating head piston as an R&D project at NARAM-28 that further increased performance.

9.4.c Wire Loops

From Jack Hagerty:

...There was a great debate a few years back as to the amount of parasitic aero drag that comes from a launch lug (hence tower launchers, pop-off lugs, etc.). The lug essentially stagnates and looks like a solid piece only with turbulence inside. A friend of mine who's an aero engineer with NASA at Dryden told me that if you can keep the length/diameter ratio short, then the air will pass through with very little drag. "How short?" I asked. "About 1/4," he said. That means in order to have no drag, the lug length has to be less than 1/4 of the diameter. For a 1/8" rod this means a length of no more than 1/32". This is, of course, impossible using a conventional fiber lug, but 1/32" is .031"...

9.4.d Pop Lugs - A CMR pop lug described

From Fred Schecter:

A long lug (2 inches at least) or two smaller pieces of lug glued to along standoff (the standoff is long in length, but does not stand off from the rocket very far).

The standoff has bent/formed music wire epoxied to the top and bottom. The bottom piece forms a little "U" shape that captures the lower lip of the rocket body tube. The top piece is a flattened "V" (almost a point) and it is angled slightly toward the rocket. This top piece is inserted through a tiny hole in the body tube.

The entire rocket can sit on the lug while on the rod (that's why you have the lower "U"). You apply a few wraps of masking tape to the top of the launch rod and when the rocket takes off, it slides up the rod until the lug hits the tape, The lug stops ("POPS OFF") but the rocket keeps going straight since it has built up enough speed to fly stably.

The top pin MUST FIT SNUG!!!!! Otherwise it will pop off at ignition. That would be bad.

9.4.e Flying Naked

From Dan Wolf:

>I am putting together a few rockets with competition in mind, and
>having never been to a rocket competition before, I have a few questions.
>Do people generally paint competition rockets? If so, what kind of
>paint is used, and does performance increase due to smoother surfaces
>or decrease due to added weight?
>And if people don't paint their competition rockets, do they generally
>seal the fins for more laminar flow (this assumes balsa instead of
>Finally, what about gliders? Do people paint/dope them or just seal
>them, or neither?

Many competition rockets these days go unpainted, particularly in duration events where the models often end up thermaling away. Also, a lot depends on the materials used. Fiberglass and vellum body tube rockets are rarely painted (although sometimes fiberglass models are made with colored die added to the resin). Blackshaft tubing is still used somewhat and it is usually not painted. If the body tube is a conventional Estes type, some competitors will color it with "Magic Marker" if anything. For duration, the preference is to go for reduced weight other than a smoother finish. For altitude, the trick is to do both. Fins on unpainted rockets are often flown unfinished, or finsihed with a couple of coats of clear dope (sanded smooth).

Gliders are rarely painted these days. Either magic marker is used to color them, particularly the underside of the wings (black marker) for visibility. Or, the glider is tissued with lightweight tissue (ie. Jap tissue). This adds strength with a minimal weight penalty and also increases visibility and makes it easier to trim (the tissued stab surfaces can be more easily warped into position on the field).

9.4.f Regarding Streamers

9.4.f.1 Streamers Part 1

From John DeMar:

> What are some of the ways that you have used to attach mylar streamers
> to Kevlar shock cord? The mylar tears really easily so I am afraid to
> punch a hole in it. Also any suggestions on folding the streamer? Is
> this legal in NAR competitions? The "pink book" rules seem rather vague.
> I would like to enter a streamer duration contest for fun, but I haven't
> done streamers before. Any suggestions would be most appreciated.

To attach the Kevlar shock cord to the streamer, use a piece of thin steel wire (music wire) or nylon fishing line. Tape this about 1/2" from the end, parallel to the end (ie: 5" long wire for a 5" wide streamer). Fold the end over the wire and tape again. Then, punch a small hole just above the wire and reinforce the hole with strong tape. Tie the kevlar through the whole and around the internal wire with a couple of strong knots. Put a touch of CyA glue on the knot if you'd like to make sure it doesn't come off.

The "pink book" doesn't say anything about folding, but you need to use a single continuous piece of streamer material. Folding has been the subject of many NAR R&D reports and everyone has their own ideas on what is best. For small streamers, A 1/2" accordian fold for about 1/2 the length works well for me. This can be rolled up nicely into a 13mm tube.

For larger streamers, some people have had good luck with a slight zig-zag fold for most of the length, but it needs a bigger body tube. The goal of this type of fold is to get a draggier whipping action.

9.4.f.2 Streamers Part 2

From Kevin Kuczek:

First I reinforce the end I plan to tie the streamer onto with 1/2" mylar tape (from ASP) folded over so you have 1/4" on each side. Next, I tie a small 1" loop in the kevlar, pass a piece of clear packaging tape through the loop then apply it to a corner on the streamer- one half of the packaging tape gets applied to one side,the other half to the opposite side. Need to made sure you get the packaging tape that stretches and is can't be torn vs. the mylar/polyester type that does not stretch and is easy to tear.

9.4.f.3 Streamers Part 3

From Bob Kaplow:

...folding and pleating the streamer is legal. In fact it's standard practice. But quarter mil and even half mil parachute mylar just doesn't pleat well. For best results, you need to find about 1 mil mylar. The old Ed LaCroix Apogee used to sell it. I don't know of a current source. If any one else does, please say so.

The heavier mylar doesn't tear as easy as the quarter mil stuff. What I do with either mylar or tissue (I still use drafting tissue for most of my competition streamers) is to tape the Kevlar to the streamer at a 45 degree angle from one corner. Use the magic yellow tape that Ring Rocketry sells. I tie several knots in the Kevlar first, to keep it from pulling out, and if possible, fray the Kevlar end to increase the contact area.

I also reinforce both the leading edge and the side of the streamer at the attachment point with another piece of tape. And for the tissue, I also put a piece of tape on the BACK side, to prevent it from tearing through the tissue.

I use a very long Kevlar shock cord, longer than the streamer. I also bungee it with a piece of sewing elastic that is designed to break in use. That absorbs the ejection energy. Replace after every flight.

9.4.f.4 Streamers Part 4

From George Gassaway:

>>>I'm planning on doing some tests on optimizing streamer duration. The conventional wisdom favors micafilm, with 1/2" to 3/4" accordian pleats over 3/4 length. I would like to investigate different materials and pleating techniques. If you have other materials or techniques you favor, I would appreciate hearing about them, so that my tests can be as complete as possible.<<<

Well, as for folding techniques, sure. There's a fold I call "Scorpion's Tail", because the streamer deflects to one side, curled sort of like an attacking Scorpion. The theory is that by the streamer being curled like that, the upper part grabs into the air and flaps around more than an accordion fold does.

The best thing is how relatively easy it is to do compared to making accordion folds. Roll the streamer up on a 1/4-3/8" diameter dowel, then squash it flat and iron it to set the folds. Now for really small diameter models it's not so easy to do that, you'd need less than 1/4" dowel to do a streamer for an 11mm diameter model, since once it's flattened and so forth it would be too big to fit inside the tube. But you get the idea.

And to add another kink, literally, is the idea for double-scorpion fold. Before rolling the streamer up, first fold the top 6" or 12" down, and then do the rolling and flattening. The result is an "S" curve to the streamer.

Another fold, long-forgotten, was the helix fold that Ken Mizoi had a lot of luck with. He did a normal accordion type of fold, and then with it folded up he did a diagonal fold from say the upper left to lower right corner as seen with the whole streamer folded up (NOT deployed). That made the streamer have a helical twist to it when deployed.

I suspect that the optimum fold is out there somewhere that might involve quite and odd mix of the above. Say a double-scorpion fold at the top with an accordion helical fold? And whatever is perfect for one streamer material probably would not work so well for another type and may tend to be very size and mass-specific. So, be sure to identify exactly what kind of model would be used, and base the test streamer sizes and simulated model mass (or actual models) accordingly.

9.4.g Super Roc Duration

From George Gassaway

>>>>I've got a competition coming up soon with... super-roc duration. Any suggestions on what's worked well for you in the past....<<<<

Just remember it's DURATION. So, don't go building something that is on the edge structurally as is typical in Superroc Altitude, this event is not typically won by the highest-flying model.

So, more main body diameter for a long length, less smaller diameter stuff on top. The more of a very small diameter tube you have on top, the more it can deflect like a canard to either make the model go off course or simply make it buckle/shred on boost. Just no reason to get that close to the edge for Duration.

Also it helps to have room to store a decent sized chute. After all this is not a Superroc event that happens to be timed, it is an interesting mix of superroc with Parachute Duration. Don't overlook the Parachute Duration part of it. Well, OK, technically you can use any recovery system for Superroc Duration but parachute recovery is the most practical way to go.

9.4.h Flex Wings

From George Gassaway:

(Note - This really belongs in the glider FAQs but over there, may end up missing ;-)

>>>I'm not getting enough billowing in back (that is, the covering is not loose enough), with the result that the thing dives (not enough incidence between front and back). How do I cut and mount the covering in such a way that it's tight in front but loose in back?..."<<<

Well, ready to learn? :-)

I was fortunate that early on when I used to apply the plastic to spars by stitching it on, something about the process made it tight in front but billowed in the back. Later when using thinned contact cement to attach the plastic to the spars, and laying the plastic down tight across a building board, it didn't produce the same effect.

The trick I use to force the correct amount of billow is to use some very sticky but thin and flexible tape. Originally that was the CMR adhesive mylar, but that's been gone for a long time now (Ah yes, there is adhesive mylar around the hobby but none that is as thin and sticky as CMR's was). So I use strips cut from band-aids (also that's what I use to apply shroud lines that I used to use CMR adhesive mylar for).

I apply a small strip to the top of the plastic, near the edge of a side spar, at around 1/4 of the distance back from the nose. So for a flex-wing with 12" spars, that would be about 3". I use the tape to pull the plastic taut, towards the spar, so that the front part of the plastic is taut but the rear part billows. The amount of billow at the rear depends on how much you make the front taut using this method.

BTW - first prepare the area for the tape, by wiping away from that area any talcum powder you may already have applied to the plastic. I do the left and right side, but do not stick the other side of the tape down until after making some test glides to see if the billow is about right. By the other side of the tape, what I mean is that once you are sure the tautness is right, then you'll curl the tape completely over the spar and stick the tape to the bottom side of the plastic. But as I say, do not do that yet, as it is almost impossible to peel the tape off to make adjustments later.

So, just test glide it indoors. If it stalls a lot, try adding a bit of noseweight. However usualy a LOT of stalling indicates there is too much billow, so you'll need to adjust the tautness. If it glides OK, try the acid test. Hold it almost straight down and let go. If it starts to pull out of a dive, then you're OK. If it flutters and dives down, then you'll have to try increasing the tautness.

Keep making adjustments until "you learn how to do it, or something like that".

When it is right, then curl the tape around the spar and stick it to the bottom of the plastic too. And give it all another dusting of talcum powder so that any stray adhesive won't stick to anything it should not be sticking to.

9.4.i.1 Tracking Powder Part 1

From Kevin Kuczek:

> Can someone tell me what "tracking powder" is made of? Can it be added to a
> single use motor to help in seeing the ejection? I have seen references for
> it but nothing to explain what it is.

The BEST tracking powder is epoxy paint pigment. It is used by all US team FAI altitude and scale altitude flyers. Better than chalk, better than powdered tempura. When deployed, the clouds are very, very dense and most importantly, linger for a few seconds so that trackers have a greater chance of homing in on it. You can purchase at It's not cheap by any means, but the results are well worth it.

9.4.i.2 Tracking Powder Part 2 (How to Pack It)

From Jeff Vincent:

>... but WHERE do you put the stuff? In the ejection charge or in a cup somewhere...?

Conventional wisdom is to just dump it in, between the wadding and the recovery device (that way when you see the cloud, you know your 'chute is out, even if you can't see it). As you get into smaller models (18mm tube diameter or smaller), skin friction (with the inner tube wall) starts to become a problem.

My practice is to make a small pouch with the old MRC wadding (consistency is similar to silkspan). You will form the pouch around a dowel just a bit smaller than the tube ID. Cut a piece wide enough to make just over one revolution around the tube. Wrap the wadding around the dowel, fold over the bottom end, slide it most of the way into the body tube, *then* remove the dowel. While holding onto the top edge of the pouch, fill it with tracking powder. Once full, crimp/twist the upper end shut, drop into the tube, and load your recovery device.

9.4.j Packing Large Chutes

From Wolfram v. Kiparski:

> What do most of you feel is the best way to fold 0.5 and 0.25 mil mylar
> 'chutes? I am primarily interested in strategies for low opening shock
> for Egglofters.

On a flat surface dusted liberally with talcum powder, lay out your parachute flat. Dust it with talcum powder. Fold it in half to make a semicircle. Make sure the shroud lines are lined up on top of each other. Dust with talcum powder again. Remember, before you fold, dust with powder. Now take one "corner" of the semicircle, and fold the chute halfway. You're not folding it in half again! If one "corner" is at 0 degrees, and the other is at 180 degrees, bring one corner over to 90 degrees - halfway. Now carefully flip the whole chute over, and fold the other "corner" over like you did on the other side. Examine it until you notice that you have folded the chute into an "S" shape. See? Repeat this process again and again until you can't stand it any longer. Remember to dust with powder before folding. When you are finished folding, the whole chute should be folded in zig-zag pleats. The object of doing this is so that no folds are trapped inside of another fold. To finish up, fold the chute lengthwise two or three times, and wrap the shroud lines carefully around the bundle. Parachutes folded this way open very quickly when released. Try it at home a few times to get the hang of it. Practice.

This technique was taught to me by Chuck Weiss. I later read an article in an old "Model Rocketeer" written by Chris Tavares that described the same technique.

9.4.k Tandems

From Jeff Vincent, Chas Russell & Brett Buck:

(Note - This one belongs with the Gliders, is not a FAQ, but sorta interesting)

> >>What ever became of the practice of epoxying a
> >>mini-motor (13mm) into the top of a standard size (18mm)
> >>booster motor to kick it into the next impulse range?
> >>Example - C6-0 with an A3-4T sustainer.

Verboten within a year or so of its origin (late '70s). Thus the "do not permanently attach anything to a casing" rule in the Pink Book.

"Tandems" got their start in California, as far as I know, in the ' '70,s. A couple of guys in the Bay area were flying the Estes Skyraider on a D12-0/D12-7 epoxied together in a BT-50. Really were neat. Static testing showed that some performance increase was obtained from all of the extra mass eroded from the booster motor. However, the fine people in Penrose (fine compared to the current crew) decided that tandems did not meet the test of using the product "as intended". Read liability issues. The NAR concurred and the tandems had a short lived history. The later availability of composites made the point essentially moot. I had flown a few prior to the boom being lowered..

... my cohorts and I were flying tandems in 73-74 time frame in central Kentucky ( about when Centuri Mini-Engines first came out ). Never heard of mixed tandems, though, like a C6-0/A3-4T. I always figured that using the wrong sized nozzle for the upper engine - a C6 nozzle is much bigger than an A3 - wuoldn't work. . Plenty of people had the idea of weakly gluing them together for conventional staging, since they telescope so nicely. I assume that one failure to separate would plant the idea.

I guess now that we can glue stuff to motor casings again, tandems are A-OK ;-).

9.4.l Helicopter design

From Tim Van Milligan:

> I've been meaning to ask for a long time, why does everyone use front-hinged
> blades? It would seem that the struggle to pull them out against the aero
> would be enough of a disincentive that people would start hinging them at the
> back instead.

It really doesn't matter where the hinge is. The basic problem with rear-mounted hinges is strength. That is; they need to be made stronger than front-mounted blades.

With rear mounted blades, it is likely that the model will deploy when the rocket is moving in a forward direction. This really aids the deployment. But when the speed is high (like when the model is arcing over), the forces on the blades can be very significant. This may cause them to snap off. The higher the aspect ratio, the greater the problem. The Estes Skywinder, which I designed, solves this problem by having a strong hinge, and flexible blades.

I've made balsa wood versions of the skywinder (see the photograph in the Model Rocket Design and Construction book on page 87). But when flying this model, it is really necessary to make sure it doesn't arc over, and that the blades deploy near apogee.

As you mentioned, front mounted blades have the opposite problem. If the model is moving forward, the blades have a struggle to open against the airflow that is trying to hold them down. They also need to be flown so that they don't arc over and deploy near apogee. To solve this problem, what I like to do is have the model separate (but still held together by a shock cord), so that it will instantly slow down so that the blades can open when the model is traveling slower.

So basically, it depends on your own preferences. But when you design the model, you need to make sure that it can safely deploy when it is arcing over.

9.4.m Optimal Thrust (very shortened version of a hotly debated topic)

From Alan Jones:


To a very good approximation, optimal thrust for a model rocket (or HPR rocket) is T = 2W. That is, you thrust at maximum (ideally just an impulse) until you reach the velocity where drag = weight, thrust at 2W until fuel is exhausted, and coast to appogee. The interesting part is that the optimal sustaining thrust level is not very dependant on Cd.

9.5 Aside from hanging around 'old timers', how can I learn more about competition strategies and techniques without re-inventing the wheel many times over?

The best place to start looking would be the NAR Technical Services (NARTS) catalog. NARTS has several documents of particular interest to competitors. The NARTS catalog can be browsed at the NAR web site - Look for the NARTS catalog, and when browsing through it, look for these titles:

US Record Setting Designs

CMASS Plan Book

MIT Competition Notebook

Journals of the MIT Rocket Society...

Proceedings of the MIT Model Rocket Conventions...

NAR Technical Reviews, Volumes 1 - 7

Boost Glider Analysis-"A Free Flight Method For Boost Glider Analysis."

Streamer Duration Optimization

Basic Design Rules for Boost and Rocket Gliders

Another great place to find information is on the internet where you can do keyword searches at places such as Deja/Google. Be sure and check out the various on-line club newsletters available as the various contest reports also contain useful information.

9.6 Tripoli Altitude Records

Tripoli altititude competition records can be viewed using your web browser at:

Buzzing through the Tripoli web site, it appears that the organization has been refining the events to include Open, Hybrid, Restricted and Large Rocket altitude categories. Gone are the duration (makes good sense) and cluster events.

9.7 NAR Competition Records

NAR competition records can be viewed using your web browser at:

9.8 Some Unofficial High Power Altitude Attempts

Some of the high power records come by way of a posting from Chip Wuerz ( Chip is part of the University of Central Florida's high altitude rocketry project. Additional information has been taken from several issues of _Tripolitan_/_High Power Rocketry_ magazine.

(Ed. Note - Not quite sure how to handle these so I'm just leaving them in. These records have been since beaten but given the advances in technology, the following recognition seems noteworthy)

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

---Top altitude holders:

Altitude: 27,576 (altitude by Adept altimeter)
Set by: Pius Morozumi
Event: Black Rock V, Black Rock Dry Lakebed
Date: July 16-18, 1993
Altitude: 24,771 feet (11.7% tracking error)
Set by: Chuck Rogers and Corey Kline
Event: Lucerne Dry Lake Bed, Lucerne, Ca.
Date June 1989, USXRL-89
Altitude: 24,662 (tracking error unknown)
Set by: Tom Binford
Event: LDRS XI, Black Rock Dry Lake Bed, Nevada
Date: August 16, 1992
Altitude: 22,211 feet (5.3% tracking error)
Set by: University of Central Florida
Event: LDRS X, Black Rock Dry Lake Bed, Gerlach, NV.
Date: August 1991

-- Highest tracked flight at LDRS-X / BALLS 1, 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.

9.9 Biggest Non-metallic Rocket Flights

Rocket: Down Right Ignorant
Weight: 800 pounds +
Set by: Dennis Lamonthe, Chuck Sackett, and Mike Ward
Where: BlackRock Dry Lake Bed, Gerlach, NV.
When: August 17, 1992, FireBALLS experimental launch
What: Super scale based on Esoteric rocket designed by Ron Schultz
Height: 34' 7"
Diameter: 24"
Power: 1 O-class custom motor
5 Energon L1100 motors
8 ISP K1100 motors (around 76,000 NS total impulse)
Materials: 24" fiberglass tubes for main body tube
1/8" aluminum plates for coupler bases and fin mounting boxes
1/2" aluminum plate for motor thrust plate
2x5" oak boards for tube coupler assemblies
2x5" pine boards for body tube strengthening
plywood centering rings
3/4" birch fins
14" paper tubing for upper body tube
hard resin/fiberglass nose cone (originally a sounding rocket nose cone shroud)

(Note: The definition of 'non-metallic' traditionally has meant 'no substantial metal components' as well as no structural components being metal. DRI appears to push that definition to its absolute limit, or a little beyond.

9.10 Other Non-professional Flights of Note

Rocket: Frank Kosdon metal rocket
Where: Argonia, Kansas
When: 15 August 1993
Power: Kosdon non-certified O10000 (that's O-10,000)
Materials: All metal rocket with custom manufactured motor
Altitude: 35,407 feet AGL; closed optical track

(Notes: This is a special-case flight. The rocket does not follow the rules for high power because metallic rockets are expressly prohibited by both the NAR and Tripoli. It also uses a custom made motor. The motor was made by a manufacturer with other high power motors certified by Tripoli. It was pre-manufactured and solid propellant, within the total NS limits of high power consumer rockets.

Tripoli does not recognize this flight, or any other flight, for altitude record purposes unless a successful deployment of the recovery system is observed or the rocket can be recovered to show successful recovery system deployment.

9.11 Some other highest verified altitudes

For the most current list of highest flying altitude records, stop by for the list maintained by Robert (Bobby) Gormley.

9.12 The Best of the BMWQF

From Bob Kaplow:

(Note - This isn't really a FAQ but a favorite of mine. AE)

The all time classic has to be Bob Sanford's Best MidWest Qualified Flight winner at NARAM-29. We were flying B Eggloft (don't recall off hand if it was altitude or duration). He came to the checkin desk with a model and pre-taped motor. All the Check in officer (Ric Gaff) could see because of the tape was the "6-2", but being a nice guy, Ric let him thru, and wrote "B6-2" on the flight card. Well, the model just barely cleared the rod and pranged. Upon post flight examination, under the tape where the "B" should have been was...


9.13 Do's and Don'ts

(Overheard from John DeMar and Bob Kaplow):

* Don't forget to remove the masking tape that you used to hold down your helicopter rotors while attaching the thread. Makes it real hard for those rotors to deploy!

... and it's cousin, the tape on the BG pod, and the rubber band on the chute. Also don't forget to hook up the rubber band on the HD / BG / RG or it won't deploy at all.

* Don't open an egglofter OVER the check-in table.

...But don't bother with a bag either. If the egg breaks, the bag usually breaks too. Better concentrate your efforts on not breaking the egg than in controlling the mess. Besides, a bag just says that you don't have faith in your abilities.

* Don't let Apogee Blackshaft(tm) tubing land on aluminum bleachers, especially 2.5 meters of it coming down sideways. Especially at NARAM!

...Never paint a superroc black. The black warps in the sun. A 6' long banana shaped rocket flies a banana shaped arc thru the sky, often intersecting with the ground plane :-(

* Don't run after long-drifting models through dairy farm fields without looking down occassionally. There are obvious obstacles (eyu!), but the old barbed wire across the shins is more painful!

And the random holes can really twist an ankle.

And never go anywhere where there is something that wants to EAT YOU! In Florida at NARAM-24, this includes both fire ants and gators.

* Don't miss a chance to argue with Pink Book Lawyers, especially when your boost glider carries 20ft of igniter cables with it, lands on the ground still attached to the clips. Yes, it leave the launcher and an official flight! ;)

What? *ME* argue with someone over the rules? You must be mistaken!

* Don't forget sunscreen.

...and now that the hairline is receding, the hat. Sunglasses too. And bug repellent where appropriate.

* Don't catch models that must be allowed to land (eggloft, payload, scale, pmc). Worse, don't let some other urchin catch yours, then fall on it. DO be right there when it lands, so you can grab it the instant it is down. I've had several rockets damaged when they blew across the field after landing, including a HPR model at Danville that used the tube as a shovel, filling up with 2' of mud after dragging itself across state lines!

* Don't fly your NARAM models in that local contest a month earlier. I remember a contest at the Michigan Space Center in 1987. I lost 4 models that weekend that were ALL needed for NARAM. One was a record setting D RG that I flew in B RG, but thermalled away anyway. Another was a B ELD model that was last seen going up! Things that you just don't expect to lose at all.

* Don't fly an F7 in ANYTHING! If it doesn't blow up it will be unstable!

* Don't even bother entering PMC!

Copyright (c) 1996, 1997, 2001 Compiled by Buzz McDermott, Wolfram von Kiparski, and Andy Eng. Written by the rec.models.rockets community.

Refer to Part 00 for the full copyright notice.