Friday, 30 June 2017 23:10

LOC Precision

MoonRockets1 300x146LOC PRECISION was acquired by Barry Lynch in 2000 from Ron Schultz of Ohio. Over the next 16 years Barry took LOC to the next level by investing in LOC to do moreā€¦.fly higher, more affordably and added touches of modern day quality. What Barry has given to LOC, he set industry standards for others to follow. Expanding the company to do more for education, youth and investing in the next generation of HPR flyers. In November 2016 LOC changed hands again, and it was more than a business transaction. It turned into a friendship! For Dave Barber and Jason Turicik of Plymouth Wisconsin it is a dream come true to have the blessing to work with their passions for design every day. Dave and Jason bring experience as previous owners of Yank Enterprises. As young entrepreneurs they had a catalog of over 20 rocket kits before the age of 21.

They bring fresh insight and new ideas. They promise to deliver exciting new selections, but also bring back "Retro" versions of the much loved classics from the good ol' days. They love working close with customers, and are open to phone calls, emails and Facebook feedback. They are happy to discuss custom orders and special requests. Along with traditions they will work to keep the relationships with educators to pass this hobby along to the next generation starting out through school. Very importantly, they value the ability to create and offer kits that are affordable for a Dad to take kids out to a launch. These guys are dedicated to maintain the high quality and service that LOC provided to customers over the last 31 years.

LOC Precision
435A Factory Street
Plymouth, WI 53073

Phone: (920) 892-0557
Email: This email address is being protected from spambots. You need JavaScript enabled to view it.
Website: www.locprecision.com

 

 

 

 

 

Published in Sponsors
Tuesday, 21 February 2017 17:27

HellFire 22 Dates Announced

HellFire, sponsored by the Utah Rocket Club (UROC)  takes place this year August 3,4,5,6. Though HellFire is technically an amateur launch, we’re talking serious rocketry here. Participants from around the country launch rockets ranging from foot-tall wonders to towering monsters that weigh in at over one hundred pounds, feature high-tech electronics, use a propellant similar to that used on the space shuttle, and lift off with 750 pounds of pure thrust.

Now in its 22nd year, HellFire continues to grow. Many people attend not to launch, but simply for the thrill of watching. Between launches, visitors enjoy examining rockets and components close-up and speaking with the experts who build and launch them.

Spectator Admission to HellFire is free and the public is welcome. HellFire will be held on the Bonneville Salt Flats near Wendover, Utah. Take Exit 4 on Interstate 80 and follow easy-to-spot signs. The event takes place 9 a.m. to 5 p.m. Thursday, August 3 through Sunday, August 6.

Discounted registration for flyers is available for UROC members.

Many more details to come over the next weeks.

Tips for visitors:

  • According to UROC insiders, Saturday is the day “where it starts getting crazy” with “lots of flights.”
  • All launch plans are subject to weather. Visitors are encouraged to check www.uroc.org BEFORE driving out to the launch.
  • There are no food or drink vendors at the event, so UROC reminds visitors to bring binoculars, hats, chairs, shade, lots of sunscreen, food and snacks, and plenty of drinking water.
  • UROC strongly encourages spectators to leave their pets at home, this is not a pet friendly environment
Published in UROC News
Tuesday, 26 July 2016 17:47

Aerotech

aerotech

Since its founding in 1982, AeroTech has grown to become the largest supplier of "D" through "G" power composite model rocket motors, mid-power rocket kits and related products and "H" through "N" high power rocket motors in the world. If you have flown any mid-power or high-power rockets. You have no doubt used an Aerotech product. 

AeroTech has been producing rocket motors for the motion picture special effects industry since the early 1980`s. AeroTech rocket motors have been featured in numerous motion pictures since then, and you can look for them in "Iron Eagle", Delta Force 2", "Tank Girl", "Star Trek: Generations," "Tomorrow Never Dies," and "October Sky". AeroTech also supplies rocket motors to educational institutions and rocket parts to other hobby rocket kit manufacturers. AeroTech kits and motors have been featured in a National Geographic article and PBS television show on thunderstorm research, a Travel Channel special on Ray Halm`s "Aries" project, a "Junkyard Wars" episode and a Discovery Channel "Mythbusters" program on the legend of Wan Hu. 

The core strength of AeroTech`s product line is its composite propellant rocket motor technology. Compared to conventional black powder propellant, composite propellant can produce up to three times the power for the same propellant weight. In addition, composite propellant technology permits the creation of rocket motors with performance characteristics and sound and visual effects not possible with black powder propellant technology. 

Charlie will be onsite to talk about Aerotech's newest products, answer questions and remind us just how cool Aerotech is!

 

AeroTech Consumer Aerospace Division
RCS Rocket Motor Components, Inc.
2113 W. 850 N. Street
Cedar City, UT 84721

Voice: 1-435-865-7100
Website: http://www.aerotech-rocketry.com/

 

 

 

 

Published in Sponsors
Wednesday, 15 June 2016 10:24

Register for HellFire

Published in HellFire
Friday, 24 August 2007 06:57

Fiberglassing Body Tubes in One Easy Step

One thing I have found about rocket construction is that there’s not just one ‘right’ way of doing things, in other words there can be many different approaches that can work on a given application. Here’s one way I’ve come up with to fiberglass body tubes and come up with a nice smooth finish all at the same time. I usually fiberglass whole lengths of tubes at one time and cut them to the length needed afterwards. 

I generally use ‘flex phenolic’ tubing but the method works well on paper tubes also as long as you sand the gloss layer with a course sandpaper such as 80-100 grit to allow the epoxy to ‘soak’ in the tube. Some have recommended peeling the outer layer of ‘glassine’ off but I’ve never been that ambitious and have had good results just sanding. I lay out the fiberglass flat, roll the body tube up in it the desired number of layers (depending on motor impulse level anticipated), and cut the cloth with a little overlap on the joint and the ends. If you cut it straight with the weave in the cloth you will have minimal loose strings to deal with, if you have any pull these loose to avoid them causing lumps in the finished product.

The next step is where you may need a little help, roll the tube tightly in the cloth and while holding the cloth rolled up on the tube have your helper roll a leg of women’s nylons down over the tube to completely envelope the tube and the cloth

At this point I use a twist tie to hold the open end of the nylons leg closed. After you get it tied off you can go back and smooth out any wrinkles that may have shown up under the nylon ‘veil’. This is generally easier if you start with ‘queen sized’ nylons on the tubes 4”- 6”, but is fairly easy with ‘normal sized’ nylons on anything smaller. At this point you have the hard part done; you can don the latex gloves and mix up a batch of epoxy. I generally use the stuff that cures in 30 minutes or so. I’ve found using the cheap paintbrushes available at Wal-Mart on the smaller tubes or the smaller paint rollers on the bigger tubes minimizes the mess and makes epoxy easier to apply. Hold the tube horizontal and start laying that stuff on!

When you get the whole tube coated and the epoxy worked in so the cloth goes transparent work out any bubbles you have and hang it up by the twist tied end to cure. If you didn’t use too much epoxy it shouldn’t run down too much but after 15 minutes or so you can turn it over to even out the ‘flow’. After it’s cured just trim off the ends (I use a power miter saw because I’m lazy), and sand the entire tube with the orbital sander of choice in long smooth strokes while turning frequently. This usually goes quick since the nylons provide a nice smooth finish by themselves.

Well that’s it, this method may not be to everybody’s taste but it’s worked for me for years on a lot of rockets from ‘G’ power level up to full ‘L’ (I couldn’t find big enough nylons for 7.6” tubing).

Tracy “Woody” Wood - TRA#4828 L3

PS - If you don’t care for filling spirals on tubing but don’t feel your rocket needs the extra strength of Fiberglassing just pull a leg of nylons down over the tube with no fiberglass cloth underneath and epoxy coat the same as above (after sanding on paper tube). It will add some strength with minimal weight gain on the finished rocket and fills those nasty spiral marks.

Published in Learning
Tuesday, 07 August 2007 16:11

Thinking About Level 3? You Can Do It!

As the UROC club grows, there are more and more flyers that are progressing up the ranks of level 1 and 2. Some of you may be considering making the jump to level 3 and wondering if this is something that you might want to achieve. UROC has seen a big increase in the number of Level 3 flyers over the last couple of years. I remember when I first got into high power rocketry I thought that those guys putting up level 3 rockets must have a PhD in astrophysics or some other connection to NASA. Surely, Level 3 rockets were beyond my basement building techniques.

The purpose of this article is to demystify the Tripoli Level 3 process for anyone considering making the jump and to set forth guidelines to help walk you through the steps.

I am not a NAR member so I am not as familiar with their procedures but I understand NAR has adopted similar regs and rules. Currently, Tripoli has about 700 Level 3 members nationwide with more being added all the time.

First of all, I am a TAP (technical advisory panel) member for Tripoli. TAP members must be level 3 certified and must apply to the Tripoli board for inclusion on the membership list. I wanted to become a TAP member because there was nobody in Utah at the time that could help certify Level 3 members at our launches. Also, I enjoy seeing the nuts and bolts of other Level 3 projects and I learn something new from each and every one. To date, I have flown or been very involved in about 50 M and N motor flights. That's some AP poundage!

Why does the TAP committee exist? Because Tripoli believes that as the rockets get bigger and the total impulse goes up, the potential danger also rises. These rockets should have more than one pair of eyes looking at them to ensure that they are safe and the construction and design techniques make them flight worthy. After the flyer has demonstrated the ability to construct and successfully fly a large M motor rocket, he or she is free to fly other Level 3 rockets without TAP approval.

Myth #1

Level 3 rockets are technically much harder to fly than level 2 and 1 rockets. Not necessarily true. In fact, many level 2 rockets, especially multi stage or clustered J-K rockets are tougher to fly and more technical than basic Level 3 rockets. For your Level 3 attempt you may want to employ the KISS method (Keep It Simple Stupid) to have a greater probability of success.

Myth #2

The Level 3 process is a lot of bureaucracy. Not true. There are some basic steps that you have to follow but with friendly TAP members (like me) guiding you, this should pose no problem.

Myth #3

Level 3 rockets cost a lot. Actually, this one isn't a myth. Level 3 rockets are definitely a step up in the cost factor depending on what you decide to do. But, if you can borrow somebody's motor hardware (with the typical lose-it-or-dent-it, you-buy-it policy) you can help bring the cost down. The 75mm reloads are also a lot more cost effective than the 98mm loads. Still, it is not uncommon for a level 3 rocket to cost over $1000 when you consider electronics, parachutes, motor hardware, motor reload and airframe parts. Everything but the reload is reusable but you still have to ask yourself, "What will this cost if it crashes and I lose everything?"

OK, so how do I get started on my Level 3 project? First of all, you need to select a project to build. It can be an upscale of an old estes kit or a Level 3 kit from some of the various rocket vendors or your own design. Some of the basic Tripoli rules for the design are as follows:

  1. Single stage design only.
  2. No clusters allowed.
  3. The project must be constructed principally by the flyer.No team projects allowed.
  4. Electronic recovery is required and must function as designed. A redundant (backup) recovery system is also required. This can be motor ejection but not recommended. I always advise that either two altimeters be used or one altimeter and a timer backup.
  5. Two-stage recovery is not required. If you want to keep it simple, blow the main parachute at apogee. A lot of Level 3 rockets don't go that high anyway.
  6. Currently, Tripoli is allowing kits from manufacturers to be used. There is some discussion among the TAP committee that only scratch built rockets will be allowed in the future. More to come on this issue

Next, you should contact a TAP member to discuss your project. He'll tell you what you need to do in order to get your paperwork signed off. In my case, I tell the flyer that I would like to see the following:

  1. Overall written description of the project with specification such as length, weight (loaded and dry), diameter, electronics involved, recovery systems, expected altitude, etc.
  2. A schematic of mechanical drawing showing all components of the rocket.
  3. Some photos of construction are nice if you can take them as you build.If not, then details of construction and materials used, etc.
  4. Some computer simulated flight profiles with the motors you expect to use.
  5. Tripoli paperwork.

For Level 3 certification, you need to have two TAP members sign off on your project at least one month before you actually make the flight. This is to allow time for minor changes that TAP members may suggest. If you would like to use me for one of your TAP members, I can suggest others that would be happy to serve as your second committee member. Rich Evans of UROC is also a TAP member in Utah and is happy and willing to serve as a second TAP member for UROC level 3 projects.

Finally, you need to launch your project. The day of reckoning! For the actual flight, a TAP member must witness the flight and survey the rocket upon recovery. The TAP member witnessing the flight can be one of the first two preliminary members that you used or it can be a third member. If the flight is successful, he will sign your paperwork at the site and mail it in to Tripoli headquarters.

In my case, I define a successful flight as follows: The rocket must work as designed and sustain only cosmetic or minor damage. Example: If you design in a level of complexity such as two-stage recovery, then the rocket must work that way. Damage such as zippers may mean that recovery was somehow compromised or structurally the rocket couldn't withstand the forces encountered during chute deployment.

What's the success rate? The Level 3 projects that I've been involved in have had about a 65% success rate. 2 successes for each failure. That's not bad. And for the failures, most were able to launch again at a later date and have a successful flight.

Hopefully, this article will encourage some of you who are thinking about Level 3 to go for it. If you want to call me to get started, my phone number is 277-9006 hm or you can catch me at a meeting or launch.

Published in Learning
Tuesday, 07 August 2007 04:03

Fin Fillet Construction

As with many aspects of rocket building, there are many ways to do things. This is how I make my fin fillets and can be used on both methods of fin attachment, direct body and through the tube attachment.

I use balsa wood for the fillet material in the profile shape of a triangle. Square material could be used, but it would require more sanding. I cut the balsa a little longer than the fin root chord length and sand the sides to make it fit. The balsa is cut at 90 degrees and the area for the fillets is more than that, so some sanding is needed.

I disregard the fact that the fin is flat and the tube is rounded at the glue joint area. This small difference is filled in with the adhesive and is less noticeable with the larger rockets. I use slow cure epoxy for the adhesive. I have tried to use wood glue to save money, but when it dries it shrinks and makes huge gaps in the fillets when even using pins to hold the balsa in place.

I force epoxy in the fin/tube joint for through the tube attachments, apply epoxy to the balsa and attach the fillets. Be careful not to get epoxy on the fin or the tube outside the bond area. While curing, examine the fillets to make sure they are staying in place. Pressing on the fillets during curing a few times makes the fit better.

After cure, sand the fillets using a sanding drum tube held between the fingers. I use a 1/2" X 2" drum on the smaller rockets less than 2", and 1" X 2" on the larger rockets. While sanding, and as the flat side is becoming concave, be careful not to cut into the fin or the tube. It will make a groove that will have to be filled later. Stop sanding just as the edges of the balsa meet the tube or fin. While sanding, compare all fillets to make sure they are coming out even in shape.

The forward part of the fin/tube attachment is the hardest to shape. I use a pencil wrapped with sand paper to make this transition smooth, again making sure that all joints are identical. If the tube extends aft past the fins this procedure must be used again. If the fins end with the tube, sand this area flat and fill any voids with filler. I always glass the fins and tube for strength.

Published in Learning
Saturday, 24 June 2006 10:07

Making a Foam and Wood Nosecone

After trying several ways to create the nosecone for the ASP (Atmospheric Sounding Projectile), I've decided I won't use any of those methods again. Here are some notes and photos of what I did, and a few suggestions for what I'd do differently. Any input would be welcome.

We (Luke, Ian and I) had earlier experimented with gluing up just the foam (styrofoam insulation), turning it to shape, splitting it and then gluing it to the wooden ribs that were to support it. Bad idea all around in my opinion. It was a pig to put (and keep) on the lathe and cutting the finished product into four equal pieces would be a pain. Maybe it'd be OK for a smallish cone but not for this one. By the way, gluing a piece of styrofoam to a wood disc and attaching that to a faceplate on the lathe works pretty good for pieces up to maybe a foot long and a foot in diameter.

Image

The next experiment was to create a wooden support structure with a 1” dowel at the center and 1/4” plywood ribs for support. The dowel had four 1/8” deep dadoes cut into it to hold the plywood.

Image

I then cut the ribs so that, when glued to the dowel, they would make a structure defining the size and shape of the finished nosecone. Stacking the rib blanks and taping them together made it fairly easy to cut them the same size and shape.

Image

I drilled and cut foam circles just a little bigger than the wooden structure and quartered them.

Image

A 3/4” center hole worked great and careful quartering produced a pretty good fit when I began gluing the pieces to the ribs.

The first attempt I made at this procedure can be seen on the lathe in the background of the picture above. I thought I might be able to do it cheaply by using liquid nails to hold the foam together. - -Wrong.- - The liquid nails ate the foam from the inside out and the whole thing blew apart under stress on the lathe.The assembly in the foreground has wood glue for the wood joints and Devcon epoxy for sticking the foam. I used 5-minute epoxy but I had extra hands there to put the cable ties on and help mix the epoxy. Working alone would definitely require slower epoxy. 

This attempt went well. I planned on using a skew (angled knife) to turn the foam down until I hit wood and figured I'd get the right shape and a nice smooth finish that way. The first time I nicked the wood I could tell I'd have to change plans. Even with a razor sharp skew, the difference in density between the foam and the wood made the knife catch and pull. I ended up using a drywall sanding block and paper to get the finished shape while the lathe was running. One downside to sanding instead of cutting was that any amount of pressure applied to the sanding block wore the foam more than the wood resulting in a dip along one edge of the rib. Another downside to using the sanding block was that I couldn't get the nice crisp corners I wanted on the angles in the lower portion of the ASP's cone.

Image

The Finished Product - Next time I'd make the wood ribs smaller than the finished cone size and fill in with 1/4” strips of foam. It would take some careful work with a skew and calipers to get the exact shape but I'd prefer that to sanding and I think I'd be happier with the results. Turning the foam on the lathe is easy and that's nice, but the stuff is so soft I ended up looking for a filler to take care of some nicks. Lightweight vinyl spackle seemed to do the trick.

Something else I'd like to try would be to turn a wooden form and create the cone out of fiberglass. Maybe glue a wooden support structure in later after the cone was removed from the form. That kind of glass work is beyond me right now but I'd love to learn. More to come, Evan

P.S. You can find out more about this project on Jim Yehle's pages at http://www.xmission.com/~jry/rocketry/projects/asp/asp-group-project.html.

 

 

 
 
 
 

 

 

 

Published in Learning
Thursday, 11 November 2004 10:25

How To Interpret Rocket Motor Codes

motorclass1Sport rocket motors approved for sale in the United States are stamped with a three-part code that gives the modeler some basic information about the motor's power and behavior. For example, a "C6-3" designation indicates that the total impulse of the motor ("C"), This number specifies the average thrust ("6"), and finally, the last number indicates the time delay between burnout and recovery ejection ("3").

Total impulse is a measure of the overall total energy contained in a motor, and is measured in Newton-seconds. The letter "C" in our example motor above tells us that there is anywhere from 5.01 to 10.0 N-sec of total impulse available in this motor.


In a typical hobby store you will be able to find engines in power classes from 1/2A to D. However, E, F, and some G motors are also classified as model rocket motors, and modelers certified for high power rocketry by the NAR can purchase motors ranging from G to K.

Since each letter represents twice the power range of the previous letter, total available power increases rapidly the further you progress through the alphabet.

Average Thrust

Average thrust is a measure of how slowly or quickly the motor delivers its total energy, and is measured in Newtons. The "6" in our example motor tells us that the energy is delivered at a moderate rate (over about 1.7 seconds). A C4 would deliver weaker thrust over a longer time (about 2.5 seconds), while a C10 would deliver a strong thrust for a shorter time (about a second).

As a rule of thumb, the thrust duration of a motor can be approximated by dividing its total impulse by its average thrust.

Keep in mind that you cannot assume that the actual total impulse of a motor lies at the top end of its letter's power range -- an engine marked "C" might be engineered to deliver only 5.5 Newton-seconds, not 10.

Time Delay

The rocket is traveling very fast at the instant of motor burnout. The time delay allows the rocket to coast to its maximum altitude and slow down before the recovery system (such as a parachute) is activated by the ejection charge.

The time delay is indicated on our sample motor is 3 seconds. Other typical delay choices for C engines are 5 and 7. Longer delays are best for lighter rockets, which will coast upwards for a long time. Heavier rockets usually do better with shorter delays -- otherwise the rocket might fall back down to the ground during the delay time.

Motors marked with a time delay of 0 (e.g., "C6-0") are booster engines. They are not designed to activate recovery systems. They are intended for use as lower-stage engines in multi-stage rockets. They are designed to ignite the next stage engine immediately once their own thrust is finished. Often their labels are printed in a different color to help prevent you from using them in a typical rocket. In a multi-stage rocket, you would usually select a very long delay for your topmost engine.

https://en.wikipedia.org/wiki/Model_rocket_motor_classification

 

Published in Learning
Thursday, 07 February 2002 17:00

Rocketry Rules of Thumb

First, please read the fine print... There are many different solutions to the rocket design challenge. Rules of Thumb simply provide a solid starting point that many have found useful in the past, and that will, in many cases, provide a suitable solution for your design problem today. Rules of Thumb are guidelines. They're not laws. They are nominal solutions that usually, in many cases, most of the time, get the designer in the right ballpark. Once a rocket designer's judgement has been formed by lots of experience, some Rules of Thumb can be stretched, bent, stood on their head, or ignored completely.

Using Rules of Thumb certainly does not take the place of stability tests, or attention to safety. Proof of stability and a constant focus on safety are the most fundamental and unchangeable Rules of Thumb I know. If you know Rules of Thumb that are not mentioned here, e-mail them to Tom Savoie and they could appear in a future update with your name as the contributor. Comments are always welcome.

General Design

Motor Mount Size
Build your rocket for the largest motor you might want to fly in it. You can always adapt down, you can never adapt never up.

Paint Selection
Whatever your choice, use a primer, finish and clear coats that are compatible. Many times this means sticking to the same brands-e.g., Krylon primer, Krylon finish coat, and Krylon clear coat.

Airframe

Diameter And Length Of The Rocket
The ratio of rocket length to diameter, sometimes referred to the aspect ratio, should be from 10 - 20:1. For example, a six inch diameter rocket would mean a length of 60 -120 inches.

Reinforcing the Airframe
The larger the rocket, the more important reinforcement becomes. Two layers of a lighter fiberglass fabric work better than a single heavy layer. Two layers of 4oz fiberglass works well for 3-4 inch rockets, 2-3 layers of 6oz for 5-7.5 inch rockets. A final wrap of 2 oz glass provides a good sanding veil. Glass a rocket measuring 2.56" or greater that will reach equal or greater than 0.85 Mach.

Fins

Fin Dimensions
A fin that is 2 diameters of the airframe in root length and span and a chord length of about 1 diameter will be effective.

Fin Shape or Planform
The shape you see more than any other is called the clipped delta, and is known for its effectiveness. The clipped delta resembles a parallelogram, with the fin swept somewhat to the rear. The root and chord lines are near parallel, and the leading and trailing edges are near parallel. There are many, many shapes that will get the job done. Some look cooler to me than others. One of the most efficient fin designs looks like a simple rectangle attached to the tube.

Shaping the Fin
The leading edge of the fin should be rounded, the trailing edge shaped like a V. The chord edge should remain square.

Number of Fins
Three fins will almost always do the job. Four fins work too, but only marginally better as far as improving CP. Some have said that four fins reduce wind-induced spin.

Recovery

Black Powder Ejection
Use enough BP to yield a 15 psi pressure within the airframe. See article on Ejection Charges for a detailed discussion.

Sizing The Parachute
You want your rocket to descend at about 15 feet per second under nominal conditions. Slow it up over playa and concrete. Use 3.5 square feet of chute per pound of recovered rocket weight. Determine chute size by doubling the square root of the weight of the rocket. For example, a 16 pound rocket would use a 2X4=8' chute. A 49 # rocket would use a 2X7=14' chute.

Streamers should be 10 times as long as they are wide.

Drogue recovery descent should be about 50 ft/sec.

A full-hemispherical canopy has very little performance gain over the more efficient and less bulky quarter-spherical--the top-half of a full-hemispherical chute.

Recovery Harness Strength
Tensile rating for recovery materials should be at least 50 times the static weight of the rocket.

Sizing Tubular Nylon
9/16" serves well in rockets up to 15 pounds. Go with 3/4 up to 30 pounds. 1" up to 50 pounds.

Length of model rocket shock cord
Make shock cords for model rockets a minimum of 2 to 3 times the overall length of the rocket. Middle or high power rockets should use tubular nylon at least 5 times the rocket length.

Wadding
Use enough wadding to fill 2 x the diameter of your BT. Any more is probably overkill. Any less may allow hot particles through to hit your chute. Do not pack it tight.

Knots, Loops and Sharp Bends in Shock Cord or Bridle
Knots, sharp bends, including sewn loops, in the tubular nylon or flat webbing will weaken its load capacity by 50%.

How Tight is Tight?
Many people use masking tape to finesse the fit between an airframe and a coupler that must separate at deployment. A common question is: how tight do I want it to be? Use enough masking tape so that you can pick the rocket by the nose cone without the rocket coming apart. If you vigorously shake the rocket up and down, and don't see any movement off the coupler, you've probably got too much tape on, Jack.

Piston Deployment
Use 25% less Black Powder if your deployment system is piston driven.

Piston Maintenance
Running a damp cloth through your airframe after flying will clean out powder residue and keep your piston moving freely.

Shear Pins
Use shear pins on any rocket where you need a little extra piece of mind to know everything will stay in place until the proper time. Use 1/16" styrene rod or #2 nylon screws on almost any high performance rocket. For example two styrene shear pins each on a 2.6" phenolic airframe, 4 nylon screws on a 6" bird. See the article on Shear Pins in the CONSTRUCTION area for more detail.

Shortening Delay Elements
Note: Adjusting the delay as described below is considered a modification to the motor and is therefore against the rules in a TRA/NAR sanctioned launch. Delay grain burns at the rate of 1/32" per second. Shorten delay time by drilling a 1/16" bit to drill a hole into the ejection charge end of the delay. Drill to a depth of 1/32" for every second you want to shorten the delay. A piece of tape wrapped around the drill bit at the proper depth will help ensure an accurate depth. Don't drill more than 25% into the length of the delay.

Stability

Margin of Stability
The CG should be forward of the Center of Pressure by 1-2 calibers. A caliber is simply the diameter of the bird. One caliber of stability is also known as a margin of stability. In other words, in a four inch rocket, the CG must be ahead (closer to the nosecone) of the CP by 4 - 8 inches. More than .5 but less than 1 margin of stability (less than one caliber) and a rocket is "marginally stable'. More than two calibers of stability is known as "over stable". An over stable rocket will tend to dramatically turn into the wind. A marginally-powered, over stable rocket can end up almost horizontal.

Adjusting the Center of Gravity
To move the CG forward, add weight to the nose, lengthen the rocket, or lessen the weight in the aft end of the rocket. To move the CG aft, (for example, if your rocket is overstable), do the reverse.

Adjusting the Center of Pressure
To move the CP aft (more stable), increase the size of the fins. To move the CP forward, decrease fin size.

How Long is Too Long
A rocket must maintain its rigidity in flight. Any tendency to bend will be magnified in flight resulting in a kinked tube and likely a failed flight. If you hold a rocket horizontal by its tail section and notice any curvature in the rocket, your bird probably isn't stiff enough. Sorry, rocketeers, Viagra will not cure this problem.

Propulsion

Sizing the Motor
In selecting a motor to power your rocket, you need to have at least a 5:1 thrust to weight ratio. See a detailed discussion of this guideline Motor Selection in the PROPULSION area.

Launch Operations

Launch Rod Diameter
Determine by motor size:
A,B,C - 1/8"
D,E - 3/16"
F,G,H and a body tube less than 2.6" - 1/4"
F,G,H,I w/ 2.6" to 4.0" body - 7/16"
I,J - 1/2"

Over J and body tube over should use rail buttons

Minimum Speed for Stable Flight
44 fps (30mph) is generally accepted as a minimum safe speed for stable flight. Faster speeds are necessary to achieve stability in windy conditions.

Mounting launch lug(s)/button/s
When mounting a single lug, cover the center of gravity with the lug. Always mount at least two rail buttons. When mounting two lugs or buttons, mount the lower piece at the rear of the airframe. The second should be on or just behind the center of gravity.

Submitted by Tom Savoie

 

Published in Learning
Page 1 of 2

Search our Site

Member Meeting

September
Monday
11
We will hold the ever-popular "HellFire Post Review" as well as other presentations to be announced.
07:00 PM

Balls 26

September
Friday
22
BALLS is the premier Experimental Rocket Launch in the Continental US. It spans 27 years however this year will be the 26th time it is held in the Black Rock Desert, North of Reno, near Gerlach,...

Contact Details

Call Us
+1(801) 893-1074
Mailing Address
PO Box 26584, Salt Lake City, UT 84126
Questions?
info@uroc.org

About UROC

The Utah Rocket Club is an Not for Profit organization dedicated to the promotion of safe and fun activities for people of all ages through the sport, science, and hobby of rocketry. The Utah Rocket Club supports the community through educational presentations, demonstration launches and displays for youth groups, nonprofit organizations, etc.

Learn More