Tips

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What NOT to Do - Stupid Rocket Tricks

My Tips

Nose Cones
  1. See my Big List of Materials to see what you can use for a nose cone.
  2. Fill the seams on plastic nose cones using an epoxy filler such as SuperFil from Shadow Composites. This light weight stuff mixes, fills, and sands easily.
  3. When turning small cones on a hand drill, use a section of brass tubing epoxied into the balsa or styrofoam stock. This works much better than a wooden dowel, especially for larger cones. To make sure the shoulder is the right size for your tube, slip a short section of tubing over the chuck before you start. Stop periodically as you turn the shoulder and check your progress.
  4. You can approximate any shape cone with a set of truncated conical sections. Start with a small tube and position centering rings of various diameters along its length. Make the appropriate wraps using VCP.  I used this technique on a large rocket, The Grand Whazoo.
  5. For Micro-Maxx cones, just clamp a piece of 3/8-inch dowel into your hand drill. Clamp the drill in a vise and turn the cone with a wood file or very coarse sandpaper, followed by finer sandpaper. Use enough dowel for the cone, it's shoulder and the depth of the chuck. When complete, cut off flush with the chuck.
  6. I haven't tried this yet, but I hear scrap balsa with a toothpick glued in works. You can turn these on a Dremel-type tool. (Also for MicroMaxx, obviously.)
  7. You can make cones from leftover chunks of body tube. Here's a good video on the process.  And, here's my version of how to do it in 22 easy steps.  The video method requires epoxy.  My version requires 2-part expanding foam and Elmer's Fill-n-Finish.
Recovery
  1. Use quick-connect devices on all chutes and nose cone connections. I make as much of the recovery system replaceable as possible. For small rockets I use fishing snap swivels and for larger rockets use heavier quick-connects.
  2. Keep several sized of Nomex pads around. Use them in place of (or in addition to) wadding.
  3. Nylon ty-wraps are very useful for rigging recovery connections in the field. They are very tough. I keep several sizes in the range box.
  4. A long time ago now, I acquired two discharged automobile air bags. I have made several chute protectors ranging in size from about 15" to 3" (octagonal, measured corner to corner). For a shock cord connection point, my wife sewed large button holes, the center of which were slit using an X-acto knife. These have worked great for both Estes BP motors and mid- and high-power composites.  I have found these are more durable than commercial pads made from either Nomex or Kevlar!
  5. I saw this rule of thumb somewhere and wanted to capture it before I forgot. I'm not convinced of its accuracy since the decent rate of rockets will vary, but here goes: In a 10mph wind, you should plan on walking a distance equal to the apogee of your rocket.
  6. I have been repairing burn holes in my rip-stop nylon chutes using nylon tape from Into the Wind. I just apply the tape to both sides of the hole, and so far the patches seem to be holding up great.  One 'chute even lived in a tree for two years and the tape was stayed firmly in place! The only brand 'chute this didn't seem to adhere to is a Rocketman, which are kind of 'slippery'.
  7. Most altimeters and timers that auto-detect launch will work fine on your rocket.  Unless: 1. Your liftoff is too slow to trigger the event, or 2. Your thrust phase is too short to trigger the event.  I have met both criteria (but not at the same time).  I've had a heavy rocket that didn't activate the G-Wiz altimeter and a G339 flight whose entire thrust phase was shorter than the trigger time of the timer.
  8. A soldering tool with a notched tip makes stuffing a Kevlar® shock cord into a small airframe (i.e. MicroMaxx sized) a LOT easier.
  9. Dog barf wrapped in Estes or Quest flameproof wadding.  Makes a flame resistant piston of sorts. That's one of my current favorites for rockets <3" in diameter. Often recovered near the rocket.  If recovered, often reusable.  Photo in this post
  10. Burn hole in your 'chute protector? A quick temporary fix is to patch it with duct tape.  Doesn't last for many flights but is easy to replace.
  11. Recovery speed tips via Bob Krech on TRF:
    1. Smaller, lighter model rockets can normally descend at a higher velocity than a heavy high power rocket.
    2. The surface is important. At grassy field will support a higher descent rate than a sun baked playa or asphalt.
    3. Smaller rockets landing on grass fields can handle 20-25 fps landings.
    4. Smaller rocket landing on hard surfaces and larger rockets ideally should have a final descent speed of ~15 fps.
    5. Drop test your rocket over the same type surface as your LZ before you launch.
      • A rocket dropped from 4' has a terminal velocity of 16 fps.
      • A rocket dropped from 6.25' has a terminal velocity of 20 fps.
      • A rocket dropped from 10' has a terminal velocity of 25.3 fps.
      • To determine the drop high, ft. for a velocity, fps: d=(v/8)^2
      • Drop from all orientations. If nothing breaks, you're good to go with landing speed comparable to the velocities obtained in the drop test.
Airframes
  1. See my Big List of Materials to see what you can use for body tubes.
  2. My favorite mailing tubes come from the Container Store. They are 48" long and have a full length inner tube - good for couplers, double-walled construction, etc. If you use the coupler stock to make a fin can for your ring fin rocket, the ring fins will be flush with the body tube, which simplifies the addition of rail buttons.  The lower button can reside in a ring fin and no spacer is required on the upper button (which can also be used to hold the fin can in. See the AquaBottleBat review.
  3. Fill spiral lines on paper with Elmers 'fill 'n finish'.
  4. Fill spiral lines on phenolic using an epoxy filler such as SuperFil from Shadow Composites. This light weight stuff mixes, fills, and sands easily.
  5. For those 'junk builders' who'd rather scrounge than order, the packaging for CTI 38mm reloads is a good match for AeroTech 1.9" tubing.  Ref: my AeroTech Cheetah rebuild.
Motor Mount/Retention
  1. I like the 'Kaplow Clip' style retainers the best in terms of their bang-for-the-buck. These are metal clips that you screw into either threaded inserts or T-nuts mounted in the rear centering ring. Although they seem easy to make, I have two purchased sets that I move from rocket to rocket. I also have used aluminum window screen brackets, picture hangers, and good old fender washers..
  2. Although any long, thin implement can be used to get epoxy into tight places, my favorite is the throw-away chopsticks that you get at many Chinese food restaurants.
  3. You can make DIY motor retainers from PVC fittings.  This EMRR article tells you how to do it for 29mm motor mounts and this rocket review describes how I made one for a 38mm mount.  For 29mm mounts, I now recommend Estes' new retainers.  These are lighter, have a precision fit, and look better.  You can get two sets for around $6.00 from Hobbylinc.  For three bucks, it isn't worth dealing with the PVC shavings.
  4. When the new Estes E12's came out, I immediately started planning what to fly them in.  I came up with several models that have flown on 24/40 reloads but that also have clips designed for the shorter motors.  I came up with a nifty solution.  Cut a slice of a spent 24mm motor, section it, and glue it to the longer motor.  This process leaves a small gap in the resulting shoulder.  You insert the motor so the clip passes by the gap and twist it so the clip engages the shoulder.  I don't have a reference but I remember that glue-on motor motor retainers are not considered a motor modification by the NAR.
Fins
  1. See my Big List of Materials to see what you can make them out of. I haven't used them but hear corrugated plastic signs are a good source.
  2. For minimum diameter rockets, slot the airframe to fit the fins and epoxy the fins into the slots. When mounting, place a spent SU casing covered with a thin layer of Vaseline into the airframe. The Vaseline will keep the epoxy from sticking to the casing while you align and secure the fin. This works best with thicker airframes (1/16" and up).
  3. Use fin tabs to the MMT when possible.
  4. Always use outer fillets, use inner fillets for HPR.
  5. In place of, or in addition to, internal fillets, I have also successfully filled the fin can with 2-part foam. Never use one part foam from a spray can. It requires moisture to cure and can be re-activated by heat. Mix only a small amount of the 2-part foam at a time. When it's set, cut off any overhang.
  6. When aligning split fins (e.g. the PML Small Endeavour), I use a light but rigid plastic ruler and two small, 3/8" capacity, binder clips (~c-shaped black metal clips). They are light but strong for their size. I clip the ruler to each fin and use an alignment jig on the front fin. The ruler and clips keep the fins perfectly aligned and, because they are light, they do not tend to pull the fins off center.
  7. A rafter angle square can help in fin layout, alignment, and slot marking.
  8. Instead of rubber gloves, consider buying latex "finger cots", which cover a single finger. I found these in the pharmacy department of my local Safeway. They allow more flexibility/dexterity than a full glove and still keep the epoxy off your skin. They are easily rolled on and off your finger - just don't think about their intended use :-).
Launching
  1. If you are not trying to squeeze every ounce of performance out of your sport rocket, consider adding several size lugs and/or rail guides. I notice that at most launches there seems to be one size rod that gets backed up. Using more than one lug may decrease the time you wait in line.
  2. If you use a forward-mounted motor, make sure to secure the igniter clips carefully! If you don't, they WILL snag a fin!
  3. A cheap ceramic tile, epoxied to a piece of plywood, makes a great blast deflector and costs under a buck. Drill the hole for the launch rod in one corner using a masonry bit. On mine, I glued a scrap piece of tubing on the bottom of the opposite end to provide support to the deflector.
  4. There are several theories on the placement of rail buttons. In most, the lower button is placed as far to the rear of the rocket as possible. Theories for placement of the top button include: 1) place it at the CG; 2) place it at the CP; 3) place it at the top centering ring that sandwiches the fin tabs. I generally use the latter method. I suppose is possible that torque caused by having the top button away from the CP/CG (depending on which you think is best) could either pull it off or cause it to bind in the rail guide. However, I have not experienced these problems. This method has several advantages. You have to realize that the effective length of your launch guide in a rail system is the distance from the top button to the top of the rail. Once the top button has left the rail, the rocket is able to pitch around the lower button. So, the lower the top button is, the more guidance you have. The lower placement also avoids interference with the recovery system, including pistons on the PML rockets. Finally, placing the rail buttons adjacent to centering rings helps support the mounting screws. My theory is that the force on a button will tend to pull the head of the screw down and the tip upward, so the button should be placed immediately below the centering ring.
  5. You can buy dirt-cheap nylon rail guides here. They cost 25 cents each, and are available in black, white, red, blue, yellow, and green. They come in three pieces, plus the bolt, and the colors can be mixed. I have now used bunches of them on LPR, MPR, and HPR models. They are great! He now also makes Delrin buttons to the fit the Blacksky rails and a larger size to fit the 1.5" x 1.5" 80/20 "1515" extrusion, which has a 5/16" slot.
  6. Yesterday, I found an old 'recycled' rocket's nosecone was a bit tight after several quick fixes for a crunched body tube.  In this case, the RSO removed the cone and, using the pointy end, carefully stretched the tube.  I use the term stretched for lack of a better one.  The change was minor, but was enough to provide a perfect fit for the cone's shoulder.  This may also be useful for non damaged rockets.  Wouldn't use a balsa cone for this though.
Finishing
  1. Fill spiral lines on paper with Elmers 'fill 'n finish'
  2. Fill spiral lines on phenolic using an epoxy filler such as SuperFil from Shadow Composites. This light weight stuff mixes, fills, and sands easily.
  3. Test the compatibility of different paints on a scrap piece of material.
  4. Rustoleum 'hammered finish' paints look cool and mask finishing imperfections.
  5. I recently discovered Microbrushes, by Microbrush Corp. They go for around $1.29 for a package of ten and come in several sizes. I got the ‘regular’ size, which has a circular tip that’s approximately 1/16” in diameter. These are useful for applying liquid glue in small cracks and for painting small areas and details. They clean nicely and can be reused.
  6. Added 7/16/2012:  Via Model Rocket Building, a tip on how to fill those spiral lines.
Propulsion
  1. When you can, support the vendors that attend your launches! Several launches I attended would have been a wash-out without Ken from Performance Hobbies.
  2. Bring extra igniters and carry a few to the pad.
  3. To make my own bridge-wire igniter, I took a used Magnelite ML-12, trimmed the scorched end, separated the leads, and cut one lead ½ inch shorter than the other. One-quarter inch of insulation was then stripped from each lead. Using some nichrome wire (I didn’t buy it so I’m not sure of its gauge, maybe 32 or 33), I hand-wrapped 5 turns on the shorter lead’s conductor, 5 turns on the longer lead’s insulation (about the same as the original igniter), and another 5 turns longer lead’s conductor. All the wraps were non-overlapping. The igniter was then prepared like the rest. Once cured, the igniter read 2.3 ohms. I used it on a G80FWL motor and it lit immediately. Not bad for a ‘quick and dirty’ effort, and no soldering or special tools were required. 
Flight and Stability
  1. See my lengthy post about stability and performance.
Repairs
  1. To replace a broken shock cord, you can install a Kevlar leader along the side of a launch lug as follows:
    1. Punch two small holes, one on either end of the lug in the fillet area.
    2. Feed the Kevlar twine into the back hole and fish the end out.
    3. Tie a double knot and pull the knot against the hole.
    4. Feed the loose end through the upper hole and fish it back out.
    5. Keeping the line taut, apply a fillet with 5-minute epoxy, and work a bit into the rear hole where the knot is.
    6. If not exclusively using the Kevlar as a shock tether, you can attach some of your favorite sproingy material.
  2. Add a couple of folds of tape (I prefer duct tape) at the point where the Kevlar line touches the body tube.  This will reduce Kevlar-induced zippers.
  3. I found several of my Nomex 'chute protectors were tearing in the middle.  Holes will allow gas to pass so this is not good.  I found duct tape works as a decent patch material.  It adhered well and was still in place after the flight.  I don't know low long it will last, but it's cheap and easy to replace if it falls off. P.S. - If the pad sits in water, the tape will need replacing.  But that isn't the worst problem you'll have.
  4. Via AKPilot on TRF, I see that you can de-bond Titebond wood glue with vinegar. I assume this will work on any aliphatic resin-based glue (?)
  5. Wood working knives can be used to surgically remove tri-fold mounts.
  6. Added 7/16/2012:   When using a reload in a rocket with an Estes motor clip, always add a few wraps of masking tape.  Reloads can pop out even if you think they seem secure.  Someone on TRF  also suggested wrapping the motor with tape (e.g. friction fitting) to make it snug.  Double insurance against losing that tiny, relatively expensive case!
Centering Rings
  1. There are many great tools for making your own plywood centering rings.  I recently have used a buddy's plunge router with a circle attachment.  At home, I use either my RotoZip or hole saws on my drill press.  Hole saw sets are inexpensive at Harbor Freight and you can find one that's close for many tube sizes. Extra grinding with a Dremel or the creative use of shims will make these very usable.
  2. For paper/fiber rings I use an Olfa-style circle cutter.  These are inexpensive at places like Michaels (just remember the coupons).  I like using fairly thick stock and cutting all the way through can be a pain. I found that if you cut about half way through, you can switch to a Sharp Exacto with the venerable #11 blade.  This cuts faster than the circle cutter and the channel made by the cutter keeps the circle round.