Tips and Technique of the Day Thread (Twice a week).

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Strengthen your fillets and joints:

Contributor: @dr wogz

Don't toss the strands from carbon fiber and fiberglass cloth. You can embed them into your epoxy fillets & joints for some added strength. You can leave them whole or make chopped filaments 1/8-1/2" long and use them as a thickener and strengthener.

Thanks, @dr wogz for this tip.
 
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Tape That Cone:

Contributor: @prfesser

I'm a little anally retentive on masking tape, but the fact is that a little time and care in the application can go a long way. I've seen a few no-ejection or stuck-nose-cone problems---including a cert failure---that could have been solved by applying tape carefully.

PULL the tape snugly against the shoulder/coupler/whatever as it comes off the roll. Smooth; no wrinkles. (The paw is Smudge Pot, helping.)

If possible the edge of the (wide) tape should be smoothed over the edge of the shoulder as seen below. This reduces the rollover of the tape when the nose is pushed into the airframe. Narrow tape applied in the center of the shoulder is more likely to roll over; it's those pesky edges that are the problem areas.

482935-d3bba9bef61d32cc47572ec82df964b6.data.png


I like to CUT the tape when possible. Note the angle of the cut. The nose cone will go in more easily, and the tape is less likely to roll than if the tape is merely torn or if the cut is straight (or angled in the opposite direction).

There is an equally good argument for cutting the angle in the other direction. Regardless, it is most important to burnish down the edges so that rollover can't occur at either insertion or ejection of the nose cone.


482936-66cba9983293ae288a43998aad752d5f.data.png


It doesn't hurt to burnish the tape down with the back of a fingernail, especially the pesky edges.

Finally: Tape. Is. Cheap. If it doesn't go on right, pull it off. Throw it away. Try again. It's easier than fussing with a slightly wrinkled piece or gummed up.

Thanks @prfesser for this tip.
 
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This is index @2 for the tip-of-the-day thread.

List of Techniques (Index 2)

I am asking you each to help me post tips. Send me any ideas, and I will add them to the list.

Comments or suggestions should be posted here:
https://www.rocketryforum.com/threads/trf-tips-and-techniques-comments-thread.177678/
 
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Stir Sticks

Contributor: @dr wogz

Coffee stir sticks & popsicle sticks are great for mixing & applying glues. Go one better, and cut the round off the tip, make it square (I usually cut my tips at about a 60° angle.)

Addition from cwbullet said:
Tongue depressors work very well. If the the stir sticks are made of wood, save them in a box and they work well to start outdoor fires (I would not cook with the fire).
 
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Paint Dark Over Light

Contributor:
@dr wogz

Paint dark colours over light. Red & Yellow paints are usually more see-thru than others. Paint accordingly.

from cwbullet said:
The above advice pertains to paint and even primer. Think of it as wearing dark underwear under white paints. It will be visible.
 
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Use CA in Well Ventilated Areas

Contibutor:
@OverTheTop

When using CA glue, always apply it in a well-ventilated space, due to fumes, and make sure you wear safety glasses or spectacles. I have seen it skin over, then build pressure till it splits the skin and spits at whatever is nearby. One of my technicians had it land just under his eye one day. If it hit 5/8" higher, the story would not have had such a benign ending.

@cwbullet said:
If you do get CA glue in yoru eye, remain calm!. Rinse your eyes immediately with lukewarm water for at least five minutes if the glue comes into contact with your eye. If irritation does not subside after a thorough rinse, contact your eye doctor or visit an emergency room for further evaluation and treatment.
 
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Keep Eating Utensils in the Range Box:

Contributor:
@dr wogz

Keep a knife, fork & spoon in your toolbox.
  1. Knife: used to pry, shift, wedge, etc.
  2. Fork: the tines can be made to grab & poke things
  3. Spoon: to measure out / dispense powders & such. The back side can be used to smooth things (burnish).
@cwbullet said:
Do I need to add this? I would not use them for eating again.
 
Add Glass to your Desktop

Contributor: @dr wogz

A sheet of glass (tempered preferably) on your workbench is a great worktop: glues & paints (and other “globs” scrape off easily & nicely), it makes a great surface to cut against (X-Acto knife & straight edge).
 
Use Carbon Paper

Contributor:
@cwbullet

This technique is one I learned while building my Mariah 38. It was taught to me by Kent Burnett, who made many of the old kits for Giant Leap (I think).

In this technique, you use copy or carbon paper to make the marks on your body tube to tape it off before laying the fillets.

Parts needed:
  • Masking tape
  • Carbon Paper
  • PVC pipe or firm round ball (Delrin works)
    • size depends on the fillet size
  • the booster with fins attached
Steps:
  1. Lay the carbon paper on the fin joint where you want to mark.
  2. Drag the ball or tube along the joint to create a mark on the fin and tube. It will naturally create two lines equal distances from the center.
  3. Tape off the lines to make your fillets.
Attached is instructions with photos.

It was also discussed in this thread:

https://www.rocketryforum.com/threads/a-better-way-for-fin-fillets.144553/#post-1863665
 

Attachments

  • 435255-Great-Fillets.pdf
    8.8 MB · Views: 0
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Buy Good Tools

Contributor:
@dr wogz

Always buy the most expensive tool or the highest quality you can afford. The quantity of the money usually pays off in the long run.

@cwbullet said:
Higher prices usually equate to higher quality, but you can get some good tools at Harbor Freight (a discount hardware store).
 
Use a Wire Wrapper

Contributor: @cwbullet

Making igniter blanks is an art that is taught and honed with time. I have heard many folks swear that you need to solder your leads. I have found that it is not needed. I have found soldering a time suck I can avoid with a wire wrapping tool. The key is using a tool and wrapping tightly.

Tip of an igniter:


IMG_2676.jpeg

That does not come off there once it is locked into a pyrogen such as nitrocellulose, plasticized, or epoxy base. I have used igniters over ten years old, and they still make continuity and light a motor. I have made thousands. I average about one failed continuity per 200-300 versus one failed continuity per 500-600 soldered. My time is more valuable, so I will continue to wire wrap instead.

I use the same old Tandy or Radioshack wire wrapping tool. I lost part of it over the years, but it still works.

IMG_2663.jpeg
 
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Get a Good Set of Nippers

Contibutor
: @cwbullet

For my rocket toolbox and beside every 3D printer I own, I keep a set of Hakko or IGAN cross-cutters. These little tools are invaluable for cutting almost anything you need on the field (except kevlar). If you use them well, you can even use them to trip a wire.

I prefer IGAN 170 and 330s. You can find a cheaper set, but these will last a long time. I have used mine so much that I have worn the label off of them.
 
Filament Type Is Only Part of the Equation.

Contributor:
@cwbullet

I know not everyone has a printer, but this is for all my peeps who own one or might use one at the local share shop.

I hear many experts chime in when they come to the launch field that 3D-printed parts will not hold up to the forces of rocketry. Nothing can be further from the truth, but you do need to choose the components you will print and the method/material you use wisely.

Factors that affect the strength of 3d printed parts:
  1. Filament Type: This is a given. Not all filaments are the same. PLA is weaker in high temperatures. ABS and PLA are both weakened by exposure to UV light over time. PC and PETG are probably the best options for rocketry. PLA+ if painted, can be the best middle ground for ease of printability and heat resistance, but I would still not leave it in the car in the summer in Georgia.
  2. Additives: Blended filaments can increase printability and add significant strength. PC Blend from Prusa is a very strong material. Manufacturers add carbon fiber and fiberglass to filaments adding significant strength to the prints. On the downside, you do need to use a hardened nozzle.
  3. Infill Density: Almost all filament 3D prints are a hollow matrix with solid shell. You can increase or decrease the infill, which will affect both weight and strength. I often print my nosecones with a lower infill (10-15%), but I would never do that with a bulkhead (25-45%). In general, the higher the infill, the stronger the print, but there are diminishing returns over 60%. Infill-density.png
  4. Infill Pattern: There are many infill patterns. Probably new ones were invented as I type this. Rectilinear, Gyroid, Honeycomb or Hexagonal, and Triangular are most common. Hexagonal has the highest strength-to-weight ratio. infill patterns.jpg
  5. Layer Height: The standard layer height is 0.2mm. A thin layer will lead to better adhesion and higher density between layers. The more layers per CM or inch strengthens 3D printed parts. I have printed as low as 0.1mm (100 microns) to maximize strength, but this also increases printing time.
  6. Ideal Print Temperature: Printing at too low of a temperature will create adhesion issues in the plastic print to both itself and the bed. Not all filaments of a certain type are the same. For example, a generic PETG may be as low as 220, and others, such a Prusa PETG, might require temps as high as 245-250.
  7. Flow Rate: Adjusting the flow rate for the walls, supports, and infill can change strengths, but you have to be careful, it can also cause over and under extrusion.
  8. Increase Line Width: High line widths increase strengh because they increase the smooshing pressure to squish the hot filament and cause it to merge with nearby lines of filament. There is a sweet spot where any higher increase will decrease returns and cause extrusion issues. widthVSflow.png
  9. Reduce Cooling: Too much cooling by the print fan will reduce adhesion between layers.
I am sure there are more but these should help you increase the strength of your prints. I suggested you change one item at a time to avoid chasing your tail.
 
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Use a sharp blade!

Contributor:
@dr wogz

When cutting/using a very sharp knife, plan where a slip or a break will end up so you don’t end up slicing your arm off. Think about where the blade will be/end up if the part gives.

cwbullet said:
Although you can cut yourself with any blader, I have found that I am more likely to cut myself when using a dull blade to save a few bucks. Just use a new blade!
 
Make a Cord Stuffer

Contributor: @BABAR

View attachment 436631

My most useful low power field tool. A shock cord stuffer. Can also make this out of a big aluminum straw, cut some notches in one end, round them so they don’t cut the cord. Makes it super easy for my big fingers to get cords deep into BT-5 and BT-20 rockets. This is an old pic, my new ones are aluminum bright colors so if I drop it in the grass it is easy to find.

cwbullet said:
Proof that tools do not have to be expensive. This is a useful and cheap tool to keep handy in your tool box.
 

Cutting balsa fin stock


Contributor: @prfesser

When cutting balsa fin stock the old-fashioned way--by hand--if the blade leaves the straightedge or pattern, it will tend to follow the grain of the balsa. So make your cut toward the green arrow, not the black one. If the blade leaves the straightedge a bit, it will cut into unused balsa and not the fin itself.

It doesn't hurt to cut fins a millimeter or oversize, in case the cut goes awry anyway. Stack and sand the edges to size; balsa sands pretty quickly.

485429-bcc886eb7b722b826ef5713075bd019d.data.png
 
Tape for Motor Retention

Contributor:
@cwbullet

One of the most valuable and easy methods to retain a motor is tape. It can be used in minimum diameter or with a motor mount and both high and low power.

 
Minimum Diameter Wire Motor Retention

Contributor: @cwbullet

I found this tip in an old version of Apogee's Monthly New Letter. I have only used it for low power, but it would probably work up to mid-powerScreenshot 2023-03-17 at 6.00.17 AM.png.
 
Use Sphere to Make Fillets:

Contributor:
@Neutronium95

I like to use spherical tools for shaping epoxy fillets. This allows you to nicely contour the fillet around the leading and trailing edges of the fins, and you don't have to worry about holding the tool at a constant angle.

For mid-power and smaller high-power rockets, you can get fondant tools that will work quite nicely.

For larger rockets, I make my own tools, with a Delrin or PTFE sphere from McMaster Carr with a threaded rod stuck into it. I've drilled and tapped the holes for my first few tools, but I've since moved to just a tight fit over the rod instead.

I also use a small amount of the dye that comes with Rocketpoxy to lay out the tape lines for my fillets. Squirt a few drops onto a paper towel, wipe it on the tool, and run the tool up and down the fin roots. It'll leave nice neat lines to use as a reference when applying masking tape.

483034-75222b962cdd256226ffbc9810fc472d.data.jpeg
 
Estes Igniter tip:

Contributor: @neil_w

When using Estes BP motors, fold the igniter wire over the paper and then attach the igniter clips to the paper + wire. This will give the clips something solid to hold onto, and will keep the connection secure until launch. An extra curl of the wire on the paper (optional) will give more contact area for the clip.

0BD8A9EB-DDB2-45A6-9AC1-6B54F82C6528.png
 
Filling Spirals:

Contributor:
Multiple

One of the most vexing problems in scale modeling is successfully filling the spiral seams in body tubes. While I admit I admire that perfect finish some rocket guys get by willing and sanding, I often give up and fly the darn thing. I often can't find the time must fill, and sand tubes as well as they do; honestly, I don't particularly appreciate sanding.

In my opinion, there is no magic compound. You need to find one you like and learn how to use it. I have used almost all of them, and all of them require sanding unless you give up and live with spirals.

Options (not a fully inclusive list - from @afadeev):

100% before the fins, unless I screw something up (e.g.: wanted to apply vinyl wrap, had to give up on that, now have to go back and fill those #$%^ spirals).



I'm using the following, sometimes interchangeably, sometimes depending on the depth of spirals involved.
Listed below are the options in the order in which I resort to them as of this season:
  1. 3M 907 Bondo Glazing & Spot putty.
    1. Pros: inexpensive, quick and easy application (squeeze out of the tube), dries quickly, easily sandable.
    2. Cons: a little stinky, wasteful in application on shallow spirals (hard to apply small quantities).
  2. Paint primers, Krylon Industrial Tough Coat (KITC) in particular.
    1. Pros: inexpensive, dries quickly (unlike other primers), sands VERY easily, doesn't clog sanding paper (true for KITC, not true for other paint primers). KITC has a rubber-like component to the paint that fills spiral valleys way quicker than other primers.
    2. Cons: a little stinky, requires multiple (3+) passes to "build up" enough material in the spiral valleys. Can't be applied precisely, thus requires more sanding cycles.
  3. Tamiya Putty(white).
    1. Pros: the easiest to sand, dries quickly, can fill-in 1/8" of a valley in one pass.
    2. Cons: expensive, comes in small 32g tubes. Impractical for large airframes.
  4. Elmer's WoodFiller(white).
    1. Pros: cheap, can be dissolved with water and "painted" into the spirals.
    2. Cons: requires multiple (3+) passes to "build up" the filler in the spirals. Takes a while to dry. Can be hard to sand. Doesn't stick to glossier tubes, and will fall out during sanding unless you pre-sand the spiral valleys before application.
  5. HobbyLite balsa filler - not anymore.
    1. Pros: cheap, can be dissolved with water and "painted" into the spirals. Easy to sand.
    2. Cons: requires multiple (5+) passes to "build up" the filler in the spirals. Far too fragile (falls out of spiral in chunks), doesn't stick to tubes all that well unless you pre-sand the spiral valleys before application.
For shallower spirals I go with #2.
For deep spirals I go with #1.

YMMV.

Bondo is pretty good but can be tough to sand. If you ask ten rocket guys their favorite, your will get twelve answers.

Steps:
  1. Use medium-grit sandpaper (180-240 grit) to lightly roughen up the entire surface to be filled. I know it is counterintuitive to make more grooves to once again fill, but this will make the filler stick better. It does not take a lot of sanding.
  2. Apply a thin layer of filler. I like thinned Elmers Carpenter's Wood Filler (CWF) in the orange lid tub, but I prefer Superfil. I also have used DELUXE MATERIALS Model Lite Balsa Filler. All are easily sandable. CWF shrinks more and sometimes does not stick well without sanding. Superfil has less shrinkage and is easier to sand.
  3. I use a credit card or spreader to get a think coat into the spiral. The more you add, the longer you have to sand.
  4. Allow the filler to dry completely.
  5. Sand leaves a very slight coat of filler on the surface. I use 400 grit sandpaper. This will take a lot of patience.
  6. If you are happy with the filler, move to step 7. If not, repeat steps 3-5.
  7. Apply a thick spray of Duplicolor Filler/Primer.
  8. Sand filler/primer to surface with 400 grit.
  9. Continue 7 and 8 until you have a good smooth surface to paint.
Shop around for the best prices. I provided three links to products I use. I usually just buy from Amazon, but you might find a better price.

My way is nto always the best so let me know if you have a better way.

More threads:

https://www.rocketryforum.com/threads/tool-to-fill-in-spirals-in-tubes.177589/
https://www.rocketryforum.com/threads/hpr-spiral-fillers.175299/
 
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Spills Will Happen

Contributor:
@dr wogz

If it is going to spill, it will. If it can run or drip, it will. And it will when you are least able to deal with it.

Because of this, save the vintage ‘Van Halen 1984’ tour shirt for the bar, not the work bench! Protect all essential surfaces such as your cell, keys, or expensive reading glasses.
 
Use "Press n Seal"

Contributor:
@Huxter

Use Glad 'Press n Seal' wrap to cover rockets parts you do not want to paint. The wrap is immutable to paint. It's thicker and handles better than the thin stuff. It has a slight sticky to it, so make sure the sticky side is out - it will leave residuals on the rockets. If you haven't tried the stuff, I suggest you do! Oh yeah - it's great in the kitchen too!
 
Range Box Relay for Clusters:

Contributor: @Micromeister

This is a blast from the past from a member of the forum that has passed. I was having a trip down memory lane last night when I found his post. I will let you visit the links on your own to see the genius tool that he made.

I used to fly a lot of Clusters using estes igniters. They were fine until about the mid 80's when estes started cutting back on the pyrogen. somewhere around that same time I started noticing a greater number of BAD OUT of the Package igniters. Those that look perfectly fine on the outside ie pyrogen perfectly solid and sound, but when tested had no continuity at all.
At that point I started testing each and every igniter before and after installation in the motors to ensure good igniter continuity before they were ever put on a launcher. I've can't recall the last misfire i've had since starting the practice.
Below its the little pocket continuity tester i've been using. Very simple to make and super quick to use. The second photo is of a new even smaller AAA battery continuity tester that I've been using Same basic wiring in a smaller custom styrene plastic holder. Fits easily in any pocket.

View attachment 33790

View attachment 33791

Link to the thread:
https://www.rocketryforum.com/threads/estes-ignitor-shelf-life.16100/#post-143847
PDF Copy from NARHAMs:
https://www.narhams.org/library/tech/012-RelayLauncher.pdf
To those that cannot make one yourself:
  1. Pratt Hobbies makes a relay box: http://www.pratt-hobbies.com/proddetail.asp?prod=PRM-12
  2. Quickburst makes their Cluster Buster: http://quickburst.net/qb/quickburst-cluster-buster/
Safety Note: I test these with igniters before using them on a rocket motor. Use any igniter you can imagine, including electric matches.
 
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Better Sanding Tube Ends

Contributor
: @neil_w

When sanding the end of a cut body tube on a sanding block, keep rotating the tube as you sand. This will help you avoid inadvertently sanding a bevel onto the end of the tube. This advice applies in general to whenever you're hand-holding an object to be sanded... keep changing its orientation in your hand to even out the natural bias in your sanding motions.
 
Avoid Paint Seepage Trick:

Contributor: @Huxter with an assist by @Sandy H.

Paint base color, mask, and then spray the same color. Spraying a coat of base color will fill in and prevent any seepage under the tape. Whatever leaks under is the same color, but then the tape is then sealed. Spray the next color and it won't leak under. Clear can work too, if you want a less thick paint line, if you're airbrushing etc.
 
Quick Encapsulate Electronics

Contributor:
@Tech 68

"Five Minute" epoxy can be used to bond/encapsulate wiring that needs to be secured against vibration and "gee" forces. Careful use of a heat gun allows the epoxy to be broken down so repairs can be made. Obviously the underlying surface needs to be capable of surviving the heat.

How we bonded/secured wiring harnesses in developmental Sidewinder seekers. Integration into the guidance system was sometimes brutal... reversed feedback loops, etc.
 
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