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

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Cheap Fin Hardening Techniques:​

I have found some of the best tips in the Annals of Time in the basement of TRF. @Constr Star initially posted the Cheap Fin Hardening Thread posted thus in late 2004.

Three tips for hardening your fins:

1. A thin layer of evenly spread wood glue.
2. Wood glue spread evenly, followed by a sheet of paper pressed evenly and let dry. After it is dry, sand away the paper. And if needed, wet sand to get smooth.
3. Epoxy spread evenly, followed by a sheet of paper pressed evenly and let dry. After it is dry, sand away the paper. And if needed, wet sand to get smooth.

I have not tried them, but if you have, post the results. If you have a better tip, let us know. Post them here:

https://www.rocketryforum.com/threads/trf-tips-and-techniques-comments-thread.177678/page-9

 

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Finding the center of a bulkhead:

Contributor: @cwbullet

The method I use is in this video:

 

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Kaplov Clip Retention:

Contributor: @Stymye and others in this thread from the past.

Want to go cheap and need motor retention? You can use mirror clips or brass strips to make retention clips. I found this search through old threads. This technique is as relevant today as it was in 2011.

https://www.rocketryforum.com/threads/fabricating-kaplow-clip-retention.18733/

 

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Consider Rear Ejection:

Contributor: @cwbullet with a blast from the the past,

When reviewing some old threads, I found the following:

https://www.rocketryforum.com/threads/rear-ejection-and-recovery.56397/#post-1818434
Rear ejection is a great recovery technique for odd rockets such as spools, rockets with fins that protrude from the bottom, and short-fat rockets. The basic concept is that the centering rings and motor tube are ejected with the recovery gear out the back. This allows the nose cone to impact the receiver and reduce impact force on the base or fins. A good example of an illustration was documented by @lakeroadster in the following thread:

https://www.rocketryforum.com/threads/rear-eject-spool-design.175631/
More examples:

https://www.rocketryforum.com/threads/rear-ejection-and-recovery.56397/#post-1818434

 

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Drilling a hole in a tube:

Contributor: @cwbullet

This problem is a common issue for rocketry folks. This issue is that a handheld drill is challenging to get a straight hole, and the tube often rolls when you try to drill them.

One solution is to use a drill press and hold the tube still. There are many jigs or tools that you can buy to drill a hold the tubing still. I especially like the many V-shaped holders that can be mounted to your drill press. They are made to drill pipe, but what is an airframe but a specialized pipe?

A tube drill guide is another interesting device that will work with a handheld drill guide. You can also 3D print something similar.

 

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How to bevel fins:

Contributor: @cwbullet - I am adding this, but I acquired it from Info-Central and this site.

You can always do it by hand but many of the users on this site have found ways to that is more reproducible.

John Coker has a great how to on his website:

http://jcrocket.com/finbevels.shtml
3D Printed version that is similar:

https://www.thingiverse.com/thing:5993440
This is only a few options so let me know if you have another.

 

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Cutting fin slots:

Contributor: @cwbullet

Cutting fin slots on a blank tube for a scratch build can be as simple as using an aluminum angle and a knife or as complex as using a jig and a router to slot a tube. It is not easy to do it by hand alone, but you can use a ruler to make your lines and slice the tube. There are a few YourTube videos that might inspire your next build:







If money were no option:



The best method on cardboard tubes is to mark your lines with a straight edge. Then, use an aluminum angle and a hobby knife.

 

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3D Printed Parts Shrink:

Contributor: @cwbullet

Ok, I learned this one the hard way this weekend. I had plans to build a rocket. I had the parts all printed out. I accounted for everything but incorrectly estimated shrinkage with a new filament. Unfortunately, the parts I am printing are out of ABS, and the ABS I am using must have a shrink rating of about 1.6%. Well, a few more parts for the landfill.

Below is an article with a chart to help you estimate how much you need to increase the size of your prints.

https://filament2print.com/gb/blog/136_warping-contractions-3D-printing-parts.html

 

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Consider tinning, twisting, or adding ferrules:

Contributor: @cwbullet



One common error I have seen when wiring electronics occurs using stranded wire with a screw terminal. Users will inadvertently set off a charge or arm the altimeter when one of the strands "jumps" the connection. An excellent way to prevent this is to ensure no extra strands. You could use a solid wire, but some prefer stranded wires, and they do have their benefits.

Techniques:

1. Tin the tip of the wire. This technique is where you tin the tip of the wire to hold all the strands together. This is not the preferred method - see below.
2. Twist the wires together. It is what it says it is. Twist it with your fingers or a tool. To me, this is a temporary fix on the field. Long term, I would use one or the other. It tends to come undone over time and even leads to broken wires where you repeat the process over time.
3. Add a Ferule: This is an easy means that provides long-term protection. The best part is that it does not require a soldering iron and can be easily done on the field. I prefer this method because it makes a nice sturdy connection to the screw terminal.

Video on Ferules:

I'll make a comment that tinning wires that go into terminal blocks is not recommended. The solder creeps under pressure and can lose contact with the terminal over time. The wire also flexes where the solder stops and if the wire is moved or suffers vibration it can break at that point.

If you do tin the ends, support the wire and check that they haven't failed at the bend points, and tweak the screw on the terminal block occasionally.

Ferrules are the preferred method, with just twisting the wires the second. You can pick up a set of ferrules and a crimper for about $20 on eBay.

I actually agree with @OverTheTop - Ferules are the preferred method.

 

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Using Old Epoxy:

Contributor: @cwbullet

A local flyer told me he threw out all of his old epoxy. He proceeded to tell me that he could not mix the hardener. It was too hard. Can it be used?

Old epoxy tends to change color, and the hardener might even thicken. That is a normal part of the aging process for those bottles you buy. Can it still be used? Maybe, but I would not just throw it in the trash. I also would not use the epoxy on a level 3 build or expensive carbon fiber lamination.

Use a small test mix to see if it is still good. I heat mine in a baby bottle heater. I got one on Amazon for less than $30, but you can probably buy one for less than ten at Goodwill. I will heat it for 10 minutes and see if the hardener thins. If it does, I mix a small amount and see if it hardens. Be aware that it will probably harden faster with the heat added.

 

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This is index #6 for the tip-of-the-day thread.

List of Techniques (Index 7)
�

Page 1		Link to page 1 index
Page 2		Link to page 2 Index
Page 3		Link to page 3 index
Page 4		Link to page 4 index
Page 5		Link to page 5 index
Page 6		Link to Page 6 Index
181	31 July 2023	Using Old Epoxy
182	1 August 2023	Red marker for black powder staging
183	2 August 2023	Need a decal, consider a wrapper.
184	3 August 2023	Consider Where You Want Glue to Go
185	4 August 2023	Upsize the Motor Mount
186	5 August 2023	Protect those initiators
187	6 August 2023	Plumb Those Fin Lines
188	7 August 2023	Save your reload packaging!
189	8 August 2023	Use a Drone
190	9 August 2023	Color your epoxy
191	10 August 2023	Making or Painting Curves
192	11 August 2023	Wipe the Glue
193	12 August 2023	Chamfer the edge
194	13 August 2023	Clean your nozzle
195	14 August 2023	Simple problem-solving in rocketry
196	15 August 2023	Tip for first layer failures in 3D Printing
197	16 August 2023	Make a spray booth
198	17 August 2023	Dowel and Flower Pot Stand
199	18 August 2023	Don't forget the dollar store.
200	19 August 2023	Body Tube Sizing Reference
201	20 August 2023	Vacuforming Nose Cones
202	21 August 2023	Centuri Guidebook
203	22 August 2023	An anchor can be a weak link
204	23 August 2023	Lengthen the Shock Cord
205	24 August 2023	Cheap Adaptor
206	25 August 2023	Use Silicone Bowls.
207	26 August 2023	Cracked Fillet Repair
208	27 August 2023	Fiberglass Hotbox
209	28 August 2023	Don't Stretch Electrical Tape
210	29 August 2023	Micro Applicators for Touch-Ups
Page 8		Link to the next index

If you have an idea, could you each please help me post tips? Send me any ideas, and I will add them to the list.

Comments or suggestions should be posted here:

TRF Tips and Techniques Comments Thread.​

Guys, we will use this thread for comments and suggestions against the Tip of Day thread in the Techniques forum. This goal is the maximum value and limited side chatter. If you have a comment, post it here and add a link to the post you are commenting about.

 

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Red Marker for Black Powder Staging:

Contributor: @BABAR

If you use black powder staging, invest in a red magic marker. Mark the butt end of the casing and the clay of the zero delay booster with the red color because you may not see the color code once the motor is inserted into the booster.

Then, after you load the motor, especially if you prep well before a launch, you can do a last-minute check, “Am I SURE the booster motor is a zero delay?” You can quickly look at the bottom of the booster and be sure.

 

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Need a decal, consider a wrapper:

Contributor: @cwbullet

I have seen this done on our field and never considered it as a tip until I saw a thread from the past:

https://www.rocketryforum.com/threads/candy-wrappers-as-rocket-body-wraps.102422/#post-1158370
A guy that flies in SC, often uses chip bags, wrappers, or cardboard tubes from products to make rockets. It is easy to avoid painting and decals and still look snazzy. A Doritos rocket might be in your future.

 

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Consider Where You Want Your Excess Glue to Go

Contributor: @OverTheTop and @SolarYellow

When gluing two parts together, there is usually an inside part (eg coupler) and an outside part (eg airframe). Carefully consider where you apply the glue before mating.

• If you apply the glue to the inside of the outer part then the excess glue goes inside the assembly when you mate them.
• If you apply the glue to the outside of the inner part then the excess glue stays on the outside of the assembly.

Think about this up front, in regards to how you want the joint finished, cleanup, and any other requirements you may have.

@SolarYellow added: And if you put it on the inside of the outer part and on the outside of the inner part, it goes everywhere. Which you may want. For example, with a long, sliding joint, the LE of a non-glued inserting part may tend to push the glue ahead of it. If that inserting part also has glue on it, it will tend to supply glue into the joint as it enters, helping make sure the joint is properly filled.

This tip I especially important if you are wearing your favorite shirt. Wearing his shirt almost guarantees that your drop a drop or squirt a little onto your clothing.

 

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Upsize the Motor Mount:

Contributor: @cwbullet

There is a tendency to use the exact size of motor mount for that motor you plan to use on launch #1. If you plan to launch it with a G-80 and a 29mm motor mount, consider using a larger motor mount if the rocket will hold it and stay stable. You can use an adaptor. This will expand you possibilities in the future.

 

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Protect those initiators:

Contributor: @cwbullet

Most of us have pulled an old igniter / initiator our of the bag to find most of it left as a powder in the bottom of the baggie. As ignitors age, they can become brittle and fall apart. Don't let that despair your because you can add a protective layer to them and prevent this form happening.

Tips to prevent this:

1. The first and most crucial thing is to leave them in their protective straw until you are ready to use them.
2. Buy them as you use them.
3. If you need to stare them for long periods, consider coating them with a protective layer.
   • Fingernail polish
   • Nitrocellulose Lacquer
   • Duco Cement

I am sure you have one also, please share it.

 

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Plumb fin lines on larger-size body tubes.

Contributor: @John Kemker

When drawing lines to cut fin slots or fin attachment points, take a tip from Amos 7:8
“And the LORD said unto me, Amos, what seest thou? And I said, A plumbline.”

Set the body tube on the end away from the fin lines where it hangs off the edge of a table just a bit. Make sure the top of the tube is level. Then, tape a plumb line over your mark where the line is supposed to go. Please wait for the plumb bob to stop its oscillations. If you've chalked the line, lightly snap it to transfer the line to the tube. If not, as in my picture below, make a mark along the line so you can line a ruler up between the two marks and get a straight line.

 

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Save Your Reload Packaging!

Contributor: @John Kemker

Loki 38mm reloads come in tubes that are perfect for 38mm motor mounts. Save them after you've used the reload.

They also make good body tubes for what I call "trash rockets"

 

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Use a Drone:

Contributor: @SanRocketMan

Not necessarily a building technique but it is a recovery tip. Who likes walking to find and retrieve their rockets? Often long walks in undesirable conditions! Not me. Does anyone use a drone with a parachute shroud hook mechanism to locate and recover their launched rockets?

I have seen it used to look but not necessarily to recover. This is a great idea but I need to get one with a hook or grabber for Skill Island.

 

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Color your epoxy:

Contributor: @cwbullet

There are many options to color your epoxy. You can use glitter, pigment powders, or event liquid pigments. Coloring your epoxy will allow you to see where it has been applied. When you get good at it, it can allow you to skip painting the fillets.

You will want to check to see that it is compatible with your brand of adhesive. A small test batch should confirm it.

 

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Painting Curves or Masking Curves:

Contributor: @cwbullet

This tip is a blast from the past.

The key is patience, practice, and using the right material. You could mask it off with thin masking tape or use this miracle material called Frisket Film. It is a low-tack masking material used in airbrush painting.

As recommended in the original post, I have also used Tamaya and Pactra tape. Frisket works better.

 

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Wipe the glue

Contributor: @prfesser

To ensure a good bond, apply glue liberally to the inside body tube, then a very thin wipe over the outside coupler. Just enough to give it a sheen. Little or no excess glue squeezes out, but the surfaces of both parts get complete glue coverage.

 

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Consider Chamfering the Edge:

Contributor: @SolarYellow

Another prep detail is to chamfer the ends so you get a wedge of glue that wants to stay in the joint, rather than a sharp corner that tends to squeegee the glue ahead of the joint as the parts are mated. Chamfering the glued edge will create a space for the glue to stay and "stick".

 

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Clean your nozzle:

Contributor: @John Kemker

This tip applies to 3D printing but could be used for other equipment. One of the most common mistakes is to ignore maintenance. One piece is to clean your nozzle and hotend regularly. You'll get less messy prints in the long run.

 

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Simple Problem Solving in Rocketry:

Contributor: @cwbullet

You have discovered an error or something is not working right. It may be helpful to break larger problems down into smaller pieces or steps. This allows you to focus on resolving each smaller piece of the problem or ruling them out individually. This allows you to break to portenial causes into more manageable bits. Start by identifying what the "problem" into potential causes. The simplest solution is often the right one.

For example, you have a CATO. Nearly every flier jumps to I have a faulty motor. It is easier to blame someone else for the failure. That is often the hardest thing to prove. I walk back through the storage and assembly of that motor to determine potential things I might have forgotten or missed. It starts with re-reading the instructions and examining the cause and parts that are left over.

Also, always put in a mess report even if it is your error. It might help manuafactures change their labeling.

 

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Tips for 3D Printing First Layer Failures:

Contributor: @cwbullet

I know not everone 3D prints, but this simple method of approaching poor adhesion will work with any 3D FFA printer. Most printer owners jump to the thought that they have a bed that is not flat or a lemon of a printer. I have purchased two lemons off eBay and was gifted a printer from a coworker (a Bambu Labs P1P) that each had an adhesion issue that took me less than 30 minutes to solve.

1. Check the Z height and Pinda Position
2. Check the filament and print settings - Wet filament, the wrong filament, and the slicer settings can cause it to not stick (Even new filament can be "wet")
3. Clean the bed: Soap and water with a sponge every 1-2 weeks, IPA the rest of the time
4. If all fails, redo your first layer calibration

I would guess that 90% of problems are in 1, 2, and 3. There is nothing like a coworker begging to truck off a 2-3 month old P1P.

 

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Consider a DIY Spray Booth:

Contributor: @cwbullet

This tip is more of a blast from the past. Make a spray booth to paint rockets. In the SE, the humidity can be tough on painting and bugs and wind can really hurt your paint surface. I found this thread that might inspire you:

https://www.rocketryforum.com/threads/youve-seen-others-heres-our-spray-booth.112599/

 

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Dowel and Flower Pot Stand:

Contributor: @ljwilley

A straightforward way to make a paint stand with a large flower pot and a dowel:

1. Find a large flower pot with a large hole in the bottom.
2. Find a dowel or pipe that will fit your rocket and fit through the hole in the pot.
3. Turn the pot upside down and place it where you plan to paint.
4. If you plan to use the pot later for something, cover it with something so it doesn't get painted. (Optional)
5. Stick the pipe or dowel down the hole in the pot and place your rocket on top. Now you are ready to paint!

*Depending on the size of the dowel/pipe and the pot, you can use this stand to paint rockets from micro maxx size to massive high-power rockets!

 

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Don't Forget the Dollar Stores!

Contributor: @John Kemker

Dollar Tree sells most things for $1.25 US. In their automotive/hardware aisle, they often have zip ties in several sizes. The Dollar Tree versions are inexpensive if you do not need permanent zip tie installation. This also goes for small screwdriver sets, as is often required for hooking up avionics, as well as small pieces of plywood and other items. Their Crafter's Square section usually has sheet metal decor that can be easily cut and repurposed for various uses.

This tip is not a building technique, but people often miss the value of Dollar Stores. I buy everything from epoxy mixing containers to rocket parts. My wife and I often walk down the Isles and comment, "I can make that into a rocket" or "That will be useful to make x." You can make a family game of the trip. By the way, cheap fingernail policy often contains nitrocellulose.

 

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EROCKETS BODY TUBE SIZES

Contributor: @ljwilley

The Erockets body tube size chart is a VERY good way to find the perfect size body tube for your project! If you need an "oddball" size body tube for an upscale or downscale rocket, you can scroll down this chart until you find the right size tube. Most of the tubes are in stock at Erockets, and they have enough sizes to get at least really really close to the exact size you need. I have used this to find the body tubes I needed for many projects.
Here is the chart: EROCKETS BODY TUBE SIZES

Another good one:
https://www.nar.org/wp-content/uploads/2014/05/BodyTubeRatios-WOOSH1.pdf