CJ's "HOW TO BUILD A DARKSTAR 3 OR ANY GLASS KIT BUILD" STARTS

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Mounting electronics on av-bay:

Happy New years everyone!

First a few tips on mounting stuff.
I use a magnetized screwdriver for picking up all the small screws. If you don't have one ya can make it by simply sticking your screwdriver on any magnet overnight.

I have a set of needle nose pliers I ground the tips flat on. Really makes removing plastic rivets & holding tiny altimeter nuts a snap.

Finally THINK about how you wish to mount stuff! A little of mental exercise can save major headaches. Nothing worse than laying out a board, mounting, then sticking sled in the coupler ,to find out somethings hitting the coupler wall or it's not easily reachable to attach matches etc.[or download cables]

A bit of thought can save having to re-mount stuff.
Do your layout then test FIT before drilling holes. If you have to...... tape stuff on the sled.

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Assemble all needed parts and tools BEFORE you begin.

Most altimeters use 4-40 mounting hardware and some 2-56.
I find the most used nuts & bolts are 1/2 & 3/4in 4-40. These can be found at most big box stores in the little .90 bags. Buy a bunch & save future trips to the store. You always run out at the worst time.

Shown are the 2 altimeters.[ MissleWorks RRC3 & Stratologger]
Screw drivers [Red tape or paint on handles, makes finding the buggers easy when dropped at the launch on dirt or grass.]
Battery boxes I use.[some use battery clips]
4-40 hardware for sled thickness I use [ usually 1/8 G-10] .
7/64 drill bit is used for this size hardware holes.
Drill
Needle nose pliers

Stand offs, for mounting altimeters slightly above board, to keep pressure sensors from being too close to function. I also use several stacked nuts when size needed dictates, rather than nylon or steel standoff. [I will use both for mounting here]

Soldering pencil & solder [if needed]

Wire for switches & battery boxes. [size & type will always start a debate] I use match wire leads [single strand for switch, I replace them often as I twist and tape, cutting off the ends every time I fly, so there is a fresh wire end to twist.]
Stranded trailer light wire for more permanent applications. [battery box to altimeter or switch if you use them]

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Batteries & battery holders should always be mounted on the forward/nose end of sled to keep the weight/CG
forward.
This type of battery box I get from MissleWorks. At this price I get 10 at a time. I have paid as much as 5.00@ for them elsewhere. https://www.missileworks.com/index.php?main_page=product_info&cPath=2&products_id=4

I always mark sled aft & nose, so my old brain can keep track of things!
First I do an initial lay out.
2 altimeters & 2 boxes.

I place boxes & then check for fit. [I already know it will be tight but doable from previous builds]

Place sled into coupler &.......oops it looked fine on sled....but edges [battery box] are hanging up & hitting coupler.


Reposition & check again, this time a winner. Mark for drilling holes. 1/8in. makes all the difference here. Now there is plenty of battery box to coupler clearance.

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Here's another typical goof anyone who ever mounted altimeters makes....ya'll know that you've done it too!


1st. red altimeter has charge terminals to outside of sled, which is good, BUT battery terminals are on wrong end.

2nd. flipped it around, but now charge terminals are on inside, where wires will cross other altimeter.

3rd. finally red altimeter has battery terminal next to battery and charge terminal on outside edge of sled, keeping wires from getting crossed.

Thinking BEFORE mounting keeps one from re-doing stuff! 'Nuff about that.

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Holes for mounting drilled with 7/64 bit.[4-40 screws] I only use 2 of 4 holes.

Excess length from screws are cut off with side cutters & filed/dremeled flush

I do this before mounting electronics, to keep any metal shavings from being deposited on them.

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Mounting your altimeter:

First a bit if info as to the use of standoffs, those spacers that keep the alt. elevated above the sled.

Barometric altimeters have a sensor that samples air pressure. These generally don't like sunlight & therefore are put on the bottom of the board to protect them.
There are 1 or more tiny sampling ports.
If you were to mount direct with-out stand-offs, the ports may be obstructed by the board.

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There are many types of stand-offs out there commercially or you can make your own.

I use these 3 types.

1.Nylon spacers & bolts from Adept. These are #2 size. Great for Ravens & Adepts. https://www.adeptrocketry.com/MMH1cart.htm

2. steel hex type that stay on board to make moving alts sled-to sled easy.. these are from PerfectFlite & are #4 size. The bulk of altimeters out there use # 4 mounting hardware.
https://www.perfectflitedirect.com/products/Mounting-hardware.html

3. Base of stand-off stays mounted on board & you can screw/unscrew altimeter to move.

4. Just use 1 or 2 nuts on your #4 mounting screw & make your own stand off.

When ever you buy an altimeter, ask or look around the site & buy as many extra mounting sets as you may need in the future. This is often overlooked.

There are many other options but these are ones I use most.

These will be nice for the new RRC3 soon.https://www.missileworks.com/index.php?main_page=product_info&cPath=3&products_id=8

https://www.missileworks.com/index.php?main_page=product_info&cPath=3&products_id=25

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I'm terrible with using mounting templates, measuring & marking etc.

1. I just put the altimeter where I want it and using a 7/64 bit drill the darn hole.

2 &3. Then place my bolt & nut stand-off into the hole to keep altimeter in perfect alignment.

4. Drill my second hole.

5. add second stand-off nut, replace back on board.

Repeat for 3rd & 4th hole locations.

Works for me, and now I don't have sleds that looks like Woody-woodpecker worked on them!

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Altimeter is mounted just high enough for sensors to clear.

I use twist and tape wire for my switch. Run out wire through a vent hole, twist together to power up & tape to payload so I can power down should flight be aborted.

Why? I believe in the K.I.S.S. principle...less soldered joint...less things to go wrong. I also wire my charges direct to the altimeter for the same reason.

If you are using switches of any type, do the layout, making sure they line up with vents, so you can turn them on & off, if mounted inside the bay.

Holding batteries securely:

I have drilled a hole between battery boxes for wire ties & filed notches on side of sled for wire tie to clear coupler walls.

There are many other ways.....these are just mine. Less is Mo better! Lol:grin:

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Soldered wires to battery box & tinned the end for altimeter.
Wire ties used to further secure batteries in boxes. 2 ties used, 1 for each battery, sharing the center hole for neater install. Notice how they fit in the filed notches on edge of sled. Otherwise sled would NOT fit into av-bay/coupler!

I also drilled holes for my switch wires. They are first wound around a corner mounting screw, then down through the hole.
1. I do this, to lead them to bottom side of board, where they will be fished through 2 vent hole leading to outside of airframe & away from all the match/charge wires.

2. If they get a tug or somehow hung up....there is no stress directly on my terminal blocks...further protecting them. You can yank on wire till it breaks with no ill effect!


Well there ya have it. Everything ready to go & a reason why I did everything I did.

Final shot shows how the switch wires will align with the vents band holes when sled is installed.

Last words of wisdom....what ever you do...before drilling....make SURE it will fit inside coupler!


Coming next:
Rail buttons,recovery gear, shock cords & length, ejection charge sizing & install

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Happy new year CJ!

Thanks for sharing your technique and instead of just saying, actually taking the time to take pics and post to make the points c l e a r.

Had used your wire switch method for my dual deploy flight, but made the mistake of taking the tape I had prepared on the side of the av bay for external taping and wrapped the leads twisted together with it and then poked it all back in the hole thinking it was 'cleaner'. Soon as I had stepped away from the pad realized that if the rocket had to come off the pad for A N Y reason - would have to disassemble the whole bay to disarm it.

Again very helpful and you can bet I am paying closer attention now.

Kenny
 
I was about to order the tailcone adapter for this thing:

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Does the silver color match the silver tip of the nose cone pretty well?
 
1. I do this, to lead them to bottom side of board, where they will be fished through 2 vent hole leading to outside of airframe & away from all the match/charge wires.

Jim, that's a great tip on how to provide some strain relief for your switch wires.

A noob-ish question for you...I've heard of twist-and-tape but not seen it in person yet. Are there any other tips/tricks so I don't have to learn things the hard way on this? How much wire to leave outside, which direction to orient it, what type of tape, how many wraps, etc. Sounds easy enough, just want to make sure there are no gotchas that are obvious on the back side of disaster.

/reed
 
Thanks guys for all the compliments.

No worries mates... I will cover everything I can think of before this build is over, here's a list of what's left.

Shear-pins in NC.... I have to wait until I get my NC back.....[it went on tour]
How much shock cord/size & why. Kevlar or nylon.
Actual dynamics of flight vs ground test & simulations
Parachute size.
How to ground test charges
Sizing apogee charge to length of motor used. [most often overlooked, longer motor, less volume in fincan,less BP]
Rail button install
Drogue or drogueless.....when & why
Making/measuring/installing charges [how to use glove finger tips]
Battery use & how long to use.
Twist & tape method for power
Install Tracker ...where and when..... flying around water.
Packing chute/nomex and recovery gear.....
Priming/painting/clear coating
Installing vinyl decals

When finished with build, will prep rocket for actual flight & cover all aspects with pics, along the way.
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If there's anything you want added to the list, simply ask & I will cover it.
This will be my most extensive build to date, I want to cover everything.
 
Jim - I have used Twist and Tape and I like it OK - but it's a little ugly looking. I was thinking about doing a twist and rivet. Using a plastic rivet and wrapping the twisted end of my wires around it and inserting it into a dedicated hole on the bay. The idea being that I can pop it out (with the wires) to disarm if needed. I haven't played with this fully yet but it seems like it could be done.

Any thoughts?
 
Railbuttons:

I drill directly into the airframe on G-12 tubes.Put buttons where I need them, don't search for centering rings. [I used to] Over time I find this is plenty strong & have never pulled one off. Yeah...I know...let the debate begin, but it works for me!
1010 buttons are rated for 75lbs & can also be flown on 1515 rails.[little known fact, but true]. So if you find yourself at a launch where all the 1010's are taken, go out to the 1515's instead of waiting for another rack.
I am referring to standard size 1010 buttons, there are some smaller aerodynamic streamlined ones out there & they won't work, but they are far & few between.[rare]

Needless to say if you install these on this DarkStar this way, they will survive 99% of any motor that will fit. [covering my butt here]


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If you have drawn a line between the fins for buttons before gluing the fins on, you're already set. If you forget to do that, like me.....here's a simple solution.

1 center edge of paper on a fin.Tape to hold.

2 lay paper over to next fin and mark where center of fin is.

3 fold paper over....mark to mark & crease.
Crease is dead center, mark that with a line.

4 Now use that center line to mark airframe for button position.

5 move guide to upper fins, mark center there. Draw line between marks and make it 20in long.

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Use a 1/8in bit for drilling hole and self tap the screws in.

Motor tube is 17.5in long. If I put my upper button there or below, I don't need to worry about excess screw length catching my recovery gear. Yep....that's where it's going! [that's why the 20in line]

Many times I see an upper button way too high on an airframe. Closer to the bottom BOTH are, the longer time you have for guidance when launching. The only time ya need one higher is for a extremely long or heavy rocket, to aid it getting it on the rail. This is not the case here with DS 3.

So bottom button just above the rear CR.
Upper 17in from rear of motor tube & out of harms way internally. Which also coincides at or close to the CG when motors are installed. [upper button is ideally placed near CG]

edit: CG is center of gravity

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Kicking myself for not buying one of these... Looks great, Jim!
 
Parachutes & Shockcord:

Wildman recommends the Recon Recovery 40inch chute for the DS-3 or a Topflight 50in.
Recovery is 9/16 tubular nylon or 3/8 Kevlar.

These sizes are a good match for the weight of this rocket, which will be in the 9-11lb range built and flown. You figure the weight with largest motor,[ fuel weight matters not, cause it will be burnt for recovery] and ready for the pad configuration.
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Ok, my opinion only here:

Kelvar...Kevlar...Kevlar.... what's with this stuff? It has it's place,but is so overkill in most sport flying applications. It has no give [or very little] and can cut through an airframe like hot knife through butter! [zippers].

While were at it, what knot to use for Quicklinks? Boy here's a volatile subject. Well I did my own testing. I used 15ft of both Kevlar & TN....tied between my trucks bumper & a telephone pole.
I used 3 different knots. Bowline...Water...and fly tie.
Left about 4-5ft. slack in line and put truck into gear. Rolling under power, taking up slack and accelerating till line snapped. Where do ya think it broke EVERY time?

Not at either end or knot.....Right in the middle or close to middle....where the severest stretch occurs. Maybe not to scientific, but answered all my questions. For me knot strength is no longer an issue.

I use a bowline to attach shockcord to recovery Y-harness in fin can, & also to attach upper cord to NC. No need for Q-link, ya gotta tie a knot on it, so what do ya gain?
Bowline is easily undone anyhow & ya save a tad of weight.

I use a water knot for the 2 links at av-bay. I DO want Q-links there, easier prep.

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27ft of 9/16 tubular nylon for my apogee event. It's more forgiving than K. and wider so less chance of zipper on fincan should things go foul. I also will wrap tape around it where it meets airframe when deployed to keep from fraying.

27ft.[1500lb rated] for several reasons.
You will find during ground testing a shorter cord may work [if your REALLY good at it, you CAN make it work] I want the X-factor for dynamics of flight. Sometimes the apogee event will be early or late, rocket is moving at higher speeds. Extra cordage negates the possibility of shaking out the main, cause it comes to the end of a shorter shockcord violently, popping shearpins & NC.
Another reason is I fly around trees, longer cord give me a better chance of getting a rocket back..

15ft of 1/4in Kevlar[1200lb. rated] for my main. Takes up less space[easier to pack in my cut down payload]
Your already down close to ground[400-700ft] when main deploys & the 4-5ft of parachute risers make the total length = 19-20ft.
You have to be coming in ballistic to zipper a payload[usually], & by then you got bigger problems anyhow. I've flown many 3in rockets & this amount works, so why re-invent the wheel.
So there's some of the reasoning behind the madness!

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So I cut 27ft from my roll of TN. This will give me about 25ft usable after losing 1-2ft for tying knots.[another thing often overlooked].
Burn/melt the ends to keep from fraying.

17ft of Kevlar to give me 15 usable for same above reason. [knots]

If you wrap some tape around line before cutting, then cut in middle, both ends can't unravel like Kevlar is prone to doing.

Borrow the bone cutting scissors, from the kitchen knife set. They cut Kevlar & TN like butter!

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Jim,
Just wanted to take a moment to offer up a very sincere "thank you!" for doing this thread (along with your other build threads). There is an amazing amount of VERY useful information, and real world experience, here that you are so generously offering up to us all. I really like your style and approach on getting things done. Things are never presented as THE way, but rather the way the YOU do them - but always with sound reasoning and logic. What's valuable to me are often little minor details.
I know I'm not the only one who appreciates what you do here - please keep doing what you do.

One minor tip/request - a lot of photos are just a bit out of focus and/or show some camera shake. Perhaps you could look into the auto focus on your camera, or maybe use a tripod? Also, if you take a moment before clicking the shutter and breathe in easily, then press the shutter button as you are breathing out, you might have less camera shake. Or you could use a faster shutter speed.

Eagerly awaiting more posts, s6
 
I vote we all chip in and buy Jim a new camera as a thank you for this thread. :)
 
Jim,
Just wanted to take a moment to offer up a very sincere "thank you!" for doing this thread (along with your other build threads). There is an amazing amount of VERY useful information, and real world experience, here that you are so generously offering up to us all. I really like your style and approach on getting things done. Things are never presented as THE way, but rather the way the YOU do them - but always with sound reasoning and logic. What's valuable to me are often little minor details.
I know I'm not the only one who appreciates what you do here - please keep doing what you do.

One minor tip/request - a lot of photos are just a bit out of focus and/or show some camera shake. Perhaps you could look into the auto focus on your camera, or maybe use a tripod? Also, if you take a moment before clicking the shutter and breathe in easily, then press the shutter button as you are breathing out, you might have less camera shake. Or you could use a faster shutter speed.

Eagerly awaiting more posts, s6

Thanks....

one of the biggest problems I have is: I live in a 140yr old Victorian row house [BrownStone].
There are only windows front and back, so there is very little natural lighting.
A few months ago I switched my bulbs to florescent type energy savers & some LEDS. Although they seem fine to the eye, they really screw with camera. Pics come out really weird colors & the auto-focus won't focus or compensate.There are settings on the camera, but they just don't seem to work every time.
I even put 2 clamp on incandescent spots in the room for back fill lighting & that has helped immensely.

I take a LEAST 3-5 shots,[sometimes 10-15] of every step you see here to get one good one.
The screen on camera is small & you can't really tell how good a shot is till you download it on the computer .

I am constantly going back & forth from close ups to normal settings on camera. Sometimes even going back & taking MORE pics after finding none are acceptable when downloaded. BUT at times there is no way to compensate because that step is already done, I've moved on & there is no way to re-do it. I am constantly re-doing shots, do to glare & changing my angle.
I have quadruple the time in photography/set up for pics as I do in actual build time. Heck I could build this rocket in 2 days [and have in the past]

There have been 1786 pics taken to get the 209 posted. I took 8 shots just to get 1 usable for the battery box alone!

It seems the sloppy ones always happen late afternoon or evenings when all natural light is gone, & the flash just washes out a shot completely. I shoot guns ....so yes I know & do use the 3 breathes ... exhale & hold one when shooting...even use the support stick when I can.

It's the best I can do with what I have, & there is plenty of epoxy/glue on my new camera to show for it. I have been through 6 sets of batteries already too! Ya probably haven't noticed....but I've even gone back days later and added or corrected text, to many posts to clear up issues.

I vote we all chip in and buy Jim a new camera as a thank you for this thread. :)

There ya go!
 
Just to give ya an idea how much time this takes: Theses next steps would only take 15-20 minutes. Staging for pics & taking them over & over was 2 hrs. I started after my last post at 2.29 and just finished & began this post at 4.30!


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Time to show you my way of hooking up recovery gear: I use 2 sizes of Q-links.....1/8 for the Kevlar & 3/16 for tubular nylon. Only reason is larger Q-link is easier to work with on larger size nylon. Both sizes in first pic.
I will try to show how to tie my favorite knot. Boy this was a bear, hope you can figure it out. Trying to tie with one hand, and snapping pics with the other is not a simple task.

1. run cord through Q-link and leave about a 12-14in tail. You may need more if you have fat fingers to wrap around. Lol [here's where ya start losing shock cord length to knots]

2.hold with tail laying on your pointing finger.

3 &4. Wrap around finger 2 1/2 times, loosely so ya can slide tail through in a minute.

5. Bring tail up through Q-link.

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