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Build Thread: Zoom and Poof!

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rocketace

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I planned to do a build thread on these as I was building, but time got short. So, I figured I would post these fun rockets now. My goal starting out was to see how fast I could go on a J570 and to gain more experience working with carbon fiber. Yes there or more powerful 38mm motors but I didn’t want to buy a new casing. While designing it I decided I will make a second one that is shorter and specifically meant for the H999 to see how may Gs I could pull/survive. So after a lots of thinking on and off out came my designs for Zoom (Goal: >Mach 2) and Poof (Goal: >200Gs).
TheStart.jpg


Design:
The only way to reach my goals is to keep everything as light as possible with a few compromises. I did not want the added weight of a standard altimeter bay or dual deployment, so those were removed. The overall design of the rockets are almost identical except for different fin shape and tube length. Also, to save on cost, they will be sharing a nose cone.

Nose Cone: Eliminating those DD and the altimeter bay, I decided to mount the electronics (Raven & GPS) in the cone and for deployment I am using a Chute Release to reduce the landing zone. Originally everything was designed with a Mag switch in mind before the rule change. Adding a mechanical switch was a complex challenge.
NCM1.PNG
NCM2.PNG

Airframe: Rolled carbon tube using 3k Twill. I have done the sock tube, but this was my first time trying to roll a tube.

Fins: G10 plate glued on with RocketPoxy G5000. It was my first time using RocketPoxy and I was very happy with it! I did decide to add one layer of Tip-2-Tip carbon. I know it was not needed for these flights, but I figured I could still meet my goal and it would look better to me so that added a bit of unnecessary weight.

Motor retention: I am not a fan of losing casings so I wanted threaded retention to a bulkhead.

Laundry: Topflight 24” ThinMill chute, 10ft of 1000lbs Kevlar, homemade fire blankets, and a bit of dogbarf

Electronics: Featherweight Raven V4, Featherweight GPS, and Jolly Logic Chute Release. The GPS will have a magnetic switch and the Raven ended up with a homemade screw switch.


SimPoof.png
SimZoom.png
 
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rocketace

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Construction:

Airframe:
All rockets need a tube, I just wanted a fancy light weight one for this project. The tutorial by Jim Jarvis can provide a more detailed and better explanation than I can, but starting with the mandrel some waxing then added Mylar and more waxing. Then add the carbon and a final wrap of peel ply. For epoxy I used the 820 system from SollerComposites with the medium hardener. I do like the 820 and I will get it again, but that stuff does not like cool weather <90F. At room temp the resin is a supper thick gel and needs to be heated to thin out. Back to the carbon, I first made Poof with 4 layers. It cured with some bubbles in the peal ply with was a big frustration. Also I think the 4th layer was over kill. I made the tube for Zoom with 3 layers and I was a lot more careful to eliminate and prevent trapped air. That one came out a lot better cosmetically.

TubePoof.jpg
TubePoof2.jpg


Fins: I originally was planning for 1/16” G10 but the 3/32” was cheaper when I ordered the parts. Looking back, I wish I would have paid the slight difference to save the weight. After I had a design that looked good to me I traced them and cut them out. I used a 3D printed jig and strips of sand paper to create the bevels. I saw something similar on another thread and loved the idea. It worked great but took some time. I ended up removing most of the material with a flat plate, then using the angled jig to get great bevels, and lastly suing a flat jig to make sure the fin root was perfectly square for mounting.

Fin 1.JPG
Fin 2.JPG
Fin 3.JPG


Then the all surfaces were roughed up and the root was notched. Now ready to attached I had a fin guide from Wildman but wasn’t 100% happy with it, so I printed my own jig to compliment it. This worked out very well. I used some tape to make sure they were sung in the jigs, roughed up all surfaces, cleaned with acetone, and tacked on with RocketPoxy with milled glass added. I came back after and added fillets with RocketPoxy, milled glass, and fumed silica.

Fin 4.JPG
Fin 5.JPG


The Tip-2-Tip was tedious as always and likewise didn’t come out as good as I wanted, but from 12” away you can’t really see any of the mistakes, so I can’t complain too much. I did do a test with a scrap piece of tube and G10 using RocketPoxy to see how much direct side load it could handle. From the crude set up picture the joint held 40lbs and snapped at 42lbs. From running a few quick hand calculations this would be strong enough to handle and 70 degree change while going Mach 1. And with the size and thickness of this fins, I am not worried about flutter. So, t2t is just because I think it looks cool on this rocket .

Fin 6.JPG
Fin 7.JPG


Motor Retention: There are so many options when it comes to holding in the motor. I wanted something more than friction fit but I also did not want to attach the recovery to an eye bolt that could unscrew. There are many ways to accomplish or prevent these issues, but this was my idea that I decided to try. It does complicate somethings, but I still get the rocket back in 1 piece! Ok, so what I did was have a G10 plate with a center hole in it just above the J570 casing. I use a short aluminum hex bolt to hold the motor in and I made aluminum all thread extensions to use shorter casings and also the RAS system with its threaded closure.
ALBolts.JPG
 
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rocketace

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To add in strength to the bulkhead, I used a short G10 coupler section above and a very short section below the plate to help during any violent events. It was probably not needed, but it adds a lot of peace of mind. Now the Kevlar attachment is unique. I have small offset hole in the bulkhead that the Kevlar threads through and then loops around the FWD closure or the threaded spacer for the shorter casings.

Full 1.jpg
Full 2.jpg

BKheadK.JPG

Nose Cone: Its hard to pass up Wildmans 38mm for only $21. Only downside to this indestructible cone is its weight. This sucker is heavy…I will settle for now due to time, but in the future I’ll use this cone as a mold to make my own to save weight. But seriously, the nose cone with the electronics installed weighs more that the rest of the rocket minus the motor. To mount the electronics I designed my own 3D printed sled. This took many many iterations but I am very pleased with the outcome. As with the recovery attachment, there are a few things here that are more complicated than they need to be, but it was a fun design challenge. The main one being that I wanted the pressure vent holes for the altimeter as from the cone as possible, with is difficult when all the electronics are in the cone. I ended up designing an extended part of the internals to accomplish this. I also added some “fins” that add stiffness and help it fit very snug into the cone so that the sled cant wobble. Lastly, I wanted to prevent as much ejection pressure from getting into the electronics so I added two o rings. One to seal the nose cone to the sled and a second to seal the baro holes that are in the extended portion of the sled.

NC 1.jpg
NC 2.jpg


Holes: The holes for the shear pins (2x 2-56), baro holes (3x 1/16”), and the holes for the nose cone retention bolts (2x 6-32) all had to align perfectly with the two body tubes, nose cone, and nose cone sled. To not screw this up I printed a drill guide for the tube which worked out really well. After I drilled the tube, I used the holes to mark the nose cone shoulder for drilling. After the rocket was fully complete I drilled another 1/16” hole just below the nose cone shoulder to release any pressure caused by sudden altitude change.

NC3.JPG
Holes 1.JPG
 

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rocketace

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Recovery: For recovery, both Zoom and Poof will use 10ft of 1000lb tubular Kevlar with a Top flight thin mill chute (Zoom 24”, Poof 18”) which is held closed by a Chute release. All of this is protected by a fire blanket and some dog barf. Some ground testing showed that 0.5g would work good, so I will use 0.6g and be happy. The charge is placed against the motor bulkhead and the wire is ran up the tube to the nose cone. It took a lot of practice but I am now able to consistently roll it all up to only take up 4in. It does fit tight in the tube, but with a little baby powder everything slides quite nice.

Rec1.jpg
Rec2.jpg
Rec3.jpg
Rec4.JPG
Rec5.jpg


High Gs: My biggest concern on this build is the G load. The H999 is going to be one hell of a kick on this little rocket. I used hot glue to add fillets to the few large components on the Raven and GPS. I then put a few hot glue dots to help secure the two boards and their batteries to the sled. The magnetic switch is only held in place with hot glue. I also used the hot glue in a few places on the wires so that none of the wires would be pulling on the connections. I don’t know how necessary all the hot glue is, but it’s a lot of peace of mind. I also had to make sure that the altimeter sled would stay secured in the nose cone with its 6-32 bolts. I am not using any thread inserts so I was a little worried about damaging the plastic, but I was able to hang the equivalent of 400 Gs off the sled and it didn’t damage the plastic and if something does damage the sled in any way, ill just print a spare.

Glue1.jpg
Glue2.jpg


Switch: This has been a slow build and I started all the design before the mechanical switch mandate. The original plan was to use a magnetic switch for both the GPS and Raven. After lots of tinkering and thinking I finally came up with a custom switch that uses two brass plates spaced apart with a sheet of plastic and using a 6/32” set screw to connect the two plats that closes the circuit. The 6/32” set screw has a 1/16” hex drive which is the size of the holes for the shear pins. So what I did was design the switch to be in line with one of the shear pin holes. During launch prep I only install 1 shear pin. After the rocket is on the pad I arm the Raven then install the second shear pin. Its just another part of this rocket that is more complicated than is needs to be, but it works. The pictures shows a pan head instead of a set screw which I want to switch to in the future.

Switch 1.jpg
 

rocketace

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Test flights: I am not one who just puts the largest motor in and sees what happens, I usually like to do several test flights to see how the rocket preforms and to have fun burning money (I mean AP). I also think it is cool when a rocket can fly on several sized motors. I chose Airfest 28 as my launch to test these rockets out. I was able to get everything launch ready except for the cosmetics, there is still a lot of sanding that needs to be done, but I ran out of time.

Zooms maiden flight: I planned to fly a G67R to keep it under 3k so that it would stay in visual range if anything didn’t go as planned. The flight went ok, but not great. First off, It took a sharp curve north right off the rail, which I still don’t know why. Secondly, when I recovered the rocket I noticed that the fire blanket was destroyed and looking at the Raven data, the ejection was very violent and the cute was not held by the chute release and opened at apogee. After some thinking, this is what I am guessing happened: I was overly cautious for this flight so I was using a backup ejection at apogee +1.2 seconds, so there were two 0.6 gram charges really close to each other. Looking at the Raven data the e-matches blew when they were supposed to, but my guess is that because the two charges were so close together, that when the apogee charge fired it burnt though the masking tape on the backup charge igniting its powder but not the match, or at least not burning though its bridge.

IMG_0294.JPG
Zoom G67R Full.jpg
Z67F1.JPG
Z67F2.JPG



Poofs maiden flight: Based on my thoughts form Zooms first flight, this one would not use a backup charge. Poof flew on a H242T. It was a text book flight. Went up and out of sight quick, tracker lead me straight to it, no damage, and Raven data shows that the Chute Release worked perfectly.
PadPoof.JPG
P242F1.JPG
Poof H242T Full.jpg
 

mbeels

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Awesome, this looks like a fun project. I'll be following along.

Is that heatshrink around the threaded rod used for motor retention?
 

rocketace

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Is that heatshrink around the threaded rod used for motor retention?
Thanks and Yes it is heat shrink, for the smaller casings I need the longer all threads. Since My recovery loop goes around the all thread I put a piece of heat shrink on it so it wont fray the Kevlar and it slides easier to the top.
 

rocketace

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Zooms Mach test: Next up was to see how Zoom handled Mach and +50Gs. Again this flight would not use a backup charge. This flight was almost perfect. The data from the Raven shows that the main opened at apogee. I am guessing that the parachute was just not secure enough in the Chute Release.

Boost section of flight and full flight.
Zoom I300T Boost.jpg
Zoom I300T Full.jpg

Z300F1.JPG
Z300F2.jpg
IMG_9759.JPEG



One think to mention is I noticed that each flight the altitude from the accelerometer was closer (but higher) to the GPS data than the altitude from the barometric sensor.

Data1.jpg

And here is the data from the Featherweight GPS
Red: Zoom G67R
Green: Poof H242T
Blue: Zoom I300T
GPS.png


I think I am done with all the test flights…Now time to push it. I am planning on going back to Kloudbusters this weekend for their Fun Fly. First flight will be Zoom on a J825, second Poof on a H669, then last Poof on a H999.

Hopefully my biggest challenge will just be getting a decent picture!
 

mbeels

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Is that "kink" in the barometric altitude on the I300 flight evidence of the super sonic shock wave? (somewhere around 700 mph?)
 

rocketace

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Flight Updates!
I made it out to Kloudbusters this past weekend and as usual, they put on a great launch! Saturday morning there was a thick fog until noon and then it started to cleared up for some nice flying weather. Sunday started early with perfect flying weather but winds increased quickly.


First up I flew Zoom on an AT J825R. I thought I had a lot of motor for this size but the gentleman that flew right before me had a research K that was practically the same size. Zooms flight was picture perfect even though I am not good at getting a good picture. The Redline put out a beautiful red flame longer than the rocket on its way past Mach 2. This was my first Mach 2 flight and highest altitude yet at 14693ft. It pulled 87 Gs off the pad which seems like a lot, but Poof will be even more….

Zpad.JPG
Zlaunch.JPG
Zoom J825R Apogee.jpg


The GPS did loose connection with my ground station for a about 10 seconds at apogee. Those few seconds felt like 5 minutes. But it regained connection and its decent rate proved it was not ballistic. And as every flight with this GPS, it lead me directly to the rocket. Another weird note, is that with the newest app update, it keeps crashing every few minutes. I just reopen it and its quickly shows everything, but it’s still a weird glitch.

Zlanding1.JPG
Zlanding2.JPG
 

rocketace

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So with my first goal of hitting Mach 2 being successful, now time to try for 200 Gs in Poof. First the H669 then the H999. Sadly I only got the H669 flight in before winds on Sunday picked up, but it was still a great flight. As expected it ripped off the pad and Poofed out of sight.

PPad.JPG
plaunch.JPG
Poof H669N Boost.jpg


I am pretty sure the acceleration acceded the 100Gs that the raven can record, but its hard to tell with the flat thrust curve of the Warp 9. When I recovered the rocket I noticed that the Chute Release did activate and was loose, but it was all still a bundle with the parachute. Also looking at the graphs afterwards, the decent velocity never slows when it should be releasing the main. I have some work to do on my recovery set up before its next flight.

Planding1.JPG
Planding2.JPG


I think part of it, is that it is falling for so long and the shock cord gets all tangled with the cute release before it activates. I am going to see if I can fit a small 9” drogue cute in the little to no space I have left inside.

And here is the GPS flight data because its always fun to see.

GPS Both.png
 

mbeels

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Wow. Looks like you'll be well over 100Gs with the H999. Do you think it will hit 100? Are there even accelerometer based flight computers that can go that high? Looking forward to the H999 flight.

What was your flight ready weight on Poof?
 

rocketace

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Yes, I have no doubt the H999 will be over 100. I had a heavier minimum diameter rocket that pulled 125Gs with the H999. I would not be surprised if it hit close to 200. The only altimeters that I know of are the Old Ravens and Parrots from Featherweight. My new Raven V4 did not have the option, but the old Ravens had an option for a 250G sensor. I’ll be asking my local group if I anyone has one I can borrow for this flight.

The pad weights
Zoom with the J825R was 48.6oz
Poof with H669N was 25.3oz (this was in a 38/360 case using the RAS and one spacer, so it added weight vs just using the 38/240 casing)
Poof with the H999 is estimated at 26.8 oz

So far, the only flight that was not close to the sim was the one that exceeded the sensor.
Screen Shot 2020-10-14 at 5.42.45 PM.jpg
 

rocketace

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I have yet to fly the H999, but for future flights I am planning on seeing what's the smallest letter I can fly (safely). By using a light weight nose cone, no electronics, and motor ejection I am thinking I can I might be able to get down to a high thrust E.

For this I need a MMT adapter. Since I didn't have any spare 29 or 24 mm tube laying around I just decided to print some.

mmt1.jpg
mmt2.jpg
mmt3.jpg


My idea here is to wrap the casing with some tape that lines up with the grove in the adapter. This will allow for positive retention for the casing to the adapter. The adapter will have to be friction fit or I might drill/tap a hole for a set screw depending on ejection testing.
 

mbeels

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That's a fun idea. I think that there was a contest somewhere once to see what the widest range of impulse a rocket could be successfully flown on. How does your sim with an "E" look? That'd be quite a range, E -> F -> G -> H -> I -> J !
 

rocketace

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How does your sim with an "E" look?
With all the electronics and an E28T it would go 670ft @ 130mph with a rail departure of 35mph. I need to update the sim with the lighter nose cone and adapter, but I should put me at a safer rail departure. Ill launch it on a F52T or F40W before the E.

I have not run the sims on a D, but I think if I would have used 1/16" fin plate instead of 3/32" and skipped the T2T a D24T might have worked...
 

Johnly

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I did a 13 gram Estes Ninja on a 18mm E27-10T. Simulations put it a bit over 100Gs, and the little rocket disappeared. Found it at the launch the following month not too far from the pad.
 

rocketace

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I did a 13 gram Estes Ninja on a 18mm E27-10T. Simulations put it a bit over 100Gs, and the little rocket disappeared. Found it at the launch the following month not too far from the pad.
Nice! That sounds like a fun flight! Glad you found it.
 

rocketace

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Jason are you still working on this project?
I am, but weather and life have tossed in a few obstacles. My truck stated having some issues and the shop I took it too has been screwing me over. So, priority has been trying to get my truck running smoothly again.

I have been able to do some ejection testing with a motor adapter to launch with smaller motors. The adapter will be friction fit, so I too much BP is easy to do. 0.3 - 0.4 grams seams to be a sweet spot. So ill have to remove some BP from the smaller motors.
 

jbrracer

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Fingers crossed on your truck situation.
I have a 38/240 sitting here if you want, once your done with it on this project you can send it back to me or give it to someone else working on something cool.
 

rocketace

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I really appreciate that! But I am good with hardware at the moment. I even have the H999 loaded and ready to go, I just need the other stuff to fall into place.
 
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