A Level 2 Cert with Cardboard - Build Thread

[tsmith1315]

I've never liked the standard ebay sleds using a flat board and all-thread/tubes. I don't think there's a logical reason, it's just what everybody was doing way back when, and I don't particularly like doing the same thing everyone else is. At least without thinking it over. I remember thinking of things like
-a cylindrical circuit board with an open center for a pass through, or
-routing the shock cord through a cut out up the outside of the coupler, attaching it only to the top bulkhead so that no shock load was transmitted through the av bay

This time, I was insistent on blocking off a vertical section of the coupler to create sort of a well for the ejection charges. One opening upwards, the other opening downwards. Like this:



The initial reason was to keep wiring self contained in the tube and off the bulkhead. This had started with a altimeter bay I was preparing out of a coupler for a 1.9" Aerotech Arreaux. The Proton was a tight squeeze in there, even worse with the battery, but there was just enough room. Then I realized that I had insulated the charge well with thin tin, and made the altimeter mount out of copper-clad PC board, when the altimeter had a WiFi antenna for remote power on/off. I'll have to get another coupler to reboot that one. I haven't given up on either, but it's time to get something done, so...

I wiped the mental slate clean for the electronics bay and told myself to just build a simple sled for this flight, with charge containers on the bulkplates and shut up about it. So, I cut the electronics sled from G10 stock for a standard ebay. I can try my alternate ideas later, simple and quick for now. I need to be flying this thing soon!



Next up, cut the AV bay bulkheads and start affixing rings to the motor tube.

 

[tsmith1315]

https://www.rocketryforum.com/threads/hpr-custom-build.162115/

Helps not to post while multi-tasking!

Ahh yes, I have seen that. Cool! When do you expect to fly it?

 

[tsmith1315]

Attached the middle CR, forward ½-ring (just to aid in positioning the fwd CR) and cut the end caps for the electronics bay.



I used leftover black epoxy from the middle CR to plug the end of a small tube with a slice of a dowel. Both the tube and dowel were scarfed from the trash at work. After being coated in epoxy these will be my ejection charge wells.



The pink charge holders were made from scrap fiberglass cloth and leftover epoxy during another project. I rolled wax paper and then wetted cloth around a brass tube and wrapped it with another layer of wax paper. Just because. They've been sitting around for a while, and happen to be the perfect diameter to insert into the charge wells, so I'll cut some into appropriate lengths to function as disposable charge holders.


While waiting for the epoxy to cure on the centering ring, I cut the bulkheads cut with a jigsaw. Wood blade for the plywood, and tungsten carbide blade for the G10. Cut a mm or two oversize, roughed down to my traced circle with the belt sander, then squared off and fined to size on the disc sander. Internal bulkheads for the AV bay are plywood, external bulkheads are G10. No real reason for that, I just had coupler ID's already drawn on the plywood from prior thinking, and not enough ¼" plywood to make all 4.



Drilled the eyebolt holes, mounted the pieces together and fine-tuned the fit with a coupler and airframe.



Very happy to have made some movement on the avionics bay, I was dreading it. Still am, for that matter.

 

[thzero]

Ahh yes, I have seen that. Cool! When do you expect to fly it?

Hopefully Saturday!

 

[tsmith1315]

Hopefully Saturday!

That's great! Still thinking J285?

I hope it goes well and you have good flying weather. I'll watch your thread for updates!

 

[High Desert Rocketry]

My last three rockets were 4" minimum diameter cardboard rockets including the fins and dual deployment AV bay. The only thing not cardboard is the 2 liter soda bottle nosecone, nylon parachute, and 4" motor case. They flew on L-1200 ex motors reaching Mach 1.56

Only issue was leaving one of them in the back of my truck when it rained

Electronics on the first one was an Eggtimer 'Apogee' I bought for $12 on a Black Friday sale last year. The main chute taken from another rocket was deployed at apogee. No epoxy was used, only Elmer's "School Glue'

Same with the other two rockets except using a Easy Mini on one and a RRC3 on the last one doing dual deploy. Next cardboard rocket will be with a M- motor hoping for Mach 2.

Total cost of the first one was less than $25 for airframe, 'Apogee', and the propellant...not bad for a 4" Mach rocket

 

[tsmith1315]

Total cost of the first one was less than $25 for airframe, 'Apogee', and the propellant...not bad for a 4" Mach rocket

That's heroic!

 

[dhbarr]

My L2 was a couple UPS Store mailing tubes and a Big Daddy nosecone. You'll do fine :-D

 

[tsmith1315]

Trying to catch the thread up a bit before it get too far behind...

After applying an additional 30 min epoxy fillet on middle CR. It took longer to cure than I was hoping, so I worked on the electronics bay instead.

It's been a very long time since I've flown dual deployment. This DD uses an Eggtimer Proton that I put together, with wifi doodads and such. And, there will be an Eggfinder Mini in there that I also put together. Neither have been flight tested. I was planning to save it for last, but it's nice to see the bay reduced to kit-style pieces ready for assembly. It's a simple G10 plate with AL tubes attached and all-thread to clamp things down. Standard eyebolts for attachment.
I still have address how the batteries will be mounted, some combination of zip-ties and G-10 ledges, perhaps foam support or even glass cloth laid over a small form. The sled will be 4-40 threaded for the Proton & Mini mounting hardware.




If I'm not comfortable all of the DD details come flight day, I'll save it for later and just go with motor ejection. And try to keep my eyes on it.

 

[tsmith1315]

Getting back to the motor mount, I mounted it into the booster. I only tacking the middle ring in place, with a thin ring of epoxy just ahead of the fin slots. The motor tube was slid in from the back in order to push the epoxy forward and away from the fin slots. The front and rear rings were in place for proper alignment, but they were removed after cure to facilitate internal fillets.

After that cured, to finish out the middle centering ring, I poured ¼ oz of epoxy down from the front, using a piece of wax paper to keep it off the airframe where it wasn't wanted. Set vertical to settle into place and cure.



The fin tabs will butt against the rings, so I wanted that area to remain clean until the fins were mounted. Looking inside the booster from the back, you can see that some of the epoxy (dyed dark blue) has soaked through the junctions and the grain of the ring, but it's clean and ready for a fin connection:




The switchband had been wrongly painted black a week or more before, so I put a coat of Rusto white on it. It was a good painting day, so I was able to add another coat before long and it looked good. A little later and third coat, which wrinkled up right away. Ugh. Rather than fool around with it, I cut a couple more switchbands. Got one primed and then painted white, and a second one primed and painted yellow.

Later that evening, I made a little straw/paper funnel to direct epoxy onto the fwd ½ ring. Then I slid the fwd CR it into place with chopsticks. Turning it upside down so the epoxy will run back down from the ½ ring and onto the CR, and it will be ready for a fwd fillet. I will have to decide how the coupler will be integrated- glued to the fwd CR or removable.



Next up, fins...

 

[tsmith1315]

While cutting a section of tube out of the tube edge sanding tool, I stabbed my leg good with a razor knife. I was going to use the section for a drilling template/jig for installing PEM nuts to attach the drogue payload to the booster coupler.
After patching up, I changed the plan to using a piece of 3¼" phenolic tube for the jig and I use a hacksaw blade to cut it. I added a piece of LOC tubing to the inside for a shim and finished it up.



I used the jig to drill the aft end of the airframe and coupler for 6 4-40 screws. Attached PEM nuts to the inside of the coupler. This way, I can screw the lower payload section to the booster, or friction fit if I want it to separate at that joint in the future.

 

[tsmith1315]

OK, fins. I always eyeball fins. This time I made a cardboard cradle & jig to hold things up. The cradle is helpful, I don't know if I'll fool with a fin jig next time.
I'm thinking up a more substantial work cradle for future projects, we'll see if any part of it comes to fruition.





The motor tube had already been peeled where the fin tabs and centering rings would connect.




Fins were sanded well with 220/320 and scuffed with 60 grit where epoxy was going to attach:




I mixed up small batches of 5 minute BSI to tack the fin tabs onto the motor tube.







Once the 5 minute had set, I used the little paper/straw funnel from prior steps to pour about ¼" of 30 minute epoxy onto the aft side of the middle centering ring where the fin tabs/motor tube/centering ring meet. I want a good connection between all pieces at this junction. Motor tube is wrapped with waxed paper to keep off stray epoxy swipes and drips.



Over the next couple of days, I poured small external fillets. BSI 30 minute, about 0.3 oz per pair. I've never been one to make big fillets. My biggest annoyance in building rockets is probably waiting on fin fillets to cure. No pics.

 

[tsmith1315]

The ACME recovery anchor was bothering me. The instructions say to epoxy it in the forward end of the motor tube with JB Weld. I haven't bought JB Weld since I was in my early 20's and had to do an emergency radiator repair in downtown ATL. But, I bought some JB Weld like the instructions said.

I just didn't want to epoxy it in place until I was sure of position, maximum motor length, etc. Instead, I decided to make it removeable.
I put a small slice of 54mm coupler in the end of the MMT using JB Weld as a stop for the recovery hardpoint.




Then, I drilled 3 holes through the end of the MMT and ACME anchor, and tapped it for 10-24 screws.




And, I drilled access holes in the coupler so the coupler could be epoxied in place firmly against the forward centering ring, and the anchor screws could still be removed.



OK, I'm good with that arrangement. So, I mixed up a good batch of 30 minute epoxy and committed the coupler to the booster with the fwd CR fillet. Everything lines up, good to go.

 

[tsmith1315]

With the front end of the booster done, it's time to finish up the back. So, I poured internal fin-motor tube fillets over a couple days using the handy little paper/straw funnel to keep the epoxy off the aft centering ring attachment points.

I still have the aft centering ring, rail guides and any positive retention to go. However, since most of the epoxy weights have accumulated and there's not much left to add, it's a good time to re-evaluate in Open Rocket.

Updated with as much info as I have now, this is how it's predicted to perform on all the AT 38/720 and 54/852 reloads:



I don't see anything there that I would be unhappy with. If there's good visibility, I'd be comfortable using motor or apogee ejection on many of those.
Just based on old times, I'm partial to the J350W and J460T.

Chris is low on 54/852's but shows plenty of the 38/720's in stock, so I'll probably just pick one when I get there and worry about other things now.

 

[tsmith1315]

Well, no test flights this past weekend. I called in a NOTAM on Friday in hopes to be ready to test on Sunday, but nowhere near ready. It was a beautiful day, too. No appreciable working time Friday afternoon or Saturday, but I did get the build thread caught up to real-time.

On Sunday I got the aft centering ring in place, with a good bead of epoxy on all mating surfaces in there. I added a coupler slice to double-wall the last inch of airframe for durability, since it extends past the fins, and added one last centering ring just for retention. I'll have to use 4-40 screws for retention because there's not much room in that space. The last ring is also 3/8" thick, and will have a nice layer of epoxy on top. I'll drill & tap that for 4-40 and use long screws for retention clips.




Made clips from hanging office file folder supports. Bent them to fit with flat-nosed pliers. Still unsure whether it will be a 38mm or 54mm flight, so I made a long set to use with the 38mm case plus a LOC adapter. I've always been a friction fit flyer, but something was making me do this to have the option.






I also epoxied the ACME Rail Guides in place with JB Weld, as ACME recommends. I think I saw those tiny inspectors give me a thumbs up.

 

[tsmith1315]

Itching to get a coat of primer on the booster tonight. I went outside and it's 54 degrees and pretty windy.

As I tried to get a coat on under the carport without getting overspray on the car, lawn mower, brick, etc... I noticed a door out there and realized that I have a nice paint booth at the moment. Well at least a primer booth. Our outdoor utility room is mostly cleaned out right now and a little overspray wouldn't hurt those walls or floor! Nice controlled environment.

 

[tsmith1315]

Oooh, and two coats of black on tonight!

 

[mccordmw]

My goal is to L2 Cert on my Binder Design Velociraptor (伶盜龍) with cardboard (hardened with wood hardener). I've heard that BD kits have been able to handle some seriously large motors without being glassed.

I have a Binder Design Excel. It eats H to J motors without batting an eye. It can take K motors just fine if you build it well. No special reinforcement needed. Binder makes fabulous rockets.

 

[Sooner Boomer]

Itching to get a coat of primer on the booster tonight. I went outside and it's 54 degrees and pretty windy.

As I tried to get a coat on under the carport without getting overspray on the car, lawn mower, brick, etc... I noticed a door out there and realized that I have a nice paint booth at the moment. Well at least a primer booth. Our outdoor utility room is mostly cleaned out right now and a little overspray wouldn't hurt those walls or floor! Nice controlled environment.

View attachment 491271

Wow!

"Great Minds", eh?

 

[tsmith1315]

Wow!

A little day zha voo?

 

[tsmith1315]

It's time to tie it up, now or never... well, now or much later.

The rocket itself, Floyd, is complete:


Maybe the white ring in front of the rail guide was supposed to be at the forward edge of the fins...

In any case, I can tie the recovery stuff on and fly it with motor ejection as it sits. That would qualify for L2, if I could walk far enough to retrieve it. There's a real possibility that it will indeed fly that way for my cert flight. Simple, less to go wrong.

The only reason I don't stop now and tie it up just like that is concern for bringing it back on the field from 5000'. I've only flown that field once, I don't know what the wind will be like, or where the rockets will be drifting tomorrow and Sunday.

 

[tsmith1315]

Or, I can start down the slippery slope...
Using the Eggfinder Mini Tx would help with that, using motor ejection. It's simple, self contained, and pad times should be short enough that I can use it without a switch. OK, that's still simple and won't compromise the L2 if something goes awry. Simple enough. The coupler has to be in there anyway, might as well attach the Mini and turn it on.

I'll just add the Mini. The battery will need a secure attachment... I have some dense foam about the right size hoarded away, I'll just lay that out and see if it looks workable... just the Mini transmitter and the big, flat 430 mAh battery.



That will squeeze perfectly between the tube on the sled, just needs a clamp over it. I can cut a piece of G10 for a clamp and drill/tap the sled. Wow, that was easy. Hmm, where are those other batteries?

There's that slope. I don't think it's linear.



Now there's a lot of wiring, connectors and soldering to be done. another clamp and set of holes to drill & tap. Do I have enough screws, are they long enough. Can't forget I have to go back to the office and do payroll today.

Not to mention the test. TEST? Yipe! I answered the questions when I received my L1 packet last year and did well, but well enough to pass? I should quit typing and read over that while I work.

But ADHD wins, and I test fit the 54-38 adapter with the motor and the retaining clips. Don't want any surprises on the field.




Well, that was a good idea, those screws are tight through the last ½ of the thread, and this one just wouldn't go any further:


One more thread test and back to the sled. And the recovery system - the cord and 'chute are a very tight fit.

edit: And after looking at that picture, a little makeup on the butt wouldn't hurt.

 

[Orien]

a little makeup on the butt wouldn't hurt.

Thank you! I thought I was the only one who did that. Started to think I was a weirdo. Or did you mean on the rocket?

 

[OverTheTop]

Have you put vent holes in each airframe section? That's something that I tend to almost forget during builds.

 

[tsmith1315]

Have you put vent holes in each airframe section? That's something that I tend to almost forget during builds.

Good catch! As of that last post, no I had not.

And I had forgotten about them until later that day, while drilling screw holes to attach the electronics bay to the upper airframe. I quickly added a 1/8" hole in each of the upper sections roughly 3" dia x 15" long.

 

[tsmith1315]

Well, my goal was to do the cert flight last weekend at the Turkey & GRITS launch.

That didn't happen, primarily due to logistics. It would have been a motor ejection flight, because there was no ceiling and no wind. A quick up and down would have been an easy one.

But I couldn't be disappointed, because I was at a great launch on a most beautiful day.

Instead of burning a J-motor, I came home with some lovely consolation prizes, hazmat-free:

 

[tsmith1315]

Ok, thread update... It's 6 months later and Floyd finally flew. It wasn't a L2 cert flight, just a test flight to check my handywork and be sure I know how to operate the Proton.

Brief rundown:
Using the H550ST shown above,
Both separation points are friction fit,
Eggtimer Proton in dual deployment mode,
Drogue at apogee + 2 sec,
Main at 500'


All went well, apogee at 1905'. Unfortunately, time was short and the only picture I have is at recovery:



I'll update the thread once more when the L2 flight is done, probably in November.

 

[loopy]

Nice! I love my cardboard rockets...I did my L2 on a relatively stock LOC/Precision Expediter ("relatively" meaning I turned the transition into an altimeter bay for dual deployment), and I have a scratch built 3x upscale of the Estes Sizzler (from the mid-'80s starter set) that flies on 38mm J loads all the time! Can't wait for November when you get your L2 with this!

 

[rocketace]

For my L1&L2 I had CF reinforced cardboard rockets. It was more for looks and my L3 was cardboard / plywood / foam.
Make sure you get some pictures of the Cert flight!!

 

[tsmith1315]

Nice! I love my cardboard rockets...I did my L2 on a relatively stock LOC/Precision Expediter

Cool!

So did I! L1 on H238, and L2 on J275 in a stock LOC Expediter in ~'96.

aaaand, I used that same old Expediter for my current L1 cert in 2020.

I was about halfway done with the same transition mod for an AltAcc when I stopped flying for a while. I'd be interested to see your bay if you have pics!

my L3 was cardboard / plywood / foam.
Make sure you get some pictures of the Cert flight!!

Very cool! I'll get pics for sure, thanks!