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"Tubestack" mid-power scratch build thread

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HHaase

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You know, sometimes there exists sentimentality where you least expect it. In my new workshop / lounge area I have a nondescript wooden box. There are two things special about this box you don't know at first glance. The more important one is that Dad built this for me close to 40 years ago, it's my childhood toybox, my sister had a matching one. I have a lot of memories attached to this box, and one of my oldest memories was seeing the two matching toyboxes in the corner of our den acting as walls, holding a puppy. That little schnauzer was one angry little a-hole, and he's been gone for decades. Anyway.... that's too much of a tangent.



The other special thing about this box, is it's my rocket box. I keep all my un-built kits in here, as well as all my leftovers and spares. It's incredible how just a few repairs and clones can build up a big pile of body tubes you weren't expecting to have.



And this is my next build right here, it's a stack of tubes. So let's call this build "Tubestack". Original name? Yes. Good name? who cares, let's build a rocket!!!!!

 

HHaase

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So, what all do we actually have here, anyway?
Mostly a selection of BT-60, BT-80, 3" and 29mm.

....... 29mm motor tubes.......



Thought #1 that occured to me is how nicely a trio of 29mm motors fit into BT-80.
But I'm not exactly cluster experienced and a triple motor set really can ONLY fly as a triple motor set.
Can't fit 4 in here, which would have been nice because I could do a pair or a quad.
Good warmup for that 4-29SS I still need to finish.



Another thought I had was tube fins. Lots of 38mm tubes here, and they kinda stack up nicely against that 3" tube.



So, why not combine those ideas, shall we?
Quad 29mm's in a 3" tube. But that 3" is a weeeeeee bit short, and my brain screams 'stability margin, stability margin, stability margin.'

 

HHaase

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Ahhhh yes, I have a rather good length of BT-80, don't I?
I'll need to figure out a transition and some centering rings, and there's no doubt in my mind it'll need more fin area for sure.
But I think we've got ourselves a rocket. My head is full of ideas now to build off this base pattern.

Time to start burning some time in openrocket and see what it'll take to make this guy safe.

 

HHaase

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Ok, OpenRocket gets me stability, but weeeeeeeee doggy does it get me some altitude with even mild 2-motor clusters.
I've got my high fliers, and have some even-higher fliers in mid-build. I want a bit more field friendly of a design here.
The last thing I want is another fantastic rocket hiding in the corner because I can only fly it with a road trip.

So let's dial back to a single motor, shall we? A single Aerotech F23 gets me a good 600ft flight and almost over-stable.
Or I can run a 24mm adapter and CTI 6-grain G65 and a really beautiful looking profile up to 1500ft.
Honestly I really like the flight profiles I'm getting in the F-G motor range.
That and I really like the fin pattern too. Just some basic trapezoids really, but I like the look.

I think I found my rocket.

 

HHaase

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I'm going to impose some FUN rules on this build for myself, to keep it in the spirit of using up things I already have.
So purchasing components must be kept to a bare minimum. At current I think I can get away with ONLY buying a chute and some thin ply stock for the fins.
I'm also going to 3D print as much as possible. Again, because it makes this build more fun to me, your mileage may vary.

-Hans
 

rstaff3

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Again, because it makes this build more fun to me, your mileage may vary.

-Hans
And, that is the only reason to build any rocket as far as I'm concerned. I like this kind of build, although I usually don't have that many actual rocket parts :)
 

HHaase

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Did I mention how much I love doing 3D printed stuff? First try at these centering rings had a slightly under-sized hole for the motor tube, but 2nd try was spot-on.
The motor retainer came off thingiverse, and is very similar to Estes retainers.
Normally I buy the Estes ones, but keeping with the theme of the rocket I decided to print this time.




Add it all together and I've got me a motor mount ready to epoxy together and into the lower 3" tube
This is all ABS plastic. In the past I probably wouldn't have used plastic for motor mount centering rings.
But after all the flights I've done with the plastic Estes retainers I'm pretty comfortable with the material in this build.
Lots of examples out there on the web of people flying extensively 3D printed designs.

 

dhbarr

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Did I mention how much I love doing 3D printed stuff? First try at these centering rings had a slightly under-sized hole for the motor tube, but 2nd try was spot-on.
The motor retainer came off thingiverse, and is very similar to Estes retainers.
Normally I buy the Estes ones, but keeping with the theme of the rocket I decided to print this time.




Add it all together and I've got me a motor mount ready to epoxy together and into the lower 3" tube
This is all ABS plastic. In the past I probably wouldn't have used plastic for motor mount centering rings.
But after all the flights I've done with the plastic Estes retainers I'm pretty comfortable with the material in this build.
Lots of examples out there on the web of people flying extensively 3D printed designs.

Hrmm, 3d-printed I-beam supports for stock paper rings would actually be pretty interesting. Weight should come in under ply.
 

rstaff3

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Did I mention how much I love doing 3D printed stuff? First try at these centering rings had a slightly under-sized hole for the motor tube, but 2nd try was spot-on.
The motor retainer came off thingiverse, and is very similar to Estes retainers.
Normally I buy the Estes ones, but keeping with the theme of the rocket I decided to print this time.




Add it all together and I've got me a motor mount ready to epoxy together and into the lower 3" tube
This is all ABS plastic. In the past I probably wouldn't have used plastic for motor mount centering rings.
But after all the flights I've done with the plastic Estes retainers I'm pretty comfortable with the material in this build.
Lots of examples out there on the web of people flying extensively 3D printed designs.

Now you're just bragging. But that is pretty cool. :)
 
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HHaase

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I also epoxied a lot of things yesterday.
I epoxied the motor mount parts together, and installed them in the lower body tube.
Also epoxied each pair of tubes to each other.

Still using my favorite epoxy. G-Flex by West Marine, but in this case re-packaged as "Flex-Epox" by TotalBoat.
Same stuff, going by the datasheets, but cheaper in the off-brand.

I really like this "no instructions or examples to follow" kind of build.
I decided it would look better if I moved the tubes and fins forward about 2".
So I moved the tubes and fins forward about 2".

 

LithosphereRocketry

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Looks interesting so far! I don't think I've seen too many rockets with the "2 pairs" tubefin approach.

I like the 3D printed parts! I considered 3D printing retainers but I was worried they wouldn't thread well. Seems to work fine on yours...
 

HHaase

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Been struggling a bit with the transition section. First attempt printed beautiful, but I used the ID measurement for the OD, so it was too small and too thin walled.
2nd attempt I think the dimensions are right but print separated on me. Then I went on a business trip for a week.
Trying again soon
 

HHaase

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Ok, managed another good print of a transition section, and it's REALLY close to the right dimensions, but not exactly. I was off by about 1.5mm in the ID for the BT-80, I didn't realize there was a coupler slipped in there when I measured the tube.
Good news is the 3" side fits perfectly and the OD for the BT-80 side matches up very nice as well. So just one dimension to fix and the next print should be good to continue building.

I can at least mock it up for you all now to show how it's looking, even if this particular transition is going to become a pen holder or something.

 

AlfaBrewer

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If this is a SPEV, just glue in the coupler and fly what you've already printed.

Or print another transition. Whatever floats your boat.
 

HHaase

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Thought about that actually, but with the coupler then it wouldn't fit. So I was stuck making another.
Good news is I DO have a good one now. Just haven't had time to epoxy it all together yet.
 

HHaase

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Ok, 3D printer has been a pain in the behind, but that's all fixed, and I've had rocket time again.
I'm not going to post another photo with the latest coupler, as it just looks the same as the previous picture.
But it fits, it's epoxied in place, and I can move on to the next step.

Nose Cone!

I need an avionics bay in the nose for my eggfinder, and it mounts on a 29mm sled that I've been using for a while now.
LHS actually had the Mega Mosquito style BT-80 nose cone in-stock for me. So I grabbed one, and promptly cut the back off of it.
I also chopped a section of body tube off the rocket, and using a BT-80 coupler, I made a LONG nose cone assembly.
Throw in a 29mm body tube, more 3D printed centering rings, and another 3D printed motor mount.
Epoxy it all together, with a recovery harness attachment.

Once all this epoxy dries, the motor mount assembly will go into the nose cone. Viola! Nose-Bay!
I'll show the sled in the next post once it's all assembled and ready to go.

I really love using this style avionics bay for my tracker. Keeps it all rock-solid in place, maintains the Cg/Cp relationship, and is super easy to use.
I have uploaded the eggfinder sled to thingiverse today, as well as the BT-80 Coupler to 29mm motor mount centering rings.

 

HHaase

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So, here's the 3D printed sled I use for my eggfinder. Fits into a 29mm motor tube, holds a pair of LiPo's.
Slides into a 29mm motor mount tube, holds it all nice and sturdy, keeps my Cg foward.
Clean and easy to use.

Starting to get into the closing stages of this build, really just needs fins, lugs, and finishing.
Time to start thinking of a color scheme.



 

HHaase

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Wow, been a while since I've worked on this one. Not having a place to fly sure becomes a mental block on building rockets. Now that we've got a field for the local club I'm going to start finishing up my build threads and half-built kits. Not too far from being done here the next step is fins.

I took the lazy route out of this one and ordered some 4" G10 fins from PML. Probably won't be here for a bit due to the holiday, but I have plenty of stuff to keep me busy. I know that's the spendy way to do things but I found some that I like and I don't want to deal with wood right now, so let's get this thing done!
 

HHaase

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Awwwww Yeah! Now we're making progress again. The PML fins arrived today and fit exactly what I wanted. A bit awkward to photo and show the fin/tube profile on the aft end but I'm very happy with how things are progressing.

Except for the Cg. I'm going to have to add some nose weight, that's for sure. I'm thinking a chute baffle will definitely help in that regard, plus give me a solid mounting location for the recovery gear.

-Hans

tubestack-019.JPG
 

bobbyg23

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Can't wait to see this one finished.
 

HHaase

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Same here. I'm pretty nervous about this one though, the Cg is pretty much at the front lip of the transition which is pretty far aft. But the Cp is essentially at the front edge of the tube fins. So the MATH says everything should be perfectly fine, but it's such an oddball and goes against everything I thought I knew about rockets.

Should be a GREAT flight on a 24mm G65 or 29mm H54. Both around 1500-1700ft on slower burn motors. Maybe I should throw some paint on this thing and start working on the baffle/chute mount.
 

HHaase

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Well, that final push is nearly done!

To mount the recovery gear, I decided against a shroud this time around, and instead 3D printed up a chute shelf / anchor for the laundry. In the spirit of the project, I had a 6ft length of heavy elastic that I used. I think it came from my L1 Scion kit? Anyway, I tied the elastic to the shelf and epoxied it about 8-9" down the body tube. Nothing terribly fancy.

Then I cracked open the cabinet of spray paints, and used the colors I had on hand to make up this rather goofy looking scheme. If it survives a couple flights I might add some more detail and make it more aggressive looking. My gut is telling me however that this one is going to have a short lifespan and I think it still looks pretty decent. Should at least be easy to spot flying and in the field.

Only things left to do now are tie on a parachute and add some kind of lug/rail button, and it's ready to fly. I'll probably borrow a chute from something, and I already have rail buttons in the box. So the plan is to fly this on a G65 on August 2nd. I've had this 6 grain 24mm CTI longburn sitting around for too long, so I'll toss in a 29-24 adapter and let 'er go.
 

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HHaase

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Just ran an openrocket sim with the G65 and the measured actual weight of the rocket. This is going to be a great flight. Approximately 1,500ft for apogee, good and stable the whole flight, topping out at 258mph. The extra weight of the tracker in the nose, plus the recovery gear, gives me a great safety margin. Hell, I don't even have to cut the delay charge on the motor at all. Can't wait to hit the go-button.

I've also got a chute on the way. I really wanted to order as few parts as possible for this build but I just didn't have a correct size chute. So I've got a 42" Top Flight X-type on the way. Not sure why but I just really enjoy their X-type chutes.
 
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HHaase

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That G65 proved to be a great motor in the rocket. The 3D printed motor retainers? Not so hot.

I did those retainers on my old printer, which was giving me issues at the time. Both of the 3D printed nuts cracked when I was doing the final prep. More on that later.

The flight itself went great. Recovered nicely and can fly again any time. This is obviously a draggy rocket, so long-burns are a great match. Really a lot more fun than I expected flying this one. I had it in my head that it was a disposable rocket and didn’t care if it crunched. Now I enjoy it and consider it part of the fleet.

What did suck was the motor retainers. After the one holding the motor cracked I grabbed an Estes piece off another kit, but I didn’t realize how little it was threaded onto the rocket, with a last minute 29-to-24mm adapter I made. So the retainer popped off at the pad on launch........ and the motor tube got spit out when the deployment charge went off. So I lost my 6 grain 24mm CTI case. It’s a case I never really knew what to do with, so I’m not toooo upset, but still sucks to lose it on the first use.

I’m also going to swap in a smaller volume chute. I was barely able to get it all packed and get the nose on. I didn’t push the chute shelf down enough when I epoxied it in, so not much room to work with.

Otherwise I think I can declare this build completed! Once I get the 4-29SS finished up I can move on to the next project finally.

C9428341-CE64-4F05-B13A-B02F8D2381A7.jpeg
 

HHaase

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Video from the club! Was a great first flight for the day for us..... even if it took forever to find.

 

bobbyg23

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Video from the club! Was a great first flight for the day for us..... even if it took forever to find.

And I thought that was going to be the easiest recovery of the day.
 

BABAR

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Nice flight, and cool design!

Amazing how even when you think you see “exactly” where a rocket landed how hard it can be to find!
 
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