Modular Model Rocket

by Landru, published

Modular Model Rocket by Landru May 24, 2011

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Modular Model Rocket by Landru is licensed under the GNU - GPL license.

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NEW! as of June 17.

This is now a complete modular rocket system!

Pick a nosecone, body tube(s), fincan, nosecone coupler, and voila! A semi custom printable rocket!

I plan to be adding new sections on a regular basis so check back often! Feel free to leave feedback if there is some feature you'd like to see that isn't up yet :)

Important dimensions to make compatible modules:
Tube Outside Diameter - 1.75in
Tube Inside Diameter - 1.667in
Coupler Tube Outside Diameter (tight): 1.663in
Coupler Tube Outside diameter (looser): 1.659in

NOTE: The designs are closely based on the Legacy design and should work well, but many of them are still untested. I'm working on it, though.


A minimum 4x4x4 build area is required to print all parts individually. I've shortened the fin span very slightly to allow this to be (theoretically) printed on the ABP.

The rocket parts are designed to have .35mm layers and 1.5 width over thickness, so the tubes are exactly two extruded filaments wide. The walls are pretty thin so printing at other settings may produce hollow walls which probably won't work well.

Step 1:
Select Components. You will need a nosecone, body tube, fincan, and nosecone coupler. You can use multiple body tubes to make a longer rocket if desired

Step 2:
Print parts. They printed with the perfect tightness on my printer. You may need to sand some mating surfaces or add tape for the correct fit.

Step 3:
Screw and glue nosecone to coupler.

Tie the nosecone coupler to the fin can through the body tube with 3ft of non-flammable cord. Attach a parachute or streamer if desired (HIGHLY RECOMMENDED)

Step 5:
Insert Motor and add short drywall screw to the rear of the rocket for motor retention. You can also put tape around the rocket motor for a tight friction fit.

Step 6:
Fly safely and have fun!

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Sorry about my ignorance in advance, but how does the parachute system work on this thing?

Comments deleted.

Cooll Any size motor will work, just warp some paper and tape around it to make its diameter bigger

EPIC! Fly's awesome off the end of one of my custom "Air Launchers". Fly's straight and Hasn't broken yet!

Great resource, I wanted to use the 2 nose cone and connector designs to fit an existing Estes Big Bertha kit that uses a BT-60 tube. Scaling the diameter to 95% made it fit almost perfectly. So while it's not totally "standard" sizing it is easily modifiable to fit with standard model rocket components.

what sized engine? a,b,c,d????

I'm guessing C or smaller with a little masking tape (as needed).

I found that a D sized motor fits if you hit it really hard. (Don't) So scale up the fincan part by about 1 or 2 percent.

Hi, did you ever find out what fit ?

And what parachute to use?

I have printed all of the parts needed for the rocket and am waiting to glue them together until I get the shock cord situation figured out. Which brings me to my question:

Where on the fin can am I supposed to tie the shock cord?

I have looked closely and it seems that the only hole that could be used as an anchor point would be one of the holes on the end of the engine mount. This would be fine except that if my shock cord is tied there, I fear that the proximity to the ejection charge of the rocket motor may sever the shock cord after one or perhaps a few launches. As I would like to be able to launch this rocket more than once, I would greatly appreciate it if someone could lend their advice on where to tie the shock cord to the fin can. If the hole on the end if the engine mount really is the only anchor point, I can see no other option than to use a kevlar shock cord, or simply fly without one, which would surely result in the destruction of my rocket. Thanks for the help!

I'm working on printing this now, but I don't quite understand the method of connecting the nose cone and the coupler. Should I glue it? Why not make both parts just one piece?

What I ended up doing was just covering both the flat side of the nose cone, and the nose cone coupler in glue, the I pressed them together and drove a screw through the holes in the center of both parts. I then filled in the seam left between the two pieces with more glue which both streamlined the connection and made said connection that much stronger. Since the glue has dried it has held together rock solid and shows no sign of separating.

actually, both... your have your choice of fincan with 18, 24 or 2x18mm cluster.

Thank you for creating such a great model. It's truly impressive. I had a few questions before I go fly mine.

1: What motor would any of you good folks recommend for it? I printed the 18mm standard fincan with one body segment and the ogive nosecone, using PLA, on a New Matter MOD-T.
2: What size parachute should I use? Or would a streamer be enough?
3: What method do use for attaching the shock cord?
4: If I wanted to print another at a smaller scale for A-type engines, what would be the scale percentage?

Flew great. But the motor was a tight fit and is now welded in :)

This is really awesome!! any build videos out there on this?

I printed one on a DaVinci 1.0. It came out really well, and all I had to do was sand down the nose cone so it would come off easily for parachute deployment. The hole for the engine is kind of big for an Estes C engine, so I would imagine it would be really big for an A-B size. One of the parachute tie downs in the base broke off, so I plan to print another base this weekend. I believe it will launch really well once I figure out how to make the slot for the launch rod bigger. For the 18mm file the hole for the rod is 1/8" if you buy a launch pad. I had to buy the smaller rod so it would fit. I'm anxious to see how well it flies, but it looks really sturdy and feels well balanced. This was my first print over 2 hours and it came out awesome! Nice work Landru! Thanks for the files =)

Could this be scaled up for a 29mm motor?

Thanks so much for posting this great system!

does it actually fly if you wanted to some abd in it

My students built 2 rockets. Both fly great.

Any chance you can export your solid works files to a .step file. I have Autodesk Inventor and that is the only way I would be able to re-size them. I want to re-size your design for 29mm motor. I want to print and build this for my Level 1 Tripoli certification. I could just re-size the STL but the wings are not quite big enough for the size rocket I want to build :-).

It should be possible to build a multi- stage rocket. You need something that will detach from the upper stage when the rocket motor emits the little puff of air that would normally eject the parachute. Also, don't forget about a way to ignite the upper stage...

If you use multi-stage rocket motors this is a lot easier. The mulit-stage engines are designed to ignite the next stage so include a pyro charge at the top instead of a clay cap that is blown out to push the parachute out. The key to multistage though is designing the stages to mate correctly. Even when properly designed I have burned out enough first stages to be wary of plastics. On this design you would need a specifically designed first stage that would mount below the current fin set.

Would it be possible to make a fin base that had the ability to attach another fin base to it so we could set up a multi-stage rocket?

along with that, is it feasible to create a base like the one listed above that can take advantage of 4 rockets such as your x2 base?

  • Thanks for all the hard work by the way..... This is awesome!

I was wondering how you were able to merge the launch lug with the rocket body. In my design, which I made with sketchup, the two pieces look merged, but in the print the places where the cylinders intersect ends up empty. Can you offer any help? Thanks!

maybe export them together in place but not merged. this way it must fully see and use both as 2 instead of merging them as 1. they will still print together just be sure they line up perfectly. im not positive but i think thats what your after. try export as multiple pieces see if that helps.

Impressive rocket design and finished print. I really need a payload section for a light during night flights with my glow in the dark upper sections. I just caught the dimensions shown, I'm sure you used high quality 3d exporting of the model in CAD for the smooth segments I presume about every 5 degrees? I'm very fond of bifurcated nozzles and twin engine configurations. Beautiful job sir! APPRECIATE YOUR HARD WORK and sharing this with us all.

I printed and flew this rocket over the week end and I have to say it is impressive. It balanced perfect with the standard fin can one center piece the cone adapter and the pointed nose cone. I used a d-5 estese engine a piece of elastic some sting and a streamer, no chute. It was to windy for the chute I would never have gotten the rocket back. The streamer and the length of string were enough to slow the rocket down for a safe landing. The rocket went up well over 1000 feet. I think it was closer to 1500 but it went so fast it was hard to tell. Flew it 6 times, got it back every time and then gave it to one of the kids at our field. It was great fun thank you for sharing the rocket and I hope to see maybe some new stiles in the future.

What size motor does it use? It looks like a G, but I got that from the pictures

I used a D sized motor.

I would believe that it uses Sizes A to C motors (18mm) but could be resized to fit anything from 1/2 A through F (Anything above that is considered a Hobby-Grade, not model rocket and is essentially highly illegal to fly without permission)

Actually not illegal, and in fact, most F and G motors can be purchased and flown without certification. Anything over G requires NAR or TRA certification to purchase. Though it isn't law, but rather agreements between the organizations and vendors. Small rockets that fall under the Class 1 definition of the FAA generally can be flown without special permissions or waivers as long as it is done safely and with permission of the land owner. Class 1 rockets are:
(a) Class 1—Model Rocket means an amateur rocket that:
(1) Uses no more than 125 grams (4.4 ounces) of propellant;
(2) Uses a slow-burning propellant;
(3) Is made of paper, wood, or breakable plastic;
(4) Contains no substantial metal parts; and
(5) Weighs no more than 1,500 grams (53 ounces), including the propellant.

I didn't make this for flight, but as a Toy for my son. It was our most anticipated project yet, and since I printed it my 4yo has not been without it.

An awesome project/design.

Thanks Landru - you Rock!


Printed 3 so far. I have used both size fin cans. I have found no need for the drywall screws with either size fin can. The Estes motors I am using barely fit and they stick out a bit. They work fine and stay in place. In fact I have to push pretty hard to get them in there.

I have launched one so far and like someone else mentioned it took a core sample of the Earth. This was in no way due to the model. It was because I put too much wading in the fuselage.

A tip for those that do end up launching these excellent models. The lug on the outside of the fin can and fuselage are only big enough for the smaller Estes type launch pads. If you are using a Porta-Pad E you will need to glue on some straw segments to get it to launch safely.

Rocket 1: Boiler Hornet #1 - 1 24mm Fin Can + 2 Fuselage Segments + Coupler + Conical Nosecone - Not launched yet
Rocket 2: Man #1 - 1 24mm Fin Can + 4 Fuselage Segments + Coupler + Ogive Nosecone - Launched - Destroyed on impact
Rocket 3: Boiler Hornet #2 - 1 24mm Fin Can + 6 Fuselage Segments + Coupler + Ogive Nosecone - Not Launched Yet

Wishlist to expand this model

  1. 29mm Fin Cans -- This way we could use epic 29mm Pro Series II motors
  2. Altimeter Mount -- Actual info about the flight would be amazing
  3. Dual Extrusion Fin Can with the fins separate so we could print them in different colors
  4. Camera Mount -- I think others have attempted this on Thingiverse but not sure if it would work with this model.

Thanks to the creator of this model. I am sure it wasn't easy to make these models and you rock!

Hi Landru, Thanks for posting the files. I printed it on our Stratasys Uprint machine and it came out really well. I've some photo's on our web site here:


No problems with the flight using a 'C' motor, only that the elastic was too short/not secure so the tube ended up doing a 'core sample'. The 3D Printed ABS was very strong with barely a scratch. I've some video I'll post once I've done an edit. The rocket is all fixed with longer, super glued elastic and I'll fly it again once the weather clears.

Landru - could you drop me an email at [email protected]://-alchemy.co.uk-alchemy.co.uk - A major UK museum contacted us regarded a 3d printed item for display. I'd like to use the rocket and would like to ensure you have a credit.

Oh and I printed mine using 1.75mm filament at 0.3mm layers using a Solidoodle 3 and it's pretty hefty. To get rid of that 'zimmerit' body layer, try smearing with Milliput body filler (I use that on my models), then wet sand. As you paint, the paint will fill any remaining gaps. Might be adding a lot of weight this way, but then that's your excuse to use larger motors!

I am going to fly this rocket at NASA Goddard on 6/2/13 when they do the monthly NARAMS launch. Look for the purple beast if you are there!. Here are my notes:

1) I had the same problem as everyone else....fins that peel up. I trimmed them with an emery board to be angled post build, but next time, I will be putting down a 'raft' on my printer to prevent that.

2) I also tacked on the body and nose of a 'Baby Bertha' as well as a baffle in the middle. The rocket is super beefy now.

3) It would be nice to have an engine retainer ring in there that can be screwed into the 2 holes at the bottom. The NASA folks are not fond of friction fit engines.

4) It would be nice to have the find on a slot, so that we can have interchangeable fins, AND, print the fins flat. A nice addition is a version that allows any engine mount to be added (e.g. cluster) or the ability to connect the fin cans together to create stages or multi-fin designs

I flew this rocket at NASA with two body tubes and an Aertotech E15-7W motor. It flew straight as an arrow going up, but shattered on the return (an unfair stress test as the parachute did not inflate). I just posted the build notes and post-mortem and open questions: http://www.flickr.com/photos/jurvetson/8564855081http://www.flickr.com/photos/j...

Has anyone lathered epoxy over the Makerbot PLA material? Anyone experiment with fins that angle up off the build plate? Anyone design a fin can for a cluster of three motors already? Thanks!

I have had success with coating abs with epoxy but im not sure about pla. Also not sure about the fins angling off the plate but my guess would be you could make slots for the fins that snap together that way you could print much bigger fins in much different dimensions. Also rocksim allows you to export 3D models as stl files for printing but it doesn't do fillits for you so you would have to work with it in solidworks a little bit.

This is going to be my first print when I get my printer

So, I don't know what it is about this model, but I've been trying to get it for a year, finally have a full model http://www.flickr.com/photos/hslphotosync/7490189206/in/photostream/http://www.flickr.com/photos/h... :-D

I've never made a rocket that wasn't from a kit before and I'm kind of confused about where the drywall screw goes. Does it/they go in the two holes in the bottom? So the head of the screw overlaps the bottom of the engine? Wouldn't you have to unscrew it every time you had to put in a new motor?

Yes, the screw goes into the small hole(s) at the bottom, and has to be unscrewed to remove the motor.

There are different files for different size tubes (18 or 24mm)

Nice job! The 18mm version is missing the guts to hold the motor. I printed the 24mm version and noticed the D won't fit. I'll need to sand it out a bit. What size diameter did you make the inner tube for the motor? 24mm?


Fixed the faulty 18mm rocket.

The ID is 24.1mm. The paper estes motors have a tendency to swell in high humidity, so either they might be a bit larger than usual, or your printer might be a bit out of calibration.

I am using skeinforge 41 and the fins always are hollow for me no matter what settings I use. I also calibrated my printer (again) to try and get the D motor to fit. I increased the x and y steps and printed several calibration objects and sizing is correct with a micrometer. However the hole for the D motor is still too tight and will not go in more than a cm or two. I am printing with 0.35mm layer height and 1.5 pwot/iwot. I might just import the stl into openscad and make the motor hole larger. I would rather have a larger motor hole and have to use some masking tape on the motor to make it snug.

Wow, that's really strange. My fin infill always seems fairly decent. Looks like your prints are otherwise very good quality, too. Are you doing linear infill and no extra shells?

If you want, I can upload a version with thicker fins and a bigger motor mount. The Solidworks files are really flexible so it'll only take a few minutes. How much bigger/thicker do you think the fins and motor mount need to be?

Where did you fly it from? That looks like an NAR/Tripoli club.

I think it was a Tripoli club. We were launching in California, about an hour West of Visalia. A coworker goes every month and it was my first time.

It is Tripoli Central California.

Please please share your source files. I wanna make a helicopter nose cone and twisty fins...

I've got a whole set of new parts coming out tonight or tomorrow. I'll post the solidworks 2010 files for all the new stuff. I already have a twisted fin-fincan, too ;)

I am also posting info like the diameters needed for loose and tight fits so others can easily make mating parts. I

could one print a lot of bodys and make a really tall rocket?

Certainly, though you may need to add a launch lug towards the front of a long rocket.

Am printing this now and it's coming out great - but I'm unsure which motor I need to order for it. I see there are several model D type motors from Estes, does it matter which one I get?

I used a D12-5

Probably any of the D12-3,5,7 will work.

The rocket is pretty light so it can take the abuse of a mis-timed ejection charge.

LOVE this rocket! But... I'm trying to print on my ToM with ABP - The short body prints fine, as do the nose cone, coupler and adapter. The fin can is giving me fits, though! WIth the mounting bolts on the edges of the ABP, and clearance for the extruder head cone to get over the bolt heads, I have 98mm of x-axis travel available. No mater how I've tried to reorient the fins, the head keeps crashing into one of the corner bolts while drawing the initial box around the base of the part (which has x ranging from -61.86 to 55.07 in the GCode in my last try, a range of 116.93 mm). Is there a secret others have used to print on a ToM with ABP that I'm missing? Is there a way to get a slightly smaller fin without also shrinking the engine mount? Thanks!

vollumc, I had the exact same problem. I actually got it to print on my TOM without hitting bolts by printing raftless, but then the fins warped, even with the heated ABP. If you find a solution, please post it! In the meantime, I may simply scale it to fit A/B/C motors without the adapter. Just need to find the accurate OD of the motors, so I can find the scaling factor

According to http://www.apogeerockets.com/estes_items.asphttp://www.apogeerockets.com/e... the outside daim of the D engines is 24mm, and the A, B, and C motors are 18mm. Great idea to scale the whole thing down! I'm going to give that a try!

Landru and davidatdavincisciencecenter - I tried a partial build of the fincan scaled to 75% (18/24) and checked it against an A engine. It looks perfect, so I'm restarting the build without the raft, as that doesn't really look necessary. I'll let you know how it works out!

The 75% size fincan printed fine, but the shrinking leaves the guide tube pretty small for my coat hanger launch rod... I think I can bore it out (or replace with a glued on straw) but it's something to consider for the next generation design!

Starting on a 75% body tube now.

Oops - another shoe just dropped! The A, B, and C engines are the same length as the Ds (70mm) so now the fincan is too short to hold the whole engine inside... without a redesign, it looks like my options are to let it stick out and find an alternative means of securing the bottom, or remove the "stops" at the top of the engine tube and add a stop plate or stop rod near the top of the fincan; in the latter case, it will have not interfere with the attachment of the body tube... I'll look at this when the body tube finishes. So there's another thing to add to the redesign.

The fins had 2-3mm of warp on my printer, too. Must be due to the high Z of the fins relative to their width.

How much clearance do you need to print this without hitting the bolts? I'm doing a re-design and I will keep that in mind.

Landru - The useable build area is about 98 mm square. Keeping it to 90-95 mm should work fine even with a raft. Whatever you design, I'll try out!

Can you turn off the skirt or reduce the outline?

I don't see any option for that in ReplicatorG, but I tried to comment out those lines in the GCode; that didn't seem to help, but possibly if I did a bit more hand editing I could get something that would work. I'll have to read the code carefully and see where it's getting into trouble. One thought was to print it upside down - that would avoid hitting the corner bolt heads, but would be pretty wobbly and would need support structure, or possibly it's side, also not an appealing option...

nice surface quality !

This is very nice. Printed great on my Mendel.

Here are some pictures of it printing and the final product. :-D

How come the attached picture shows the body and fincan with the same height and in the stl files the fin can is 101.6 mm tall and the fincan is 127.0 mm tall (or impossible to print in a TOM with ABP)?

Sorry, the body is 127 mm tall.

I think you are somewhat correct. I had to cancel the print a tad before it finished on the body.

What is the max height you can print, and i'll see if I can upload a shorter section.

I went ahead and edited the body stl file to fit under the 104.5mm maximum Z height I have on my TOM. It looks really nice. I am having some trouble connecting the nose assembly to the body but some sanding will sort it out. Now I just need to find some rocket engines :)

It would be great though if you can post a shorter body ( or two pieces ) for those that are height challenged.

Could you post your own variation? I'd love to print this one on my TOM.

Just uploaded a short body which is 4in tall. Everybody should be able to print it now, hopefully.

now terrorist are going to start buying.makerbots

Nice job - but the precedent was really set by the Zcorp engineers. Check out our website blogs!

"That rocket looks pretty good on your 1000$ printer, but it's so much nicer on our 40000$ printer?" Seriously? :-P

Perhaps you should share the files then?

You're right, I checked out the Zcorp web site, but I couldn't find a single build file. Very disappointing.

I like your design, you went straight for the 24mm engines (me gusta). Well done.

I can't wait to see some video. :-)

Wow ... you just set a new standard for printable rocketry! Thanks for sharing ...

Yeah this is a cool design. Although the "standard" was set earlier ;) (it was done some time ago by the folks at DesktopFab: http://www.desktopfab.com/projects/eos.phphttp://www.desktopfab.com/proj...

Either way both are cool designs.

By the way what did you print this on?

There are no stl files there... :'(

I wish the desktop fab one was printed in 1 piece for the fins.

I Printed this on a t-slot repstrap with 1.75mm feedstock on a bowden cable, with mechanics similar to the ultimaker. I'll be posting plans for that too if I ever clean up the design.

This looks awesome. Can't wait to print.