Inspired by the Comanche 3

[banjonate]

Over on the Facebook groups Estes Model Rockets and Born Again Rocketeers, I had showed off a completely scratch-built, poster board rocket using no off-the-shelf "rocket parts." It was inspired by my desire to do a feasibility study of a 29mm-diameter Comanche 3, in turn inspired by a thread I found on a sub-forum elsewhere on this site dealing with folks' musings about a hypothetical "Comanche 3E".

I built the first rocket which I will attach to this initial post. The following posts will be a photo-documented, step-by-step of my recreated build using the same materials and techniques, along with a minor change due to results of the first flight (which was successful; no recovery due to a higher flight than I anticipated, therefore a smaller field than required, and the trees ate it).

The intention is to be able to create a 20% upscale C3 that will be able to fly on D and E powered boosters. This is the sustainer rocket that is currently built as D12 powered. I have flown the model before, but I have not simmed it to see what would happen with additional stages, although that is the intention.

 

[banjonate]

This is, in my opinion, very similar to the purpose of the real-life sounding rocket programs that the United States, Canada, and other countries have done: get a specific job done as economically as possible and use experience to guide you.

The following materials were used:

-A pack of 5 11"x14" (yes, I am American so I use inches; live with it) pieces of posterboard. The posterboard that I used was 11pt C2S. Cost was $2.09. (Part of the reason this project was done was because I didn't feel I could justify buying an odd-size body tube, along with a nose cone, and pay for shipping along with it. I could, however, justify $2.09.)

-a 1" x 1" x 6" piece of balsa
-a 3/32" x 4" x 4" piece of balsa
-a cardboard Reynold's Wrap tube to use as a mandrel among other things
-6 feet of Paracord
-strips of plastic bag to be obtained from anywhere; or other streamer material
-white glue and some form of epoxy or other thick adhesive

 

[banjonate]

Take three 11x14 sheets of board to be used. Cut three inches off two of the boards, making a total of one 11x14 and two 11x11 sheets. The two left over 3x11 sheets will be used for fins and, if you care to, lugs.

The first step is rolling the body tubes. I will not bore you with the details, as Tim van Milligan and James Yawn both have good techniques for rolling tubes. I believe my method splits the difference between Tim's just-tough-enough-to-be-usable and James's built-like-a-brick-outhouse methods. They are both better than mine; I was learning this as I went.

If you use heavier, thicker board (I have in another build used 18pt C2S), they come out smoother. My method does have some imperfections to it, but it's approximately good enoough.

Using some cylinder smaller than the mandrel tube you will be using, roll and unroll the three sheets used for body tubes (roll the odd 14x11 sheet so that the tube will be 14" long; i.e. you will have two 11" tubes and one 14" tube). Next, take the Reynold's Wrap tube and roll one of the sheets ONE TIME around the tube. Holding in this position, spread the glue over the rest of the tube (I found it actually works better if you lay the glue down either perpendicular to the tube, or diluting the glue slightly and spreading it with a brush). Roll the tube completely, making sure that the edge of the tube stays down. It will not take more than a few minutes before the glue has bonded enough to where the tube will stay rolled of its own accord. Pull the tube out and repeat with the other two sheets.

 

[banjonate]

Use the 3x11 sheets we cut earlier for fins. I cut them ~2 body widths on the root edge, 2-1/2 body widths wide, and a 1 body width short edge, as shown.

Cut 6 fins, and glue them together in a 2-ply, for a final count of three fins. Put a heavy book over the top of them to keep them flat as the glue sets.

2 Notes:
- For the first one I did, you will notice that the lower inside corner is cut out, like the original Comanche 3 fin design. I modified to NOT do this the second time, as on the first flight one of the fins came off a couple hundred feet into the flight; however, the rocket was stable enough that this did not affect the rest of the flight adversely. I figured a little extra attachment area wouldn't hurt any.
- Your mileage may vary for how well this technique works. The first time, it went great. This time, the fins wanted to bend on me, so I was constantly trying to keep them straight. I have built rockets (using traditional parts) with 18 pt C2S board fins as a single ply and they are great. I have even used, for B-and-under powered flights, this lighter posterboard as a single ply for fins and have flown many of them multiple times.

 

[banjonate]

For the engine mount, you have two choices:

1) wrap a notecard or some left over board around a 24mm engine and create centering rings appropriately (in this case, strips of board wrapped around and glued to the motor tube in two places until it fits in the main tube), or
2) a Reynold's Wrap cardboard tube, like I am using, will PERFECTLY fit a BT-50 tube, so simply cut a couple of rings from the tube you used to roll the poster board, glue to the outside, and it will glue directly into your body tube.

I like to use an extra strip of paper at the top of the motor tube I just created to act as an engine block; if you are going to use composite motors with retention rings built in, not necessary.

NOTE: THIS ROCKET IS BUILT TO BE STABLE USING AN ESTES D12 MOTOR. BY EXTENSION, AN AEROTECH E SHOULD WORK FINE. HOWEVER, MAKE SURE YOU ADJUST CG WITH WEIGHT IN THE FRONT OF THE ROCKET IF YOU GO OFF-PROGRAM.

 

[banjonate]

Cut a couple of 2" pieces off of the RW tube we used to roll the body tubes. Use them as tube couplers and glue the body tubes together. I used strips of a different color poster to wrap around the joint for a little better aesthetics, and because, due to the nature of the beast, the tubes will not be EXACT fits to each other.

 

[banjonate]

For the nose cone: Glue the balsa that is in the materials list this way:


Shape using whatever technique you are comfortable with; in this case, I hand-sanded using 60, 150, and 400 grit.

Once you are done with the shape, cut another 1" to 1-1/2" piece off the RW tube and glue to the bottom of the nose cone, to insert into the body tube.

 

[banjonate]

I mount the shock cord the old way: using the corn-in-envelope method, because, as a BAR from 25+ years ago, it's really all I know!

Cut to size, insert into body tube as far as you can practically get it:


Use some sort of epoxy or Liquid Nails to place the other end (about 4" or so) in the nose cone. This has the effect of adding nose weight, if needed (and I believe it probably is):

 

[banjonate]

At this point, effectively I am done. I haven't yet loaded the streamer or parachute (whatever you may want to use) or wadding, but I am going to check the CG vs. CP, knowing that any additional weight added at flight time will increase my stability margin.

I do not have any type of software at the moment, so I calculate the CP the old-fashioned (simple and conservative) way: using the 2D cross-section of the rocket, finding the point at which the area below and above are the same.

I find the CG by, well, balancing it (with engine loaded) on my finger.

The below picture shows the margin of almost exactly one caliber:

 

[banjonate]

I hope that you have enjoyed the above walk-through (and that I posted in the correct sub-forum). I haven't flown this second model yet, but the first model flew great. I will post results of this flight, which hopefully will be some time soon.

Comment below with any improvements, encouragements, disparagements, whatever. I am new at this, and always looking to improve.

Safe flying, and God bless!

Banjo Nate

 

[JohnCoker]

Nice working making your own tubes and nose; they came out great!

 

[mbeels]

Yeah, great job, that is truly a scratch built rocket!

 

[banjonate]

Thank you both, appreciate it.

One purpose I had in posting this was to show that, with very little money, the right materials, and some pretty rudimentary labor, one can build a good-sized rocket that will fly impressively and safely, UNLIKE many of the videos I have seen on YouTube that show questionable and dangerous techniques.

come to think of it, maybe this should have gone in the Scratch Built sub forum.

 

[dhbarr]

Pfft, didn't even make your own paper, let alone grow the trees or create the soil.

No seriously though, that's fantastic!

 

[GlenP]

Very cool poster board rocket, I sometimes raid the recycle bin for paper towel tubes or wrapping paper tubes to make rockets for LPR. What are the specs of this rocket: diameter, length, empty weight, engines, and estimated altitude?

With cardstock sheets that can be printed on a ink jet or laser printer, the paper has a grain direction. It prefers to curl along the long paper edge. If you roll it the other way it may crease. To avoid that it may help to steam the paper slightly, or just breathe on it. With a larger poster board, that would take a big breath! I am not sure if the poster board has multi plies with grain in different directions so that it will pretty much crease if you roll it too tightly in any direction. Some light steaming might help with that, not sure, I have not tried making body tubes from the heavier poster board paper. Seems like a double layer of that will be plenty strong for a MPR, I was just wondering how the weight compares with the Estes heavy wall PSII body tubes. Do you come out lighter or heavier than an Estes Mammoth, for example? Not sure if that is an appropriate size comparison, but is there a similar kit in that diameter and length with the PSII tubes you can compare with? Maybe the Star Orbiter?

 

[mbeels]

Pfft, didn't even make your own paper, let alone grow the trees or create the soil.

No seriously though, that's fantastic!

Reminds me of a quote from Carl Sagan. If you wish to make an apple pie from scratch, you must first create the universe. (or something like that).

 

[GlenP]

Those 2-ply surface mounted fins might barely survive a single-stage flight on a D, have you launched it on an E yet? What engine did you use when you lost a fin?

When you multi-stage it with an E to either a D or E, the sustainer fins might not survive after the initial kick from the booster. Speeds will be much higher. You might consider TTW fins and using more plies when you stage this one.

 

[banjonate]

Very cool poster board rocket, I sometimes raid the recycle bin for paper towel tubes or wrapping paper tubes to make rockets for LPR. What are the specs of this rocket: diameter, length, empty weight, engines, and estimated altitude?

With cardstock sheets that can be printed on a ink jet or laser printer, the paper has a grain direction. It prefers to curl along the long paper edge. If you roll it the other way it may crease. To avoid that it may help to steam the paper slightly, or just breathe on it. With a larger poster board, that would take a big breath! I am not sure if the poster board has multi plies with grain in different directions so that it will pretty much crease if you roll it too tightly in any direction. Some light steaming might help with that, not sure, I have not tried making body tubes from the heavier poster board paper. Seems like a double layer of that will be plenty strong for a MPR, I was just wondering how the weight compares with the Estes heavy wall PSII body tubes. Do you come out lighter or heavier than an Estes Mammoth, for example? Not sure if that is an appropriate size comparison, but is there a similar kit in that diameter and length with the PSII tubes you can compare with? Maybe the Star Orbiter?

The length is 42”: 36” of tube and 6” of cone. is approximately 29mm. The first one was fully 29mm inside diameter, this one didn’t quite get there.
As far as weight, the paper (almost all of which is used) weighs 75 grams. Add glue, motor mount, and the couplers in there you are talking probably 85 grams. About 15 grams for the nose cone (density of balsa), paracord and other accessories in the recovery end add a nonzero amount, and a D12 puts the CP close enough to the middle, I am estimating 115g unloaded.

The tubes are tough. Almost like plastic.

Thrustcurve.org simulates it to the 900 foot range on a D12-5, and from the first one I flew that is pretty accurate. No altimeter, just eyeballing it.

I do think a good modification would be real balsa fins as far as sturdiness. I would like to try single ply fins with thicker board first. I have had good luck with that on smaller stuff.
I would imagine you could go up to F on this thing with very little modification. Also, the CP I calculated is very conservative and needs to be calculated accurately before doing much playing.

 

[banjonate]

Those 2-ply surface mounted fins might barely survive a single-stage flight on a D, have you launched it on an E yet? What engine did you use when you lost a fin?

When you multi-stage it with an E to either a D or E, the sustainer fins might not survive after the initial kick from the booster. Speeds will be much higher. You might consider TTW fins and using more plies when you stage this one.

Very much so.

 

[banjonate]

So, I went to the dark side and downloaded Open Rocket.
As it turns out, the sustainer detailed above has something like 10 calibers of stability (CP is just a little forward of the fins). Which brings up a couple questions:

1). Negating the fact that I do have to do something with the fins structurally if I want this to fly as a multi-stage (and on anything more than a D), Adding a booster with an E12 and no fins still has a pretty large stability margin. I am seriously thinking about a smaller fin span.
2). I haven’t played too much with it, but I am guessing that body tubes that weigh more than cardboard ones add significant margin by distributing mass better.

 

[GlenP]

So you may have sufficient stability margin to just throw a motor on there as a booster, i.e. CHAD CHeap and Dirty style staging. If you have a retainer on there, not sure how easy it would be to tape the motor on. Usually just with some cellophane that will melt during staging and allow the spent booster engine to fall off. This works best when the motors can be essentially touching each other and the cellophane tape wraps them to each other. Not sure if you have enough margin for more than one stage like that. But, too-thin and too-large fins that help contribute to that margin won't be very effective should they rip off halfway through the boost.

 

[banjonate]

So you may have sufficient stability margin to just throw a motor on there as a booster, i.e. CHAD CHeap and Dirty style staging. If you have a retainer on there, not sure how easy it would be to tape the motor on. Usually just with some cellophane that will melt during staging and allow the spent booster engine to fall off. This works best when the motors can be essentially touching each other and the cellophane tape wraps them to each other. Not sure if you have enough margin for more than one stage like that. But, too-thin and too-large fins that help contribute to that margin won't be very effective should they rip off halfway through the boost.

Going to trim the fins on the existing sustainer and test on a D before I do anything else. On OR, I have built out 3 stages with trimmed fins, and fully loaded EEE or EED needs a longer rod to get off the pad fast enough.
I don’t like the idea of CHAD or finless staging just because spent engines raining down like large hail doesn’t sound like a fun day at the office.

 

[GlenP]

Going to trim the fins on the existing sustainer and test on a D before I do anything else. On OR, I have built out 3 stages with trimmed fins, and fully loaded EEE or EED needs a longer rod to get off the pad fast enough.
I don’t like the idea of CHAD or finless staging just because spent engines raining down like large hail doesn’t sound like a fun day at the office.

Good point, some clubs might not even allow dropping engine casings. You can always use an engine adapter for the sustainer like a 18mm in a 24mm mount, or a 24mm engine in a 29mm mount, maybe to get the fully loaded stack weight down, and rod speed fast enough, look at E to D to C staging?

 

[banjonate]

Good point, some clubs might not even allow dropping engine casings. You can always use an engine adapter for the sustainer like a 18mm in a 24mm mount, or a 24mm engine in a 29mm mount, maybe to get the fully loaded stack weight down, and rod speed fast enough, look at E to D to C staging?

I am trying to match the original C3 3-stage height of 1/2 mile. Can simulate this bugger to that on a single composite; 3 BP stages is getting difficult. Especially since I realized here at work that I was using weight assumptions for 10pt coated paper instead of the 11pt that I actually used...

 

[banjonate]

So, coming back to this after a few months.....

Haven't flown yet. BUT... have trimmed the fins based on the simulation file back to 1 diameter. Using the current configuration (tubes that are rolled 3x), multiple stages don't need to have fins that are any bigger than this. I have built another stage for flying after the first single-stage test flight, but the next build will be with tubes rolled only 2x for some mass reduction and with balsa fins. Yes, I seem committed to doing this without commercially available tubes, although eventually I am going to do that (which will I guess have to be posted for discussion at the Scratch Built forum as opposed to this Cardstock forum, which I am probably pushing the limits of anyway.

Anyway, here we are with trimmed fins:

 

[BABAR]

Carl Sagan is quoted as saying,

“if you wish to make an apple pie from scratch, you must first invent the universe.”

That said, this is a really cool build!

 

[banjonate]

Carl Sagan is quoted as saying,

“if you wish to make an apple pie from scratch, you must first invent the universe.”

That said, this is a really cool build!

Someone mentioned that earlier in the the thread (which was something like 3 months ago at this point).

 

[BABAR]

Someone mentioned that earlier in the the thread (which was something like 3 months ago at this point).

@dhbarr

Great minds think alike.

 

[Ronz Rocketz]

Over on the Facebook groups Estes Model Rockets and Born Again Rocketeers, I had showed off a completely scratch-built, poster board rocket using no off-the-shelf "rocket parts." It was inspired by my desire to do a feasibility study of a 29mm-diameter Comanche 3, in turn inspired by a thread I found on a sub-forum elsewhere on this site dealing with folks' musings about a hypothetical "Comanche 3E".

I built the first rocket which I will attach to this initial post. The following posts will be a photo-documented, step-by-step of my recreated build using the same materials and techniques, along with a minor change due to results of the first flight (which was successful; no recovery due to a higher flight than I anticipated, therefore a smaller field than required, and the trees ate it).

The intention is to be able to create a 20% upscale C3 that will be able to fly on D and E powered boosters. This is the sustainer rocket that is currently built as D12 powered. I have flown the model before, but I have not simmed it to see what would happen with additional stages, although that is the intention.

View attachment 429625

That's quite the electrical hazard on the back wall.

 

[banjonate]

That's quite the electrical hazard on the back wall.

Was wondering if someone would notice that...