Estes DOM Moonik-I

[JAL3]

Has anyone ever built this one?

Does anyone have any advice on how best to miter the tubes?

View attachment Moonik-I.pdf

 

[Blades]

John,
do you have the Template Widget program by Matt Stum? If not, you can find it at https://www.rocketreviews.com/tool_template_widget.shtml. It's a handy little program and can produce miter templates for you. All you need to know is the tube size and the angle of the miter cut. I use the program all the time.

 

[JAL3]

John,
do you have the Template Widget program by Matt Stum? If not, you can find it at https://www.rocketreviews.com/tool_template_widget.shtml. It's a handy little program and can produce miter templates for you. All you need to know is the tube size and the angle of the miter cut. I use the program all the time.

That looks very promising.

Thank you.

JAL

 

[MarkII]

I started one a few years ago. The various miter template generators would work of the joint in question was a corner joint, but it isn't. The design requires you to join one tube to another at an angle, midway along the second tube's length. (IOW, make a branching tube.) A simple miter would be fine if the side of the "trunk" tube was flat, but since it is round the problem is much more difficult. And oh, did I mention that you must connect the two tubes after they have been embedded into a styrofoam ball? And that the joint must be tight and leak-proof to keep ejection charge gasses from melting the styrofoam?

After going through a bunch of BT-20 I managed to hack something together that looked like it would more or less work, but I got hung up on the rest of the build. The material that was specified for the legs/antennae (thin balsa sticks) is much too flimsy and flexible to even hold up the empty ball. I was going to use basswood strips, but then I got hung up on trying to accurately draw an equatorial line on the ball so that I could mount them all evenly around it, and then I also was faced with the issue of getting them solidly attached as tangents to the ball (as opposed to simply embedding them into it). These are significant challenges and I have no idea how the designer was able to pull them all off. My build is still "in process" even though I haven't touched it in the past 4 years.

 

[JAL3]

I started one a few years ago. The various miter template generators would work of the joint in question was a corner joint, but it isn't. The design requires you to join one tube to another at an angle, midway along the second tube's length. (IOW, make a branching tube.) A simple miter would be fine if the side of the "trunk" tube was flat, but since it is round the problem is much more difficult. And oh, did I mention that you must connect the two tubes after they have been embedded into a styrofoam ball? And that the joint must be tight and leak-proof to keep ejection charge gasses from melting the styrofoam?

After going through a bunch of BT-20 I managed to hack something together that looked like it would more or less work, but I got hung up on the rest of the build. The material that was specified for the legs/antennae (thin balsa sticks) is much too flimsy and flexible to even hold up the empty ball. I was going to use basswood strips, but then I got hung up on trying to accurately draw an equatorial line on the ball so that I could mount them all evenly around it, and then I also was faced with the issue of getting them solidly attached as tangents to the ball (as opposed to simply embedding them into it). These are significant challenges and I have no idea how the designer was able to pull them all off. My build is still "in process" even though I haven't touched it in the past 4 years.

I appreciate the "encouraging words", especially since I got all the materials together today. I even found some BT30 laying around that was ordered for a project that fell by the wayside.

I though the tubes were mitered at their ends. It looks that way to me but its hard to tell. To me, the hard part will be drilling the shafts to meet.

For the fins, I bought some freezer paper to give your method a try. I also picked up the stiffest sheet of balsa I could find. Together, I hope it proves to be enough.

I have thought about the tangency issue as well and don't yet have a solution. I was figuring to probably eyeball the thing.

I am planning on trying FnF on the styrofoam ball to give it a smooth finish. I then have some ideas about using brass and nickle paints.

I thought I might try a trifold for the shock cord instead of the paper strip the plan shows on the outside of the ball.

 

[MarkII]

I though the tubes were mitered at their ends. It looks that way to me but its hard to tell. To me, the hard part will be drilling the shafts to meet.

Study the drawing carefully and you will see. The instruction have you put a hardwood plug in up at the top of the motor tube to prevent the ejection charge from burning through the tube. This is a problem with any design that requires the ejection charge to make a turn before exiting the rocket. Whatever surface the ejection charge hits first before making the turn catches an awful lot of fire and burning debris, so it needs to be able to withstand a lot of punishment. And remember that there is only styrofoam beyond it. So because of the plug, the branching has to be below it along the shaft of the motor tube. You can also use the plug as an anchoring point for your Kevlar, by the way.

Oh, yeah, thanks for reminding me. Boring the two channels where the tubes will meet is a bear, too. Don't start on the tube joint until after you have dome this, because you won't know where along the main tube the branching tube will hit until after you have bored the two holes. I inserted the motor tube into its bore hole and then inserted a fine point Sharpie into the hole for the branching tube. I used the Sharpie to mark the point on the motor tube where the other tube would hit it.

Once you get the joint figured out, you will have to insert the motor tube into its bore hole and make sure that the joint face is lined up with the other bore hole. Then you will have to insert the branching tube into its hole and bond that joint together, even though you can't see it because it is buried in the middle of the styrofoam ball! And that joint has to be absolutely leak-proof, too, to prevent hot ejection gases from melting the foam. It won't be easy but it can be done (I think).

All I can say is that the kid who designed this must have been an apprentice plumber or steam-fitter, or else he had significant help from a professional in one of those trades. Yowsa!

 

[MarkII]

I really don't want to turn this into MY build thread (because it may never get finished), but I did want to show you a few pictures.

Here's what I have done so far.

To make the branching joint, you need to make an oval-shaped hole in the motor tube...

...and a double miter on the branching tube.

 

[MarkII]

This shows where I marked the ball of for the antennae/legs. Wherever the lines cross is where an attachment will be make. There will be four of them. One of the "poles" is centered on the opening for the motor tube and the other is 180° opposite it. It took me an entire evening to get these meridians lined up and marked off.

 

[mikeyd]

Just a thought, but why not just take the tube all the way through, and put a nose block at the top? have it blow the Chute, out the top, this would make it land on the "fins", but you would not have to make the unique BT splice.

 

[JAL3]

Just a thought, but why not just take the tube all the way through, and put a nose block at the top? have it blow the Chute, out the top, this would make it land on the "fins", but you would not have to make the unique BT splice.

That would be the easier way and there are plans for plenty of variations on Sputniks around that do just that, if they used ejection at all. Part of why I chose this particular plan, though, is because of the side ejection.

"We choose to go the the moon not because it is easy, but because it is hard."

 

[MarkII]

Probably the most common recovery technique for larger (too large for featherlight recovery) Sputnik-style oddrocs is rear ejection. The Moonik uses the more-complicated "ported ejection." I was attracted to the design for the same reason that John was; it's an interesting approach.

I'm sure that there's a formula for calculating the bevels that need to be cut for the branching tube, but I derived it with a little bit of applied logic and a whole lot of trial and error. I can explain it visually with diagrams in a heartbeat with a drafting board, T-square, protractor and a pencil, but doing it with software is much more of a PITA. Let's see if I can draw a picture with words.

Imagine that you have a vertical pipe, and want to merge another one of the same diameter with it at right angles midway along its length. You don't have a T-coupler, so you have to do it the hard way. You can simply butt the second pipe up against the first one, but it only contacts it in two places, leaving gaps everywhere else. you need to be able to push the second pipe into the side of the first one.

For reasons that would be obvious if I could draw it, you want to be able to push the end of pipe B into the side of pipe A until it is halfway through it. Remember that the two pipes are the same diameter. Now once you have done that, you want to trim off the portion of pipe B that is actually inside of pipe A, leaving only the edges where the two pipes touch. After you have done that, you pull pipe B back out. What does the end look like? It has two half-circles cut out of the end at 180° to each other. (We are just going to focus on the changes to pipe B.) If you looked at the cuts in profile, you would see that the pipe actually has a symmetrical double-bevel on that end.

Now go back and imagine that after you push pipe B halfway into the side of pipe A, you twist it down so that it is no longer perpendicular. Then if you trimmed off the part of B that was inside of A, the end of B would still have two opposing bevels on it, but they unlike the first example, they would not be the same size. The upper bevel would be shallower than a perfect semicircle, and the lower one would be elliptical in shape. In fact, the upper bevel decreased by exactly the same amount that the lower one steepened. Their bevel angle would no longer be equal, but the sum of both of them would still be equal to the sum of their angles when B was perpendicular to A, which was 180° (90° + 90°).

So if, say, you angle B down so that it meets A at an (inside) angle of 60°, then the lower (acute angle) side of B is 60° to A and the upper (oblique angle) side is 120° to A. That is because not as much of the upper side is inside of A as it was in the first example, and more of the lower side is in it.

Next post - how to cut the bevels.

 

[JAL3]

Mark, I'm wondering if we're working from the same version of the plan. The one I have shows a thrust ring but no plug at the top of the motor tube. Instead, the top of the tube is cut at a 45. The side tube is also cut at a 45 and the two are joined together that way.

 

[MarkII]

We cut the bevels after we trace them out using an online or downloaded template generator. (This being the 21st century and all...) Template generators are programmed to show you where to cut a tube if you want to make a single bevel. In the terminology of our example, you would be cutting a bevel that starts on the lower side of B and extends right up through the upper side of it. But that's not what you need. Actually, it is almost what you need, but not quite, plus you need something else.

Instead of cutting the first bevel so that it goes all the way through from the lower side to the upper side (when looking at the pipe in profile), you want to cut a bevel that will only angle half of B's diameter. Then you want to cut a bevel 180° from the first one that will angle the other half of the pipe's diameter. The two bevels won't be equal, but where they meet in the middle, the angle between the two of them will be 90°. Got that picture?

So you need to program the template generator to allow you to trace a cut line for a bevel on one side of the tube, and then another template to trace a different bevel on the other side, and have the angle where those two bevels cross each other be 90°.

 

[MarkII]

The way that I create a two-sided or double bevel is to first mark the tube as if I wanted to put two fins on it exactly opposite each other. Use whatever technique you prefer to mark the tube for two opposing fins, and extend the fin lines for the length of the tube.

Then I use my template generator to make a wrap-around miter template. I place that around the tube so that the two sides of the wrap-around meet right at one of my two fin lines, and the peak of the template is even with the end of the tube. I use it to draw my first cut line.

Then I generate a wrap-around template for the other bevel, and place it on the tube so that the two sides of the wrap meet at the other fin line, and the peak is at the very end of the tube. Then I trace my other cut line.

The two cut line cross each other at two places on the tube that are 90° away from the two cut lines and 180° from each other. When the two bevels are cut, there will be two "points" on the end of the tube that are opposite each other.

 

[MarkII]

Ideally, the hole that would be cut in pipe A would be a negative outline of the double bevel in pipe B, so that all of the cut edges would simply weld together when the two pipes were joined. But for the Moonik I cut a simple oval into the side of the motor tube ("pipe A") that was smaller in diameter than the recovery tube ("pipe B"). Since I would not be able to bond the two tubes together until they were both inside the styrofoam ball, I wanted the beveled edges of the recovery tube to be able to grab onto and bond to the solid outer wall of the motor tube. When I push the recovery tube in, I want the glue-covered edges of the double bevel to contact the motor tube along their entire length. I was hoping that this would be enough to provide a good seal to keep hot ejection gases from leaking past the bond and into the styrofoam. Thus the hole in the motor tube had to be smaller to leave enough surface for the bevels to bond to.

I could go into how I plotted the meridians on the outside of the sphere if you want me to.

 

[JAL3]

I could go into how I plotted the meridians on the outside of the sphere if you want me to.

Yes I would but I'd also like you to go back and take a look at post 12. I think you missed as you were setting forth you beveling method.

 

[MarkII]

Mark, I'm wondering if we're working from the same version of the plan. The one I have shows a thrust ring but no plug at the top of the motor tube. Instead, the top of the tube is cut at a 45. The side tube is also cut at a 45 and the two are joined together that way.

Nope, that's it. As I said, it's been several years since I worked on mine, and memory sometimes plays tricks on me. I must have added the hardwood plug to the design myself, due to the concerns that I stated. But it's funny - all of this time I was sure that it was part of the original design and not a modification by me. I was also sure that the branching connection of the two tubes was also in the original design. It does have them join in almost the same way. By the way, when I worked on this project, Semroc hadn't begun to stock BT-30 yet. I used BT-20 from FlisKits and a spare Estes motor hook for it. A short section of 3/4" dowel was used to block the motor tube at the top, and I drilled a hole through it and embedded a length of Kevlar into it with wood glue. I'm not sure if it shows in any of the pictures, but I did cut the top of the motor tube at an angle.

Although I can easily imagine myself making these mods, that isn't at all how I remember it. Huh...isn't that funny... Hmmmm.

 

[JAL3]

Nope, that's it. As I said, it's been several years since I worked on mine, and memory sometimes plays tricks on me. I must have added the hardwood plug to the design myself, due to the concerns that I stated. But it's funny - all of this time I was sure that it was part of the original design and not a modification by me. I was also sure that the branching connection of the two tubes was also in the original design. It does have them join in almost the same way. By the way, when I worked on this project, Semroc hadn't begun to stock BT-30 yet. I used BT-20 from FlisKits and a spare Estes motor hook for it. A short section of 3/4" dowel was used to block the motor tube at the top, and I drilled a hole through it and embedded a length of Kevlar into it with wood glue. I'm not sure if it shows in any of the pictures, but I did cut the top of the motor tube at an angle.

Although I can easily imagine myself making these mods, that isn't at all how I remember it. Huh...isn't that funny... Hmmmm.

What you say makes perfect sense to me. I just wanted to make sure we were on the same page.

I do have the BT30 and was wondering is a plug would be a good idea even if it doesn't show.

For drawing the circles, I'm thinking about drawing a template in AutoCAD and marking off the quadrants and then just eyeballing it into place. After that some measurements would be made for offsets before the cutting.

My tired brain just can't come up with a better way that isn't so labor intensive that it puts me off the entire project.

I would like to see what you did.

 

[MarkII]

So you could disregard the procedure that I described and just make a simple mitered joint for yours. The angle is not 90°, though, so the miters will have to be something greater than 45°. I'd be interested in finding out how well that type of joint ends up working with this design. It seems to me that something more substantial than the side of the tube needs to be there to protect the foam from the ejection charge, but maybe your experience will prove otherwise.

OK, for the meridians I spliced together a long, narrow strip of cardstock. I drew an absolutely straight line down the middle of it all along the length and I reinforced one end with tape. At that end I also terminated the line with a horizontal line drawn across it at right angles. I punched a very small hole through the paper exactly where the two lines crossed. The masking tape was there to keep the paper from being torn or the hole becoming enlarged from wear.

I started by drawing the longitudinal "prime meridian" and the "north pole." I inserted the motor tube into its bore hole and put a spent motor in it. I pushed a thick pin through the hole in the paper strip and then into the motor's nozzle. Then I wrapped the paper around the ball until it was back over the nozzle. I checked to make sure that the paper was straight and even all around the ball and that the line on it was straight all the way around, and then I punched another hole into the paper on the line right where it overlaid the motor nozzle. I removed the paper, laid it out straight and then doubled it onto itself so that the two holes were over each other, and folded it exactly in half. I punched another hole where the fold line crossed the line on the paper. Then I anchored the paper to the motor again and rewrapped it around the ball. I inserted the tip of a sharpie through the last hole I made and used it to mark the ball. I made another mark on the ball next to it to signify that this was the pole. Then I punched a few more holes in the paper along the line and used a Sharpie to put marks all around the ball along this prime meridian. I used the edge of another strip of paper as a straightedge to draw a line through the marks all the way around the ball.

I bisected the line on the paper with another perpendicular line right at the fold. I anchored it to the motor nozzle again and rotated the paper so that it looked like it was 90° from the first meridian and wrapped the paper around the ball again. I put another pin through the hole at the north pole and pinned it right at the pole. I lined up the cross line at the pole with prime meridian to insure that the paper was indeed rotated 90° from it, and marked the ball for the anti-meridian. I removed the paper and drew that line around the ball.

 

[MarkII]

I folded the paper strip onto itself again so that the anchor hole was lined up with the north pole hole and folded it again. I drew a new line across the center line at this new fold and punched another hole where they crossed. Then I did the same thing on the other half of the strip.

I reinstalled the strip around the ball and over the prime meridian, and made identifiable marks along it where the new holes were placed. Then I rotated the strip to lie over the anti-meridian and did the same thing. I removed the strip and placed it around the ball so that the anchor point was at one of these new marks on the prime meridian, the pole point was directly over the opposite mark on the p.m., and the quarter points were directly over the respective marks on the anti-meridian, and then made marks all round the ball again. I removed the strip and drew in the equator.

The four Moonik-1's antennae/legs will be attached at the points where the meridians cross the equator in such a way that they will be tangent to the ball at those spots. Once I figure out a way to securely anchor them, that is.

I got this far with it in 2006, and then stopped. It has languished in my incomplete projects section ever since. Your thread reminded me of it and now I may actually try to finish it. Back then I had bought a couple of jars of a product called Foam Finish. It is made by Beacon Adhesives. It resembles a very thick paste or white glue and is meant to be applied to styrofoam to give it a hard, sandable and paintable surface. It can also be used to fill in dents and dings in the foam and to bond pieces of foam together. I'm not sure that what I have is still usable or if I have to get more. I think that you get it at a craft store like Michael's or Joanne's.

 

[mwtoelle]

I may be over-complicating this, but could you cut the ball in half after the holes are drilled? Next, the two tubes could be precisely mitered with the joint properly sealed in one half of the ball. Finally, the two halves of the ball would be glued back together, and the model could be completed as per the instructions. Just a thought.

 

[MarkII]

I may be over-complicating this, but could you cut the ball in half after the holes are drilled? Next, the two tubes could be precisely mitered with the joint properly sealed in one half of the ball. Finally, the two halves of the ball would be glued back together, and the model could be completed as per the instructions. Just a thought.

Cutting the ball perfectly in half would be a challenge, too, especially when all you have are hand tools. And then there's the problem with material loss due to kerf, which can be quite significant with styrofoam. I suppose that a hotwire foam cutter would solve that, but I'm not inclined to run out and buy one just for this one project. Making the tube joint wasn't all that hard, once I finally figured out how to do it effectively.

The bigger challenge now looks like it is going to be figuring out how to get those antennae attached securely.

 

[JAL3]

I gathered the parts for my Moonik over a week ago but finally had a chance to get started after church today. I began with the 6" foam ball.

 

[JAL3]

The instructions said to use a 3/4" wooden dowel to drill the motor mount hole. Instead, I used a 6" piece of BT30. I pressed it where I wanted to begin and rotated it one way and then the other while applying pressure to penetrate the foam.

 

[JAL3]

I continued in this manner until I reached the 4-7/8" mark I had made on the tube.

 

[JAL3]

I managed to keep things pretty straight, at least according to my eyes, and the BT seemed to do a good job of cutting the circle but it did absolutely nothing to remove the material within the circle. To do this, I inserted a paddle bit within the tube and twisted it by hand to break up the foam.

 

[JAL3]

After doing this for a bit, I heard a crack and the remaining column of foam broke off within the BT.

 

[JAL3]

I pushed the foam column out of the tube and examined the ball. It seemed I had drilled a fairly clean, fairly straight hole, just as I wanted.

 

[MarkII]

op:

 

[JAL3]

op:

I have a feeling we're both going to need an industrial can of Pepto Bismol before this one is done. So far, though, its better than I expected.

I am still wrestling with the part of me that just want's to try the side ejection and doesn't want to make an exact science of the spherical geometry (the lazy part) and the part that wants it to be perfect.

Time will tell.

Meanwhile, I think its bedtime even though I got quite a bit further...