SIM Modelers - Post Your Designs

EXPjawa said:

My next installment: Sagittarius Arrow

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*Really* like that one.

Lots of interesting designs here. Good work guys!




I'd call this one Pong! a two stage variant would be Ping! (colors would need to change to green and white with black (or white) trim decals.

neil_w said:

*Really* like that one.

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Thanks Neil. I'd say your designs are anything but simplistic; I really dig what you're doing with ring tails. Some of those should make for great slow flights on long burn motors without getting too high to see.

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That's really cool. What would the spherical parts be made from?

Ping pong balls.

In OR, they're back-to-back ogive transitions. I used trial and error until it looked right; going in I didn't know if it would really work, but it turned out pretty good (certainly good enough to get the point across visually.)

Here's a composite image of the details of the two transitions; ORK file is attached as well.


It's kind of a cute design I think; somewhat like the Diamond Cutter with all diamonds and triangles replaced by semicircles.

EXPjawa said:

I call this Berthasaurapod. Don't ask why, suffice it to say that it amused me.

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Don't sell your naming skills short. The name made two options perfectly obvious: Either a Big Bertha (Berthasaur) with pods, or something really big with a pair of modified Berthasaurs as pods. (Just leave off one of the four fins, or not even that if you put the fins at 45 degrees.) Hmm, I guess that'll be my next post to this thread.

Incidentally, the attachments seem to be broken.

I saw that last night, but at the time, clicking on the link still brought up the image. Now it doesn't. This is Berthasaurapod:




The name, incidentally, was a sort of evolutionary thing. Somewhere along the way when I started designing this (based on a Big Bertha), in my mind, Big Bertha became Berthasaurus. Sort of a pun on "saur" vs "soar" (like with Dyna Soar). At one point it was Berthasaurus Rex. But then I added the SRBs as pods, and the name became saurapod, like a brachiosaurus. Incidentally, my spellcheck still wants to turn that into brontosaurus, despite that term being obsolete. Anyway, now we have Berthasaurapod, which shares the overall length, 4-fin configuration, tube size and nose cone (BNC-60L) with the original Big Bertha design from the '60s, prior to being truncated with the later shorter elliptical nose cone. The fins themselves have less overhang and are more delta-like, and the tube is lengthened to keep the length. The fins are also basswood, though the strakes are balsa. The SRB pods are #7 tube, with cone/nozzle sets from Semroc/eRockets, though I'm sure the design originated with Centuri somewhere... Also, the motor mount is upgraded to 24mm - I was adding a bit of weight with the SRBs, comparatively speaking, so I wasn't going to muck about with 18mm motors. And its rounded out with the boat tail from the Astron Sprint XL kit.

Thus concludes the anatomy of a Berthasaurapod.

neil_w said:

Ping pong balls.

In OR, they're back-to-back ogive transitions. I used trial and error until it looked right; going in I didn't know if it would really work, but it turned out pretty good (certainly good enough to get the point across visually.)

Here's a composite image of the details of the two transitions; ORK file is attached as well.
View attachment 297245

It's kind of a cute design I think; somewhat like the Diamond Cutter with all diamonds and triangles replaced by semicircles.

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So, is the intent to cut ping pong balls, and essentially use them as shrouds over a tube joint, instead of a paper cone or the like? I'd bet that cutting the balls somewhat precisely would become kind of a challenge; I'm thinking that just holding them while cutting will be tricky...

One could drill them. Clamp a piece of scrap onto the table of a drill press, drill a 3/4" or so hole part way through. Then you can set the ball in the depression and hold it in one hand while feeding the drill, with whatever size bit is needed. Just use a fresh, sharp bit and go slow.

As for putting them in OR, it's done now, but elliptical transitions might be easier for future designs. An elliptical nose with the length equal to half the diameter is a hemisphere. Getting the length right relative to both front and back diameters takes only a simple application of Pythagoras.

• For a pin pong ball, diameter at large end = 40 mm
• Let diameter at small end be X (in mm)
• Length (in mm) = sqrt(400 - X²/4)

Here's a ping pong ball stuck on a BT-50 using that formula:

The lighter grey is the elliptical nose cone, and the darker is the elliptical transition.

So, is the intent to cut ping pong balls, and essentially use them as shrouds over a tube joint, instead of a paper cone or the like?

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Pretty much.

Although I've never built with them, ping pong balls have an illustrious history in model rockets. Shrox used them a lot (see this one for the ultimate insanity); Gary Byrum has done it at least once, and LW Bercini's Apparition (one of my favorite designs of all time, to be sure) has a couple in it and he described his cutting method in his build thread.

That said, I wouldn't certainly not look forward to cutting 5 of them for this design, though I think the results would be neat. The design seems incomplete without the balls (words to live by, to be sure ).

jqavins said:

As for putting them in OR, it's done now, but elliptical transitions might be easier for future designs.

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I'm sure I had a reason for using ogive rather than ellipsoid, but I can't imagine what it could have been. I just now played a bit and, for the transitions in that particular design, it seems the difference is visually undetectable, but in the future I would indeed use the ellipsoid.

Ladies and GentlemenThe booster pods are full size Big Berthas minus one fin, and with 29 mm motor mounts. The main section is a triple size Bertha with a 38 mm motor mount. It sims out at about 1100 meters using two G77s and a J300. Of course that's based on a really simplistic design file not really buildable and flyable as is, but on the other hand I don't think RS is dropping the pods correctly, so it should be doing better. (Of course, it would also do better with all the fins removed form the boosters, but that would defeat the conceptual purpose.)

Until I do more work on the elliptical tubed plane, here's the last one from my files worth posting.

This one has only marginal stability with a 20 gram nose weight, and each additional 10 grams makes very little difference, so it's not ready to build either.

jqavins said:

Ladies and Gentlemen

May I present:​

The Mega Bertha!
View attachment 297252View attachment 297253View attachment 297254​

The booster pods are full size Big Berthas minus one fin, and with 29 mm motor mounts. The main section is a triple size Bertha with a 38 mm motor mount. It sims out at about 1100 meters using two G77s and a J300. Of course that's based on a really simplistic design file not really buildable and flyable as is, but on the other hand I don't think RS is dropping the pods correctly, so it should be doing better. (Of course, it would also do better with all the fins removed form the boosters, but that would defeat the conceptual purpose.)

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I dig it! Though I would probably go in the direction of Super Bertha/Mini Bertha for the sake of size practicality... To this point, I still haven't built an actual Big Bertha. I've done upscales, Babies, an upscaled Ranger, and the Berthasaurapod. But no basic Bertha...

Another quirk that I've noticed with Rocksim - unless you specifically use the ring tail or tube fin tools, it doesn't recognize that type of feature (aerodynamically). What I mean is, if you create a similar feature using other methods - like clustering internal tubes spaced radially outward for tube fins - it won't see them the same as actual tube fins. Mostly, it'd be well, fine, use the tube fin tool or whatever. But here's a design I drew up a while back on a whim, which has a square ring tail. I call this (imaginatively, I know) the F-Bomb.


Its loosely inspired by WWII vintage general purpose iron bombs, 3" in diameter and 22" long. Obviously, its sized to use mid-powered motors, primarily in the F-size range. The square ring is made with single-fin pods on the fin tips, at 45 degrees angles. I'm not convinced that the sim reads it correctly, drag-wise. As you can see, the CP is pretty far aft:


But the sim suggests that it'll hit almost 875' on an Estes F15 motor. This rocket is 3", with a square ring with square edges on 1/8" fins. It weighs over a pound. Does it seem to anyone else that that altitude is a bit optimstic? It shows it hitting 2800' on a G80, and seems to favor long delays across the board (which is the real indicator in my mind). I'd think that much drag would slow it down quickly after burn out.

I was gonna save this one for the eventual build thread, but what the hell, here it is. This is my slightly modified version of Gary Byrum's APRO Lander. I have all the parts and will be building it later this year I hope. It will eventually have all manner of decals but I'm not sure what yet, so for now it's kind of bare.

APRO Lander 2:


OR doesn't have much of a clue about what to do with this, I'm planning for some nose weight and relying on base drag as well.

I like it! I missed Gary's previous thread, but it reminds me of a sort of a mash up of Mars Snooper, Mars Lander & Astron Starlight. I think the base drag is strong with this one...

EXPjawa said:

My next installment: Sagittarius Arrow

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I really like the lines on this bad boy!!! Now, if the pods eject and glide down... That would be TOO COOL!!!

K'Tesh said:

I really like the lines on this bad boy!!! Now, if the pods eject and glide down... That would be TOO COOL!!!

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That would be interesting, though not what I'd envisioned. I am toying with adding 24mm mounts to the pods, so that I'd have the option of flying D11-Ps on either side of a 29mm BP motor, or just fly on a composite 29. I'll have to look at the sim and see how that stacks up.

Something else I've been working on:


I call this the Tertiary Inquisitor. I came up with this back in the spring, so its strictly coincidental that Estes' new Expedition kit bears some resemblance. This is larger, has three motors protruding through a boat tail, six fins, plus six of my favorite strakes. Main tube is BT80, necks down to BT60, then the nose and forward bay is BT70. Overall, its 4' long. The split is midship, so the recovery gear is in the BT80 tube. Rocksim tells me that in its perfect world, she'll make the .5 past light speed. Sorry, I mean it'll make about 1400' on three E12 motors. She's fast enough for you, old man...

Nice! Slap some Stickershock on it, and I'm sure you could push it past .95 lightspeed.

Contrary to my previously-stated intention to post only "finished" designs, here's two versions of a design that is half-done and causing me great frustration. I love the top view but I can't figure out what to do with the fins on the bottom, and the resulting side view (which right now looks ugly to me). The 3-pod version solves this, but I'd prefer to solve it in the 2-pod version. In another thread, Screaminhelo did a nice jet-fightery variation on this design, but for my own purposes I'm targeting more of a sci-fi rocket style, and the pods spaced off the main BT are key [BTW I'm still exploring some very differently-styled rockets with those pods, but that's a separate topic. ]

If anyone has ideas on how to finish this one, have at it.

2-pod version:
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3-pod version:
View attachment newtube2.ork

I guess I don't see the problem. Personally, I like the look of the 2-pod version better, as you've got them rendered. It strikes me as a little less derivative of a "normal" rocket.

If it were me, I'd consider eliminating the ventral fin, and instead give the "wing" fins a 15-20 degree anhedral, similar to the Orbital Interceptor or NASA Pegasus designs. You could possibly angle them down from the pod out, so that the pod tubes are still in the 9 & 3 o'clock positions. Or maybe angle them down from the root and place the pod tubes on the upper surface of the wing at the root.

EXPjawa said:

If it were me, I'd consider eliminating the ventral fin, and instead give the "wing" fins a 15-20 degree anhedral, similar to the Orbital Interceptor or NASA Pegasus designs. You could possibly angle them down from the pod out, so that the pod tubes are still in the 9 & 3 o'clock positions.

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As rendered they have a 15 degree anhedral (just learned a new word, yay ) although the pods and wings are at the same angle because OR can't do it any other way. Getting rid of the ventral is possible, though that would enhance my general worries about stability... maybe the ring is enough down there, dunno.

You don't need 3 evenly spaced fins for stability. The two former kits I just sited are examples of that. Just a bit of down angle on the side fins will suffice in combination with a dorsal fin. In your case, the ring at the tail pretty much eliminates the need for any other fins, so everything else is dressing. I think your design as you have it would be fine if you simply dropped the ventral fin, though you could retain a small strut fin to support the ring if you think it necessary.

Good thoughts, thanks. Maybe I'll just ditch the ventral fin and move on from there.

No problem, that's sort of what I started this thread for.

On another note, I've started playing with the "texture" tool in Rocksim. I still think that the rendering abilities of Open Rocket seem better, but this at least adds another dimension of finishing. This is not my rocket design, but rather what I'm thinking about doing with MAC Performance Scorpion that I just picked up:



For the nose cone and (green) fins, I used an image of the Ford paint color "Gotta Have it Green", with was a color on the 2013 Mustang Boss 302. The main tube used a sample picture of metallic silver paint, and for the roll pattern I simply found a jpg of black stripes that's applied onto a massless/dummy tube section. I'm sure that there's a lot more that can be done with some experimentation, though I don't see how to apply decal like textures unless I specifically created image files containing the decal artwork for each specific component. Is that how you're doing it in OR?

That sounds pretty similar. Gory details about OR decaling are documented in another thread. One of the things I find challenging about metallic textures like you've got there is that the resolution of the "grain" varies depending on the size of the component and the size of the image. So I try to control that as closely as I can. In your picture there, the silver definitely looks like metallic silver but the grain is coarse; I'd try to start with a larger image of the silver if you can find one, and then when it is scaled to the BT the grain will look smaller. (Actually I really like the sparkly appearance you have there, but I suspect that the real paint would have much finer grain, unless you go with a metal flake-type paint). But then it all depends on how much realism you're aiming for.

Typically I do not create dummy components just for decals (if I understand correctly what you're doing); I create a single decal image that covers the entire component, however complex it may be. In your case, it would have green and black stripes and the black band up top, and silver on bottom. But any method is OK if it looks like you want and doesn't mess up the simulation (too much ).

So I just spent a little while trying to enter a variant of my design in Rocksim; really needed the pods implementation to be able to show it correctly. After battling the UI (oh my) and mostly figuring out how to do it, I was just entering the last fin when it crashed and lost all my data.

Guess I'll stick with OR and hope they come out with a decent pods implementation at some point.

RockSim is like anything else: save often. I've had a few crashes like that over the years, but not many. I've had the same in MS Office apps too, amd games, and Libre Office, and plenty of other things.

Here is my contribution. I call it Helios. It has only flown once; on a G76-7G. Hasn't been painted yet.


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[video=youtube;n_34MELEhG8]https://www.youtube.com/watch?v=n_34MELEhG8[/video]