Diamond Cutter: A weird design concept I'm screwing around with

For some reason I'm intrigued with the idea of shaping and mounting fins in conjunction with transition areas in the BT. Here's a first experiment with that idea which I'm calling the Diamond Cutter. Open Rocket file is attached, but it's totally unrealistic, just there to get a visualization.

This would be a bit challenging but not impossible to build. It has a hint of Black Star Voyager in it, but that wasn't my inspiration.

I have some other related ideas I'm thinking about, but this is the first one that totally came together for me (although it is still in the early stages). The color scheme is mainly intended to highlight the interesting bits.

Anyway, just curious if anyone finds this concept even remotely interesting. All comments welcome.



View attachment diamond_cutter.ork

It looks cool to me.

Looks good to me too. Unique but not weird.

I love it! Really cool design idea.

Great idea. Transitions would be interesting given that they are in the same areas as a motor mount. This does have a little Flis feel to it too, as he likes to change things up in the fin/mount area like this too.

RocketGeekInFL said:

Great idea. Transitions would be interesting given that they are in the same areas as a motor mount.

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I figured the motor mount tube would run through the middle, and mount with centering rings to the tubes fore and aft of the transitions. The tube would have to be extra-long, but that shouldn't be a problem. The transitions would presumably have to be done with shrouds, which I'm not too enthusiastic about but probably would have no choice (barring access to a 3D printer and someone to help me out with that).

The front transitions are trickier given the need to mount the canards there. Maybe two balsa transitions cut and glued back-to-back, which would make a nice gluing surface for the fins. There are some other more exotic options too.

Now who's gonna help me with some 3D printing...

rstaff3 said:

Looks good to me too. Unique but not weird.

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This pretty much sums up my thoughts on it.

I like the design and the name fits it well!

Thanks for the positive feedback.

I think deep down I was hoping for some more negative feedback to discourage me from going forward with this. Perhaps this will be a good winter project for me.

If anyone has any inspired ideas for how to build the two transition areas I'm all ears. I have a bunch of ideas but am not totally happy with any of them yet.

Paint scheme/design input is also welcome. I'm kind of liking what I have there but I feel like it needs some more details (and, eventually, a logo).

I couldn't do it but with an airbrush, you could probably paint fake facets on the fins. Cardstock transitions probably would work. The lower ones are well protected and you could backfill the top ones with foam to better support the fins.

Looks cool. As others have said, looks different, which is getting harder to achieve IMHO. Looking forward to hearing how you solve the transition question.

At the rear, it looks like you could have a custom turned transition from balsa if you used an 18mm MMT. Maybe Roachwerks could supply them? Undrilled for the front, drilled for the rear

24mm would be trickier - I would think that would need to be card stock or 3d printing, as you suggested. Or what about a balsa transition , drilled for a 24mm mmt, then a tapered duct/tube for the ejection gasses?

Really cool design! If you 3D print the transition to have the couplers on the ends and motor mount diameter on the inside it could be one unit and the forward fin set coul act as the bulkhead. You could even turn the transition pieces on a lathe from balsa rather than 3D printing.

I don't have OR to open the file right now, what size body tube are you using?

I actually just did something very similar to this with the rear end of a rocket. Just stretched out a bit. I used cardstock transitions, and an extra long motor mount. I used four centering rings, two above and two below the transition region, to attach the body tubes to the MM. I'm going to get a build thread up eventually, but here's a pic of what it looked like when complete.

Overall, I think it came out pretty well, but I did find that the cardstock transitions tended to bulge a bit at the junction. It took some careful sanding at that point (and more after primer) to get it mostly flat. I'd suggest in the future, using a two layer transition, with seams at different locations, so that the outer surface seam is glued down to the inner surface for added strength. I've done it that way before, but was trying to speed up the process for this one. My mistake. I'll leave the fin work in that area up to you, but I think that if you used this method and stretched the motor mount far enough, you could make it work. I may have to do something like that in the future. I like the idea.

FYI, this flew well on a C6-3, but weather-cocked a bit due to length.

75Grandville said:

At the rear, it looks like you could have a custom turned transition from balsa if you used an 18mm MMT. Maybe Roachwerks could supply them? Undrilled for the front, drilled for the rear

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Ooh, I didn't know about them, it looks like they could certainly do it, at least for the front.

24mm would be trickier - I would think that would need to be card stock or 3d printing, as you suggested. Or what about a balsa transition , drilled for a 24mm mmt, then a tapered duct/tube for the ejection gasses?

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Not sure I understand the last part?

Danh said:

If you 3D print the transition to have the couplers on the ends and motor mount diameter on the inside it could be one unit and the forward fin set could act as the bulkhead.

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The forward transition is gonna be a bulkhead no matter what, so I can use the top section for payload. I had sort of thought that a fairly standard (but elongated) motor mount would run through the center of the rear transition, just need to provide the shape on the outside.

I don't have OR to open the file right now, what size body tube are you using?

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At the moment it's BT60, which is probably my preference, with a 24 mm motor mount, but it could also work with a BT55 and an 18 mm motor (which would allow for a deeper transition area, relatively speaking).

Well, this all certainly went from "toying around with an idea" to "planning a build" a little faster than I was expecting.

MCriscione said:

I actually just did something very similar to this with the rear end of a rocket. Just stretched out a bit.

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Whoa, that is unbelievably similar to my original idea, with the strakes (if we can call them that) mounted "into" a narrower section of tube. I also thought of bulging them out a bit, and that eventually evolved into the design we're discussing here. Looks great, do you have any pictures of it all painted?

I used cardstock transitions, and an extra long motor mount. I used four centering rings, two above and two below the transition region, to attach the body tubes to the MM. I'm going to get a build thread up eventually, but here's a pic of what it looked like when complete.

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That is exactly what I was thinking. Cool.

I'm thinking I should perhaps experiment with making some cardstock shrouds (or super-shrouds as hcmbanjo excellently described in an Apogee newsletter). I can do this on its own before investing in any of the other parts. If I can't get them to come out OK, I can try something different.

Ooh, and I just had a good idea how to build the front transition and attach the fins. Will draw it out in a future post.

It flew in sanded primer on 9/26, but I haven't gone back and painted it. It needs a second primer coat, and by then, who knows, it may well be too cold to paint around my parts.

The 'super-shroud' you referenced is exactly what I meant. I only read over the newsletter quickly but it looks like he made his examples with overlapping glue tabs. For the outer layer though, you don't need a tab, you can just glue it directly to the first one if your careful. Also, it may not be obvious, but I used slightly thicker centering rings adjacent to the transitions, that allowed enough surface area to attach both the BT and the transition. I slid the transitions on the MM, slid on the CRs and positioned and glued them down, then slid on the BTs and glued them such that the CRs adjacent to the transitions were still half exposed, then slid the transitions up and glued them to the CRs too. You might have to reverse that a bit if you don't have any gap like I did, but you shouldn't have too much trouble. You could always double up CRs there to make it extra wide. Check out https://www.delorie.com/rockets/transitions.html for transition templates. I like their generator the best of what I've seen so far.

neil_w said:

Not sure I understand the last part?

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What I was thinking was: If you wanted to use a 24mm motor, then drill the transition for an 18mm (or some other diameter that could have a tube added for stability). Then, drill the bottom end to fit over the 24mm motor mount. That way, there would be a 18mm hole coming from the top, and meeting a 24mm hole coming from the bottom. That would give clearance for a 24mm motor, and still provide a path for the ejection charge. You'd probably want to taper the edges of the 24mm hole to direct the ejection charge through the smaller 18mm tube/hole.


I am now reminded of the Red River Rocketry Red Star (OOP) which uses paper transitions, and fits the fins into the lower transitions: https://www.rocketreviews.com/redstar---red-river-rocketry.html

Awesome. I love the idea of the extra-thick CR, am definitely gonna do that. I will look forward to your build thread. Have you named the rocket yet BTW? I was thinking of something related to "Skeleton" when I was considering that sort of design.

Gotta go start practicing shroud-building. I can make a hundred until I get satisfactory results, then I'll start collecting the rest of the parts.

I guess this rocket is a "go", although I expect design details to change. I'll do a build thread eventually.

[in reply to 75Grandville]

Ah, now I get it. I think that could definitely work. For now I'm leaning toward some straightforward shroud work, but I'll keep that idea in mind for the future.

Yes, that Redstar does play with the same idea a bit. I don't know why I'm so fascinated by it, but it least it's an interesting enough wrinkle to give me an excuse to do my first scratch build.

Here is a couple ideas If you wanted to 3d print them . 24mm motor mount tube runs through booster , slots on forward fins for ttw mounting.

Danh said:

Here is a couple ideas If you wanted to 3d print them . 24mm motor mount tube runs through booster , slots on forward fins for ttw mounting.

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Dang, that is *so* tempting... but I think I'm going to try traditional construction (with shrouds and balsa) first, and see how it goes. Suddenly I'm enthusiastic about the idea of seeing how good of a shroud I can make.

Now, when I revisit this concept in the future and start to experiment with curved transitions (i.e, smooth curved indentations), that'll be a different story. I think those could look really cool (with curved fins to match...)

Gordon at Roachwerks gave me a cheaper-than-expected estimate to fabricate the transitions out of balsa: on solid piece for the front and two pieces (drilled for MM) in the rear. I think it's a no-brainer for the front, and there's a good chance I'm going to go for it for the rear as well. So much for my shrouds. Maybe I'll add a small shroud to the rear.

With the one-piece front transition, I'll be able to mount the fins into it and paint the whole assembly before attaching it to the payload section in front, which should save me some masking. Actually I could attach the two rear pieces (to each other) and paint them separately as well. That's very appealing.

Here's a "final" OpenRocket file for this rocket, ready enough to build from. I tweaked a few things, but mostly the same as before. I will be going with custom balsa parts from Roachwerks for the transition pieces. Build thread to come.

Still open for paint scheme suggestions if anyone has any. Current design is showing the fins as grey, but that's supposed to be silver. Body is either black or black metallic, haven't decided yet. No clue for decals or other highlights at this point.

View attachment diamond_cutter_real.ork

one can use a piece of rod about 5/16" diameter(an x-acto knife works) and a mouse pad to curve cardstock. put the cardstock on the pad then press down on the rod as you roll it across the paper and you will get a curl in the paper.
Rex

Given what I need to do with the back-to-back transitions here, I'm gonna wimp out and use the balsa. My shroud-making adventure will have to wait for a future build.

Anyone have an opinion between these two versions? I think I have a preference (and a definite reason) but I've now stared at them long enough to be questioning my own judgment (and sanity).

Opinions - on teh interwebs? Yer lookin in the wrong place...


I prefer the top version, which I believe was your original. The fins and cutouts just look better to me.


But, if you have a preference, go with yours. It's your rocket, you're flying it. Since I doubt it impacts stability, do what makes you happy!

neil_w said:

Anyone have an opinion between these two versions? I think I have a preference (and a definite reason) but I've now stared at them long enough to be questioning my own judgment (and sanity).View attachment 274144

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I like the bottom one with the larger gap in the fin area.

I like the symmetry of the bottom one better.

neil_w said:

Anyone have an opinion between these two versions? I think I have a preference (and a definite reason) but I've now stared at them long enough to be questioning my own judgment (and sanity).

Click to expand...

For purely aerodynamic reasons, I think the second (lower) configuration might be a teeny bit better.

The "reduction" transition angle is more shallow on the second config, and the airflow should be better able to make it over the corner with the smaller angle and stay attached. (Separated airflow adds turbulence and drag.) Even better yet would be if that corner could be rounded just a little bit, as subsonic airflow adheres more easily to curves than to sharp corners. Same thing applies to rounding the outer (aft) edge of the transition that follows immediately behind. (If that does not ruin the style you are going for.) FWIW.

Better airflow quality would also make your fins more effective, in addition to reducing drag.

Cool design. Keep on using your imagination, say no to boring.